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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
4 *
5 * Swap reorganised 29.12.95, Stephen Tweedie.
6 * kswapd added: 7.1.96 sct
7 * Removed kswapd_ctl limits, and swap out as many pages as needed
8 * to bring the system back to freepages.high: 2.4.97, Rik van Riel.
9 * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
10 * Multiqueue VM started 5.8.00, Rik van Riel.
11 */
12
13#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
14
15#include <linux/mm.h>
16#include <linux/sched/mm.h>
17#include <linux/module.h>
18#include <linux/gfp.h>
19#include <linux/kernel_stat.h>
20#include <linux/swap.h>
21#include <linux/pagemap.h>
22#include <linux/init.h>
23#include <linux/highmem.h>
24#include <linux/vmpressure.h>
25#include <linux/vmstat.h>
26#include <linux/file.h>
27#include <linux/writeback.h>
28#include <linux/blkdev.h>
29#include <linux/buffer_head.h> /* for buffer_heads_over_limit */
30#include <linux/mm_inline.h>
31#include <linux/backing-dev.h>
32#include <linux/rmap.h>
33#include <linux/topology.h>
34#include <linux/cpu.h>
35#include <linux/cpuset.h>
36#include <linux/compaction.h>
37#include <linux/notifier.h>
38#include <linux/delay.h>
39#include <linux/kthread.h>
40#include <linux/freezer.h>
41#include <linux/memcontrol.h>
42#include <linux/migrate.h>
43#include <linux/delayacct.h>
44#include <linux/sysctl.h>
45#include <linux/memory-tiers.h>
46#include <linux/oom.h>
47#include <linux/pagevec.h>
48#include <linux/prefetch.h>
49#include <linux/printk.h>
50#include <linux/dax.h>
51#include <linux/psi.h>
52#include <linux/pagewalk.h>
53#include <linux/shmem_fs.h>
54#include <linux/ctype.h>
55#include <linux/debugfs.h>
56#include <linux/khugepaged.h>
57#include <linux/rculist_nulls.h>
58#include <linux/random.h>
59
60#include <asm/tlbflush.h>
61#include <asm/div64.h>
62
63#include <linux/swapops.h>
64#include <linux/balloon_compaction.h>
65#include <linux/sched/sysctl.h>
66
67#include "internal.h"
68#include "swap.h"
69
70#define CREATE_TRACE_POINTS
71#include <trace/events/vmscan.h>
72
73struct scan_control {
74 /* How many pages shrink_list() should reclaim */
75 unsigned long nr_to_reclaim;
76
77 /*
78 * Nodemask of nodes allowed by the caller. If NULL, all nodes
79 * are scanned.
80 */
81 nodemask_t *nodemask;
82
83 /*
84 * The memory cgroup that hit its limit and as a result is the
85 * primary target of this reclaim invocation.
86 */
87 struct mem_cgroup *target_mem_cgroup;
88
89 /*
90 * Scan pressure balancing between anon and file LRUs
91 */
92 unsigned long anon_cost;
93 unsigned long file_cost;
94
95 /* Can active folios be deactivated as part of reclaim? */
96#define DEACTIVATE_ANON 1
97#define DEACTIVATE_FILE 2
98 unsigned int may_deactivate:2;
99 unsigned int force_deactivate:1;
100 unsigned int skipped_deactivate:1;
101
102 /* Writepage batching in laptop mode; RECLAIM_WRITE */
103 unsigned int may_writepage:1;
104
105 /* Can mapped folios be reclaimed? */
106 unsigned int may_unmap:1;
107
108 /* Can folios be swapped as part of reclaim? */
109 unsigned int may_swap:1;
110
111 /* Proactive reclaim invoked by userspace through memory.reclaim */
112 unsigned int proactive:1;
113
114 /*
115 * Cgroup memory below memory.low is protected as long as we
116 * don't threaten to OOM. If any cgroup is reclaimed at
117 * reduced force or passed over entirely due to its memory.low
118 * setting (memcg_low_skipped), and nothing is reclaimed as a
119 * result, then go back for one more cycle that reclaims the protected
120 * memory (memcg_low_reclaim) to avert OOM.
121 */
122 unsigned int memcg_low_reclaim:1;
123 unsigned int memcg_low_skipped:1;
124
125 unsigned int hibernation_mode:1;
126
127 /* One of the zones is ready for compaction */
128 unsigned int compaction_ready:1;
129
130 /* There is easily reclaimable cold cache in the current node */
131 unsigned int cache_trim_mode:1;
132
133 /* The file folios on the current node are dangerously low */
134 unsigned int file_is_tiny:1;
135
136 /* Always discard instead of demoting to lower tier memory */
137 unsigned int no_demotion:1;
138
139 /* Allocation order */
140 s8 order;
141
142 /* Scan (total_size >> priority) pages at once */
143 s8 priority;
144
145 /* The highest zone to isolate folios for reclaim from */
146 s8 reclaim_idx;
147
148 /* This context's GFP mask */
149 gfp_t gfp_mask;
150
151 /* Incremented by the number of inactive pages that were scanned */
152 unsigned long nr_scanned;
153
154 /* Number of pages freed so far during a call to shrink_zones() */
155 unsigned long nr_reclaimed;
156
157 struct {
158 unsigned int dirty;
159 unsigned int unqueued_dirty;
160 unsigned int congested;
161 unsigned int writeback;
162 unsigned int immediate;
163 unsigned int file_taken;
164 unsigned int taken;
165 } nr;
166
167 /* for recording the reclaimed slab by now */
168 struct reclaim_state reclaim_state;
169};
170
171#ifdef ARCH_HAS_PREFETCHW
172#define prefetchw_prev_lru_folio(_folio, _base, _field) \
173 do { \
174 if ((_folio)->lru.prev != _base) { \
175 struct folio *prev; \
176 \
177 prev = lru_to_folio(&(_folio->lru)); \
178 prefetchw(&prev->_field); \
179 } \
180 } while (0)
181#else
182#define prefetchw_prev_lru_folio(_folio, _base, _field) do { } while (0)
183#endif
184
185/*
186 * From 0 .. 200. Higher means more swappy.
187 */
188int vm_swappiness = 60;
189
190#ifdef CONFIG_MEMCG
191
192/* Returns true for reclaim through cgroup limits or cgroup interfaces. */
193static bool cgroup_reclaim(struct scan_control *sc)
194{
195 return sc->target_mem_cgroup;
196}
197
198/*
199 * Returns true for reclaim on the root cgroup. This is true for direct
200 * allocator reclaim and reclaim through cgroup interfaces on the root cgroup.
201 */
202static bool root_reclaim(struct scan_control *sc)
203{
204 return !sc->target_mem_cgroup || mem_cgroup_is_root(sc->target_mem_cgroup);
205}
206
207/**
208 * writeback_throttling_sane - is the usual dirty throttling mechanism available?
209 * @sc: scan_control in question
210 *
211 * The normal page dirty throttling mechanism in balance_dirty_pages() is
212 * completely broken with the legacy memcg and direct stalling in
213 * shrink_folio_list() is used for throttling instead, which lacks all the
214 * niceties such as fairness, adaptive pausing, bandwidth proportional
215 * allocation and configurability.
216 *
217 * This function tests whether the vmscan currently in progress can assume
218 * that the normal dirty throttling mechanism is operational.
219 */
220static bool writeback_throttling_sane(struct scan_control *sc)
221{
222 if (!cgroup_reclaim(sc))
223 return true;
224#ifdef CONFIG_CGROUP_WRITEBACK
225 if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
226 return true;
227#endif
228 return false;
229}
230#else
231static bool cgroup_reclaim(struct scan_control *sc)
232{
233 return false;
234}
235
236static bool root_reclaim(struct scan_control *sc)
237{
238 return true;
239}
240
241static bool writeback_throttling_sane(struct scan_control *sc)
242{
243 return true;
244}
245#endif
246
247static void set_task_reclaim_state(struct task_struct *task,
248 struct reclaim_state *rs)
249{
250 /* Check for an overwrite */
251 WARN_ON_ONCE(rs && task->reclaim_state);
252
253 /* Check for the nulling of an already-nulled member */
254 WARN_ON_ONCE(!rs && !task->reclaim_state);
255
256 task->reclaim_state = rs;
257}
258
259/*
260 * flush_reclaim_state(): add pages reclaimed outside of LRU-based reclaim to
261 * scan_control->nr_reclaimed.
262 */
263static void flush_reclaim_state(struct scan_control *sc)
264{
265 /*
266 * Currently, reclaim_state->reclaimed includes three types of pages
267 * freed outside of vmscan:
268 * (1) Slab pages.
269 * (2) Clean file pages from pruned inodes (on highmem systems).
270 * (3) XFS freed buffer pages.
271 *
272 * For all of these cases, we cannot universally link the pages to a
273 * single memcg. For example, a memcg-aware shrinker can free one object
274 * charged to the target memcg, causing an entire page to be freed.
275 * If we count the entire page as reclaimed from the memcg, we end up
276 * overestimating the reclaimed amount (potentially under-reclaiming).
277 *
278 * Only count such pages for global reclaim to prevent under-reclaiming
279 * from the target memcg; preventing unnecessary retries during memcg
280 * charging and false positives from proactive reclaim.
281 *
282 * For uncommon cases where the freed pages were actually mostly
283 * charged to the target memcg, we end up underestimating the reclaimed
284 * amount. This should be fine. The freed pages will be uncharged
285 * anyway, even if they are not counted here properly, and we will be
286 * able to make forward progress in charging (which is usually in a
287 * retry loop).
288 *
289 * We can go one step further, and report the uncharged objcg pages in
290 * memcg reclaim, to make reporting more accurate and reduce
291 * underestimation, but it's probably not worth the complexity for now.
292 */
293 if (current->reclaim_state && root_reclaim(sc)) {
294 sc->nr_reclaimed += current->reclaim_state->reclaimed;
295 current->reclaim_state->reclaimed = 0;
296 }
297}
298
299static bool can_demote(int nid, struct scan_control *sc)
300{
301 if (!numa_demotion_enabled)
302 return false;
303 if (sc && sc->no_demotion)
304 return false;
305 if (next_demotion_node(nid) == NUMA_NO_NODE)
306 return false;
307
308 return true;
309}
310
311static inline bool can_reclaim_anon_pages(struct mem_cgroup *memcg,
312 int nid,
313 struct scan_control *sc)
314{
315 if (memcg == NULL) {
316 /*
317 * For non-memcg reclaim, is there
318 * space in any swap device?
319 */
320 if (get_nr_swap_pages() > 0)
321 return true;
322 } else {
323 /* Is the memcg below its swap limit? */
324 if (mem_cgroup_get_nr_swap_pages(memcg) > 0)
325 return true;
326 }
327
328 /*
329 * The page can not be swapped.
330 *
331 * Can it be reclaimed from this node via demotion?
332 */
333 return can_demote(nid, sc);
334}
335
336/*
337 * This misses isolated folios which are not accounted for to save counters.
338 * As the data only determines if reclaim or compaction continues, it is
339 * not expected that isolated folios will be a dominating factor.
340 */
341unsigned long zone_reclaimable_pages(struct zone *zone)
342{
343 unsigned long nr;
344
345 nr = zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_FILE) +
346 zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_FILE);
347 if (can_reclaim_anon_pages(NULL, zone_to_nid(zone), NULL))
348 nr += zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_ANON) +
349 zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_ANON);
350
351 return nr;
352}
353
354/**
355 * lruvec_lru_size - Returns the number of pages on the given LRU list.
356 * @lruvec: lru vector
357 * @lru: lru to use
358 * @zone_idx: zones to consider (use MAX_NR_ZONES - 1 for the whole LRU list)
359 */
360static unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru,
361 int zone_idx)
362{
363 unsigned long size = 0;
364 int zid;
365
366 for (zid = 0; zid <= zone_idx; zid++) {
367 struct zone *zone = &lruvec_pgdat(lruvec)->node_zones[zid];
368
369 if (!managed_zone(zone))
370 continue;
371
372 if (!mem_cgroup_disabled())
373 size += mem_cgroup_get_zone_lru_size(lruvec, lru, zid);
374 else
375 size += zone_page_state(zone, NR_ZONE_LRU_BASE + lru);
376 }
377 return size;
378}
379
380static unsigned long drop_slab_node(int nid)
381{
382 unsigned long freed = 0;
383 struct mem_cgroup *memcg = NULL;
384
385 memcg = mem_cgroup_iter(NULL, NULL, NULL);
386 do {
387 freed += shrink_slab(GFP_KERNEL, nid, memcg, 0);
388 } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
389
390 return freed;
391}
392
393void drop_slab(void)
394{
395 int nid;
396 int shift = 0;
397 unsigned long freed;
398
399 do {
400 freed = 0;
401 for_each_online_node(nid) {
402 if (fatal_signal_pending(current))
403 return;
404
405 freed += drop_slab_node(nid);
406 }
407 } while ((freed >> shift++) > 1);
408}
409
410static int reclaimer_offset(void)
411{
412 BUILD_BUG_ON(PGSTEAL_DIRECT - PGSTEAL_KSWAPD !=
413 PGDEMOTE_DIRECT - PGDEMOTE_KSWAPD);
414 BUILD_BUG_ON(PGSTEAL_KHUGEPAGED - PGSTEAL_KSWAPD !=
415 PGDEMOTE_KHUGEPAGED - PGDEMOTE_KSWAPD);
416 BUILD_BUG_ON(PGSTEAL_DIRECT - PGSTEAL_KSWAPD !=
417 PGSCAN_DIRECT - PGSCAN_KSWAPD);
418 BUILD_BUG_ON(PGSTEAL_KHUGEPAGED - PGSTEAL_KSWAPD !=
419 PGSCAN_KHUGEPAGED - PGSCAN_KSWAPD);
420
421 if (current_is_kswapd())
422 return 0;
423 if (current_is_khugepaged())
424 return PGSTEAL_KHUGEPAGED - PGSTEAL_KSWAPD;
425 return PGSTEAL_DIRECT - PGSTEAL_KSWAPD;
426}
427
428static inline int is_page_cache_freeable(struct folio *folio)
429{
430 /*
431 * A freeable page cache folio is referenced only by the caller
432 * that isolated the folio, the page cache and optional filesystem
433 * private data at folio->private.
434 */
435 return folio_ref_count(folio) - folio_test_private(folio) ==
436 1 + folio_nr_pages(folio);
437}
438
439/*
440 * We detected a synchronous write error writing a folio out. Probably
441 * -ENOSPC. We need to propagate that into the address_space for a subsequent
442 * fsync(), msync() or close().
443 *
444 * The tricky part is that after writepage we cannot touch the mapping: nothing
445 * prevents it from being freed up. But we have a ref on the folio and once
446 * that folio is locked, the mapping is pinned.
447 *
448 * We're allowed to run sleeping folio_lock() here because we know the caller has
449 * __GFP_FS.
450 */
451static void handle_write_error(struct address_space *mapping,
452 struct folio *folio, int error)
453{
454 folio_lock(folio);
455 if (folio_mapping(folio) == mapping)
456 mapping_set_error(mapping, error);
457 folio_unlock(folio);
458}
459
460static bool skip_throttle_noprogress(pg_data_t *pgdat)
461{
462 int reclaimable = 0, write_pending = 0;
463 int i;
464
465 /*
466 * If kswapd is disabled, reschedule if necessary but do not
467 * throttle as the system is likely near OOM.
468 */
469 if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES)
470 return true;
471
472 /*
473 * If there are a lot of dirty/writeback folios then do not
474 * throttle as throttling will occur when the folios cycle
475 * towards the end of the LRU if still under writeback.
476 */
477 for (i = 0; i < MAX_NR_ZONES; i++) {
478 struct zone *zone = pgdat->node_zones + i;
479
480 if (!managed_zone(zone))
481 continue;
482
483 reclaimable += zone_reclaimable_pages(zone);
484 write_pending += zone_page_state_snapshot(zone,
485 NR_ZONE_WRITE_PENDING);
486 }
487 if (2 * write_pending <= reclaimable)
488 return true;
489
490 return false;
491}
492
493void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason)
494{
495 wait_queue_head_t *wqh = &pgdat->reclaim_wait[reason];
496 long timeout, ret;
497 DEFINE_WAIT(wait);
498
499 /*
500 * Do not throttle user workers, kthreads other than kswapd or
501 * workqueues. They may be required for reclaim to make
502 * forward progress (e.g. journalling workqueues or kthreads).
503 */
504 if (!current_is_kswapd() &&
505 current->flags & (PF_USER_WORKER|PF_KTHREAD)) {
506 cond_resched();
507 return;
508 }
509
510 /*
511 * These figures are pulled out of thin air.
512 * VMSCAN_THROTTLE_ISOLATED is a transient condition based on too many
513 * parallel reclaimers which is a short-lived event so the timeout is
514 * short. Failing to make progress or waiting on writeback are
515 * potentially long-lived events so use a longer timeout. This is shaky
516 * logic as a failure to make progress could be due to anything from
517 * writeback to a slow device to excessive referenced folios at the tail
518 * of the inactive LRU.
519 */
520 switch(reason) {
521 case VMSCAN_THROTTLE_WRITEBACK:
522 timeout = HZ/10;
523
524 if (atomic_inc_return(&pgdat->nr_writeback_throttled) == 1) {
525 WRITE_ONCE(pgdat->nr_reclaim_start,
526 node_page_state(pgdat, NR_THROTTLED_WRITTEN));
527 }
528
529 break;
530 case VMSCAN_THROTTLE_CONGESTED:
531 fallthrough;
532 case VMSCAN_THROTTLE_NOPROGRESS:
533 if (skip_throttle_noprogress(pgdat)) {
534 cond_resched();
535 return;
536 }
537
538 timeout = 1;
539
540 break;
541 case VMSCAN_THROTTLE_ISOLATED:
542 timeout = HZ/50;
543 break;
544 default:
545 WARN_ON_ONCE(1);
546 timeout = HZ;
547 break;
548 }
549
550 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
551 ret = schedule_timeout(timeout);
552 finish_wait(wqh, &wait);
553
554 if (reason == VMSCAN_THROTTLE_WRITEBACK)
555 atomic_dec(&pgdat->nr_writeback_throttled);
556
557 trace_mm_vmscan_throttled(pgdat->node_id, jiffies_to_usecs(timeout),
558 jiffies_to_usecs(timeout - ret),
559 reason);
560}
561
562/*
563 * Account for folios written if tasks are throttled waiting on dirty
564 * folios to clean. If enough folios have been cleaned since throttling
565 * started then wakeup the throttled tasks.
566 */
567void __acct_reclaim_writeback(pg_data_t *pgdat, struct folio *folio,
568 int nr_throttled)
569{
570 unsigned long nr_written;
571
572 node_stat_add_folio(folio, NR_THROTTLED_WRITTEN);
573
574 /*
575 * This is an inaccurate read as the per-cpu deltas may not
576 * be synchronised. However, given that the system is
577 * writeback throttled, it is not worth taking the penalty
578 * of getting an accurate count. At worst, the throttle
579 * timeout guarantees forward progress.
580 */
581 nr_written = node_page_state(pgdat, NR_THROTTLED_WRITTEN) -
582 READ_ONCE(pgdat->nr_reclaim_start);
583
584 if (nr_written > SWAP_CLUSTER_MAX * nr_throttled)
585 wake_up(&pgdat->reclaim_wait[VMSCAN_THROTTLE_WRITEBACK]);
586}
587
588/* possible outcome of pageout() */
589typedef enum {
590 /* failed to write folio out, folio is locked */
591 PAGE_KEEP,
592 /* move folio to the active list, folio is locked */
593 PAGE_ACTIVATE,
594 /* folio has been sent to the disk successfully, folio is unlocked */
595 PAGE_SUCCESS,
596 /* folio is clean and locked */
597 PAGE_CLEAN,
598} pageout_t;
599
600/*
601 * pageout is called by shrink_folio_list() for each dirty folio.
602 * Calls ->writepage().
603 */
604static pageout_t pageout(struct folio *folio, struct address_space *mapping,
605 struct swap_iocb **plug)
606{
607 /*
608 * If the folio is dirty, only perform writeback if that write
609 * will be non-blocking. To prevent this allocation from being
610 * stalled by pagecache activity. But note that there may be
611 * stalls if we need to run get_block(). We could test
612 * PagePrivate for that.
613 *
614 * If this process is currently in __generic_file_write_iter() against
615 * this folio's queue, we can perform writeback even if that
616 * will block.
617 *
618 * If the folio is swapcache, write it back even if that would
619 * block, for some throttling. This happens by accident, because
620 * swap_backing_dev_info is bust: it doesn't reflect the
621 * congestion state of the swapdevs. Easy to fix, if needed.
622 */
623 if (!is_page_cache_freeable(folio))
624 return PAGE_KEEP;
625 if (!mapping) {
626 /*
627 * Some data journaling orphaned folios can have
628 * folio->mapping == NULL while being dirty with clean buffers.
629 */
630 if (folio_test_private(folio)) {
631 if (try_to_free_buffers(folio)) {
632 folio_clear_dirty(folio);
633 pr_info("%s: orphaned folio\n", __func__);
634 return PAGE_CLEAN;
635 }
636 }
637 return PAGE_KEEP;
638 }
639 if (mapping->a_ops->writepage == NULL)
640 return PAGE_ACTIVATE;
641
642 if (folio_clear_dirty_for_io(folio)) {
643 int res;
644 struct writeback_control wbc = {
645 .sync_mode = WB_SYNC_NONE,
646 .nr_to_write = SWAP_CLUSTER_MAX,
647 .range_start = 0,
648 .range_end = LLONG_MAX,
649 .for_reclaim = 1,
650 .swap_plug = plug,
651 };
652
653 folio_set_reclaim(folio);
654 res = mapping->a_ops->writepage(&folio->page, &wbc);
655 if (res < 0)
656 handle_write_error(mapping, folio, res);
657 if (res == AOP_WRITEPAGE_ACTIVATE) {
658 folio_clear_reclaim(folio);
659 return PAGE_ACTIVATE;
660 }
661
662 if (!folio_test_writeback(folio)) {
663 /* synchronous write or broken a_ops? */
664 folio_clear_reclaim(folio);
665 }
666 trace_mm_vmscan_write_folio(folio);
667 node_stat_add_folio(folio, NR_VMSCAN_WRITE);
668 return PAGE_SUCCESS;
669 }
670
671 return PAGE_CLEAN;
672}
673
674/*
675 * Same as remove_mapping, but if the folio is removed from the mapping, it
676 * gets returned with a refcount of 0.
677 */
678static int __remove_mapping(struct address_space *mapping, struct folio *folio,
679 bool reclaimed, struct mem_cgroup *target_memcg)
680{
681 int refcount;
682 void *shadow = NULL;
683
684 BUG_ON(!folio_test_locked(folio));
685 BUG_ON(mapping != folio_mapping(folio));
686
687 if (!folio_test_swapcache(folio))
688 spin_lock(&mapping->host->i_lock);
689 xa_lock_irq(&mapping->i_pages);
690 /*
691 * The non racy check for a busy folio.
692 *
693 * Must be careful with the order of the tests. When someone has
694 * a ref to the folio, it may be possible that they dirty it then
695 * drop the reference. So if the dirty flag is tested before the
696 * refcount here, then the following race may occur:
697 *
698 * get_user_pages(&page);
699 * [user mapping goes away]
700 * write_to(page);
701 * !folio_test_dirty(folio) [good]
702 * folio_set_dirty(folio);
703 * folio_put(folio);
704 * !refcount(folio) [good, discard it]
705 *
706 * [oops, our write_to data is lost]
707 *
708 * Reversing the order of the tests ensures such a situation cannot
709 * escape unnoticed. The smp_rmb is needed to ensure the folio->flags
710 * load is not satisfied before that of folio->_refcount.
711 *
712 * Note that if the dirty flag is always set via folio_mark_dirty,
713 * and thus under the i_pages lock, then this ordering is not required.
714 */
715 refcount = 1 + folio_nr_pages(folio);
716 if (!folio_ref_freeze(folio, refcount))
717 goto cannot_free;
718 /* note: atomic_cmpxchg in folio_ref_freeze provides the smp_rmb */
719 if (unlikely(folio_test_dirty(folio))) {
720 folio_ref_unfreeze(folio, refcount);
721 goto cannot_free;
722 }
723
724 if (folio_test_swapcache(folio)) {
725 swp_entry_t swap = folio->swap;
726
727 if (reclaimed && !mapping_exiting(mapping))
728 shadow = workingset_eviction(folio, target_memcg);
729 __delete_from_swap_cache(folio, swap, shadow);
730 mem_cgroup_swapout(folio, swap);
731 xa_unlock_irq(&mapping->i_pages);
732 put_swap_folio(folio, swap);
733 } else {
734 void (*free_folio)(struct folio *);
735
736 free_folio = mapping->a_ops->free_folio;
737 /*
738 * Remember a shadow entry for reclaimed file cache in
739 * order to detect refaults, thus thrashing, later on.
740 *
741 * But don't store shadows in an address space that is
742 * already exiting. This is not just an optimization,
743 * inode reclaim needs to empty out the radix tree or
744 * the nodes are lost. Don't plant shadows behind its
745 * back.
746 *
747 * We also don't store shadows for DAX mappings because the
748 * only page cache folios found in these are zero pages
749 * covering holes, and because we don't want to mix DAX
750 * exceptional entries and shadow exceptional entries in the
751 * same address_space.
752 */
753 if (reclaimed && folio_is_file_lru(folio) &&
754 !mapping_exiting(mapping) && !dax_mapping(mapping))
755 shadow = workingset_eviction(folio, target_memcg);
756 __filemap_remove_folio(folio, shadow);
757 xa_unlock_irq(&mapping->i_pages);
758 if (mapping_shrinkable(mapping))
759 inode_add_lru(mapping->host);
760 spin_unlock(&mapping->host->i_lock);
761
762 if (free_folio)
763 free_folio(folio);
764 }
765
766 return 1;
767
768cannot_free:
769 xa_unlock_irq(&mapping->i_pages);
770 if (!folio_test_swapcache(folio))
771 spin_unlock(&mapping->host->i_lock);
772 return 0;
773}
774
775/**
776 * remove_mapping() - Attempt to remove a folio from its mapping.
777 * @mapping: The address space.
778 * @folio: The folio to remove.
779 *
780 * If the folio is dirty, under writeback or if someone else has a ref
781 * on it, removal will fail.
782 * Return: The number of pages removed from the mapping. 0 if the folio
783 * could not be removed.
784 * Context: The caller should have a single refcount on the folio and
785 * hold its lock.
786 */
787long remove_mapping(struct address_space *mapping, struct folio *folio)
788{
789 if (__remove_mapping(mapping, folio, false, NULL)) {
790 /*
791 * Unfreezing the refcount with 1 effectively
792 * drops the pagecache ref for us without requiring another
793 * atomic operation.
794 */
795 folio_ref_unfreeze(folio, 1);
796 return folio_nr_pages(folio);
797 }
798 return 0;
799}
800
801/**
802 * folio_putback_lru - Put previously isolated folio onto appropriate LRU list.
803 * @folio: Folio to be returned to an LRU list.
804 *
805 * Add previously isolated @folio to appropriate LRU list.
806 * The folio may still be unevictable for other reasons.
807 *
808 * Context: lru_lock must not be held, interrupts must be enabled.
809 */
810void folio_putback_lru(struct folio *folio)
811{
812 folio_add_lru(folio);
813 folio_put(folio); /* drop ref from isolate */
814}
815
816enum folio_references {
817 FOLIOREF_RECLAIM,
818 FOLIOREF_RECLAIM_CLEAN,
819 FOLIOREF_KEEP,
820 FOLIOREF_ACTIVATE,
821};
822
823static enum folio_references folio_check_references(struct folio *folio,
824 struct scan_control *sc)
825{
826 int referenced_ptes, referenced_folio;
827 unsigned long vm_flags;
828
829 referenced_ptes = folio_referenced(folio, 1, sc->target_mem_cgroup,
830 &vm_flags);
831 referenced_folio = folio_test_clear_referenced(folio);
832
833 /*
834 * The supposedly reclaimable folio was found to be in a VM_LOCKED vma.
835 * Let the folio, now marked Mlocked, be moved to the unevictable list.
836 */
837 if (vm_flags & VM_LOCKED)
838 return FOLIOREF_ACTIVATE;
839
840 /* rmap lock contention: rotate */
841 if (referenced_ptes == -1)
842 return FOLIOREF_KEEP;
843
844 if (referenced_ptes) {
845 /*
846 * All mapped folios start out with page table
847 * references from the instantiating fault, so we need
848 * to look twice if a mapped file/anon folio is used more
849 * than once.
850 *
851 * Mark it and spare it for another trip around the
852 * inactive list. Another page table reference will
853 * lead to its activation.
854 *
855 * Note: the mark is set for activated folios as well
856 * so that recently deactivated but used folios are
857 * quickly recovered.
858 */
859 folio_set_referenced(folio);
860
861 if (referenced_folio || referenced_ptes > 1)
862 return FOLIOREF_ACTIVATE;
863
864 /*
865 * Activate file-backed executable folios after first usage.
866 */
867 if ((vm_flags & VM_EXEC) && folio_is_file_lru(folio))
868 return FOLIOREF_ACTIVATE;
869
870 return FOLIOREF_KEEP;
871 }
872
873 /* Reclaim if clean, defer dirty folios to writeback */
874 if (referenced_folio && folio_is_file_lru(folio))
875 return FOLIOREF_RECLAIM_CLEAN;
876
877 return FOLIOREF_RECLAIM;
878}
879
880/* Check if a folio is dirty or under writeback */
881static void folio_check_dirty_writeback(struct folio *folio,
882 bool *dirty, bool *writeback)
883{
884 struct address_space *mapping;
885
886 /*
887 * Anonymous folios are not handled by flushers and must be written
888 * from reclaim context. Do not stall reclaim based on them.
889 * MADV_FREE anonymous folios are put into inactive file list too.
890 * They could be mistakenly treated as file lru. So further anon
891 * test is needed.
892 */
893 if (!folio_is_file_lru(folio) ||
894 (folio_test_anon(folio) && !folio_test_swapbacked(folio))) {
895 *dirty = false;
896 *writeback = false;
897 return;
898 }
899
900 /* By default assume that the folio flags are accurate */
901 *dirty = folio_test_dirty(folio);
902 *writeback = folio_test_writeback(folio);
903
904 /* Verify dirty/writeback state if the filesystem supports it */
905 if (!folio_test_private(folio))
906 return;
907
908 mapping = folio_mapping(folio);
909 if (mapping && mapping->a_ops->is_dirty_writeback)
910 mapping->a_ops->is_dirty_writeback(folio, dirty, writeback);
911}
912
913static struct folio *alloc_demote_folio(struct folio *src,
914 unsigned long private)
915{
916 struct folio *dst;
917 nodemask_t *allowed_mask;
918 struct migration_target_control *mtc;
919
920 mtc = (struct migration_target_control *)private;
921
922 allowed_mask = mtc->nmask;
923 /*
924 * make sure we allocate from the target node first also trying to
925 * demote or reclaim pages from the target node via kswapd if we are
926 * low on free memory on target node. If we don't do this and if
927 * we have free memory on the slower(lower) memtier, we would start
928 * allocating pages from slower(lower) memory tiers without even forcing
929 * a demotion of cold pages from the target memtier. This can result
930 * in the kernel placing hot pages in slower(lower) memory tiers.
931 */
932 mtc->nmask = NULL;
933 mtc->gfp_mask |= __GFP_THISNODE;
934 dst = alloc_migration_target(src, (unsigned long)mtc);
935 if (dst)
936 return dst;
937
938 mtc->gfp_mask &= ~__GFP_THISNODE;
939 mtc->nmask = allowed_mask;
940
941 return alloc_migration_target(src, (unsigned long)mtc);
942}
943
944/*
945 * Take folios on @demote_folios and attempt to demote them to another node.
946 * Folios which are not demoted are left on @demote_folios.
947 */
948static unsigned int demote_folio_list(struct list_head *demote_folios,
949 struct pglist_data *pgdat)
950{
951 int target_nid = next_demotion_node(pgdat->node_id);
952 unsigned int nr_succeeded;
953 nodemask_t allowed_mask;
954
955 struct migration_target_control mtc = {
956 /*
957 * Allocate from 'node', or fail quickly and quietly.
958 * When this happens, 'page' will likely just be discarded
959 * instead of migrated.
960 */
961 .gfp_mask = (GFP_HIGHUSER_MOVABLE & ~__GFP_RECLAIM) | __GFP_NOWARN |
962 __GFP_NOMEMALLOC | GFP_NOWAIT,
963 .nid = target_nid,
964 .nmask = &allowed_mask
965 };
966
967 if (list_empty(demote_folios))
968 return 0;
969
970 if (target_nid == NUMA_NO_NODE)
971 return 0;
972
973 node_get_allowed_targets(pgdat, &allowed_mask);
974
975 /* Demotion ignores all cpuset and mempolicy settings */
976 migrate_pages(demote_folios, alloc_demote_folio, NULL,
977 (unsigned long)&mtc, MIGRATE_ASYNC, MR_DEMOTION,
978 &nr_succeeded);
979
980 mod_node_page_state(pgdat, PGDEMOTE_KSWAPD + reclaimer_offset(),
981 nr_succeeded);
982
983 return nr_succeeded;
984}
985
986static bool may_enter_fs(struct folio *folio, gfp_t gfp_mask)
987{
988 if (gfp_mask & __GFP_FS)
989 return true;
990 if (!folio_test_swapcache(folio) || !(gfp_mask & __GFP_IO))
991 return false;
992 /*
993 * We can "enter_fs" for swap-cache with only __GFP_IO
994 * providing this isn't SWP_FS_OPS.
995 * ->flags can be updated non-atomicially (scan_swap_map_slots),
996 * but that will never affect SWP_FS_OPS, so the data_race
997 * is safe.
998 */
999 return !data_race(folio_swap_flags(folio) & SWP_FS_OPS);
1000}
1001
1002/*
1003 * shrink_folio_list() returns the number of reclaimed pages
1004 */
1005static unsigned int shrink_folio_list(struct list_head *folio_list,
1006 struct pglist_data *pgdat, struct scan_control *sc,
1007 struct reclaim_stat *stat, bool ignore_references)
1008{
1009 LIST_HEAD(ret_folios);
1010 LIST_HEAD(free_folios);
1011 LIST_HEAD(demote_folios);
1012 unsigned int nr_reclaimed = 0;
1013 unsigned int pgactivate = 0;
1014 bool do_demote_pass;
1015 struct swap_iocb *plug = NULL;
1016
1017 memset(stat, 0, sizeof(*stat));
1018 cond_resched();
1019 do_demote_pass = can_demote(pgdat->node_id, sc);
1020
1021retry:
1022 while (!list_empty(folio_list)) {
1023 struct address_space *mapping;
1024 struct folio *folio;
1025 enum folio_references references = FOLIOREF_RECLAIM;
1026 bool dirty, writeback;
1027 unsigned int nr_pages;
1028
1029 cond_resched();
1030
1031 folio = lru_to_folio(folio_list);
1032 list_del(&folio->lru);
1033
1034 if (!folio_trylock(folio))
1035 goto keep;
1036
1037 VM_BUG_ON_FOLIO(folio_test_active(folio), folio);
1038
1039 nr_pages = folio_nr_pages(folio);
1040
1041 /* Account the number of base pages */
1042 sc->nr_scanned += nr_pages;
1043
1044 if (unlikely(!folio_evictable(folio)))
1045 goto activate_locked;
1046
1047 if (!sc->may_unmap && folio_mapped(folio))
1048 goto keep_locked;
1049
1050 /* folio_update_gen() tried to promote this page? */
1051 if (lru_gen_enabled() && !ignore_references &&
1052 folio_mapped(folio) && folio_test_referenced(folio))
1053 goto keep_locked;
1054
1055 /*
1056 * The number of dirty pages determines if a node is marked
1057 * reclaim_congested. kswapd will stall and start writing
1058 * folios if the tail of the LRU is all dirty unqueued folios.
1059 */
1060 folio_check_dirty_writeback(folio, &dirty, &writeback);
1061 if (dirty || writeback)
1062 stat->nr_dirty += nr_pages;
1063
1064 if (dirty && !writeback)
1065 stat->nr_unqueued_dirty += nr_pages;
1066
1067 /*
1068 * Treat this folio as congested if folios are cycling
1069 * through the LRU so quickly that the folios marked
1070 * for immediate reclaim are making it to the end of
1071 * the LRU a second time.
1072 */
1073 if (writeback && folio_test_reclaim(folio))
1074 stat->nr_congested += nr_pages;
1075
1076 /*
1077 * If a folio at the tail of the LRU is under writeback, there
1078 * are three cases to consider.
1079 *
1080 * 1) If reclaim is encountering an excessive number
1081 * of folios under writeback and this folio has both
1082 * the writeback and reclaim flags set, then it
1083 * indicates that folios are being queued for I/O but
1084 * are being recycled through the LRU before the I/O
1085 * can complete. Waiting on the folio itself risks an
1086 * indefinite stall if it is impossible to writeback
1087 * the folio due to I/O error or disconnected storage
1088 * so instead note that the LRU is being scanned too
1089 * quickly and the caller can stall after the folio
1090 * list has been processed.
1091 *
1092 * 2) Global or new memcg reclaim encounters a folio that is
1093 * not marked for immediate reclaim, or the caller does not
1094 * have __GFP_FS (or __GFP_IO if it's simply going to swap,
1095 * not to fs). In this case mark the folio for immediate
1096 * reclaim and continue scanning.
1097 *
1098 * Require may_enter_fs() because we would wait on fs, which
1099 * may not have submitted I/O yet. And the loop driver might
1100 * enter reclaim, and deadlock if it waits on a folio for
1101 * which it is needed to do the write (loop masks off
1102 * __GFP_IO|__GFP_FS for this reason); but more thought
1103 * would probably show more reasons.
1104 *
1105 * 3) Legacy memcg encounters a folio that already has the
1106 * reclaim flag set. memcg does not have any dirty folio
1107 * throttling so we could easily OOM just because too many
1108 * folios are in writeback and there is nothing else to
1109 * reclaim. Wait for the writeback to complete.
1110 *
1111 * In cases 1) and 2) we activate the folios to get them out of
1112 * the way while we continue scanning for clean folios on the
1113 * inactive list and refilling from the active list. The
1114 * observation here is that waiting for disk writes is more
1115 * expensive than potentially causing reloads down the line.
1116 * Since they're marked for immediate reclaim, they won't put
1117 * memory pressure on the cache working set any longer than it
1118 * takes to write them to disk.
1119 */
1120 if (folio_test_writeback(folio)) {
1121 /* Case 1 above */
1122 if (current_is_kswapd() &&
1123 folio_test_reclaim(folio) &&
1124 test_bit(PGDAT_WRITEBACK, &pgdat->flags)) {
1125 stat->nr_immediate += nr_pages;
1126 goto activate_locked;
1127
1128 /* Case 2 above */
1129 } else if (writeback_throttling_sane(sc) ||
1130 !folio_test_reclaim(folio) ||
1131 !may_enter_fs(folio, sc->gfp_mask)) {
1132 /*
1133 * This is slightly racy -
1134 * folio_end_writeback() might have
1135 * just cleared the reclaim flag, then
1136 * setting the reclaim flag here ends up
1137 * interpreted as the readahead flag - but
1138 * that does not matter enough to care.
1139 * What we do want is for this folio to
1140 * have the reclaim flag set next time
1141 * memcg reclaim reaches the tests above,
1142 * so it will then wait for writeback to
1143 * avoid OOM; and it's also appropriate
1144 * in global reclaim.
1145 */
1146 folio_set_reclaim(folio);
1147 stat->nr_writeback += nr_pages;
1148 goto activate_locked;
1149
1150 /* Case 3 above */
1151 } else {
1152 folio_unlock(folio);
1153 folio_wait_writeback(folio);
1154 /* then go back and try same folio again */
1155 list_add_tail(&folio->lru, folio_list);
1156 continue;
1157 }
1158 }
1159
1160 if (!ignore_references)
1161 references = folio_check_references(folio, sc);
1162
1163 switch (references) {
1164 case FOLIOREF_ACTIVATE:
1165 goto activate_locked;
1166 case FOLIOREF_KEEP:
1167 stat->nr_ref_keep += nr_pages;
1168 goto keep_locked;
1169 case FOLIOREF_RECLAIM:
1170 case FOLIOREF_RECLAIM_CLEAN:
1171 ; /* try to reclaim the folio below */
1172 }
1173
1174 /*
1175 * Before reclaiming the folio, try to relocate
1176 * its contents to another node.
1177 */
1178 if (do_demote_pass &&
1179 (thp_migration_supported() || !folio_test_large(folio))) {
1180 list_add(&folio->lru, &demote_folios);
1181 folio_unlock(folio);
1182 continue;
1183 }
1184
1185 /*
1186 * Anonymous process memory has backing store?
1187 * Try to allocate it some swap space here.
1188 * Lazyfree folio could be freed directly
1189 */
1190 if (folio_test_anon(folio) && folio_test_swapbacked(folio)) {
1191 if (!folio_test_swapcache(folio)) {
1192 if (!(sc->gfp_mask & __GFP_IO))
1193 goto keep_locked;
1194 if (folio_maybe_dma_pinned(folio))
1195 goto keep_locked;
1196 if (folio_test_large(folio)) {
1197 /* cannot split folio, skip it */
1198 if (!can_split_folio(folio, NULL))
1199 goto activate_locked;
1200 /*
1201 * Split folios without a PMD map right
1202 * away. Chances are some or all of the
1203 * tail pages can be freed without IO.
1204 */
1205 if (!folio_entire_mapcount(folio) &&
1206 split_folio_to_list(folio,
1207 folio_list))
1208 goto activate_locked;
1209 }
1210 if (!add_to_swap(folio)) {
1211 if (!folio_test_large(folio))
1212 goto activate_locked_split;
1213 /* Fallback to swap normal pages */
1214 if (split_folio_to_list(folio,
1215 folio_list))
1216 goto activate_locked;
1217#ifdef CONFIG_TRANSPARENT_HUGEPAGE
1218 count_memcg_folio_events(folio, THP_SWPOUT_FALLBACK, 1);
1219 count_vm_event(THP_SWPOUT_FALLBACK);
1220#endif
1221 if (!add_to_swap(folio))
1222 goto activate_locked_split;
1223 }
1224 }
1225 } else if (folio_test_swapbacked(folio) &&
1226 folio_test_large(folio)) {
1227 /* Split shmem folio */
1228 if (split_folio_to_list(folio, folio_list))
1229 goto keep_locked;
1230 }
1231
1232 /*
1233 * If the folio was split above, the tail pages will make
1234 * their own pass through this function and be accounted
1235 * then.
1236 */
1237 if ((nr_pages > 1) && !folio_test_large(folio)) {
1238 sc->nr_scanned -= (nr_pages - 1);
1239 nr_pages = 1;
1240 }
1241
1242 /*
1243 * The folio is mapped into the page tables of one or more
1244 * processes. Try to unmap it here.
1245 */
1246 if (folio_mapped(folio)) {
1247 enum ttu_flags flags = TTU_BATCH_FLUSH;
1248 bool was_swapbacked = folio_test_swapbacked(folio);
1249
1250 if (folio_test_pmd_mappable(folio))
1251 flags |= TTU_SPLIT_HUGE_PMD;
1252
1253 try_to_unmap(folio, flags);
1254 if (folio_mapped(folio)) {
1255 stat->nr_unmap_fail += nr_pages;
1256 if (!was_swapbacked &&
1257 folio_test_swapbacked(folio))
1258 stat->nr_lazyfree_fail += nr_pages;
1259 goto activate_locked;
1260 }
1261 }
1262
1263 /*
1264 * Folio is unmapped now so it cannot be newly pinned anymore.
1265 * No point in trying to reclaim folio if it is pinned.
1266 * Furthermore we don't want to reclaim underlying fs metadata
1267 * if the folio is pinned and thus potentially modified by the
1268 * pinning process as that may upset the filesystem.
1269 */
1270 if (folio_maybe_dma_pinned(folio))
1271 goto activate_locked;
1272
1273 mapping = folio_mapping(folio);
1274 if (folio_test_dirty(folio)) {
1275 /*
1276 * Only kswapd can writeback filesystem folios
1277 * to avoid risk of stack overflow. But avoid
1278 * injecting inefficient single-folio I/O into
1279 * flusher writeback as much as possible: only
1280 * write folios when we've encountered many
1281 * dirty folios, and when we've already scanned
1282 * the rest of the LRU for clean folios and see
1283 * the same dirty folios again (with the reclaim
1284 * flag set).
1285 */
1286 if (folio_is_file_lru(folio) &&
1287 (!current_is_kswapd() ||
1288 !folio_test_reclaim(folio) ||
1289 !test_bit(PGDAT_DIRTY, &pgdat->flags))) {
1290 /*
1291 * Immediately reclaim when written back.
1292 * Similar in principle to folio_deactivate()
1293 * except we already have the folio isolated
1294 * and know it's dirty
1295 */
1296 node_stat_mod_folio(folio, NR_VMSCAN_IMMEDIATE,
1297 nr_pages);
1298 folio_set_reclaim(folio);
1299
1300 goto activate_locked;
1301 }
1302
1303 if (references == FOLIOREF_RECLAIM_CLEAN)
1304 goto keep_locked;
1305 if (!may_enter_fs(folio, sc->gfp_mask))
1306 goto keep_locked;
1307 if (!sc->may_writepage)
1308 goto keep_locked;
1309
1310 /*
1311 * Folio is dirty. Flush the TLB if a writable entry
1312 * potentially exists to avoid CPU writes after I/O
1313 * starts and then write it out here.
1314 */
1315 try_to_unmap_flush_dirty();
1316 switch (pageout(folio, mapping, &plug)) {
1317 case PAGE_KEEP:
1318 goto keep_locked;
1319 case PAGE_ACTIVATE:
1320 goto activate_locked;
1321 case PAGE_SUCCESS:
1322 stat->nr_pageout += nr_pages;
1323
1324 if (folio_test_writeback(folio))
1325 goto keep;
1326 if (folio_test_dirty(folio))
1327 goto keep;
1328
1329 /*
1330 * A synchronous write - probably a ramdisk. Go
1331 * ahead and try to reclaim the folio.
1332 */
1333 if (!folio_trylock(folio))
1334 goto keep;
1335 if (folio_test_dirty(folio) ||
1336 folio_test_writeback(folio))
1337 goto keep_locked;
1338 mapping = folio_mapping(folio);
1339 fallthrough;
1340 case PAGE_CLEAN:
1341 ; /* try to free the folio below */
1342 }
1343 }
1344
1345 /*
1346 * If the folio has buffers, try to free the buffer
1347 * mappings associated with this folio. If we succeed
1348 * we try to free the folio as well.
1349 *
1350 * We do this even if the folio is dirty.
1351 * filemap_release_folio() does not perform I/O, but it
1352 * is possible for a folio to have the dirty flag set,
1353 * but it is actually clean (all its buffers are clean).
1354 * This happens if the buffers were written out directly,
1355 * with submit_bh(). ext3 will do this, as well as
1356 * the blockdev mapping. filemap_release_folio() will
1357 * discover that cleanness and will drop the buffers
1358 * and mark the folio clean - it can be freed.
1359 *
1360 * Rarely, folios can have buffers and no ->mapping.
1361 * These are the folios which were not successfully
1362 * invalidated in truncate_cleanup_folio(). We try to
1363 * drop those buffers here and if that worked, and the
1364 * folio is no longer mapped into process address space
1365 * (refcount == 1) it can be freed. Otherwise, leave
1366 * the folio on the LRU so it is swappable.
1367 */
1368 if (folio_needs_release(folio)) {
1369 if (!filemap_release_folio(folio, sc->gfp_mask))
1370 goto activate_locked;
1371 if (!mapping && folio_ref_count(folio) == 1) {
1372 folio_unlock(folio);
1373 if (folio_put_testzero(folio))
1374 goto free_it;
1375 else {
1376 /*
1377 * rare race with speculative reference.
1378 * the speculative reference will free
1379 * this folio shortly, so we may
1380 * increment nr_reclaimed here (and
1381 * leave it off the LRU).
1382 */
1383 nr_reclaimed += nr_pages;
1384 continue;
1385 }
1386 }
1387 }
1388
1389 if (folio_test_anon(folio) && !folio_test_swapbacked(folio)) {
1390 /* follow __remove_mapping for reference */
1391 if (!folio_ref_freeze(folio, 1))
1392 goto keep_locked;
1393 /*
1394 * The folio has only one reference left, which is
1395 * from the isolation. After the caller puts the
1396 * folio back on the lru and drops the reference, the
1397 * folio will be freed anyway. It doesn't matter
1398 * which lru it goes on. So we don't bother checking
1399 * the dirty flag here.
1400 */
1401 count_vm_events(PGLAZYFREED, nr_pages);
1402 count_memcg_folio_events(folio, PGLAZYFREED, nr_pages);
1403 } else if (!mapping || !__remove_mapping(mapping, folio, true,
1404 sc->target_mem_cgroup))
1405 goto keep_locked;
1406
1407 folio_unlock(folio);
1408free_it:
1409 /*
1410 * Folio may get swapped out as a whole, need to account
1411 * all pages in it.
1412 */
1413 nr_reclaimed += nr_pages;
1414
1415 /*
1416 * Is there need to periodically free_folio_list? It would
1417 * appear not as the counts should be low
1418 */
1419 if (unlikely(folio_test_large(folio)))
1420 destroy_large_folio(folio);
1421 else
1422 list_add(&folio->lru, &free_folios);
1423 continue;
1424
1425activate_locked_split:
1426 /*
1427 * The tail pages that are failed to add into swap cache
1428 * reach here. Fixup nr_scanned and nr_pages.
1429 */
1430 if (nr_pages > 1) {
1431 sc->nr_scanned -= (nr_pages - 1);
1432 nr_pages = 1;
1433 }
1434activate_locked:
1435 /* Not a candidate for swapping, so reclaim swap space. */
1436 if (folio_test_swapcache(folio) &&
1437 (mem_cgroup_swap_full(folio) || folio_test_mlocked(folio)))
1438 folio_free_swap(folio);
1439 VM_BUG_ON_FOLIO(folio_test_active(folio), folio);
1440 if (!folio_test_mlocked(folio)) {
1441 int type = folio_is_file_lru(folio);
1442 folio_set_active(folio);
1443 stat->nr_activate[type] += nr_pages;
1444 count_memcg_folio_events(folio, PGACTIVATE, nr_pages);
1445 }
1446keep_locked:
1447 folio_unlock(folio);
1448keep:
1449 list_add(&folio->lru, &ret_folios);
1450 VM_BUG_ON_FOLIO(folio_test_lru(folio) ||
1451 folio_test_unevictable(folio), folio);
1452 }
1453 /* 'folio_list' is always empty here */
1454
1455 /* Migrate folios selected for demotion */
1456 nr_reclaimed += demote_folio_list(&demote_folios, pgdat);
1457 /* Folios that could not be demoted are still in @demote_folios */
1458 if (!list_empty(&demote_folios)) {
1459 /* Folios which weren't demoted go back on @folio_list */
1460 list_splice_init(&demote_folios, folio_list);
1461
1462 /*
1463 * goto retry to reclaim the undemoted folios in folio_list if
1464 * desired.
1465 *
1466 * Reclaiming directly from top tier nodes is not often desired
1467 * due to it breaking the LRU ordering: in general memory
1468 * should be reclaimed from lower tier nodes and demoted from
1469 * top tier nodes.
1470 *
1471 * However, disabling reclaim from top tier nodes entirely
1472 * would cause ooms in edge scenarios where lower tier memory
1473 * is unreclaimable for whatever reason, eg memory being
1474 * mlocked or too hot to reclaim. We can disable reclaim
1475 * from top tier nodes in proactive reclaim though as that is
1476 * not real memory pressure.
1477 */
1478 if (!sc->proactive) {
1479 do_demote_pass = false;
1480 goto retry;
1481 }
1482 }
1483
1484 pgactivate = stat->nr_activate[0] + stat->nr_activate[1];
1485
1486 mem_cgroup_uncharge_list(&free_folios);
1487 try_to_unmap_flush();
1488 free_unref_page_list(&free_folios);
1489
1490 list_splice(&ret_folios, folio_list);
1491 count_vm_events(PGACTIVATE, pgactivate);
1492
1493 if (plug)
1494 swap_write_unplug(plug);
1495 return nr_reclaimed;
1496}
1497
1498unsigned int reclaim_clean_pages_from_list(struct zone *zone,
1499 struct list_head *folio_list)
1500{
1501 struct scan_control sc = {
1502 .gfp_mask = GFP_KERNEL,
1503 .may_unmap = 1,
1504 };
1505 struct reclaim_stat stat;
1506 unsigned int nr_reclaimed;
1507 struct folio *folio, *next;
1508 LIST_HEAD(clean_folios);
1509 unsigned int noreclaim_flag;
1510
1511 list_for_each_entry_safe(folio, next, folio_list, lru) {
1512 if (!folio_test_hugetlb(folio) && folio_is_file_lru(folio) &&
1513 !folio_test_dirty(folio) && !__folio_test_movable(folio) &&
1514 !folio_test_unevictable(folio)) {
1515 folio_clear_active(folio);
1516 list_move(&folio->lru, &clean_folios);
1517 }
1518 }
1519
1520 /*
1521 * We should be safe here since we are only dealing with file pages and
1522 * we are not kswapd and therefore cannot write dirty file pages. But
1523 * call memalloc_noreclaim_save() anyway, just in case these conditions
1524 * change in the future.
1525 */
1526 noreclaim_flag = memalloc_noreclaim_save();
1527 nr_reclaimed = shrink_folio_list(&clean_folios, zone->zone_pgdat, &sc,
1528 &stat, true);
1529 memalloc_noreclaim_restore(noreclaim_flag);
1530
1531 list_splice(&clean_folios, folio_list);
1532 mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE,
1533 -(long)nr_reclaimed);
1534 /*
1535 * Since lazyfree pages are isolated from file LRU from the beginning,
1536 * they will rotate back to anonymous LRU in the end if it failed to
1537 * discard so isolated count will be mismatched.
1538 * Compensate the isolated count for both LRU lists.
1539 */
1540 mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_ANON,
1541 stat.nr_lazyfree_fail);
1542 mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE,
1543 -(long)stat.nr_lazyfree_fail);
1544 return nr_reclaimed;
1545}
1546
1547/*
1548 * Update LRU sizes after isolating pages. The LRU size updates must
1549 * be complete before mem_cgroup_update_lru_size due to a sanity check.
1550 */
1551static __always_inline void update_lru_sizes(struct lruvec *lruvec,
1552 enum lru_list lru, unsigned long *nr_zone_taken)
1553{
1554 int zid;
1555
1556 for (zid = 0; zid < MAX_NR_ZONES; zid++) {
1557 if (!nr_zone_taken[zid])
1558 continue;
1559
1560 update_lru_size(lruvec, lru, zid, -nr_zone_taken[zid]);
1561 }
1562
1563}
1564
1565#ifdef CONFIG_CMA
1566/*
1567 * It is waste of effort to scan and reclaim CMA pages if it is not available
1568 * for current allocation context. Kswapd can not be enrolled as it can not
1569 * distinguish this scenario by using sc->gfp_mask = GFP_KERNEL
1570 */
1571static bool skip_cma(struct folio *folio, struct scan_control *sc)
1572{
1573 return !current_is_kswapd() &&
1574 gfp_migratetype(sc->gfp_mask) != MIGRATE_MOVABLE &&
1575 folio_migratetype(folio) == MIGRATE_CMA;
1576}
1577#else
1578static bool skip_cma(struct folio *folio, struct scan_control *sc)
1579{
1580 return false;
1581}
1582#endif
1583
1584/*
1585 * Isolating page from the lruvec to fill in @dst list by nr_to_scan times.
1586 *
1587 * lruvec->lru_lock is heavily contended. Some of the functions that
1588 * shrink the lists perform better by taking out a batch of pages
1589 * and working on them outside the LRU lock.
1590 *
1591 * For pagecache intensive workloads, this function is the hottest
1592 * spot in the kernel (apart from copy_*_user functions).
1593 *
1594 * Lru_lock must be held before calling this function.
1595 *
1596 * @nr_to_scan: The number of eligible pages to look through on the list.
1597 * @lruvec: The LRU vector to pull pages from.
1598 * @dst: The temp list to put pages on to.
1599 * @nr_scanned: The number of pages that were scanned.
1600 * @sc: The scan_control struct for this reclaim session
1601 * @lru: LRU list id for isolating
1602 *
1603 * returns how many pages were moved onto *@dst.
1604 */
1605static unsigned long isolate_lru_folios(unsigned long nr_to_scan,
1606 struct lruvec *lruvec, struct list_head *dst,
1607 unsigned long *nr_scanned, struct scan_control *sc,
1608 enum lru_list lru)
1609{
1610 struct list_head *src = &lruvec->lists[lru];
1611 unsigned long nr_taken = 0;
1612 unsigned long nr_zone_taken[MAX_NR_ZONES] = { 0 };
1613 unsigned long nr_skipped[MAX_NR_ZONES] = { 0, };
1614 unsigned long skipped = 0;
1615 unsigned long scan, total_scan, nr_pages;
1616 LIST_HEAD(folios_skipped);
1617
1618 total_scan = 0;
1619 scan = 0;
1620 while (scan < nr_to_scan && !list_empty(src)) {
1621 struct list_head *move_to = src;
1622 struct folio *folio;
1623
1624 folio = lru_to_folio(src);
1625 prefetchw_prev_lru_folio(folio, src, flags);
1626
1627 nr_pages = folio_nr_pages(folio);
1628 total_scan += nr_pages;
1629
1630 if (folio_zonenum(folio) > sc->reclaim_idx ||
1631 skip_cma(folio, sc)) {
1632 nr_skipped[folio_zonenum(folio)] += nr_pages;
1633 move_to = &folios_skipped;
1634 goto move;
1635 }
1636
1637 /*
1638 * Do not count skipped folios because that makes the function
1639 * return with no isolated folios if the LRU mostly contains
1640 * ineligible folios. This causes the VM to not reclaim any
1641 * folios, triggering a premature OOM.
1642 * Account all pages in a folio.
1643 */
1644 scan += nr_pages;
1645
1646 if (!folio_test_lru(folio))
1647 goto move;
1648 if (!sc->may_unmap && folio_mapped(folio))
1649 goto move;
1650
1651 /*
1652 * Be careful not to clear the lru flag until after we're
1653 * sure the folio is not being freed elsewhere -- the
1654 * folio release code relies on it.
1655 */
1656 if (unlikely(!folio_try_get(folio)))
1657 goto move;
1658
1659 if (!folio_test_clear_lru(folio)) {
1660 /* Another thread is already isolating this folio */
1661 folio_put(folio);
1662 goto move;
1663 }
1664
1665 nr_taken += nr_pages;
1666 nr_zone_taken[folio_zonenum(folio)] += nr_pages;
1667 move_to = dst;
1668move:
1669 list_move(&folio->lru, move_to);
1670 }
1671
1672 /*
1673 * Splice any skipped folios to the start of the LRU list. Note that
1674 * this disrupts the LRU order when reclaiming for lower zones but
1675 * we cannot splice to the tail. If we did then the SWAP_CLUSTER_MAX
1676 * scanning would soon rescan the same folios to skip and waste lots
1677 * of cpu cycles.
1678 */
1679 if (!list_empty(&folios_skipped)) {
1680 int zid;
1681
1682 list_splice(&folios_skipped, src);
1683 for (zid = 0; zid < MAX_NR_ZONES; zid++) {
1684 if (!nr_skipped[zid])
1685 continue;
1686
1687 __count_zid_vm_events(PGSCAN_SKIP, zid, nr_skipped[zid]);
1688 skipped += nr_skipped[zid];
1689 }
1690 }
1691 *nr_scanned = total_scan;
1692 trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, nr_to_scan,
1693 total_scan, skipped, nr_taken, lru);
1694 update_lru_sizes(lruvec, lru, nr_zone_taken);
1695 return nr_taken;
1696}
1697
1698/**
1699 * folio_isolate_lru() - Try to isolate a folio from its LRU list.
1700 * @folio: Folio to isolate from its LRU list.
1701 *
1702 * Isolate a @folio from an LRU list and adjust the vmstat statistic
1703 * corresponding to whatever LRU list the folio was on.
1704 *
1705 * The folio will have its LRU flag cleared. If it was found on the
1706 * active list, it will have the Active flag set. If it was found on the
1707 * unevictable list, it will have the Unevictable flag set. These flags
1708 * may need to be cleared by the caller before letting the page go.
1709 *
1710 * Context:
1711 *
1712 * (1) Must be called with an elevated refcount on the folio. This is a
1713 * fundamental difference from isolate_lru_folios() (which is called
1714 * without a stable reference).
1715 * (2) The lru_lock must not be held.
1716 * (3) Interrupts must be enabled.
1717 *
1718 * Return: true if the folio was removed from an LRU list.
1719 * false if the folio was not on an LRU list.
1720 */
1721bool folio_isolate_lru(struct folio *folio)
1722{
1723 bool ret = false;
1724
1725 VM_BUG_ON_FOLIO(!folio_ref_count(folio), folio);
1726
1727 if (folio_test_clear_lru(folio)) {
1728 struct lruvec *lruvec;
1729
1730 folio_get(folio);
1731 lruvec = folio_lruvec_lock_irq(folio);
1732 lruvec_del_folio(lruvec, folio);
1733 unlock_page_lruvec_irq(lruvec);
1734 ret = true;
1735 }
1736
1737 return ret;
1738}
1739
1740/*
1741 * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and
1742 * then get rescheduled. When there are massive number of tasks doing page
1743 * allocation, such sleeping direct reclaimers may keep piling up on each CPU,
1744 * the LRU list will go small and be scanned faster than necessary, leading to
1745 * unnecessary swapping, thrashing and OOM.
1746 */
1747static int too_many_isolated(struct pglist_data *pgdat, int file,
1748 struct scan_control *sc)
1749{
1750 unsigned long inactive, isolated;
1751 bool too_many;
1752
1753 if (current_is_kswapd())
1754 return 0;
1755
1756 if (!writeback_throttling_sane(sc))
1757 return 0;
1758
1759 if (file) {
1760 inactive = node_page_state(pgdat, NR_INACTIVE_FILE);
1761 isolated = node_page_state(pgdat, NR_ISOLATED_FILE);
1762 } else {
1763 inactive = node_page_state(pgdat, NR_INACTIVE_ANON);
1764 isolated = node_page_state(pgdat, NR_ISOLATED_ANON);
1765 }
1766
1767 /*
1768 * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they
1769 * won't get blocked by normal direct-reclaimers, forming a circular
1770 * deadlock.
1771 */
1772 if (gfp_has_io_fs(sc->gfp_mask))
1773 inactive >>= 3;
1774
1775 too_many = isolated > inactive;
1776
1777 /* Wake up tasks throttled due to too_many_isolated. */
1778 if (!too_many)
1779 wake_throttle_isolated(pgdat);
1780
1781 return too_many;
1782}
1783
1784/*
1785 * move_folios_to_lru() moves folios from private @list to appropriate LRU list.
1786 * On return, @list is reused as a list of folios to be freed by the caller.
1787 *
1788 * Returns the number of pages moved to the given lruvec.
1789 */
1790static unsigned int move_folios_to_lru(struct lruvec *lruvec,
1791 struct list_head *list)
1792{
1793 int nr_pages, nr_moved = 0;
1794 LIST_HEAD(folios_to_free);
1795
1796 while (!list_empty(list)) {
1797 struct folio *folio = lru_to_folio(list);
1798
1799 VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
1800 list_del(&folio->lru);
1801 if (unlikely(!folio_evictable(folio))) {
1802 spin_unlock_irq(&lruvec->lru_lock);
1803 folio_putback_lru(folio);
1804 spin_lock_irq(&lruvec->lru_lock);
1805 continue;
1806 }
1807
1808 /*
1809 * The folio_set_lru needs to be kept here for list integrity.
1810 * Otherwise:
1811 * #0 move_folios_to_lru #1 release_pages
1812 * if (!folio_put_testzero())
1813 * if (folio_put_testzero())
1814 * !lru //skip lru_lock
1815 * folio_set_lru()
1816 * list_add(&folio->lru,)
1817 * list_add(&folio->lru,)
1818 */
1819 folio_set_lru(folio);
1820
1821 if (unlikely(folio_put_testzero(folio))) {
1822 __folio_clear_lru_flags(folio);
1823
1824 if (unlikely(folio_test_large(folio))) {
1825 spin_unlock_irq(&lruvec->lru_lock);
1826 destroy_large_folio(folio);
1827 spin_lock_irq(&lruvec->lru_lock);
1828 } else
1829 list_add(&folio->lru, &folios_to_free);
1830
1831 continue;
1832 }
1833
1834 /*
1835 * All pages were isolated from the same lruvec (and isolation
1836 * inhibits memcg migration).
1837 */
1838 VM_BUG_ON_FOLIO(!folio_matches_lruvec(folio, lruvec), folio);
1839 lruvec_add_folio(lruvec, folio);
1840 nr_pages = folio_nr_pages(folio);
1841 nr_moved += nr_pages;
1842 if (folio_test_active(folio))
1843 workingset_age_nonresident(lruvec, nr_pages);
1844 }
1845
1846 /*
1847 * To save our caller's stack, now use input list for pages to free.
1848 */
1849 list_splice(&folios_to_free, list);
1850
1851 return nr_moved;
1852}
1853
1854/*
1855 * If a kernel thread (such as nfsd for loop-back mounts) services a backing
1856 * device by writing to the page cache it sets PF_LOCAL_THROTTLE. In this case
1857 * we should not throttle. Otherwise it is safe to do so.
1858 */
1859static int current_may_throttle(void)
1860{
1861 return !(current->flags & PF_LOCAL_THROTTLE);
1862}
1863
1864/*
1865 * shrink_inactive_list() is a helper for shrink_node(). It returns the number
1866 * of reclaimed pages
1867 */
1868static unsigned long shrink_inactive_list(unsigned long nr_to_scan,
1869 struct lruvec *lruvec, struct scan_control *sc,
1870 enum lru_list lru)
1871{
1872 LIST_HEAD(folio_list);
1873 unsigned long nr_scanned;
1874 unsigned int nr_reclaimed = 0;
1875 unsigned long nr_taken;
1876 struct reclaim_stat stat;
1877 bool file = is_file_lru(lru);
1878 enum vm_event_item item;
1879 struct pglist_data *pgdat = lruvec_pgdat(lruvec);
1880 bool stalled = false;
1881
1882 while (unlikely(too_many_isolated(pgdat, file, sc))) {
1883 if (stalled)
1884 return 0;
1885
1886 /* wait a bit for the reclaimer. */
1887 stalled = true;
1888 reclaim_throttle(pgdat, VMSCAN_THROTTLE_ISOLATED);
1889
1890 /* We are about to die and free our memory. Return now. */
1891 if (fatal_signal_pending(current))
1892 return SWAP_CLUSTER_MAX;
1893 }
1894
1895 lru_add_drain();
1896
1897 spin_lock_irq(&lruvec->lru_lock);
1898
1899 nr_taken = isolate_lru_folios(nr_to_scan, lruvec, &folio_list,
1900 &nr_scanned, sc, lru);
1901
1902 __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken);
1903 item = PGSCAN_KSWAPD + reclaimer_offset();
1904 if (!cgroup_reclaim(sc))
1905 __count_vm_events(item, nr_scanned);
1906 __count_memcg_events(lruvec_memcg(lruvec), item, nr_scanned);
1907 __count_vm_events(PGSCAN_ANON + file, nr_scanned);
1908
1909 spin_unlock_irq(&lruvec->lru_lock);
1910
1911 if (nr_taken == 0)
1912 return 0;
1913
1914 nr_reclaimed = shrink_folio_list(&folio_list, pgdat, sc, &stat, false);
1915
1916 spin_lock_irq(&lruvec->lru_lock);
1917 move_folios_to_lru(lruvec, &folio_list);
1918
1919 __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
1920 item = PGSTEAL_KSWAPD + reclaimer_offset();
1921 if (!cgroup_reclaim(sc))
1922 __count_vm_events(item, nr_reclaimed);
1923 __count_memcg_events(lruvec_memcg(lruvec), item, nr_reclaimed);
1924 __count_vm_events(PGSTEAL_ANON + file, nr_reclaimed);
1925 spin_unlock_irq(&lruvec->lru_lock);
1926
1927 lru_note_cost(lruvec, file, stat.nr_pageout, nr_scanned - nr_reclaimed);
1928 mem_cgroup_uncharge_list(&folio_list);
1929 free_unref_page_list(&folio_list);
1930
1931 /*
1932 * If dirty folios are scanned that are not queued for IO, it
1933 * implies that flushers are not doing their job. This can
1934 * happen when memory pressure pushes dirty folios to the end of
1935 * the LRU before the dirty limits are breached and the dirty
1936 * data has expired. It can also happen when the proportion of
1937 * dirty folios grows not through writes but through memory
1938 * pressure reclaiming all the clean cache. And in some cases,
1939 * the flushers simply cannot keep up with the allocation
1940 * rate. Nudge the flusher threads in case they are asleep.
1941 */
1942 if (stat.nr_unqueued_dirty == nr_taken) {
1943 wakeup_flusher_threads(WB_REASON_VMSCAN);
1944 /*
1945 * For cgroupv1 dirty throttling is achieved by waking up
1946 * the kernel flusher here and later waiting on folios
1947 * which are in writeback to finish (see shrink_folio_list()).
1948 *
1949 * Flusher may not be able to issue writeback quickly
1950 * enough for cgroupv1 writeback throttling to work
1951 * on a large system.
1952 */
1953 if (!writeback_throttling_sane(sc))
1954 reclaim_throttle(pgdat, VMSCAN_THROTTLE_WRITEBACK);
1955 }
1956
1957 sc->nr.dirty += stat.nr_dirty;
1958 sc->nr.congested += stat.nr_congested;
1959 sc->nr.unqueued_dirty += stat.nr_unqueued_dirty;
1960 sc->nr.writeback += stat.nr_writeback;
1961 sc->nr.immediate += stat.nr_immediate;
1962 sc->nr.taken += nr_taken;
1963 if (file)
1964 sc->nr.file_taken += nr_taken;
1965
1966 trace_mm_vmscan_lru_shrink_inactive(pgdat->node_id,
1967 nr_scanned, nr_reclaimed, &stat, sc->priority, file);
1968 return nr_reclaimed;
1969}
1970
1971/*
1972 * shrink_active_list() moves folios from the active LRU to the inactive LRU.
1973 *
1974 * We move them the other way if the folio is referenced by one or more
1975 * processes.
1976 *
1977 * If the folios are mostly unmapped, the processing is fast and it is
1978 * appropriate to hold lru_lock across the whole operation. But if
1979 * the folios are mapped, the processing is slow (folio_referenced()), so
1980 * we should drop lru_lock around each folio. It's impossible to balance
1981 * this, so instead we remove the folios from the LRU while processing them.
1982 * It is safe to rely on the active flag against the non-LRU folios in here
1983 * because nobody will play with that bit on a non-LRU folio.
1984 *
1985 * The downside is that we have to touch folio->_refcount against each folio.
1986 * But we had to alter folio->flags anyway.
1987 */
1988static void shrink_active_list(unsigned long nr_to_scan,
1989 struct lruvec *lruvec,
1990 struct scan_control *sc,
1991 enum lru_list lru)
1992{
1993 unsigned long nr_taken;
1994 unsigned long nr_scanned;
1995 unsigned long vm_flags;
1996 LIST_HEAD(l_hold); /* The folios which were snipped off */
1997 LIST_HEAD(l_active);
1998 LIST_HEAD(l_inactive);
1999 unsigned nr_deactivate, nr_activate;
2000 unsigned nr_rotated = 0;
2001 int file = is_file_lru(lru);
2002 struct pglist_data *pgdat = lruvec_pgdat(lruvec);
2003
2004 lru_add_drain();
2005
2006 spin_lock_irq(&lruvec->lru_lock);
2007
2008 nr_taken = isolate_lru_folios(nr_to_scan, lruvec, &l_hold,
2009 &nr_scanned, sc, lru);
2010
2011 __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken);
2012
2013 if (!cgroup_reclaim(sc))
2014 __count_vm_events(PGREFILL, nr_scanned);
2015 __count_memcg_events(lruvec_memcg(lruvec), PGREFILL, nr_scanned);
2016
2017 spin_unlock_irq(&lruvec->lru_lock);
2018
2019 while (!list_empty(&l_hold)) {
2020 struct folio *folio;
2021
2022 cond_resched();
2023 folio = lru_to_folio(&l_hold);
2024 list_del(&folio->lru);
2025
2026 if (unlikely(!folio_evictable(folio))) {
2027 folio_putback_lru(folio);
2028 continue;
2029 }
2030
2031 if (unlikely(buffer_heads_over_limit)) {
2032 if (folio_needs_release(folio) &&
2033 folio_trylock(folio)) {
2034 filemap_release_folio(folio, 0);
2035 folio_unlock(folio);
2036 }
2037 }
2038
2039 /* Referenced or rmap lock contention: rotate */
2040 if (folio_referenced(folio, 0, sc->target_mem_cgroup,
2041 &vm_flags) != 0) {
2042 /*
2043 * Identify referenced, file-backed active folios and
2044 * give them one more trip around the active list. So
2045 * that executable code get better chances to stay in
2046 * memory under moderate memory pressure. Anon folios
2047 * are not likely to be evicted by use-once streaming
2048 * IO, plus JVM can create lots of anon VM_EXEC folios,
2049 * so we ignore them here.
2050 */
2051 if ((vm_flags & VM_EXEC) && folio_is_file_lru(folio)) {
2052 nr_rotated += folio_nr_pages(folio);
2053 list_add(&folio->lru, &l_active);
2054 continue;
2055 }
2056 }
2057
2058 folio_clear_active(folio); /* we are de-activating */
2059 folio_set_workingset(folio);
2060 list_add(&folio->lru, &l_inactive);
2061 }
2062
2063 /*
2064 * Move folios back to the lru list.
2065 */
2066 spin_lock_irq(&lruvec->lru_lock);
2067
2068 nr_activate = move_folios_to_lru(lruvec, &l_active);
2069 nr_deactivate = move_folios_to_lru(lruvec, &l_inactive);
2070 /* Keep all free folios in l_active list */
2071 list_splice(&l_inactive, &l_active);
2072
2073 __count_vm_events(PGDEACTIVATE, nr_deactivate);
2074 __count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE, nr_deactivate);
2075
2076 __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
2077 spin_unlock_irq(&lruvec->lru_lock);
2078
2079 if (nr_rotated)
2080 lru_note_cost(lruvec, file, 0, nr_rotated);
2081 mem_cgroup_uncharge_list(&l_active);
2082 free_unref_page_list(&l_active);
2083 trace_mm_vmscan_lru_shrink_active(pgdat->node_id, nr_taken, nr_activate,
2084 nr_deactivate, nr_rotated, sc->priority, file);
2085}
2086
2087static unsigned int reclaim_folio_list(struct list_head *folio_list,
2088 struct pglist_data *pgdat)
2089{
2090 struct reclaim_stat dummy_stat;
2091 unsigned int nr_reclaimed;
2092 struct folio *folio;
2093 struct scan_control sc = {
2094 .gfp_mask = GFP_KERNEL,
2095 .may_writepage = 1,
2096 .may_unmap = 1,
2097 .may_swap = 1,
2098 .no_demotion = 1,
2099 };
2100
2101 nr_reclaimed = shrink_folio_list(folio_list, pgdat, &sc, &dummy_stat, false);
2102 while (!list_empty(folio_list)) {
2103 folio = lru_to_folio(folio_list);
2104 list_del(&folio->lru);
2105 folio_putback_lru(folio);
2106 }
2107
2108 return nr_reclaimed;
2109}
2110
2111unsigned long reclaim_pages(struct list_head *folio_list)
2112{
2113 int nid;
2114 unsigned int nr_reclaimed = 0;
2115 LIST_HEAD(node_folio_list);
2116 unsigned int noreclaim_flag;
2117
2118 if (list_empty(folio_list))
2119 return nr_reclaimed;
2120
2121 noreclaim_flag = memalloc_noreclaim_save();
2122
2123 nid = folio_nid(lru_to_folio(folio_list));
2124 do {
2125 struct folio *folio = lru_to_folio(folio_list);
2126
2127 if (nid == folio_nid(folio)) {
2128 folio_clear_active(folio);
2129 list_move(&folio->lru, &node_folio_list);
2130 continue;
2131 }
2132
2133 nr_reclaimed += reclaim_folio_list(&node_folio_list, NODE_DATA(nid));
2134 nid = folio_nid(lru_to_folio(folio_list));
2135 } while (!list_empty(folio_list));
2136
2137 nr_reclaimed += reclaim_folio_list(&node_folio_list, NODE_DATA(nid));
2138
2139 memalloc_noreclaim_restore(noreclaim_flag);
2140
2141 return nr_reclaimed;
2142}
2143
2144static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
2145 struct lruvec *lruvec, struct scan_control *sc)
2146{
2147 if (is_active_lru(lru)) {
2148 if (sc->may_deactivate & (1 << is_file_lru(lru)))
2149 shrink_active_list(nr_to_scan, lruvec, sc, lru);
2150 else
2151 sc->skipped_deactivate = 1;
2152 return 0;
2153 }
2154
2155 return shrink_inactive_list(nr_to_scan, lruvec, sc, lru);
2156}
2157
2158/*
2159 * The inactive anon list should be small enough that the VM never has
2160 * to do too much work.
2161 *
2162 * The inactive file list should be small enough to leave most memory
2163 * to the established workingset on the scan-resistant active list,
2164 * but large enough to avoid thrashing the aggregate readahead window.
2165 *
2166 * Both inactive lists should also be large enough that each inactive
2167 * folio has a chance to be referenced again before it is reclaimed.
2168 *
2169 * If that fails and refaulting is observed, the inactive list grows.
2170 *
2171 * The inactive_ratio is the target ratio of ACTIVE to INACTIVE folios
2172 * on this LRU, maintained by the pageout code. An inactive_ratio
2173 * of 3 means 3:1 or 25% of the folios are kept on the inactive list.
2174 *
2175 * total target max
2176 * memory ratio inactive
2177 * -------------------------------------
2178 * 10MB 1 5MB
2179 * 100MB 1 50MB
2180 * 1GB 3 250MB
2181 * 10GB 10 0.9GB
2182 * 100GB 31 3GB
2183 * 1TB 101 10GB
2184 * 10TB 320 32GB
2185 */
2186static bool inactive_is_low(struct lruvec *lruvec, enum lru_list inactive_lru)
2187{
2188 enum lru_list active_lru = inactive_lru + LRU_ACTIVE;
2189 unsigned long inactive, active;
2190 unsigned long inactive_ratio;
2191 unsigned long gb;
2192
2193 inactive = lruvec_page_state(lruvec, NR_LRU_BASE + inactive_lru);
2194 active = lruvec_page_state(lruvec, NR_LRU_BASE + active_lru);
2195
2196 gb = (inactive + active) >> (30 - PAGE_SHIFT);
2197 if (gb)
2198 inactive_ratio = int_sqrt(10 * gb);
2199 else
2200 inactive_ratio = 1;
2201
2202 return inactive * inactive_ratio < active;
2203}
2204
2205enum scan_balance {
2206 SCAN_EQUAL,
2207 SCAN_FRACT,
2208 SCAN_ANON,
2209 SCAN_FILE,
2210};
2211
2212static void prepare_scan_control(pg_data_t *pgdat, struct scan_control *sc)
2213{
2214 unsigned long file;
2215 struct lruvec *target_lruvec;
2216
2217 if (lru_gen_enabled())
2218 return;
2219
2220 target_lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup, pgdat);
2221
2222 /*
2223 * Flush the memory cgroup stats, so that we read accurate per-memcg
2224 * lruvec stats for heuristics.
2225 */
2226 mem_cgroup_flush_stats(sc->target_mem_cgroup);
2227
2228 /*
2229 * Determine the scan balance between anon and file LRUs.
2230 */
2231 spin_lock_irq(&target_lruvec->lru_lock);
2232 sc->anon_cost = target_lruvec->anon_cost;
2233 sc->file_cost = target_lruvec->file_cost;
2234 spin_unlock_irq(&target_lruvec->lru_lock);
2235
2236 /*
2237 * Target desirable inactive:active list ratios for the anon
2238 * and file LRU lists.
2239 */
2240 if (!sc->force_deactivate) {
2241 unsigned long refaults;
2242
2243 /*
2244 * When refaults are being observed, it means a new
2245 * workingset is being established. Deactivate to get
2246 * rid of any stale active pages quickly.
2247 */
2248 refaults = lruvec_page_state(target_lruvec,
2249 WORKINGSET_ACTIVATE_ANON);
2250 if (refaults != target_lruvec->refaults[WORKINGSET_ANON] ||
2251 inactive_is_low(target_lruvec, LRU_INACTIVE_ANON))
2252 sc->may_deactivate |= DEACTIVATE_ANON;
2253 else
2254 sc->may_deactivate &= ~DEACTIVATE_ANON;
2255
2256 refaults = lruvec_page_state(target_lruvec,
2257 WORKINGSET_ACTIVATE_FILE);
2258 if (refaults != target_lruvec->refaults[WORKINGSET_FILE] ||
2259 inactive_is_low(target_lruvec, LRU_INACTIVE_FILE))
2260 sc->may_deactivate |= DEACTIVATE_FILE;
2261 else
2262 sc->may_deactivate &= ~DEACTIVATE_FILE;
2263 } else
2264 sc->may_deactivate = DEACTIVATE_ANON | DEACTIVATE_FILE;
2265
2266 /*
2267 * If we have plenty of inactive file pages that aren't
2268 * thrashing, try to reclaim those first before touching
2269 * anonymous pages.
2270 */
2271 file = lruvec_page_state(target_lruvec, NR_INACTIVE_FILE);
2272 if (file >> sc->priority && !(sc->may_deactivate & DEACTIVATE_FILE))
2273 sc->cache_trim_mode = 1;
2274 else
2275 sc->cache_trim_mode = 0;
2276
2277 /*
2278 * Prevent the reclaimer from falling into the cache trap: as
2279 * cache pages start out inactive, every cache fault will tip
2280 * the scan balance towards the file LRU. And as the file LRU
2281 * shrinks, so does the window for rotation from references.
2282 * This means we have a runaway feedback loop where a tiny
2283 * thrashing file LRU becomes infinitely more attractive than
2284 * anon pages. Try to detect this based on file LRU size.
2285 */
2286 if (!cgroup_reclaim(sc)) {
2287 unsigned long total_high_wmark = 0;
2288 unsigned long free, anon;
2289 int z;
2290
2291 free = sum_zone_node_page_state(pgdat->node_id, NR_FREE_PAGES);
2292 file = node_page_state(pgdat, NR_ACTIVE_FILE) +
2293 node_page_state(pgdat, NR_INACTIVE_FILE);
2294
2295 for (z = 0; z < MAX_NR_ZONES; z++) {
2296 struct zone *zone = &pgdat->node_zones[z];
2297
2298 if (!managed_zone(zone))
2299 continue;
2300
2301 total_high_wmark += high_wmark_pages(zone);
2302 }
2303
2304 /*
2305 * Consider anon: if that's low too, this isn't a
2306 * runaway file reclaim problem, but rather just
2307 * extreme pressure. Reclaim as per usual then.
2308 */
2309 anon = node_page_state(pgdat, NR_INACTIVE_ANON);
2310
2311 sc->file_is_tiny =
2312 file + free <= total_high_wmark &&
2313 !(sc->may_deactivate & DEACTIVATE_ANON) &&
2314 anon >> sc->priority;
2315 }
2316}
2317
2318/*
2319 * Determine how aggressively the anon and file LRU lists should be
2320 * scanned.
2321 *
2322 * nr[0] = anon inactive folios to scan; nr[1] = anon active folios to scan
2323 * nr[2] = file inactive folios to scan; nr[3] = file active folios to scan
2324 */
2325static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
2326 unsigned long *nr)
2327{
2328 struct pglist_data *pgdat = lruvec_pgdat(lruvec);
2329 struct mem_cgroup *memcg = lruvec_memcg(lruvec);
2330 unsigned long anon_cost, file_cost, total_cost;
2331 int swappiness = mem_cgroup_swappiness(memcg);
2332 u64 fraction[ANON_AND_FILE];
2333 u64 denominator = 0; /* gcc */
2334 enum scan_balance scan_balance;
2335 unsigned long ap, fp;
2336 enum lru_list lru;
2337
2338 /* If we have no swap space, do not bother scanning anon folios. */
2339 if (!sc->may_swap || !can_reclaim_anon_pages(memcg, pgdat->node_id, sc)) {
2340 scan_balance = SCAN_FILE;
2341 goto out;
2342 }
2343
2344 /*
2345 * Global reclaim will swap to prevent OOM even with no
2346 * swappiness, but memcg users want to use this knob to
2347 * disable swapping for individual groups completely when
2348 * using the memory controller's swap limit feature would be
2349 * too expensive.
2350 */
2351 if (cgroup_reclaim(sc) && !swappiness) {
2352 scan_balance = SCAN_FILE;
2353 goto out;
2354 }
2355
2356 /*
2357 * Do not apply any pressure balancing cleverness when the
2358 * system is close to OOM, scan both anon and file equally
2359 * (unless the swappiness setting disagrees with swapping).
2360 */
2361 if (!sc->priority && swappiness) {
2362 scan_balance = SCAN_EQUAL;
2363 goto out;
2364 }
2365
2366 /*
2367 * If the system is almost out of file pages, force-scan anon.
2368 */
2369 if (sc->file_is_tiny) {
2370 scan_balance = SCAN_ANON;
2371 goto out;
2372 }
2373
2374 /*
2375 * If there is enough inactive page cache, we do not reclaim
2376 * anything from the anonymous working right now.
2377 */
2378 if (sc->cache_trim_mode) {
2379 scan_balance = SCAN_FILE;
2380 goto out;
2381 }
2382
2383 scan_balance = SCAN_FRACT;
2384 /*
2385 * Calculate the pressure balance between anon and file pages.
2386 *
2387 * The amount of pressure we put on each LRU is inversely
2388 * proportional to the cost of reclaiming each list, as
2389 * determined by the share of pages that are refaulting, times
2390 * the relative IO cost of bringing back a swapped out
2391 * anonymous page vs reloading a filesystem page (swappiness).
2392 *
2393 * Although we limit that influence to ensure no list gets
2394 * left behind completely: at least a third of the pressure is
2395 * applied, before swappiness.
2396 *
2397 * With swappiness at 100, anon and file have equal IO cost.
2398 */
2399 total_cost = sc->anon_cost + sc->file_cost;
2400 anon_cost = total_cost + sc->anon_cost;
2401 file_cost = total_cost + sc->file_cost;
2402 total_cost = anon_cost + file_cost;
2403
2404 ap = swappiness * (total_cost + 1);
2405 ap /= anon_cost + 1;
2406
2407 fp = (200 - swappiness) * (total_cost + 1);
2408 fp /= file_cost + 1;
2409
2410 fraction[0] = ap;
2411 fraction[1] = fp;
2412 denominator = ap + fp;
2413out:
2414 for_each_evictable_lru(lru) {
2415 int file = is_file_lru(lru);
2416 unsigned long lruvec_size;
2417 unsigned long low, min;
2418 unsigned long scan;
2419
2420 lruvec_size = lruvec_lru_size(lruvec, lru, sc->reclaim_idx);
2421 mem_cgroup_protection(sc->target_mem_cgroup, memcg,
2422 &min, &low);
2423
2424 if (min || low) {
2425 /*
2426 * Scale a cgroup's reclaim pressure by proportioning
2427 * its current usage to its memory.low or memory.min
2428 * setting.
2429 *
2430 * This is important, as otherwise scanning aggression
2431 * becomes extremely binary -- from nothing as we
2432 * approach the memory protection threshold, to totally
2433 * nominal as we exceed it. This results in requiring
2434 * setting extremely liberal protection thresholds. It
2435 * also means we simply get no protection at all if we
2436 * set it too low, which is not ideal.
2437 *
2438 * If there is any protection in place, we reduce scan
2439 * pressure by how much of the total memory used is
2440 * within protection thresholds.
2441 *
2442 * There is one special case: in the first reclaim pass,
2443 * we skip over all groups that are within their low
2444 * protection. If that fails to reclaim enough pages to
2445 * satisfy the reclaim goal, we come back and override
2446 * the best-effort low protection. However, we still
2447 * ideally want to honor how well-behaved groups are in
2448 * that case instead of simply punishing them all
2449 * equally. As such, we reclaim them based on how much
2450 * memory they are using, reducing the scan pressure
2451 * again by how much of the total memory used is under
2452 * hard protection.
2453 */
2454 unsigned long cgroup_size = mem_cgroup_size(memcg);
2455 unsigned long protection;
2456
2457 /* memory.low scaling, make sure we retry before OOM */
2458 if (!sc->memcg_low_reclaim && low > min) {
2459 protection = low;
2460 sc->memcg_low_skipped = 1;
2461 } else {
2462 protection = min;
2463 }
2464
2465 /* Avoid TOCTOU with earlier protection check */
2466 cgroup_size = max(cgroup_size, protection);
2467
2468 scan = lruvec_size - lruvec_size * protection /
2469 (cgroup_size + 1);
2470
2471 /*
2472 * Minimally target SWAP_CLUSTER_MAX pages to keep
2473 * reclaim moving forwards, avoiding decrementing
2474 * sc->priority further than desirable.
2475 */
2476 scan = max(scan, SWAP_CLUSTER_MAX);
2477 } else {
2478 scan = lruvec_size;
2479 }
2480
2481 scan >>= sc->priority;
2482
2483 /*
2484 * If the cgroup's already been deleted, make sure to
2485 * scrape out the remaining cache.
2486 */
2487 if (!scan && !mem_cgroup_online(memcg))
2488 scan = min(lruvec_size, SWAP_CLUSTER_MAX);
2489
2490 switch (scan_balance) {
2491 case SCAN_EQUAL:
2492 /* Scan lists relative to size */
2493 break;
2494 case SCAN_FRACT:
2495 /*
2496 * Scan types proportional to swappiness and
2497 * their relative recent reclaim efficiency.
2498 * Make sure we don't miss the last page on
2499 * the offlined memory cgroups because of a
2500 * round-off error.
2501 */
2502 scan = mem_cgroup_online(memcg) ?
2503 div64_u64(scan * fraction[file], denominator) :
2504 DIV64_U64_ROUND_UP(scan * fraction[file],
2505 denominator);
2506 break;
2507 case SCAN_FILE:
2508 case SCAN_ANON:
2509 /* Scan one type exclusively */
2510 if ((scan_balance == SCAN_FILE) != file)
2511 scan = 0;
2512 break;
2513 default:
2514 /* Look ma, no brain */
2515 BUG();
2516 }
2517
2518 nr[lru] = scan;
2519 }
2520}
2521
2522/*
2523 * Anonymous LRU management is a waste if there is
2524 * ultimately no way to reclaim the memory.
2525 */
2526static bool can_age_anon_pages(struct pglist_data *pgdat,
2527 struct scan_control *sc)
2528{
2529 /* Aging the anon LRU is valuable if swap is present: */
2530 if (total_swap_pages > 0)
2531 return true;
2532
2533 /* Also valuable if anon pages can be demoted: */
2534 return can_demote(pgdat->node_id, sc);
2535}
2536
2537#ifdef CONFIG_LRU_GEN
2538
2539#ifdef CONFIG_LRU_GEN_ENABLED
2540DEFINE_STATIC_KEY_ARRAY_TRUE(lru_gen_caps, NR_LRU_GEN_CAPS);
2541#define get_cap(cap) static_branch_likely(&lru_gen_caps[cap])
2542#else
2543DEFINE_STATIC_KEY_ARRAY_FALSE(lru_gen_caps, NR_LRU_GEN_CAPS);
2544#define get_cap(cap) static_branch_unlikely(&lru_gen_caps[cap])
2545#endif
2546
2547static bool should_walk_mmu(void)
2548{
2549 return arch_has_hw_pte_young() && get_cap(LRU_GEN_MM_WALK);
2550}
2551
2552static bool should_clear_pmd_young(void)
2553{
2554 return arch_has_hw_nonleaf_pmd_young() && get_cap(LRU_GEN_NONLEAF_YOUNG);
2555}
2556
2557/******************************************************************************
2558 * shorthand helpers
2559 ******************************************************************************/
2560
2561#define LRU_REFS_FLAGS (BIT(PG_referenced) | BIT(PG_workingset))
2562
2563#define DEFINE_MAX_SEQ(lruvec) \
2564 unsigned long max_seq = READ_ONCE((lruvec)->lrugen.max_seq)
2565
2566#define DEFINE_MIN_SEQ(lruvec) \
2567 unsigned long min_seq[ANON_AND_FILE] = { \
2568 READ_ONCE((lruvec)->lrugen.min_seq[LRU_GEN_ANON]), \
2569 READ_ONCE((lruvec)->lrugen.min_seq[LRU_GEN_FILE]), \
2570 }
2571
2572#define for_each_gen_type_zone(gen, type, zone) \
2573 for ((gen) = 0; (gen) < MAX_NR_GENS; (gen)++) \
2574 for ((type) = 0; (type) < ANON_AND_FILE; (type)++) \
2575 for ((zone) = 0; (zone) < MAX_NR_ZONES; (zone)++)
2576
2577#define get_memcg_gen(seq) ((seq) % MEMCG_NR_GENS)
2578#define get_memcg_bin(bin) ((bin) % MEMCG_NR_BINS)
2579
2580static struct lruvec *get_lruvec(struct mem_cgroup *memcg, int nid)
2581{
2582 struct pglist_data *pgdat = NODE_DATA(nid);
2583
2584#ifdef CONFIG_MEMCG
2585 if (memcg) {
2586 struct lruvec *lruvec = &memcg->nodeinfo[nid]->lruvec;
2587
2588 /* see the comment in mem_cgroup_lruvec() */
2589 if (!lruvec->pgdat)
2590 lruvec->pgdat = pgdat;
2591
2592 return lruvec;
2593 }
2594#endif
2595 VM_WARN_ON_ONCE(!mem_cgroup_disabled());
2596
2597 return &pgdat->__lruvec;
2598}
2599
2600static int get_swappiness(struct lruvec *lruvec, struct scan_control *sc)
2601{
2602 struct mem_cgroup *memcg = lruvec_memcg(lruvec);
2603 struct pglist_data *pgdat = lruvec_pgdat(lruvec);
2604
2605 if (!sc->may_swap)
2606 return 0;
2607
2608 if (!can_demote(pgdat->node_id, sc) &&
2609 mem_cgroup_get_nr_swap_pages(memcg) < MIN_LRU_BATCH)
2610 return 0;
2611
2612 return mem_cgroup_swappiness(memcg);
2613}
2614
2615static int get_nr_gens(struct lruvec *lruvec, int type)
2616{
2617 return lruvec->lrugen.max_seq - lruvec->lrugen.min_seq[type] + 1;
2618}
2619
2620static bool __maybe_unused seq_is_valid(struct lruvec *lruvec)
2621{
2622 /* see the comment on lru_gen_folio */
2623 return get_nr_gens(lruvec, LRU_GEN_FILE) >= MIN_NR_GENS &&
2624 get_nr_gens(lruvec, LRU_GEN_FILE) <= get_nr_gens(lruvec, LRU_GEN_ANON) &&
2625 get_nr_gens(lruvec, LRU_GEN_ANON) <= MAX_NR_GENS;
2626}
2627
2628/******************************************************************************
2629 * Bloom filters
2630 ******************************************************************************/
2631
2632/*
2633 * Bloom filters with m=1<<15, k=2 and the false positive rates of ~1/5 when
2634 * n=10,000 and ~1/2 when n=20,000, where, conventionally, m is the number of
2635 * bits in a bitmap, k is the number of hash functions and n is the number of
2636 * inserted items.
2637 *
2638 * Page table walkers use one of the two filters to reduce their search space.
2639 * To get rid of non-leaf entries that no longer have enough leaf entries, the
2640 * aging uses the double-buffering technique to flip to the other filter each
2641 * time it produces a new generation. For non-leaf entries that have enough
2642 * leaf entries, the aging carries them over to the next generation in
2643 * walk_pmd_range(); the eviction also report them when walking the rmap
2644 * in lru_gen_look_around().
2645 *
2646 * For future optimizations:
2647 * 1. It's not necessary to keep both filters all the time. The spare one can be
2648 * freed after the RCU grace period and reallocated if needed again.
2649 * 2. And when reallocating, it's worth scaling its size according to the number
2650 * of inserted entries in the other filter, to reduce the memory overhead on
2651 * small systems and false positives on large systems.
2652 * 3. Jenkins' hash function is an alternative to Knuth's.
2653 */
2654#define BLOOM_FILTER_SHIFT 15
2655
2656static inline int filter_gen_from_seq(unsigned long seq)
2657{
2658 return seq % NR_BLOOM_FILTERS;
2659}
2660
2661static void get_item_key(void *item, int *key)
2662{
2663 u32 hash = hash_ptr(item, BLOOM_FILTER_SHIFT * 2);
2664
2665 BUILD_BUG_ON(BLOOM_FILTER_SHIFT * 2 > BITS_PER_TYPE(u32));
2666
2667 key[0] = hash & (BIT(BLOOM_FILTER_SHIFT) - 1);
2668 key[1] = hash >> BLOOM_FILTER_SHIFT;
2669}
2670
2671static bool test_bloom_filter(struct lru_gen_mm_state *mm_state, unsigned long seq,
2672 void *item)
2673{
2674 int key[2];
2675 unsigned long *filter;
2676 int gen = filter_gen_from_seq(seq);
2677
2678 filter = READ_ONCE(mm_state->filters[gen]);
2679 if (!filter)
2680 return true;
2681
2682 get_item_key(item, key);
2683
2684 return test_bit(key[0], filter) && test_bit(key[1], filter);
2685}
2686
2687static void update_bloom_filter(struct lru_gen_mm_state *mm_state, unsigned long seq,
2688 void *item)
2689{
2690 int key[2];
2691 unsigned long *filter;
2692 int gen = filter_gen_from_seq(seq);
2693
2694 filter = READ_ONCE(mm_state->filters[gen]);
2695 if (!filter)
2696 return;
2697
2698 get_item_key(item, key);
2699
2700 if (!test_bit(key[0], filter))
2701 set_bit(key[0], filter);
2702 if (!test_bit(key[1], filter))
2703 set_bit(key[1], filter);
2704}
2705
2706static void reset_bloom_filter(struct lru_gen_mm_state *mm_state, unsigned long seq)
2707{
2708 unsigned long *filter;
2709 int gen = filter_gen_from_seq(seq);
2710
2711 filter = mm_state->filters[gen];
2712 if (filter) {
2713 bitmap_clear(filter, 0, BIT(BLOOM_FILTER_SHIFT));
2714 return;
2715 }
2716
2717 filter = bitmap_zalloc(BIT(BLOOM_FILTER_SHIFT),
2718 __GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN);
2719 WRITE_ONCE(mm_state->filters[gen], filter);
2720}
2721
2722/******************************************************************************
2723 * mm_struct list
2724 ******************************************************************************/
2725
2726#ifdef CONFIG_LRU_GEN_WALKS_MMU
2727
2728static struct lru_gen_mm_list *get_mm_list(struct mem_cgroup *memcg)
2729{
2730 static struct lru_gen_mm_list mm_list = {
2731 .fifo = LIST_HEAD_INIT(mm_list.fifo),
2732 .lock = __SPIN_LOCK_UNLOCKED(mm_list.lock),
2733 };
2734
2735#ifdef CONFIG_MEMCG
2736 if (memcg)
2737 return &memcg->mm_list;
2738#endif
2739 VM_WARN_ON_ONCE(!mem_cgroup_disabled());
2740
2741 return &mm_list;
2742}
2743
2744static struct lru_gen_mm_state *get_mm_state(struct lruvec *lruvec)
2745{
2746 return &lruvec->mm_state;
2747}
2748
2749static struct mm_struct *get_next_mm(struct lru_gen_mm_walk *walk)
2750{
2751 int key;
2752 struct mm_struct *mm;
2753 struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);
2754 struct lru_gen_mm_state *mm_state = get_mm_state(walk->lruvec);
2755
2756 mm = list_entry(mm_state->head, struct mm_struct, lru_gen.list);
2757 key = pgdat->node_id % BITS_PER_TYPE(mm->lru_gen.bitmap);
2758
2759 if (!walk->force_scan && !test_bit(key, &mm->lru_gen.bitmap))
2760 return NULL;
2761
2762 clear_bit(key, &mm->lru_gen.bitmap);
2763
2764 return mmget_not_zero(mm) ? mm : NULL;
2765}
2766
2767void lru_gen_add_mm(struct mm_struct *mm)
2768{
2769 int nid;
2770 struct mem_cgroup *memcg = get_mem_cgroup_from_mm(mm);
2771 struct lru_gen_mm_list *mm_list = get_mm_list(memcg);
2772
2773 VM_WARN_ON_ONCE(!list_empty(&mm->lru_gen.list));
2774#ifdef CONFIG_MEMCG
2775 VM_WARN_ON_ONCE(mm->lru_gen.memcg);
2776 mm->lru_gen.memcg = memcg;
2777#endif
2778 spin_lock(&mm_list->lock);
2779
2780 for_each_node_state(nid, N_MEMORY) {
2781 struct lruvec *lruvec = get_lruvec(memcg, nid);
2782 struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
2783
2784 /* the first addition since the last iteration */
2785 if (mm_state->tail == &mm_list->fifo)
2786 mm_state->tail = &mm->lru_gen.list;
2787 }
2788
2789 list_add_tail(&mm->lru_gen.list, &mm_list->fifo);
2790
2791 spin_unlock(&mm_list->lock);
2792}
2793
2794void lru_gen_del_mm(struct mm_struct *mm)
2795{
2796 int nid;
2797 struct lru_gen_mm_list *mm_list;
2798 struct mem_cgroup *memcg = NULL;
2799
2800 if (list_empty(&mm->lru_gen.list))
2801 return;
2802
2803#ifdef CONFIG_MEMCG
2804 memcg = mm->lru_gen.memcg;
2805#endif
2806 mm_list = get_mm_list(memcg);
2807
2808 spin_lock(&mm_list->lock);
2809
2810 for_each_node(nid) {
2811 struct lruvec *lruvec = get_lruvec(memcg, nid);
2812 struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
2813
2814 /* where the current iteration continues after */
2815 if (mm_state->head == &mm->lru_gen.list)
2816 mm_state->head = mm_state->head->prev;
2817
2818 /* where the last iteration ended before */
2819 if (mm_state->tail == &mm->lru_gen.list)
2820 mm_state->tail = mm_state->tail->next;
2821 }
2822
2823 list_del_init(&mm->lru_gen.list);
2824
2825 spin_unlock(&mm_list->lock);
2826
2827#ifdef CONFIG_MEMCG
2828 mem_cgroup_put(mm->lru_gen.memcg);
2829 mm->lru_gen.memcg = NULL;
2830#endif
2831}
2832
2833#ifdef CONFIG_MEMCG
2834void lru_gen_migrate_mm(struct mm_struct *mm)
2835{
2836 struct mem_cgroup *memcg;
2837 struct task_struct *task = rcu_dereference_protected(mm->owner, true);
2838
2839 VM_WARN_ON_ONCE(task->mm != mm);
2840 lockdep_assert_held(&task->alloc_lock);
2841
2842 /* for mm_update_next_owner() */
2843 if (mem_cgroup_disabled())
2844 return;
2845
2846 /* migration can happen before addition */
2847 if (!mm->lru_gen.memcg)
2848 return;
2849
2850 rcu_read_lock();
2851 memcg = mem_cgroup_from_task(task);
2852 rcu_read_unlock();
2853 if (memcg == mm->lru_gen.memcg)
2854 return;
2855
2856 VM_WARN_ON_ONCE(list_empty(&mm->lru_gen.list));
2857
2858 lru_gen_del_mm(mm);
2859 lru_gen_add_mm(mm);
2860}
2861#endif
2862
2863#else /* !CONFIG_LRU_GEN_WALKS_MMU */
2864
2865static struct lru_gen_mm_list *get_mm_list(struct mem_cgroup *memcg)
2866{
2867 return NULL;
2868}
2869
2870static struct lru_gen_mm_state *get_mm_state(struct lruvec *lruvec)
2871{
2872 return NULL;
2873}
2874
2875static struct mm_struct *get_next_mm(struct lru_gen_mm_walk *walk)
2876{
2877 return NULL;
2878}
2879
2880#endif
2881
2882static void reset_mm_stats(struct lruvec *lruvec, struct lru_gen_mm_walk *walk, bool last)
2883{
2884 int i;
2885 int hist;
2886 struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
2887
2888 lockdep_assert_held(&get_mm_list(lruvec_memcg(lruvec))->lock);
2889
2890 if (walk) {
2891 hist = lru_hist_from_seq(walk->max_seq);
2892
2893 for (i = 0; i < NR_MM_STATS; i++) {
2894 WRITE_ONCE(mm_state->stats[hist][i],
2895 mm_state->stats[hist][i] + walk->mm_stats[i]);
2896 walk->mm_stats[i] = 0;
2897 }
2898 }
2899
2900 if (NR_HIST_GENS > 1 && last) {
2901 hist = lru_hist_from_seq(mm_state->seq + 1);
2902
2903 for (i = 0; i < NR_MM_STATS; i++)
2904 WRITE_ONCE(mm_state->stats[hist][i], 0);
2905 }
2906}
2907
2908static bool iterate_mm_list(struct lruvec *lruvec, struct lru_gen_mm_walk *walk,
2909 struct mm_struct **iter)
2910{
2911 bool first = false;
2912 bool last = false;
2913 struct mm_struct *mm = NULL;
2914 struct mem_cgroup *memcg = lruvec_memcg(lruvec);
2915 struct lru_gen_mm_list *mm_list = get_mm_list(memcg);
2916 struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
2917
2918 /*
2919 * mm_state->seq is incremented after each iteration of mm_list. There
2920 * are three interesting cases for this page table walker:
2921 * 1. It tries to start a new iteration with a stale max_seq: there is
2922 * nothing left to do.
2923 * 2. It started the next iteration: it needs to reset the Bloom filter
2924 * so that a fresh set of PTE tables can be recorded.
2925 * 3. It ended the current iteration: it needs to reset the mm stats
2926 * counters and tell its caller to increment max_seq.
2927 */
2928 spin_lock(&mm_list->lock);
2929
2930 VM_WARN_ON_ONCE(mm_state->seq + 1 < walk->max_seq);
2931
2932 if (walk->max_seq <= mm_state->seq)
2933 goto done;
2934
2935 if (!mm_state->head)
2936 mm_state->head = &mm_list->fifo;
2937
2938 if (mm_state->head == &mm_list->fifo)
2939 first = true;
2940
2941 do {
2942 mm_state->head = mm_state->head->next;
2943 if (mm_state->head == &mm_list->fifo) {
2944 WRITE_ONCE(mm_state->seq, mm_state->seq + 1);
2945 last = true;
2946 break;
2947 }
2948
2949 /* force scan for those added after the last iteration */
2950 if (!mm_state->tail || mm_state->tail == mm_state->head) {
2951 mm_state->tail = mm_state->head->next;
2952 walk->force_scan = true;
2953 }
2954 } while (!(mm = get_next_mm(walk)));
2955done:
2956 if (*iter || last)
2957 reset_mm_stats(lruvec, walk, last);
2958
2959 spin_unlock(&mm_list->lock);
2960
2961 if (mm && first)
2962 reset_bloom_filter(mm_state, walk->max_seq + 1);
2963
2964 if (*iter)
2965 mmput_async(*iter);
2966
2967 *iter = mm;
2968
2969 return last;
2970}
2971
2972static bool iterate_mm_list_nowalk(struct lruvec *lruvec, unsigned long max_seq)
2973{
2974 bool success = false;
2975 struct mem_cgroup *memcg = lruvec_memcg(lruvec);
2976 struct lru_gen_mm_list *mm_list = get_mm_list(memcg);
2977 struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
2978
2979 spin_lock(&mm_list->lock);
2980
2981 VM_WARN_ON_ONCE(mm_state->seq + 1 < max_seq);
2982
2983 if (max_seq > mm_state->seq) {
2984 mm_state->head = NULL;
2985 mm_state->tail = NULL;
2986 WRITE_ONCE(mm_state->seq, mm_state->seq + 1);
2987 reset_mm_stats(lruvec, NULL, true);
2988 success = true;
2989 }
2990
2991 spin_unlock(&mm_list->lock);
2992
2993 return success;
2994}
2995
2996/******************************************************************************
2997 * PID controller
2998 ******************************************************************************/
2999
3000/*
3001 * A feedback loop based on Proportional-Integral-Derivative (PID) controller.
3002 *
3003 * The P term is refaulted/(evicted+protected) from a tier in the generation
3004 * currently being evicted; the I term is the exponential moving average of the
3005 * P term over the generations previously evicted, using the smoothing factor
3006 * 1/2; the D term isn't supported.
3007 *
3008 * The setpoint (SP) is always the first tier of one type; the process variable
3009 * (PV) is either any tier of the other type or any other tier of the same
3010 * type.
3011 *
3012 * The error is the difference between the SP and the PV; the correction is to
3013 * turn off protection when SP>PV or turn on protection when SP<PV.
3014 *
3015 * For future optimizations:
3016 * 1. The D term may discount the other two terms over time so that long-lived
3017 * generations can resist stale information.
3018 */
3019struct ctrl_pos {
3020 unsigned long refaulted;
3021 unsigned long total;
3022 int gain;
3023};
3024
3025static void read_ctrl_pos(struct lruvec *lruvec, int type, int tier, int gain,
3026 struct ctrl_pos *pos)
3027{
3028 struct lru_gen_folio *lrugen = &lruvec->lrugen;
3029 int hist = lru_hist_from_seq(lrugen->min_seq[type]);
3030
3031 pos->refaulted = lrugen->avg_refaulted[type][tier] +
3032 atomic_long_read(&lrugen->refaulted[hist][type][tier]);
3033 pos->total = lrugen->avg_total[type][tier] +
3034 atomic_long_read(&lrugen->evicted[hist][type][tier]);
3035 if (tier)
3036 pos->total += lrugen->protected[hist][type][tier - 1];
3037 pos->gain = gain;
3038}
3039
3040static void reset_ctrl_pos(struct lruvec *lruvec, int type, bool carryover)
3041{
3042 int hist, tier;
3043 struct lru_gen_folio *lrugen = &lruvec->lrugen;
3044 bool clear = carryover ? NR_HIST_GENS == 1 : NR_HIST_GENS > 1;
3045 unsigned long seq = carryover ? lrugen->min_seq[type] : lrugen->max_seq + 1;
3046
3047 lockdep_assert_held(&lruvec->lru_lock);
3048
3049 if (!carryover && !clear)
3050 return;
3051
3052 hist = lru_hist_from_seq(seq);
3053
3054 for (tier = 0; tier < MAX_NR_TIERS; tier++) {
3055 if (carryover) {
3056 unsigned long sum;
3057
3058 sum = lrugen->avg_refaulted[type][tier] +
3059 atomic_long_read(&lrugen->refaulted[hist][type][tier]);
3060 WRITE_ONCE(lrugen->avg_refaulted[type][tier], sum / 2);
3061
3062 sum = lrugen->avg_total[type][tier] +
3063 atomic_long_read(&lrugen->evicted[hist][type][tier]);
3064 if (tier)
3065 sum += lrugen->protected[hist][type][tier - 1];
3066 WRITE_ONCE(lrugen->avg_total[type][tier], sum / 2);
3067 }
3068
3069 if (clear) {
3070 atomic_long_set(&lrugen->refaulted[hist][type][tier], 0);
3071 atomic_long_set(&lrugen->evicted[hist][type][tier], 0);
3072 if (tier)
3073 WRITE_ONCE(lrugen->protected[hist][type][tier - 1], 0);
3074 }
3075 }
3076}
3077
3078static bool positive_ctrl_err(struct ctrl_pos *sp, struct ctrl_pos *pv)
3079{
3080 /*
3081 * Return true if the PV has a limited number of refaults or a lower
3082 * refaulted/total than the SP.
3083 */
3084 return pv->refaulted < MIN_LRU_BATCH ||
3085 pv->refaulted * (sp->total + MIN_LRU_BATCH) * sp->gain <=
3086 (sp->refaulted + 1) * pv->total * pv->gain;
3087}
3088
3089/******************************************************************************
3090 * the aging
3091 ******************************************************************************/
3092
3093/* promote pages accessed through page tables */
3094static int folio_update_gen(struct folio *folio, int gen)
3095{
3096 unsigned long new_flags, old_flags = READ_ONCE(folio->flags);
3097
3098 VM_WARN_ON_ONCE(gen >= MAX_NR_GENS);
3099 VM_WARN_ON_ONCE(!rcu_read_lock_held());
3100
3101 do {
3102 /* lru_gen_del_folio() has isolated this page? */
3103 if (!(old_flags & LRU_GEN_MASK)) {
3104 /* for shrink_folio_list() */
3105 new_flags = old_flags | BIT(PG_referenced);
3106 continue;
3107 }
3108
3109 new_flags = old_flags & ~(LRU_GEN_MASK | LRU_REFS_MASK | LRU_REFS_FLAGS);
3110 new_flags |= (gen + 1UL) << LRU_GEN_PGOFF;
3111 } while (!try_cmpxchg(&folio->flags, &old_flags, new_flags));
3112
3113 return ((old_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1;
3114}
3115
3116/* protect pages accessed multiple times through file descriptors */
3117static int folio_inc_gen(struct lruvec *lruvec, struct folio *folio, bool reclaiming)
3118{
3119 int type = folio_is_file_lru(folio);
3120 struct lru_gen_folio *lrugen = &lruvec->lrugen;
3121 int new_gen, old_gen = lru_gen_from_seq(lrugen->min_seq[type]);
3122 unsigned long new_flags, old_flags = READ_ONCE(folio->flags);
3123
3124 VM_WARN_ON_ONCE_FOLIO(!(old_flags & LRU_GEN_MASK), folio);
3125
3126 do {
3127 new_gen = ((old_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1;
3128 /* folio_update_gen() has promoted this page? */
3129 if (new_gen >= 0 && new_gen != old_gen)
3130 return new_gen;
3131
3132 new_gen = (old_gen + 1) % MAX_NR_GENS;
3133
3134 new_flags = old_flags & ~(LRU_GEN_MASK | LRU_REFS_MASK | LRU_REFS_FLAGS);
3135 new_flags |= (new_gen + 1UL) << LRU_GEN_PGOFF;
3136 /* for folio_end_writeback() */
3137 if (reclaiming)
3138 new_flags |= BIT(PG_reclaim);
3139 } while (!try_cmpxchg(&folio->flags, &old_flags, new_flags));
3140
3141 lru_gen_update_size(lruvec, folio, old_gen, new_gen);
3142
3143 return new_gen;
3144}
3145
3146static void update_batch_size(struct lru_gen_mm_walk *walk, struct folio *folio,
3147 int old_gen, int new_gen)
3148{
3149 int type = folio_is_file_lru(folio);
3150 int zone = folio_zonenum(folio);
3151 int delta = folio_nr_pages(folio);
3152
3153 VM_WARN_ON_ONCE(old_gen >= MAX_NR_GENS);
3154 VM_WARN_ON_ONCE(new_gen >= MAX_NR_GENS);
3155
3156 walk->batched++;
3157
3158 walk->nr_pages[old_gen][type][zone] -= delta;
3159 walk->nr_pages[new_gen][type][zone] += delta;
3160}
3161
3162static void reset_batch_size(struct lruvec *lruvec, struct lru_gen_mm_walk *walk)
3163{
3164 int gen, type, zone;
3165 struct lru_gen_folio *lrugen = &lruvec->lrugen;
3166
3167 walk->batched = 0;
3168
3169 for_each_gen_type_zone(gen, type, zone) {
3170 enum lru_list lru = type * LRU_INACTIVE_FILE;
3171 int delta = walk->nr_pages[gen][type][zone];
3172
3173 if (!delta)
3174 continue;
3175
3176 walk->nr_pages[gen][type][zone] = 0;
3177 WRITE_ONCE(lrugen->nr_pages[gen][type][zone],
3178 lrugen->nr_pages[gen][type][zone] + delta);
3179
3180 if (lru_gen_is_active(lruvec, gen))
3181 lru += LRU_ACTIVE;
3182 __update_lru_size(lruvec, lru, zone, delta);
3183 }
3184}
3185
3186static int should_skip_vma(unsigned long start, unsigned long end, struct mm_walk *args)
3187{
3188 struct address_space *mapping;
3189 struct vm_area_struct *vma = args->vma;
3190 struct lru_gen_mm_walk *walk = args->private;
3191
3192 if (!vma_is_accessible(vma))
3193 return true;
3194
3195 if (is_vm_hugetlb_page(vma))
3196 return true;
3197
3198 if (!vma_has_recency(vma))
3199 return true;
3200
3201 if (vma->vm_flags & (VM_LOCKED | VM_SPECIAL))
3202 return true;
3203
3204 if (vma == get_gate_vma(vma->vm_mm))
3205 return true;
3206
3207 if (vma_is_anonymous(vma))
3208 return !walk->can_swap;
3209
3210 if (WARN_ON_ONCE(!vma->vm_file || !vma->vm_file->f_mapping))
3211 return true;
3212
3213 mapping = vma->vm_file->f_mapping;
3214 if (mapping_unevictable(mapping))
3215 return true;
3216
3217 if (shmem_mapping(mapping))
3218 return !walk->can_swap;
3219
3220 /* to exclude special mappings like dax, etc. */
3221 return !mapping->a_ops->read_folio;
3222}
3223
3224/*
3225 * Some userspace memory allocators map many single-page VMAs. Instead of
3226 * returning back to the PGD table for each of such VMAs, finish an entire PMD
3227 * table to reduce zigzags and improve cache performance.
3228 */
3229static bool get_next_vma(unsigned long mask, unsigned long size, struct mm_walk *args,
3230 unsigned long *vm_start, unsigned long *vm_end)
3231{
3232 unsigned long start = round_up(*vm_end, size);
3233 unsigned long end = (start | ~mask) + 1;
3234 VMA_ITERATOR(vmi, args->mm, start);
3235
3236 VM_WARN_ON_ONCE(mask & size);
3237 VM_WARN_ON_ONCE((start & mask) != (*vm_start & mask));
3238
3239 for_each_vma(vmi, args->vma) {
3240 if (end && end <= args->vma->vm_start)
3241 return false;
3242
3243 if (should_skip_vma(args->vma->vm_start, args->vma->vm_end, args))
3244 continue;
3245
3246 *vm_start = max(start, args->vma->vm_start);
3247 *vm_end = min(end - 1, args->vma->vm_end - 1) + 1;
3248
3249 return true;
3250 }
3251
3252 return false;
3253}
3254
3255static unsigned long get_pte_pfn(pte_t pte, struct vm_area_struct *vma, unsigned long addr)
3256{
3257 unsigned long pfn = pte_pfn(pte);
3258
3259 VM_WARN_ON_ONCE(addr < vma->vm_start || addr >= vma->vm_end);
3260
3261 if (!pte_present(pte) || is_zero_pfn(pfn))
3262 return -1;
3263
3264 if (WARN_ON_ONCE(pte_devmap(pte) || pte_special(pte)))
3265 return -1;
3266
3267 if (WARN_ON_ONCE(!pfn_valid(pfn)))
3268 return -1;
3269
3270 return pfn;
3271}
3272
3273static unsigned long get_pmd_pfn(pmd_t pmd, struct vm_area_struct *vma, unsigned long addr)
3274{
3275 unsigned long pfn = pmd_pfn(pmd);
3276
3277 VM_WARN_ON_ONCE(addr < vma->vm_start || addr >= vma->vm_end);
3278
3279 if (!pmd_present(pmd) || is_huge_zero_pmd(pmd))
3280 return -1;
3281
3282 if (WARN_ON_ONCE(pmd_devmap(pmd)))
3283 return -1;
3284
3285 if (WARN_ON_ONCE(!pfn_valid(pfn)))
3286 return -1;
3287
3288 return pfn;
3289}
3290
3291static struct folio *get_pfn_folio(unsigned long pfn, struct mem_cgroup *memcg,
3292 struct pglist_data *pgdat, bool can_swap)
3293{
3294 struct folio *folio;
3295
3296 /* try to avoid unnecessary memory loads */
3297 if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat))
3298 return NULL;
3299
3300 folio = pfn_folio(pfn);
3301 if (folio_nid(folio) != pgdat->node_id)
3302 return NULL;
3303
3304 if (folio_memcg_rcu(folio) != memcg)
3305 return NULL;
3306
3307 /* file VMAs can contain anon pages from COW */
3308 if (!folio_is_file_lru(folio) && !can_swap)
3309 return NULL;
3310
3311 return folio;
3312}
3313
3314static bool suitable_to_scan(int total, int young)
3315{
3316 int n = clamp_t(int, cache_line_size() / sizeof(pte_t), 2, 8);
3317
3318 /* suitable if the average number of young PTEs per cacheline is >=1 */
3319 return young * n >= total;
3320}
3321
3322static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end,
3323 struct mm_walk *args)
3324{
3325 int i;
3326 pte_t *pte;
3327 spinlock_t *ptl;
3328 unsigned long addr;
3329 int total = 0;
3330 int young = 0;
3331 struct lru_gen_mm_walk *walk = args->private;
3332 struct mem_cgroup *memcg = lruvec_memcg(walk->lruvec);
3333 struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);
3334 int old_gen, new_gen = lru_gen_from_seq(walk->max_seq);
3335
3336 pte = pte_offset_map_nolock(args->mm, pmd, start & PMD_MASK, &ptl);
3337 if (!pte)
3338 return false;
3339 if (!spin_trylock(ptl)) {
3340 pte_unmap(pte);
3341 return false;
3342 }
3343
3344 arch_enter_lazy_mmu_mode();
3345restart:
3346 for (i = pte_index(start), addr = start; addr != end; i++, addr += PAGE_SIZE) {
3347 unsigned long pfn;
3348 struct folio *folio;
3349 pte_t ptent = ptep_get(pte + i);
3350
3351 total++;
3352 walk->mm_stats[MM_LEAF_TOTAL]++;
3353
3354 pfn = get_pte_pfn(ptent, args->vma, addr);
3355 if (pfn == -1)
3356 continue;
3357
3358 if (!pte_young(ptent)) {
3359 walk->mm_stats[MM_LEAF_OLD]++;
3360 continue;
3361 }
3362
3363 folio = get_pfn_folio(pfn, memcg, pgdat, walk->can_swap);
3364 if (!folio)
3365 continue;
3366
3367 if (!ptep_test_and_clear_young(args->vma, addr, pte + i))
3368 VM_WARN_ON_ONCE(true);
3369
3370 young++;
3371 walk->mm_stats[MM_LEAF_YOUNG]++;
3372
3373 if (pte_dirty(ptent) && !folio_test_dirty(folio) &&
3374 !(folio_test_anon(folio) && folio_test_swapbacked(folio) &&
3375 !folio_test_swapcache(folio)))
3376 folio_mark_dirty(folio);
3377
3378 old_gen = folio_update_gen(folio, new_gen);
3379 if (old_gen >= 0 && old_gen != new_gen)
3380 update_batch_size(walk, folio, old_gen, new_gen);
3381 }
3382
3383 if (i < PTRS_PER_PTE && get_next_vma(PMD_MASK, PAGE_SIZE, args, &start, &end))
3384 goto restart;
3385
3386 arch_leave_lazy_mmu_mode();
3387 pte_unmap_unlock(pte, ptl);
3388
3389 return suitable_to_scan(total, young);
3390}
3391
3392static void walk_pmd_range_locked(pud_t *pud, unsigned long addr, struct vm_area_struct *vma,
3393 struct mm_walk *args, unsigned long *bitmap, unsigned long *first)
3394{
3395 int i;
3396 pmd_t *pmd;
3397 spinlock_t *ptl;
3398 struct lru_gen_mm_walk *walk = args->private;
3399 struct mem_cgroup *memcg = lruvec_memcg(walk->lruvec);
3400 struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);
3401 int old_gen, new_gen = lru_gen_from_seq(walk->max_seq);
3402
3403 VM_WARN_ON_ONCE(pud_leaf(*pud));
3404
3405 /* try to batch at most 1+MIN_LRU_BATCH+1 entries */
3406 if (*first == -1) {
3407 *first = addr;
3408 bitmap_zero(bitmap, MIN_LRU_BATCH);
3409 return;
3410 }
3411
3412 i = addr == -1 ? 0 : pmd_index(addr) - pmd_index(*first);
3413 if (i && i <= MIN_LRU_BATCH) {
3414 __set_bit(i - 1, bitmap);
3415 return;
3416 }
3417
3418 pmd = pmd_offset(pud, *first);
3419
3420 ptl = pmd_lockptr(args->mm, pmd);
3421 if (!spin_trylock(ptl))
3422 goto done;
3423
3424 arch_enter_lazy_mmu_mode();
3425
3426 do {
3427 unsigned long pfn;
3428 struct folio *folio;
3429
3430 /* don't round down the first address */
3431 addr = i ? (*first & PMD_MASK) + i * PMD_SIZE : *first;
3432
3433 pfn = get_pmd_pfn(pmd[i], vma, addr);
3434 if (pfn == -1)
3435 goto next;
3436
3437 if (!pmd_trans_huge(pmd[i])) {
3438 if (should_clear_pmd_young())
3439 pmdp_test_and_clear_young(vma, addr, pmd + i);
3440 goto next;
3441 }
3442
3443 folio = get_pfn_folio(pfn, memcg, pgdat, walk->can_swap);
3444 if (!folio)
3445 goto next;
3446
3447 if (!pmdp_test_and_clear_young(vma, addr, pmd + i))
3448 goto next;
3449
3450 walk->mm_stats[MM_LEAF_YOUNG]++;
3451
3452 if (pmd_dirty(pmd[i]) && !folio_test_dirty(folio) &&
3453 !(folio_test_anon(folio) && folio_test_swapbacked(folio) &&
3454 !folio_test_swapcache(folio)))
3455 folio_mark_dirty(folio);
3456
3457 old_gen = folio_update_gen(folio, new_gen);
3458 if (old_gen >= 0 && old_gen != new_gen)
3459 update_batch_size(walk, folio, old_gen, new_gen);
3460next:
3461 i = i > MIN_LRU_BATCH ? 0 : find_next_bit(bitmap, MIN_LRU_BATCH, i) + 1;
3462 } while (i <= MIN_LRU_BATCH);
3463
3464 arch_leave_lazy_mmu_mode();
3465 spin_unlock(ptl);
3466done:
3467 *first = -1;
3468}
3469
3470static void walk_pmd_range(pud_t *pud, unsigned long start, unsigned long end,
3471 struct mm_walk *args)
3472{
3473 int i;
3474 pmd_t *pmd;
3475 unsigned long next;
3476 unsigned long addr;
3477 struct vm_area_struct *vma;
3478 DECLARE_BITMAP(bitmap, MIN_LRU_BATCH);
3479 unsigned long first = -1;
3480 struct lru_gen_mm_walk *walk = args->private;
3481 struct lru_gen_mm_state *mm_state = get_mm_state(walk->lruvec);
3482
3483 VM_WARN_ON_ONCE(pud_leaf(*pud));
3484
3485 /*
3486 * Finish an entire PMD in two passes: the first only reaches to PTE
3487 * tables to avoid taking the PMD lock; the second, if necessary, takes
3488 * the PMD lock to clear the accessed bit in PMD entries.
3489 */
3490 pmd = pmd_offset(pud, start & PUD_MASK);
3491restart:
3492 /* walk_pte_range() may call get_next_vma() */
3493 vma = args->vma;
3494 for (i = pmd_index(start), addr = start; addr != end; i++, addr = next) {
3495 pmd_t val = pmdp_get_lockless(pmd + i);
3496
3497 next = pmd_addr_end(addr, end);
3498
3499 if (!pmd_present(val) || is_huge_zero_pmd(val)) {
3500 walk->mm_stats[MM_LEAF_TOTAL]++;
3501 continue;
3502 }
3503
3504 if (pmd_trans_huge(val)) {
3505 unsigned long pfn = pmd_pfn(val);
3506 struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);
3507
3508 walk->mm_stats[MM_LEAF_TOTAL]++;
3509
3510 if (!pmd_young(val)) {
3511 walk->mm_stats[MM_LEAF_OLD]++;
3512 continue;
3513 }
3514
3515 /* try to avoid unnecessary memory loads */
3516 if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat))
3517 continue;
3518
3519 walk_pmd_range_locked(pud, addr, vma, args, bitmap, &first);
3520 continue;
3521 }
3522
3523 walk->mm_stats[MM_NONLEAF_TOTAL]++;
3524
3525 if (should_clear_pmd_young()) {
3526 if (!pmd_young(val))
3527 continue;
3528
3529 walk_pmd_range_locked(pud, addr, vma, args, bitmap, &first);
3530 }
3531
3532 if (!walk->force_scan && !test_bloom_filter(mm_state, walk->max_seq, pmd + i))
3533 continue;
3534
3535 walk->mm_stats[MM_NONLEAF_FOUND]++;
3536
3537 if (!walk_pte_range(&val, addr, next, args))
3538 continue;
3539
3540 walk->mm_stats[MM_NONLEAF_ADDED]++;
3541
3542 /* carry over to the next generation */
3543 update_bloom_filter(mm_state, walk->max_seq + 1, pmd + i);
3544 }
3545
3546 walk_pmd_range_locked(pud, -1, vma, args, bitmap, &first);
3547
3548 if (i < PTRS_PER_PMD && get_next_vma(PUD_MASK, PMD_SIZE, args, &start, &end))
3549 goto restart;
3550}
3551
3552static int walk_pud_range(p4d_t *p4d, unsigned long start, unsigned long end,
3553 struct mm_walk *args)
3554{
3555 int i;
3556 pud_t *pud;
3557 unsigned long addr;
3558 unsigned long next;
3559 struct lru_gen_mm_walk *walk = args->private;
3560
3561 VM_WARN_ON_ONCE(p4d_leaf(*p4d));
3562
3563 pud = pud_offset(p4d, start & P4D_MASK);
3564restart:
3565 for (i = pud_index(start), addr = start; addr != end; i++, addr = next) {
3566 pud_t val = READ_ONCE(pud[i]);
3567
3568 next = pud_addr_end(addr, end);
3569
3570 if (!pud_present(val) || WARN_ON_ONCE(pud_leaf(val)))
3571 continue;
3572
3573 walk_pmd_range(&val, addr, next, args);
3574
3575 if (need_resched() || walk->batched >= MAX_LRU_BATCH) {
3576 end = (addr | ~PUD_MASK) + 1;
3577 goto done;
3578 }
3579 }
3580
3581 if (i < PTRS_PER_PUD && get_next_vma(P4D_MASK, PUD_SIZE, args, &start, &end))
3582 goto restart;
3583
3584 end = round_up(end, P4D_SIZE);
3585done:
3586 if (!end || !args->vma)
3587 return 1;
3588
3589 walk->next_addr = max(end, args->vma->vm_start);
3590
3591 return -EAGAIN;
3592}
3593
3594static void walk_mm(struct lruvec *lruvec, struct mm_struct *mm, struct lru_gen_mm_walk *walk)
3595{
3596 static const struct mm_walk_ops mm_walk_ops = {
3597 .test_walk = should_skip_vma,
3598 .p4d_entry = walk_pud_range,
3599 .walk_lock = PGWALK_RDLOCK,
3600 };
3601
3602 int err;
3603 struct mem_cgroup *memcg = lruvec_memcg(lruvec);
3604
3605 walk->next_addr = FIRST_USER_ADDRESS;
3606
3607 do {
3608 DEFINE_MAX_SEQ(lruvec);
3609
3610 err = -EBUSY;
3611
3612 /* another thread might have called inc_max_seq() */
3613 if (walk->max_seq != max_seq)
3614 break;
3615
3616 /* folio_update_gen() requires stable folio_memcg() */
3617 if (!mem_cgroup_trylock_pages(memcg))
3618 break;
3619
3620 /* the caller might be holding the lock for write */
3621 if (mmap_read_trylock(mm)) {
3622 err = walk_page_range(mm, walk->next_addr, ULONG_MAX, &mm_walk_ops, walk);
3623
3624 mmap_read_unlock(mm);
3625 }
3626
3627 mem_cgroup_unlock_pages();
3628
3629 if (walk->batched) {
3630 spin_lock_irq(&lruvec->lru_lock);
3631 reset_batch_size(lruvec, walk);
3632 spin_unlock_irq(&lruvec->lru_lock);
3633 }
3634
3635 cond_resched();
3636 } while (err == -EAGAIN);
3637}
3638
3639static struct lru_gen_mm_walk *set_mm_walk(struct pglist_data *pgdat, bool force_alloc)
3640{
3641 struct lru_gen_mm_walk *walk = current->reclaim_state->mm_walk;
3642
3643 if (pgdat && current_is_kswapd()) {
3644 VM_WARN_ON_ONCE(walk);
3645
3646 walk = &pgdat->mm_walk;
3647 } else if (!walk && force_alloc) {
3648 VM_WARN_ON_ONCE(current_is_kswapd());
3649
3650 walk = kzalloc(sizeof(*walk), __GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN);
3651 }
3652
3653 current->reclaim_state->mm_walk = walk;
3654
3655 return walk;
3656}
3657
3658static void clear_mm_walk(void)
3659{
3660 struct lru_gen_mm_walk *walk = current->reclaim_state->mm_walk;
3661
3662 VM_WARN_ON_ONCE(walk && memchr_inv(walk->nr_pages, 0, sizeof(walk->nr_pages)));
3663 VM_WARN_ON_ONCE(walk && memchr_inv(walk->mm_stats, 0, sizeof(walk->mm_stats)));
3664
3665 current->reclaim_state->mm_walk = NULL;
3666
3667 if (!current_is_kswapd())
3668 kfree(walk);
3669}
3670
3671static bool inc_min_seq(struct lruvec *lruvec, int type, bool can_swap)
3672{
3673 int zone;
3674 int remaining = MAX_LRU_BATCH;
3675 struct lru_gen_folio *lrugen = &lruvec->lrugen;
3676 int new_gen, old_gen = lru_gen_from_seq(lrugen->min_seq[type]);
3677
3678 if (type == LRU_GEN_ANON && !can_swap)
3679 goto done;
3680
3681 /* prevent cold/hot inversion if force_scan is true */
3682 for (zone = 0; zone < MAX_NR_ZONES; zone++) {
3683 struct list_head *head = &lrugen->folios[old_gen][type][zone];
3684
3685 while (!list_empty(head)) {
3686 struct folio *folio = lru_to_folio(head);
3687
3688 VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio);
3689 VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio), folio);
3690 VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio);
3691 VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio) != zone, folio);
3692
3693 new_gen = folio_inc_gen(lruvec, folio, false);
3694 list_move_tail(&folio->lru, &lrugen->folios[new_gen][type][zone]);
3695
3696 if (!--remaining)
3697 return false;
3698 }
3699 }
3700done:
3701 reset_ctrl_pos(lruvec, type, true);
3702 WRITE_ONCE(lrugen->min_seq[type], lrugen->min_seq[type] + 1);
3703
3704 return true;
3705}
3706
3707static bool try_to_inc_min_seq(struct lruvec *lruvec, bool can_swap)
3708{
3709 int gen, type, zone;
3710 bool success = false;
3711 struct lru_gen_folio *lrugen = &lruvec->lrugen;
3712 DEFINE_MIN_SEQ(lruvec);
3713
3714 VM_WARN_ON_ONCE(!seq_is_valid(lruvec));
3715
3716 /* find the oldest populated generation */
3717 for (type = !can_swap; type < ANON_AND_FILE; type++) {
3718 while (min_seq[type] + MIN_NR_GENS <= lrugen->max_seq) {
3719 gen = lru_gen_from_seq(min_seq[type]);
3720
3721 for (zone = 0; zone < MAX_NR_ZONES; zone++) {
3722 if (!list_empty(&lrugen->folios[gen][type][zone]))
3723 goto next;
3724 }
3725
3726 min_seq[type]++;
3727 }
3728next:
3729 ;
3730 }
3731
3732 /* see the comment on lru_gen_folio */
3733 if (can_swap) {
3734 min_seq[LRU_GEN_ANON] = min(min_seq[LRU_GEN_ANON], min_seq[LRU_GEN_FILE]);
3735 min_seq[LRU_GEN_FILE] = max(min_seq[LRU_GEN_ANON], lrugen->min_seq[LRU_GEN_FILE]);
3736 }
3737
3738 for (type = !can_swap; type < ANON_AND_FILE; type++) {
3739 if (min_seq[type] == lrugen->min_seq[type])
3740 continue;
3741
3742 reset_ctrl_pos(lruvec, type, true);
3743 WRITE_ONCE(lrugen->min_seq[type], min_seq[type]);
3744 success = true;
3745 }
3746
3747 return success;
3748}
3749
3750static bool inc_max_seq(struct lruvec *lruvec, unsigned long max_seq,
3751 bool can_swap, bool force_scan)
3752{
3753 bool success;
3754 int prev, next;
3755 int type, zone;
3756 struct lru_gen_folio *lrugen = &lruvec->lrugen;
3757restart:
3758 if (max_seq < READ_ONCE(lrugen->max_seq))
3759 return false;
3760
3761 spin_lock_irq(&lruvec->lru_lock);
3762
3763 VM_WARN_ON_ONCE(!seq_is_valid(lruvec));
3764
3765 success = max_seq == lrugen->max_seq;
3766 if (!success)
3767 goto unlock;
3768
3769 for (type = ANON_AND_FILE - 1; type >= 0; type--) {
3770 if (get_nr_gens(lruvec, type) != MAX_NR_GENS)
3771 continue;
3772
3773 VM_WARN_ON_ONCE(!force_scan && (type == LRU_GEN_FILE || can_swap));
3774
3775 if (inc_min_seq(lruvec, type, can_swap))
3776 continue;
3777
3778 spin_unlock_irq(&lruvec->lru_lock);
3779 cond_resched();
3780 goto restart;
3781 }
3782
3783 /*
3784 * Update the active/inactive LRU sizes for compatibility. Both sides of
3785 * the current max_seq need to be covered, since max_seq+1 can overlap
3786 * with min_seq[LRU_GEN_ANON] if swapping is constrained. And if they do
3787 * overlap, cold/hot inversion happens.
3788 */
3789 prev = lru_gen_from_seq(lrugen->max_seq - 1);
3790 next = lru_gen_from_seq(lrugen->max_seq + 1);
3791
3792 for (type = 0; type < ANON_AND_FILE; type++) {
3793 for (zone = 0; zone < MAX_NR_ZONES; zone++) {
3794 enum lru_list lru = type * LRU_INACTIVE_FILE;
3795 long delta = lrugen->nr_pages[prev][type][zone] -
3796 lrugen->nr_pages[next][type][zone];
3797
3798 if (!delta)
3799 continue;
3800
3801 __update_lru_size(lruvec, lru, zone, delta);
3802 __update_lru_size(lruvec, lru + LRU_ACTIVE, zone, -delta);
3803 }
3804 }
3805
3806 for (type = 0; type < ANON_AND_FILE; type++)
3807 reset_ctrl_pos(lruvec, type, false);
3808
3809 WRITE_ONCE(lrugen->timestamps[next], jiffies);
3810 /* make sure preceding modifications appear */
3811 smp_store_release(&lrugen->max_seq, lrugen->max_seq + 1);
3812unlock:
3813 spin_unlock_irq(&lruvec->lru_lock);
3814
3815 return success;
3816}
3817
3818static bool try_to_inc_max_seq(struct lruvec *lruvec, unsigned long max_seq,
3819 struct scan_control *sc, bool can_swap, bool force_scan)
3820{
3821 bool success;
3822 struct lru_gen_mm_walk *walk;
3823 struct mm_struct *mm = NULL;
3824 struct lru_gen_folio *lrugen = &lruvec->lrugen;
3825 struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
3826
3827 VM_WARN_ON_ONCE(max_seq > READ_ONCE(lrugen->max_seq));
3828
3829 if (!mm_state)
3830 return inc_max_seq(lruvec, max_seq, can_swap, force_scan);
3831
3832 /* see the comment in iterate_mm_list() */
3833 if (max_seq <= READ_ONCE(mm_state->seq))
3834 return false;
3835
3836 /*
3837 * If the hardware doesn't automatically set the accessed bit, fallback
3838 * to lru_gen_look_around(), which only clears the accessed bit in a
3839 * handful of PTEs. Spreading the work out over a period of time usually
3840 * is less efficient, but it avoids bursty page faults.
3841 */
3842 if (!should_walk_mmu()) {
3843 success = iterate_mm_list_nowalk(lruvec, max_seq);
3844 goto done;
3845 }
3846
3847 walk = set_mm_walk(NULL, true);
3848 if (!walk) {
3849 success = iterate_mm_list_nowalk(lruvec, max_seq);
3850 goto done;
3851 }
3852
3853 walk->lruvec = lruvec;
3854 walk->max_seq = max_seq;
3855 walk->can_swap = can_swap;
3856 walk->force_scan = force_scan;
3857
3858 do {
3859 success = iterate_mm_list(lruvec, walk, &mm);
3860 if (mm)
3861 walk_mm(lruvec, mm, walk);
3862 } while (mm);
3863done:
3864 if (success) {
3865 success = inc_max_seq(lruvec, max_seq, can_swap, force_scan);
3866 WARN_ON_ONCE(!success);
3867 }
3868
3869 return success;
3870}
3871
3872/******************************************************************************
3873 * working set protection
3874 ******************************************************************************/
3875
3876static bool lruvec_is_sizable(struct lruvec *lruvec, struct scan_control *sc)
3877{
3878 int gen, type, zone;
3879 unsigned long total = 0;
3880 bool can_swap = get_swappiness(lruvec, sc);
3881 struct lru_gen_folio *lrugen = &lruvec->lrugen;
3882 struct mem_cgroup *memcg = lruvec_memcg(lruvec);
3883 DEFINE_MAX_SEQ(lruvec);
3884 DEFINE_MIN_SEQ(lruvec);
3885
3886 for (type = !can_swap; type < ANON_AND_FILE; type++) {
3887 unsigned long seq;
3888
3889 for (seq = min_seq[type]; seq <= max_seq; seq++) {
3890 gen = lru_gen_from_seq(seq);
3891
3892 for (zone = 0; zone < MAX_NR_ZONES; zone++)
3893 total += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L);
3894 }
3895 }
3896
3897 /* whether the size is big enough to be helpful */
3898 return mem_cgroup_online(memcg) ? (total >> sc->priority) : total;
3899}
3900
3901static bool lruvec_is_reclaimable(struct lruvec *lruvec, struct scan_control *sc,
3902 unsigned long min_ttl)
3903{
3904 int gen;
3905 unsigned long birth;
3906 struct mem_cgroup *memcg = lruvec_memcg(lruvec);
3907 DEFINE_MIN_SEQ(lruvec);
3908
3909 /* see the comment on lru_gen_folio */
3910 gen = lru_gen_from_seq(min_seq[LRU_GEN_FILE]);
3911 birth = READ_ONCE(lruvec->lrugen.timestamps[gen]);
3912
3913 if (time_is_after_jiffies(birth + min_ttl))
3914 return false;
3915
3916 if (!lruvec_is_sizable(lruvec, sc))
3917 return false;
3918
3919 mem_cgroup_calculate_protection(NULL, memcg);
3920
3921 return !mem_cgroup_below_min(NULL, memcg);
3922}
3923
3924/* to protect the working set of the last N jiffies */
3925static unsigned long lru_gen_min_ttl __read_mostly;
3926
3927static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc)
3928{
3929 struct mem_cgroup *memcg;
3930 unsigned long min_ttl = READ_ONCE(lru_gen_min_ttl);
3931
3932 VM_WARN_ON_ONCE(!current_is_kswapd());
3933
3934 /* check the order to exclude compaction-induced reclaim */
3935 if (!min_ttl || sc->order || sc->priority == DEF_PRIORITY)
3936 return;
3937
3938 memcg = mem_cgroup_iter(NULL, NULL, NULL);
3939 do {
3940 struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
3941
3942 if (lruvec_is_reclaimable(lruvec, sc, min_ttl)) {
3943 mem_cgroup_iter_break(NULL, memcg);
3944 return;
3945 }
3946
3947 cond_resched();
3948 } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)));
3949
3950 /*
3951 * The main goal is to OOM kill if every generation from all memcgs is
3952 * younger than min_ttl. However, another possibility is all memcgs are
3953 * either too small or below min.
3954 */
3955 if (mutex_trylock(&oom_lock)) {
3956 struct oom_control oc = {
3957 .gfp_mask = sc->gfp_mask,
3958 };
3959
3960 out_of_memory(&oc);
3961
3962 mutex_unlock(&oom_lock);
3963 }
3964}
3965
3966/******************************************************************************
3967 * rmap/PT walk feedback
3968 ******************************************************************************/
3969
3970/*
3971 * This function exploits spatial locality when shrink_folio_list() walks the
3972 * rmap. It scans the adjacent PTEs of a young PTE and promotes hot pages. If
3973 * the scan was done cacheline efficiently, it adds the PMD entry pointing to
3974 * the PTE table to the Bloom filter. This forms a feedback loop between the
3975 * eviction and the aging.
3976 */
3977void lru_gen_look_around(struct page_vma_mapped_walk *pvmw)
3978{
3979 int i;
3980 unsigned long start;
3981 unsigned long end;
3982 struct lru_gen_mm_walk *walk;
3983 int young = 0;
3984 pte_t *pte = pvmw->pte;
3985 unsigned long addr = pvmw->address;
3986 struct vm_area_struct *vma = pvmw->vma;
3987 struct folio *folio = pfn_folio(pvmw->pfn);
3988 bool can_swap = !folio_is_file_lru(folio);
3989 struct mem_cgroup *memcg = folio_memcg(folio);
3990 struct pglist_data *pgdat = folio_pgdat(folio);
3991 struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
3992 struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
3993 DEFINE_MAX_SEQ(lruvec);
3994 int old_gen, new_gen = lru_gen_from_seq(max_seq);
3995
3996 lockdep_assert_held(pvmw->ptl);
3997 VM_WARN_ON_ONCE_FOLIO(folio_test_lru(folio), folio);
3998
3999 if (spin_is_contended(pvmw->ptl))
4000 return;
4001
4002 /* exclude special VMAs containing anon pages from COW */
4003 if (vma->vm_flags & VM_SPECIAL)
4004 return;
4005
4006 /* avoid taking the LRU lock under the PTL when possible */
4007 walk = current->reclaim_state ? current->reclaim_state->mm_walk : NULL;
4008
4009 start = max(addr & PMD_MASK, vma->vm_start);
4010 end = min(addr | ~PMD_MASK, vma->vm_end - 1) + 1;
4011
4012 if (end - start > MIN_LRU_BATCH * PAGE_SIZE) {
4013 if (addr - start < MIN_LRU_BATCH * PAGE_SIZE / 2)
4014 end = start + MIN_LRU_BATCH * PAGE_SIZE;
4015 else if (end - addr < MIN_LRU_BATCH * PAGE_SIZE / 2)
4016 start = end - MIN_LRU_BATCH * PAGE_SIZE;
4017 else {
4018 start = addr - MIN_LRU_BATCH * PAGE_SIZE / 2;
4019 end = addr + MIN_LRU_BATCH * PAGE_SIZE / 2;
4020 }
4021 }
4022
4023 /* folio_update_gen() requires stable folio_memcg() */
4024 if (!mem_cgroup_trylock_pages(memcg))
4025 return;
4026
4027 arch_enter_lazy_mmu_mode();
4028
4029 pte -= (addr - start) / PAGE_SIZE;
4030
4031 for (i = 0, addr = start; addr != end; i++, addr += PAGE_SIZE) {
4032 unsigned long pfn;
4033 pte_t ptent = ptep_get(pte + i);
4034
4035 pfn = get_pte_pfn(ptent, vma, addr);
4036 if (pfn == -1)
4037 continue;
4038
4039 if (!pte_young(ptent))
4040 continue;
4041
4042 folio = get_pfn_folio(pfn, memcg, pgdat, can_swap);
4043 if (!folio)
4044 continue;
4045
4046 if (!ptep_test_and_clear_young(vma, addr, pte + i))
4047 VM_WARN_ON_ONCE(true);
4048
4049 young++;
4050
4051 if (pte_dirty(ptent) && !folio_test_dirty(folio) &&
4052 !(folio_test_anon(folio) && folio_test_swapbacked(folio) &&
4053 !folio_test_swapcache(folio)))
4054 folio_mark_dirty(folio);
4055
4056 if (walk) {
4057 old_gen = folio_update_gen(folio, new_gen);
4058 if (old_gen >= 0 && old_gen != new_gen)
4059 update_batch_size(walk, folio, old_gen, new_gen);
4060
4061 continue;
4062 }
4063
4064 old_gen = folio_lru_gen(folio);
4065 if (old_gen < 0)
4066 folio_set_referenced(folio);
4067 else if (old_gen != new_gen)
4068 folio_activate(folio);
4069 }
4070
4071 arch_leave_lazy_mmu_mode();
4072 mem_cgroup_unlock_pages();
4073
4074 /* feedback from rmap walkers to page table walkers */
4075 if (mm_state && suitable_to_scan(i, young))
4076 update_bloom_filter(mm_state, max_seq, pvmw->pmd);
4077}
4078
4079/******************************************************************************
4080 * memcg LRU
4081 ******************************************************************************/
4082
4083/* see the comment on MEMCG_NR_GENS */
4084enum {
4085 MEMCG_LRU_NOP,
4086 MEMCG_LRU_HEAD,
4087 MEMCG_LRU_TAIL,
4088 MEMCG_LRU_OLD,
4089 MEMCG_LRU_YOUNG,
4090};
4091
4092static void lru_gen_rotate_memcg(struct lruvec *lruvec, int op)
4093{
4094 int seg;
4095 int old, new;
4096 unsigned long flags;
4097 int bin = get_random_u32_below(MEMCG_NR_BINS);
4098 struct pglist_data *pgdat = lruvec_pgdat(lruvec);
4099
4100 spin_lock_irqsave(&pgdat->memcg_lru.lock, flags);
4101
4102 VM_WARN_ON_ONCE(hlist_nulls_unhashed(&lruvec->lrugen.list));
4103
4104 seg = 0;
4105 new = old = lruvec->lrugen.gen;
4106
4107 /* see the comment on MEMCG_NR_GENS */
4108 if (op == MEMCG_LRU_HEAD)
4109 seg = MEMCG_LRU_HEAD;
4110 else if (op == MEMCG_LRU_TAIL)
4111 seg = MEMCG_LRU_TAIL;
4112 else if (op == MEMCG_LRU_OLD)
4113 new = get_memcg_gen(pgdat->memcg_lru.seq);
4114 else if (op == MEMCG_LRU_YOUNG)
4115 new = get_memcg_gen(pgdat->memcg_lru.seq + 1);
4116 else
4117 VM_WARN_ON_ONCE(true);
4118
4119 WRITE_ONCE(lruvec->lrugen.seg, seg);
4120 WRITE_ONCE(lruvec->lrugen.gen, new);
4121
4122 hlist_nulls_del_rcu(&lruvec->lrugen.list);
4123
4124 if (op == MEMCG_LRU_HEAD || op == MEMCG_LRU_OLD)
4125 hlist_nulls_add_head_rcu(&lruvec->lrugen.list, &pgdat->memcg_lru.fifo[new][bin]);
4126 else
4127 hlist_nulls_add_tail_rcu(&lruvec->lrugen.list, &pgdat->memcg_lru.fifo[new][bin]);
4128
4129 pgdat->memcg_lru.nr_memcgs[old]--;
4130 pgdat->memcg_lru.nr_memcgs[new]++;
4131
4132 if (!pgdat->memcg_lru.nr_memcgs[old] && old == get_memcg_gen(pgdat->memcg_lru.seq))
4133 WRITE_ONCE(pgdat->memcg_lru.seq, pgdat->memcg_lru.seq + 1);
4134
4135 spin_unlock_irqrestore(&pgdat->memcg_lru.lock, flags);
4136}
4137
4138#ifdef CONFIG_MEMCG
4139
4140void lru_gen_online_memcg(struct mem_cgroup *memcg)
4141{
4142 int gen;
4143 int nid;
4144 int bin = get_random_u32_below(MEMCG_NR_BINS);
4145
4146 for_each_node(nid) {
4147 struct pglist_data *pgdat = NODE_DATA(nid);
4148 struct lruvec *lruvec = get_lruvec(memcg, nid);
4149
4150 spin_lock_irq(&pgdat->memcg_lru.lock);
4151
4152 VM_WARN_ON_ONCE(!hlist_nulls_unhashed(&lruvec->lrugen.list));
4153
4154 gen = get_memcg_gen(pgdat->memcg_lru.seq);
4155
4156 lruvec->lrugen.gen = gen;
4157
4158 hlist_nulls_add_tail_rcu(&lruvec->lrugen.list, &pgdat->memcg_lru.fifo[gen][bin]);
4159 pgdat->memcg_lru.nr_memcgs[gen]++;
4160
4161 spin_unlock_irq(&pgdat->memcg_lru.lock);
4162 }
4163}
4164
4165void lru_gen_offline_memcg(struct mem_cgroup *memcg)
4166{
4167 int nid;
4168
4169 for_each_node(nid) {
4170 struct lruvec *lruvec = get_lruvec(memcg, nid);
4171
4172 lru_gen_rotate_memcg(lruvec, MEMCG_LRU_OLD);
4173 }
4174}
4175
4176void lru_gen_release_memcg(struct mem_cgroup *memcg)
4177{
4178 int gen;
4179 int nid;
4180
4181 for_each_node(nid) {
4182 struct pglist_data *pgdat = NODE_DATA(nid);
4183 struct lruvec *lruvec = get_lruvec(memcg, nid);
4184
4185 spin_lock_irq(&pgdat->memcg_lru.lock);
4186
4187 if (hlist_nulls_unhashed(&lruvec->lrugen.list))
4188 goto unlock;
4189
4190 gen = lruvec->lrugen.gen;
4191
4192 hlist_nulls_del_init_rcu(&lruvec->lrugen.list);
4193 pgdat->memcg_lru.nr_memcgs[gen]--;
4194
4195 if (!pgdat->memcg_lru.nr_memcgs[gen] && gen == get_memcg_gen(pgdat->memcg_lru.seq))
4196 WRITE_ONCE(pgdat->memcg_lru.seq, pgdat->memcg_lru.seq + 1);
4197unlock:
4198 spin_unlock_irq(&pgdat->memcg_lru.lock);
4199 }
4200}
4201
4202void lru_gen_soft_reclaim(struct mem_cgroup *memcg, int nid)
4203{
4204 struct lruvec *lruvec = get_lruvec(memcg, nid);
4205
4206 /* see the comment on MEMCG_NR_GENS */
4207 if (READ_ONCE(lruvec->lrugen.seg) != MEMCG_LRU_HEAD)
4208 lru_gen_rotate_memcg(lruvec, MEMCG_LRU_HEAD);
4209}
4210
4211#endif /* CONFIG_MEMCG */
4212
4213/******************************************************************************
4214 * the eviction
4215 ******************************************************************************/
4216
4217static bool sort_folio(struct lruvec *lruvec, struct folio *folio, struct scan_control *sc,
4218 int tier_idx)
4219{
4220 bool success;
4221 int gen = folio_lru_gen(folio);
4222 int type = folio_is_file_lru(folio);
4223 int zone = folio_zonenum(folio);
4224 int delta = folio_nr_pages(folio);
4225 int refs = folio_lru_refs(folio);
4226 int tier = lru_tier_from_refs(refs);
4227 struct lru_gen_folio *lrugen = &lruvec->lrugen;
4228
4229 VM_WARN_ON_ONCE_FOLIO(gen >= MAX_NR_GENS, folio);
4230
4231 /* unevictable */
4232 if (!folio_evictable(folio)) {
4233 success = lru_gen_del_folio(lruvec, folio, true);
4234 VM_WARN_ON_ONCE_FOLIO(!success, folio);
4235 folio_set_unevictable(folio);
4236 lruvec_add_folio(lruvec, folio);
4237 __count_vm_events(UNEVICTABLE_PGCULLED, delta);
4238 return true;
4239 }
4240
4241 /* dirty lazyfree */
4242 if (type == LRU_GEN_FILE && folio_test_anon(folio) && folio_test_dirty(folio)) {
4243 success = lru_gen_del_folio(lruvec, folio, true);
4244 VM_WARN_ON_ONCE_FOLIO(!success, folio);
4245 folio_set_swapbacked(folio);
4246 lruvec_add_folio_tail(lruvec, folio);
4247 return true;
4248 }
4249
4250 /* promoted */
4251 if (gen != lru_gen_from_seq(lrugen->min_seq[type])) {
4252 list_move(&folio->lru, &lrugen->folios[gen][type][zone]);
4253 return true;
4254 }
4255
4256 /* protected */
4257 if (tier > tier_idx || refs == BIT(LRU_REFS_WIDTH)) {
4258 int hist = lru_hist_from_seq(lrugen->min_seq[type]);
4259
4260 gen = folio_inc_gen(lruvec, folio, false);
4261 list_move_tail(&folio->lru, &lrugen->folios[gen][type][zone]);
4262
4263 WRITE_ONCE(lrugen->protected[hist][type][tier - 1],
4264 lrugen->protected[hist][type][tier - 1] + delta);
4265 return true;
4266 }
4267
4268 /* ineligible */
4269 if (zone > sc->reclaim_idx || skip_cma(folio, sc)) {
4270 gen = folio_inc_gen(lruvec, folio, false);
4271 list_move_tail(&folio->lru, &lrugen->folios[gen][type][zone]);
4272 return true;
4273 }
4274
4275 /* waiting for writeback */
4276 if (folio_test_locked(folio) || folio_test_writeback(folio) ||
4277 (type == LRU_GEN_FILE && folio_test_dirty(folio))) {
4278 gen = folio_inc_gen(lruvec, folio, true);
4279 list_move(&folio->lru, &lrugen->folios[gen][type][zone]);
4280 return true;
4281 }
4282
4283 return false;
4284}
4285
4286static bool isolate_folio(struct lruvec *lruvec, struct folio *folio, struct scan_control *sc)
4287{
4288 bool success;
4289
4290 /* swapping inhibited */
4291 if (!(sc->gfp_mask & __GFP_IO) &&
4292 (folio_test_dirty(folio) ||
4293 (folio_test_anon(folio) && !folio_test_swapcache(folio))))
4294 return false;
4295
4296 /* raced with release_pages() */
4297 if (!folio_try_get(folio))
4298 return false;
4299
4300 /* raced with another isolation */
4301 if (!folio_test_clear_lru(folio)) {
4302 folio_put(folio);
4303 return false;
4304 }
4305
4306 /* see the comment on MAX_NR_TIERS */
4307 if (!folio_test_referenced(folio))
4308 set_mask_bits(&folio->flags, LRU_REFS_MASK | LRU_REFS_FLAGS, 0);
4309
4310 /* for shrink_folio_list() */
4311 folio_clear_reclaim(folio);
4312 folio_clear_referenced(folio);
4313
4314 success = lru_gen_del_folio(lruvec, folio, true);
4315 VM_WARN_ON_ONCE_FOLIO(!success, folio);
4316
4317 return true;
4318}
4319
4320static int scan_folios(struct lruvec *lruvec, struct scan_control *sc,
4321 int type, int tier, struct list_head *list)
4322{
4323 int i;
4324 int gen;
4325 enum vm_event_item item;
4326 int sorted = 0;
4327 int scanned = 0;
4328 int isolated = 0;
4329 int skipped = 0;
4330 int remaining = MAX_LRU_BATCH;
4331 struct lru_gen_folio *lrugen = &lruvec->lrugen;
4332 struct mem_cgroup *memcg = lruvec_memcg(lruvec);
4333
4334 VM_WARN_ON_ONCE(!list_empty(list));
4335
4336 if (get_nr_gens(lruvec, type) == MIN_NR_GENS)
4337 return 0;
4338
4339 gen = lru_gen_from_seq(lrugen->min_seq[type]);
4340
4341 for (i = MAX_NR_ZONES; i > 0; i--) {
4342 LIST_HEAD(moved);
4343 int skipped_zone = 0;
4344 int zone = (sc->reclaim_idx + i) % MAX_NR_ZONES;
4345 struct list_head *head = &lrugen->folios[gen][type][zone];
4346
4347 while (!list_empty(head)) {
4348 struct folio *folio = lru_to_folio(head);
4349 int delta = folio_nr_pages(folio);
4350
4351 VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio);
4352 VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio), folio);
4353 VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio);
4354 VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio) != zone, folio);
4355
4356 scanned += delta;
4357
4358 if (sort_folio(lruvec, folio, sc, tier))
4359 sorted += delta;
4360 else if (isolate_folio(lruvec, folio, sc)) {
4361 list_add(&folio->lru, list);
4362 isolated += delta;
4363 } else {
4364 list_move(&folio->lru, &moved);
4365 skipped_zone += delta;
4366 }
4367
4368 if (!--remaining || max(isolated, skipped_zone) >= MIN_LRU_BATCH)
4369 break;
4370 }
4371
4372 if (skipped_zone) {
4373 list_splice(&moved, head);
4374 __count_zid_vm_events(PGSCAN_SKIP, zone, skipped_zone);
4375 skipped += skipped_zone;
4376 }
4377
4378 if (!remaining || isolated >= MIN_LRU_BATCH)
4379 break;
4380 }
4381
4382 item = PGSCAN_KSWAPD + reclaimer_offset();
4383 if (!cgroup_reclaim(sc)) {
4384 __count_vm_events(item, isolated);
4385 __count_vm_events(PGREFILL, sorted);
4386 }
4387 __count_memcg_events(memcg, item, isolated);
4388 __count_memcg_events(memcg, PGREFILL, sorted);
4389 __count_vm_events(PGSCAN_ANON + type, isolated);
4390 trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, MAX_LRU_BATCH,
4391 scanned, skipped, isolated,
4392 type ? LRU_INACTIVE_FILE : LRU_INACTIVE_ANON);
4393
4394 /*
4395 * There might not be eligible folios due to reclaim_idx. Check the
4396 * remaining to prevent livelock if it's not making progress.
4397 */
4398 return isolated || !remaining ? scanned : 0;
4399}
4400
4401static int get_tier_idx(struct lruvec *lruvec, int type)
4402{
4403 int tier;
4404 struct ctrl_pos sp, pv;
4405
4406 /*
4407 * To leave a margin for fluctuations, use a larger gain factor (1:2).
4408 * This value is chosen because any other tier would have at least twice
4409 * as many refaults as the first tier.
4410 */
4411 read_ctrl_pos(lruvec, type, 0, 1, &sp);
4412 for (tier = 1; tier < MAX_NR_TIERS; tier++) {
4413 read_ctrl_pos(lruvec, type, tier, 2, &pv);
4414 if (!positive_ctrl_err(&sp, &pv))
4415 break;
4416 }
4417
4418 return tier - 1;
4419}
4420
4421static int get_type_to_scan(struct lruvec *lruvec, int swappiness, int *tier_idx)
4422{
4423 int type, tier;
4424 struct ctrl_pos sp, pv;
4425 int gain[ANON_AND_FILE] = { swappiness, 200 - swappiness };
4426
4427 /*
4428 * Compare the first tier of anon with that of file to determine which
4429 * type to scan. Also need to compare other tiers of the selected type
4430 * with the first tier of the other type to determine the last tier (of
4431 * the selected type) to evict.
4432 */
4433 read_ctrl_pos(lruvec, LRU_GEN_ANON, 0, gain[LRU_GEN_ANON], &sp);
4434 read_ctrl_pos(lruvec, LRU_GEN_FILE, 0, gain[LRU_GEN_FILE], &pv);
4435 type = positive_ctrl_err(&sp, &pv);
4436
4437 read_ctrl_pos(lruvec, !type, 0, gain[!type], &sp);
4438 for (tier = 1; tier < MAX_NR_TIERS; tier++) {
4439 read_ctrl_pos(lruvec, type, tier, gain[type], &pv);
4440 if (!positive_ctrl_err(&sp, &pv))
4441 break;
4442 }
4443
4444 *tier_idx = tier - 1;
4445
4446 return type;
4447}
4448
4449static int isolate_folios(struct lruvec *lruvec, struct scan_control *sc, int swappiness,
4450 int *type_scanned, struct list_head *list)
4451{
4452 int i;
4453 int type;
4454 int scanned;
4455 int tier = -1;
4456 DEFINE_MIN_SEQ(lruvec);
4457
4458 /*
4459 * Try to make the obvious choice first. When anon and file are both
4460 * available from the same generation, interpret swappiness 1 as file
4461 * first and 200 as anon first.
4462 */
4463 if (!swappiness)
4464 type = LRU_GEN_FILE;
4465 else if (min_seq[LRU_GEN_ANON] < min_seq[LRU_GEN_FILE])
4466 type = LRU_GEN_ANON;
4467 else if (swappiness == 1)
4468 type = LRU_GEN_FILE;
4469 else if (swappiness == 200)
4470 type = LRU_GEN_ANON;
4471 else
4472 type = get_type_to_scan(lruvec, swappiness, &tier);
4473
4474 for (i = !swappiness; i < ANON_AND_FILE; i++) {
4475 if (tier < 0)
4476 tier = get_tier_idx(lruvec, type);
4477
4478 scanned = scan_folios(lruvec, sc, type, tier, list);
4479 if (scanned)
4480 break;
4481
4482 type = !type;
4483 tier = -1;
4484 }
4485
4486 *type_scanned = type;
4487
4488 return scanned;
4489}
4490
4491static int evict_folios(struct lruvec *lruvec, struct scan_control *sc, int swappiness)
4492{
4493 int type;
4494 int scanned;
4495 int reclaimed;
4496 LIST_HEAD(list);
4497 LIST_HEAD(clean);
4498 struct folio *folio;
4499 struct folio *next;
4500 enum vm_event_item item;
4501 struct reclaim_stat stat;
4502 struct lru_gen_mm_walk *walk;
4503 bool skip_retry = false;
4504 struct mem_cgroup *memcg = lruvec_memcg(lruvec);
4505 struct pglist_data *pgdat = lruvec_pgdat(lruvec);
4506
4507 spin_lock_irq(&lruvec->lru_lock);
4508
4509 scanned = isolate_folios(lruvec, sc, swappiness, &type, &list);
4510
4511 scanned += try_to_inc_min_seq(lruvec, swappiness);
4512
4513 if (get_nr_gens(lruvec, !swappiness) == MIN_NR_GENS)
4514 scanned = 0;
4515
4516 spin_unlock_irq(&lruvec->lru_lock);
4517
4518 if (list_empty(&list))
4519 return scanned;
4520retry:
4521 reclaimed = shrink_folio_list(&list, pgdat, sc, &stat, false);
4522 sc->nr_reclaimed += reclaimed;
4523 trace_mm_vmscan_lru_shrink_inactive(pgdat->node_id,
4524 scanned, reclaimed, &stat, sc->priority,
4525 type ? LRU_INACTIVE_FILE : LRU_INACTIVE_ANON);
4526
4527 list_for_each_entry_safe_reverse(folio, next, &list, lru) {
4528 if (!folio_evictable(folio)) {
4529 list_del(&folio->lru);
4530 folio_putback_lru(folio);
4531 continue;
4532 }
4533
4534 if (folio_test_reclaim(folio) &&
4535 (folio_test_dirty(folio) || folio_test_writeback(folio))) {
4536 /* restore LRU_REFS_FLAGS cleared by isolate_folio() */
4537 if (folio_test_workingset(folio))
4538 folio_set_referenced(folio);
4539 continue;
4540 }
4541
4542 if (skip_retry || folio_test_active(folio) || folio_test_referenced(folio) ||
4543 folio_mapped(folio) || folio_test_locked(folio) ||
4544 folio_test_dirty(folio) || folio_test_writeback(folio)) {
4545 /* don't add rejected folios to the oldest generation */
4546 set_mask_bits(&folio->flags, LRU_REFS_MASK | LRU_REFS_FLAGS,
4547 BIT(PG_active));
4548 continue;
4549 }
4550
4551 /* retry folios that may have missed folio_rotate_reclaimable() */
4552 list_move(&folio->lru, &clean);
4553 sc->nr_scanned -= folio_nr_pages(folio);
4554 }
4555
4556 spin_lock_irq(&lruvec->lru_lock);
4557
4558 move_folios_to_lru(lruvec, &list);
4559
4560 walk = current->reclaim_state->mm_walk;
4561 if (walk && walk->batched)
4562 reset_batch_size(lruvec, walk);
4563
4564 item = PGSTEAL_KSWAPD + reclaimer_offset();
4565 if (!cgroup_reclaim(sc))
4566 __count_vm_events(item, reclaimed);
4567 __count_memcg_events(memcg, item, reclaimed);
4568 __count_vm_events(PGSTEAL_ANON + type, reclaimed);
4569
4570 spin_unlock_irq(&lruvec->lru_lock);
4571
4572 mem_cgroup_uncharge_list(&list);
4573 free_unref_page_list(&list);
4574
4575 INIT_LIST_HEAD(&list);
4576 list_splice_init(&clean, &list);
4577
4578 if (!list_empty(&list)) {
4579 skip_retry = true;
4580 goto retry;
4581 }
4582
4583 return scanned;
4584}
4585
4586static bool should_run_aging(struct lruvec *lruvec, unsigned long max_seq,
4587 struct scan_control *sc, bool can_swap, unsigned long *nr_to_scan)
4588{
4589 int gen, type, zone;
4590 unsigned long old = 0;
4591 unsigned long young = 0;
4592 unsigned long total = 0;
4593 struct lru_gen_folio *lrugen = &lruvec->lrugen;
4594 struct mem_cgroup *memcg = lruvec_memcg(lruvec);
4595 DEFINE_MIN_SEQ(lruvec);
4596
4597 /* whether this lruvec is completely out of cold folios */
4598 if (min_seq[!can_swap] + MIN_NR_GENS > max_seq) {
4599 *nr_to_scan = 0;
4600 return true;
4601 }
4602
4603 for (type = !can_swap; type < ANON_AND_FILE; type++) {
4604 unsigned long seq;
4605
4606 for (seq = min_seq[type]; seq <= max_seq; seq++) {
4607 unsigned long size = 0;
4608
4609 gen = lru_gen_from_seq(seq);
4610
4611 for (zone = 0; zone < MAX_NR_ZONES; zone++)
4612 size += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L);
4613
4614 total += size;
4615 if (seq == max_seq)
4616 young += size;
4617 else if (seq + MIN_NR_GENS == max_seq)
4618 old += size;
4619 }
4620 }
4621
4622 /* try to scrape all its memory if this memcg was deleted */
4623 if (!mem_cgroup_online(memcg)) {
4624 *nr_to_scan = total;
4625 return false;
4626 }
4627
4628 *nr_to_scan = total >> sc->priority;
4629
4630 /*
4631 * The aging tries to be lazy to reduce the overhead, while the eviction
4632 * stalls when the number of generations reaches MIN_NR_GENS. Hence, the
4633 * ideal number of generations is MIN_NR_GENS+1.
4634 */
4635 if (min_seq[!can_swap] + MIN_NR_GENS < max_seq)
4636 return false;
4637
4638 /*
4639 * It's also ideal to spread pages out evenly, i.e., 1/(MIN_NR_GENS+1)
4640 * of the total number of pages for each generation. A reasonable range
4641 * for this average portion is [1/MIN_NR_GENS, 1/(MIN_NR_GENS+2)]. The
4642 * aging cares about the upper bound of hot pages, while the eviction
4643 * cares about the lower bound of cold pages.
4644 */
4645 if (young * MIN_NR_GENS > total)
4646 return true;
4647 if (old * (MIN_NR_GENS + 2) < total)
4648 return true;
4649
4650 return false;
4651}
4652
4653/*
4654 * For future optimizations:
4655 * 1. Defer try_to_inc_max_seq() to workqueues to reduce latency for memcg
4656 * reclaim.
4657 */
4658static long get_nr_to_scan(struct lruvec *lruvec, struct scan_control *sc, bool can_swap)
4659{
4660 unsigned long nr_to_scan;
4661 struct mem_cgroup *memcg = lruvec_memcg(lruvec);
4662 DEFINE_MAX_SEQ(lruvec);
4663
4664 if (mem_cgroup_below_min(sc->target_mem_cgroup, memcg))
4665 return -1;
4666
4667 if (!should_run_aging(lruvec, max_seq, sc, can_swap, &nr_to_scan))
4668 return nr_to_scan;
4669
4670 /* skip the aging path at the default priority */
4671 if (sc->priority == DEF_PRIORITY)
4672 return nr_to_scan;
4673
4674 /* skip this lruvec as it's low on cold folios */
4675 return try_to_inc_max_seq(lruvec, max_seq, sc, can_swap, false) ? -1 : 0;
4676}
4677
4678static bool should_abort_scan(struct lruvec *lruvec, struct scan_control *sc)
4679{
4680 int i;
4681 enum zone_watermarks mark;
4682
4683 /* don't abort memcg reclaim to ensure fairness */
4684 if (!root_reclaim(sc))
4685 return false;
4686
4687 if (sc->nr_reclaimed >= max(sc->nr_to_reclaim, compact_gap(sc->order)))
4688 return true;
4689
4690 /* check the order to exclude compaction-induced reclaim */
4691 if (!current_is_kswapd() || sc->order)
4692 return false;
4693
4694 mark = sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING ?
4695 WMARK_PROMO : WMARK_HIGH;
4696
4697 for (i = 0; i <= sc->reclaim_idx; i++) {
4698 struct zone *zone = lruvec_pgdat(lruvec)->node_zones + i;
4699 unsigned long size = wmark_pages(zone, mark) + MIN_LRU_BATCH;
4700
4701 if (managed_zone(zone) && !zone_watermark_ok(zone, 0, size, sc->reclaim_idx, 0))
4702 return false;
4703 }
4704
4705 /* kswapd should abort if all eligible zones are safe */
4706 return true;
4707}
4708
4709static bool try_to_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
4710{
4711 long nr_to_scan;
4712 unsigned long scanned = 0;
4713 int swappiness = get_swappiness(lruvec, sc);
4714
4715 /* clean file folios are more likely to exist */
4716 if (swappiness && !(sc->gfp_mask & __GFP_IO))
4717 swappiness = 1;
4718
4719 while (true) {
4720 int delta;
4721
4722 nr_to_scan = get_nr_to_scan(lruvec, sc, swappiness);
4723 if (nr_to_scan <= 0)
4724 break;
4725
4726 delta = evict_folios(lruvec, sc, swappiness);
4727 if (!delta)
4728 break;
4729
4730 scanned += delta;
4731 if (scanned >= nr_to_scan)
4732 break;
4733
4734 if (should_abort_scan(lruvec, sc))
4735 break;
4736
4737 cond_resched();
4738 }
4739
4740 /* whether this lruvec should be rotated */
4741 return nr_to_scan < 0;
4742}
4743
4744static int shrink_one(struct lruvec *lruvec, struct scan_control *sc)
4745{
4746 bool success;
4747 unsigned long scanned = sc->nr_scanned;
4748 unsigned long reclaimed = sc->nr_reclaimed;
4749 struct mem_cgroup *memcg = lruvec_memcg(lruvec);
4750 struct pglist_data *pgdat = lruvec_pgdat(lruvec);
4751
4752 mem_cgroup_calculate_protection(NULL, memcg);
4753
4754 if (mem_cgroup_below_min(NULL, memcg))
4755 return MEMCG_LRU_YOUNG;
4756
4757 if (mem_cgroup_below_low(NULL, memcg)) {
4758 /* see the comment on MEMCG_NR_GENS */
4759 if (READ_ONCE(lruvec->lrugen.seg) != MEMCG_LRU_TAIL)
4760 return MEMCG_LRU_TAIL;
4761
4762 memcg_memory_event(memcg, MEMCG_LOW);
4763 }
4764
4765 success = try_to_shrink_lruvec(lruvec, sc);
4766
4767 shrink_slab(sc->gfp_mask, pgdat->node_id, memcg, sc->priority);
4768
4769 if (!sc->proactive)
4770 vmpressure(sc->gfp_mask, memcg, false, sc->nr_scanned - scanned,
4771 sc->nr_reclaimed - reclaimed);
4772
4773 flush_reclaim_state(sc);
4774
4775 if (success && mem_cgroup_online(memcg))
4776 return MEMCG_LRU_YOUNG;
4777
4778 if (!success && lruvec_is_sizable(lruvec, sc))
4779 return 0;
4780
4781 /* one retry if offlined or too small */
4782 return READ_ONCE(lruvec->lrugen.seg) != MEMCG_LRU_TAIL ?
4783 MEMCG_LRU_TAIL : MEMCG_LRU_YOUNG;
4784}
4785
4786static void shrink_many(struct pglist_data *pgdat, struct scan_control *sc)
4787{
4788 int op;
4789 int gen;
4790 int bin;
4791 int first_bin;
4792 struct lruvec *lruvec;
4793 struct lru_gen_folio *lrugen;
4794 struct mem_cgroup *memcg;
4795 struct hlist_nulls_node *pos;
4796
4797 gen = get_memcg_gen(READ_ONCE(pgdat->memcg_lru.seq));
4798 bin = first_bin = get_random_u32_below(MEMCG_NR_BINS);
4799restart:
4800 op = 0;
4801 memcg = NULL;
4802
4803 rcu_read_lock();
4804
4805 hlist_nulls_for_each_entry_rcu(lrugen, pos, &pgdat->memcg_lru.fifo[gen][bin], list) {
4806 if (op) {
4807 lru_gen_rotate_memcg(lruvec, op);
4808 op = 0;
4809 }
4810
4811 mem_cgroup_put(memcg);
4812 memcg = NULL;
4813
4814 if (gen != READ_ONCE(lrugen->gen))
4815 continue;
4816
4817 lruvec = container_of(lrugen, struct lruvec, lrugen);
4818 memcg = lruvec_memcg(lruvec);
4819
4820 if (!mem_cgroup_tryget(memcg)) {
4821 lru_gen_release_memcg(memcg);
4822 memcg = NULL;
4823 continue;
4824 }
4825
4826 rcu_read_unlock();
4827
4828 op = shrink_one(lruvec, sc);
4829
4830 rcu_read_lock();
4831
4832 if (should_abort_scan(lruvec, sc))
4833 break;
4834 }
4835
4836 rcu_read_unlock();
4837
4838 if (op)
4839 lru_gen_rotate_memcg(lruvec, op);
4840
4841 mem_cgroup_put(memcg);
4842
4843 if (!is_a_nulls(pos))
4844 return;
4845
4846 /* restart if raced with lru_gen_rotate_memcg() */
4847 if (gen != get_nulls_value(pos))
4848 goto restart;
4849
4850 /* try the rest of the bins of the current generation */
4851 bin = get_memcg_bin(bin + 1);
4852 if (bin != first_bin)
4853 goto restart;
4854}
4855
4856static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
4857{
4858 struct blk_plug plug;
4859
4860 VM_WARN_ON_ONCE(root_reclaim(sc));
4861 VM_WARN_ON_ONCE(!sc->may_writepage || !sc->may_unmap);
4862
4863 lru_add_drain();
4864
4865 blk_start_plug(&plug);
4866
4867 set_mm_walk(NULL, sc->proactive);
4868
4869 if (try_to_shrink_lruvec(lruvec, sc))
4870 lru_gen_rotate_memcg(lruvec, MEMCG_LRU_YOUNG);
4871
4872 clear_mm_walk();
4873
4874 blk_finish_plug(&plug);
4875}
4876
4877static void set_initial_priority(struct pglist_data *pgdat, struct scan_control *sc)
4878{
4879 int priority;
4880 unsigned long reclaimable;
4881 struct lruvec *lruvec = mem_cgroup_lruvec(NULL, pgdat);
4882
4883 if (sc->priority != DEF_PRIORITY || sc->nr_to_reclaim < MIN_LRU_BATCH)
4884 return;
4885 /*
4886 * Determine the initial priority based on
4887 * (total >> priority) * reclaimed_to_scanned_ratio = nr_to_reclaim,
4888 * where reclaimed_to_scanned_ratio = inactive / total.
4889 */
4890 reclaimable = node_page_state(pgdat, NR_INACTIVE_FILE);
4891 if (get_swappiness(lruvec, sc))
4892 reclaimable += node_page_state(pgdat, NR_INACTIVE_ANON);
4893
4894 /* round down reclaimable and round up sc->nr_to_reclaim */
4895 priority = fls_long(reclaimable) - 1 - fls_long(sc->nr_to_reclaim - 1);
4896
4897 sc->priority = clamp(priority, 0, DEF_PRIORITY);
4898}
4899
4900static void lru_gen_shrink_node(struct pglist_data *pgdat, struct scan_control *sc)
4901{
4902 struct blk_plug plug;
4903 unsigned long reclaimed = sc->nr_reclaimed;
4904
4905 VM_WARN_ON_ONCE(!root_reclaim(sc));
4906
4907 /*
4908 * Unmapped clean folios are already prioritized. Scanning for more of
4909 * them is likely futile and can cause high reclaim latency when there
4910 * is a large number of memcgs.
4911 */
4912 if (!sc->may_writepage || !sc->may_unmap)
4913 goto done;
4914
4915 lru_add_drain();
4916
4917 blk_start_plug(&plug);
4918
4919 set_mm_walk(pgdat, sc->proactive);
4920
4921 set_initial_priority(pgdat, sc);
4922
4923 if (current_is_kswapd())
4924 sc->nr_reclaimed = 0;
4925
4926 if (mem_cgroup_disabled())
4927 shrink_one(&pgdat->__lruvec, sc);
4928 else
4929 shrink_many(pgdat, sc);
4930
4931 if (current_is_kswapd())
4932 sc->nr_reclaimed += reclaimed;
4933
4934 clear_mm_walk();
4935
4936 blk_finish_plug(&plug);
4937done:
4938 /* kswapd should never fail */
4939 pgdat->kswapd_failures = 0;
4940}
4941
4942/******************************************************************************
4943 * state change
4944 ******************************************************************************/
4945
4946static bool __maybe_unused state_is_valid(struct lruvec *lruvec)
4947{
4948 struct lru_gen_folio *lrugen = &lruvec->lrugen;
4949
4950 if (lrugen->enabled) {
4951 enum lru_list lru;
4952
4953 for_each_evictable_lru(lru) {
4954 if (!list_empty(&lruvec->lists[lru]))
4955 return false;
4956 }
4957 } else {
4958 int gen, type, zone;
4959
4960 for_each_gen_type_zone(gen, type, zone) {
4961 if (!list_empty(&lrugen->folios[gen][type][zone]))
4962 return false;
4963 }
4964 }
4965
4966 return true;
4967}
4968
4969static bool fill_evictable(struct lruvec *lruvec)
4970{
4971 enum lru_list lru;
4972 int remaining = MAX_LRU_BATCH;
4973
4974 for_each_evictable_lru(lru) {
4975 int type = is_file_lru(lru);
4976 bool active = is_active_lru(lru);
4977 struct list_head *head = &lruvec->lists[lru];
4978
4979 while (!list_empty(head)) {
4980 bool success;
4981 struct folio *folio = lru_to_folio(head);
4982
4983 VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio);
4984 VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio) != active, folio);
4985 VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio);
4986 VM_WARN_ON_ONCE_FOLIO(folio_lru_gen(folio) != -1, folio);
4987
4988 lruvec_del_folio(lruvec, folio);
4989 success = lru_gen_add_folio(lruvec, folio, false);
4990 VM_WARN_ON_ONCE(!success);
4991
4992 if (!--remaining)
4993 return false;
4994 }
4995 }
4996
4997 return true;
4998}
4999
5000static bool drain_evictable(struct lruvec *lruvec)
5001{
5002 int gen, type, zone;
5003 int remaining = MAX_LRU_BATCH;
5004
5005 for_each_gen_type_zone(gen, type, zone) {
5006 struct list_head *head = &lruvec->lrugen.folios[gen][type][zone];
5007
5008 while (!list_empty(head)) {
5009 bool success;
5010 struct folio *folio = lru_to_folio(head);
5011
5012 VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio);
5013 VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio), folio);
5014 VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio);
5015 VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio) != zone, folio);
5016
5017 success = lru_gen_del_folio(lruvec, folio, false);
5018 VM_WARN_ON_ONCE(!success);
5019 lruvec_add_folio(lruvec, folio);
5020
5021 if (!--remaining)
5022 return false;
5023 }
5024 }
5025
5026 return true;
5027}
5028
5029static void lru_gen_change_state(bool enabled)
5030{
5031 static DEFINE_MUTEX(state_mutex);
5032
5033 struct mem_cgroup *memcg;
5034
5035 cgroup_lock();
5036 cpus_read_lock();
5037 get_online_mems();
5038 mutex_lock(&state_mutex);
5039
5040 if (enabled == lru_gen_enabled())
5041 goto unlock;
5042
5043 if (enabled)
5044 static_branch_enable_cpuslocked(&lru_gen_caps[LRU_GEN_CORE]);
5045 else
5046 static_branch_disable_cpuslocked(&lru_gen_caps[LRU_GEN_CORE]);
5047
5048 memcg = mem_cgroup_iter(NULL, NULL, NULL);
5049 do {
5050 int nid;
5051
5052 for_each_node(nid) {
5053 struct lruvec *lruvec = get_lruvec(memcg, nid);
5054
5055 spin_lock_irq(&lruvec->lru_lock);
5056
5057 VM_WARN_ON_ONCE(!seq_is_valid(lruvec));
5058 VM_WARN_ON_ONCE(!state_is_valid(lruvec));
5059
5060 lruvec->lrugen.enabled = enabled;
5061
5062 while (!(enabled ? fill_evictable(lruvec) : drain_evictable(lruvec))) {
5063 spin_unlock_irq(&lruvec->lru_lock);
5064 cond_resched();
5065 spin_lock_irq(&lruvec->lru_lock);
5066 }
5067
5068 spin_unlock_irq(&lruvec->lru_lock);
5069 }
5070
5071 cond_resched();
5072 } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)));
5073unlock:
5074 mutex_unlock(&state_mutex);
5075 put_online_mems();
5076 cpus_read_unlock();
5077 cgroup_unlock();
5078}
5079
5080/******************************************************************************
5081 * sysfs interface
5082 ******************************************************************************/
5083
5084static ssize_t min_ttl_ms_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
5085{
5086 return sysfs_emit(buf, "%u\n", jiffies_to_msecs(READ_ONCE(lru_gen_min_ttl)));
5087}
5088
5089/* see Documentation/admin-guide/mm/multigen_lru.rst for details */
5090static ssize_t min_ttl_ms_store(struct kobject *kobj, struct kobj_attribute *attr,
5091 const char *buf, size_t len)
5092{
5093 unsigned int msecs;
5094
5095 if (kstrtouint(buf, 0, &msecs))
5096 return -EINVAL;
5097
5098 WRITE_ONCE(lru_gen_min_ttl, msecs_to_jiffies(msecs));
5099
5100 return len;
5101}
5102
5103static struct kobj_attribute lru_gen_min_ttl_attr = __ATTR_RW(min_ttl_ms);
5104
5105static ssize_t enabled_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
5106{
5107 unsigned int caps = 0;
5108
5109 if (get_cap(LRU_GEN_CORE))
5110 caps |= BIT(LRU_GEN_CORE);
5111
5112 if (should_walk_mmu())
5113 caps |= BIT(LRU_GEN_MM_WALK);
5114
5115 if (should_clear_pmd_young())
5116 caps |= BIT(LRU_GEN_NONLEAF_YOUNG);
5117
5118 return sysfs_emit(buf, "0x%04x\n", caps);
5119}
5120
5121/* see Documentation/admin-guide/mm/multigen_lru.rst for details */
5122static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
5123 const char *buf, size_t len)
5124{
5125 int i;
5126 unsigned int caps;
5127
5128 if (tolower(*buf) == 'n')
5129 caps = 0;
5130 else if (tolower(*buf) == 'y')
5131 caps = -1;
5132 else if (kstrtouint(buf, 0, &caps))
5133 return -EINVAL;
5134
5135 for (i = 0; i < NR_LRU_GEN_CAPS; i++) {
5136 bool enabled = caps & BIT(i);
5137
5138 if (i == LRU_GEN_CORE)
5139 lru_gen_change_state(enabled);
5140 else if (enabled)
5141 static_branch_enable(&lru_gen_caps[i]);
5142 else
5143 static_branch_disable(&lru_gen_caps[i]);
5144 }
5145
5146 return len;
5147}
5148
5149static struct kobj_attribute lru_gen_enabled_attr = __ATTR_RW(enabled);
5150
5151static struct attribute *lru_gen_attrs[] = {
5152 &lru_gen_min_ttl_attr.attr,
5153 &lru_gen_enabled_attr.attr,
5154 NULL
5155};
5156
5157static const struct attribute_group lru_gen_attr_group = {
5158 .name = "lru_gen",
5159 .attrs = lru_gen_attrs,
5160};
5161
5162/******************************************************************************
5163 * debugfs interface
5164 ******************************************************************************/
5165
5166static void *lru_gen_seq_start(struct seq_file *m, loff_t *pos)
5167{
5168 struct mem_cgroup *memcg;
5169 loff_t nr_to_skip = *pos;
5170
5171 m->private = kvmalloc(PATH_MAX, GFP_KERNEL);
5172 if (!m->private)
5173 return ERR_PTR(-ENOMEM);
5174
5175 memcg = mem_cgroup_iter(NULL, NULL, NULL);
5176 do {
5177 int nid;
5178
5179 for_each_node_state(nid, N_MEMORY) {
5180 if (!nr_to_skip--)
5181 return get_lruvec(memcg, nid);
5182 }
5183 } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)));
5184
5185 return NULL;
5186}
5187
5188static void lru_gen_seq_stop(struct seq_file *m, void *v)
5189{
5190 if (!IS_ERR_OR_NULL(v))
5191 mem_cgroup_iter_break(NULL, lruvec_memcg(v));
5192
5193 kvfree(m->private);
5194 m->private = NULL;
5195}
5196
5197static void *lru_gen_seq_next(struct seq_file *m, void *v, loff_t *pos)
5198{
5199 int nid = lruvec_pgdat(v)->node_id;
5200 struct mem_cgroup *memcg = lruvec_memcg(v);
5201
5202 ++*pos;
5203
5204 nid = next_memory_node(nid);
5205 if (nid == MAX_NUMNODES) {
5206 memcg = mem_cgroup_iter(NULL, memcg, NULL);
5207 if (!memcg)
5208 return NULL;
5209
5210 nid = first_memory_node;
5211 }
5212
5213 return get_lruvec(memcg, nid);
5214}
5215
5216static void lru_gen_seq_show_full(struct seq_file *m, struct lruvec *lruvec,
5217 unsigned long max_seq, unsigned long *min_seq,
5218 unsigned long seq)
5219{
5220 int i;
5221 int type, tier;
5222 int hist = lru_hist_from_seq(seq);
5223 struct lru_gen_folio *lrugen = &lruvec->lrugen;
5224 struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
5225
5226 for (tier = 0; tier < MAX_NR_TIERS; tier++) {
5227 seq_printf(m, " %10d", tier);
5228 for (type = 0; type < ANON_AND_FILE; type++) {
5229 const char *s = " ";
5230 unsigned long n[3] = {};
5231
5232 if (seq == max_seq) {
5233 s = "RT ";
5234 n[0] = READ_ONCE(lrugen->avg_refaulted[type][tier]);
5235 n[1] = READ_ONCE(lrugen->avg_total[type][tier]);
5236 } else if (seq == min_seq[type] || NR_HIST_GENS > 1) {
5237 s = "rep";
5238 n[0] = atomic_long_read(&lrugen->refaulted[hist][type][tier]);
5239 n[1] = atomic_long_read(&lrugen->evicted[hist][type][tier]);
5240 if (tier)
5241 n[2] = READ_ONCE(lrugen->protected[hist][type][tier - 1]);
5242 }
5243
5244 for (i = 0; i < 3; i++)
5245 seq_printf(m, " %10lu%c", n[i], s[i]);
5246 }
5247 seq_putc(m, '\n');
5248 }
5249
5250 if (!mm_state)
5251 return;
5252
5253 seq_puts(m, " ");
5254 for (i = 0; i < NR_MM_STATS; i++) {
5255 const char *s = " ";
5256 unsigned long n = 0;
5257
5258 if (seq == max_seq && NR_HIST_GENS == 1) {
5259 s = "LOYNFA";
5260 n = READ_ONCE(mm_state->stats[hist][i]);
5261 } else if (seq != max_seq && NR_HIST_GENS > 1) {
5262 s = "loynfa";
5263 n = READ_ONCE(mm_state->stats[hist][i]);
5264 }
5265
5266 seq_printf(m, " %10lu%c", n, s[i]);
5267 }
5268 seq_putc(m, '\n');
5269}
5270
5271/* see Documentation/admin-guide/mm/multigen_lru.rst for details */
5272static int lru_gen_seq_show(struct seq_file *m, void *v)
5273{
5274 unsigned long seq;
5275 bool full = !debugfs_real_fops(m->file)->write;
5276 struct lruvec *lruvec = v;
5277 struct lru_gen_folio *lrugen = &lruvec->lrugen;
5278 int nid = lruvec_pgdat(lruvec)->node_id;
5279 struct mem_cgroup *memcg = lruvec_memcg(lruvec);
5280 DEFINE_MAX_SEQ(lruvec);
5281 DEFINE_MIN_SEQ(lruvec);
5282
5283 if (nid == first_memory_node) {
5284 const char *path = memcg ? m->private : "";
5285
5286#ifdef CONFIG_MEMCG
5287 if (memcg)
5288 cgroup_path(memcg->css.cgroup, m->private, PATH_MAX);
5289#endif
5290 seq_printf(m, "memcg %5hu %s\n", mem_cgroup_id(memcg), path);
5291 }
5292
5293 seq_printf(m, " node %5d\n", nid);
5294
5295 if (!full)
5296 seq = min_seq[LRU_GEN_ANON];
5297 else if (max_seq >= MAX_NR_GENS)
5298 seq = max_seq - MAX_NR_GENS + 1;
5299 else
5300 seq = 0;
5301
5302 for (; seq <= max_seq; seq++) {
5303 int type, zone;
5304 int gen = lru_gen_from_seq(seq);
5305 unsigned long birth = READ_ONCE(lruvec->lrugen.timestamps[gen]);
5306
5307 seq_printf(m, " %10lu %10u", seq, jiffies_to_msecs(jiffies - birth));
5308
5309 for (type = 0; type < ANON_AND_FILE; type++) {
5310 unsigned long size = 0;
5311 char mark = full && seq < min_seq[type] ? 'x' : ' ';
5312
5313 for (zone = 0; zone < MAX_NR_ZONES; zone++)
5314 size += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L);
5315
5316 seq_printf(m, " %10lu%c", size, mark);
5317 }
5318
5319 seq_putc(m, '\n');
5320
5321 if (full)
5322 lru_gen_seq_show_full(m, lruvec, max_seq, min_seq, seq);
5323 }
5324
5325 return 0;
5326}
5327
5328static const struct seq_operations lru_gen_seq_ops = {
5329 .start = lru_gen_seq_start,
5330 .stop = lru_gen_seq_stop,
5331 .next = lru_gen_seq_next,
5332 .show = lru_gen_seq_show,
5333};
5334
5335static int run_aging(struct lruvec *lruvec, unsigned long seq, struct scan_control *sc,
5336 bool can_swap, bool force_scan)
5337{
5338 DEFINE_MAX_SEQ(lruvec);
5339 DEFINE_MIN_SEQ(lruvec);
5340
5341 if (seq < max_seq)
5342 return 0;
5343
5344 if (seq > max_seq)
5345 return -EINVAL;
5346
5347 if (!force_scan && min_seq[!can_swap] + MAX_NR_GENS - 1 <= max_seq)
5348 return -ERANGE;
5349
5350 try_to_inc_max_seq(lruvec, max_seq, sc, can_swap, force_scan);
5351
5352 return 0;
5353}
5354
5355static int run_eviction(struct lruvec *lruvec, unsigned long seq, struct scan_control *sc,
5356 int swappiness, unsigned long nr_to_reclaim)
5357{
5358 DEFINE_MAX_SEQ(lruvec);
5359
5360 if (seq + MIN_NR_GENS > max_seq)
5361 return -EINVAL;
5362
5363 sc->nr_reclaimed = 0;
5364
5365 while (!signal_pending(current)) {
5366 DEFINE_MIN_SEQ(lruvec);
5367
5368 if (seq < min_seq[!swappiness])
5369 return 0;
5370
5371 if (sc->nr_reclaimed >= nr_to_reclaim)
5372 return 0;
5373
5374 if (!evict_folios(lruvec, sc, swappiness))
5375 return 0;
5376
5377 cond_resched();
5378 }
5379
5380 return -EINTR;
5381}
5382
5383static int run_cmd(char cmd, int memcg_id, int nid, unsigned long seq,
5384 struct scan_control *sc, int swappiness, unsigned long opt)
5385{
5386 struct lruvec *lruvec;
5387 int err = -EINVAL;
5388 struct mem_cgroup *memcg = NULL;
5389
5390 if (nid < 0 || nid >= MAX_NUMNODES || !node_state(nid, N_MEMORY))
5391 return -EINVAL;
5392
5393 if (!mem_cgroup_disabled()) {
5394 rcu_read_lock();
5395
5396 memcg = mem_cgroup_from_id(memcg_id);
5397 if (!mem_cgroup_tryget(memcg))
5398 memcg = NULL;
5399
5400 rcu_read_unlock();
5401
5402 if (!memcg)
5403 return -EINVAL;
5404 }
5405
5406 if (memcg_id != mem_cgroup_id(memcg))
5407 goto done;
5408
5409 lruvec = get_lruvec(memcg, nid);
5410
5411 if (swappiness < 0)
5412 swappiness = get_swappiness(lruvec, sc);
5413 else if (swappiness > 200)
5414 goto done;
5415
5416 switch (cmd) {
5417 case '+':
5418 err = run_aging(lruvec, seq, sc, swappiness, opt);
5419 break;
5420 case '-':
5421 err = run_eviction(lruvec, seq, sc, swappiness, opt);
5422 break;
5423 }
5424done:
5425 mem_cgroup_put(memcg);
5426
5427 return err;
5428}
5429
5430/* see Documentation/admin-guide/mm/multigen_lru.rst for details */
5431static ssize_t lru_gen_seq_write(struct file *file, const char __user *src,
5432 size_t len, loff_t *pos)
5433{
5434 void *buf;
5435 char *cur, *next;
5436 unsigned int flags;
5437 struct blk_plug plug;
5438 int err = -EINVAL;
5439 struct scan_control sc = {
5440 .may_writepage = true,
5441 .may_unmap = true,
5442 .may_swap = true,
5443 .reclaim_idx = MAX_NR_ZONES - 1,
5444 .gfp_mask = GFP_KERNEL,
5445 };
5446
5447 buf = kvmalloc(len + 1, GFP_KERNEL);
5448 if (!buf)
5449 return -ENOMEM;
5450
5451 if (copy_from_user(buf, src, len)) {
5452 kvfree(buf);
5453 return -EFAULT;
5454 }
5455
5456 set_task_reclaim_state(current, &sc.reclaim_state);
5457 flags = memalloc_noreclaim_save();
5458 blk_start_plug(&plug);
5459 if (!set_mm_walk(NULL, true)) {
5460 err = -ENOMEM;
5461 goto done;
5462 }
5463
5464 next = buf;
5465 next[len] = '\0';
5466
5467 while ((cur = strsep(&next, ",;\n"))) {
5468 int n;
5469 int end;
5470 char cmd;
5471 unsigned int memcg_id;
5472 unsigned int nid;
5473 unsigned long seq;
5474 unsigned int swappiness = -1;
5475 unsigned long opt = -1;
5476
5477 cur = skip_spaces(cur);
5478 if (!*cur)
5479 continue;
5480
5481 n = sscanf(cur, "%c %u %u %lu %n %u %n %lu %n", &cmd, &memcg_id, &nid,
5482 &seq, &end, &swappiness, &end, &opt, &end);
5483 if (n < 4 || cur[end]) {
5484 err = -EINVAL;
5485 break;
5486 }
5487
5488 err = run_cmd(cmd, memcg_id, nid, seq, &sc, swappiness, opt);
5489 if (err)
5490 break;
5491 }
5492done:
5493 clear_mm_walk();
5494 blk_finish_plug(&plug);
5495 memalloc_noreclaim_restore(flags);
5496 set_task_reclaim_state(current, NULL);
5497
5498 kvfree(buf);
5499
5500 return err ? : len;
5501}
5502
5503static int lru_gen_seq_open(struct inode *inode, struct file *file)
5504{
5505 return seq_open(file, &lru_gen_seq_ops);
5506}
5507
5508static const struct file_operations lru_gen_rw_fops = {
5509 .open = lru_gen_seq_open,
5510 .read = seq_read,
5511 .write = lru_gen_seq_write,
5512 .llseek = seq_lseek,
5513 .release = seq_release,
5514};
5515
5516static const struct file_operations lru_gen_ro_fops = {
5517 .open = lru_gen_seq_open,
5518 .read = seq_read,
5519 .llseek = seq_lseek,
5520 .release = seq_release,
5521};
5522
5523/******************************************************************************
5524 * initialization
5525 ******************************************************************************/
5526
5527void lru_gen_init_pgdat(struct pglist_data *pgdat)
5528{
5529 int i, j;
5530
5531 spin_lock_init(&pgdat->memcg_lru.lock);
5532
5533 for (i = 0; i < MEMCG_NR_GENS; i++) {
5534 for (j = 0; j < MEMCG_NR_BINS; j++)
5535 INIT_HLIST_NULLS_HEAD(&pgdat->memcg_lru.fifo[i][j], i);
5536 }
5537}
5538
5539void lru_gen_init_lruvec(struct lruvec *lruvec)
5540{
5541 int i;
5542 int gen, type, zone;
5543 struct lru_gen_folio *lrugen = &lruvec->lrugen;
5544 struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
5545
5546 lrugen->max_seq = MIN_NR_GENS + 1;
5547 lrugen->enabled = lru_gen_enabled();
5548
5549 for (i = 0; i <= MIN_NR_GENS + 1; i++)
5550 lrugen->timestamps[i] = jiffies;
5551
5552 for_each_gen_type_zone(gen, type, zone)
5553 INIT_LIST_HEAD(&lrugen->folios[gen][type][zone]);
5554
5555 if (mm_state)
5556 mm_state->seq = MIN_NR_GENS;
5557}
5558
5559#ifdef CONFIG_MEMCG
5560
5561void lru_gen_init_memcg(struct mem_cgroup *memcg)
5562{
5563 struct lru_gen_mm_list *mm_list = get_mm_list(memcg);
5564
5565 if (!mm_list)
5566 return;
5567
5568 INIT_LIST_HEAD(&mm_list->fifo);
5569 spin_lock_init(&mm_list->lock);
5570}
5571
5572void lru_gen_exit_memcg(struct mem_cgroup *memcg)
5573{
5574 int i;
5575 int nid;
5576 struct lru_gen_mm_list *mm_list = get_mm_list(memcg);
5577
5578 VM_WARN_ON_ONCE(mm_list && !list_empty(&mm_list->fifo));
5579
5580 for_each_node(nid) {
5581 struct lruvec *lruvec = get_lruvec(memcg, nid);
5582 struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
5583
5584 VM_WARN_ON_ONCE(memchr_inv(lruvec->lrugen.nr_pages, 0,
5585 sizeof(lruvec->lrugen.nr_pages)));
5586
5587 lruvec->lrugen.list.next = LIST_POISON1;
5588
5589 if (!mm_state)
5590 continue;
5591
5592 for (i = 0; i < NR_BLOOM_FILTERS; i++) {
5593 bitmap_free(mm_state->filters[i]);
5594 mm_state->filters[i] = NULL;
5595 }
5596 }
5597}
5598
5599#endif /* CONFIG_MEMCG */
5600
5601static int __init init_lru_gen(void)
5602{
5603 BUILD_BUG_ON(MIN_NR_GENS + 1 >= MAX_NR_GENS);
5604 BUILD_BUG_ON(BIT(LRU_GEN_WIDTH) <= MAX_NR_GENS);
5605
5606 if (sysfs_create_group(mm_kobj, &lru_gen_attr_group))
5607 pr_err("lru_gen: failed to create sysfs group\n");
5608
5609 debugfs_create_file("lru_gen", 0644, NULL, NULL, &lru_gen_rw_fops);
5610 debugfs_create_file("lru_gen_full", 0444, NULL, NULL, &lru_gen_ro_fops);
5611
5612 return 0;
5613};
5614late_initcall(init_lru_gen);
5615
5616#else /* !CONFIG_LRU_GEN */
5617
5618static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc)
5619{
5620 BUILD_BUG();
5621}
5622
5623static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
5624{
5625 BUILD_BUG();
5626}
5627
5628static void lru_gen_shrink_node(struct pglist_data *pgdat, struct scan_control *sc)
5629{
5630 BUILD_BUG();
5631}
5632
5633#endif /* CONFIG_LRU_GEN */
5634
5635static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
5636{
5637 unsigned long nr[NR_LRU_LISTS];
5638 unsigned long targets[NR_LRU_LISTS];
5639 unsigned long nr_to_scan;
5640 enum lru_list lru;
5641 unsigned long nr_reclaimed = 0;
5642 unsigned long nr_to_reclaim = sc->nr_to_reclaim;
5643 bool proportional_reclaim;
5644 struct blk_plug plug;
5645
5646 if (lru_gen_enabled() && !root_reclaim(sc)) {
5647 lru_gen_shrink_lruvec(lruvec, sc);
5648 return;
5649 }
5650
5651 get_scan_count(lruvec, sc, nr);
5652
5653 /* Record the original scan target for proportional adjustments later */
5654 memcpy(targets, nr, sizeof(nr));
5655
5656 /*
5657 * Global reclaiming within direct reclaim at DEF_PRIORITY is a normal
5658 * event that can occur when there is little memory pressure e.g.
5659 * multiple streaming readers/writers. Hence, we do not abort scanning
5660 * when the requested number of pages are reclaimed when scanning at
5661 * DEF_PRIORITY on the assumption that the fact we are direct
5662 * reclaiming implies that kswapd is not keeping up and it is best to
5663 * do a batch of work at once. For memcg reclaim one check is made to
5664 * abort proportional reclaim if either the file or anon lru has already
5665 * dropped to zero at the first pass.
5666 */
5667 proportional_reclaim = (!cgroup_reclaim(sc) && !current_is_kswapd() &&
5668 sc->priority == DEF_PRIORITY);
5669
5670 blk_start_plug(&plug);
5671 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
5672 nr[LRU_INACTIVE_FILE]) {
5673 unsigned long nr_anon, nr_file, percentage;
5674 unsigned long nr_scanned;
5675
5676 for_each_evictable_lru(lru) {
5677 if (nr[lru]) {
5678 nr_to_scan = min(nr[lru], SWAP_CLUSTER_MAX);
5679 nr[lru] -= nr_to_scan;
5680
5681 nr_reclaimed += shrink_list(lru, nr_to_scan,
5682 lruvec, sc);
5683 }
5684 }
5685
5686 cond_resched();
5687
5688 if (nr_reclaimed < nr_to_reclaim || proportional_reclaim)
5689 continue;
5690
5691 /*
5692 * For kswapd and memcg, reclaim at least the number of pages
5693 * requested. Ensure that the anon and file LRUs are scanned
5694 * proportionally what was requested by get_scan_count(). We
5695 * stop reclaiming one LRU and reduce the amount scanning
5696 * proportional to the original scan target.
5697 */
5698 nr_file = nr[LRU_INACTIVE_FILE] + nr[LRU_ACTIVE_FILE];
5699 nr_anon = nr[LRU_INACTIVE_ANON] + nr[LRU_ACTIVE_ANON];
5700
5701 /*
5702 * It's just vindictive to attack the larger once the smaller
5703 * has gone to zero. And given the way we stop scanning the
5704 * smaller below, this makes sure that we only make one nudge
5705 * towards proportionality once we've got nr_to_reclaim.
5706 */
5707 if (!nr_file || !nr_anon)
5708 break;
5709
5710 if (nr_file > nr_anon) {
5711 unsigned long scan_target = targets[LRU_INACTIVE_ANON] +
5712 targets[LRU_ACTIVE_ANON] + 1;
5713 lru = LRU_BASE;
5714 percentage = nr_anon * 100 / scan_target;
5715 } else {
5716 unsigned long scan_target = targets[LRU_INACTIVE_FILE] +
5717 targets[LRU_ACTIVE_FILE] + 1;
5718 lru = LRU_FILE;
5719 percentage = nr_file * 100 / scan_target;
5720 }
5721
5722 /* Stop scanning the smaller of the LRU */
5723 nr[lru] = 0;
5724 nr[lru + LRU_ACTIVE] = 0;
5725
5726 /*
5727 * Recalculate the other LRU scan count based on its original
5728 * scan target and the percentage scanning already complete
5729 */
5730 lru = (lru == LRU_FILE) ? LRU_BASE : LRU_FILE;
5731 nr_scanned = targets[lru] - nr[lru];
5732 nr[lru] = targets[lru] * (100 - percentage) / 100;
5733 nr[lru] -= min(nr[lru], nr_scanned);
5734
5735 lru += LRU_ACTIVE;
5736 nr_scanned = targets[lru] - nr[lru];
5737 nr[lru] = targets[lru] * (100 - percentage) / 100;
5738 nr[lru] -= min(nr[lru], nr_scanned);
5739 }
5740 blk_finish_plug(&plug);
5741 sc->nr_reclaimed += nr_reclaimed;
5742
5743 /*
5744 * Even if we did not try to evict anon pages at all, we want to
5745 * rebalance the anon lru active/inactive ratio.
5746 */
5747 if (can_age_anon_pages(lruvec_pgdat(lruvec), sc) &&
5748 inactive_is_low(lruvec, LRU_INACTIVE_ANON))
5749 shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
5750 sc, LRU_ACTIVE_ANON);
5751}
5752
5753/* Use reclaim/compaction for costly allocs or under memory pressure */
5754static bool in_reclaim_compaction(struct scan_control *sc)
5755{
5756 if (gfp_compaction_allowed(sc->gfp_mask) && sc->order &&
5757 (sc->order > PAGE_ALLOC_COSTLY_ORDER ||
5758 sc->priority < DEF_PRIORITY - 2))
5759 return true;
5760
5761 return false;
5762}
5763
5764/*
5765 * Reclaim/compaction is used for high-order allocation requests. It reclaims
5766 * order-0 pages before compacting the zone. should_continue_reclaim() returns
5767 * true if more pages should be reclaimed such that when the page allocator
5768 * calls try_to_compact_pages() that it will have enough free pages to succeed.
5769 * It will give up earlier than that if there is difficulty reclaiming pages.
5770 */
5771static inline bool should_continue_reclaim(struct pglist_data *pgdat,
5772 unsigned long nr_reclaimed,
5773 struct scan_control *sc)
5774{
5775 unsigned long pages_for_compaction;
5776 unsigned long inactive_lru_pages;
5777 int z;
5778
5779 /* If not in reclaim/compaction mode, stop */
5780 if (!in_reclaim_compaction(sc))
5781 return false;
5782
5783 /*
5784 * Stop if we failed to reclaim any pages from the last SWAP_CLUSTER_MAX
5785 * number of pages that were scanned. This will return to the caller
5786 * with the risk reclaim/compaction and the resulting allocation attempt
5787 * fails. In the past we have tried harder for __GFP_RETRY_MAYFAIL
5788 * allocations through requiring that the full LRU list has been scanned
5789 * first, by assuming that zero delta of sc->nr_scanned means full LRU
5790 * scan, but that approximation was wrong, and there were corner cases
5791 * where always a non-zero amount of pages were scanned.
5792 */
5793 if (!nr_reclaimed)
5794 return false;
5795
5796 /* If compaction would go ahead or the allocation would succeed, stop */
5797 for (z = 0; z <= sc->reclaim_idx; z++) {
5798 struct zone *zone = &pgdat->node_zones[z];
5799 if (!managed_zone(zone))
5800 continue;
5801
5802 /* Allocation can already succeed, nothing to do */
5803 if (zone_watermark_ok(zone, sc->order, min_wmark_pages(zone),
5804 sc->reclaim_idx, 0))
5805 return false;
5806
5807 if (compaction_suitable(zone, sc->order, sc->reclaim_idx))
5808 return false;
5809 }
5810
5811 /*
5812 * If we have not reclaimed enough pages for compaction and the
5813 * inactive lists are large enough, continue reclaiming
5814 */
5815 pages_for_compaction = compact_gap(sc->order);
5816 inactive_lru_pages = node_page_state(pgdat, NR_INACTIVE_FILE);
5817 if (can_reclaim_anon_pages(NULL, pgdat->node_id, sc))
5818 inactive_lru_pages += node_page_state(pgdat, NR_INACTIVE_ANON);
5819
5820 return inactive_lru_pages > pages_for_compaction;
5821}
5822
5823static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc)
5824{
5825 struct mem_cgroup *target_memcg = sc->target_mem_cgroup;
5826 struct mem_cgroup *memcg;
5827
5828 memcg = mem_cgroup_iter(target_memcg, NULL, NULL);
5829 do {
5830 struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
5831 unsigned long reclaimed;
5832 unsigned long scanned;
5833
5834 /*
5835 * This loop can become CPU-bound when target memcgs
5836 * aren't eligible for reclaim - either because they
5837 * don't have any reclaimable pages, or because their
5838 * memory is explicitly protected. Avoid soft lockups.
5839 */
5840 cond_resched();
5841
5842 mem_cgroup_calculate_protection(target_memcg, memcg);
5843
5844 if (mem_cgroup_below_min(target_memcg, memcg)) {
5845 /*
5846 * Hard protection.
5847 * If there is no reclaimable memory, OOM.
5848 */
5849 continue;
5850 } else if (mem_cgroup_below_low(target_memcg, memcg)) {
5851 /*
5852 * Soft protection.
5853 * Respect the protection only as long as
5854 * there is an unprotected supply
5855 * of reclaimable memory from other cgroups.
5856 */
5857 if (!sc->memcg_low_reclaim) {
5858 sc->memcg_low_skipped = 1;
5859 continue;
5860 }
5861 memcg_memory_event(memcg, MEMCG_LOW);
5862 }
5863
5864 reclaimed = sc->nr_reclaimed;
5865 scanned = sc->nr_scanned;
5866
5867 shrink_lruvec(lruvec, sc);
5868
5869 shrink_slab(sc->gfp_mask, pgdat->node_id, memcg,
5870 sc->priority);
5871
5872 /* Record the group's reclaim efficiency */
5873 if (!sc->proactive)
5874 vmpressure(sc->gfp_mask, memcg, false,
5875 sc->nr_scanned - scanned,
5876 sc->nr_reclaimed - reclaimed);
5877
5878 } while ((memcg = mem_cgroup_iter(target_memcg, memcg, NULL)));
5879}
5880
5881static void shrink_node(pg_data_t *pgdat, struct scan_control *sc)
5882{
5883 unsigned long nr_reclaimed, nr_scanned, nr_node_reclaimed;
5884 struct lruvec *target_lruvec;
5885 bool reclaimable = false;
5886
5887 if (lru_gen_enabled() && root_reclaim(sc)) {
5888 lru_gen_shrink_node(pgdat, sc);
5889 return;
5890 }
5891
5892 target_lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup, pgdat);
5893
5894again:
5895 memset(&sc->nr, 0, sizeof(sc->nr));
5896
5897 nr_reclaimed = sc->nr_reclaimed;
5898 nr_scanned = sc->nr_scanned;
5899
5900 prepare_scan_control(pgdat, sc);
5901
5902 shrink_node_memcgs(pgdat, sc);
5903
5904 flush_reclaim_state(sc);
5905
5906 nr_node_reclaimed = sc->nr_reclaimed - nr_reclaimed;
5907
5908 /* Record the subtree's reclaim efficiency */
5909 if (!sc->proactive)
5910 vmpressure(sc->gfp_mask, sc->target_mem_cgroup, true,
5911 sc->nr_scanned - nr_scanned, nr_node_reclaimed);
5912
5913 if (nr_node_reclaimed)
5914 reclaimable = true;
5915
5916 if (current_is_kswapd()) {
5917 /*
5918 * If reclaim is isolating dirty pages under writeback,
5919 * it implies that the long-lived page allocation rate
5920 * is exceeding the page laundering rate. Either the
5921 * global limits are not being effective at throttling
5922 * processes due to the page distribution throughout
5923 * zones or there is heavy usage of a slow backing
5924 * device. The only option is to throttle from reclaim
5925 * context which is not ideal as there is no guarantee
5926 * the dirtying process is throttled in the same way
5927 * balance_dirty_pages() manages.
5928 *
5929 * Once a node is flagged PGDAT_WRITEBACK, kswapd will
5930 * count the number of pages under pages flagged for
5931 * immediate reclaim and stall if any are encountered
5932 * in the nr_immediate check below.
5933 */
5934 if (sc->nr.writeback && sc->nr.writeback == sc->nr.taken)
5935 set_bit(PGDAT_WRITEBACK, &pgdat->flags);
5936
5937 /* Allow kswapd to start writing pages during reclaim.*/
5938 if (sc->nr.unqueued_dirty == sc->nr.file_taken)
5939 set_bit(PGDAT_DIRTY, &pgdat->flags);
5940
5941 /*
5942 * If kswapd scans pages marked for immediate
5943 * reclaim and under writeback (nr_immediate), it
5944 * implies that pages are cycling through the LRU
5945 * faster than they are written so forcibly stall
5946 * until some pages complete writeback.
5947 */
5948 if (sc->nr.immediate)
5949 reclaim_throttle(pgdat, VMSCAN_THROTTLE_WRITEBACK);
5950 }
5951
5952 /*
5953 * Tag a node/memcg as congested if all the dirty pages were marked
5954 * for writeback and immediate reclaim (counted in nr.congested).
5955 *
5956 * Legacy memcg will stall in page writeback so avoid forcibly
5957 * stalling in reclaim_throttle().
5958 */
5959 if (sc->nr.dirty && sc->nr.dirty == sc->nr.congested) {
5960 if (cgroup_reclaim(sc) && writeback_throttling_sane(sc))
5961 set_bit(LRUVEC_CGROUP_CONGESTED, &target_lruvec->flags);
5962
5963 if (current_is_kswapd())
5964 set_bit(LRUVEC_NODE_CONGESTED, &target_lruvec->flags);
5965 }
5966
5967 /*
5968 * Stall direct reclaim for IO completions if the lruvec is
5969 * node is congested. Allow kswapd to continue until it
5970 * starts encountering unqueued dirty pages or cycling through
5971 * the LRU too quickly.
5972 */
5973 if (!current_is_kswapd() && current_may_throttle() &&
5974 !sc->hibernation_mode &&
5975 (test_bit(LRUVEC_CGROUP_CONGESTED, &target_lruvec->flags) ||
5976 test_bit(LRUVEC_NODE_CONGESTED, &target_lruvec->flags)))
5977 reclaim_throttle(pgdat, VMSCAN_THROTTLE_CONGESTED);
5978
5979 if (should_continue_reclaim(pgdat, nr_node_reclaimed, sc))
5980 goto again;
5981
5982 /*
5983 * Kswapd gives up on balancing particular nodes after too
5984 * many failures to reclaim anything from them and goes to
5985 * sleep. On reclaim progress, reset the failure counter. A
5986 * successful direct reclaim run will revive a dormant kswapd.
5987 */
5988 if (reclaimable)
5989 pgdat->kswapd_failures = 0;
5990}
5991
5992/*
5993 * Returns true if compaction should go ahead for a costly-order request, or
5994 * the allocation would already succeed without compaction. Return false if we
5995 * should reclaim first.
5996 */
5997static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
5998{
5999 unsigned long watermark;
6000
6001 if (!gfp_compaction_allowed(sc->gfp_mask))
6002 return false;
6003
6004 /* Allocation can already succeed, nothing to do */
6005 if (zone_watermark_ok(zone, sc->order, min_wmark_pages(zone),
6006 sc->reclaim_idx, 0))
6007 return true;
6008
6009 /* Compaction cannot yet proceed. Do reclaim. */
6010 if (!compaction_suitable(zone, sc->order, sc->reclaim_idx))
6011 return false;
6012
6013 /*
6014 * Compaction is already possible, but it takes time to run and there
6015 * are potentially other callers using the pages just freed. So proceed
6016 * with reclaim to make a buffer of free pages available to give
6017 * compaction a reasonable chance of completing and allocating the page.
6018 * Note that we won't actually reclaim the whole buffer in one attempt
6019 * as the target watermark in should_continue_reclaim() is lower. But if
6020 * we are already above the high+gap watermark, don't reclaim at all.
6021 */
6022 watermark = high_wmark_pages(zone) + compact_gap(sc->order);
6023
6024 return zone_watermark_ok_safe(zone, 0, watermark, sc->reclaim_idx);
6025}
6026
6027static void consider_reclaim_throttle(pg_data_t *pgdat, struct scan_control *sc)
6028{
6029 /*
6030 * If reclaim is making progress greater than 12% efficiency then
6031 * wake all the NOPROGRESS throttled tasks.
6032 */
6033 if (sc->nr_reclaimed > (sc->nr_scanned >> 3)) {
6034 wait_queue_head_t *wqh;
6035
6036 wqh = &pgdat->reclaim_wait[VMSCAN_THROTTLE_NOPROGRESS];
6037 if (waitqueue_active(wqh))
6038 wake_up(wqh);
6039
6040 return;
6041 }
6042
6043 /*
6044 * Do not throttle kswapd or cgroup reclaim on NOPROGRESS as it will
6045 * throttle on VMSCAN_THROTTLE_WRITEBACK if there are too many pages
6046 * under writeback and marked for immediate reclaim at the tail of the
6047 * LRU.
6048 */
6049 if (current_is_kswapd() || cgroup_reclaim(sc))
6050 return;
6051
6052 /* Throttle if making no progress at high prioities. */
6053 if (sc->priority == 1 && !sc->nr_reclaimed)
6054 reclaim_throttle(pgdat, VMSCAN_THROTTLE_NOPROGRESS);
6055}
6056
6057/*
6058 * This is the direct reclaim path, for page-allocating processes. We only
6059 * try to reclaim pages from zones which will satisfy the caller's allocation
6060 * request.
6061 *
6062 * If a zone is deemed to be full of pinned pages then just give it a light
6063 * scan then give up on it.
6064 */
6065static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
6066{
6067 struct zoneref *z;
6068 struct zone *zone;
6069 unsigned long nr_soft_reclaimed;
6070 unsigned long nr_soft_scanned;
6071 gfp_t orig_mask;
6072 pg_data_t *last_pgdat = NULL;
6073 pg_data_t *first_pgdat = NULL;
6074
6075 /*
6076 * If the number of buffer_heads in the machine exceeds the maximum
6077 * allowed level, force direct reclaim to scan the highmem zone as
6078 * highmem pages could be pinning lowmem pages storing buffer_heads
6079 */
6080 orig_mask = sc->gfp_mask;
6081 if (buffer_heads_over_limit) {
6082 sc->gfp_mask |= __GFP_HIGHMEM;
6083 sc->reclaim_idx = gfp_zone(sc->gfp_mask);
6084 }
6085
6086 for_each_zone_zonelist_nodemask(zone, z, zonelist,
6087 sc->reclaim_idx, sc->nodemask) {
6088 /*
6089 * Take care memory controller reclaiming has small influence
6090 * to global LRU.
6091 */
6092 if (!cgroup_reclaim(sc)) {
6093 if (!cpuset_zone_allowed(zone,
6094 GFP_KERNEL | __GFP_HARDWALL))
6095 continue;
6096
6097 /*
6098 * If we already have plenty of memory free for
6099 * compaction in this zone, don't free any more.
6100 * Even though compaction is invoked for any
6101 * non-zero order, only frequent costly order
6102 * reclamation is disruptive enough to become a
6103 * noticeable problem, like transparent huge
6104 * page allocations.
6105 */
6106 if (IS_ENABLED(CONFIG_COMPACTION) &&
6107 sc->order > PAGE_ALLOC_COSTLY_ORDER &&
6108 compaction_ready(zone, sc)) {
6109 sc->compaction_ready = true;
6110 continue;
6111 }
6112
6113 /*
6114 * Shrink each node in the zonelist once. If the
6115 * zonelist is ordered by zone (not the default) then a
6116 * node may be shrunk multiple times but in that case
6117 * the user prefers lower zones being preserved.
6118 */
6119 if (zone->zone_pgdat == last_pgdat)
6120 continue;
6121
6122 /*
6123 * This steals pages from memory cgroups over softlimit
6124 * and returns the number of reclaimed pages and
6125 * scanned pages. This works for global memory pressure
6126 * and balancing, not for a memcg's limit.
6127 */
6128 nr_soft_scanned = 0;
6129 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone->zone_pgdat,
6130 sc->order, sc->gfp_mask,
6131 &nr_soft_scanned);
6132 sc->nr_reclaimed += nr_soft_reclaimed;
6133 sc->nr_scanned += nr_soft_scanned;
6134 /* need some check for avoid more shrink_zone() */
6135 }
6136
6137 if (!first_pgdat)
6138 first_pgdat = zone->zone_pgdat;
6139
6140 /* See comment about same check for global reclaim above */
6141 if (zone->zone_pgdat == last_pgdat)
6142 continue;
6143 last_pgdat = zone->zone_pgdat;
6144 shrink_node(zone->zone_pgdat, sc);
6145 }
6146
6147 if (first_pgdat)
6148 consider_reclaim_throttle(first_pgdat, sc);
6149
6150 /*
6151 * Restore to original mask to avoid the impact on the caller if we
6152 * promoted it to __GFP_HIGHMEM.
6153 */
6154 sc->gfp_mask = orig_mask;
6155}
6156
6157static void snapshot_refaults(struct mem_cgroup *target_memcg, pg_data_t *pgdat)
6158{
6159 struct lruvec *target_lruvec;
6160 unsigned long refaults;
6161
6162 if (lru_gen_enabled())
6163 return;
6164
6165 target_lruvec = mem_cgroup_lruvec(target_memcg, pgdat);
6166 refaults = lruvec_page_state(target_lruvec, WORKINGSET_ACTIVATE_ANON);
6167 target_lruvec->refaults[WORKINGSET_ANON] = refaults;
6168 refaults = lruvec_page_state(target_lruvec, WORKINGSET_ACTIVATE_FILE);
6169 target_lruvec->refaults[WORKINGSET_FILE] = refaults;
6170}
6171
6172/*
6173 * This is the main entry point to direct page reclaim.
6174 *
6175 * If a full scan of the inactive list fails to free enough memory then we
6176 * are "out of memory" and something needs to be killed.
6177 *
6178 * If the caller is !__GFP_FS then the probability of a failure is reasonably
6179 * high - the zone may be full of dirty or under-writeback pages, which this
6180 * caller can't do much about. We kick the writeback threads and take explicit
6181 * naps in the hope that some of these pages can be written. But if the
6182 * allocating task holds filesystem locks which prevent writeout this might not
6183 * work, and the allocation attempt will fail.
6184 *
6185 * returns: 0, if no pages reclaimed
6186 * else, the number of pages reclaimed
6187 */
6188static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
6189 struct scan_control *sc)
6190{
6191 int initial_priority = sc->priority;
6192 pg_data_t *last_pgdat;
6193 struct zoneref *z;
6194 struct zone *zone;
6195retry:
6196 delayacct_freepages_start();
6197
6198 if (!cgroup_reclaim(sc))
6199 __count_zid_vm_events(ALLOCSTALL, sc->reclaim_idx, 1);
6200
6201 do {
6202 if (!sc->proactive)
6203 vmpressure_prio(sc->gfp_mask, sc->target_mem_cgroup,
6204 sc->priority);
6205 sc->nr_scanned = 0;
6206 shrink_zones(zonelist, sc);
6207
6208 if (sc->nr_reclaimed >= sc->nr_to_reclaim)
6209 break;
6210
6211 if (sc->compaction_ready)
6212 break;
6213
6214 /*
6215 * If we're getting trouble reclaiming, start doing
6216 * writepage even in laptop mode.
6217 */
6218 if (sc->priority < DEF_PRIORITY - 2)
6219 sc->may_writepage = 1;
6220 } while (--sc->priority >= 0);
6221
6222 last_pgdat = NULL;
6223 for_each_zone_zonelist_nodemask(zone, z, zonelist, sc->reclaim_idx,
6224 sc->nodemask) {
6225 if (zone->zone_pgdat == last_pgdat)
6226 continue;
6227 last_pgdat = zone->zone_pgdat;
6228
6229 snapshot_refaults(sc->target_mem_cgroup, zone->zone_pgdat);
6230
6231 if (cgroup_reclaim(sc)) {
6232 struct lruvec *lruvec;
6233
6234 lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup,
6235 zone->zone_pgdat);
6236 clear_bit(LRUVEC_CGROUP_CONGESTED, &lruvec->flags);
6237 }
6238 }
6239
6240 delayacct_freepages_end();
6241
6242 if (sc->nr_reclaimed)
6243 return sc->nr_reclaimed;
6244
6245 /* Aborted reclaim to try compaction? don't OOM, then */
6246 if (sc->compaction_ready)
6247 return 1;
6248
6249 /*
6250 * We make inactive:active ratio decisions based on the node's
6251 * composition of memory, but a restrictive reclaim_idx or a
6252 * memory.low cgroup setting can exempt large amounts of
6253 * memory from reclaim. Neither of which are very common, so
6254 * instead of doing costly eligibility calculations of the
6255 * entire cgroup subtree up front, we assume the estimates are
6256 * good, and retry with forcible deactivation if that fails.
6257 */
6258 if (sc->skipped_deactivate) {
6259 sc->priority = initial_priority;
6260 sc->force_deactivate = 1;
6261 sc->skipped_deactivate = 0;
6262 goto retry;
6263 }
6264
6265 /* Untapped cgroup reserves? Don't OOM, retry. */
6266 if (sc->memcg_low_skipped) {
6267 sc->priority = initial_priority;
6268 sc->force_deactivate = 0;
6269 sc->memcg_low_reclaim = 1;
6270 sc->memcg_low_skipped = 0;
6271 goto retry;
6272 }
6273
6274 return 0;
6275}
6276
6277static bool allow_direct_reclaim(pg_data_t *pgdat)
6278{
6279 struct zone *zone;
6280 unsigned long pfmemalloc_reserve = 0;
6281 unsigned long free_pages = 0;
6282 int i;
6283 bool wmark_ok;
6284
6285 if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES)
6286 return true;
6287
6288 for (i = 0; i <= ZONE_NORMAL; i++) {
6289 zone = &pgdat->node_zones[i];
6290 if (!managed_zone(zone))
6291 continue;
6292
6293 if (!zone_reclaimable_pages(zone))
6294 continue;
6295
6296 pfmemalloc_reserve += min_wmark_pages(zone);
6297 free_pages += zone_page_state_snapshot(zone, NR_FREE_PAGES);
6298 }
6299
6300 /* If there are no reserves (unexpected config) then do not throttle */
6301 if (!pfmemalloc_reserve)
6302 return true;
6303
6304 wmark_ok = free_pages > pfmemalloc_reserve / 2;
6305
6306 /* kswapd must be awake if processes are being throttled */
6307 if (!wmark_ok && waitqueue_active(&pgdat->kswapd_wait)) {
6308 if (READ_ONCE(pgdat->kswapd_highest_zoneidx) > ZONE_NORMAL)
6309 WRITE_ONCE(pgdat->kswapd_highest_zoneidx, ZONE_NORMAL);
6310
6311 wake_up_interruptible(&pgdat->kswapd_wait);
6312 }
6313
6314 return wmark_ok;
6315}
6316
6317/*
6318 * Throttle direct reclaimers if backing storage is backed by the network
6319 * and the PFMEMALLOC reserve for the preferred node is getting dangerously
6320 * depleted. kswapd will continue to make progress and wake the processes
6321 * when the low watermark is reached.
6322 *
6323 * Returns true if a fatal signal was delivered during throttling. If this
6324 * happens, the page allocator should not consider triggering the OOM killer.
6325 */
6326static bool throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist *zonelist,
6327 nodemask_t *nodemask)
6328{
6329 struct zoneref *z;
6330 struct zone *zone;
6331 pg_data_t *pgdat = NULL;
6332
6333 /*
6334 * Kernel threads should not be throttled as they may be indirectly
6335 * responsible for cleaning pages necessary for reclaim to make forward
6336 * progress. kjournald for example may enter direct reclaim while
6337 * committing a transaction where throttling it could forcing other
6338 * processes to block on log_wait_commit().
6339 */
6340 if (current->flags & PF_KTHREAD)
6341 goto out;
6342
6343 /*
6344 * If a fatal signal is pending, this process should not throttle.
6345 * It should return quickly so it can exit and free its memory
6346 */
6347 if (fatal_signal_pending(current))
6348 goto out;
6349
6350 /*
6351 * Check if the pfmemalloc reserves are ok by finding the first node
6352 * with a usable ZONE_NORMAL or lower zone. The expectation is that
6353 * GFP_KERNEL will be required for allocating network buffers when
6354 * swapping over the network so ZONE_HIGHMEM is unusable.
6355 *
6356 * Throttling is based on the first usable node and throttled processes
6357 * wait on a queue until kswapd makes progress and wakes them. There
6358 * is an affinity then between processes waking up and where reclaim
6359 * progress has been made assuming the process wakes on the same node.
6360 * More importantly, processes running on remote nodes will not compete
6361 * for remote pfmemalloc reserves and processes on different nodes
6362 * should make reasonable progress.
6363 */
6364 for_each_zone_zonelist_nodemask(zone, z, zonelist,
6365 gfp_zone(gfp_mask), nodemask) {
6366 if (zone_idx(zone) > ZONE_NORMAL)
6367 continue;
6368
6369 /* Throttle based on the first usable node */
6370 pgdat = zone->zone_pgdat;
6371 if (allow_direct_reclaim(pgdat))
6372 goto out;
6373 break;
6374 }
6375
6376 /* If no zone was usable by the allocation flags then do not throttle */
6377 if (!pgdat)
6378 goto out;
6379
6380 /* Account for the throttling */
6381 count_vm_event(PGSCAN_DIRECT_THROTTLE);
6382
6383 /*
6384 * If the caller cannot enter the filesystem, it's possible that it
6385 * is due to the caller holding an FS lock or performing a journal
6386 * transaction in the case of a filesystem like ext[3|4]. In this case,
6387 * it is not safe to block on pfmemalloc_wait as kswapd could be
6388 * blocked waiting on the same lock. Instead, throttle for up to a
6389 * second before continuing.
6390 */
6391 if (!(gfp_mask & __GFP_FS))
6392 wait_event_interruptible_timeout(pgdat->pfmemalloc_wait,
6393 allow_direct_reclaim(pgdat), HZ);
6394 else
6395 /* Throttle until kswapd wakes the process */
6396 wait_event_killable(zone->zone_pgdat->pfmemalloc_wait,
6397 allow_direct_reclaim(pgdat));
6398
6399 if (fatal_signal_pending(current))
6400 return true;
6401
6402out:
6403 return false;
6404}
6405
6406unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
6407 gfp_t gfp_mask, nodemask_t *nodemask)
6408{
6409 unsigned long nr_reclaimed;
6410 struct scan_control sc = {
6411 .nr_to_reclaim = SWAP_CLUSTER_MAX,
6412 .gfp_mask = current_gfp_context(gfp_mask),
6413 .reclaim_idx = gfp_zone(gfp_mask),
6414 .order = order,
6415 .nodemask = nodemask,
6416 .priority = DEF_PRIORITY,
6417 .may_writepage = !laptop_mode,
6418 .may_unmap = 1,
6419 .may_swap = 1,
6420 };
6421
6422 /*
6423 * scan_control uses s8 fields for order, priority, and reclaim_idx.
6424 * Confirm they are large enough for max values.
6425 */
6426 BUILD_BUG_ON(MAX_PAGE_ORDER >= S8_MAX);
6427 BUILD_BUG_ON(DEF_PRIORITY > S8_MAX);
6428 BUILD_BUG_ON(MAX_NR_ZONES > S8_MAX);
6429
6430 /*
6431 * Do not enter reclaim if fatal signal was delivered while throttled.
6432 * 1 is returned so that the page allocator does not OOM kill at this
6433 * point.
6434 */
6435 if (throttle_direct_reclaim(sc.gfp_mask, zonelist, nodemask))
6436 return 1;
6437
6438 set_task_reclaim_state(current, &sc.reclaim_state);
6439 trace_mm_vmscan_direct_reclaim_begin(order, sc.gfp_mask);
6440
6441 nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
6442
6443 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
6444 set_task_reclaim_state(current, NULL);
6445
6446 return nr_reclaimed;
6447}
6448
6449#ifdef CONFIG_MEMCG
6450
6451/* Only used by soft limit reclaim. Do not reuse for anything else. */
6452unsigned long mem_cgroup_shrink_node(struct mem_cgroup *memcg,
6453 gfp_t gfp_mask, bool noswap,
6454 pg_data_t *pgdat,
6455 unsigned long *nr_scanned)
6456{
6457 struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
6458 struct scan_control sc = {
6459 .nr_to_reclaim = SWAP_CLUSTER_MAX,
6460 .target_mem_cgroup = memcg,
6461 .may_writepage = !laptop_mode,
6462 .may_unmap = 1,
6463 .reclaim_idx = MAX_NR_ZONES - 1,
6464 .may_swap = !noswap,
6465 };
6466
6467 WARN_ON_ONCE(!current->reclaim_state);
6468
6469 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
6470 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
6471
6472 trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc.order,
6473 sc.gfp_mask);
6474
6475 /*
6476 * NOTE: Although we can get the priority field, using it
6477 * here is not a good idea, since it limits the pages we can scan.
6478 * if we don't reclaim here, the shrink_node from balance_pgdat
6479 * will pick up pages from other mem cgroup's as well. We hack
6480 * the priority and make it zero.
6481 */
6482 shrink_lruvec(lruvec, &sc);
6483
6484 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
6485
6486 *nr_scanned = sc.nr_scanned;
6487
6488 return sc.nr_reclaimed;
6489}
6490
6491unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
6492 unsigned long nr_pages,
6493 gfp_t gfp_mask,
6494 unsigned int reclaim_options)
6495{
6496 unsigned long nr_reclaimed;
6497 unsigned int noreclaim_flag;
6498 struct scan_control sc = {
6499 .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
6500 .gfp_mask = (current_gfp_context(gfp_mask) & GFP_RECLAIM_MASK) |
6501 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
6502 .reclaim_idx = MAX_NR_ZONES - 1,
6503 .target_mem_cgroup = memcg,
6504 .priority = DEF_PRIORITY,
6505 .may_writepage = !laptop_mode,
6506 .may_unmap = 1,
6507 .may_swap = !!(reclaim_options & MEMCG_RECLAIM_MAY_SWAP),
6508 .proactive = !!(reclaim_options & MEMCG_RECLAIM_PROACTIVE),
6509 };
6510 /*
6511 * Traverse the ZONELIST_FALLBACK zonelist of the current node to put
6512 * equal pressure on all the nodes. This is based on the assumption that
6513 * the reclaim does not bail out early.
6514 */
6515 struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
6516
6517 set_task_reclaim_state(current, &sc.reclaim_state);
6518 trace_mm_vmscan_memcg_reclaim_begin(0, sc.gfp_mask);
6519 noreclaim_flag = memalloc_noreclaim_save();
6520
6521 nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
6522
6523 memalloc_noreclaim_restore(noreclaim_flag);
6524 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
6525 set_task_reclaim_state(current, NULL);
6526
6527 return nr_reclaimed;
6528}
6529#endif
6530
6531static void kswapd_age_node(struct pglist_data *pgdat, struct scan_control *sc)
6532{
6533 struct mem_cgroup *memcg;
6534 struct lruvec *lruvec;
6535
6536 if (lru_gen_enabled()) {
6537 lru_gen_age_node(pgdat, sc);
6538 return;
6539 }
6540
6541 if (!can_age_anon_pages(pgdat, sc))
6542 return;
6543
6544 lruvec = mem_cgroup_lruvec(NULL, pgdat);
6545 if (!inactive_is_low(lruvec, LRU_INACTIVE_ANON))
6546 return;
6547
6548 memcg = mem_cgroup_iter(NULL, NULL, NULL);
6549 do {
6550 lruvec = mem_cgroup_lruvec(memcg, pgdat);
6551 shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
6552 sc, LRU_ACTIVE_ANON);
6553 memcg = mem_cgroup_iter(NULL, memcg, NULL);
6554 } while (memcg);
6555}
6556
6557static bool pgdat_watermark_boosted(pg_data_t *pgdat, int highest_zoneidx)
6558{
6559 int i;
6560 struct zone *zone;
6561
6562 /*
6563 * Check for watermark boosts top-down as the higher zones
6564 * are more likely to be boosted. Both watermarks and boosts
6565 * should not be checked at the same time as reclaim would
6566 * start prematurely when there is no boosting and a lower
6567 * zone is balanced.
6568 */
6569 for (i = highest_zoneidx; i >= 0; i--) {
6570 zone = pgdat->node_zones + i;
6571 if (!managed_zone(zone))
6572 continue;
6573
6574 if (zone->watermark_boost)
6575 return true;
6576 }
6577
6578 return false;
6579}
6580
6581/*
6582 * Returns true if there is an eligible zone balanced for the request order
6583 * and highest_zoneidx
6584 */
6585static bool pgdat_balanced(pg_data_t *pgdat, int order, int highest_zoneidx)
6586{
6587 int i;
6588 unsigned long mark = -1;
6589 struct zone *zone;
6590
6591 /*
6592 * Check watermarks bottom-up as lower zones are more likely to
6593 * meet watermarks.
6594 */
6595 for (i = 0; i <= highest_zoneidx; i++) {
6596 zone = pgdat->node_zones + i;
6597
6598 if (!managed_zone(zone))
6599 continue;
6600
6601 if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING)
6602 mark = wmark_pages(zone, WMARK_PROMO);
6603 else
6604 mark = high_wmark_pages(zone);
6605 if (zone_watermark_ok_safe(zone, order, mark, highest_zoneidx))
6606 return true;
6607 }
6608
6609 /*
6610 * If a node has no managed zone within highest_zoneidx, it does not
6611 * need balancing by definition. This can happen if a zone-restricted
6612 * allocation tries to wake a remote kswapd.
6613 */
6614 if (mark == -1)
6615 return true;
6616
6617 return false;
6618}
6619
6620/* Clear pgdat state for congested, dirty or under writeback. */
6621static void clear_pgdat_congested(pg_data_t *pgdat)
6622{
6623 struct lruvec *lruvec = mem_cgroup_lruvec(NULL, pgdat);
6624
6625 clear_bit(LRUVEC_NODE_CONGESTED, &lruvec->flags);
6626 clear_bit(LRUVEC_CGROUP_CONGESTED, &lruvec->flags);
6627 clear_bit(PGDAT_DIRTY, &pgdat->flags);
6628 clear_bit(PGDAT_WRITEBACK, &pgdat->flags);
6629}
6630
6631/*
6632 * Prepare kswapd for sleeping. This verifies that there are no processes
6633 * waiting in throttle_direct_reclaim() and that watermarks have been met.
6634 *
6635 * Returns true if kswapd is ready to sleep
6636 */
6637static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order,
6638 int highest_zoneidx)
6639{
6640 /*
6641 * The throttled processes are normally woken up in balance_pgdat() as
6642 * soon as allow_direct_reclaim() is true. But there is a potential
6643 * race between when kswapd checks the watermarks and a process gets
6644 * throttled. There is also a potential race if processes get
6645 * throttled, kswapd wakes, a large process exits thereby balancing the
6646 * zones, which causes kswapd to exit balance_pgdat() before reaching
6647 * the wake up checks. If kswapd is going to sleep, no process should
6648 * be sleeping on pfmemalloc_wait, so wake them now if necessary. If
6649 * the wake up is premature, processes will wake kswapd and get
6650 * throttled again. The difference from wake ups in balance_pgdat() is
6651 * that here we are under prepare_to_wait().
6652 */
6653 if (waitqueue_active(&pgdat->pfmemalloc_wait))
6654 wake_up_all(&pgdat->pfmemalloc_wait);
6655
6656 /* Hopeless node, leave it to direct reclaim */
6657 if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES)
6658 return true;
6659
6660 if (pgdat_balanced(pgdat, order, highest_zoneidx)) {
6661 clear_pgdat_congested(pgdat);
6662 return true;
6663 }
6664
6665 return false;
6666}
6667
6668/*
6669 * kswapd shrinks a node of pages that are at or below the highest usable
6670 * zone that is currently unbalanced.
6671 *
6672 * Returns true if kswapd scanned at least the requested number of pages to
6673 * reclaim or if the lack of progress was due to pages under writeback.
6674 * This is used to determine if the scanning priority needs to be raised.
6675 */
6676static bool kswapd_shrink_node(pg_data_t *pgdat,
6677 struct scan_control *sc)
6678{
6679 struct zone *zone;
6680 int z;
6681
6682 /* Reclaim a number of pages proportional to the number of zones */
6683 sc->nr_to_reclaim = 0;
6684 for (z = 0; z <= sc->reclaim_idx; z++) {
6685 zone = pgdat->node_zones + z;
6686 if (!managed_zone(zone))
6687 continue;
6688
6689 sc->nr_to_reclaim += max(high_wmark_pages(zone), SWAP_CLUSTER_MAX);
6690 }
6691
6692 /*
6693 * Historically care was taken to put equal pressure on all zones but
6694 * now pressure is applied based on node LRU order.
6695 */
6696 shrink_node(pgdat, sc);
6697
6698 /*
6699 * Fragmentation may mean that the system cannot be rebalanced for
6700 * high-order allocations. If twice the allocation size has been
6701 * reclaimed then recheck watermarks only at order-0 to prevent
6702 * excessive reclaim. Assume that a process requested a high-order
6703 * can direct reclaim/compact.
6704 */
6705 if (sc->order && sc->nr_reclaimed >= compact_gap(sc->order))
6706 sc->order = 0;
6707
6708 return sc->nr_scanned >= sc->nr_to_reclaim;
6709}
6710
6711/* Page allocator PCP high watermark is lowered if reclaim is active. */
6712static inline void
6713update_reclaim_active(pg_data_t *pgdat, int highest_zoneidx, bool active)
6714{
6715 int i;
6716 struct zone *zone;
6717
6718 for (i = 0; i <= highest_zoneidx; i++) {
6719 zone = pgdat->node_zones + i;
6720
6721 if (!managed_zone(zone))
6722 continue;
6723
6724 if (active)
6725 set_bit(ZONE_RECLAIM_ACTIVE, &zone->flags);
6726 else
6727 clear_bit(ZONE_RECLAIM_ACTIVE, &zone->flags);
6728 }
6729}
6730
6731static inline void
6732set_reclaim_active(pg_data_t *pgdat, int highest_zoneidx)
6733{
6734 update_reclaim_active(pgdat, highest_zoneidx, true);
6735}
6736
6737static inline void
6738clear_reclaim_active(pg_data_t *pgdat, int highest_zoneidx)
6739{
6740 update_reclaim_active(pgdat, highest_zoneidx, false);
6741}
6742
6743/*
6744 * For kswapd, balance_pgdat() will reclaim pages across a node from zones
6745 * that are eligible for use by the caller until at least one zone is
6746 * balanced.
6747 *
6748 * Returns the order kswapd finished reclaiming at.
6749 *
6750 * kswapd scans the zones in the highmem->normal->dma direction. It skips
6751 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
6752 * found to have free_pages <= high_wmark_pages(zone), any page in that zone
6753 * or lower is eligible for reclaim until at least one usable zone is
6754 * balanced.
6755 */
6756static int balance_pgdat(pg_data_t *pgdat, int order, int highest_zoneidx)
6757{
6758 int i;
6759 unsigned long nr_soft_reclaimed;
6760 unsigned long nr_soft_scanned;
6761 unsigned long pflags;
6762 unsigned long nr_boost_reclaim;
6763 unsigned long zone_boosts[MAX_NR_ZONES] = { 0, };
6764 bool boosted;
6765 struct zone *zone;
6766 struct scan_control sc = {
6767 .gfp_mask = GFP_KERNEL,
6768 .order = order,
6769 .may_unmap = 1,
6770 };
6771
6772 set_task_reclaim_state(current, &sc.reclaim_state);
6773 psi_memstall_enter(&pflags);
6774 __fs_reclaim_acquire(_THIS_IP_);
6775
6776 count_vm_event(PAGEOUTRUN);
6777
6778 /*
6779 * Account for the reclaim boost. Note that the zone boost is left in
6780 * place so that parallel allocations that are near the watermark will
6781 * stall or direct reclaim until kswapd is finished.
6782 */
6783 nr_boost_reclaim = 0;
6784 for (i = 0; i <= highest_zoneidx; i++) {
6785 zone = pgdat->node_zones + i;
6786 if (!managed_zone(zone))
6787 continue;
6788
6789 nr_boost_reclaim += zone->watermark_boost;
6790 zone_boosts[i] = zone->watermark_boost;
6791 }
6792 boosted = nr_boost_reclaim;
6793
6794restart:
6795 set_reclaim_active(pgdat, highest_zoneidx);
6796 sc.priority = DEF_PRIORITY;
6797 do {
6798 unsigned long nr_reclaimed = sc.nr_reclaimed;
6799 bool raise_priority = true;
6800 bool balanced;
6801 bool ret;
6802
6803 sc.reclaim_idx = highest_zoneidx;
6804
6805 /*
6806 * If the number of buffer_heads exceeds the maximum allowed
6807 * then consider reclaiming from all zones. This has a dual
6808 * purpose -- on 64-bit systems it is expected that
6809 * buffer_heads are stripped during active rotation. On 32-bit
6810 * systems, highmem pages can pin lowmem memory and shrinking
6811 * buffers can relieve lowmem pressure. Reclaim may still not
6812 * go ahead if all eligible zones for the original allocation
6813 * request are balanced to avoid excessive reclaim from kswapd.
6814 */
6815 if (buffer_heads_over_limit) {
6816 for (i = MAX_NR_ZONES - 1; i >= 0; i--) {
6817 zone = pgdat->node_zones + i;
6818 if (!managed_zone(zone))
6819 continue;
6820
6821 sc.reclaim_idx = i;
6822 break;
6823 }
6824 }
6825
6826 /*
6827 * If the pgdat is imbalanced then ignore boosting and preserve
6828 * the watermarks for a later time and restart. Note that the
6829 * zone watermarks will be still reset at the end of balancing
6830 * on the grounds that the normal reclaim should be enough to
6831 * re-evaluate if boosting is required when kswapd next wakes.
6832 */
6833 balanced = pgdat_balanced(pgdat, sc.order, highest_zoneidx);
6834 if (!balanced && nr_boost_reclaim) {
6835 nr_boost_reclaim = 0;
6836 goto restart;
6837 }
6838
6839 /*
6840 * If boosting is not active then only reclaim if there are no
6841 * eligible zones. Note that sc.reclaim_idx is not used as
6842 * buffer_heads_over_limit may have adjusted it.
6843 */
6844 if (!nr_boost_reclaim && balanced)
6845 goto out;
6846
6847 /* Limit the priority of boosting to avoid reclaim writeback */
6848 if (nr_boost_reclaim && sc.priority == DEF_PRIORITY - 2)
6849 raise_priority = false;
6850
6851 /*
6852 * Do not writeback or swap pages for boosted reclaim. The
6853 * intent is to relieve pressure not issue sub-optimal IO
6854 * from reclaim context. If no pages are reclaimed, the
6855 * reclaim will be aborted.
6856 */
6857 sc.may_writepage = !laptop_mode && !nr_boost_reclaim;
6858 sc.may_swap = !nr_boost_reclaim;
6859
6860 /*
6861 * Do some background aging, to give pages a chance to be
6862 * referenced before reclaiming. All pages are rotated
6863 * regardless of classzone as this is about consistent aging.
6864 */
6865 kswapd_age_node(pgdat, &sc);
6866
6867 /*
6868 * If we're getting trouble reclaiming, start doing writepage
6869 * even in laptop mode.
6870 */
6871 if (sc.priority < DEF_PRIORITY - 2)
6872 sc.may_writepage = 1;
6873
6874 /* Call soft limit reclaim before calling shrink_node. */
6875 sc.nr_scanned = 0;
6876 nr_soft_scanned = 0;
6877 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(pgdat, sc.order,
6878 sc.gfp_mask, &nr_soft_scanned);
6879 sc.nr_reclaimed += nr_soft_reclaimed;
6880
6881 /*
6882 * There should be no need to raise the scanning priority if
6883 * enough pages are already being scanned that that high
6884 * watermark would be met at 100% efficiency.
6885 */
6886 if (kswapd_shrink_node(pgdat, &sc))
6887 raise_priority = false;
6888
6889 /*
6890 * If the low watermark is met there is no need for processes
6891 * to be throttled on pfmemalloc_wait as they should not be
6892 * able to safely make forward progress. Wake them
6893 */
6894 if (waitqueue_active(&pgdat->pfmemalloc_wait) &&
6895 allow_direct_reclaim(pgdat))
6896 wake_up_all(&pgdat->pfmemalloc_wait);
6897
6898 /* Check if kswapd should be suspending */
6899 __fs_reclaim_release(_THIS_IP_);
6900 ret = try_to_freeze();
6901 __fs_reclaim_acquire(_THIS_IP_);
6902 if (ret || kthread_should_stop())
6903 break;
6904
6905 /*
6906 * Raise priority if scanning rate is too low or there was no
6907 * progress in reclaiming pages
6908 */
6909 nr_reclaimed = sc.nr_reclaimed - nr_reclaimed;
6910 nr_boost_reclaim -= min(nr_boost_reclaim, nr_reclaimed);
6911
6912 /*
6913 * If reclaim made no progress for a boost, stop reclaim as
6914 * IO cannot be queued and it could be an infinite loop in
6915 * extreme circumstances.
6916 */
6917 if (nr_boost_reclaim && !nr_reclaimed)
6918 break;
6919
6920 if (raise_priority || !nr_reclaimed)
6921 sc.priority--;
6922 } while (sc.priority >= 1);
6923
6924 if (!sc.nr_reclaimed)
6925 pgdat->kswapd_failures++;
6926
6927out:
6928 clear_reclaim_active(pgdat, highest_zoneidx);
6929
6930 /* If reclaim was boosted, account for the reclaim done in this pass */
6931 if (boosted) {
6932 unsigned long flags;
6933
6934 for (i = 0; i <= highest_zoneidx; i++) {
6935 if (!zone_boosts[i])
6936 continue;
6937
6938 /* Increments are under the zone lock */
6939 zone = pgdat->node_zones + i;
6940 spin_lock_irqsave(&zone->lock, flags);
6941 zone->watermark_boost -= min(zone->watermark_boost, zone_boosts[i]);
6942 spin_unlock_irqrestore(&zone->lock, flags);
6943 }
6944
6945 /*
6946 * As there is now likely space, wakeup kcompact to defragment
6947 * pageblocks.
6948 */
6949 wakeup_kcompactd(pgdat, pageblock_order, highest_zoneidx);
6950 }
6951
6952 snapshot_refaults(NULL, pgdat);
6953 __fs_reclaim_release(_THIS_IP_);
6954 psi_memstall_leave(&pflags);
6955 set_task_reclaim_state(current, NULL);
6956
6957 /*
6958 * Return the order kswapd stopped reclaiming at as
6959 * prepare_kswapd_sleep() takes it into account. If another caller
6960 * entered the allocator slow path while kswapd was awake, order will
6961 * remain at the higher level.
6962 */
6963 return sc.order;
6964}
6965
6966/*
6967 * The pgdat->kswapd_highest_zoneidx is used to pass the highest zone index to
6968 * be reclaimed by kswapd from the waker. If the value is MAX_NR_ZONES which is
6969 * not a valid index then either kswapd runs for first time or kswapd couldn't
6970 * sleep after previous reclaim attempt (node is still unbalanced). In that
6971 * case return the zone index of the previous kswapd reclaim cycle.
6972 */
6973static enum zone_type kswapd_highest_zoneidx(pg_data_t *pgdat,
6974 enum zone_type prev_highest_zoneidx)
6975{
6976 enum zone_type curr_idx = READ_ONCE(pgdat->kswapd_highest_zoneidx);
6977
6978 return curr_idx == MAX_NR_ZONES ? prev_highest_zoneidx : curr_idx;
6979}
6980
6981static void kswapd_try_to_sleep(pg_data_t *pgdat, int alloc_order, int reclaim_order,
6982 unsigned int highest_zoneidx)
6983{
6984 long remaining = 0;
6985 DEFINE_WAIT(wait);
6986
6987 if (freezing(current) || kthread_should_stop())
6988 return;
6989
6990 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
6991
6992 /*
6993 * Try to sleep for a short interval. Note that kcompactd will only be
6994 * woken if it is possible to sleep for a short interval. This is
6995 * deliberate on the assumption that if reclaim cannot keep an
6996 * eligible zone balanced that it's also unlikely that compaction will
6997 * succeed.
6998 */
6999 if (prepare_kswapd_sleep(pgdat, reclaim_order, highest_zoneidx)) {
7000 /*
7001 * Compaction records what page blocks it recently failed to
7002 * isolate pages from and skips them in the future scanning.
7003 * When kswapd is going to sleep, it is reasonable to assume
7004 * that pages and compaction may succeed so reset the cache.
7005 */
7006 reset_isolation_suitable(pgdat);
7007
7008 /*
7009 * We have freed the memory, now we should compact it to make
7010 * allocation of the requested order possible.
7011 */
7012 wakeup_kcompactd(pgdat, alloc_order, highest_zoneidx);
7013
7014 remaining = schedule_timeout(HZ/10);
7015
7016 /*
7017 * If woken prematurely then reset kswapd_highest_zoneidx and
7018 * order. The values will either be from a wakeup request or
7019 * the previous request that slept prematurely.
7020 */
7021 if (remaining) {
7022 WRITE_ONCE(pgdat->kswapd_highest_zoneidx,
7023 kswapd_highest_zoneidx(pgdat,
7024 highest_zoneidx));
7025
7026 if (READ_ONCE(pgdat->kswapd_order) < reclaim_order)
7027 WRITE_ONCE(pgdat->kswapd_order, reclaim_order);
7028 }
7029
7030 finish_wait(&pgdat->kswapd_wait, &wait);
7031 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
7032 }
7033
7034 /*
7035 * After a short sleep, check if it was a premature sleep. If not, then
7036 * go fully to sleep until explicitly woken up.
7037 */
7038 if (!remaining &&
7039 prepare_kswapd_sleep(pgdat, reclaim_order, highest_zoneidx)) {
7040 trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
7041
7042 /*
7043 * vmstat counters are not perfectly accurate and the estimated
7044 * value for counters such as NR_FREE_PAGES can deviate from the
7045 * true value by nr_online_cpus * threshold. To avoid the zone
7046 * watermarks being breached while under pressure, we reduce the
7047 * per-cpu vmstat threshold while kswapd is awake and restore
7048 * them before going back to sleep.
7049 */
7050 set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold);
7051
7052 if (!kthread_should_stop())
7053 schedule();
7054
7055 set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold);
7056 } else {
7057 if (remaining)
7058 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
7059 else
7060 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
7061 }
7062 finish_wait(&pgdat->kswapd_wait, &wait);
7063}
7064
7065/*
7066 * The background pageout daemon, started as a kernel thread
7067 * from the init process.
7068 *
7069 * This basically trickles out pages so that we have _some_
7070 * free memory available even if there is no other activity
7071 * that frees anything up. This is needed for things like routing
7072 * etc, where we otherwise might have all activity going on in
7073 * asynchronous contexts that cannot page things out.
7074 *
7075 * If there are applications that are active memory-allocators
7076 * (most normal use), this basically shouldn't matter.
7077 */
7078static int kswapd(void *p)
7079{
7080 unsigned int alloc_order, reclaim_order;
7081 unsigned int highest_zoneidx = MAX_NR_ZONES - 1;
7082 pg_data_t *pgdat = (pg_data_t *)p;
7083 struct task_struct *tsk = current;
7084 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
7085
7086 if (!cpumask_empty(cpumask))
7087 set_cpus_allowed_ptr(tsk, cpumask);
7088
7089 /*
7090 * Tell the memory management that we're a "memory allocator",
7091 * and that if we need more memory we should get access to it
7092 * regardless (see "__alloc_pages()"). "kswapd" should
7093 * never get caught in the normal page freeing logic.
7094 *
7095 * (Kswapd normally doesn't need memory anyway, but sometimes
7096 * you need a small amount of memory in order to be able to
7097 * page out something else, and this flag essentially protects
7098 * us from recursively trying to free more memory as we're
7099 * trying to free the first piece of memory in the first place).
7100 */
7101 tsk->flags |= PF_MEMALLOC | PF_KSWAPD;
7102 set_freezable();
7103
7104 WRITE_ONCE(pgdat->kswapd_order, 0);
7105 WRITE_ONCE(pgdat->kswapd_highest_zoneidx, MAX_NR_ZONES);
7106 atomic_set(&pgdat->nr_writeback_throttled, 0);
7107 for ( ; ; ) {
7108 bool ret;
7109
7110 alloc_order = reclaim_order = READ_ONCE(pgdat->kswapd_order);
7111 highest_zoneidx = kswapd_highest_zoneidx(pgdat,
7112 highest_zoneidx);
7113
7114kswapd_try_sleep:
7115 kswapd_try_to_sleep(pgdat, alloc_order, reclaim_order,
7116 highest_zoneidx);
7117
7118 /* Read the new order and highest_zoneidx */
7119 alloc_order = READ_ONCE(pgdat->kswapd_order);
7120 highest_zoneidx = kswapd_highest_zoneidx(pgdat,
7121 highest_zoneidx);
7122 WRITE_ONCE(pgdat->kswapd_order, 0);
7123 WRITE_ONCE(pgdat->kswapd_highest_zoneidx, MAX_NR_ZONES);
7124
7125 ret = try_to_freeze();
7126 if (kthread_should_stop())
7127 break;
7128
7129 /*
7130 * We can speed up thawing tasks if we don't call balance_pgdat
7131 * after returning from the refrigerator
7132 */
7133 if (ret)
7134 continue;
7135
7136 /*
7137 * Reclaim begins at the requested order but if a high-order
7138 * reclaim fails then kswapd falls back to reclaiming for
7139 * order-0. If that happens, kswapd will consider sleeping
7140 * for the order it finished reclaiming at (reclaim_order)
7141 * but kcompactd is woken to compact for the original
7142 * request (alloc_order).
7143 */
7144 trace_mm_vmscan_kswapd_wake(pgdat->node_id, highest_zoneidx,
7145 alloc_order);
7146 reclaim_order = balance_pgdat(pgdat, alloc_order,
7147 highest_zoneidx);
7148 if (reclaim_order < alloc_order)
7149 goto kswapd_try_sleep;
7150 }
7151
7152 tsk->flags &= ~(PF_MEMALLOC | PF_KSWAPD);
7153
7154 return 0;
7155}
7156
7157/*
7158 * A zone is low on free memory or too fragmented for high-order memory. If
7159 * kswapd should reclaim (direct reclaim is deferred), wake it up for the zone's
7160 * pgdat. It will wake up kcompactd after reclaiming memory. If kswapd reclaim
7161 * has failed or is not needed, still wake up kcompactd if only compaction is
7162 * needed.
7163 */
7164void wakeup_kswapd(struct zone *zone, gfp_t gfp_flags, int order,
7165 enum zone_type highest_zoneidx)
7166{
7167 pg_data_t *pgdat;
7168 enum zone_type curr_idx;
7169
7170 if (!managed_zone(zone))
7171 return;
7172
7173 if (!cpuset_zone_allowed(zone, gfp_flags))
7174 return;
7175
7176 pgdat = zone->zone_pgdat;
7177 curr_idx = READ_ONCE(pgdat->kswapd_highest_zoneidx);
7178
7179 if (curr_idx == MAX_NR_ZONES || curr_idx < highest_zoneidx)
7180 WRITE_ONCE(pgdat->kswapd_highest_zoneidx, highest_zoneidx);
7181
7182 if (READ_ONCE(pgdat->kswapd_order) < order)
7183 WRITE_ONCE(pgdat->kswapd_order, order);
7184
7185 if (!waitqueue_active(&pgdat->kswapd_wait))
7186 return;
7187
7188 /* Hopeless node, leave it to direct reclaim if possible */
7189 if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES ||
7190 (pgdat_balanced(pgdat, order, highest_zoneidx) &&
7191 !pgdat_watermark_boosted(pgdat, highest_zoneidx))) {
7192 /*
7193 * There may be plenty of free memory available, but it's too
7194 * fragmented for high-order allocations. Wake up kcompactd
7195 * and rely on compaction_suitable() to determine if it's
7196 * needed. If it fails, it will defer subsequent attempts to
7197 * ratelimit its work.
7198 */
7199 if (!(gfp_flags & __GFP_DIRECT_RECLAIM))
7200 wakeup_kcompactd(pgdat, order, highest_zoneidx);
7201 return;
7202 }
7203
7204 trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, highest_zoneidx, order,
7205 gfp_flags);
7206 wake_up_interruptible(&pgdat->kswapd_wait);
7207}
7208
7209#ifdef CONFIG_HIBERNATION
7210/*
7211 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
7212 * freed pages.
7213 *
7214 * Rather than trying to age LRUs the aim is to preserve the overall
7215 * LRU order by reclaiming preferentially
7216 * inactive > active > active referenced > active mapped
7217 */
7218unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
7219{
7220 struct scan_control sc = {
7221 .nr_to_reclaim = nr_to_reclaim,
7222 .gfp_mask = GFP_HIGHUSER_MOVABLE,
7223 .reclaim_idx = MAX_NR_ZONES - 1,
7224 .priority = DEF_PRIORITY,
7225 .may_writepage = 1,
7226 .may_unmap = 1,
7227 .may_swap = 1,
7228 .hibernation_mode = 1,
7229 };
7230 struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
7231 unsigned long nr_reclaimed;
7232 unsigned int noreclaim_flag;
7233
7234 fs_reclaim_acquire(sc.gfp_mask);
7235 noreclaim_flag = memalloc_noreclaim_save();
7236 set_task_reclaim_state(current, &sc.reclaim_state);
7237
7238 nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
7239
7240 set_task_reclaim_state(current, NULL);
7241 memalloc_noreclaim_restore(noreclaim_flag);
7242 fs_reclaim_release(sc.gfp_mask);
7243
7244 return nr_reclaimed;
7245}
7246#endif /* CONFIG_HIBERNATION */
7247
7248/*
7249 * This kswapd start function will be called by init and node-hot-add.
7250 */
7251void __meminit kswapd_run(int nid)
7252{
7253 pg_data_t *pgdat = NODE_DATA(nid);
7254
7255 pgdat_kswapd_lock(pgdat);
7256 if (!pgdat->kswapd) {
7257 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
7258 if (IS_ERR(pgdat->kswapd)) {
7259 /* failure at boot is fatal */
7260 pr_err("Failed to start kswapd on node %d，ret=%ld\n",
7261 nid, PTR_ERR(pgdat->kswapd));
7262 BUG_ON(system_state < SYSTEM_RUNNING);
7263 pgdat->kswapd = NULL;
7264 }
7265 }
7266 pgdat_kswapd_unlock(pgdat);
7267}
7268
7269/*
7270 * Called by memory hotplug when all memory in a node is offlined. Caller must
7271 * be holding mem_hotplug_begin/done().
7272 */
7273void __meminit kswapd_stop(int nid)
7274{
7275 pg_data_t *pgdat = NODE_DATA(nid);
7276 struct task_struct *kswapd;
7277
7278 pgdat_kswapd_lock(pgdat);
7279 kswapd = pgdat->kswapd;
7280 if (kswapd) {
7281 kthread_stop(kswapd);
7282 pgdat->kswapd = NULL;
7283 }
7284 pgdat_kswapd_unlock(pgdat);
7285}
7286
7287static int __init kswapd_init(void)
7288{
7289 int nid;
7290
7291 swap_setup();
7292 for_each_node_state(nid, N_MEMORY)
7293 kswapd_run(nid);
7294 return 0;
7295}
7296
7297module_init(kswapd_init)
7298
7299#ifdef CONFIG_NUMA
7300/*
7301 * Node reclaim mode
7302 *
7303 * If non-zero call node_reclaim when the number of free pages falls below
7304 * the watermarks.
7305 */
7306int node_reclaim_mode __read_mostly;
7307
7308/*
7309 * Priority for NODE_RECLAIM. This determines the fraction of pages
7310 * of a node considered for each zone_reclaim. 4 scans 1/16th of
7311 * a zone.
7312 */
7313#define NODE_RECLAIM_PRIORITY 4
7314
7315/*
7316 * Percentage of pages in a zone that must be unmapped for node_reclaim to
7317 * occur.
7318 */
7319int sysctl_min_unmapped_ratio = 1;
7320
7321/*
7322 * If the number of slab pages in a zone grows beyond this percentage then
7323 * slab reclaim needs to occur.
7324 */
7325int sysctl_min_slab_ratio = 5;
7326
7327static inline unsigned long node_unmapped_file_pages(struct pglist_data *pgdat)
7328{
7329 unsigned long file_mapped = node_page_state(pgdat, NR_FILE_MAPPED);
7330 unsigned long file_lru = node_page_state(pgdat, NR_INACTIVE_FILE) +
7331 node_page_state(pgdat, NR_ACTIVE_FILE);
7332
7333 /*
7334 * It's possible for there to be more file mapped pages than
7335 * accounted for by the pages on the file LRU lists because
7336 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
7337 */
7338 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
7339}
7340
7341/* Work out how many page cache pages we can reclaim in this reclaim_mode */
7342static unsigned long node_pagecache_reclaimable(struct pglist_data *pgdat)
7343{
7344 unsigned long nr_pagecache_reclaimable;
7345 unsigned long delta = 0;
7346
7347 /*
7348 * If RECLAIM_UNMAP is set, then all file pages are considered
7349 * potentially reclaimable. Otherwise, we have to worry about
7350 * pages like swapcache and node_unmapped_file_pages() provides
7351 * a better estimate
7352 */
7353 if (node_reclaim_mode & RECLAIM_UNMAP)
7354 nr_pagecache_reclaimable = node_page_state(pgdat, NR_FILE_PAGES);
7355 else
7356 nr_pagecache_reclaimable = node_unmapped_file_pages(pgdat);
7357
7358 /* If we can't clean pages, remove dirty pages from consideration */
7359 if (!(node_reclaim_mode & RECLAIM_WRITE))
7360 delta += node_page_state(pgdat, NR_FILE_DIRTY);
7361
7362 /* Watch for any possible underflows due to delta */
7363 if (unlikely(delta > nr_pagecache_reclaimable))
7364 delta = nr_pagecache_reclaimable;
7365
7366 return nr_pagecache_reclaimable - delta;
7367}
7368
7369/*
7370 * Try to free up some pages from this node through reclaim.
7371 */
7372static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order)
7373{
7374 /* Minimum pages needed in order to stay on node */
7375 const unsigned long nr_pages = 1 << order;
7376 struct task_struct *p = current;
7377 unsigned int noreclaim_flag;
7378 struct scan_control sc = {
7379 .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
7380 .gfp_mask = current_gfp_context(gfp_mask),
7381 .order = order,
7382 .priority = NODE_RECLAIM_PRIORITY,
7383 .may_writepage = !!(node_reclaim_mode & RECLAIM_WRITE),
7384 .may_unmap = !!(node_reclaim_mode & RECLAIM_UNMAP),
7385 .may_swap = 1,
7386 .reclaim_idx = gfp_zone(gfp_mask),
7387 };
7388 unsigned long pflags;
7389
7390 trace_mm_vmscan_node_reclaim_begin(pgdat->node_id, order,
7391 sc.gfp_mask);
7392
7393 cond_resched();
7394 psi_memstall_enter(&pflags);
7395 delayacct_freepages_start();
7396 fs_reclaim_acquire(sc.gfp_mask);
7397 /*
7398 * We need to be able to allocate from the reserves for RECLAIM_UNMAP
7399 */
7400 noreclaim_flag = memalloc_noreclaim_save();
7401 set_task_reclaim_state(p, &sc.reclaim_state);
7402
7403 if (node_pagecache_reclaimable(pgdat) > pgdat->min_unmapped_pages ||
7404 node_page_state_pages(pgdat, NR_SLAB_RECLAIMABLE_B) > pgdat->min_slab_pages) {
7405 /*
7406 * Free memory by calling shrink node with increasing
7407 * priorities until we have enough memory freed.
7408 */
7409 do {
7410 shrink_node(pgdat, &sc);
7411 } while (sc.nr_reclaimed < nr_pages && --sc.priority >= 0);
7412 }
7413
7414 set_task_reclaim_state(p, NULL);
7415 memalloc_noreclaim_restore(noreclaim_flag);
7416 fs_reclaim_release(sc.gfp_mask);
7417 psi_memstall_leave(&pflags);
7418 delayacct_freepages_end();
7419
7420 trace_mm_vmscan_node_reclaim_end(sc.nr_reclaimed);
7421
7422 return sc.nr_reclaimed >= nr_pages;
7423}
7424
7425int node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order)
7426{
7427 int ret;
7428
7429 /*
7430 * Node reclaim reclaims unmapped file backed pages and
7431 * slab pages if we are over the defined limits.
7432 *
7433 * A small portion of unmapped file backed pages is needed for
7434 * file I/O otherwise pages read by file I/O will be immediately
7435 * thrown out if the node is overallocated. So we do not reclaim
7436 * if less than a specified percentage of the node is used by
7437 * unmapped file backed pages.
7438 */
7439 if (node_pagecache_reclaimable(pgdat) <= pgdat->min_unmapped_pages &&
7440 node_page_state_pages(pgdat, NR_SLAB_RECLAIMABLE_B) <=
7441 pgdat->min_slab_pages)
7442 return NODE_RECLAIM_FULL;
7443
7444 /*
7445 * Do not scan if the allocation should not be delayed.
7446 */
7447 if (!gfpflags_allow_blocking(gfp_mask) || (current->flags & PF_MEMALLOC))
7448 return NODE_RECLAIM_NOSCAN;
7449
7450 /*
7451 * Only run node reclaim on the local node or on nodes that do not
7452 * have associated processors. This will favor the local processor
7453 * over remote processors and spread off node memory allocations
7454 * as wide as possible.
7455 */
7456 if (node_state(pgdat->node_id, N_CPU) && pgdat->node_id != numa_node_id())
7457 return NODE_RECLAIM_NOSCAN;
7458
7459 if (test_and_set_bit(PGDAT_RECLAIM_LOCKED, &pgdat->flags))
7460 return NODE_RECLAIM_NOSCAN;
7461
7462 ret = __node_reclaim(pgdat, gfp_mask, order);
7463 clear_bit(PGDAT_RECLAIM_LOCKED, &pgdat->flags);
7464
7465 if (!ret)
7466 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
7467
7468 return ret;
7469}
7470#endif
7471
7472/**
7473 * check_move_unevictable_folios - Move evictable folios to appropriate zone
7474 * lru list
7475 * @fbatch: Batch of lru folios to check.
7476 *
7477 * Checks folios for evictability, if an evictable folio is in the unevictable
7478 * lru list, moves it to the appropriate evictable lru list. This function
7479 * should be only used for lru folios.
7480 */
7481void check_move_unevictable_folios(struct folio_batch *fbatch)
7482{
7483 struct lruvec *lruvec = NULL;
7484 int pgscanned = 0;
7485 int pgrescued = 0;
7486 int i;
7487
7488 for (i = 0; i < fbatch->nr; i++) {
7489 struct folio *folio = fbatch->folios[i];
7490 int nr_pages = folio_nr_pages(folio);
7491
7492 pgscanned += nr_pages;
7493
7494 /* block memcg migration while the folio moves between lrus */
7495 if (!folio_test_clear_lru(folio))
7496 continue;
7497
7498 lruvec = folio_lruvec_relock_irq(folio, lruvec);
7499 if (folio_evictable(folio) && folio_test_unevictable(folio)) {
7500 lruvec_del_folio(lruvec, folio);
7501 folio_clear_unevictable(folio);
7502 lruvec_add_folio(lruvec, folio);
7503 pgrescued += nr_pages;
7504 }
7505 folio_set_lru(folio);
7506 }
7507
7508 if (lruvec) {
7509 __count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
7510 __count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned);
7511 unlock_page_lruvec_irq(lruvec);
7512 } else if (pgscanned) {
7513 count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned);
7514 }
7515}
7516EXPORT_SYMBOL_GPL(check_move_unevictable_folios);
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
4 *
5 * Swap reorganised 29.12.95, Stephen Tweedie.
6 * kswapd added: 7.1.96 sct
7 * Removed kswapd_ctl limits, and swap out as many pages as needed
8 * to bring the system back to freepages.high: 2.4.97, Rik van Riel.
9 * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
10 * Multiqueue VM started 5.8.00, Rik van Riel.
11 */
12
13#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
14
15#include <linux/mm.h>
16#include <linux/sched/mm.h>
17#include <linux/module.h>
18#include <linux/gfp.h>
19#include <linux/kernel_stat.h>
20#include <linux/swap.h>
21#include <linux/pagemap.h>
22#include <linux/init.h>
23#include <linux/highmem.h>
24#include <linux/vmpressure.h>
25#include <linux/vmstat.h>
26#include <linux/file.h>
27#include <linux/writeback.h>
28#include <linux/blkdev.h>
29#include <linux/buffer_head.h> /* for buffer_heads_over_limit */
30#include <linux/mm_inline.h>
31#include <linux/backing-dev.h>
32#include <linux/rmap.h>
33#include <linux/topology.h>
34#include <linux/cpu.h>
35#include <linux/cpuset.h>
36#include <linux/compaction.h>
37#include <linux/notifier.h>
38#include <linux/rwsem.h>
39#include <linux/delay.h>
40#include <linux/kthread.h>
41#include <linux/freezer.h>
42#include <linux/memcontrol.h>
43#include <linux/migrate.h>
44#include <linux/delayacct.h>
45#include <linux/sysctl.h>
46#include <linux/memory-tiers.h>
47#include <linux/oom.h>
48#include <linux/pagevec.h>
49#include <linux/prefetch.h>
50#include <linux/printk.h>
51#include <linux/dax.h>
52#include <linux/psi.h>
53#include <linux/pagewalk.h>
54#include <linux/shmem_fs.h>
55#include <linux/ctype.h>
56#include <linux/debugfs.h>
57#include <linux/khugepaged.h>
58
59#include <asm/tlbflush.h>
60#include <asm/div64.h>
61
62#include <linux/swapops.h>
63#include <linux/balloon_compaction.h>
64#include <linux/sched/sysctl.h>
65
66#include "internal.h"
67#include "swap.h"
68
69#define CREATE_TRACE_POINTS
70#include <trace/events/vmscan.h>
71
72struct scan_control {
73 /* How many pages shrink_list() should reclaim */
74 unsigned long nr_to_reclaim;
75
76 /*
77 * Nodemask of nodes allowed by the caller. If NULL, all nodes
78 * are scanned.
79 */
80 nodemask_t *nodemask;
81
82 /*
83 * The memory cgroup that hit its limit and as a result is the
84 * primary target of this reclaim invocation.
85 */
86 struct mem_cgroup *target_mem_cgroup;
87
88 /*
89 * Scan pressure balancing between anon and file LRUs
90 */
91 unsigned long anon_cost;
92 unsigned long file_cost;
93
94 /* Can active folios be deactivated as part of reclaim? */
95#define DEACTIVATE_ANON 1
96#define DEACTIVATE_FILE 2
97 unsigned int may_deactivate:2;
98 unsigned int force_deactivate:1;
99 unsigned int skipped_deactivate:1;
100
101 /* Writepage batching in laptop mode; RECLAIM_WRITE */
102 unsigned int may_writepage:1;
103
104 /* Can mapped folios be reclaimed? */
105 unsigned int may_unmap:1;
106
107 /* Can folios be swapped as part of reclaim? */
108 unsigned int may_swap:1;
109
110 /* Proactive reclaim invoked by userspace through memory.reclaim */
111 unsigned int proactive:1;
112
113 /*
114 * Cgroup memory below memory.low is protected as long as we
115 * don't threaten to OOM. If any cgroup is reclaimed at
116 * reduced force or passed over entirely due to its memory.low
117 * setting (memcg_low_skipped), and nothing is reclaimed as a
118 * result, then go back for one more cycle that reclaims the protected
119 * memory (memcg_low_reclaim) to avert OOM.
120 */
121 unsigned int memcg_low_reclaim:1;
122 unsigned int memcg_low_skipped:1;
123
124 unsigned int hibernation_mode:1;
125
126 /* One of the zones is ready for compaction */
127 unsigned int compaction_ready:1;
128
129 /* There is easily reclaimable cold cache in the current node */
130 unsigned int cache_trim_mode:1;
131
132 /* The file folios on the current node are dangerously low */
133 unsigned int file_is_tiny:1;
134
135 /* Always discard instead of demoting to lower tier memory */
136 unsigned int no_demotion:1;
137
138#ifdef CONFIG_LRU_GEN
139 /* help kswapd make better choices among multiple memcgs */
140 unsigned int memcgs_need_aging:1;
141 unsigned long last_reclaimed;
142#endif
143
144 /* Allocation order */
145 s8 order;
146
147 /* Scan (total_size >> priority) pages at once */
148 s8 priority;
149
150 /* The highest zone to isolate folios for reclaim from */
151 s8 reclaim_idx;
152
153 /* This context's GFP mask */
154 gfp_t gfp_mask;
155
156 /* Incremented by the number of inactive pages that were scanned */
157 unsigned long nr_scanned;
158
159 /* Number of pages freed so far during a call to shrink_zones() */
160 unsigned long nr_reclaimed;
161
162 struct {
163 unsigned int dirty;
164 unsigned int unqueued_dirty;
165 unsigned int congested;
166 unsigned int writeback;
167 unsigned int immediate;
168 unsigned int file_taken;
169 unsigned int taken;
170 } nr;
171
172 /* for recording the reclaimed slab by now */
173 struct reclaim_state reclaim_state;
174};
175
176#ifdef ARCH_HAS_PREFETCHW
177#define prefetchw_prev_lru_folio(_folio, _base, _field) \
178 do { \
179 if ((_folio)->lru.prev != _base) { \
180 struct folio *prev; \
181 \
182 prev = lru_to_folio(&(_folio->lru)); \
183 prefetchw(&prev->_field); \
184 } \
185 } while (0)
186#else
187#define prefetchw_prev_lru_folio(_folio, _base, _field) do { } while (0)
188#endif
189
190/*
191 * From 0 .. 200. Higher means more swappy.
192 */
193int vm_swappiness = 60;
194
195static void set_task_reclaim_state(struct task_struct *task,
196 struct reclaim_state *rs)
197{
198 /* Check for an overwrite */
199 WARN_ON_ONCE(rs && task->reclaim_state);
200
201 /* Check for the nulling of an already-nulled member */
202 WARN_ON_ONCE(!rs && !task->reclaim_state);
203
204 task->reclaim_state = rs;
205}
206
207LIST_HEAD(shrinker_list);
208DECLARE_RWSEM(shrinker_rwsem);
209
210#ifdef CONFIG_MEMCG
211static int shrinker_nr_max;
212
213/* The shrinker_info is expanded in a batch of BITS_PER_LONG */
214static inline int shrinker_map_size(int nr_items)
215{
216 return (DIV_ROUND_UP(nr_items, BITS_PER_LONG) * sizeof(unsigned long));
217}
218
219static inline int shrinker_defer_size(int nr_items)
220{
221 return (round_up(nr_items, BITS_PER_LONG) * sizeof(atomic_long_t));
222}
223
224static struct shrinker_info *shrinker_info_protected(struct mem_cgroup *memcg,
225 int nid)
226{
227 return rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_info,
228 lockdep_is_held(&shrinker_rwsem));
229}
230
231static int expand_one_shrinker_info(struct mem_cgroup *memcg,
232 int map_size, int defer_size,
233 int old_map_size, int old_defer_size)
234{
235 struct shrinker_info *new, *old;
236 struct mem_cgroup_per_node *pn;
237 int nid;
238 int size = map_size + defer_size;
239
240 for_each_node(nid) {
241 pn = memcg->nodeinfo[nid];
242 old = shrinker_info_protected(memcg, nid);
243 /* Not yet online memcg */
244 if (!old)
245 return 0;
246
247 new = kvmalloc_node(sizeof(*new) + size, GFP_KERNEL, nid);
248 if (!new)
249 return -ENOMEM;
250
251 new->nr_deferred = (atomic_long_t *)(new + 1);
252 new->map = (void *)new->nr_deferred + defer_size;
253
254 /* map: set all old bits, clear all new bits */
255 memset(new->map, (int)0xff, old_map_size);
256 memset((void *)new->map + old_map_size, 0, map_size - old_map_size);
257 /* nr_deferred: copy old values, clear all new values */
258 memcpy(new->nr_deferred, old->nr_deferred, old_defer_size);
259 memset((void *)new->nr_deferred + old_defer_size, 0,
260 defer_size - old_defer_size);
261
262 rcu_assign_pointer(pn->shrinker_info, new);
263 kvfree_rcu(old, rcu);
264 }
265
266 return 0;
267}
268
269void free_shrinker_info(struct mem_cgroup *memcg)
270{
271 struct mem_cgroup_per_node *pn;
272 struct shrinker_info *info;
273 int nid;
274
275 for_each_node(nid) {
276 pn = memcg->nodeinfo[nid];
277 info = rcu_dereference_protected(pn->shrinker_info, true);
278 kvfree(info);
279 rcu_assign_pointer(pn->shrinker_info, NULL);
280 }
281}
282
283int alloc_shrinker_info(struct mem_cgroup *memcg)
284{
285 struct shrinker_info *info;
286 int nid, size, ret = 0;
287 int map_size, defer_size = 0;
288
289 down_write(&shrinker_rwsem);
290 map_size = shrinker_map_size(shrinker_nr_max);
291 defer_size = shrinker_defer_size(shrinker_nr_max);
292 size = map_size + defer_size;
293 for_each_node(nid) {
294 info = kvzalloc_node(sizeof(*info) + size, GFP_KERNEL, nid);
295 if (!info) {
296 free_shrinker_info(memcg);
297 ret = -ENOMEM;
298 break;
299 }
300 info->nr_deferred = (atomic_long_t *)(info + 1);
301 info->map = (void *)info->nr_deferred + defer_size;
302 rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_info, info);
303 }
304 up_write(&shrinker_rwsem);
305
306 return ret;
307}
308
309static inline bool need_expand(int nr_max)
310{
311 return round_up(nr_max, BITS_PER_LONG) >
312 round_up(shrinker_nr_max, BITS_PER_LONG);
313}
314
315static int expand_shrinker_info(int new_id)
316{
317 int ret = 0;
318 int new_nr_max = new_id + 1;
319 int map_size, defer_size = 0;
320 int old_map_size, old_defer_size = 0;
321 struct mem_cgroup *memcg;
322
323 if (!need_expand(new_nr_max))
324 goto out;
325
326 if (!root_mem_cgroup)
327 goto out;
328
329 lockdep_assert_held(&shrinker_rwsem);
330
331 map_size = shrinker_map_size(new_nr_max);
332 defer_size = shrinker_defer_size(new_nr_max);
333 old_map_size = shrinker_map_size(shrinker_nr_max);
334 old_defer_size = shrinker_defer_size(shrinker_nr_max);
335
336 memcg = mem_cgroup_iter(NULL, NULL, NULL);
337 do {
338 ret = expand_one_shrinker_info(memcg, map_size, defer_size,
339 old_map_size, old_defer_size);
340 if (ret) {
341 mem_cgroup_iter_break(NULL, memcg);
342 goto out;
343 }
344 } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
345out:
346 if (!ret)
347 shrinker_nr_max = new_nr_max;
348
349 return ret;
350}
351
352void set_shrinker_bit(struct mem_cgroup *memcg, int nid, int shrinker_id)
353{
354 if (shrinker_id >= 0 && memcg && !mem_cgroup_is_root(memcg)) {
355 struct shrinker_info *info;
356
357 rcu_read_lock();
358 info = rcu_dereference(memcg->nodeinfo[nid]->shrinker_info);
359 /* Pairs with smp mb in shrink_slab() */
360 smp_mb__before_atomic();
361 set_bit(shrinker_id, info->map);
362 rcu_read_unlock();
363 }
364}
365
366static DEFINE_IDR(shrinker_idr);
367
368static int prealloc_memcg_shrinker(struct shrinker *shrinker)
369{
370 int id, ret = -ENOMEM;
371
372 if (mem_cgroup_disabled())
373 return -ENOSYS;
374
375 down_write(&shrinker_rwsem);
376 /* This may call shrinker, so it must use down_read_trylock() */
377 id = idr_alloc(&shrinker_idr, shrinker, 0, 0, GFP_KERNEL);
378 if (id < 0)
379 goto unlock;
380
381 if (id >= shrinker_nr_max) {
382 if (expand_shrinker_info(id)) {
383 idr_remove(&shrinker_idr, id);
384 goto unlock;
385 }
386 }
387 shrinker->id = id;
388 ret = 0;
389unlock:
390 up_write(&shrinker_rwsem);
391 return ret;
392}
393
394static void unregister_memcg_shrinker(struct shrinker *shrinker)
395{
396 int id = shrinker->id;
397
398 BUG_ON(id < 0);
399
400 lockdep_assert_held(&shrinker_rwsem);
401
402 idr_remove(&shrinker_idr, id);
403}
404
405static long xchg_nr_deferred_memcg(int nid, struct shrinker *shrinker,
406 struct mem_cgroup *memcg)
407{
408 struct shrinker_info *info;
409
410 info = shrinker_info_protected(memcg, nid);
411 return atomic_long_xchg(&info->nr_deferred[shrinker->id], 0);
412}
413
414static long add_nr_deferred_memcg(long nr, int nid, struct shrinker *shrinker,
415 struct mem_cgroup *memcg)
416{
417 struct shrinker_info *info;
418
419 info = shrinker_info_protected(memcg, nid);
420 return atomic_long_add_return(nr, &info->nr_deferred[shrinker->id]);
421}
422
423void reparent_shrinker_deferred(struct mem_cgroup *memcg)
424{
425 int i, nid;
426 long nr;
427 struct mem_cgroup *parent;
428 struct shrinker_info *child_info, *parent_info;
429
430 parent = parent_mem_cgroup(memcg);
431 if (!parent)
432 parent = root_mem_cgroup;
433
434 /* Prevent from concurrent shrinker_info expand */
435 down_read(&shrinker_rwsem);
436 for_each_node(nid) {
437 child_info = shrinker_info_protected(memcg, nid);
438 parent_info = shrinker_info_protected(parent, nid);
439 for (i = 0; i < shrinker_nr_max; i++) {
440 nr = atomic_long_read(&child_info->nr_deferred[i]);
441 atomic_long_add(nr, &parent_info->nr_deferred[i]);
442 }
443 }
444 up_read(&shrinker_rwsem);
445}
446
447static bool cgroup_reclaim(struct scan_control *sc)
448{
449 return sc->target_mem_cgroup;
450}
451
452/**
453 * writeback_throttling_sane - is the usual dirty throttling mechanism available?
454 * @sc: scan_control in question
455 *
456 * The normal page dirty throttling mechanism in balance_dirty_pages() is
457 * completely broken with the legacy memcg and direct stalling in
458 * shrink_folio_list() is used for throttling instead, which lacks all the
459 * niceties such as fairness, adaptive pausing, bandwidth proportional
460 * allocation and configurability.
461 *
462 * This function tests whether the vmscan currently in progress can assume
463 * that the normal dirty throttling mechanism is operational.
464 */
465static bool writeback_throttling_sane(struct scan_control *sc)
466{
467 if (!cgroup_reclaim(sc))
468 return true;
469#ifdef CONFIG_CGROUP_WRITEBACK
470 if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
471 return true;
472#endif
473 return false;
474}
475#else
476static int prealloc_memcg_shrinker(struct shrinker *shrinker)
477{
478 return -ENOSYS;
479}
480
481static void unregister_memcg_shrinker(struct shrinker *shrinker)
482{
483}
484
485static long xchg_nr_deferred_memcg(int nid, struct shrinker *shrinker,
486 struct mem_cgroup *memcg)
487{
488 return 0;
489}
490
491static long add_nr_deferred_memcg(long nr, int nid, struct shrinker *shrinker,
492 struct mem_cgroup *memcg)
493{
494 return 0;
495}
496
497static bool cgroup_reclaim(struct scan_control *sc)
498{
499 return false;
500}
501
502static bool writeback_throttling_sane(struct scan_control *sc)
503{
504 return true;
505}
506#endif
507
508static long xchg_nr_deferred(struct shrinker *shrinker,
509 struct shrink_control *sc)
510{
511 int nid = sc->nid;
512
513 if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
514 nid = 0;
515
516 if (sc->memcg &&
517 (shrinker->flags & SHRINKER_MEMCG_AWARE))
518 return xchg_nr_deferred_memcg(nid, shrinker,
519 sc->memcg);
520
521 return atomic_long_xchg(&shrinker->nr_deferred[nid], 0);
522}
523
524
525static long add_nr_deferred(long nr, struct shrinker *shrinker,
526 struct shrink_control *sc)
527{
528 int nid = sc->nid;
529
530 if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
531 nid = 0;
532
533 if (sc->memcg &&
534 (shrinker->flags & SHRINKER_MEMCG_AWARE))
535 return add_nr_deferred_memcg(nr, nid, shrinker,
536 sc->memcg);
537
538 return atomic_long_add_return(nr, &shrinker->nr_deferred[nid]);
539}
540
541static bool can_demote(int nid, struct scan_control *sc)
542{
543 if (!numa_demotion_enabled)
544 return false;
545 if (sc && sc->no_demotion)
546 return false;
547 if (next_demotion_node(nid) == NUMA_NO_NODE)
548 return false;
549
550 return true;
551}
552
553static inline bool can_reclaim_anon_pages(struct mem_cgroup *memcg,
554 int nid,
555 struct scan_control *sc)
556{
557 if (memcg == NULL) {
558 /*
559 * For non-memcg reclaim, is there
560 * space in any swap device?
561 */
562 if (get_nr_swap_pages() > 0)
563 return true;
564 } else {
565 /* Is the memcg below its swap limit? */
566 if (mem_cgroup_get_nr_swap_pages(memcg) > 0)
567 return true;
568 }
569
570 /*
571 * The page can not be swapped.
572 *
573 * Can it be reclaimed from this node via demotion?
574 */
575 return can_demote(nid, sc);
576}
577
578/*
579 * This misses isolated folios which are not accounted for to save counters.
580 * As the data only determines if reclaim or compaction continues, it is
581 * not expected that isolated folios will be a dominating factor.
582 */
583unsigned long zone_reclaimable_pages(struct zone *zone)
584{
585 unsigned long nr;
586
587 nr = zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_FILE) +
588 zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_FILE);
589 if (can_reclaim_anon_pages(NULL, zone_to_nid(zone), NULL))
590 nr += zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_ANON) +
591 zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_ANON);
592
593 return nr;
594}
595
596/**
597 * lruvec_lru_size - Returns the number of pages on the given LRU list.
598 * @lruvec: lru vector
599 * @lru: lru to use
600 * @zone_idx: zones to consider (use MAX_NR_ZONES - 1 for the whole LRU list)
601 */
602static unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru,
603 int zone_idx)
604{
605 unsigned long size = 0;
606 int zid;
607
608 for (zid = 0; zid <= zone_idx; zid++) {
609 struct zone *zone = &lruvec_pgdat(lruvec)->node_zones[zid];
610
611 if (!managed_zone(zone))
612 continue;
613
614 if (!mem_cgroup_disabled())
615 size += mem_cgroup_get_zone_lru_size(lruvec, lru, zid);
616 else
617 size += zone_page_state(zone, NR_ZONE_LRU_BASE + lru);
618 }
619 return size;
620}
621
622/*
623 * Add a shrinker callback to be called from the vm.
624 */
625static int __prealloc_shrinker(struct shrinker *shrinker)
626{
627 unsigned int size;
628 int err;
629
630 if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
631 err = prealloc_memcg_shrinker(shrinker);
632 if (err != -ENOSYS)
633 return err;
634
635 shrinker->flags &= ~SHRINKER_MEMCG_AWARE;
636 }
637
638 size = sizeof(*shrinker->nr_deferred);
639 if (shrinker->flags & SHRINKER_NUMA_AWARE)
640 size *= nr_node_ids;
641
642 shrinker->nr_deferred = kzalloc(size, GFP_KERNEL);
643 if (!shrinker->nr_deferred)
644 return -ENOMEM;
645
646 return 0;
647}
648
649#ifdef CONFIG_SHRINKER_DEBUG
650int prealloc_shrinker(struct shrinker *shrinker, const char *fmt, ...)
651{
652 va_list ap;
653 int err;
654
655 va_start(ap, fmt);
656 shrinker->name = kvasprintf_const(GFP_KERNEL, fmt, ap);
657 va_end(ap);
658 if (!shrinker->name)
659 return -ENOMEM;
660
661 err = __prealloc_shrinker(shrinker);
662 if (err) {
663 kfree_const(shrinker->name);
664 shrinker->name = NULL;
665 }
666
667 return err;
668}
669#else
670int prealloc_shrinker(struct shrinker *shrinker, const char *fmt, ...)
671{
672 return __prealloc_shrinker(shrinker);
673}
674#endif
675
676void free_prealloced_shrinker(struct shrinker *shrinker)
677{
678#ifdef CONFIG_SHRINKER_DEBUG
679 kfree_const(shrinker->name);
680 shrinker->name = NULL;
681#endif
682 if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
683 down_write(&shrinker_rwsem);
684 unregister_memcg_shrinker(shrinker);
685 up_write(&shrinker_rwsem);
686 return;
687 }
688
689 kfree(shrinker->nr_deferred);
690 shrinker->nr_deferred = NULL;
691}
692
693void register_shrinker_prepared(struct shrinker *shrinker)
694{
695 down_write(&shrinker_rwsem);
696 list_add_tail(&shrinker->list, &shrinker_list);
697 shrinker->flags |= SHRINKER_REGISTERED;
698 shrinker_debugfs_add(shrinker);
699 up_write(&shrinker_rwsem);
700}
701
702static int __register_shrinker(struct shrinker *shrinker)
703{
704 int err = __prealloc_shrinker(shrinker);
705
706 if (err)
707 return err;
708 register_shrinker_prepared(shrinker);
709 return 0;
710}
711
712#ifdef CONFIG_SHRINKER_DEBUG
713int register_shrinker(struct shrinker *shrinker, const char *fmt, ...)
714{
715 va_list ap;
716 int err;
717
718 va_start(ap, fmt);
719 shrinker->name = kvasprintf_const(GFP_KERNEL, fmt, ap);
720 va_end(ap);
721 if (!shrinker->name)
722 return -ENOMEM;
723
724 err = __register_shrinker(shrinker);
725 if (err) {
726 kfree_const(shrinker->name);
727 shrinker->name = NULL;
728 }
729 return err;
730}
731#else
732int register_shrinker(struct shrinker *shrinker, const char *fmt, ...)
733{
734 return __register_shrinker(shrinker);
735}
736#endif
737EXPORT_SYMBOL(register_shrinker);
738
739/*
740 * Remove one
741 */
742void unregister_shrinker(struct shrinker *shrinker)
743{
744 struct dentry *debugfs_entry;
745
746 if (!(shrinker->flags & SHRINKER_REGISTERED))
747 return;
748
749 down_write(&shrinker_rwsem);
750 list_del(&shrinker->list);
751 shrinker->flags &= ~SHRINKER_REGISTERED;
752 if (shrinker->flags & SHRINKER_MEMCG_AWARE)
753 unregister_memcg_shrinker(shrinker);
754 debugfs_entry = shrinker_debugfs_remove(shrinker);
755 up_write(&shrinker_rwsem);
756
757 debugfs_remove_recursive(debugfs_entry);
758
759 kfree(shrinker->nr_deferred);
760 shrinker->nr_deferred = NULL;
761}
762EXPORT_SYMBOL(unregister_shrinker);
763
764/**
765 * synchronize_shrinkers - Wait for all running shrinkers to complete.
766 *
767 * This is equivalent to calling unregister_shrink() and register_shrinker(),
768 * but atomically and with less overhead. This is useful to guarantee that all
769 * shrinker invocations have seen an update, before freeing memory, similar to
770 * rcu.
771 */
772void synchronize_shrinkers(void)
773{
774 down_write(&shrinker_rwsem);
775 up_write(&shrinker_rwsem);
776}
777EXPORT_SYMBOL(synchronize_shrinkers);
778
779#define SHRINK_BATCH 128
780
781static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
782 struct shrinker *shrinker, int priority)
783{
784 unsigned long freed = 0;
785 unsigned long long delta;
786 long total_scan;
787 long freeable;
788 long nr;
789 long new_nr;
790 long batch_size = shrinker->batch ? shrinker->batch
791 : SHRINK_BATCH;
792 long scanned = 0, next_deferred;
793
794 freeable = shrinker->count_objects(shrinker, shrinkctl);
795 if (freeable == 0 || freeable == SHRINK_EMPTY)
796 return freeable;
797
798 /*
799 * copy the current shrinker scan count into a local variable
800 * and zero it so that other concurrent shrinker invocations
801 * don't also do this scanning work.
802 */
803 nr = xchg_nr_deferred(shrinker, shrinkctl);
804
805 if (shrinker->seeks) {
806 delta = freeable >> priority;
807 delta *= 4;
808 do_div(delta, shrinker->seeks);
809 } else {
810 /*
811 * These objects don't require any IO to create. Trim
812 * them aggressively under memory pressure to keep
813 * them from causing refetches in the IO caches.
814 */
815 delta = freeable / 2;
816 }
817
818 total_scan = nr >> priority;
819 total_scan += delta;
820 total_scan = min(total_scan, (2 * freeable));
821
822 trace_mm_shrink_slab_start(shrinker, shrinkctl, nr,
823 freeable, delta, total_scan, priority);
824
825 /*
826 * Normally, we should not scan less than batch_size objects in one
827 * pass to avoid too frequent shrinker calls, but if the slab has less
828 * than batch_size objects in total and we are really tight on memory,
829 * we will try to reclaim all available objects, otherwise we can end
830 * up failing allocations although there are plenty of reclaimable
831 * objects spread over several slabs with usage less than the
832 * batch_size.
833 *
834 * We detect the "tight on memory" situations by looking at the total
835 * number of objects we want to scan (total_scan). If it is greater
836 * than the total number of objects on slab (freeable), we must be
837 * scanning at high prio and therefore should try to reclaim as much as
838 * possible.
839 */
840 while (total_scan >= batch_size ||
841 total_scan >= freeable) {
842 unsigned long ret;
843 unsigned long nr_to_scan = min(batch_size, total_scan);
844
845 shrinkctl->nr_to_scan = nr_to_scan;
846 shrinkctl->nr_scanned = nr_to_scan;
847 ret = shrinker->scan_objects(shrinker, shrinkctl);
848 if (ret == SHRINK_STOP)
849 break;
850 freed += ret;
851
852 count_vm_events(SLABS_SCANNED, shrinkctl->nr_scanned);
853 total_scan -= shrinkctl->nr_scanned;
854 scanned += shrinkctl->nr_scanned;
855
856 cond_resched();
857 }
858
859 /*
860 * The deferred work is increased by any new work (delta) that wasn't
861 * done, decreased by old deferred work that was done now.
862 *
863 * And it is capped to two times of the freeable items.
864 */
865 next_deferred = max_t(long, (nr + delta - scanned), 0);
866 next_deferred = min(next_deferred, (2 * freeable));
867
868 /*
869 * move the unused scan count back into the shrinker in a
870 * manner that handles concurrent updates.
871 */
872 new_nr = add_nr_deferred(next_deferred, shrinker, shrinkctl);
873
874 trace_mm_shrink_slab_end(shrinker, shrinkctl->nid, freed, nr, new_nr, total_scan);
875 return freed;
876}
877
878#ifdef CONFIG_MEMCG
879static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
880 struct mem_cgroup *memcg, int priority)
881{
882 struct shrinker_info *info;
883 unsigned long ret, freed = 0;
884 int i;
885
886 if (!mem_cgroup_online(memcg))
887 return 0;
888
889 if (!down_read_trylock(&shrinker_rwsem))
890 return 0;
891
892 info = shrinker_info_protected(memcg, nid);
893 if (unlikely(!info))
894 goto unlock;
895
896 for_each_set_bit(i, info->map, shrinker_nr_max) {
897 struct shrink_control sc = {
898 .gfp_mask = gfp_mask,
899 .nid = nid,
900 .memcg = memcg,
901 };
902 struct shrinker *shrinker;
903
904 shrinker = idr_find(&shrinker_idr, i);
905 if (unlikely(!shrinker || !(shrinker->flags & SHRINKER_REGISTERED))) {
906 if (!shrinker)
907 clear_bit(i, info->map);
908 continue;
909 }
910
911 /* Call non-slab shrinkers even though kmem is disabled */
912 if (!memcg_kmem_enabled() &&
913 !(shrinker->flags & SHRINKER_NONSLAB))
914 continue;
915
916 ret = do_shrink_slab(&sc, shrinker, priority);
917 if (ret == SHRINK_EMPTY) {
918 clear_bit(i, info->map);
919 /*
920 * After the shrinker reported that it had no objects to
921 * free, but before we cleared the corresponding bit in
922 * the memcg shrinker map, a new object might have been
923 * added. To make sure, we have the bit set in this
924 * case, we invoke the shrinker one more time and reset
925 * the bit if it reports that it is not empty anymore.
926 * The memory barrier here pairs with the barrier in
927 * set_shrinker_bit():
928 *
929 * list_lru_add() shrink_slab_memcg()
930 * list_add_tail() clear_bit()
931 * <MB> <MB>
932 * set_bit() do_shrink_slab()
933 */
934 smp_mb__after_atomic();
935 ret = do_shrink_slab(&sc, shrinker, priority);
936 if (ret == SHRINK_EMPTY)
937 ret = 0;
938 else
939 set_shrinker_bit(memcg, nid, i);
940 }
941 freed += ret;
942
943 if (rwsem_is_contended(&shrinker_rwsem)) {
944 freed = freed ? : 1;
945 break;
946 }
947 }
948unlock:
949 up_read(&shrinker_rwsem);
950 return freed;
951}
952#else /* CONFIG_MEMCG */
953static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
954 struct mem_cgroup *memcg, int priority)
955{
956 return 0;
957}
958#endif /* CONFIG_MEMCG */
959
960/**
961 * shrink_slab - shrink slab caches
962 * @gfp_mask: allocation context
963 * @nid: node whose slab caches to target
964 * @memcg: memory cgroup whose slab caches to target
965 * @priority: the reclaim priority
966 *
967 * Call the shrink functions to age shrinkable caches.
968 *
969 * @nid is passed along to shrinkers with SHRINKER_NUMA_AWARE set,
970 * unaware shrinkers will receive a node id of 0 instead.
971 *
972 * @memcg specifies the memory cgroup to target. Unaware shrinkers
973 * are called only if it is the root cgroup.
974 *
975 * @priority is sc->priority, we take the number of objects and >> by priority
976 * in order to get the scan target.
977 *
978 * Returns the number of reclaimed slab objects.
979 */
980static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
981 struct mem_cgroup *memcg,
982 int priority)
983{
984 unsigned long ret, freed = 0;
985 struct shrinker *shrinker;
986
987 /*
988 * The root memcg might be allocated even though memcg is disabled
989 * via "cgroup_disable=memory" boot parameter. This could make
990 * mem_cgroup_is_root() return false, then just run memcg slab
991 * shrink, but skip global shrink. This may result in premature
992 * oom.
993 */
994 if (!mem_cgroup_disabled() && !mem_cgroup_is_root(memcg))
995 return shrink_slab_memcg(gfp_mask, nid, memcg, priority);
996
997 if (!down_read_trylock(&shrinker_rwsem))
998 goto out;
999
1000 list_for_each_entry(shrinker, &shrinker_list, list) {
1001 struct shrink_control sc = {
1002 .gfp_mask = gfp_mask,
1003 .nid = nid,
1004 .memcg = memcg,
1005 };
1006
1007 ret = do_shrink_slab(&sc, shrinker, priority);
1008 if (ret == SHRINK_EMPTY)
1009 ret = 0;
1010 freed += ret;
1011 /*
1012 * Bail out if someone want to register a new shrinker to
1013 * prevent the registration from being stalled for long periods
1014 * by parallel ongoing shrinking.
1015 */
1016 if (rwsem_is_contended(&shrinker_rwsem)) {
1017 freed = freed ? : 1;
1018 break;
1019 }
1020 }
1021
1022 up_read(&shrinker_rwsem);
1023out:
1024 cond_resched();
1025 return freed;
1026}
1027
1028static unsigned long drop_slab_node(int nid)
1029{
1030 unsigned long freed = 0;
1031 struct mem_cgroup *memcg = NULL;
1032
1033 memcg = mem_cgroup_iter(NULL, NULL, NULL);
1034 do {
1035 freed += shrink_slab(GFP_KERNEL, nid, memcg, 0);
1036 } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
1037
1038 return freed;
1039}
1040
1041void drop_slab(void)
1042{
1043 int nid;
1044 int shift = 0;
1045 unsigned long freed;
1046
1047 do {
1048 freed = 0;
1049 for_each_online_node(nid) {
1050 if (fatal_signal_pending(current))
1051 return;
1052
1053 freed += drop_slab_node(nid);
1054 }
1055 } while ((freed >> shift++) > 1);
1056}
1057
1058static int reclaimer_offset(void)
1059{
1060 BUILD_BUG_ON(PGSTEAL_DIRECT - PGSTEAL_KSWAPD !=
1061 PGDEMOTE_DIRECT - PGDEMOTE_KSWAPD);
1062 BUILD_BUG_ON(PGSTEAL_DIRECT - PGSTEAL_KSWAPD !=
1063 PGSCAN_DIRECT - PGSCAN_KSWAPD);
1064 BUILD_BUG_ON(PGSTEAL_KHUGEPAGED - PGSTEAL_KSWAPD !=
1065 PGDEMOTE_KHUGEPAGED - PGDEMOTE_KSWAPD);
1066 BUILD_BUG_ON(PGSTEAL_KHUGEPAGED - PGSTEAL_KSWAPD !=
1067 PGSCAN_KHUGEPAGED - PGSCAN_KSWAPD);
1068
1069 if (current_is_kswapd())
1070 return 0;
1071 if (current_is_khugepaged())
1072 return PGSTEAL_KHUGEPAGED - PGSTEAL_KSWAPD;
1073 return PGSTEAL_DIRECT - PGSTEAL_KSWAPD;
1074}
1075
1076static inline int is_page_cache_freeable(struct folio *folio)
1077{
1078 /*
1079 * A freeable page cache folio is referenced only by the caller
1080 * that isolated the folio, the page cache and optional filesystem
1081 * private data at folio->private.
1082 */
1083 return folio_ref_count(folio) - folio_test_private(folio) ==
1084 1 + folio_nr_pages(folio);
1085}
1086
1087/*
1088 * We detected a synchronous write error writing a folio out. Probably
1089 * -ENOSPC. We need to propagate that into the address_space for a subsequent
1090 * fsync(), msync() or close().
1091 *
1092 * The tricky part is that after writepage we cannot touch the mapping: nothing
1093 * prevents it from being freed up. But we have a ref on the folio and once
1094 * that folio is locked, the mapping is pinned.
1095 *
1096 * We're allowed to run sleeping folio_lock() here because we know the caller has
1097 * __GFP_FS.
1098 */
1099static void handle_write_error(struct address_space *mapping,
1100 struct folio *folio, int error)
1101{
1102 folio_lock(folio);
1103 if (folio_mapping(folio) == mapping)
1104 mapping_set_error(mapping, error);
1105 folio_unlock(folio);
1106}
1107
1108static bool skip_throttle_noprogress(pg_data_t *pgdat)
1109{
1110 int reclaimable = 0, write_pending = 0;
1111 int i;
1112
1113 /*
1114 * If kswapd is disabled, reschedule if necessary but do not
1115 * throttle as the system is likely near OOM.
1116 */
1117 if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES)
1118 return true;
1119
1120 /*
1121 * If there are a lot of dirty/writeback folios then do not
1122 * throttle as throttling will occur when the folios cycle
1123 * towards the end of the LRU if still under writeback.
1124 */
1125 for (i = 0; i < MAX_NR_ZONES; i++) {
1126 struct zone *zone = pgdat->node_zones + i;
1127
1128 if (!managed_zone(zone))
1129 continue;
1130
1131 reclaimable += zone_reclaimable_pages(zone);
1132 write_pending += zone_page_state_snapshot(zone,
1133 NR_ZONE_WRITE_PENDING);
1134 }
1135 if (2 * write_pending <= reclaimable)
1136 return true;
1137
1138 return false;
1139}
1140
1141void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason)
1142{
1143 wait_queue_head_t *wqh = &pgdat->reclaim_wait[reason];
1144 long timeout, ret;
1145 DEFINE_WAIT(wait);
1146
1147 /*
1148 * Do not throttle IO workers, kthreads other than kswapd or
1149 * workqueues. They may be required for reclaim to make
1150 * forward progress (e.g. journalling workqueues or kthreads).
1151 */
1152 if (!current_is_kswapd() &&
1153 current->flags & (PF_IO_WORKER|PF_KTHREAD)) {
1154 cond_resched();
1155 return;
1156 }
1157
1158 /*
1159 * These figures are pulled out of thin air.
1160 * VMSCAN_THROTTLE_ISOLATED is a transient condition based on too many
1161 * parallel reclaimers which is a short-lived event so the timeout is
1162 * short. Failing to make progress or waiting on writeback are
1163 * potentially long-lived events so use a longer timeout. This is shaky
1164 * logic as a failure to make progress could be due to anything from
1165 * writeback to a slow device to excessive referenced folios at the tail
1166 * of the inactive LRU.
1167 */
1168 switch(reason) {
1169 case VMSCAN_THROTTLE_WRITEBACK:
1170 timeout = HZ/10;
1171
1172 if (atomic_inc_return(&pgdat->nr_writeback_throttled) == 1) {
1173 WRITE_ONCE(pgdat->nr_reclaim_start,
1174 node_page_state(pgdat, NR_THROTTLED_WRITTEN));
1175 }
1176
1177 break;
1178 case VMSCAN_THROTTLE_CONGESTED:
1179 fallthrough;
1180 case VMSCAN_THROTTLE_NOPROGRESS:
1181 if (skip_throttle_noprogress(pgdat)) {
1182 cond_resched();
1183 return;
1184 }
1185
1186 timeout = 1;
1187
1188 break;
1189 case VMSCAN_THROTTLE_ISOLATED:
1190 timeout = HZ/50;
1191 break;
1192 default:
1193 WARN_ON_ONCE(1);
1194 timeout = HZ;
1195 break;
1196 }
1197
1198 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
1199 ret = schedule_timeout(timeout);
1200 finish_wait(wqh, &wait);
1201
1202 if (reason == VMSCAN_THROTTLE_WRITEBACK)
1203 atomic_dec(&pgdat->nr_writeback_throttled);
1204
1205 trace_mm_vmscan_throttled(pgdat->node_id, jiffies_to_usecs(timeout),
1206 jiffies_to_usecs(timeout - ret),
1207 reason);
1208}
1209
1210/*
1211 * Account for folios written if tasks are throttled waiting on dirty
1212 * folios to clean. If enough folios have been cleaned since throttling
1213 * started then wakeup the throttled tasks.
1214 */
1215void __acct_reclaim_writeback(pg_data_t *pgdat, struct folio *folio,
1216 int nr_throttled)
1217{
1218 unsigned long nr_written;
1219
1220 node_stat_add_folio(folio, NR_THROTTLED_WRITTEN);
1221
1222 /*
1223 * This is an inaccurate read as the per-cpu deltas may not
1224 * be synchronised. However, given that the system is
1225 * writeback throttled, it is not worth taking the penalty
1226 * of getting an accurate count. At worst, the throttle
1227 * timeout guarantees forward progress.
1228 */
1229 nr_written = node_page_state(pgdat, NR_THROTTLED_WRITTEN) -
1230 READ_ONCE(pgdat->nr_reclaim_start);
1231
1232 if (nr_written > SWAP_CLUSTER_MAX * nr_throttled)
1233 wake_up(&pgdat->reclaim_wait[VMSCAN_THROTTLE_WRITEBACK]);
1234}
1235
1236/* possible outcome of pageout() */
1237typedef enum {
1238 /* failed to write folio out, folio is locked */
1239 PAGE_KEEP,
1240 /* move folio to the active list, folio is locked */
1241 PAGE_ACTIVATE,
1242 /* folio has been sent to the disk successfully, folio is unlocked */
1243 PAGE_SUCCESS,
1244 /* folio is clean and locked */
1245 PAGE_CLEAN,
1246} pageout_t;
1247
1248/*
1249 * pageout is called by shrink_folio_list() for each dirty folio.
1250 * Calls ->writepage().
1251 */
1252static pageout_t pageout(struct folio *folio, struct address_space *mapping,
1253 struct swap_iocb **plug)
1254{
1255 /*
1256 * If the folio is dirty, only perform writeback if that write
1257 * will be non-blocking. To prevent this allocation from being
1258 * stalled by pagecache activity. But note that there may be
1259 * stalls if we need to run get_block(). We could test
1260 * PagePrivate for that.
1261 *
1262 * If this process is currently in __generic_file_write_iter() against
1263 * this folio's queue, we can perform writeback even if that
1264 * will block.
1265 *
1266 * If the folio is swapcache, write it back even if that would
1267 * block, for some throttling. This happens by accident, because
1268 * swap_backing_dev_info is bust: it doesn't reflect the
1269 * congestion state of the swapdevs. Easy to fix, if needed.
1270 */
1271 if (!is_page_cache_freeable(folio))
1272 return PAGE_KEEP;
1273 if (!mapping) {
1274 /*
1275 * Some data journaling orphaned folios can have
1276 * folio->mapping == NULL while being dirty with clean buffers.
1277 */
1278 if (folio_test_private(folio)) {
1279 if (try_to_free_buffers(folio)) {
1280 folio_clear_dirty(folio);
1281 pr_info("%s: orphaned folio\n", __func__);
1282 return PAGE_CLEAN;
1283 }
1284 }
1285 return PAGE_KEEP;
1286 }
1287 if (mapping->a_ops->writepage == NULL)
1288 return PAGE_ACTIVATE;
1289
1290 if (folio_clear_dirty_for_io(folio)) {
1291 int res;
1292 struct writeback_control wbc = {
1293 .sync_mode = WB_SYNC_NONE,
1294 .nr_to_write = SWAP_CLUSTER_MAX,
1295 .range_start = 0,
1296 .range_end = LLONG_MAX,
1297 .for_reclaim = 1,
1298 .swap_plug = plug,
1299 };
1300
1301 folio_set_reclaim(folio);
1302 res = mapping->a_ops->writepage(&folio->page, &wbc);
1303 if (res < 0)
1304 handle_write_error(mapping, folio, res);
1305 if (res == AOP_WRITEPAGE_ACTIVATE) {
1306 folio_clear_reclaim(folio);
1307 return PAGE_ACTIVATE;
1308 }
1309
1310 if (!folio_test_writeback(folio)) {
1311 /* synchronous write or broken a_ops? */
1312 folio_clear_reclaim(folio);
1313 }
1314 trace_mm_vmscan_write_folio(folio);
1315 node_stat_add_folio(folio, NR_VMSCAN_WRITE);
1316 return PAGE_SUCCESS;
1317 }
1318
1319 return PAGE_CLEAN;
1320}
1321
1322/*
1323 * Same as remove_mapping, but if the folio is removed from the mapping, it
1324 * gets returned with a refcount of 0.
1325 */
1326static int __remove_mapping(struct address_space *mapping, struct folio *folio,
1327 bool reclaimed, struct mem_cgroup *target_memcg)
1328{
1329 int refcount;
1330 void *shadow = NULL;
1331
1332 BUG_ON(!folio_test_locked(folio));
1333 BUG_ON(mapping != folio_mapping(folio));
1334
1335 if (!folio_test_swapcache(folio))
1336 spin_lock(&mapping->host->i_lock);
1337 xa_lock_irq(&mapping->i_pages);
1338 /*
1339 * The non racy check for a busy folio.
1340 *
1341 * Must be careful with the order of the tests. When someone has
1342 * a ref to the folio, it may be possible that they dirty it then
1343 * drop the reference. So if the dirty flag is tested before the
1344 * refcount here, then the following race may occur:
1345 *
1346 * get_user_pages(&page);
1347 * [user mapping goes away]
1348 * write_to(page);
1349 * !folio_test_dirty(folio) [good]
1350 * folio_set_dirty(folio);
1351 * folio_put(folio);
1352 * !refcount(folio) [good, discard it]
1353 *
1354 * [oops, our write_to data is lost]
1355 *
1356 * Reversing the order of the tests ensures such a situation cannot
1357 * escape unnoticed. The smp_rmb is needed to ensure the folio->flags
1358 * load is not satisfied before that of folio->_refcount.
1359 *
1360 * Note that if the dirty flag is always set via folio_mark_dirty,
1361 * and thus under the i_pages lock, then this ordering is not required.
1362 */
1363 refcount = 1 + folio_nr_pages(folio);
1364 if (!folio_ref_freeze(folio, refcount))
1365 goto cannot_free;
1366 /* note: atomic_cmpxchg in folio_ref_freeze provides the smp_rmb */
1367 if (unlikely(folio_test_dirty(folio))) {
1368 folio_ref_unfreeze(folio, refcount);
1369 goto cannot_free;
1370 }
1371
1372 if (folio_test_swapcache(folio)) {
1373 swp_entry_t swap = folio_swap_entry(folio);
1374
1375 if (reclaimed && !mapping_exiting(mapping))
1376 shadow = workingset_eviction(folio, target_memcg);
1377 __delete_from_swap_cache(folio, swap, shadow);
1378 mem_cgroup_swapout(folio, swap);
1379 xa_unlock_irq(&mapping->i_pages);
1380 put_swap_folio(folio, swap);
1381 } else {
1382 void (*free_folio)(struct folio *);
1383
1384 free_folio = mapping->a_ops->free_folio;
1385 /*
1386 * Remember a shadow entry for reclaimed file cache in
1387 * order to detect refaults, thus thrashing, later on.
1388 *
1389 * But don't store shadows in an address space that is
1390 * already exiting. This is not just an optimization,
1391 * inode reclaim needs to empty out the radix tree or
1392 * the nodes are lost. Don't plant shadows behind its
1393 * back.
1394 *
1395 * We also don't store shadows for DAX mappings because the
1396 * only page cache folios found in these are zero pages
1397 * covering holes, and because we don't want to mix DAX
1398 * exceptional entries and shadow exceptional entries in the
1399 * same address_space.
1400 */
1401 if (reclaimed && folio_is_file_lru(folio) &&
1402 !mapping_exiting(mapping) && !dax_mapping(mapping))
1403 shadow = workingset_eviction(folio, target_memcg);
1404 __filemap_remove_folio(folio, shadow);
1405 xa_unlock_irq(&mapping->i_pages);
1406 if (mapping_shrinkable(mapping))
1407 inode_add_lru(mapping->host);
1408 spin_unlock(&mapping->host->i_lock);
1409
1410 if (free_folio)
1411 free_folio(folio);
1412 }
1413
1414 return 1;
1415
1416cannot_free:
1417 xa_unlock_irq(&mapping->i_pages);
1418 if (!folio_test_swapcache(folio))
1419 spin_unlock(&mapping->host->i_lock);
1420 return 0;
1421}
1422
1423/**
1424 * remove_mapping() - Attempt to remove a folio from its mapping.
1425 * @mapping: The address space.
1426 * @folio: The folio to remove.
1427 *
1428 * If the folio is dirty, under writeback or if someone else has a ref
1429 * on it, removal will fail.
1430 * Return: The number of pages removed from the mapping. 0 if the folio
1431 * could not be removed.
1432 * Context: The caller should have a single refcount on the folio and
1433 * hold its lock.
1434 */
1435long remove_mapping(struct address_space *mapping, struct folio *folio)
1436{
1437 if (__remove_mapping(mapping, folio, false, NULL)) {
1438 /*
1439 * Unfreezing the refcount with 1 effectively
1440 * drops the pagecache ref for us without requiring another
1441 * atomic operation.
1442 */
1443 folio_ref_unfreeze(folio, 1);
1444 return folio_nr_pages(folio);
1445 }
1446 return 0;
1447}
1448
1449/**
1450 * folio_putback_lru - Put previously isolated folio onto appropriate LRU list.
1451 * @folio: Folio to be returned to an LRU list.
1452 *
1453 * Add previously isolated @folio to appropriate LRU list.
1454 * The folio may still be unevictable for other reasons.
1455 *
1456 * Context: lru_lock must not be held, interrupts must be enabled.
1457 */
1458void folio_putback_lru(struct folio *folio)
1459{
1460 folio_add_lru(folio);
1461 folio_put(folio); /* drop ref from isolate */
1462}
1463
1464enum folio_references {
1465 FOLIOREF_RECLAIM,
1466 FOLIOREF_RECLAIM_CLEAN,
1467 FOLIOREF_KEEP,
1468 FOLIOREF_ACTIVATE,
1469};
1470
1471static enum folio_references folio_check_references(struct folio *folio,
1472 struct scan_control *sc)
1473{
1474 int referenced_ptes, referenced_folio;
1475 unsigned long vm_flags;
1476
1477 referenced_ptes = folio_referenced(folio, 1, sc->target_mem_cgroup,
1478 &vm_flags);
1479 referenced_folio = folio_test_clear_referenced(folio);
1480
1481 /*
1482 * The supposedly reclaimable folio was found to be in a VM_LOCKED vma.
1483 * Let the folio, now marked Mlocked, be moved to the unevictable list.
1484 */
1485 if (vm_flags & VM_LOCKED)
1486 return FOLIOREF_ACTIVATE;
1487
1488 /* rmap lock contention: rotate */
1489 if (referenced_ptes == -1)
1490 return FOLIOREF_KEEP;
1491
1492 if (referenced_ptes) {
1493 /*
1494 * All mapped folios start out with page table
1495 * references from the instantiating fault, so we need
1496 * to look twice if a mapped file/anon folio is used more
1497 * than once.
1498 *
1499 * Mark it and spare it for another trip around the
1500 * inactive list. Another page table reference will
1501 * lead to its activation.
1502 *
1503 * Note: the mark is set for activated folios as well
1504 * so that recently deactivated but used folios are
1505 * quickly recovered.
1506 */
1507 folio_set_referenced(folio);
1508
1509 if (referenced_folio || referenced_ptes > 1)
1510 return FOLIOREF_ACTIVATE;
1511
1512 /*
1513 * Activate file-backed executable folios after first usage.
1514 */
1515 if ((vm_flags & VM_EXEC) && folio_is_file_lru(folio))
1516 return FOLIOREF_ACTIVATE;
1517
1518 return FOLIOREF_KEEP;
1519 }
1520
1521 /* Reclaim if clean, defer dirty folios to writeback */
1522 if (referenced_folio && folio_is_file_lru(folio))
1523 return FOLIOREF_RECLAIM_CLEAN;
1524
1525 return FOLIOREF_RECLAIM;
1526}
1527
1528/* Check if a folio is dirty or under writeback */
1529static void folio_check_dirty_writeback(struct folio *folio,
1530 bool *dirty, bool *writeback)
1531{
1532 struct address_space *mapping;
1533
1534 /*
1535 * Anonymous folios are not handled by flushers and must be written
1536 * from reclaim context. Do not stall reclaim based on them.
1537 * MADV_FREE anonymous folios are put into inactive file list too.
1538 * They could be mistakenly treated as file lru. So further anon
1539 * test is needed.
1540 */
1541 if (!folio_is_file_lru(folio) ||
1542 (folio_test_anon(folio) && !folio_test_swapbacked(folio))) {
1543 *dirty = false;
1544 *writeback = false;
1545 return;
1546 }
1547
1548 /* By default assume that the folio flags are accurate */
1549 *dirty = folio_test_dirty(folio);
1550 *writeback = folio_test_writeback(folio);
1551
1552 /* Verify dirty/writeback state if the filesystem supports it */
1553 if (!folio_test_private(folio))
1554 return;
1555
1556 mapping = folio_mapping(folio);
1557 if (mapping && mapping->a_ops->is_dirty_writeback)
1558 mapping->a_ops->is_dirty_writeback(folio, dirty, writeback);
1559}
1560
1561static struct page *alloc_demote_page(struct page *page, unsigned long private)
1562{
1563 struct page *target_page;
1564 nodemask_t *allowed_mask;
1565 struct migration_target_control *mtc;
1566
1567 mtc = (struct migration_target_control *)private;
1568
1569 allowed_mask = mtc->nmask;
1570 /*
1571 * make sure we allocate from the target node first also trying to
1572 * demote or reclaim pages from the target node via kswapd if we are
1573 * low on free memory on target node. If we don't do this and if
1574 * we have free memory on the slower(lower) memtier, we would start
1575 * allocating pages from slower(lower) memory tiers without even forcing
1576 * a demotion of cold pages from the target memtier. This can result
1577 * in the kernel placing hot pages in slower(lower) memory tiers.
1578 */
1579 mtc->nmask = NULL;
1580 mtc->gfp_mask |= __GFP_THISNODE;
1581 target_page = alloc_migration_target(page, (unsigned long)mtc);
1582 if (target_page)
1583 return target_page;
1584
1585 mtc->gfp_mask &= ~__GFP_THISNODE;
1586 mtc->nmask = allowed_mask;
1587
1588 return alloc_migration_target(page, (unsigned long)mtc);
1589}
1590
1591/*
1592 * Take folios on @demote_folios and attempt to demote them to another node.
1593 * Folios which are not demoted are left on @demote_folios.
1594 */
1595static unsigned int demote_folio_list(struct list_head *demote_folios,
1596 struct pglist_data *pgdat)
1597{
1598 int target_nid = next_demotion_node(pgdat->node_id);
1599 unsigned int nr_succeeded;
1600 nodemask_t allowed_mask;
1601
1602 struct migration_target_control mtc = {
1603 /*
1604 * Allocate from 'node', or fail quickly and quietly.
1605 * When this happens, 'page' will likely just be discarded
1606 * instead of migrated.
1607 */
1608 .gfp_mask = (GFP_HIGHUSER_MOVABLE & ~__GFP_RECLAIM) | __GFP_NOWARN |
1609 __GFP_NOMEMALLOC | GFP_NOWAIT,
1610 .nid = target_nid,
1611 .nmask = &allowed_mask
1612 };
1613
1614 if (list_empty(demote_folios))
1615 return 0;
1616
1617 if (target_nid == NUMA_NO_NODE)
1618 return 0;
1619
1620 node_get_allowed_targets(pgdat, &allowed_mask);
1621
1622 /* Demotion ignores all cpuset and mempolicy settings */
1623 migrate_pages(demote_folios, alloc_demote_page, NULL,
1624 (unsigned long)&mtc, MIGRATE_ASYNC, MR_DEMOTION,
1625 &nr_succeeded);
1626
1627 __count_vm_events(PGDEMOTE_KSWAPD + reclaimer_offset(), nr_succeeded);
1628
1629 return nr_succeeded;
1630}
1631
1632static bool may_enter_fs(struct folio *folio, gfp_t gfp_mask)
1633{
1634 if (gfp_mask & __GFP_FS)
1635 return true;
1636 if (!folio_test_swapcache(folio) || !(gfp_mask & __GFP_IO))
1637 return false;
1638 /*
1639 * We can "enter_fs" for swap-cache with only __GFP_IO
1640 * providing this isn't SWP_FS_OPS.
1641 * ->flags can be updated non-atomicially (scan_swap_map_slots),
1642 * but that will never affect SWP_FS_OPS, so the data_race
1643 * is safe.
1644 */
1645 return !data_race(folio_swap_flags(folio) & SWP_FS_OPS);
1646}
1647
1648/*
1649 * shrink_folio_list() returns the number of reclaimed pages
1650 */
1651static unsigned int shrink_folio_list(struct list_head *folio_list,
1652 struct pglist_data *pgdat, struct scan_control *sc,
1653 struct reclaim_stat *stat, bool ignore_references)
1654{
1655 LIST_HEAD(ret_folios);
1656 LIST_HEAD(free_folios);
1657 LIST_HEAD(demote_folios);
1658 unsigned int nr_reclaimed = 0;
1659 unsigned int pgactivate = 0;
1660 bool do_demote_pass;
1661 struct swap_iocb *plug = NULL;
1662
1663 memset(stat, 0, sizeof(*stat));
1664 cond_resched();
1665 do_demote_pass = can_demote(pgdat->node_id, sc);
1666
1667retry:
1668 while (!list_empty(folio_list)) {
1669 struct address_space *mapping;
1670 struct folio *folio;
1671 enum folio_references references = FOLIOREF_RECLAIM;
1672 bool dirty, writeback;
1673 unsigned int nr_pages;
1674
1675 cond_resched();
1676
1677 folio = lru_to_folio(folio_list);
1678 list_del(&folio->lru);
1679
1680 if (!folio_trylock(folio))
1681 goto keep;
1682
1683 VM_BUG_ON_FOLIO(folio_test_active(folio), folio);
1684
1685 nr_pages = folio_nr_pages(folio);
1686
1687 /* Account the number of base pages */
1688 sc->nr_scanned += nr_pages;
1689
1690 if (unlikely(!folio_evictable(folio)))
1691 goto activate_locked;
1692
1693 if (!sc->may_unmap && folio_mapped(folio))
1694 goto keep_locked;
1695
1696 /* folio_update_gen() tried to promote this page? */
1697 if (lru_gen_enabled() && !ignore_references &&
1698 folio_mapped(folio) && folio_test_referenced(folio))
1699 goto keep_locked;
1700
1701 /*
1702 * The number of dirty pages determines if a node is marked
1703 * reclaim_congested. kswapd will stall and start writing
1704 * folios if the tail of the LRU is all dirty unqueued folios.
1705 */
1706 folio_check_dirty_writeback(folio, &dirty, &writeback);
1707 if (dirty || writeback)
1708 stat->nr_dirty += nr_pages;
1709
1710 if (dirty && !writeback)
1711 stat->nr_unqueued_dirty += nr_pages;
1712
1713 /*
1714 * Treat this folio as congested if folios are cycling
1715 * through the LRU so quickly that the folios marked
1716 * for immediate reclaim are making it to the end of
1717 * the LRU a second time.
1718 */
1719 if (writeback && folio_test_reclaim(folio))
1720 stat->nr_congested += nr_pages;
1721
1722 /*
1723 * If a folio at the tail of the LRU is under writeback, there
1724 * are three cases to consider.
1725 *
1726 * 1) If reclaim is encountering an excessive number
1727 * of folios under writeback and this folio has both
1728 * the writeback and reclaim flags set, then it
1729 * indicates that folios are being queued for I/O but
1730 * are being recycled through the LRU before the I/O
1731 * can complete. Waiting on the folio itself risks an
1732 * indefinite stall if it is impossible to writeback
1733 * the folio due to I/O error or disconnected storage
1734 * so instead note that the LRU is being scanned too
1735 * quickly and the caller can stall after the folio
1736 * list has been processed.
1737 *
1738 * 2) Global or new memcg reclaim encounters a folio that is
1739 * not marked for immediate reclaim, or the caller does not
1740 * have __GFP_FS (or __GFP_IO if it's simply going to swap,
1741 * not to fs). In this case mark the folio for immediate
1742 * reclaim and continue scanning.
1743 *
1744 * Require may_enter_fs() because we would wait on fs, which
1745 * may not have submitted I/O yet. And the loop driver might
1746 * enter reclaim, and deadlock if it waits on a folio for
1747 * which it is needed to do the write (loop masks off
1748 * __GFP_IO|__GFP_FS for this reason); but more thought
1749 * would probably show more reasons.
1750 *
1751 * 3) Legacy memcg encounters a folio that already has the
1752 * reclaim flag set. memcg does not have any dirty folio
1753 * throttling so we could easily OOM just because too many
1754 * folios are in writeback and there is nothing else to
1755 * reclaim. Wait for the writeback to complete.
1756 *
1757 * In cases 1) and 2) we activate the folios to get them out of
1758 * the way while we continue scanning for clean folios on the
1759 * inactive list and refilling from the active list. The
1760 * observation here is that waiting for disk writes is more
1761 * expensive than potentially causing reloads down the line.
1762 * Since they're marked for immediate reclaim, they won't put
1763 * memory pressure on the cache working set any longer than it
1764 * takes to write them to disk.
1765 */
1766 if (folio_test_writeback(folio)) {
1767 /* Case 1 above */
1768 if (current_is_kswapd() &&
1769 folio_test_reclaim(folio) &&
1770 test_bit(PGDAT_WRITEBACK, &pgdat->flags)) {
1771 stat->nr_immediate += nr_pages;
1772 goto activate_locked;
1773
1774 /* Case 2 above */
1775 } else if (writeback_throttling_sane(sc) ||
1776 !folio_test_reclaim(folio) ||
1777 !may_enter_fs(folio, sc->gfp_mask)) {
1778 /*
1779 * This is slightly racy -
1780 * folio_end_writeback() might have
1781 * just cleared the reclaim flag, then
1782 * setting the reclaim flag here ends up
1783 * interpreted as the readahead flag - but
1784 * that does not matter enough to care.
1785 * What we do want is for this folio to
1786 * have the reclaim flag set next time
1787 * memcg reclaim reaches the tests above,
1788 * so it will then wait for writeback to
1789 * avoid OOM; and it's also appropriate
1790 * in global reclaim.
1791 */
1792 folio_set_reclaim(folio);
1793 stat->nr_writeback += nr_pages;
1794 goto activate_locked;
1795
1796 /* Case 3 above */
1797 } else {
1798 folio_unlock(folio);
1799 folio_wait_writeback(folio);
1800 /* then go back and try same folio again */
1801 list_add_tail(&folio->lru, folio_list);
1802 continue;
1803 }
1804 }
1805
1806 if (!ignore_references)
1807 references = folio_check_references(folio, sc);
1808
1809 switch (references) {
1810 case FOLIOREF_ACTIVATE:
1811 goto activate_locked;
1812 case FOLIOREF_KEEP:
1813 stat->nr_ref_keep += nr_pages;
1814 goto keep_locked;
1815 case FOLIOREF_RECLAIM:
1816 case FOLIOREF_RECLAIM_CLEAN:
1817 ; /* try to reclaim the folio below */
1818 }
1819
1820 /*
1821 * Before reclaiming the folio, try to relocate
1822 * its contents to another node.
1823 */
1824 if (do_demote_pass &&
1825 (thp_migration_supported() || !folio_test_large(folio))) {
1826 list_add(&folio->lru, &demote_folios);
1827 folio_unlock(folio);
1828 continue;
1829 }
1830
1831 /*
1832 * Anonymous process memory has backing store?
1833 * Try to allocate it some swap space here.
1834 * Lazyfree folio could be freed directly
1835 */
1836 if (folio_test_anon(folio) && folio_test_swapbacked(folio)) {
1837 if (!folio_test_swapcache(folio)) {
1838 if (!(sc->gfp_mask & __GFP_IO))
1839 goto keep_locked;
1840 if (folio_maybe_dma_pinned(folio))
1841 goto keep_locked;
1842 if (folio_test_large(folio)) {
1843 /* cannot split folio, skip it */
1844 if (!can_split_folio(folio, NULL))
1845 goto activate_locked;
1846 /*
1847 * Split folios without a PMD map right
1848 * away. Chances are some or all of the
1849 * tail pages can be freed without IO.
1850 */
1851 if (!folio_entire_mapcount(folio) &&
1852 split_folio_to_list(folio,
1853 folio_list))
1854 goto activate_locked;
1855 }
1856 if (!add_to_swap(folio)) {
1857 if (!folio_test_large(folio))
1858 goto activate_locked_split;
1859 /* Fallback to swap normal pages */
1860 if (split_folio_to_list(folio,
1861 folio_list))
1862 goto activate_locked;
1863#ifdef CONFIG_TRANSPARENT_HUGEPAGE
1864 count_vm_event(THP_SWPOUT_FALLBACK);
1865#endif
1866 if (!add_to_swap(folio))
1867 goto activate_locked_split;
1868 }
1869 }
1870 } else if (folio_test_swapbacked(folio) &&
1871 folio_test_large(folio)) {
1872 /* Split shmem folio */
1873 if (split_folio_to_list(folio, folio_list))
1874 goto keep_locked;
1875 }
1876
1877 /*
1878 * If the folio was split above, the tail pages will make
1879 * their own pass through this function and be accounted
1880 * then.
1881 */
1882 if ((nr_pages > 1) && !folio_test_large(folio)) {
1883 sc->nr_scanned -= (nr_pages - 1);
1884 nr_pages = 1;
1885 }
1886
1887 /*
1888 * The folio is mapped into the page tables of one or more
1889 * processes. Try to unmap it here.
1890 */
1891 if (folio_mapped(folio)) {
1892 enum ttu_flags flags = TTU_BATCH_FLUSH;
1893 bool was_swapbacked = folio_test_swapbacked(folio);
1894
1895 if (folio_test_pmd_mappable(folio))
1896 flags |= TTU_SPLIT_HUGE_PMD;
1897
1898 try_to_unmap(folio, flags);
1899 if (folio_mapped(folio)) {
1900 stat->nr_unmap_fail += nr_pages;
1901 if (!was_swapbacked &&
1902 folio_test_swapbacked(folio))
1903 stat->nr_lazyfree_fail += nr_pages;
1904 goto activate_locked;
1905 }
1906 }
1907
1908 mapping = folio_mapping(folio);
1909 if (folio_test_dirty(folio)) {
1910 /*
1911 * Only kswapd can writeback filesystem folios
1912 * to avoid risk of stack overflow. But avoid
1913 * injecting inefficient single-folio I/O into
1914 * flusher writeback as much as possible: only
1915 * write folios when we've encountered many
1916 * dirty folios, and when we've already scanned
1917 * the rest of the LRU for clean folios and see
1918 * the same dirty folios again (with the reclaim
1919 * flag set).
1920 */
1921 if (folio_is_file_lru(folio) &&
1922 (!current_is_kswapd() ||
1923 !folio_test_reclaim(folio) ||
1924 !test_bit(PGDAT_DIRTY, &pgdat->flags))) {
1925 /*
1926 * Immediately reclaim when written back.
1927 * Similar in principle to deactivate_page()
1928 * except we already have the folio isolated
1929 * and know it's dirty
1930 */
1931 node_stat_mod_folio(folio, NR_VMSCAN_IMMEDIATE,
1932 nr_pages);
1933 folio_set_reclaim(folio);
1934
1935 goto activate_locked;
1936 }
1937
1938 if (references == FOLIOREF_RECLAIM_CLEAN)
1939 goto keep_locked;
1940 if (!may_enter_fs(folio, sc->gfp_mask))
1941 goto keep_locked;
1942 if (!sc->may_writepage)
1943 goto keep_locked;
1944
1945 /*
1946 * Folio is dirty. Flush the TLB if a writable entry
1947 * potentially exists to avoid CPU writes after I/O
1948 * starts and then write it out here.
1949 */
1950 try_to_unmap_flush_dirty();
1951 switch (pageout(folio, mapping, &plug)) {
1952 case PAGE_KEEP:
1953 goto keep_locked;
1954 case PAGE_ACTIVATE:
1955 goto activate_locked;
1956 case PAGE_SUCCESS:
1957 stat->nr_pageout += nr_pages;
1958
1959 if (folio_test_writeback(folio))
1960 goto keep;
1961 if (folio_test_dirty(folio))
1962 goto keep;
1963
1964 /*
1965 * A synchronous write - probably a ramdisk. Go
1966 * ahead and try to reclaim the folio.
1967 */
1968 if (!folio_trylock(folio))
1969 goto keep;
1970 if (folio_test_dirty(folio) ||
1971 folio_test_writeback(folio))
1972 goto keep_locked;
1973 mapping = folio_mapping(folio);
1974 fallthrough;
1975 case PAGE_CLEAN:
1976 ; /* try to free the folio below */
1977 }
1978 }
1979
1980 /*
1981 * If the folio has buffers, try to free the buffer
1982 * mappings associated with this folio. If we succeed
1983 * we try to free the folio as well.
1984 *
1985 * We do this even if the folio is dirty.
1986 * filemap_release_folio() does not perform I/O, but it
1987 * is possible for a folio to have the dirty flag set,
1988 * but it is actually clean (all its buffers are clean).
1989 * This happens if the buffers were written out directly,
1990 * with submit_bh(). ext3 will do this, as well as
1991 * the blockdev mapping. filemap_release_folio() will
1992 * discover that cleanness and will drop the buffers
1993 * and mark the folio clean - it can be freed.
1994 *
1995 * Rarely, folios can have buffers and no ->mapping.
1996 * These are the folios which were not successfully
1997 * invalidated in truncate_cleanup_folio(). We try to
1998 * drop those buffers here and if that worked, and the
1999 * folio is no longer mapped into process address space
2000 * (refcount == 1) it can be freed. Otherwise, leave
2001 * the folio on the LRU so it is swappable.
2002 */
2003 if (folio_has_private(folio)) {
2004 if (!filemap_release_folio(folio, sc->gfp_mask))
2005 goto activate_locked;
2006 if (!mapping && folio_ref_count(folio) == 1) {
2007 folio_unlock(folio);
2008 if (folio_put_testzero(folio))
2009 goto free_it;
2010 else {
2011 /*
2012 * rare race with speculative reference.
2013 * the speculative reference will free
2014 * this folio shortly, so we may
2015 * increment nr_reclaimed here (and
2016 * leave it off the LRU).
2017 */
2018 nr_reclaimed += nr_pages;
2019 continue;
2020 }
2021 }
2022 }
2023
2024 if (folio_test_anon(folio) && !folio_test_swapbacked(folio)) {
2025 /* follow __remove_mapping for reference */
2026 if (!folio_ref_freeze(folio, 1))
2027 goto keep_locked;
2028 /*
2029 * The folio has only one reference left, which is
2030 * from the isolation. After the caller puts the
2031 * folio back on the lru and drops the reference, the
2032 * folio will be freed anyway. It doesn't matter
2033 * which lru it goes on. So we don't bother checking
2034 * the dirty flag here.
2035 */
2036 count_vm_events(PGLAZYFREED, nr_pages);
2037 count_memcg_folio_events(folio, PGLAZYFREED, nr_pages);
2038 } else if (!mapping || !__remove_mapping(mapping, folio, true,
2039 sc->target_mem_cgroup))
2040 goto keep_locked;
2041
2042 folio_unlock(folio);
2043free_it:
2044 /*
2045 * Folio may get swapped out as a whole, need to account
2046 * all pages in it.
2047 */
2048 nr_reclaimed += nr_pages;
2049
2050 /*
2051 * Is there need to periodically free_folio_list? It would
2052 * appear not as the counts should be low
2053 */
2054 if (unlikely(folio_test_large(folio)))
2055 destroy_large_folio(folio);
2056 else
2057 list_add(&folio->lru, &free_folios);
2058 continue;
2059
2060activate_locked_split:
2061 /*
2062 * The tail pages that are failed to add into swap cache
2063 * reach here. Fixup nr_scanned and nr_pages.
2064 */
2065 if (nr_pages > 1) {
2066 sc->nr_scanned -= (nr_pages - 1);
2067 nr_pages = 1;
2068 }
2069activate_locked:
2070 /* Not a candidate for swapping, so reclaim swap space. */
2071 if (folio_test_swapcache(folio) &&
2072 (mem_cgroup_swap_full(folio) || folio_test_mlocked(folio)))
2073 folio_free_swap(folio);
2074 VM_BUG_ON_FOLIO(folio_test_active(folio), folio);
2075 if (!folio_test_mlocked(folio)) {
2076 int type = folio_is_file_lru(folio);
2077 folio_set_active(folio);
2078 stat->nr_activate[type] += nr_pages;
2079 count_memcg_folio_events(folio, PGACTIVATE, nr_pages);
2080 }
2081keep_locked:
2082 folio_unlock(folio);
2083keep:
2084 list_add(&folio->lru, &ret_folios);
2085 VM_BUG_ON_FOLIO(folio_test_lru(folio) ||
2086 folio_test_unevictable(folio), folio);
2087 }
2088 /* 'folio_list' is always empty here */
2089
2090 /* Migrate folios selected for demotion */
2091 nr_reclaimed += demote_folio_list(&demote_folios, pgdat);
2092 /* Folios that could not be demoted are still in @demote_folios */
2093 if (!list_empty(&demote_folios)) {
2094 /* Folios which weren't demoted go back on @folio_list */
2095 list_splice_init(&demote_folios, folio_list);
2096
2097 /*
2098 * goto retry to reclaim the undemoted folios in folio_list if
2099 * desired.
2100 *
2101 * Reclaiming directly from top tier nodes is not often desired
2102 * due to it breaking the LRU ordering: in general memory
2103 * should be reclaimed from lower tier nodes and demoted from
2104 * top tier nodes.
2105 *
2106 * However, disabling reclaim from top tier nodes entirely
2107 * would cause ooms in edge scenarios where lower tier memory
2108 * is unreclaimable for whatever reason, eg memory being
2109 * mlocked or too hot to reclaim. We can disable reclaim
2110 * from top tier nodes in proactive reclaim though as that is
2111 * not real memory pressure.
2112 */
2113 if (!sc->proactive) {
2114 do_demote_pass = false;
2115 goto retry;
2116 }
2117 }
2118
2119 pgactivate = stat->nr_activate[0] + stat->nr_activate[1];
2120
2121 mem_cgroup_uncharge_list(&free_folios);
2122 try_to_unmap_flush();
2123 free_unref_page_list(&free_folios);
2124
2125 list_splice(&ret_folios, folio_list);
2126 count_vm_events(PGACTIVATE, pgactivate);
2127
2128 if (plug)
2129 swap_write_unplug(plug);
2130 return nr_reclaimed;
2131}
2132
2133unsigned int reclaim_clean_pages_from_list(struct zone *zone,
2134 struct list_head *folio_list)
2135{
2136 struct scan_control sc = {
2137 .gfp_mask = GFP_KERNEL,
2138 .may_unmap = 1,
2139 };
2140 struct reclaim_stat stat;
2141 unsigned int nr_reclaimed;
2142 struct folio *folio, *next;
2143 LIST_HEAD(clean_folios);
2144 unsigned int noreclaim_flag;
2145
2146 list_for_each_entry_safe(folio, next, folio_list, lru) {
2147 if (!folio_test_hugetlb(folio) && folio_is_file_lru(folio) &&
2148 !folio_test_dirty(folio) && !__folio_test_movable(folio) &&
2149 !folio_test_unevictable(folio)) {
2150 folio_clear_active(folio);
2151 list_move(&folio->lru, &clean_folios);
2152 }
2153 }
2154
2155 /*
2156 * We should be safe here since we are only dealing with file pages and
2157 * we are not kswapd and therefore cannot write dirty file pages. But
2158 * call memalloc_noreclaim_save() anyway, just in case these conditions
2159 * change in the future.
2160 */
2161 noreclaim_flag = memalloc_noreclaim_save();
2162 nr_reclaimed = shrink_folio_list(&clean_folios, zone->zone_pgdat, &sc,
2163 &stat, true);
2164 memalloc_noreclaim_restore(noreclaim_flag);
2165
2166 list_splice(&clean_folios, folio_list);
2167 mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE,
2168 -(long)nr_reclaimed);
2169 /*
2170 * Since lazyfree pages are isolated from file LRU from the beginning,
2171 * they will rotate back to anonymous LRU in the end if it failed to
2172 * discard so isolated count will be mismatched.
2173 * Compensate the isolated count for both LRU lists.
2174 */
2175 mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_ANON,
2176 stat.nr_lazyfree_fail);
2177 mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE,
2178 -(long)stat.nr_lazyfree_fail);
2179 return nr_reclaimed;
2180}
2181
2182/*
2183 * Update LRU sizes after isolating pages. The LRU size updates must
2184 * be complete before mem_cgroup_update_lru_size due to a sanity check.
2185 */
2186static __always_inline void update_lru_sizes(struct lruvec *lruvec,
2187 enum lru_list lru, unsigned long *nr_zone_taken)
2188{
2189 int zid;
2190
2191 for (zid = 0; zid < MAX_NR_ZONES; zid++) {
2192 if (!nr_zone_taken[zid])
2193 continue;
2194
2195 update_lru_size(lruvec, lru, zid, -nr_zone_taken[zid]);
2196 }
2197
2198}
2199
2200/*
2201 * Isolating page from the lruvec to fill in @dst list by nr_to_scan times.
2202 *
2203 * lruvec->lru_lock is heavily contended. Some of the functions that
2204 * shrink the lists perform better by taking out a batch of pages
2205 * and working on them outside the LRU lock.
2206 *
2207 * For pagecache intensive workloads, this function is the hottest
2208 * spot in the kernel (apart from copy_*_user functions).
2209 *
2210 * Lru_lock must be held before calling this function.
2211 *
2212 * @nr_to_scan: The number of eligible pages to look through on the list.
2213 * @lruvec: The LRU vector to pull pages from.
2214 * @dst: The temp list to put pages on to.
2215 * @nr_scanned: The number of pages that were scanned.
2216 * @sc: The scan_control struct for this reclaim session
2217 * @lru: LRU list id for isolating
2218 *
2219 * returns how many pages were moved onto *@dst.
2220 */
2221static unsigned long isolate_lru_folios(unsigned long nr_to_scan,
2222 struct lruvec *lruvec, struct list_head *dst,
2223 unsigned long *nr_scanned, struct scan_control *sc,
2224 enum lru_list lru)
2225{
2226 struct list_head *src = &lruvec->lists[lru];
2227 unsigned long nr_taken = 0;
2228 unsigned long nr_zone_taken[MAX_NR_ZONES] = { 0 };
2229 unsigned long nr_skipped[MAX_NR_ZONES] = { 0, };
2230 unsigned long skipped = 0;
2231 unsigned long scan, total_scan, nr_pages;
2232 LIST_HEAD(folios_skipped);
2233
2234 total_scan = 0;
2235 scan = 0;
2236 while (scan < nr_to_scan && !list_empty(src)) {
2237 struct list_head *move_to = src;
2238 struct folio *folio;
2239
2240 folio = lru_to_folio(src);
2241 prefetchw_prev_lru_folio(folio, src, flags);
2242
2243 nr_pages = folio_nr_pages(folio);
2244 total_scan += nr_pages;
2245
2246 if (folio_zonenum(folio) > sc->reclaim_idx) {
2247 nr_skipped[folio_zonenum(folio)] += nr_pages;
2248 move_to = &folios_skipped;
2249 goto move;
2250 }
2251
2252 /*
2253 * Do not count skipped folios because that makes the function
2254 * return with no isolated folios if the LRU mostly contains
2255 * ineligible folios. This causes the VM to not reclaim any
2256 * folios, triggering a premature OOM.
2257 * Account all pages in a folio.
2258 */
2259 scan += nr_pages;
2260
2261 if (!folio_test_lru(folio))
2262 goto move;
2263 if (!sc->may_unmap && folio_mapped(folio))
2264 goto move;
2265
2266 /*
2267 * Be careful not to clear the lru flag until after we're
2268 * sure the folio is not being freed elsewhere -- the
2269 * folio release code relies on it.
2270 */
2271 if (unlikely(!folio_try_get(folio)))
2272 goto move;
2273
2274 if (!folio_test_clear_lru(folio)) {
2275 /* Another thread is already isolating this folio */
2276 folio_put(folio);
2277 goto move;
2278 }
2279
2280 nr_taken += nr_pages;
2281 nr_zone_taken[folio_zonenum(folio)] += nr_pages;
2282 move_to = dst;
2283move:
2284 list_move(&folio->lru, move_to);
2285 }
2286
2287 /*
2288 * Splice any skipped folios to the start of the LRU list. Note that
2289 * this disrupts the LRU order when reclaiming for lower zones but
2290 * we cannot splice to the tail. If we did then the SWAP_CLUSTER_MAX
2291 * scanning would soon rescan the same folios to skip and waste lots
2292 * of cpu cycles.
2293 */
2294 if (!list_empty(&folios_skipped)) {
2295 int zid;
2296
2297 list_splice(&folios_skipped, src);
2298 for (zid = 0; zid < MAX_NR_ZONES; zid++) {
2299 if (!nr_skipped[zid])
2300 continue;
2301
2302 __count_zid_vm_events(PGSCAN_SKIP, zid, nr_skipped[zid]);
2303 skipped += nr_skipped[zid];
2304 }
2305 }
2306 *nr_scanned = total_scan;
2307 trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, nr_to_scan,
2308 total_scan, skipped, nr_taken,
2309 sc->may_unmap ? 0 : ISOLATE_UNMAPPED, lru);
2310 update_lru_sizes(lruvec, lru, nr_zone_taken);
2311 return nr_taken;
2312}
2313
2314/**
2315 * folio_isolate_lru() - Try to isolate a folio from its LRU list.
2316 * @folio: Folio to isolate from its LRU list.
2317 *
2318 * Isolate a @folio from an LRU list and adjust the vmstat statistic
2319 * corresponding to whatever LRU list the folio was on.
2320 *
2321 * The folio will have its LRU flag cleared. If it was found on the
2322 * active list, it will have the Active flag set. If it was found on the
2323 * unevictable list, it will have the Unevictable flag set. These flags
2324 * may need to be cleared by the caller before letting the page go.
2325 *
2326 * Context:
2327 *
2328 * (1) Must be called with an elevated refcount on the folio. This is a
2329 * fundamental difference from isolate_lru_folios() (which is called
2330 * without a stable reference).
2331 * (2) The lru_lock must not be held.
2332 * (3) Interrupts must be enabled.
2333 *
2334 * Return: 0 if the folio was removed from an LRU list.
2335 * -EBUSY if the folio was not on an LRU list.
2336 */
2337int folio_isolate_lru(struct folio *folio)
2338{
2339 int ret = -EBUSY;
2340
2341 VM_BUG_ON_FOLIO(!folio_ref_count(folio), folio);
2342
2343 if (folio_test_clear_lru(folio)) {
2344 struct lruvec *lruvec;
2345
2346 folio_get(folio);
2347 lruvec = folio_lruvec_lock_irq(folio);
2348 lruvec_del_folio(lruvec, folio);
2349 unlock_page_lruvec_irq(lruvec);
2350 ret = 0;
2351 }
2352
2353 return ret;
2354}
2355
2356/*
2357 * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and
2358 * then get rescheduled. When there are massive number of tasks doing page
2359 * allocation, such sleeping direct reclaimers may keep piling up on each CPU,
2360 * the LRU list will go small and be scanned faster than necessary, leading to
2361 * unnecessary swapping, thrashing and OOM.
2362 */
2363static int too_many_isolated(struct pglist_data *pgdat, int file,
2364 struct scan_control *sc)
2365{
2366 unsigned long inactive, isolated;
2367 bool too_many;
2368
2369 if (current_is_kswapd())
2370 return 0;
2371
2372 if (!writeback_throttling_sane(sc))
2373 return 0;
2374
2375 if (file) {
2376 inactive = node_page_state(pgdat, NR_INACTIVE_FILE);
2377 isolated = node_page_state(pgdat, NR_ISOLATED_FILE);
2378 } else {
2379 inactive = node_page_state(pgdat, NR_INACTIVE_ANON);
2380 isolated = node_page_state(pgdat, NR_ISOLATED_ANON);
2381 }
2382
2383 /*
2384 * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they
2385 * won't get blocked by normal direct-reclaimers, forming a circular
2386 * deadlock.
2387 */
2388 if ((sc->gfp_mask & (__GFP_IO | __GFP_FS)) == (__GFP_IO | __GFP_FS))
2389 inactive >>= 3;
2390
2391 too_many = isolated > inactive;
2392
2393 /* Wake up tasks throttled due to too_many_isolated. */
2394 if (!too_many)
2395 wake_throttle_isolated(pgdat);
2396
2397 return too_many;
2398}
2399
2400/*
2401 * move_folios_to_lru() moves folios from private @list to appropriate LRU list.
2402 * On return, @list is reused as a list of folios to be freed by the caller.
2403 *
2404 * Returns the number of pages moved to the given lruvec.
2405 */
2406static unsigned int move_folios_to_lru(struct lruvec *lruvec,
2407 struct list_head *list)
2408{
2409 int nr_pages, nr_moved = 0;
2410 LIST_HEAD(folios_to_free);
2411
2412 while (!list_empty(list)) {
2413 struct folio *folio = lru_to_folio(list);
2414
2415 VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
2416 list_del(&folio->lru);
2417 if (unlikely(!folio_evictable(folio))) {
2418 spin_unlock_irq(&lruvec->lru_lock);
2419 folio_putback_lru(folio);
2420 spin_lock_irq(&lruvec->lru_lock);
2421 continue;
2422 }
2423
2424 /*
2425 * The folio_set_lru needs to be kept here for list integrity.
2426 * Otherwise:
2427 * #0 move_folios_to_lru #1 release_pages
2428 * if (!folio_put_testzero())
2429 * if (folio_put_testzero())
2430 * !lru //skip lru_lock
2431 * folio_set_lru()
2432 * list_add(&folio->lru,)
2433 * list_add(&folio->lru,)
2434 */
2435 folio_set_lru(folio);
2436
2437 if (unlikely(folio_put_testzero(folio))) {
2438 __folio_clear_lru_flags(folio);
2439
2440 if (unlikely(folio_test_large(folio))) {
2441 spin_unlock_irq(&lruvec->lru_lock);
2442 destroy_large_folio(folio);
2443 spin_lock_irq(&lruvec->lru_lock);
2444 } else
2445 list_add(&folio->lru, &folios_to_free);
2446
2447 continue;
2448 }
2449
2450 /*
2451 * All pages were isolated from the same lruvec (and isolation
2452 * inhibits memcg migration).
2453 */
2454 VM_BUG_ON_FOLIO(!folio_matches_lruvec(folio, lruvec), folio);
2455 lruvec_add_folio(lruvec, folio);
2456 nr_pages = folio_nr_pages(folio);
2457 nr_moved += nr_pages;
2458 if (folio_test_active(folio))
2459 workingset_age_nonresident(lruvec, nr_pages);
2460 }
2461
2462 /*
2463 * To save our caller's stack, now use input list for pages to free.
2464 */
2465 list_splice(&folios_to_free, list);
2466
2467 return nr_moved;
2468}
2469
2470/*
2471 * If a kernel thread (such as nfsd for loop-back mounts) services a backing
2472 * device by writing to the page cache it sets PF_LOCAL_THROTTLE. In this case
2473 * we should not throttle. Otherwise it is safe to do so.
2474 */
2475static int current_may_throttle(void)
2476{
2477 return !(current->flags & PF_LOCAL_THROTTLE);
2478}
2479
2480/*
2481 * shrink_inactive_list() is a helper for shrink_node(). It returns the number
2482 * of reclaimed pages
2483 */
2484static unsigned long shrink_inactive_list(unsigned long nr_to_scan,
2485 struct lruvec *lruvec, struct scan_control *sc,
2486 enum lru_list lru)
2487{
2488 LIST_HEAD(folio_list);
2489 unsigned long nr_scanned;
2490 unsigned int nr_reclaimed = 0;
2491 unsigned long nr_taken;
2492 struct reclaim_stat stat;
2493 bool file = is_file_lru(lru);
2494 enum vm_event_item item;
2495 struct pglist_data *pgdat = lruvec_pgdat(lruvec);
2496 bool stalled = false;
2497
2498 while (unlikely(too_many_isolated(pgdat, file, sc))) {
2499 if (stalled)
2500 return 0;
2501
2502 /* wait a bit for the reclaimer. */
2503 stalled = true;
2504 reclaim_throttle(pgdat, VMSCAN_THROTTLE_ISOLATED);
2505
2506 /* We are about to die and free our memory. Return now. */
2507 if (fatal_signal_pending(current))
2508 return SWAP_CLUSTER_MAX;
2509 }
2510
2511 lru_add_drain();
2512
2513 spin_lock_irq(&lruvec->lru_lock);
2514
2515 nr_taken = isolate_lru_folios(nr_to_scan, lruvec, &folio_list,
2516 &nr_scanned, sc, lru);
2517
2518 __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken);
2519 item = PGSCAN_KSWAPD + reclaimer_offset();
2520 if (!cgroup_reclaim(sc))
2521 __count_vm_events(item, nr_scanned);
2522 __count_memcg_events(lruvec_memcg(lruvec), item, nr_scanned);
2523 __count_vm_events(PGSCAN_ANON + file, nr_scanned);
2524
2525 spin_unlock_irq(&lruvec->lru_lock);
2526
2527 if (nr_taken == 0)
2528 return 0;
2529
2530 nr_reclaimed = shrink_folio_list(&folio_list, pgdat, sc, &stat, false);
2531
2532 spin_lock_irq(&lruvec->lru_lock);
2533 move_folios_to_lru(lruvec, &folio_list);
2534
2535 __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
2536 item = PGSTEAL_KSWAPD + reclaimer_offset();
2537 if (!cgroup_reclaim(sc))
2538 __count_vm_events(item, nr_reclaimed);
2539 __count_memcg_events(lruvec_memcg(lruvec), item, nr_reclaimed);
2540 __count_vm_events(PGSTEAL_ANON + file, nr_reclaimed);
2541 spin_unlock_irq(&lruvec->lru_lock);
2542
2543 lru_note_cost(lruvec, file, stat.nr_pageout, nr_scanned - nr_reclaimed);
2544 mem_cgroup_uncharge_list(&folio_list);
2545 free_unref_page_list(&folio_list);
2546
2547 /*
2548 * If dirty folios are scanned that are not queued for IO, it
2549 * implies that flushers are not doing their job. This can
2550 * happen when memory pressure pushes dirty folios to the end of
2551 * the LRU before the dirty limits are breached and the dirty
2552 * data has expired. It can also happen when the proportion of
2553 * dirty folios grows not through writes but through memory
2554 * pressure reclaiming all the clean cache. And in some cases,
2555 * the flushers simply cannot keep up with the allocation
2556 * rate. Nudge the flusher threads in case they are asleep.
2557 */
2558 if (stat.nr_unqueued_dirty == nr_taken) {
2559 wakeup_flusher_threads(WB_REASON_VMSCAN);
2560 /*
2561 * For cgroupv1 dirty throttling is achieved by waking up
2562 * the kernel flusher here and later waiting on folios
2563 * which are in writeback to finish (see shrink_folio_list()).
2564 *
2565 * Flusher may not be able to issue writeback quickly
2566 * enough for cgroupv1 writeback throttling to work
2567 * on a large system.
2568 */
2569 if (!writeback_throttling_sane(sc))
2570 reclaim_throttle(pgdat, VMSCAN_THROTTLE_WRITEBACK);
2571 }
2572
2573 sc->nr.dirty += stat.nr_dirty;
2574 sc->nr.congested += stat.nr_congested;
2575 sc->nr.unqueued_dirty += stat.nr_unqueued_dirty;
2576 sc->nr.writeback += stat.nr_writeback;
2577 sc->nr.immediate += stat.nr_immediate;
2578 sc->nr.taken += nr_taken;
2579 if (file)
2580 sc->nr.file_taken += nr_taken;
2581
2582 trace_mm_vmscan_lru_shrink_inactive(pgdat->node_id,
2583 nr_scanned, nr_reclaimed, &stat, sc->priority, file);
2584 return nr_reclaimed;
2585}
2586
2587/*
2588 * shrink_active_list() moves folios from the active LRU to the inactive LRU.
2589 *
2590 * We move them the other way if the folio is referenced by one or more
2591 * processes.
2592 *
2593 * If the folios are mostly unmapped, the processing is fast and it is
2594 * appropriate to hold lru_lock across the whole operation. But if
2595 * the folios are mapped, the processing is slow (folio_referenced()), so
2596 * we should drop lru_lock around each folio. It's impossible to balance
2597 * this, so instead we remove the folios from the LRU while processing them.
2598 * It is safe to rely on the active flag against the non-LRU folios in here
2599 * because nobody will play with that bit on a non-LRU folio.
2600 *
2601 * The downside is that we have to touch folio->_refcount against each folio.
2602 * But we had to alter folio->flags anyway.
2603 */
2604static void shrink_active_list(unsigned long nr_to_scan,
2605 struct lruvec *lruvec,
2606 struct scan_control *sc,
2607 enum lru_list lru)
2608{
2609 unsigned long nr_taken;
2610 unsigned long nr_scanned;
2611 unsigned long vm_flags;
2612 LIST_HEAD(l_hold); /* The folios which were snipped off */
2613 LIST_HEAD(l_active);
2614 LIST_HEAD(l_inactive);
2615 unsigned nr_deactivate, nr_activate;
2616 unsigned nr_rotated = 0;
2617 int file = is_file_lru(lru);
2618 struct pglist_data *pgdat = lruvec_pgdat(lruvec);
2619
2620 lru_add_drain();
2621
2622 spin_lock_irq(&lruvec->lru_lock);
2623
2624 nr_taken = isolate_lru_folios(nr_to_scan, lruvec, &l_hold,
2625 &nr_scanned, sc, lru);
2626
2627 __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken);
2628
2629 if (!cgroup_reclaim(sc))
2630 __count_vm_events(PGREFILL, nr_scanned);
2631 __count_memcg_events(lruvec_memcg(lruvec), PGREFILL, nr_scanned);
2632
2633 spin_unlock_irq(&lruvec->lru_lock);
2634
2635 while (!list_empty(&l_hold)) {
2636 struct folio *folio;
2637
2638 cond_resched();
2639 folio = lru_to_folio(&l_hold);
2640 list_del(&folio->lru);
2641
2642 if (unlikely(!folio_evictable(folio))) {
2643 folio_putback_lru(folio);
2644 continue;
2645 }
2646
2647 if (unlikely(buffer_heads_over_limit)) {
2648 if (folio_test_private(folio) && folio_trylock(folio)) {
2649 if (folio_test_private(folio))
2650 filemap_release_folio(folio, 0);
2651 folio_unlock(folio);
2652 }
2653 }
2654
2655 /* Referenced or rmap lock contention: rotate */
2656 if (folio_referenced(folio, 0, sc->target_mem_cgroup,
2657 &vm_flags) != 0) {
2658 /*
2659 * Identify referenced, file-backed active folios and
2660 * give them one more trip around the active list. So
2661 * that executable code get better chances to stay in
2662 * memory under moderate memory pressure. Anon folios
2663 * are not likely to be evicted by use-once streaming
2664 * IO, plus JVM can create lots of anon VM_EXEC folios,
2665 * so we ignore them here.
2666 */
2667 if ((vm_flags & VM_EXEC) && folio_is_file_lru(folio)) {
2668 nr_rotated += folio_nr_pages(folio);
2669 list_add(&folio->lru, &l_active);
2670 continue;
2671 }
2672 }
2673
2674 folio_clear_active(folio); /* we are de-activating */
2675 folio_set_workingset(folio);
2676 list_add(&folio->lru, &l_inactive);
2677 }
2678
2679 /*
2680 * Move folios back to the lru list.
2681 */
2682 spin_lock_irq(&lruvec->lru_lock);
2683
2684 nr_activate = move_folios_to_lru(lruvec, &l_active);
2685 nr_deactivate = move_folios_to_lru(lruvec, &l_inactive);
2686 /* Keep all free folios in l_active list */
2687 list_splice(&l_inactive, &l_active);
2688
2689 __count_vm_events(PGDEACTIVATE, nr_deactivate);
2690 __count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE, nr_deactivate);
2691
2692 __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
2693 spin_unlock_irq(&lruvec->lru_lock);
2694
2695 if (nr_rotated)
2696 lru_note_cost(lruvec, file, 0, nr_rotated);
2697 mem_cgroup_uncharge_list(&l_active);
2698 free_unref_page_list(&l_active);
2699 trace_mm_vmscan_lru_shrink_active(pgdat->node_id, nr_taken, nr_activate,
2700 nr_deactivate, nr_rotated, sc->priority, file);
2701}
2702
2703static unsigned int reclaim_folio_list(struct list_head *folio_list,
2704 struct pglist_data *pgdat)
2705{
2706 struct reclaim_stat dummy_stat;
2707 unsigned int nr_reclaimed;
2708 struct folio *folio;
2709 struct scan_control sc = {
2710 .gfp_mask = GFP_KERNEL,
2711 .may_writepage = 1,
2712 .may_unmap = 1,
2713 .may_swap = 1,
2714 .no_demotion = 1,
2715 };
2716
2717 nr_reclaimed = shrink_folio_list(folio_list, pgdat, &sc, &dummy_stat, false);
2718 while (!list_empty(folio_list)) {
2719 folio = lru_to_folio(folio_list);
2720 list_del(&folio->lru);
2721 folio_putback_lru(folio);
2722 }
2723
2724 return nr_reclaimed;
2725}
2726
2727unsigned long reclaim_pages(struct list_head *folio_list)
2728{
2729 int nid;
2730 unsigned int nr_reclaimed = 0;
2731 LIST_HEAD(node_folio_list);
2732 unsigned int noreclaim_flag;
2733
2734 if (list_empty(folio_list))
2735 return nr_reclaimed;
2736
2737 noreclaim_flag = memalloc_noreclaim_save();
2738
2739 nid = folio_nid(lru_to_folio(folio_list));
2740 do {
2741 struct folio *folio = lru_to_folio(folio_list);
2742
2743 if (nid == folio_nid(folio)) {
2744 folio_clear_active(folio);
2745 list_move(&folio->lru, &node_folio_list);
2746 continue;
2747 }
2748
2749 nr_reclaimed += reclaim_folio_list(&node_folio_list, NODE_DATA(nid));
2750 nid = folio_nid(lru_to_folio(folio_list));
2751 } while (!list_empty(folio_list));
2752
2753 nr_reclaimed += reclaim_folio_list(&node_folio_list, NODE_DATA(nid));
2754
2755 memalloc_noreclaim_restore(noreclaim_flag);
2756
2757 return nr_reclaimed;
2758}
2759
2760static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
2761 struct lruvec *lruvec, struct scan_control *sc)
2762{
2763 if (is_active_lru(lru)) {
2764 if (sc->may_deactivate & (1 << is_file_lru(lru)))
2765 shrink_active_list(nr_to_scan, lruvec, sc, lru);
2766 else
2767 sc->skipped_deactivate = 1;
2768 return 0;
2769 }
2770
2771 return shrink_inactive_list(nr_to_scan, lruvec, sc, lru);
2772}
2773
2774/*
2775 * The inactive anon list should be small enough that the VM never has
2776 * to do too much work.
2777 *
2778 * The inactive file list should be small enough to leave most memory
2779 * to the established workingset on the scan-resistant active list,
2780 * but large enough to avoid thrashing the aggregate readahead window.
2781 *
2782 * Both inactive lists should also be large enough that each inactive
2783 * folio has a chance to be referenced again before it is reclaimed.
2784 *
2785 * If that fails and refaulting is observed, the inactive list grows.
2786 *
2787 * The inactive_ratio is the target ratio of ACTIVE to INACTIVE folios
2788 * on this LRU, maintained by the pageout code. An inactive_ratio
2789 * of 3 means 3:1 or 25% of the folios are kept on the inactive list.
2790 *
2791 * total target max
2792 * memory ratio inactive
2793 * -------------------------------------
2794 * 10MB 1 5MB
2795 * 100MB 1 50MB
2796 * 1GB 3 250MB
2797 * 10GB 10 0.9GB
2798 * 100GB 31 3GB
2799 * 1TB 101 10GB
2800 * 10TB 320 32GB
2801 */
2802static bool inactive_is_low(struct lruvec *lruvec, enum lru_list inactive_lru)
2803{
2804 enum lru_list active_lru = inactive_lru + LRU_ACTIVE;
2805 unsigned long inactive, active;
2806 unsigned long inactive_ratio;
2807 unsigned long gb;
2808
2809 inactive = lruvec_page_state(lruvec, NR_LRU_BASE + inactive_lru);
2810 active = lruvec_page_state(lruvec, NR_LRU_BASE + active_lru);
2811
2812 gb = (inactive + active) >> (30 - PAGE_SHIFT);
2813 if (gb)
2814 inactive_ratio = int_sqrt(10 * gb);
2815 else
2816 inactive_ratio = 1;
2817
2818 return inactive * inactive_ratio < active;
2819}
2820
2821enum scan_balance {
2822 SCAN_EQUAL,
2823 SCAN_FRACT,
2824 SCAN_ANON,
2825 SCAN_FILE,
2826};
2827
2828static void prepare_scan_count(pg_data_t *pgdat, struct scan_control *sc)
2829{
2830 unsigned long file;
2831 struct lruvec *target_lruvec;
2832
2833 if (lru_gen_enabled())
2834 return;
2835
2836 target_lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup, pgdat);
2837
2838 /*
2839 * Flush the memory cgroup stats, so that we read accurate per-memcg
2840 * lruvec stats for heuristics.
2841 */
2842 mem_cgroup_flush_stats();
2843
2844 /*
2845 * Determine the scan balance between anon and file LRUs.
2846 */
2847 spin_lock_irq(&target_lruvec->lru_lock);
2848 sc->anon_cost = target_lruvec->anon_cost;
2849 sc->file_cost = target_lruvec->file_cost;
2850 spin_unlock_irq(&target_lruvec->lru_lock);
2851
2852 /*
2853 * Target desirable inactive:active list ratios for the anon
2854 * and file LRU lists.
2855 */
2856 if (!sc->force_deactivate) {
2857 unsigned long refaults;
2858
2859 /*
2860 * When refaults are being observed, it means a new
2861 * workingset is being established. Deactivate to get
2862 * rid of any stale active pages quickly.
2863 */
2864 refaults = lruvec_page_state(target_lruvec,
2865 WORKINGSET_ACTIVATE_ANON);
2866 if (refaults != target_lruvec->refaults[WORKINGSET_ANON] ||
2867 inactive_is_low(target_lruvec, LRU_INACTIVE_ANON))
2868 sc->may_deactivate |= DEACTIVATE_ANON;
2869 else
2870 sc->may_deactivate &= ~DEACTIVATE_ANON;
2871
2872 refaults = lruvec_page_state(target_lruvec,
2873 WORKINGSET_ACTIVATE_FILE);
2874 if (refaults != target_lruvec->refaults[WORKINGSET_FILE] ||
2875 inactive_is_low(target_lruvec, LRU_INACTIVE_FILE))
2876 sc->may_deactivate |= DEACTIVATE_FILE;
2877 else
2878 sc->may_deactivate &= ~DEACTIVATE_FILE;
2879 } else
2880 sc->may_deactivate = DEACTIVATE_ANON | DEACTIVATE_FILE;
2881
2882 /*
2883 * If we have plenty of inactive file pages that aren't
2884 * thrashing, try to reclaim those first before touching
2885 * anonymous pages.
2886 */
2887 file = lruvec_page_state(target_lruvec, NR_INACTIVE_FILE);
2888 if (file >> sc->priority && !(sc->may_deactivate & DEACTIVATE_FILE))
2889 sc->cache_trim_mode = 1;
2890 else
2891 sc->cache_trim_mode = 0;
2892
2893 /*
2894 * Prevent the reclaimer from falling into the cache trap: as
2895 * cache pages start out inactive, every cache fault will tip
2896 * the scan balance towards the file LRU. And as the file LRU
2897 * shrinks, so does the window for rotation from references.
2898 * This means we have a runaway feedback loop where a tiny
2899 * thrashing file LRU becomes infinitely more attractive than
2900 * anon pages. Try to detect this based on file LRU size.
2901 */
2902 if (!cgroup_reclaim(sc)) {
2903 unsigned long total_high_wmark = 0;
2904 unsigned long free, anon;
2905 int z;
2906
2907 free = sum_zone_node_page_state(pgdat->node_id, NR_FREE_PAGES);
2908 file = node_page_state(pgdat, NR_ACTIVE_FILE) +
2909 node_page_state(pgdat, NR_INACTIVE_FILE);
2910
2911 for (z = 0; z < MAX_NR_ZONES; z++) {
2912 struct zone *zone = &pgdat->node_zones[z];
2913
2914 if (!managed_zone(zone))
2915 continue;
2916
2917 total_high_wmark += high_wmark_pages(zone);
2918 }
2919
2920 /*
2921 * Consider anon: if that's low too, this isn't a
2922 * runaway file reclaim problem, but rather just
2923 * extreme pressure. Reclaim as per usual then.
2924 */
2925 anon = node_page_state(pgdat, NR_INACTIVE_ANON);
2926
2927 sc->file_is_tiny =
2928 file + free <= total_high_wmark &&
2929 !(sc->may_deactivate & DEACTIVATE_ANON) &&
2930 anon >> sc->priority;
2931 }
2932}
2933
2934/*
2935 * Determine how aggressively the anon and file LRU lists should be
2936 * scanned.
2937 *
2938 * nr[0] = anon inactive folios to scan; nr[1] = anon active folios to scan
2939 * nr[2] = file inactive folios to scan; nr[3] = file active folios to scan
2940 */
2941static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
2942 unsigned long *nr)
2943{
2944 struct pglist_data *pgdat = lruvec_pgdat(lruvec);
2945 struct mem_cgroup *memcg = lruvec_memcg(lruvec);
2946 unsigned long anon_cost, file_cost, total_cost;
2947 int swappiness = mem_cgroup_swappiness(memcg);
2948 u64 fraction[ANON_AND_FILE];
2949 u64 denominator = 0; /* gcc */
2950 enum scan_balance scan_balance;
2951 unsigned long ap, fp;
2952 enum lru_list lru;
2953
2954 /* If we have no swap space, do not bother scanning anon folios. */
2955 if (!sc->may_swap || !can_reclaim_anon_pages(memcg, pgdat->node_id, sc)) {
2956 scan_balance = SCAN_FILE;
2957 goto out;
2958 }
2959
2960 /*
2961 * Global reclaim will swap to prevent OOM even with no
2962 * swappiness, but memcg users want to use this knob to
2963 * disable swapping for individual groups completely when
2964 * using the memory controller's swap limit feature would be
2965 * too expensive.
2966 */
2967 if (cgroup_reclaim(sc) && !swappiness) {
2968 scan_balance = SCAN_FILE;
2969 goto out;
2970 }
2971
2972 /*
2973 * Do not apply any pressure balancing cleverness when the
2974 * system is close to OOM, scan both anon and file equally
2975 * (unless the swappiness setting disagrees with swapping).
2976 */
2977 if (!sc->priority && swappiness) {
2978 scan_balance = SCAN_EQUAL;
2979 goto out;
2980 }
2981
2982 /*
2983 * If the system is almost out of file pages, force-scan anon.
2984 */
2985 if (sc->file_is_tiny) {
2986 scan_balance = SCAN_ANON;
2987 goto out;
2988 }
2989
2990 /*
2991 * If there is enough inactive page cache, we do not reclaim
2992 * anything from the anonymous working right now.
2993 */
2994 if (sc->cache_trim_mode) {
2995 scan_balance = SCAN_FILE;
2996 goto out;
2997 }
2998
2999 scan_balance = SCAN_FRACT;
3000 /*
3001 * Calculate the pressure balance between anon and file pages.
3002 *
3003 * The amount of pressure we put on each LRU is inversely
3004 * proportional to the cost of reclaiming each list, as
3005 * determined by the share of pages that are refaulting, times
3006 * the relative IO cost of bringing back a swapped out
3007 * anonymous page vs reloading a filesystem page (swappiness).
3008 *
3009 * Although we limit that influence to ensure no list gets
3010 * left behind completely: at least a third of the pressure is
3011 * applied, before swappiness.
3012 *
3013 * With swappiness at 100, anon and file have equal IO cost.
3014 */
3015 total_cost = sc->anon_cost + sc->file_cost;
3016 anon_cost = total_cost + sc->anon_cost;
3017 file_cost = total_cost + sc->file_cost;
3018 total_cost = anon_cost + file_cost;
3019
3020 ap = swappiness * (total_cost + 1);
3021 ap /= anon_cost + 1;
3022
3023 fp = (200 - swappiness) * (total_cost + 1);
3024 fp /= file_cost + 1;
3025
3026 fraction[0] = ap;
3027 fraction[1] = fp;
3028 denominator = ap + fp;
3029out:
3030 for_each_evictable_lru(lru) {
3031 int file = is_file_lru(lru);
3032 unsigned long lruvec_size;
3033 unsigned long low, min;
3034 unsigned long scan;
3035
3036 lruvec_size = lruvec_lru_size(lruvec, lru, sc->reclaim_idx);
3037 mem_cgroup_protection(sc->target_mem_cgroup, memcg,
3038 &min, &low);
3039
3040 if (min || low) {
3041 /*
3042 * Scale a cgroup's reclaim pressure by proportioning
3043 * its current usage to its memory.low or memory.min
3044 * setting.
3045 *
3046 * This is important, as otherwise scanning aggression
3047 * becomes extremely binary -- from nothing as we
3048 * approach the memory protection threshold, to totally
3049 * nominal as we exceed it. This results in requiring
3050 * setting extremely liberal protection thresholds. It
3051 * also means we simply get no protection at all if we
3052 * set it too low, which is not ideal.
3053 *
3054 * If there is any protection in place, we reduce scan
3055 * pressure by how much of the total memory used is
3056 * within protection thresholds.
3057 *
3058 * There is one special case: in the first reclaim pass,
3059 * we skip over all groups that are within their low
3060 * protection. If that fails to reclaim enough pages to
3061 * satisfy the reclaim goal, we come back and override
3062 * the best-effort low protection. However, we still
3063 * ideally want to honor how well-behaved groups are in
3064 * that case instead of simply punishing them all
3065 * equally. As such, we reclaim them based on how much
3066 * memory they are using, reducing the scan pressure
3067 * again by how much of the total memory used is under
3068 * hard protection.
3069 */
3070 unsigned long cgroup_size = mem_cgroup_size(memcg);
3071 unsigned long protection;
3072
3073 /* memory.low scaling, make sure we retry before OOM */
3074 if (!sc->memcg_low_reclaim && low > min) {
3075 protection = low;
3076 sc->memcg_low_skipped = 1;
3077 } else {
3078 protection = min;
3079 }
3080
3081 /* Avoid TOCTOU with earlier protection check */
3082 cgroup_size = max(cgroup_size, protection);
3083
3084 scan = lruvec_size - lruvec_size * protection /
3085 (cgroup_size + 1);
3086
3087 /*
3088 * Minimally target SWAP_CLUSTER_MAX pages to keep
3089 * reclaim moving forwards, avoiding decrementing
3090 * sc->priority further than desirable.
3091 */
3092 scan = max(scan, SWAP_CLUSTER_MAX);
3093 } else {
3094 scan = lruvec_size;
3095 }
3096
3097 scan >>= sc->priority;
3098
3099 /*
3100 * If the cgroup's already been deleted, make sure to
3101 * scrape out the remaining cache.
3102 */
3103 if (!scan && !mem_cgroup_online(memcg))
3104 scan = min(lruvec_size, SWAP_CLUSTER_MAX);
3105
3106 switch (scan_balance) {
3107 case SCAN_EQUAL:
3108 /* Scan lists relative to size */
3109 break;
3110 case SCAN_FRACT:
3111 /*
3112 * Scan types proportional to swappiness and
3113 * their relative recent reclaim efficiency.
3114 * Make sure we don't miss the last page on
3115 * the offlined memory cgroups because of a
3116 * round-off error.
3117 */
3118 scan = mem_cgroup_online(memcg) ?
3119 div64_u64(scan * fraction[file], denominator) :
3120 DIV64_U64_ROUND_UP(scan * fraction[file],
3121 denominator);
3122 break;
3123 case SCAN_FILE:
3124 case SCAN_ANON:
3125 /* Scan one type exclusively */
3126 if ((scan_balance == SCAN_FILE) != file)
3127 scan = 0;
3128 break;
3129 default:
3130 /* Look ma, no brain */
3131 BUG();
3132 }
3133
3134 nr[lru] = scan;
3135 }
3136}
3137
3138/*
3139 * Anonymous LRU management is a waste if there is
3140 * ultimately no way to reclaim the memory.
3141 */
3142static bool can_age_anon_pages(struct pglist_data *pgdat,
3143 struct scan_control *sc)
3144{
3145 /* Aging the anon LRU is valuable if swap is present: */
3146 if (total_swap_pages > 0)
3147 return true;
3148
3149 /* Also valuable if anon pages can be demoted: */
3150 return can_demote(pgdat->node_id, sc);
3151}
3152
3153#ifdef CONFIG_LRU_GEN
3154
3155#ifdef CONFIG_LRU_GEN_ENABLED
3156DEFINE_STATIC_KEY_ARRAY_TRUE(lru_gen_caps, NR_LRU_GEN_CAPS);
3157#define get_cap(cap) static_branch_likely(&lru_gen_caps[cap])
3158#else
3159DEFINE_STATIC_KEY_ARRAY_FALSE(lru_gen_caps, NR_LRU_GEN_CAPS);
3160#define get_cap(cap) static_branch_unlikely(&lru_gen_caps[cap])
3161#endif
3162
3163/******************************************************************************
3164 * shorthand helpers
3165 ******************************************************************************/
3166
3167#define LRU_REFS_FLAGS (BIT(PG_referenced) | BIT(PG_workingset))
3168
3169#define DEFINE_MAX_SEQ(lruvec) \
3170 unsigned long max_seq = READ_ONCE((lruvec)->lrugen.max_seq)
3171
3172#define DEFINE_MIN_SEQ(lruvec) \
3173 unsigned long min_seq[ANON_AND_FILE] = { \
3174 READ_ONCE((lruvec)->lrugen.min_seq[LRU_GEN_ANON]), \
3175 READ_ONCE((lruvec)->lrugen.min_seq[LRU_GEN_FILE]), \
3176 }
3177
3178#define for_each_gen_type_zone(gen, type, zone) \
3179 for ((gen) = 0; (gen) < MAX_NR_GENS; (gen)++) \
3180 for ((type) = 0; (type) < ANON_AND_FILE; (type)++) \
3181 for ((zone) = 0; (zone) < MAX_NR_ZONES; (zone)++)
3182
3183static struct lruvec *get_lruvec(struct mem_cgroup *memcg, int nid)
3184{
3185 struct pglist_data *pgdat = NODE_DATA(nid);
3186
3187#ifdef CONFIG_MEMCG
3188 if (memcg) {
3189 struct lruvec *lruvec = &memcg->nodeinfo[nid]->lruvec;
3190
3191 /* see the comment in mem_cgroup_lruvec() */
3192 if (!lruvec->pgdat)
3193 lruvec->pgdat = pgdat;
3194
3195 return lruvec;
3196 }
3197#endif
3198 VM_WARN_ON_ONCE(!mem_cgroup_disabled());
3199
3200 return &pgdat->__lruvec;
3201}
3202
3203static int get_swappiness(struct lruvec *lruvec, struct scan_control *sc)
3204{
3205 struct mem_cgroup *memcg = lruvec_memcg(lruvec);
3206 struct pglist_data *pgdat = lruvec_pgdat(lruvec);
3207
3208 if (!can_demote(pgdat->node_id, sc) &&
3209 mem_cgroup_get_nr_swap_pages(memcg) < MIN_LRU_BATCH)
3210 return 0;
3211
3212 return mem_cgroup_swappiness(memcg);
3213}
3214
3215static int get_nr_gens(struct lruvec *lruvec, int type)
3216{
3217 return lruvec->lrugen.max_seq - lruvec->lrugen.min_seq[type] + 1;
3218}
3219
3220static bool __maybe_unused seq_is_valid(struct lruvec *lruvec)
3221{
3222 /* see the comment on lru_gen_struct */
3223 return get_nr_gens(lruvec, LRU_GEN_FILE) >= MIN_NR_GENS &&
3224 get_nr_gens(lruvec, LRU_GEN_FILE) <= get_nr_gens(lruvec, LRU_GEN_ANON) &&
3225 get_nr_gens(lruvec, LRU_GEN_ANON) <= MAX_NR_GENS;
3226}
3227
3228/******************************************************************************
3229 * mm_struct list
3230 ******************************************************************************/
3231
3232static struct lru_gen_mm_list *get_mm_list(struct mem_cgroup *memcg)
3233{
3234 static struct lru_gen_mm_list mm_list = {
3235 .fifo = LIST_HEAD_INIT(mm_list.fifo),
3236 .lock = __SPIN_LOCK_UNLOCKED(mm_list.lock),
3237 };
3238
3239#ifdef CONFIG_MEMCG
3240 if (memcg)
3241 return &memcg->mm_list;
3242#endif
3243 VM_WARN_ON_ONCE(!mem_cgroup_disabled());
3244
3245 return &mm_list;
3246}
3247
3248void lru_gen_add_mm(struct mm_struct *mm)
3249{
3250 int nid;
3251 struct mem_cgroup *memcg = get_mem_cgroup_from_mm(mm);
3252 struct lru_gen_mm_list *mm_list = get_mm_list(memcg);
3253
3254 VM_WARN_ON_ONCE(!list_empty(&mm->lru_gen.list));
3255#ifdef CONFIG_MEMCG
3256 VM_WARN_ON_ONCE(mm->lru_gen.memcg);
3257 mm->lru_gen.memcg = memcg;
3258#endif
3259 spin_lock(&mm_list->lock);
3260
3261 for_each_node_state(nid, N_MEMORY) {
3262 struct lruvec *lruvec = get_lruvec(memcg, nid);
3263
3264 /* the first addition since the last iteration */
3265 if (lruvec->mm_state.tail == &mm_list->fifo)
3266 lruvec->mm_state.tail = &mm->lru_gen.list;
3267 }
3268
3269 list_add_tail(&mm->lru_gen.list, &mm_list->fifo);
3270
3271 spin_unlock(&mm_list->lock);
3272}
3273
3274void lru_gen_del_mm(struct mm_struct *mm)
3275{
3276 int nid;
3277 struct lru_gen_mm_list *mm_list;
3278 struct mem_cgroup *memcg = NULL;
3279
3280 if (list_empty(&mm->lru_gen.list))
3281 return;
3282
3283#ifdef CONFIG_MEMCG
3284 memcg = mm->lru_gen.memcg;
3285#endif
3286 mm_list = get_mm_list(memcg);
3287
3288 spin_lock(&mm_list->lock);
3289
3290 for_each_node(nid) {
3291 struct lruvec *lruvec = get_lruvec(memcg, nid);
3292
3293 /* where the last iteration ended (exclusive) */
3294 if (lruvec->mm_state.tail == &mm->lru_gen.list)
3295 lruvec->mm_state.tail = lruvec->mm_state.tail->next;
3296
3297 /* where the current iteration continues (inclusive) */
3298 if (lruvec->mm_state.head != &mm->lru_gen.list)
3299 continue;
3300
3301 lruvec->mm_state.head = lruvec->mm_state.head->next;
3302 /* the deletion ends the current iteration */
3303 if (lruvec->mm_state.head == &mm_list->fifo)
3304 WRITE_ONCE(lruvec->mm_state.seq, lruvec->mm_state.seq + 1);
3305 }
3306
3307 list_del_init(&mm->lru_gen.list);
3308
3309 spin_unlock(&mm_list->lock);
3310
3311#ifdef CONFIG_MEMCG
3312 mem_cgroup_put(mm->lru_gen.memcg);
3313 mm->lru_gen.memcg = NULL;
3314#endif
3315}
3316
3317#ifdef CONFIG_MEMCG
3318void lru_gen_migrate_mm(struct mm_struct *mm)
3319{
3320 struct mem_cgroup *memcg;
3321 struct task_struct *task = rcu_dereference_protected(mm->owner, true);
3322
3323 VM_WARN_ON_ONCE(task->mm != mm);
3324 lockdep_assert_held(&task->alloc_lock);
3325
3326 /* for mm_update_next_owner() */
3327 if (mem_cgroup_disabled())
3328 return;
3329
3330 /* migration can happen before addition */
3331 if (!mm->lru_gen.memcg)
3332 return;
3333
3334 rcu_read_lock();
3335 memcg = mem_cgroup_from_task(task);
3336 rcu_read_unlock();
3337 if (memcg == mm->lru_gen.memcg)
3338 return;
3339
3340 VM_WARN_ON_ONCE(list_empty(&mm->lru_gen.list));
3341
3342 lru_gen_del_mm(mm);
3343 lru_gen_add_mm(mm);
3344}
3345#endif
3346
3347/*
3348 * Bloom filters with m=1<<15, k=2 and the false positive rates of ~1/5 when
3349 * n=10,000 and ~1/2 when n=20,000, where, conventionally, m is the number of
3350 * bits in a bitmap, k is the number of hash functions and n is the number of
3351 * inserted items.
3352 *
3353 * Page table walkers use one of the two filters to reduce their search space.
3354 * To get rid of non-leaf entries that no longer have enough leaf entries, the
3355 * aging uses the double-buffering technique to flip to the other filter each
3356 * time it produces a new generation. For non-leaf entries that have enough
3357 * leaf entries, the aging carries them over to the next generation in
3358 * walk_pmd_range(); the eviction also report them when walking the rmap
3359 * in lru_gen_look_around().
3360 *
3361 * For future optimizations:
3362 * 1. It's not necessary to keep both filters all the time. The spare one can be
3363 * freed after the RCU grace period and reallocated if needed again.
3364 * 2. And when reallocating, it's worth scaling its size according to the number
3365 * of inserted entries in the other filter, to reduce the memory overhead on
3366 * small systems and false positives on large systems.
3367 * 3. Jenkins' hash function is an alternative to Knuth's.
3368 */
3369#define BLOOM_FILTER_SHIFT 15
3370
3371static inline int filter_gen_from_seq(unsigned long seq)
3372{
3373 return seq % NR_BLOOM_FILTERS;
3374}
3375
3376static void get_item_key(void *item, int *key)
3377{
3378 u32 hash = hash_ptr(item, BLOOM_FILTER_SHIFT * 2);
3379
3380 BUILD_BUG_ON(BLOOM_FILTER_SHIFT * 2 > BITS_PER_TYPE(u32));
3381
3382 key[0] = hash & (BIT(BLOOM_FILTER_SHIFT) - 1);
3383 key[1] = hash >> BLOOM_FILTER_SHIFT;
3384}
3385
3386static void reset_bloom_filter(struct lruvec *lruvec, unsigned long seq)
3387{
3388 unsigned long *filter;
3389 int gen = filter_gen_from_seq(seq);
3390
3391 filter = lruvec->mm_state.filters[gen];
3392 if (filter) {
3393 bitmap_clear(filter, 0, BIT(BLOOM_FILTER_SHIFT));
3394 return;
3395 }
3396
3397 filter = bitmap_zalloc(BIT(BLOOM_FILTER_SHIFT),
3398 __GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN);
3399 WRITE_ONCE(lruvec->mm_state.filters[gen], filter);
3400}
3401
3402static void update_bloom_filter(struct lruvec *lruvec, unsigned long seq, void *item)
3403{
3404 int key[2];
3405 unsigned long *filter;
3406 int gen = filter_gen_from_seq(seq);
3407
3408 filter = READ_ONCE(lruvec->mm_state.filters[gen]);
3409 if (!filter)
3410 return;
3411
3412 get_item_key(item, key);
3413
3414 if (!test_bit(key[0], filter))
3415 set_bit(key[0], filter);
3416 if (!test_bit(key[1], filter))
3417 set_bit(key[1], filter);
3418}
3419
3420static bool test_bloom_filter(struct lruvec *lruvec, unsigned long seq, void *item)
3421{
3422 int key[2];
3423 unsigned long *filter;
3424 int gen = filter_gen_from_seq(seq);
3425
3426 filter = READ_ONCE(lruvec->mm_state.filters[gen]);
3427 if (!filter)
3428 return true;
3429
3430 get_item_key(item, key);
3431
3432 return test_bit(key[0], filter) && test_bit(key[1], filter);
3433}
3434
3435static void reset_mm_stats(struct lruvec *lruvec, struct lru_gen_mm_walk *walk, bool last)
3436{
3437 int i;
3438 int hist;
3439
3440 lockdep_assert_held(&get_mm_list(lruvec_memcg(lruvec))->lock);
3441
3442 if (walk) {
3443 hist = lru_hist_from_seq(walk->max_seq);
3444
3445 for (i = 0; i < NR_MM_STATS; i++) {
3446 WRITE_ONCE(lruvec->mm_state.stats[hist][i],
3447 lruvec->mm_state.stats[hist][i] + walk->mm_stats[i]);
3448 walk->mm_stats[i] = 0;
3449 }
3450 }
3451
3452 if (NR_HIST_GENS > 1 && last) {
3453 hist = lru_hist_from_seq(lruvec->mm_state.seq + 1);
3454
3455 for (i = 0; i < NR_MM_STATS; i++)
3456 WRITE_ONCE(lruvec->mm_state.stats[hist][i], 0);
3457 }
3458}
3459
3460static bool should_skip_mm(struct mm_struct *mm, struct lru_gen_mm_walk *walk)
3461{
3462 int type;
3463 unsigned long size = 0;
3464 struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);
3465 int key = pgdat->node_id % BITS_PER_TYPE(mm->lru_gen.bitmap);
3466
3467 if (!walk->force_scan && !test_bit(key, &mm->lru_gen.bitmap))
3468 return true;
3469
3470 clear_bit(key, &mm->lru_gen.bitmap);
3471
3472 for (type = !walk->can_swap; type < ANON_AND_FILE; type++) {
3473 size += type ? get_mm_counter(mm, MM_FILEPAGES) :
3474 get_mm_counter(mm, MM_ANONPAGES) +
3475 get_mm_counter(mm, MM_SHMEMPAGES);
3476 }
3477
3478 if (size < MIN_LRU_BATCH)
3479 return true;
3480
3481 return !mmget_not_zero(mm);
3482}
3483
3484static bool iterate_mm_list(struct lruvec *lruvec, struct lru_gen_mm_walk *walk,
3485 struct mm_struct **iter)
3486{
3487 bool first = false;
3488 bool last = true;
3489 struct mm_struct *mm = NULL;
3490 struct mem_cgroup *memcg = lruvec_memcg(lruvec);
3491 struct lru_gen_mm_list *mm_list = get_mm_list(memcg);
3492 struct lru_gen_mm_state *mm_state = &lruvec->mm_state;
3493
3494 /*
3495 * There are four interesting cases for this page table walker:
3496 * 1. It tries to start a new iteration of mm_list with a stale max_seq;
3497 * there is nothing left to do.
3498 * 2. It's the first of the current generation, and it needs to reset
3499 * the Bloom filter for the next generation.
3500 * 3. It reaches the end of mm_list, and it needs to increment
3501 * mm_state->seq; the iteration is done.
3502 * 4. It's the last of the current generation, and it needs to reset the
3503 * mm stats counters for the next generation.
3504 */
3505 spin_lock(&mm_list->lock);
3506
3507 VM_WARN_ON_ONCE(mm_state->seq + 1 < walk->max_seq);
3508 VM_WARN_ON_ONCE(*iter && mm_state->seq > walk->max_seq);
3509 VM_WARN_ON_ONCE(*iter && !mm_state->nr_walkers);
3510
3511 if (walk->max_seq <= mm_state->seq) {
3512 if (!*iter)
3513 last = false;
3514 goto done;
3515 }
3516
3517 if (!mm_state->nr_walkers) {
3518 VM_WARN_ON_ONCE(mm_state->head && mm_state->head != &mm_list->fifo);
3519
3520 mm_state->head = mm_list->fifo.next;
3521 first = true;
3522 }
3523
3524 while (!mm && mm_state->head != &mm_list->fifo) {
3525 mm = list_entry(mm_state->head, struct mm_struct, lru_gen.list);
3526
3527 mm_state->head = mm_state->head->next;
3528
3529 /* force scan for those added after the last iteration */
3530 if (!mm_state->tail || mm_state->tail == &mm->lru_gen.list) {
3531 mm_state->tail = mm_state->head;
3532 walk->force_scan = true;
3533 }
3534
3535 if (should_skip_mm(mm, walk))
3536 mm = NULL;
3537 }
3538
3539 if (mm_state->head == &mm_list->fifo)
3540 WRITE_ONCE(mm_state->seq, mm_state->seq + 1);
3541done:
3542 if (*iter && !mm)
3543 mm_state->nr_walkers--;
3544 if (!*iter && mm)
3545 mm_state->nr_walkers++;
3546
3547 if (mm_state->nr_walkers)
3548 last = false;
3549
3550 if (*iter || last)
3551 reset_mm_stats(lruvec, walk, last);
3552
3553 spin_unlock(&mm_list->lock);
3554
3555 if (mm && first)
3556 reset_bloom_filter(lruvec, walk->max_seq + 1);
3557
3558 if (*iter)
3559 mmput_async(*iter);
3560
3561 *iter = mm;
3562
3563 return last;
3564}
3565
3566static bool iterate_mm_list_nowalk(struct lruvec *lruvec, unsigned long max_seq)
3567{
3568 bool success = false;
3569 struct mem_cgroup *memcg = lruvec_memcg(lruvec);
3570 struct lru_gen_mm_list *mm_list = get_mm_list(memcg);
3571 struct lru_gen_mm_state *mm_state = &lruvec->mm_state;
3572
3573 spin_lock(&mm_list->lock);
3574
3575 VM_WARN_ON_ONCE(mm_state->seq + 1 < max_seq);
3576
3577 if (max_seq > mm_state->seq && !mm_state->nr_walkers) {
3578 VM_WARN_ON_ONCE(mm_state->head && mm_state->head != &mm_list->fifo);
3579
3580 WRITE_ONCE(mm_state->seq, mm_state->seq + 1);
3581 reset_mm_stats(lruvec, NULL, true);
3582 success = true;
3583 }
3584
3585 spin_unlock(&mm_list->lock);
3586
3587 return success;
3588}
3589
3590/******************************************************************************
3591 * refault feedback loop
3592 ******************************************************************************/
3593
3594/*
3595 * A feedback loop based on Proportional-Integral-Derivative (PID) controller.
3596 *
3597 * The P term is refaulted/(evicted+protected) from a tier in the generation
3598 * currently being evicted; the I term is the exponential moving average of the
3599 * P term over the generations previously evicted, using the smoothing factor
3600 * 1/2; the D term isn't supported.
3601 *
3602 * The setpoint (SP) is always the first tier of one type; the process variable
3603 * (PV) is either any tier of the other type or any other tier of the same
3604 * type.
3605 *
3606 * The error is the difference between the SP and the PV; the correction is to
3607 * turn off protection when SP>PV or turn on protection when SP<PV.
3608 *
3609 * For future optimizations:
3610 * 1. The D term may discount the other two terms over time so that long-lived
3611 * generations can resist stale information.
3612 */
3613struct ctrl_pos {
3614 unsigned long refaulted;
3615 unsigned long total;
3616 int gain;
3617};
3618
3619static void read_ctrl_pos(struct lruvec *lruvec, int type, int tier, int gain,
3620 struct ctrl_pos *pos)
3621{
3622 struct lru_gen_struct *lrugen = &lruvec->lrugen;
3623 int hist = lru_hist_from_seq(lrugen->min_seq[type]);
3624
3625 pos->refaulted = lrugen->avg_refaulted[type][tier] +
3626 atomic_long_read(&lrugen->refaulted[hist][type][tier]);
3627 pos->total = lrugen->avg_total[type][tier] +
3628 atomic_long_read(&lrugen->evicted[hist][type][tier]);
3629 if (tier)
3630 pos->total += lrugen->protected[hist][type][tier - 1];
3631 pos->gain = gain;
3632}
3633
3634static void reset_ctrl_pos(struct lruvec *lruvec, int type, bool carryover)
3635{
3636 int hist, tier;
3637 struct lru_gen_struct *lrugen = &lruvec->lrugen;
3638 bool clear = carryover ? NR_HIST_GENS == 1 : NR_HIST_GENS > 1;
3639 unsigned long seq = carryover ? lrugen->min_seq[type] : lrugen->max_seq + 1;
3640
3641 lockdep_assert_held(&lruvec->lru_lock);
3642
3643 if (!carryover && !clear)
3644 return;
3645
3646 hist = lru_hist_from_seq(seq);
3647
3648 for (tier = 0; tier < MAX_NR_TIERS; tier++) {
3649 if (carryover) {
3650 unsigned long sum;
3651
3652 sum = lrugen->avg_refaulted[type][tier] +
3653 atomic_long_read(&lrugen->refaulted[hist][type][tier]);
3654 WRITE_ONCE(lrugen->avg_refaulted[type][tier], sum / 2);
3655
3656 sum = lrugen->avg_total[type][tier] +
3657 atomic_long_read(&lrugen->evicted[hist][type][tier]);
3658 if (tier)
3659 sum += lrugen->protected[hist][type][tier - 1];
3660 WRITE_ONCE(lrugen->avg_total[type][tier], sum / 2);
3661 }
3662
3663 if (clear) {
3664 atomic_long_set(&lrugen->refaulted[hist][type][tier], 0);
3665 atomic_long_set(&lrugen->evicted[hist][type][tier], 0);
3666 if (tier)
3667 WRITE_ONCE(lrugen->protected[hist][type][tier - 1], 0);
3668 }
3669 }
3670}
3671
3672static bool positive_ctrl_err(struct ctrl_pos *sp, struct ctrl_pos *pv)
3673{
3674 /*
3675 * Return true if the PV has a limited number of refaults or a lower
3676 * refaulted/total than the SP.
3677 */
3678 return pv->refaulted < MIN_LRU_BATCH ||
3679 pv->refaulted * (sp->total + MIN_LRU_BATCH) * sp->gain <=
3680 (sp->refaulted + 1) * pv->total * pv->gain;
3681}
3682
3683/******************************************************************************
3684 * the aging
3685 ******************************************************************************/
3686
3687/* promote pages accessed through page tables */
3688static int folio_update_gen(struct folio *folio, int gen)
3689{
3690 unsigned long new_flags, old_flags = READ_ONCE(folio->flags);
3691
3692 VM_WARN_ON_ONCE(gen >= MAX_NR_GENS);
3693 VM_WARN_ON_ONCE(!rcu_read_lock_held());
3694
3695 do {
3696 /* lru_gen_del_folio() has isolated this page? */
3697 if (!(old_flags & LRU_GEN_MASK)) {
3698 /* for shrink_folio_list() */
3699 new_flags = old_flags | BIT(PG_referenced);
3700 continue;
3701 }
3702
3703 new_flags = old_flags & ~(LRU_GEN_MASK | LRU_REFS_MASK | LRU_REFS_FLAGS);
3704 new_flags |= (gen + 1UL) << LRU_GEN_PGOFF;
3705 } while (!try_cmpxchg(&folio->flags, &old_flags, new_flags));
3706
3707 return ((old_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1;
3708}
3709
3710/* protect pages accessed multiple times through file descriptors */
3711static int folio_inc_gen(struct lruvec *lruvec, struct folio *folio, bool reclaiming)
3712{
3713 int type = folio_is_file_lru(folio);
3714 struct lru_gen_struct *lrugen = &lruvec->lrugen;
3715 int new_gen, old_gen = lru_gen_from_seq(lrugen->min_seq[type]);
3716 unsigned long new_flags, old_flags = READ_ONCE(folio->flags);
3717
3718 VM_WARN_ON_ONCE_FOLIO(!(old_flags & LRU_GEN_MASK), folio);
3719
3720 do {
3721 new_gen = ((old_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1;
3722 /* folio_update_gen() has promoted this page? */
3723 if (new_gen >= 0 && new_gen != old_gen)
3724 return new_gen;
3725
3726 new_gen = (old_gen + 1) % MAX_NR_GENS;
3727
3728 new_flags = old_flags & ~(LRU_GEN_MASK | LRU_REFS_MASK | LRU_REFS_FLAGS);
3729 new_flags |= (new_gen + 1UL) << LRU_GEN_PGOFF;
3730 /* for folio_end_writeback() */
3731 if (reclaiming)
3732 new_flags |= BIT(PG_reclaim);
3733 } while (!try_cmpxchg(&folio->flags, &old_flags, new_flags));
3734
3735 lru_gen_update_size(lruvec, folio, old_gen, new_gen);
3736
3737 return new_gen;
3738}
3739
3740static void update_batch_size(struct lru_gen_mm_walk *walk, struct folio *folio,
3741 int old_gen, int new_gen)
3742{
3743 int type = folio_is_file_lru(folio);
3744 int zone = folio_zonenum(folio);
3745 int delta = folio_nr_pages(folio);
3746
3747 VM_WARN_ON_ONCE(old_gen >= MAX_NR_GENS);
3748 VM_WARN_ON_ONCE(new_gen >= MAX_NR_GENS);
3749
3750 walk->batched++;
3751
3752 walk->nr_pages[old_gen][type][zone] -= delta;
3753 walk->nr_pages[new_gen][type][zone] += delta;
3754}
3755
3756static void reset_batch_size(struct lruvec *lruvec, struct lru_gen_mm_walk *walk)
3757{
3758 int gen, type, zone;
3759 struct lru_gen_struct *lrugen = &lruvec->lrugen;
3760
3761 walk->batched = 0;
3762
3763 for_each_gen_type_zone(gen, type, zone) {
3764 enum lru_list lru = type * LRU_INACTIVE_FILE;
3765 int delta = walk->nr_pages[gen][type][zone];
3766
3767 if (!delta)
3768 continue;
3769
3770 walk->nr_pages[gen][type][zone] = 0;
3771 WRITE_ONCE(lrugen->nr_pages[gen][type][zone],
3772 lrugen->nr_pages[gen][type][zone] + delta);
3773
3774 if (lru_gen_is_active(lruvec, gen))
3775 lru += LRU_ACTIVE;
3776 __update_lru_size(lruvec, lru, zone, delta);
3777 }
3778}
3779
3780static int should_skip_vma(unsigned long start, unsigned long end, struct mm_walk *args)
3781{
3782 struct address_space *mapping;
3783 struct vm_area_struct *vma = args->vma;
3784 struct lru_gen_mm_walk *walk = args->private;
3785
3786 if (!vma_is_accessible(vma))
3787 return true;
3788
3789 if (is_vm_hugetlb_page(vma))
3790 return true;
3791
3792 if (vma->vm_flags & (VM_LOCKED | VM_SPECIAL | VM_SEQ_READ | VM_RAND_READ))
3793 return true;
3794
3795 if (vma == get_gate_vma(vma->vm_mm))
3796 return true;
3797
3798 if (vma_is_anonymous(vma))
3799 return !walk->can_swap;
3800
3801 if (WARN_ON_ONCE(!vma->vm_file || !vma->vm_file->f_mapping))
3802 return true;
3803
3804 mapping = vma->vm_file->f_mapping;
3805 if (mapping_unevictable(mapping))
3806 return true;
3807
3808 if (shmem_mapping(mapping))
3809 return !walk->can_swap;
3810
3811 /* to exclude special mappings like dax, etc. */
3812 return !mapping->a_ops->read_folio;
3813}
3814
3815/*
3816 * Some userspace memory allocators map many single-page VMAs. Instead of
3817 * returning back to the PGD table for each of such VMAs, finish an entire PMD
3818 * table to reduce zigzags and improve cache performance.
3819 */
3820static bool get_next_vma(unsigned long mask, unsigned long size, struct mm_walk *args,
3821 unsigned long *vm_start, unsigned long *vm_end)
3822{
3823 unsigned long start = round_up(*vm_end, size);
3824 unsigned long end = (start | ~mask) + 1;
3825 VMA_ITERATOR(vmi, args->mm, start);
3826
3827 VM_WARN_ON_ONCE(mask & size);
3828 VM_WARN_ON_ONCE((start & mask) != (*vm_start & mask));
3829
3830 for_each_vma(vmi, args->vma) {
3831 if (end && end <= args->vma->vm_start)
3832 return false;
3833
3834 if (should_skip_vma(args->vma->vm_start, args->vma->vm_end, args))
3835 continue;
3836
3837 *vm_start = max(start, args->vma->vm_start);
3838 *vm_end = min(end - 1, args->vma->vm_end - 1) + 1;
3839
3840 return true;
3841 }
3842
3843 return false;
3844}
3845
3846static unsigned long get_pte_pfn(pte_t pte, struct vm_area_struct *vma, unsigned long addr)
3847{
3848 unsigned long pfn = pte_pfn(pte);
3849
3850 VM_WARN_ON_ONCE(addr < vma->vm_start || addr >= vma->vm_end);
3851
3852 if (!pte_present(pte) || is_zero_pfn(pfn))
3853 return -1;
3854
3855 if (WARN_ON_ONCE(pte_devmap(pte) || pte_special(pte)))
3856 return -1;
3857
3858 if (WARN_ON_ONCE(!pfn_valid(pfn)))
3859 return -1;
3860
3861 return pfn;
3862}
3863
3864#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG)
3865static unsigned long get_pmd_pfn(pmd_t pmd, struct vm_area_struct *vma, unsigned long addr)
3866{
3867 unsigned long pfn = pmd_pfn(pmd);
3868
3869 VM_WARN_ON_ONCE(addr < vma->vm_start || addr >= vma->vm_end);
3870
3871 if (!pmd_present(pmd) || is_huge_zero_pmd(pmd))
3872 return -1;
3873
3874 if (WARN_ON_ONCE(pmd_devmap(pmd)))
3875 return -1;
3876
3877 if (WARN_ON_ONCE(!pfn_valid(pfn)))
3878 return -1;
3879
3880 return pfn;
3881}
3882#endif
3883
3884static struct folio *get_pfn_folio(unsigned long pfn, struct mem_cgroup *memcg,
3885 struct pglist_data *pgdat, bool can_swap)
3886{
3887 struct folio *folio;
3888
3889 /* try to avoid unnecessary memory loads */
3890 if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat))
3891 return NULL;
3892
3893 folio = pfn_folio(pfn);
3894 if (folio_nid(folio) != pgdat->node_id)
3895 return NULL;
3896
3897 if (folio_memcg_rcu(folio) != memcg)
3898 return NULL;
3899
3900 /* file VMAs can contain anon pages from COW */
3901 if (!folio_is_file_lru(folio) && !can_swap)
3902 return NULL;
3903
3904 return folio;
3905}
3906
3907static bool suitable_to_scan(int total, int young)
3908{
3909 int n = clamp_t(int, cache_line_size() / sizeof(pte_t), 2, 8);
3910
3911 /* suitable if the average number of young PTEs per cacheline is >=1 */
3912 return young * n >= total;
3913}
3914
3915static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end,
3916 struct mm_walk *args)
3917{
3918 int i;
3919 pte_t *pte;
3920 spinlock_t *ptl;
3921 unsigned long addr;
3922 int total = 0;
3923 int young = 0;
3924 struct lru_gen_mm_walk *walk = args->private;
3925 struct mem_cgroup *memcg = lruvec_memcg(walk->lruvec);
3926 struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);
3927 int old_gen, new_gen = lru_gen_from_seq(walk->max_seq);
3928
3929 VM_WARN_ON_ONCE(pmd_leaf(*pmd));
3930
3931 ptl = pte_lockptr(args->mm, pmd);
3932 if (!spin_trylock(ptl))
3933 return false;
3934
3935 arch_enter_lazy_mmu_mode();
3936
3937 pte = pte_offset_map(pmd, start & PMD_MASK);
3938restart:
3939 for (i = pte_index(start), addr = start; addr != end; i++, addr += PAGE_SIZE) {
3940 unsigned long pfn;
3941 struct folio *folio;
3942
3943 total++;
3944 walk->mm_stats[MM_LEAF_TOTAL]++;
3945
3946 pfn = get_pte_pfn(pte[i], args->vma, addr);
3947 if (pfn == -1)
3948 continue;
3949
3950 if (!pte_young(pte[i])) {
3951 walk->mm_stats[MM_LEAF_OLD]++;
3952 continue;
3953 }
3954
3955 folio = get_pfn_folio(pfn, memcg, pgdat, walk->can_swap);
3956 if (!folio)
3957 continue;
3958
3959 if (!ptep_test_and_clear_young(args->vma, addr, pte + i))
3960 VM_WARN_ON_ONCE(true);
3961
3962 young++;
3963 walk->mm_stats[MM_LEAF_YOUNG]++;
3964
3965 if (pte_dirty(pte[i]) && !folio_test_dirty(folio) &&
3966 !(folio_test_anon(folio) && folio_test_swapbacked(folio) &&
3967 !folio_test_swapcache(folio)))
3968 folio_mark_dirty(folio);
3969
3970 old_gen = folio_update_gen(folio, new_gen);
3971 if (old_gen >= 0 && old_gen != new_gen)
3972 update_batch_size(walk, folio, old_gen, new_gen);
3973 }
3974
3975 if (i < PTRS_PER_PTE && get_next_vma(PMD_MASK, PAGE_SIZE, args, &start, &end))
3976 goto restart;
3977
3978 pte_unmap(pte);
3979
3980 arch_leave_lazy_mmu_mode();
3981 spin_unlock(ptl);
3982
3983 return suitable_to_scan(total, young);
3984}
3985
3986#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG)
3987static void walk_pmd_range_locked(pud_t *pud, unsigned long next, struct vm_area_struct *vma,
3988 struct mm_walk *args, unsigned long *bitmap, unsigned long *start)
3989{
3990 int i;
3991 pmd_t *pmd;
3992 spinlock_t *ptl;
3993 struct lru_gen_mm_walk *walk = args->private;
3994 struct mem_cgroup *memcg = lruvec_memcg(walk->lruvec);
3995 struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);
3996 int old_gen, new_gen = lru_gen_from_seq(walk->max_seq);
3997
3998 VM_WARN_ON_ONCE(pud_leaf(*pud));
3999
4000 /* try to batch at most 1+MIN_LRU_BATCH+1 entries */
4001 if (*start == -1) {
4002 *start = next;
4003 return;
4004 }
4005
4006 i = next == -1 ? 0 : pmd_index(next) - pmd_index(*start);
4007 if (i && i <= MIN_LRU_BATCH) {
4008 __set_bit(i - 1, bitmap);
4009 return;
4010 }
4011
4012 pmd = pmd_offset(pud, *start);
4013
4014 ptl = pmd_lockptr(args->mm, pmd);
4015 if (!spin_trylock(ptl))
4016 goto done;
4017
4018 arch_enter_lazy_mmu_mode();
4019
4020 do {
4021 unsigned long pfn;
4022 struct folio *folio;
4023 unsigned long addr = i ? (*start & PMD_MASK) + i * PMD_SIZE : *start;
4024
4025 pfn = get_pmd_pfn(pmd[i], vma, addr);
4026 if (pfn == -1)
4027 goto next;
4028
4029 if (!pmd_trans_huge(pmd[i])) {
4030 if (arch_has_hw_nonleaf_pmd_young() &&
4031 get_cap(LRU_GEN_NONLEAF_YOUNG))
4032 pmdp_test_and_clear_young(vma, addr, pmd + i);
4033 goto next;
4034 }
4035
4036 folio = get_pfn_folio(pfn, memcg, pgdat, walk->can_swap);
4037 if (!folio)
4038 goto next;
4039
4040 if (!pmdp_test_and_clear_young(vma, addr, pmd + i))
4041 goto next;
4042
4043 walk->mm_stats[MM_LEAF_YOUNG]++;
4044
4045 if (pmd_dirty(pmd[i]) && !folio_test_dirty(folio) &&
4046 !(folio_test_anon(folio) && folio_test_swapbacked(folio) &&
4047 !folio_test_swapcache(folio)))
4048 folio_mark_dirty(folio);
4049
4050 old_gen = folio_update_gen(folio, new_gen);
4051 if (old_gen >= 0 && old_gen != new_gen)
4052 update_batch_size(walk, folio, old_gen, new_gen);
4053next:
4054 i = i > MIN_LRU_BATCH ? 0 : find_next_bit(bitmap, MIN_LRU_BATCH, i) + 1;
4055 } while (i <= MIN_LRU_BATCH);
4056
4057 arch_leave_lazy_mmu_mode();
4058 spin_unlock(ptl);
4059done:
4060 *start = -1;
4061 bitmap_zero(bitmap, MIN_LRU_BATCH);
4062}
4063#else
4064static void walk_pmd_range_locked(pud_t *pud, unsigned long next, struct vm_area_struct *vma,
4065 struct mm_walk *args, unsigned long *bitmap, unsigned long *start)
4066{
4067}
4068#endif
4069
4070static void walk_pmd_range(pud_t *pud, unsigned long start, unsigned long end,
4071 struct mm_walk *args)
4072{
4073 int i;
4074 pmd_t *pmd;
4075 unsigned long next;
4076 unsigned long addr;
4077 struct vm_area_struct *vma;
4078 unsigned long pos = -1;
4079 struct lru_gen_mm_walk *walk = args->private;
4080 unsigned long bitmap[BITS_TO_LONGS(MIN_LRU_BATCH)] = {};
4081
4082 VM_WARN_ON_ONCE(pud_leaf(*pud));
4083
4084 /*
4085 * Finish an entire PMD in two passes: the first only reaches to PTE
4086 * tables to avoid taking the PMD lock; the second, if necessary, takes
4087 * the PMD lock to clear the accessed bit in PMD entries.
4088 */
4089 pmd = pmd_offset(pud, start & PUD_MASK);
4090restart:
4091 /* walk_pte_range() may call get_next_vma() */
4092 vma = args->vma;
4093 for (i = pmd_index(start), addr = start; addr != end; i++, addr = next) {
4094 pmd_t val = pmdp_get_lockless(pmd + i);
4095
4096 next = pmd_addr_end(addr, end);
4097
4098 if (!pmd_present(val) || is_huge_zero_pmd(val)) {
4099 walk->mm_stats[MM_LEAF_TOTAL]++;
4100 continue;
4101 }
4102
4103#ifdef CONFIG_TRANSPARENT_HUGEPAGE
4104 if (pmd_trans_huge(val)) {
4105 unsigned long pfn = pmd_pfn(val);
4106 struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);
4107
4108 walk->mm_stats[MM_LEAF_TOTAL]++;
4109
4110 if (!pmd_young(val)) {
4111 walk->mm_stats[MM_LEAF_OLD]++;
4112 continue;
4113 }
4114
4115 /* try to avoid unnecessary memory loads */
4116 if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat))
4117 continue;
4118
4119 walk_pmd_range_locked(pud, addr, vma, args, bitmap, &pos);
4120 continue;
4121 }
4122#endif
4123 walk->mm_stats[MM_NONLEAF_TOTAL]++;
4124
4125 if (arch_has_hw_nonleaf_pmd_young() &&
4126 get_cap(LRU_GEN_NONLEAF_YOUNG)) {
4127 if (!pmd_young(val))
4128 continue;
4129
4130 walk_pmd_range_locked(pud, addr, vma, args, bitmap, &pos);
4131 }
4132
4133 if (!walk->force_scan && !test_bloom_filter(walk->lruvec, walk->max_seq, pmd + i))
4134 continue;
4135
4136 walk->mm_stats[MM_NONLEAF_FOUND]++;
4137
4138 if (!walk_pte_range(&val, addr, next, args))
4139 continue;
4140
4141 walk->mm_stats[MM_NONLEAF_ADDED]++;
4142
4143 /* carry over to the next generation */
4144 update_bloom_filter(walk->lruvec, walk->max_seq + 1, pmd + i);
4145 }
4146
4147 walk_pmd_range_locked(pud, -1, vma, args, bitmap, &pos);
4148
4149 if (i < PTRS_PER_PMD && get_next_vma(PUD_MASK, PMD_SIZE, args, &start, &end))
4150 goto restart;
4151}
4152
4153static int walk_pud_range(p4d_t *p4d, unsigned long start, unsigned long end,
4154 struct mm_walk *args)
4155{
4156 int i;
4157 pud_t *pud;
4158 unsigned long addr;
4159 unsigned long next;
4160 struct lru_gen_mm_walk *walk = args->private;
4161
4162 VM_WARN_ON_ONCE(p4d_leaf(*p4d));
4163
4164 pud = pud_offset(p4d, start & P4D_MASK);
4165restart:
4166 for (i = pud_index(start), addr = start; addr != end; i++, addr = next) {
4167 pud_t val = READ_ONCE(pud[i]);
4168
4169 next = pud_addr_end(addr, end);
4170
4171 if (!pud_present(val) || WARN_ON_ONCE(pud_leaf(val)))
4172 continue;
4173
4174 walk_pmd_range(&val, addr, next, args);
4175
4176 /* a racy check to curtail the waiting time */
4177 if (wq_has_sleeper(&walk->lruvec->mm_state.wait))
4178 return 1;
4179
4180 if (need_resched() || walk->batched >= MAX_LRU_BATCH) {
4181 end = (addr | ~PUD_MASK) + 1;
4182 goto done;
4183 }
4184 }
4185
4186 if (i < PTRS_PER_PUD && get_next_vma(P4D_MASK, PUD_SIZE, args, &start, &end))
4187 goto restart;
4188
4189 end = round_up(end, P4D_SIZE);
4190done:
4191 if (!end || !args->vma)
4192 return 1;
4193
4194 walk->next_addr = max(end, args->vma->vm_start);
4195
4196 return -EAGAIN;
4197}
4198
4199static void walk_mm(struct lruvec *lruvec, struct mm_struct *mm, struct lru_gen_mm_walk *walk)
4200{
4201 static const struct mm_walk_ops mm_walk_ops = {
4202 .test_walk = should_skip_vma,
4203 .p4d_entry = walk_pud_range,
4204 };
4205
4206 int err;
4207 struct mem_cgroup *memcg = lruvec_memcg(lruvec);
4208
4209 walk->next_addr = FIRST_USER_ADDRESS;
4210
4211 do {
4212 err = -EBUSY;
4213
4214 /* folio_update_gen() requires stable folio_memcg() */
4215 if (!mem_cgroup_trylock_pages(memcg))
4216 break;
4217
4218 /* the caller might be holding the lock for write */
4219 if (mmap_read_trylock(mm)) {
4220 err = walk_page_range(mm, walk->next_addr, ULONG_MAX, &mm_walk_ops, walk);
4221
4222 mmap_read_unlock(mm);
4223 }
4224
4225 mem_cgroup_unlock_pages();
4226
4227 if (walk->batched) {
4228 spin_lock_irq(&lruvec->lru_lock);
4229 reset_batch_size(lruvec, walk);
4230 spin_unlock_irq(&lruvec->lru_lock);
4231 }
4232
4233 cond_resched();
4234 } while (err == -EAGAIN);
4235}
4236
4237static struct lru_gen_mm_walk *set_mm_walk(struct pglist_data *pgdat)
4238{
4239 struct lru_gen_mm_walk *walk = current->reclaim_state->mm_walk;
4240
4241 if (pgdat && current_is_kswapd()) {
4242 VM_WARN_ON_ONCE(walk);
4243
4244 walk = &pgdat->mm_walk;
4245 } else if (!pgdat && !walk) {
4246 VM_WARN_ON_ONCE(current_is_kswapd());
4247
4248 walk = kzalloc(sizeof(*walk), __GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN);
4249 }
4250
4251 current->reclaim_state->mm_walk = walk;
4252
4253 return walk;
4254}
4255
4256static void clear_mm_walk(void)
4257{
4258 struct lru_gen_mm_walk *walk = current->reclaim_state->mm_walk;
4259
4260 VM_WARN_ON_ONCE(walk && memchr_inv(walk->nr_pages, 0, sizeof(walk->nr_pages)));
4261 VM_WARN_ON_ONCE(walk && memchr_inv(walk->mm_stats, 0, sizeof(walk->mm_stats)));
4262
4263 current->reclaim_state->mm_walk = NULL;
4264
4265 if (!current_is_kswapd())
4266 kfree(walk);
4267}
4268
4269static bool inc_min_seq(struct lruvec *lruvec, int type, bool can_swap)
4270{
4271 int zone;
4272 int remaining = MAX_LRU_BATCH;
4273 struct lru_gen_struct *lrugen = &lruvec->lrugen;
4274 int new_gen, old_gen = lru_gen_from_seq(lrugen->min_seq[type]);
4275
4276 if (type == LRU_GEN_ANON && !can_swap)
4277 goto done;
4278
4279 /* prevent cold/hot inversion if force_scan is true */
4280 for (zone = 0; zone < MAX_NR_ZONES; zone++) {
4281 struct list_head *head = &lrugen->lists[old_gen][type][zone];
4282
4283 while (!list_empty(head)) {
4284 struct folio *folio = lru_to_folio(head);
4285
4286 VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio);
4287 VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio), folio);
4288 VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio);
4289 VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio) != zone, folio);
4290
4291 new_gen = folio_inc_gen(lruvec, folio, false);
4292 list_move_tail(&folio->lru, &lrugen->lists[new_gen][type][zone]);
4293
4294 if (!--remaining)
4295 return false;
4296 }
4297 }
4298done:
4299 reset_ctrl_pos(lruvec, type, true);
4300 WRITE_ONCE(lrugen->min_seq[type], lrugen->min_seq[type] + 1);
4301
4302 return true;
4303}
4304
4305static bool try_to_inc_min_seq(struct lruvec *lruvec, bool can_swap)
4306{
4307 int gen, type, zone;
4308 bool success = false;
4309 struct lru_gen_struct *lrugen = &lruvec->lrugen;
4310 DEFINE_MIN_SEQ(lruvec);
4311
4312 VM_WARN_ON_ONCE(!seq_is_valid(lruvec));
4313
4314 /* find the oldest populated generation */
4315 for (type = !can_swap; type < ANON_AND_FILE; type++) {
4316 while (min_seq[type] + MIN_NR_GENS <= lrugen->max_seq) {
4317 gen = lru_gen_from_seq(min_seq[type]);
4318
4319 for (zone = 0; zone < MAX_NR_ZONES; zone++) {
4320 if (!list_empty(&lrugen->lists[gen][type][zone]))
4321 goto next;
4322 }
4323
4324 min_seq[type]++;
4325 }
4326next:
4327 ;
4328 }
4329
4330 /* see the comment on lru_gen_struct */
4331 if (can_swap) {
4332 min_seq[LRU_GEN_ANON] = min(min_seq[LRU_GEN_ANON], min_seq[LRU_GEN_FILE]);
4333 min_seq[LRU_GEN_FILE] = max(min_seq[LRU_GEN_ANON], lrugen->min_seq[LRU_GEN_FILE]);
4334 }
4335
4336 for (type = !can_swap; type < ANON_AND_FILE; type++) {
4337 if (min_seq[type] == lrugen->min_seq[type])
4338 continue;
4339
4340 reset_ctrl_pos(lruvec, type, true);
4341 WRITE_ONCE(lrugen->min_seq[type], min_seq[type]);
4342 success = true;
4343 }
4344
4345 return success;
4346}
4347
4348static void inc_max_seq(struct lruvec *lruvec, bool can_swap, bool force_scan)
4349{
4350 int prev, next;
4351 int type, zone;
4352 struct lru_gen_struct *lrugen = &lruvec->lrugen;
4353
4354 spin_lock_irq(&lruvec->lru_lock);
4355
4356 VM_WARN_ON_ONCE(!seq_is_valid(lruvec));
4357
4358 for (type = ANON_AND_FILE - 1; type >= 0; type--) {
4359 if (get_nr_gens(lruvec, type) != MAX_NR_GENS)
4360 continue;
4361
4362 VM_WARN_ON_ONCE(!force_scan && (type == LRU_GEN_FILE || can_swap));
4363
4364 while (!inc_min_seq(lruvec, type, can_swap)) {
4365 spin_unlock_irq(&lruvec->lru_lock);
4366 cond_resched();
4367 spin_lock_irq(&lruvec->lru_lock);
4368 }
4369 }
4370
4371 /*
4372 * Update the active/inactive LRU sizes for compatibility. Both sides of
4373 * the current max_seq need to be covered, since max_seq+1 can overlap
4374 * with min_seq[LRU_GEN_ANON] if swapping is constrained. And if they do
4375 * overlap, cold/hot inversion happens.
4376 */
4377 prev = lru_gen_from_seq(lrugen->max_seq - 1);
4378 next = lru_gen_from_seq(lrugen->max_seq + 1);
4379
4380 for (type = 0; type < ANON_AND_FILE; type++) {
4381 for (zone = 0; zone < MAX_NR_ZONES; zone++) {
4382 enum lru_list lru = type * LRU_INACTIVE_FILE;
4383 long delta = lrugen->nr_pages[prev][type][zone] -
4384 lrugen->nr_pages[next][type][zone];
4385
4386 if (!delta)
4387 continue;
4388
4389 __update_lru_size(lruvec, lru, zone, delta);
4390 __update_lru_size(lruvec, lru + LRU_ACTIVE, zone, -delta);
4391 }
4392 }
4393
4394 for (type = 0; type < ANON_AND_FILE; type++)
4395 reset_ctrl_pos(lruvec, type, false);
4396
4397 WRITE_ONCE(lrugen->timestamps[next], jiffies);
4398 /* make sure preceding modifications appear */
4399 smp_store_release(&lrugen->max_seq, lrugen->max_seq + 1);
4400
4401 spin_unlock_irq(&lruvec->lru_lock);
4402}
4403
4404static bool try_to_inc_max_seq(struct lruvec *lruvec, unsigned long max_seq,
4405 struct scan_control *sc, bool can_swap, bool force_scan)
4406{
4407 bool success;
4408 struct lru_gen_mm_walk *walk;
4409 struct mm_struct *mm = NULL;
4410 struct lru_gen_struct *lrugen = &lruvec->lrugen;
4411
4412 VM_WARN_ON_ONCE(max_seq > READ_ONCE(lrugen->max_seq));
4413
4414 /* see the comment in iterate_mm_list() */
4415 if (max_seq <= READ_ONCE(lruvec->mm_state.seq)) {
4416 success = false;
4417 goto done;
4418 }
4419
4420 /*
4421 * If the hardware doesn't automatically set the accessed bit, fallback
4422 * to lru_gen_look_around(), which only clears the accessed bit in a
4423 * handful of PTEs. Spreading the work out over a period of time usually
4424 * is less efficient, but it avoids bursty page faults.
4425 */
4426 if (!force_scan && !(arch_has_hw_pte_young() && get_cap(LRU_GEN_MM_WALK))) {
4427 success = iterate_mm_list_nowalk(lruvec, max_seq);
4428 goto done;
4429 }
4430
4431 walk = set_mm_walk(NULL);
4432 if (!walk) {
4433 success = iterate_mm_list_nowalk(lruvec, max_seq);
4434 goto done;
4435 }
4436
4437 walk->lruvec = lruvec;
4438 walk->max_seq = max_seq;
4439 walk->can_swap = can_swap;
4440 walk->force_scan = force_scan;
4441
4442 do {
4443 success = iterate_mm_list(lruvec, walk, &mm);
4444 if (mm)
4445 walk_mm(lruvec, mm, walk);
4446
4447 cond_resched();
4448 } while (mm);
4449done:
4450 if (!success) {
4451 if (sc->priority <= DEF_PRIORITY - 2)
4452 wait_event_killable(lruvec->mm_state.wait,
4453 max_seq < READ_ONCE(lrugen->max_seq));
4454
4455 return max_seq < READ_ONCE(lrugen->max_seq);
4456 }
4457
4458 VM_WARN_ON_ONCE(max_seq != READ_ONCE(lrugen->max_seq));
4459
4460 inc_max_seq(lruvec, can_swap, force_scan);
4461 /* either this sees any waiters or they will see updated max_seq */
4462 if (wq_has_sleeper(&lruvec->mm_state.wait))
4463 wake_up_all(&lruvec->mm_state.wait);
4464
4465 return true;
4466}
4467
4468static bool should_run_aging(struct lruvec *lruvec, unsigned long max_seq, unsigned long *min_seq,
4469 struct scan_control *sc, bool can_swap, unsigned long *nr_to_scan)
4470{
4471 int gen, type, zone;
4472 unsigned long old = 0;
4473 unsigned long young = 0;
4474 unsigned long total = 0;
4475 struct lru_gen_struct *lrugen = &lruvec->lrugen;
4476 struct mem_cgroup *memcg = lruvec_memcg(lruvec);
4477
4478 for (type = !can_swap; type < ANON_AND_FILE; type++) {
4479 unsigned long seq;
4480
4481 for (seq = min_seq[type]; seq <= max_seq; seq++) {
4482 unsigned long size = 0;
4483
4484 gen = lru_gen_from_seq(seq);
4485
4486 for (zone = 0; zone < MAX_NR_ZONES; zone++)
4487 size += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L);
4488
4489 total += size;
4490 if (seq == max_seq)
4491 young += size;
4492 else if (seq + MIN_NR_GENS == max_seq)
4493 old += size;
4494 }
4495 }
4496
4497 /* try to scrape all its memory if this memcg was deleted */
4498 *nr_to_scan = mem_cgroup_online(memcg) ? (total >> sc->priority) : total;
4499
4500 /*
4501 * The aging tries to be lazy to reduce the overhead, while the eviction
4502 * stalls when the number of generations reaches MIN_NR_GENS. Hence, the
4503 * ideal number of generations is MIN_NR_GENS+1.
4504 */
4505 if (min_seq[!can_swap] + MIN_NR_GENS > max_seq)
4506 return true;
4507 if (min_seq[!can_swap] + MIN_NR_GENS < max_seq)
4508 return false;
4509
4510 /*
4511 * It's also ideal to spread pages out evenly, i.e., 1/(MIN_NR_GENS+1)
4512 * of the total number of pages for each generation. A reasonable range
4513 * for this average portion is [1/MIN_NR_GENS, 1/(MIN_NR_GENS+2)]. The
4514 * aging cares about the upper bound of hot pages, while the eviction
4515 * cares about the lower bound of cold pages.
4516 */
4517 if (young * MIN_NR_GENS > total)
4518 return true;
4519 if (old * (MIN_NR_GENS + 2) < total)
4520 return true;
4521
4522 return false;
4523}
4524
4525static bool age_lruvec(struct lruvec *lruvec, struct scan_control *sc, unsigned long min_ttl)
4526{
4527 bool need_aging;
4528 unsigned long nr_to_scan;
4529 int swappiness = get_swappiness(lruvec, sc);
4530 struct mem_cgroup *memcg = lruvec_memcg(lruvec);
4531 DEFINE_MAX_SEQ(lruvec);
4532 DEFINE_MIN_SEQ(lruvec);
4533
4534 VM_WARN_ON_ONCE(sc->memcg_low_reclaim);
4535
4536 mem_cgroup_calculate_protection(NULL, memcg);
4537
4538 if (mem_cgroup_below_min(NULL, memcg))
4539 return false;
4540
4541 need_aging = should_run_aging(lruvec, max_seq, min_seq, sc, swappiness, &nr_to_scan);
4542
4543 if (min_ttl) {
4544 int gen = lru_gen_from_seq(min_seq[LRU_GEN_FILE]);
4545 unsigned long birth = READ_ONCE(lruvec->lrugen.timestamps[gen]);
4546
4547 if (time_is_after_jiffies(birth + min_ttl))
4548 return false;
4549
4550 /* the size is likely too small to be helpful */
4551 if (!nr_to_scan && sc->priority != DEF_PRIORITY)
4552 return false;
4553 }
4554
4555 if (need_aging)
4556 try_to_inc_max_seq(lruvec, max_seq, sc, swappiness, false);
4557
4558 return true;
4559}
4560
4561/* to protect the working set of the last N jiffies */
4562static unsigned long lru_gen_min_ttl __read_mostly;
4563
4564static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc)
4565{
4566 struct mem_cgroup *memcg;
4567 bool success = false;
4568 unsigned long min_ttl = READ_ONCE(lru_gen_min_ttl);
4569
4570 VM_WARN_ON_ONCE(!current_is_kswapd());
4571
4572 sc->last_reclaimed = sc->nr_reclaimed;
4573
4574 /*
4575 * To reduce the chance of going into the aging path, which can be
4576 * costly, optimistically skip it if the flag below was cleared in the
4577 * eviction path. This improves the overall performance when multiple
4578 * memcgs are available.
4579 */
4580 if (!sc->memcgs_need_aging) {
4581 sc->memcgs_need_aging = true;
4582 return;
4583 }
4584
4585 set_mm_walk(pgdat);
4586
4587 memcg = mem_cgroup_iter(NULL, NULL, NULL);
4588 do {
4589 struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
4590
4591 if (age_lruvec(lruvec, sc, min_ttl))
4592 success = true;
4593
4594 cond_resched();
4595 } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)));
4596
4597 clear_mm_walk();
4598
4599 /* check the order to exclude compaction-induced reclaim */
4600 if (success || !min_ttl || sc->order)
4601 return;
4602
4603 /*
4604 * The main goal is to OOM kill if every generation from all memcgs is
4605 * younger than min_ttl. However, another possibility is all memcgs are
4606 * either below min or empty.
4607 */
4608 if (mutex_trylock(&oom_lock)) {
4609 struct oom_control oc = {
4610 .gfp_mask = sc->gfp_mask,
4611 };
4612
4613 out_of_memory(&oc);
4614
4615 mutex_unlock(&oom_lock);
4616 }
4617}
4618
4619/*
4620 * This function exploits spatial locality when shrink_folio_list() walks the
4621 * rmap. It scans the adjacent PTEs of a young PTE and promotes hot pages. If
4622 * the scan was done cacheline efficiently, it adds the PMD entry pointing to
4623 * the PTE table to the Bloom filter. This forms a feedback loop between the
4624 * eviction and the aging.
4625 */
4626void lru_gen_look_around(struct page_vma_mapped_walk *pvmw)
4627{
4628 int i;
4629 pte_t *pte;
4630 unsigned long start;
4631 unsigned long end;
4632 unsigned long addr;
4633 struct lru_gen_mm_walk *walk;
4634 int young = 0;
4635 unsigned long bitmap[BITS_TO_LONGS(MIN_LRU_BATCH)] = {};
4636 struct folio *folio = pfn_folio(pvmw->pfn);
4637 struct mem_cgroup *memcg = folio_memcg(folio);
4638 struct pglist_data *pgdat = folio_pgdat(folio);
4639 struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
4640 DEFINE_MAX_SEQ(lruvec);
4641 int old_gen, new_gen = lru_gen_from_seq(max_seq);
4642
4643 lockdep_assert_held(pvmw->ptl);
4644 VM_WARN_ON_ONCE_FOLIO(folio_test_lru(folio), folio);
4645
4646 if (spin_is_contended(pvmw->ptl))
4647 return;
4648
4649 /* avoid taking the LRU lock under the PTL when possible */
4650 walk = current->reclaim_state ? current->reclaim_state->mm_walk : NULL;
4651
4652 start = max(pvmw->address & PMD_MASK, pvmw->vma->vm_start);
4653 end = min(pvmw->address | ~PMD_MASK, pvmw->vma->vm_end - 1) + 1;
4654
4655 if (end - start > MIN_LRU_BATCH * PAGE_SIZE) {
4656 if (pvmw->address - start < MIN_LRU_BATCH * PAGE_SIZE / 2)
4657 end = start + MIN_LRU_BATCH * PAGE_SIZE;
4658 else if (end - pvmw->address < MIN_LRU_BATCH * PAGE_SIZE / 2)
4659 start = end - MIN_LRU_BATCH * PAGE_SIZE;
4660 else {
4661 start = pvmw->address - MIN_LRU_BATCH * PAGE_SIZE / 2;
4662 end = pvmw->address + MIN_LRU_BATCH * PAGE_SIZE / 2;
4663 }
4664 }
4665
4666 pte = pvmw->pte - (pvmw->address - start) / PAGE_SIZE;
4667
4668 rcu_read_lock();
4669 arch_enter_lazy_mmu_mode();
4670
4671 for (i = 0, addr = start; addr != end; i++, addr += PAGE_SIZE) {
4672 unsigned long pfn;
4673
4674 pfn = get_pte_pfn(pte[i], pvmw->vma, addr);
4675 if (pfn == -1)
4676 continue;
4677
4678 if (!pte_young(pte[i]))
4679 continue;
4680
4681 folio = get_pfn_folio(pfn, memcg, pgdat, !walk || walk->can_swap);
4682 if (!folio)
4683 continue;
4684
4685 if (!ptep_test_and_clear_young(pvmw->vma, addr, pte + i))
4686 VM_WARN_ON_ONCE(true);
4687
4688 young++;
4689
4690 if (pte_dirty(pte[i]) && !folio_test_dirty(folio) &&
4691 !(folio_test_anon(folio) && folio_test_swapbacked(folio) &&
4692 !folio_test_swapcache(folio)))
4693 folio_mark_dirty(folio);
4694
4695 old_gen = folio_lru_gen(folio);
4696 if (old_gen < 0)
4697 folio_set_referenced(folio);
4698 else if (old_gen != new_gen)
4699 __set_bit(i, bitmap);
4700 }
4701
4702 arch_leave_lazy_mmu_mode();
4703 rcu_read_unlock();
4704
4705 /* feedback from rmap walkers to page table walkers */
4706 if (suitable_to_scan(i, young))
4707 update_bloom_filter(lruvec, max_seq, pvmw->pmd);
4708
4709 if (!walk && bitmap_weight(bitmap, MIN_LRU_BATCH) < PAGEVEC_SIZE) {
4710 for_each_set_bit(i, bitmap, MIN_LRU_BATCH) {
4711 folio = pfn_folio(pte_pfn(pte[i]));
4712 folio_activate(folio);
4713 }
4714 return;
4715 }
4716
4717 /* folio_update_gen() requires stable folio_memcg() */
4718 if (!mem_cgroup_trylock_pages(memcg))
4719 return;
4720
4721 if (!walk) {
4722 spin_lock_irq(&lruvec->lru_lock);
4723 new_gen = lru_gen_from_seq(lruvec->lrugen.max_seq);
4724 }
4725
4726 for_each_set_bit(i, bitmap, MIN_LRU_BATCH) {
4727 folio = pfn_folio(pte_pfn(pte[i]));
4728 if (folio_memcg_rcu(folio) != memcg)
4729 continue;
4730
4731 old_gen = folio_update_gen(folio, new_gen);
4732 if (old_gen < 0 || old_gen == new_gen)
4733 continue;
4734
4735 if (walk)
4736 update_batch_size(walk, folio, old_gen, new_gen);
4737 else
4738 lru_gen_update_size(lruvec, folio, old_gen, new_gen);
4739 }
4740
4741 if (!walk)
4742 spin_unlock_irq(&lruvec->lru_lock);
4743
4744 mem_cgroup_unlock_pages();
4745}
4746
4747/******************************************************************************
4748 * the eviction
4749 ******************************************************************************/
4750
4751static bool sort_folio(struct lruvec *lruvec, struct folio *folio, int tier_idx)
4752{
4753 bool success;
4754 int gen = folio_lru_gen(folio);
4755 int type = folio_is_file_lru(folio);
4756 int zone = folio_zonenum(folio);
4757 int delta = folio_nr_pages(folio);
4758 int refs = folio_lru_refs(folio);
4759 int tier = lru_tier_from_refs(refs);
4760 struct lru_gen_struct *lrugen = &lruvec->lrugen;
4761
4762 VM_WARN_ON_ONCE_FOLIO(gen >= MAX_NR_GENS, folio);
4763
4764 /* unevictable */
4765 if (!folio_evictable(folio)) {
4766 success = lru_gen_del_folio(lruvec, folio, true);
4767 VM_WARN_ON_ONCE_FOLIO(!success, folio);
4768 folio_set_unevictable(folio);
4769 lruvec_add_folio(lruvec, folio);
4770 __count_vm_events(UNEVICTABLE_PGCULLED, delta);
4771 return true;
4772 }
4773
4774 /* dirty lazyfree */
4775 if (type == LRU_GEN_FILE && folio_test_anon(folio) && folio_test_dirty(folio)) {
4776 success = lru_gen_del_folio(lruvec, folio, true);
4777 VM_WARN_ON_ONCE_FOLIO(!success, folio);
4778 folio_set_swapbacked(folio);
4779 lruvec_add_folio_tail(lruvec, folio);
4780 return true;
4781 }
4782
4783 /* promoted */
4784 if (gen != lru_gen_from_seq(lrugen->min_seq[type])) {
4785 list_move(&folio->lru, &lrugen->lists[gen][type][zone]);
4786 return true;
4787 }
4788
4789 /* protected */
4790 if (tier > tier_idx) {
4791 int hist = lru_hist_from_seq(lrugen->min_seq[type]);
4792
4793 gen = folio_inc_gen(lruvec, folio, false);
4794 list_move_tail(&folio->lru, &lrugen->lists[gen][type][zone]);
4795
4796 WRITE_ONCE(lrugen->protected[hist][type][tier - 1],
4797 lrugen->protected[hist][type][tier - 1] + delta);
4798 __mod_lruvec_state(lruvec, WORKINGSET_ACTIVATE_BASE + type, delta);
4799 return true;
4800 }
4801
4802 /* waiting for writeback */
4803 if (folio_test_locked(folio) || folio_test_writeback(folio) ||
4804 (type == LRU_GEN_FILE && folio_test_dirty(folio))) {
4805 gen = folio_inc_gen(lruvec, folio, true);
4806 list_move(&folio->lru, &lrugen->lists[gen][type][zone]);
4807 return true;
4808 }
4809
4810 return false;
4811}
4812
4813static bool isolate_folio(struct lruvec *lruvec, struct folio *folio, struct scan_control *sc)
4814{
4815 bool success;
4816
4817 /* unmapping inhibited */
4818 if (!sc->may_unmap && folio_mapped(folio))
4819 return false;
4820
4821 /* swapping inhibited */
4822 if (!(sc->may_writepage && (sc->gfp_mask & __GFP_IO)) &&
4823 (folio_test_dirty(folio) ||
4824 (folio_test_anon(folio) && !folio_test_swapcache(folio))))
4825 return false;
4826
4827 /* raced with release_pages() */
4828 if (!folio_try_get(folio))
4829 return false;
4830
4831 /* raced with another isolation */
4832 if (!folio_test_clear_lru(folio)) {
4833 folio_put(folio);
4834 return false;
4835 }
4836
4837 /* see the comment on MAX_NR_TIERS */
4838 if (!folio_test_referenced(folio))
4839 set_mask_bits(&folio->flags, LRU_REFS_MASK | LRU_REFS_FLAGS, 0);
4840
4841 /* for shrink_folio_list() */
4842 folio_clear_reclaim(folio);
4843 folio_clear_referenced(folio);
4844
4845 success = lru_gen_del_folio(lruvec, folio, true);
4846 VM_WARN_ON_ONCE_FOLIO(!success, folio);
4847
4848 return true;
4849}
4850
4851static int scan_folios(struct lruvec *lruvec, struct scan_control *sc,
4852 int type, int tier, struct list_head *list)
4853{
4854 int gen, zone;
4855 enum vm_event_item item;
4856 int sorted = 0;
4857 int scanned = 0;
4858 int isolated = 0;
4859 int remaining = MAX_LRU_BATCH;
4860 struct lru_gen_struct *lrugen = &lruvec->lrugen;
4861 struct mem_cgroup *memcg = lruvec_memcg(lruvec);
4862
4863 VM_WARN_ON_ONCE(!list_empty(list));
4864
4865 if (get_nr_gens(lruvec, type) == MIN_NR_GENS)
4866 return 0;
4867
4868 gen = lru_gen_from_seq(lrugen->min_seq[type]);
4869
4870 for (zone = sc->reclaim_idx; zone >= 0; zone--) {
4871 LIST_HEAD(moved);
4872 int skipped = 0;
4873 struct list_head *head = &lrugen->lists[gen][type][zone];
4874
4875 while (!list_empty(head)) {
4876 struct folio *folio = lru_to_folio(head);
4877 int delta = folio_nr_pages(folio);
4878
4879 VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio);
4880 VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio), folio);
4881 VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio);
4882 VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio) != zone, folio);
4883
4884 scanned += delta;
4885
4886 if (sort_folio(lruvec, folio, tier))
4887 sorted += delta;
4888 else if (isolate_folio(lruvec, folio, sc)) {
4889 list_add(&folio->lru, list);
4890 isolated += delta;
4891 } else {
4892 list_move(&folio->lru, &moved);
4893 skipped += delta;
4894 }
4895
4896 if (!--remaining || max(isolated, skipped) >= MIN_LRU_BATCH)
4897 break;
4898 }
4899
4900 if (skipped) {
4901 list_splice(&moved, head);
4902 __count_zid_vm_events(PGSCAN_SKIP, zone, skipped);
4903 }
4904
4905 if (!remaining || isolated >= MIN_LRU_BATCH)
4906 break;
4907 }
4908
4909 item = PGSCAN_KSWAPD + reclaimer_offset();
4910 if (!cgroup_reclaim(sc)) {
4911 __count_vm_events(item, isolated);
4912 __count_vm_events(PGREFILL, sorted);
4913 }
4914 __count_memcg_events(memcg, item, isolated);
4915 __count_memcg_events(memcg, PGREFILL, sorted);
4916 __count_vm_events(PGSCAN_ANON + type, isolated);
4917
4918 /*
4919 * There might not be eligible pages due to reclaim_idx, may_unmap and
4920 * may_writepage. Check the remaining to prevent livelock if it's not
4921 * making progress.
4922 */
4923 return isolated || !remaining ? scanned : 0;
4924}
4925
4926static int get_tier_idx(struct lruvec *lruvec, int type)
4927{
4928 int tier;
4929 struct ctrl_pos sp, pv;
4930
4931 /*
4932 * To leave a margin for fluctuations, use a larger gain factor (1:2).
4933 * This value is chosen because any other tier would have at least twice
4934 * as many refaults as the first tier.
4935 */
4936 read_ctrl_pos(lruvec, type, 0, 1, &sp);
4937 for (tier = 1; tier < MAX_NR_TIERS; tier++) {
4938 read_ctrl_pos(lruvec, type, tier, 2, &pv);
4939 if (!positive_ctrl_err(&sp, &pv))
4940 break;
4941 }
4942
4943 return tier - 1;
4944}
4945
4946static int get_type_to_scan(struct lruvec *lruvec, int swappiness, int *tier_idx)
4947{
4948 int type, tier;
4949 struct ctrl_pos sp, pv;
4950 int gain[ANON_AND_FILE] = { swappiness, 200 - swappiness };
4951
4952 /*
4953 * Compare the first tier of anon with that of file to determine which
4954 * type to scan. Also need to compare other tiers of the selected type
4955 * with the first tier of the other type to determine the last tier (of
4956 * the selected type) to evict.
4957 */
4958 read_ctrl_pos(lruvec, LRU_GEN_ANON, 0, gain[LRU_GEN_ANON], &sp);
4959 read_ctrl_pos(lruvec, LRU_GEN_FILE, 0, gain[LRU_GEN_FILE], &pv);
4960 type = positive_ctrl_err(&sp, &pv);
4961
4962 read_ctrl_pos(lruvec, !type, 0, gain[!type], &sp);
4963 for (tier = 1; tier < MAX_NR_TIERS; tier++) {
4964 read_ctrl_pos(lruvec, type, tier, gain[type], &pv);
4965 if (!positive_ctrl_err(&sp, &pv))
4966 break;
4967 }
4968
4969 *tier_idx = tier - 1;
4970
4971 return type;
4972}
4973
4974static int isolate_folios(struct lruvec *lruvec, struct scan_control *sc, int swappiness,
4975 int *type_scanned, struct list_head *list)
4976{
4977 int i;
4978 int type;
4979 int scanned;
4980 int tier = -1;
4981 DEFINE_MIN_SEQ(lruvec);
4982
4983 /*
4984 * Try to make the obvious choice first. When anon and file are both
4985 * available from the same generation, interpret swappiness 1 as file
4986 * first and 200 as anon first.
4987 */
4988 if (!swappiness)
4989 type = LRU_GEN_FILE;
4990 else if (min_seq[LRU_GEN_ANON] < min_seq[LRU_GEN_FILE])
4991 type = LRU_GEN_ANON;
4992 else if (swappiness == 1)
4993 type = LRU_GEN_FILE;
4994 else if (swappiness == 200)
4995 type = LRU_GEN_ANON;
4996 else
4997 type = get_type_to_scan(lruvec, swappiness, &tier);
4998
4999 for (i = !swappiness; i < ANON_AND_FILE; i++) {
5000 if (tier < 0)
5001 tier = get_tier_idx(lruvec, type);
5002
5003 scanned = scan_folios(lruvec, sc, type, tier, list);
5004 if (scanned)
5005 break;
5006
5007 type = !type;
5008 tier = -1;
5009 }
5010
5011 *type_scanned = type;
5012
5013 return scanned;
5014}
5015
5016static int evict_folios(struct lruvec *lruvec, struct scan_control *sc, int swappiness,
5017 bool *need_swapping)
5018{
5019 int type;
5020 int scanned;
5021 int reclaimed;
5022 LIST_HEAD(list);
5023 LIST_HEAD(clean);
5024 struct folio *folio;
5025 struct folio *next;
5026 enum vm_event_item item;
5027 struct reclaim_stat stat;
5028 struct lru_gen_mm_walk *walk;
5029 bool skip_retry = false;
5030 struct mem_cgroup *memcg = lruvec_memcg(lruvec);
5031 struct pglist_data *pgdat = lruvec_pgdat(lruvec);
5032
5033 spin_lock_irq(&lruvec->lru_lock);
5034
5035 scanned = isolate_folios(lruvec, sc, swappiness, &type, &list);
5036
5037 scanned += try_to_inc_min_seq(lruvec, swappiness);
5038
5039 if (get_nr_gens(lruvec, !swappiness) == MIN_NR_GENS)
5040 scanned = 0;
5041
5042 spin_unlock_irq(&lruvec->lru_lock);
5043
5044 if (list_empty(&list))
5045 return scanned;
5046retry:
5047 reclaimed = shrink_folio_list(&list, pgdat, sc, &stat, false);
5048 sc->nr_reclaimed += reclaimed;
5049
5050 list_for_each_entry_safe_reverse(folio, next, &list, lru) {
5051 if (!folio_evictable(folio)) {
5052 list_del(&folio->lru);
5053 folio_putback_lru(folio);
5054 continue;
5055 }
5056
5057 if (folio_test_reclaim(folio) &&
5058 (folio_test_dirty(folio) || folio_test_writeback(folio))) {
5059 /* restore LRU_REFS_FLAGS cleared by isolate_folio() */
5060 if (folio_test_workingset(folio))
5061 folio_set_referenced(folio);
5062 continue;
5063 }
5064
5065 if (skip_retry || folio_test_active(folio) || folio_test_referenced(folio) ||
5066 folio_mapped(folio) || folio_test_locked(folio) ||
5067 folio_test_dirty(folio) || folio_test_writeback(folio)) {
5068 /* don't add rejected folios to the oldest generation */
5069 set_mask_bits(&folio->flags, LRU_REFS_MASK | LRU_REFS_FLAGS,
5070 BIT(PG_active));
5071 continue;
5072 }
5073
5074 /* retry folios that may have missed folio_rotate_reclaimable() */
5075 list_move(&folio->lru, &clean);
5076 sc->nr_scanned -= folio_nr_pages(folio);
5077 }
5078
5079 spin_lock_irq(&lruvec->lru_lock);
5080
5081 move_folios_to_lru(lruvec, &list);
5082
5083 walk = current->reclaim_state->mm_walk;
5084 if (walk && walk->batched)
5085 reset_batch_size(lruvec, walk);
5086
5087 item = PGSTEAL_KSWAPD + reclaimer_offset();
5088 if (!cgroup_reclaim(sc))
5089 __count_vm_events(item, reclaimed);
5090 __count_memcg_events(memcg, item, reclaimed);
5091 __count_vm_events(PGSTEAL_ANON + type, reclaimed);
5092
5093 spin_unlock_irq(&lruvec->lru_lock);
5094
5095 mem_cgroup_uncharge_list(&list);
5096 free_unref_page_list(&list);
5097
5098 INIT_LIST_HEAD(&list);
5099 list_splice_init(&clean, &list);
5100
5101 if (!list_empty(&list)) {
5102 skip_retry = true;
5103 goto retry;
5104 }
5105
5106 if (need_swapping && type == LRU_GEN_ANON)
5107 *need_swapping = true;
5108
5109 return scanned;
5110}
5111
5112/*
5113 * For future optimizations:
5114 * 1. Defer try_to_inc_max_seq() to workqueues to reduce latency for memcg
5115 * reclaim.
5116 */
5117static unsigned long get_nr_to_scan(struct lruvec *lruvec, struct scan_control *sc,
5118 bool can_swap, bool *need_aging)
5119{
5120 unsigned long nr_to_scan;
5121 struct mem_cgroup *memcg = lruvec_memcg(lruvec);
5122 DEFINE_MAX_SEQ(lruvec);
5123 DEFINE_MIN_SEQ(lruvec);
5124
5125 if (mem_cgroup_below_min(sc->target_mem_cgroup, memcg) ||
5126 (mem_cgroup_below_low(sc->target_mem_cgroup, memcg) &&
5127 !sc->memcg_low_reclaim))
5128 return 0;
5129
5130 *need_aging = should_run_aging(lruvec, max_seq, min_seq, sc, can_swap, &nr_to_scan);
5131 if (!*need_aging)
5132 return nr_to_scan;
5133
5134 /* skip the aging path at the default priority */
5135 if (sc->priority == DEF_PRIORITY)
5136 goto done;
5137
5138 /* leave the work to lru_gen_age_node() */
5139 if (current_is_kswapd())
5140 return 0;
5141
5142 if (try_to_inc_max_seq(lruvec, max_seq, sc, can_swap, false))
5143 return nr_to_scan;
5144done:
5145 return min_seq[!can_swap] + MIN_NR_GENS <= max_seq ? nr_to_scan : 0;
5146}
5147
5148static bool should_abort_scan(struct lruvec *lruvec, unsigned long seq,
5149 struct scan_control *sc, bool need_swapping)
5150{
5151 int i;
5152 DEFINE_MAX_SEQ(lruvec);
5153
5154 if (!current_is_kswapd()) {
5155 /* age each memcg at most once to ensure fairness */
5156 if (max_seq - seq > 1)
5157 return true;
5158
5159 /* over-swapping can increase allocation latency */
5160 if (sc->nr_reclaimed >= sc->nr_to_reclaim && need_swapping)
5161 return true;
5162
5163 /* give this thread a chance to exit and free its memory */
5164 if (fatal_signal_pending(current)) {
5165 sc->nr_reclaimed += MIN_LRU_BATCH;
5166 return true;
5167 }
5168
5169 if (cgroup_reclaim(sc))
5170 return false;
5171 } else if (sc->nr_reclaimed - sc->last_reclaimed < sc->nr_to_reclaim)
5172 return false;
5173
5174 /* keep scanning at low priorities to ensure fairness */
5175 if (sc->priority > DEF_PRIORITY - 2)
5176 return false;
5177
5178 /*
5179 * A minimum amount of work was done under global memory pressure. For
5180 * kswapd, it may be overshooting. For direct reclaim, the allocation
5181 * may succeed if all suitable zones are somewhat safe. In either case,
5182 * it's better to stop now, and restart later if necessary.
5183 */
5184 for (i = 0; i <= sc->reclaim_idx; i++) {
5185 unsigned long wmark;
5186 struct zone *zone = lruvec_pgdat(lruvec)->node_zones + i;
5187
5188 if (!managed_zone(zone))
5189 continue;
5190
5191 wmark = current_is_kswapd() ? high_wmark_pages(zone) : low_wmark_pages(zone);
5192 if (wmark > zone_page_state(zone, NR_FREE_PAGES))
5193 return false;
5194 }
5195
5196 sc->nr_reclaimed += MIN_LRU_BATCH;
5197
5198 return true;
5199}
5200
5201static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
5202{
5203 struct blk_plug plug;
5204 bool need_aging = false;
5205 bool need_swapping = false;
5206 unsigned long scanned = 0;
5207 unsigned long reclaimed = sc->nr_reclaimed;
5208 DEFINE_MAX_SEQ(lruvec);
5209
5210 lru_add_drain();
5211
5212 blk_start_plug(&plug);
5213
5214 set_mm_walk(lruvec_pgdat(lruvec));
5215
5216 while (true) {
5217 int delta;
5218 int swappiness;
5219 unsigned long nr_to_scan;
5220
5221 if (sc->may_swap)
5222 swappiness = get_swappiness(lruvec, sc);
5223 else if (!cgroup_reclaim(sc) && get_swappiness(lruvec, sc))
5224 swappiness = 1;
5225 else
5226 swappiness = 0;
5227
5228 nr_to_scan = get_nr_to_scan(lruvec, sc, swappiness, &need_aging);
5229 if (!nr_to_scan)
5230 goto done;
5231
5232 delta = evict_folios(lruvec, sc, swappiness, &need_swapping);
5233 if (!delta)
5234 goto done;
5235
5236 scanned += delta;
5237 if (scanned >= nr_to_scan)
5238 break;
5239
5240 if (should_abort_scan(lruvec, max_seq, sc, need_swapping))
5241 break;
5242
5243 cond_resched();
5244 }
5245
5246 /* see the comment in lru_gen_age_node() */
5247 if (sc->nr_reclaimed - reclaimed >= MIN_LRU_BATCH && !need_aging)
5248 sc->memcgs_need_aging = false;
5249done:
5250 clear_mm_walk();
5251
5252 blk_finish_plug(&plug);
5253}
5254
5255/******************************************************************************
5256 * state change
5257 ******************************************************************************/
5258
5259static bool __maybe_unused state_is_valid(struct lruvec *lruvec)
5260{
5261 struct lru_gen_struct *lrugen = &lruvec->lrugen;
5262
5263 if (lrugen->enabled) {
5264 enum lru_list lru;
5265
5266 for_each_evictable_lru(lru) {
5267 if (!list_empty(&lruvec->lists[lru]))
5268 return false;
5269 }
5270 } else {
5271 int gen, type, zone;
5272
5273 for_each_gen_type_zone(gen, type, zone) {
5274 if (!list_empty(&lrugen->lists[gen][type][zone]))
5275 return false;
5276 }
5277 }
5278
5279 return true;
5280}
5281
5282static bool fill_evictable(struct lruvec *lruvec)
5283{
5284 enum lru_list lru;
5285 int remaining = MAX_LRU_BATCH;
5286
5287 for_each_evictable_lru(lru) {
5288 int type = is_file_lru(lru);
5289 bool active = is_active_lru(lru);
5290 struct list_head *head = &lruvec->lists[lru];
5291
5292 while (!list_empty(head)) {
5293 bool success;
5294 struct folio *folio = lru_to_folio(head);
5295
5296 VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio);
5297 VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio) != active, folio);
5298 VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio);
5299 VM_WARN_ON_ONCE_FOLIO(folio_lru_gen(folio) != -1, folio);
5300
5301 lruvec_del_folio(lruvec, folio);
5302 success = lru_gen_add_folio(lruvec, folio, false);
5303 VM_WARN_ON_ONCE(!success);
5304
5305 if (!--remaining)
5306 return false;
5307 }
5308 }
5309
5310 return true;
5311}
5312
5313static bool drain_evictable(struct lruvec *lruvec)
5314{
5315 int gen, type, zone;
5316 int remaining = MAX_LRU_BATCH;
5317
5318 for_each_gen_type_zone(gen, type, zone) {
5319 struct list_head *head = &lruvec->lrugen.lists[gen][type][zone];
5320
5321 while (!list_empty(head)) {
5322 bool success;
5323 struct folio *folio = lru_to_folio(head);
5324
5325 VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio);
5326 VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio), folio);
5327 VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio);
5328 VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio) != zone, folio);
5329
5330 success = lru_gen_del_folio(lruvec, folio, false);
5331 VM_WARN_ON_ONCE(!success);
5332 lruvec_add_folio(lruvec, folio);
5333
5334 if (!--remaining)
5335 return false;
5336 }
5337 }
5338
5339 return true;
5340}
5341
5342static void lru_gen_change_state(bool enabled)
5343{
5344 static DEFINE_MUTEX(state_mutex);
5345
5346 struct mem_cgroup *memcg;
5347
5348 cgroup_lock();
5349 cpus_read_lock();
5350 get_online_mems();
5351 mutex_lock(&state_mutex);
5352
5353 if (enabled == lru_gen_enabled())
5354 goto unlock;
5355
5356 if (enabled)
5357 static_branch_enable_cpuslocked(&lru_gen_caps[LRU_GEN_CORE]);
5358 else
5359 static_branch_disable_cpuslocked(&lru_gen_caps[LRU_GEN_CORE]);
5360
5361 memcg = mem_cgroup_iter(NULL, NULL, NULL);
5362 do {
5363 int nid;
5364
5365 for_each_node(nid) {
5366 struct lruvec *lruvec = get_lruvec(memcg, nid);
5367
5368 spin_lock_irq(&lruvec->lru_lock);
5369
5370 VM_WARN_ON_ONCE(!seq_is_valid(lruvec));
5371 VM_WARN_ON_ONCE(!state_is_valid(lruvec));
5372
5373 lruvec->lrugen.enabled = enabled;
5374
5375 while (!(enabled ? fill_evictable(lruvec) : drain_evictable(lruvec))) {
5376 spin_unlock_irq(&lruvec->lru_lock);
5377 cond_resched();
5378 spin_lock_irq(&lruvec->lru_lock);
5379 }
5380
5381 spin_unlock_irq(&lruvec->lru_lock);
5382 }
5383
5384 cond_resched();
5385 } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)));
5386unlock:
5387 mutex_unlock(&state_mutex);
5388 put_online_mems();
5389 cpus_read_unlock();
5390 cgroup_unlock();
5391}
5392
5393/******************************************************************************
5394 * sysfs interface
5395 ******************************************************************************/
5396
5397static ssize_t show_min_ttl(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
5398{
5399 return sprintf(buf, "%u\n", jiffies_to_msecs(READ_ONCE(lru_gen_min_ttl)));
5400}
5401
5402/* see Documentation/admin-guide/mm/multigen_lru.rst for details */
5403static ssize_t store_min_ttl(struct kobject *kobj, struct kobj_attribute *attr,
5404 const char *buf, size_t len)
5405{
5406 unsigned int msecs;
5407
5408 if (kstrtouint(buf, 0, &msecs))
5409 return -EINVAL;
5410
5411 WRITE_ONCE(lru_gen_min_ttl, msecs_to_jiffies(msecs));
5412
5413 return len;
5414}
5415
5416static struct kobj_attribute lru_gen_min_ttl_attr = __ATTR(
5417 min_ttl_ms, 0644, show_min_ttl, store_min_ttl
5418);
5419
5420static ssize_t show_enabled(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
5421{
5422 unsigned int caps = 0;
5423
5424 if (get_cap(LRU_GEN_CORE))
5425 caps |= BIT(LRU_GEN_CORE);
5426
5427 if (arch_has_hw_pte_young() && get_cap(LRU_GEN_MM_WALK))
5428 caps |= BIT(LRU_GEN_MM_WALK);
5429
5430 if (arch_has_hw_nonleaf_pmd_young() && get_cap(LRU_GEN_NONLEAF_YOUNG))
5431 caps |= BIT(LRU_GEN_NONLEAF_YOUNG);
5432
5433 return sysfs_emit(buf, "0x%04x\n", caps);
5434}
5435
5436/* see Documentation/admin-guide/mm/multigen_lru.rst for details */
5437static ssize_t store_enabled(struct kobject *kobj, struct kobj_attribute *attr,
5438 const char *buf, size_t len)
5439{
5440 int i;
5441 unsigned int caps;
5442
5443 if (tolower(*buf) == 'n')
5444 caps = 0;
5445 else if (tolower(*buf) == 'y')
5446 caps = -1;
5447 else if (kstrtouint(buf, 0, &caps))
5448 return -EINVAL;
5449
5450 for (i = 0; i < NR_LRU_GEN_CAPS; i++) {
5451 bool enabled = caps & BIT(i);
5452
5453 if (i == LRU_GEN_CORE)
5454 lru_gen_change_state(enabled);
5455 else if (enabled)
5456 static_branch_enable(&lru_gen_caps[i]);
5457 else
5458 static_branch_disable(&lru_gen_caps[i]);
5459 }
5460
5461 return len;
5462}
5463
5464static struct kobj_attribute lru_gen_enabled_attr = __ATTR(
5465 enabled, 0644, show_enabled, store_enabled
5466);
5467
5468static struct attribute *lru_gen_attrs[] = {
5469 &lru_gen_min_ttl_attr.attr,
5470 &lru_gen_enabled_attr.attr,
5471 NULL
5472};
5473
5474static struct attribute_group lru_gen_attr_group = {
5475 .name = "lru_gen",
5476 .attrs = lru_gen_attrs,
5477};
5478
5479/******************************************************************************
5480 * debugfs interface
5481 ******************************************************************************/
5482
5483static void *lru_gen_seq_start(struct seq_file *m, loff_t *pos)
5484{
5485 struct mem_cgroup *memcg;
5486 loff_t nr_to_skip = *pos;
5487
5488 m->private = kvmalloc(PATH_MAX, GFP_KERNEL);
5489 if (!m->private)
5490 return ERR_PTR(-ENOMEM);
5491
5492 memcg = mem_cgroup_iter(NULL, NULL, NULL);
5493 do {
5494 int nid;
5495
5496 for_each_node_state(nid, N_MEMORY) {
5497 if (!nr_to_skip--)
5498 return get_lruvec(memcg, nid);
5499 }
5500 } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)));
5501
5502 return NULL;
5503}
5504
5505static void lru_gen_seq_stop(struct seq_file *m, void *v)
5506{
5507 if (!IS_ERR_OR_NULL(v))
5508 mem_cgroup_iter_break(NULL, lruvec_memcg(v));
5509
5510 kvfree(m->private);
5511 m->private = NULL;
5512}
5513
5514static void *lru_gen_seq_next(struct seq_file *m, void *v, loff_t *pos)
5515{
5516 int nid = lruvec_pgdat(v)->node_id;
5517 struct mem_cgroup *memcg = lruvec_memcg(v);
5518
5519 ++*pos;
5520
5521 nid = next_memory_node(nid);
5522 if (nid == MAX_NUMNODES) {
5523 memcg = mem_cgroup_iter(NULL, memcg, NULL);
5524 if (!memcg)
5525 return NULL;
5526
5527 nid = first_memory_node;
5528 }
5529
5530 return get_lruvec(memcg, nid);
5531}
5532
5533static void lru_gen_seq_show_full(struct seq_file *m, struct lruvec *lruvec,
5534 unsigned long max_seq, unsigned long *min_seq,
5535 unsigned long seq)
5536{
5537 int i;
5538 int type, tier;
5539 int hist = lru_hist_from_seq(seq);
5540 struct lru_gen_struct *lrugen = &lruvec->lrugen;
5541
5542 for (tier = 0; tier < MAX_NR_TIERS; tier++) {
5543 seq_printf(m, " %10d", tier);
5544 for (type = 0; type < ANON_AND_FILE; type++) {
5545 const char *s = " ";
5546 unsigned long n[3] = {};
5547
5548 if (seq == max_seq) {
5549 s = "RT ";
5550 n[0] = READ_ONCE(lrugen->avg_refaulted[type][tier]);
5551 n[1] = READ_ONCE(lrugen->avg_total[type][tier]);
5552 } else if (seq == min_seq[type] || NR_HIST_GENS > 1) {
5553 s = "rep";
5554 n[0] = atomic_long_read(&lrugen->refaulted[hist][type][tier]);
5555 n[1] = atomic_long_read(&lrugen->evicted[hist][type][tier]);
5556 if (tier)
5557 n[2] = READ_ONCE(lrugen->protected[hist][type][tier - 1]);
5558 }
5559
5560 for (i = 0; i < 3; i++)
5561 seq_printf(m, " %10lu%c", n[i], s[i]);
5562 }
5563 seq_putc(m, '\n');
5564 }
5565
5566 seq_puts(m, " ");
5567 for (i = 0; i < NR_MM_STATS; i++) {
5568 const char *s = " ";
5569 unsigned long n = 0;
5570
5571 if (seq == max_seq && NR_HIST_GENS == 1) {
5572 s = "LOYNFA";
5573 n = READ_ONCE(lruvec->mm_state.stats[hist][i]);
5574 } else if (seq != max_seq && NR_HIST_GENS > 1) {
5575 s = "loynfa";
5576 n = READ_ONCE(lruvec->mm_state.stats[hist][i]);
5577 }
5578
5579 seq_printf(m, " %10lu%c", n, s[i]);
5580 }
5581 seq_putc(m, '\n');
5582}
5583
5584/* see Documentation/admin-guide/mm/multigen_lru.rst for details */
5585static int lru_gen_seq_show(struct seq_file *m, void *v)
5586{
5587 unsigned long seq;
5588 bool full = !debugfs_real_fops(m->file)->write;
5589 struct lruvec *lruvec = v;
5590 struct lru_gen_struct *lrugen = &lruvec->lrugen;
5591 int nid = lruvec_pgdat(lruvec)->node_id;
5592 struct mem_cgroup *memcg = lruvec_memcg(lruvec);
5593 DEFINE_MAX_SEQ(lruvec);
5594 DEFINE_MIN_SEQ(lruvec);
5595
5596 if (nid == first_memory_node) {
5597 const char *path = memcg ? m->private : "";
5598
5599#ifdef CONFIG_MEMCG
5600 if (memcg)
5601 cgroup_path(memcg->css.cgroup, m->private, PATH_MAX);
5602#endif
5603 seq_printf(m, "memcg %5hu %s\n", mem_cgroup_id(memcg), path);
5604 }
5605
5606 seq_printf(m, " node %5d\n", nid);
5607
5608 if (!full)
5609 seq = min_seq[LRU_GEN_ANON];
5610 else if (max_seq >= MAX_NR_GENS)
5611 seq = max_seq - MAX_NR_GENS + 1;
5612 else
5613 seq = 0;
5614
5615 for (; seq <= max_seq; seq++) {
5616 int type, zone;
5617 int gen = lru_gen_from_seq(seq);
5618 unsigned long birth = READ_ONCE(lruvec->lrugen.timestamps[gen]);
5619
5620 seq_printf(m, " %10lu %10u", seq, jiffies_to_msecs(jiffies - birth));
5621
5622 for (type = 0; type < ANON_AND_FILE; type++) {
5623 unsigned long size = 0;
5624 char mark = full && seq < min_seq[type] ? 'x' : ' ';
5625
5626 for (zone = 0; zone < MAX_NR_ZONES; zone++)
5627 size += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L);
5628
5629 seq_printf(m, " %10lu%c", size, mark);
5630 }
5631
5632 seq_putc(m, '\n');
5633
5634 if (full)
5635 lru_gen_seq_show_full(m, lruvec, max_seq, min_seq, seq);
5636 }
5637
5638 return 0;
5639}
5640
5641static const struct seq_operations lru_gen_seq_ops = {
5642 .start = lru_gen_seq_start,
5643 .stop = lru_gen_seq_stop,
5644 .next = lru_gen_seq_next,
5645 .show = lru_gen_seq_show,
5646};
5647
5648static int run_aging(struct lruvec *lruvec, unsigned long seq, struct scan_control *sc,
5649 bool can_swap, bool force_scan)
5650{
5651 DEFINE_MAX_SEQ(lruvec);
5652 DEFINE_MIN_SEQ(lruvec);
5653
5654 if (seq < max_seq)
5655 return 0;
5656
5657 if (seq > max_seq)
5658 return -EINVAL;
5659
5660 if (!force_scan && min_seq[!can_swap] + MAX_NR_GENS - 1 <= max_seq)
5661 return -ERANGE;
5662
5663 try_to_inc_max_seq(lruvec, max_seq, sc, can_swap, force_scan);
5664
5665 return 0;
5666}
5667
5668static int run_eviction(struct lruvec *lruvec, unsigned long seq, struct scan_control *sc,
5669 int swappiness, unsigned long nr_to_reclaim)
5670{
5671 DEFINE_MAX_SEQ(lruvec);
5672
5673 if (seq + MIN_NR_GENS > max_seq)
5674 return -EINVAL;
5675
5676 sc->nr_reclaimed = 0;
5677
5678 while (!signal_pending(current)) {
5679 DEFINE_MIN_SEQ(lruvec);
5680
5681 if (seq < min_seq[!swappiness])
5682 return 0;
5683
5684 if (sc->nr_reclaimed >= nr_to_reclaim)
5685 return 0;
5686
5687 if (!evict_folios(lruvec, sc, swappiness, NULL))
5688 return 0;
5689
5690 cond_resched();
5691 }
5692
5693 return -EINTR;
5694}
5695
5696static int run_cmd(char cmd, int memcg_id, int nid, unsigned long seq,
5697 struct scan_control *sc, int swappiness, unsigned long opt)
5698{
5699 struct lruvec *lruvec;
5700 int err = -EINVAL;
5701 struct mem_cgroup *memcg = NULL;
5702
5703 if (nid < 0 || nid >= MAX_NUMNODES || !node_state(nid, N_MEMORY))
5704 return -EINVAL;
5705
5706 if (!mem_cgroup_disabled()) {
5707 rcu_read_lock();
5708 memcg = mem_cgroup_from_id(memcg_id);
5709#ifdef CONFIG_MEMCG
5710 if (memcg && !css_tryget(&memcg->css))
5711 memcg = NULL;
5712#endif
5713 rcu_read_unlock();
5714
5715 if (!memcg)
5716 return -EINVAL;
5717 }
5718
5719 if (memcg_id != mem_cgroup_id(memcg))
5720 goto done;
5721
5722 lruvec = get_lruvec(memcg, nid);
5723
5724 if (swappiness < 0)
5725 swappiness = get_swappiness(lruvec, sc);
5726 else if (swappiness > 200)
5727 goto done;
5728
5729 switch (cmd) {
5730 case '+':
5731 err = run_aging(lruvec, seq, sc, swappiness, opt);
5732 break;
5733 case '-':
5734 err = run_eviction(lruvec, seq, sc, swappiness, opt);
5735 break;
5736 }
5737done:
5738 mem_cgroup_put(memcg);
5739
5740 return err;
5741}
5742
5743/* see Documentation/admin-guide/mm/multigen_lru.rst for details */
5744static ssize_t lru_gen_seq_write(struct file *file, const char __user *src,
5745 size_t len, loff_t *pos)
5746{
5747 void *buf;
5748 char *cur, *next;
5749 unsigned int flags;
5750 struct blk_plug plug;
5751 int err = -EINVAL;
5752 struct scan_control sc = {
5753 .may_writepage = true,
5754 .may_unmap = true,
5755 .may_swap = true,
5756 .reclaim_idx = MAX_NR_ZONES - 1,
5757 .gfp_mask = GFP_KERNEL,
5758 };
5759
5760 buf = kvmalloc(len + 1, GFP_KERNEL);
5761 if (!buf)
5762 return -ENOMEM;
5763
5764 if (copy_from_user(buf, src, len)) {
5765 kvfree(buf);
5766 return -EFAULT;
5767 }
5768
5769 set_task_reclaim_state(current, &sc.reclaim_state);
5770 flags = memalloc_noreclaim_save();
5771 blk_start_plug(&plug);
5772 if (!set_mm_walk(NULL)) {
5773 err = -ENOMEM;
5774 goto done;
5775 }
5776
5777 next = buf;
5778 next[len] = '\0';
5779
5780 while ((cur = strsep(&next, ",;\n"))) {
5781 int n;
5782 int end;
5783 char cmd;
5784 unsigned int memcg_id;
5785 unsigned int nid;
5786 unsigned long seq;
5787 unsigned int swappiness = -1;
5788 unsigned long opt = -1;
5789
5790 cur = skip_spaces(cur);
5791 if (!*cur)
5792 continue;
5793
5794 n = sscanf(cur, "%c %u %u %lu %n %u %n %lu %n", &cmd, &memcg_id, &nid,
5795 &seq, &end, &swappiness, &end, &opt, &end);
5796 if (n < 4 || cur[end]) {
5797 err = -EINVAL;
5798 break;
5799 }
5800
5801 err = run_cmd(cmd, memcg_id, nid, seq, &sc, swappiness, opt);
5802 if (err)
5803 break;
5804 }
5805done:
5806 clear_mm_walk();
5807 blk_finish_plug(&plug);
5808 memalloc_noreclaim_restore(flags);
5809 set_task_reclaim_state(current, NULL);
5810
5811 kvfree(buf);
5812
5813 return err ? : len;
5814}
5815
5816static int lru_gen_seq_open(struct inode *inode, struct file *file)
5817{
5818 return seq_open(file, &lru_gen_seq_ops);
5819}
5820
5821static const struct file_operations lru_gen_rw_fops = {
5822 .open = lru_gen_seq_open,
5823 .read = seq_read,
5824 .write = lru_gen_seq_write,
5825 .llseek = seq_lseek,
5826 .release = seq_release,
5827};
5828
5829static const struct file_operations lru_gen_ro_fops = {
5830 .open = lru_gen_seq_open,
5831 .read = seq_read,
5832 .llseek = seq_lseek,
5833 .release = seq_release,
5834};
5835
5836/******************************************************************************
5837 * initialization
5838 ******************************************************************************/
5839
5840void lru_gen_init_lruvec(struct lruvec *lruvec)
5841{
5842 int i;
5843 int gen, type, zone;
5844 struct lru_gen_struct *lrugen = &lruvec->lrugen;
5845
5846 lrugen->max_seq = MIN_NR_GENS + 1;
5847 lrugen->enabled = lru_gen_enabled();
5848
5849 for (i = 0; i <= MIN_NR_GENS + 1; i++)
5850 lrugen->timestamps[i] = jiffies;
5851
5852 for_each_gen_type_zone(gen, type, zone)
5853 INIT_LIST_HEAD(&lrugen->lists[gen][type][zone]);
5854
5855 lruvec->mm_state.seq = MIN_NR_GENS;
5856 init_waitqueue_head(&lruvec->mm_state.wait);
5857}
5858
5859#ifdef CONFIG_MEMCG
5860void lru_gen_init_memcg(struct mem_cgroup *memcg)
5861{
5862 INIT_LIST_HEAD(&memcg->mm_list.fifo);
5863 spin_lock_init(&memcg->mm_list.lock);
5864}
5865
5866void lru_gen_exit_memcg(struct mem_cgroup *memcg)
5867{
5868 int i;
5869 int nid;
5870
5871 for_each_node(nid) {
5872 struct lruvec *lruvec = get_lruvec(memcg, nid);
5873
5874 VM_WARN_ON_ONCE(memchr_inv(lruvec->lrugen.nr_pages, 0,
5875 sizeof(lruvec->lrugen.nr_pages)));
5876
5877 for (i = 0; i < NR_BLOOM_FILTERS; i++) {
5878 bitmap_free(lruvec->mm_state.filters[i]);
5879 lruvec->mm_state.filters[i] = NULL;
5880 }
5881 }
5882}
5883#endif
5884
5885static int __init init_lru_gen(void)
5886{
5887 BUILD_BUG_ON(MIN_NR_GENS + 1 >= MAX_NR_GENS);
5888 BUILD_BUG_ON(BIT(LRU_GEN_WIDTH) <= MAX_NR_GENS);
5889
5890 if (sysfs_create_group(mm_kobj, &lru_gen_attr_group))
5891 pr_err("lru_gen: failed to create sysfs group\n");
5892
5893 debugfs_create_file("lru_gen", 0644, NULL, NULL, &lru_gen_rw_fops);
5894 debugfs_create_file("lru_gen_full", 0444, NULL, NULL, &lru_gen_ro_fops);
5895
5896 return 0;
5897};
5898late_initcall(init_lru_gen);
5899
5900#else /* !CONFIG_LRU_GEN */
5901
5902static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc)
5903{
5904}
5905
5906static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
5907{
5908}
5909
5910#endif /* CONFIG_LRU_GEN */
5911
5912static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
5913{
5914 unsigned long nr[NR_LRU_LISTS];
5915 unsigned long targets[NR_LRU_LISTS];
5916 unsigned long nr_to_scan;
5917 enum lru_list lru;
5918 unsigned long nr_reclaimed = 0;
5919 unsigned long nr_to_reclaim = sc->nr_to_reclaim;
5920 bool proportional_reclaim;
5921 struct blk_plug plug;
5922
5923 if (lru_gen_enabled()) {
5924 lru_gen_shrink_lruvec(lruvec, sc);
5925 return;
5926 }
5927
5928 get_scan_count(lruvec, sc, nr);
5929
5930 /* Record the original scan target for proportional adjustments later */
5931 memcpy(targets, nr, sizeof(nr));
5932
5933 /*
5934 * Global reclaiming within direct reclaim at DEF_PRIORITY is a normal
5935 * event that can occur when there is little memory pressure e.g.
5936 * multiple streaming readers/writers. Hence, we do not abort scanning
5937 * when the requested number of pages are reclaimed when scanning at
5938 * DEF_PRIORITY on the assumption that the fact we are direct
5939 * reclaiming implies that kswapd is not keeping up and it is best to
5940 * do a batch of work at once. For memcg reclaim one check is made to
5941 * abort proportional reclaim if either the file or anon lru has already
5942 * dropped to zero at the first pass.
5943 */
5944 proportional_reclaim = (!cgroup_reclaim(sc) && !current_is_kswapd() &&
5945 sc->priority == DEF_PRIORITY);
5946
5947 blk_start_plug(&plug);
5948 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
5949 nr[LRU_INACTIVE_FILE]) {
5950 unsigned long nr_anon, nr_file, percentage;
5951 unsigned long nr_scanned;
5952
5953 for_each_evictable_lru(lru) {
5954 if (nr[lru]) {
5955 nr_to_scan = min(nr[lru], SWAP_CLUSTER_MAX);
5956 nr[lru] -= nr_to_scan;
5957
5958 nr_reclaimed += shrink_list(lru, nr_to_scan,
5959 lruvec, sc);
5960 }
5961 }
5962
5963 cond_resched();
5964
5965 if (nr_reclaimed < nr_to_reclaim || proportional_reclaim)
5966 continue;
5967
5968 /*
5969 * For kswapd and memcg, reclaim at least the number of pages
5970 * requested. Ensure that the anon and file LRUs are scanned
5971 * proportionally what was requested by get_scan_count(). We
5972 * stop reclaiming one LRU and reduce the amount scanning
5973 * proportional to the original scan target.
5974 */
5975 nr_file = nr[LRU_INACTIVE_FILE] + nr[LRU_ACTIVE_FILE];
5976 nr_anon = nr[LRU_INACTIVE_ANON] + nr[LRU_ACTIVE_ANON];
5977
5978 /*
5979 * It's just vindictive to attack the larger once the smaller
5980 * has gone to zero. And given the way we stop scanning the
5981 * smaller below, this makes sure that we only make one nudge
5982 * towards proportionality once we've got nr_to_reclaim.
5983 */
5984 if (!nr_file || !nr_anon)
5985 break;
5986
5987 if (nr_file > nr_anon) {
5988 unsigned long scan_target = targets[LRU_INACTIVE_ANON] +
5989 targets[LRU_ACTIVE_ANON] + 1;
5990 lru = LRU_BASE;
5991 percentage = nr_anon * 100 / scan_target;
5992 } else {
5993 unsigned long scan_target = targets[LRU_INACTIVE_FILE] +
5994 targets[LRU_ACTIVE_FILE] + 1;
5995 lru = LRU_FILE;
5996 percentage = nr_file * 100 / scan_target;
5997 }
5998
5999 /* Stop scanning the smaller of the LRU */
6000 nr[lru] = 0;
6001 nr[lru + LRU_ACTIVE] = 0;
6002
6003 /*
6004 * Recalculate the other LRU scan count based on its original
6005 * scan target and the percentage scanning already complete
6006 */
6007 lru = (lru == LRU_FILE) ? LRU_BASE : LRU_FILE;
6008 nr_scanned = targets[lru] - nr[lru];
6009 nr[lru] = targets[lru] * (100 - percentage) / 100;
6010 nr[lru] -= min(nr[lru], nr_scanned);
6011
6012 lru += LRU_ACTIVE;
6013 nr_scanned = targets[lru] - nr[lru];
6014 nr[lru] = targets[lru] * (100 - percentage) / 100;
6015 nr[lru] -= min(nr[lru], nr_scanned);
6016 }
6017 blk_finish_plug(&plug);
6018 sc->nr_reclaimed += nr_reclaimed;
6019
6020 /*
6021 * Even if we did not try to evict anon pages at all, we want to
6022 * rebalance the anon lru active/inactive ratio.
6023 */
6024 if (can_age_anon_pages(lruvec_pgdat(lruvec), sc) &&
6025 inactive_is_low(lruvec, LRU_INACTIVE_ANON))
6026 shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
6027 sc, LRU_ACTIVE_ANON);
6028}
6029
6030/* Use reclaim/compaction for costly allocs or under memory pressure */
6031static bool in_reclaim_compaction(struct scan_control *sc)
6032{
6033 if (IS_ENABLED(CONFIG_COMPACTION) && sc->order &&
6034 (sc->order > PAGE_ALLOC_COSTLY_ORDER ||
6035 sc->priority < DEF_PRIORITY - 2))
6036 return true;
6037
6038 return false;
6039}
6040
6041/*
6042 * Reclaim/compaction is used for high-order allocation requests. It reclaims
6043 * order-0 pages before compacting the zone. should_continue_reclaim() returns
6044 * true if more pages should be reclaimed such that when the page allocator
6045 * calls try_to_compact_pages() that it will have enough free pages to succeed.
6046 * It will give up earlier than that if there is difficulty reclaiming pages.
6047 */
6048static inline bool should_continue_reclaim(struct pglist_data *pgdat,
6049 unsigned long nr_reclaimed,
6050 struct scan_control *sc)
6051{
6052 unsigned long pages_for_compaction;
6053 unsigned long inactive_lru_pages;
6054 int z;
6055
6056 /* If not in reclaim/compaction mode, stop */
6057 if (!in_reclaim_compaction(sc))
6058 return false;
6059
6060 /*
6061 * Stop if we failed to reclaim any pages from the last SWAP_CLUSTER_MAX
6062 * number of pages that were scanned. This will return to the caller
6063 * with the risk reclaim/compaction and the resulting allocation attempt
6064 * fails. In the past we have tried harder for __GFP_RETRY_MAYFAIL
6065 * allocations through requiring that the full LRU list has been scanned
6066 * first, by assuming that zero delta of sc->nr_scanned means full LRU
6067 * scan, but that approximation was wrong, and there were corner cases
6068 * where always a non-zero amount of pages were scanned.
6069 */
6070 if (!nr_reclaimed)
6071 return false;
6072
6073 /* If compaction would go ahead or the allocation would succeed, stop */
6074 for (z = 0; z <= sc->reclaim_idx; z++) {
6075 struct zone *zone = &pgdat->node_zones[z];
6076 if (!managed_zone(zone))
6077 continue;
6078
6079 switch (compaction_suitable(zone, sc->order, 0, sc->reclaim_idx)) {
6080 case COMPACT_SUCCESS:
6081 case COMPACT_CONTINUE:
6082 return false;
6083 default:
6084 /* check next zone */
6085 ;
6086 }
6087 }
6088
6089 /*
6090 * If we have not reclaimed enough pages for compaction and the
6091 * inactive lists are large enough, continue reclaiming
6092 */
6093 pages_for_compaction = compact_gap(sc->order);
6094 inactive_lru_pages = node_page_state(pgdat, NR_INACTIVE_FILE);
6095 if (can_reclaim_anon_pages(NULL, pgdat->node_id, sc))
6096 inactive_lru_pages += node_page_state(pgdat, NR_INACTIVE_ANON);
6097
6098 return inactive_lru_pages > pages_for_compaction;
6099}
6100
6101static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc)
6102{
6103 struct mem_cgroup *target_memcg = sc->target_mem_cgroup;
6104 struct mem_cgroup *memcg;
6105
6106 memcg = mem_cgroup_iter(target_memcg, NULL, NULL);
6107 do {
6108 struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
6109 unsigned long reclaimed;
6110 unsigned long scanned;
6111
6112 /*
6113 * This loop can become CPU-bound when target memcgs
6114 * aren't eligible for reclaim - either because they
6115 * don't have any reclaimable pages, or because their
6116 * memory is explicitly protected. Avoid soft lockups.
6117 */
6118 cond_resched();
6119
6120 mem_cgroup_calculate_protection(target_memcg, memcg);
6121
6122 if (mem_cgroup_below_min(target_memcg, memcg)) {
6123 /*
6124 * Hard protection.
6125 * If there is no reclaimable memory, OOM.
6126 */
6127 continue;
6128 } else if (mem_cgroup_below_low(target_memcg, memcg)) {
6129 /*
6130 * Soft protection.
6131 * Respect the protection only as long as
6132 * there is an unprotected supply
6133 * of reclaimable memory from other cgroups.
6134 */
6135 if (!sc->memcg_low_reclaim) {
6136 sc->memcg_low_skipped = 1;
6137 continue;
6138 }
6139 memcg_memory_event(memcg, MEMCG_LOW);
6140 }
6141
6142 reclaimed = sc->nr_reclaimed;
6143 scanned = sc->nr_scanned;
6144
6145 shrink_lruvec(lruvec, sc);
6146
6147 shrink_slab(sc->gfp_mask, pgdat->node_id, memcg,
6148 sc->priority);
6149
6150 /* Record the group's reclaim efficiency */
6151 if (!sc->proactive)
6152 vmpressure(sc->gfp_mask, memcg, false,
6153 sc->nr_scanned - scanned,
6154 sc->nr_reclaimed - reclaimed);
6155
6156 } while ((memcg = mem_cgroup_iter(target_memcg, memcg, NULL)));
6157}
6158
6159static void shrink_node(pg_data_t *pgdat, struct scan_control *sc)
6160{
6161 struct reclaim_state *reclaim_state = current->reclaim_state;
6162 unsigned long nr_reclaimed, nr_scanned;
6163 struct lruvec *target_lruvec;
6164 bool reclaimable = false;
6165
6166 target_lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup, pgdat);
6167
6168again:
6169 memset(&sc->nr, 0, sizeof(sc->nr));
6170
6171 nr_reclaimed = sc->nr_reclaimed;
6172 nr_scanned = sc->nr_scanned;
6173
6174 prepare_scan_count(pgdat, sc);
6175
6176 shrink_node_memcgs(pgdat, sc);
6177
6178 if (reclaim_state) {
6179 sc->nr_reclaimed += reclaim_state->reclaimed_slab;
6180 reclaim_state->reclaimed_slab = 0;
6181 }
6182
6183 /* Record the subtree's reclaim efficiency */
6184 if (!sc->proactive)
6185 vmpressure(sc->gfp_mask, sc->target_mem_cgroup, true,
6186 sc->nr_scanned - nr_scanned,
6187 sc->nr_reclaimed - nr_reclaimed);
6188
6189 if (sc->nr_reclaimed - nr_reclaimed)
6190 reclaimable = true;
6191
6192 if (current_is_kswapd()) {
6193 /*
6194 * If reclaim is isolating dirty pages under writeback,
6195 * it implies that the long-lived page allocation rate
6196 * is exceeding the page laundering rate. Either the
6197 * global limits are not being effective at throttling
6198 * processes due to the page distribution throughout
6199 * zones or there is heavy usage of a slow backing
6200 * device. The only option is to throttle from reclaim
6201 * context which is not ideal as there is no guarantee
6202 * the dirtying process is throttled in the same way
6203 * balance_dirty_pages() manages.
6204 *
6205 * Once a node is flagged PGDAT_WRITEBACK, kswapd will
6206 * count the number of pages under pages flagged for
6207 * immediate reclaim and stall if any are encountered
6208 * in the nr_immediate check below.
6209 */
6210 if (sc->nr.writeback && sc->nr.writeback == sc->nr.taken)
6211 set_bit(PGDAT_WRITEBACK, &pgdat->flags);
6212
6213 /* Allow kswapd to start writing pages during reclaim.*/
6214 if (sc->nr.unqueued_dirty == sc->nr.file_taken)
6215 set_bit(PGDAT_DIRTY, &pgdat->flags);
6216
6217 /*
6218 * If kswapd scans pages marked for immediate
6219 * reclaim and under writeback (nr_immediate), it
6220 * implies that pages are cycling through the LRU
6221 * faster than they are written so forcibly stall
6222 * until some pages complete writeback.
6223 */
6224 if (sc->nr.immediate)
6225 reclaim_throttle(pgdat, VMSCAN_THROTTLE_WRITEBACK);
6226 }
6227
6228 /*
6229 * Tag a node/memcg as congested if all the dirty pages were marked
6230 * for writeback and immediate reclaim (counted in nr.congested).
6231 *
6232 * Legacy memcg will stall in page writeback so avoid forcibly
6233 * stalling in reclaim_throttle().
6234 */
6235 if ((current_is_kswapd() ||
6236 (cgroup_reclaim(sc) && writeback_throttling_sane(sc))) &&
6237 sc->nr.dirty && sc->nr.dirty == sc->nr.congested)
6238 set_bit(LRUVEC_CONGESTED, &target_lruvec->flags);
6239
6240 /*
6241 * Stall direct reclaim for IO completions if the lruvec is
6242 * node is congested. Allow kswapd to continue until it
6243 * starts encountering unqueued dirty pages or cycling through
6244 * the LRU too quickly.
6245 */
6246 if (!current_is_kswapd() && current_may_throttle() &&
6247 !sc->hibernation_mode &&
6248 test_bit(LRUVEC_CONGESTED, &target_lruvec->flags))
6249 reclaim_throttle(pgdat, VMSCAN_THROTTLE_CONGESTED);
6250
6251 if (should_continue_reclaim(pgdat, sc->nr_reclaimed - nr_reclaimed,
6252 sc))
6253 goto again;
6254
6255 /*
6256 * Kswapd gives up on balancing particular nodes after too
6257 * many failures to reclaim anything from them and goes to
6258 * sleep. On reclaim progress, reset the failure counter. A
6259 * successful direct reclaim run will revive a dormant kswapd.
6260 */
6261 if (reclaimable)
6262 pgdat->kswapd_failures = 0;
6263}
6264
6265/*
6266 * Returns true if compaction should go ahead for a costly-order request, or
6267 * the allocation would already succeed without compaction. Return false if we
6268 * should reclaim first.
6269 */
6270static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
6271{
6272 unsigned long watermark;
6273 enum compact_result suitable;
6274
6275 suitable = compaction_suitable(zone, sc->order, 0, sc->reclaim_idx);
6276 if (suitable == COMPACT_SUCCESS)
6277 /* Allocation should succeed already. Don't reclaim. */
6278 return true;
6279 if (suitable == COMPACT_SKIPPED)
6280 /* Compaction cannot yet proceed. Do reclaim. */
6281 return false;
6282
6283 /*
6284 * Compaction is already possible, but it takes time to run and there
6285 * are potentially other callers using the pages just freed. So proceed
6286 * with reclaim to make a buffer of free pages available to give
6287 * compaction a reasonable chance of completing and allocating the page.
6288 * Note that we won't actually reclaim the whole buffer in one attempt
6289 * as the target watermark in should_continue_reclaim() is lower. But if
6290 * we are already above the high+gap watermark, don't reclaim at all.
6291 */
6292 watermark = high_wmark_pages(zone) + compact_gap(sc->order);
6293
6294 return zone_watermark_ok_safe(zone, 0, watermark, sc->reclaim_idx);
6295}
6296
6297static void consider_reclaim_throttle(pg_data_t *pgdat, struct scan_control *sc)
6298{
6299 /*
6300 * If reclaim is making progress greater than 12% efficiency then
6301 * wake all the NOPROGRESS throttled tasks.
6302 */
6303 if (sc->nr_reclaimed > (sc->nr_scanned >> 3)) {
6304 wait_queue_head_t *wqh;
6305
6306 wqh = &pgdat->reclaim_wait[VMSCAN_THROTTLE_NOPROGRESS];
6307 if (waitqueue_active(wqh))
6308 wake_up(wqh);
6309
6310 return;
6311 }
6312
6313 /*
6314 * Do not throttle kswapd or cgroup reclaim on NOPROGRESS as it will
6315 * throttle on VMSCAN_THROTTLE_WRITEBACK if there are too many pages
6316 * under writeback and marked for immediate reclaim at the tail of the
6317 * LRU.
6318 */
6319 if (current_is_kswapd() || cgroup_reclaim(sc))
6320 return;
6321
6322 /* Throttle if making no progress at high prioities. */
6323 if (sc->priority == 1 && !sc->nr_reclaimed)
6324 reclaim_throttle(pgdat, VMSCAN_THROTTLE_NOPROGRESS);
6325}
6326
6327/*
6328 * This is the direct reclaim path, for page-allocating processes. We only
6329 * try to reclaim pages from zones which will satisfy the caller's allocation
6330 * request.
6331 *
6332 * If a zone is deemed to be full of pinned pages then just give it a light
6333 * scan then give up on it.
6334 */
6335static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
6336{
6337 struct zoneref *z;
6338 struct zone *zone;
6339 unsigned long nr_soft_reclaimed;
6340 unsigned long nr_soft_scanned;
6341 gfp_t orig_mask;
6342 pg_data_t *last_pgdat = NULL;
6343 pg_data_t *first_pgdat = NULL;
6344
6345 /*
6346 * If the number of buffer_heads in the machine exceeds the maximum
6347 * allowed level, force direct reclaim to scan the highmem zone as
6348 * highmem pages could be pinning lowmem pages storing buffer_heads
6349 */
6350 orig_mask = sc->gfp_mask;
6351 if (buffer_heads_over_limit) {
6352 sc->gfp_mask |= __GFP_HIGHMEM;
6353 sc->reclaim_idx = gfp_zone(sc->gfp_mask);
6354 }
6355
6356 for_each_zone_zonelist_nodemask(zone, z, zonelist,
6357 sc->reclaim_idx, sc->nodemask) {
6358 /*
6359 * Take care memory controller reclaiming has small influence
6360 * to global LRU.
6361 */
6362 if (!cgroup_reclaim(sc)) {
6363 if (!cpuset_zone_allowed(zone,
6364 GFP_KERNEL | __GFP_HARDWALL))
6365 continue;
6366
6367 /*
6368 * If we already have plenty of memory free for
6369 * compaction in this zone, don't free any more.
6370 * Even though compaction is invoked for any
6371 * non-zero order, only frequent costly order
6372 * reclamation is disruptive enough to become a
6373 * noticeable problem, like transparent huge
6374 * page allocations.
6375 */
6376 if (IS_ENABLED(CONFIG_COMPACTION) &&
6377 sc->order > PAGE_ALLOC_COSTLY_ORDER &&
6378 compaction_ready(zone, sc)) {
6379 sc->compaction_ready = true;
6380 continue;
6381 }
6382
6383 /*
6384 * Shrink each node in the zonelist once. If the
6385 * zonelist is ordered by zone (not the default) then a
6386 * node may be shrunk multiple times but in that case
6387 * the user prefers lower zones being preserved.
6388 */
6389 if (zone->zone_pgdat == last_pgdat)
6390 continue;
6391
6392 /*
6393 * This steals pages from memory cgroups over softlimit
6394 * and returns the number of reclaimed pages and
6395 * scanned pages. This works for global memory pressure
6396 * and balancing, not for a memcg's limit.
6397 */
6398 nr_soft_scanned = 0;
6399 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone->zone_pgdat,
6400 sc->order, sc->gfp_mask,
6401 &nr_soft_scanned);
6402 sc->nr_reclaimed += nr_soft_reclaimed;
6403 sc->nr_scanned += nr_soft_scanned;
6404 /* need some check for avoid more shrink_zone() */
6405 }
6406
6407 if (!first_pgdat)
6408 first_pgdat = zone->zone_pgdat;
6409
6410 /* See comment about same check for global reclaim above */
6411 if (zone->zone_pgdat == last_pgdat)
6412 continue;
6413 last_pgdat = zone->zone_pgdat;
6414 shrink_node(zone->zone_pgdat, sc);
6415 }
6416
6417 if (first_pgdat)
6418 consider_reclaim_throttle(first_pgdat, sc);
6419
6420 /*
6421 * Restore to original mask to avoid the impact on the caller if we
6422 * promoted it to __GFP_HIGHMEM.
6423 */
6424 sc->gfp_mask = orig_mask;
6425}
6426
6427static void snapshot_refaults(struct mem_cgroup *target_memcg, pg_data_t *pgdat)
6428{
6429 struct lruvec *target_lruvec;
6430 unsigned long refaults;
6431
6432 if (lru_gen_enabled())
6433 return;
6434
6435 target_lruvec = mem_cgroup_lruvec(target_memcg, pgdat);
6436 refaults = lruvec_page_state(target_lruvec, WORKINGSET_ACTIVATE_ANON);
6437 target_lruvec->refaults[WORKINGSET_ANON] = refaults;
6438 refaults = lruvec_page_state(target_lruvec, WORKINGSET_ACTIVATE_FILE);
6439 target_lruvec->refaults[WORKINGSET_FILE] = refaults;
6440}
6441
6442/*
6443 * This is the main entry point to direct page reclaim.
6444 *
6445 * If a full scan of the inactive list fails to free enough memory then we
6446 * are "out of memory" and something needs to be killed.
6447 *
6448 * If the caller is !__GFP_FS then the probability of a failure is reasonably
6449 * high - the zone may be full of dirty or under-writeback pages, which this
6450 * caller can't do much about. We kick the writeback threads and take explicit
6451 * naps in the hope that some of these pages can be written. But if the
6452 * allocating task holds filesystem locks which prevent writeout this might not
6453 * work, and the allocation attempt will fail.
6454 *
6455 * returns: 0, if no pages reclaimed
6456 * else, the number of pages reclaimed
6457 */
6458static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
6459 struct scan_control *sc)
6460{
6461 int initial_priority = sc->priority;
6462 pg_data_t *last_pgdat;
6463 struct zoneref *z;
6464 struct zone *zone;
6465retry:
6466 delayacct_freepages_start();
6467
6468 if (!cgroup_reclaim(sc))
6469 __count_zid_vm_events(ALLOCSTALL, sc->reclaim_idx, 1);
6470
6471 do {
6472 if (!sc->proactive)
6473 vmpressure_prio(sc->gfp_mask, sc->target_mem_cgroup,
6474 sc->priority);
6475 sc->nr_scanned = 0;
6476 shrink_zones(zonelist, sc);
6477
6478 if (sc->nr_reclaimed >= sc->nr_to_reclaim)
6479 break;
6480
6481 if (sc->compaction_ready)
6482 break;
6483
6484 /*
6485 * If we're getting trouble reclaiming, start doing
6486 * writepage even in laptop mode.
6487 */
6488 if (sc->priority < DEF_PRIORITY - 2)
6489 sc->may_writepage = 1;
6490 } while (--sc->priority >= 0);
6491
6492 last_pgdat = NULL;
6493 for_each_zone_zonelist_nodemask(zone, z, zonelist, sc->reclaim_idx,
6494 sc->nodemask) {
6495 if (zone->zone_pgdat == last_pgdat)
6496 continue;
6497 last_pgdat = zone->zone_pgdat;
6498
6499 snapshot_refaults(sc->target_mem_cgroup, zone->zone_pgdat);
6500
6501 if (cgroup_reclaim(sc)) {
6502 struct lruvec *lruvec;
6503
6504 lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup,
6505 zone->zone_pgdat);
6506 clear_bit(LRUVEC_CONGESTED, &lruvec->flags);
6507 }
6508 }
6509
6510 delayacct_freepages_end();
6511
6512 if (sc->nr_reclaimed)
6513 return sc->nr_reclaimed;
6514
6515 /* Aborted reclaim to try compaction? don't OOM, then */
6516 if (sc->compaction_ready)
6517 return 1;
6518
6519 /*
6520 * We make inactive:active ratio decisions based on the node's
6521 * composition of memory, but a restrictive reclaim_idx or a
6522 * memory.low cgroup setting can exempt large amounts of
6523 * memory from reclaim. Neither of which are very common, so
6524 * instead of doing costly eligibility calculations of the
6525 * entire cgroup subtree up front, we assume the estimates are
6526 * good, and retry with forcible deactivation if that fails.
6527 */
6528 if (sc->skipped_deactivate) {
6529 sc->priority = initial_priority;
6530 sc->force_deactivate = 1;
6531 sc->skipped_deactivate = 0;
6532 goto retry;
6533 }
6534
6535 /* Untapped cgroup reserves? Don't OOM, retry. */
6536 if (sc->memcg_low_skipped) {
6537 sc->priority = initial_priority;
6538 sc->force_deactivate = 0;
6539 sc->memcg_low_reclaim = 1;
6540 sc->memcg_low_skipped = 0;
6541 goto retry;
6542 }
6543
6544 return 0;
6545}
6546
6547static bool allow_direct_reclaim(pg_data_t *pgdat)
6548{
6549 struct zone *zone;
6550 unsigned long pfmemalloc_reserve = 0;
6551 unsigned long free_pages = 0;
6552 int i;
6553 bool wmark_ok;
6554
6555 if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES)
6556 return true;
6557
6558 for (i = 0; i <= ZONE_NORMAL; i++) {
6559 zone = &pgdat->node_zones[i];
6560 if (!managed_zone(zone))
6561 continue;
6562
6563 if (!zone_reclaimable_pages(zone))
6564 continue;
6565
6566 pfmemalloc_reserve += min_wmark_pages(zone);
6567 free_pages += zone_page_state(zone, NR_FREE_PAGES);
6568 }
6569
6570 /* If there are no reserves (unexpected config) then do not throttle */
6571 if (!pfmemalloc_reserve)
6572 return true;
6573
6574 wmark_ok = free_pages > pfmemalloc_reserve / 2;
6575
6576 /* kswapd must be awake if processes are being throttled */
6577 if (!wmark_ok && waitqueue_active(&pgdat->kswapd_wait)) {
6578 if (READ_ONCE(pgdat->kswapd_highest_zoneidx) > ZONE_NORMAL)
6579 WRITE_ONCE(pgdat->kswapd_highest_zoneidx, ZONE_NORMAL);
6580
6581 wake_up_interruptible(&pgdat->kswapd_wait);
6582 }
6583
6584 return wmark_ok;
6585}
6586
6587/*
6588 * Throttle direct reclaimers if backing storage is backed by the network
6589 * and the PFMEMALLOC reserve for the preferred node is getting dangerously
6590 * depleted. kswapd will continue to make progress and wake the processes
6591 * when the low watermark is reached.
6592 *
6593 * Returns true if a fatal signal was delivered during throttling. If this
6594 * happens, the page allocator should not consider triggering the OOM killer.
6595 */
6596static bool throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist *zonelist,
6597 nodemask_t *nodemask)
6598{
6599 struct zoneref *z;
6600 struct zone *zone;
6601 pg_data_t *pgdat = NULL;
6602
6603 /*
6604 * Kernel threads should not be throttled as they may be indirectly
6605 * responsible for cleaning pages necessary for reclaim to make forward
6606 * progress. kjournald for example may enter direct reclaim while
6607 * committing a transaction where throttling it could forcing other
6608 * processes to block on log_wait_commit().
6609 */
6610 if (current->flags & PF_KTHREAD)
6611 goto out;
6612
6613 /*
6614 * If a fatal signal is pending, this process should not throttle.
6615 * It should return quickly so it can exit and free its memory
6616 */
6617 if (fatal_signal_pending(current))
6618 goto out;
6619
6620 /*
6621 * Check if the pfmemalloc reserves are ok by finding the first node
6622 * with a usable ZONE_NORMAL or lower zone. The expectation is that
6623 * GFP_KERNEL will be required for allocating network buffers when
6624 * swapping over the network so ZONE_HIGHMEM is unusable.
6625 *
6626 * Throttling is based on the first usable node and throttled processes
6627 * wait on a queue until kswapd makes progress and wakes them. There
6628 * is an affinity then between processes waking up and where reclaim
6629 * progress has been made assuming the process wakes on the same node.
6630 * More importantly, processes running on remote nodes will not compete
6631 * for remote pfmemalloc reserves and processes on different nodes
6632 * should make reasonable progress.
6633 */
6634 for_each_zone_zonelist_nodemask(zone, z, zonelist,
6635 gfp_zone(gfp_mask), nodemask) {
6636 if (zone_idx(zone) > ZONE_NORMAL)
6637 continue;
6638
6639 /* Throttle based on the first usable node */
6640 pgdat = zone->zone_pgdat;
6641 if (allow_direct_reclaim(pgdat))
6642 goto out;
6643 break;
6644 }
6645
6646 /* If no zone was usable by the allocation flags then do not throttle */
6647 if (!pgdat)
6648 goto out;
6649
6650 /* Account for the throttling */
6651 count_vm_event(PGSCAN_DIRECT_THROTTLE);
6652
6653 /*
6654 * If the caller cannot enter the filesystem, it's possible that it
6655 * is due to the caller holding an FS lock or performing a journal
6656 * transaction in the case of a filesystem like ext[3|4]. In this case,
6657 * it is not safe to block on pfmemalloc_wait as kswapd could be
6658 * blocked waiting on the same lock. Instead, throttle for up to a
6659 * second before continuing.
6660 */
6661 if (!(gfp_mask & __GFP_FS))
6662 wait_event_interruptible_timeout(pgdat->pfmemalloc_wait,
6663 allow_direct_reclaim(pgdat), HZ);
6664 else
6665 /* Throttle until kswapd wakes the process */
6666 wait_event_killable(zone->zone_pgdat->pfmemalloc_wait,
6667 allow_direct_reclaim(pgdat));
6668
6669 if (fatal_signal_pending(current))
6670 return true;
6671
6672out:
6673 return false;
6674}
6675
6676unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
6677 gfp_t gfp_mask, nodemask_t *nodemask)
6678{
6679 unsigned long nr_reclaimed;
6680 struct scan_control sc = {
6681 .nr_to_reclaim = SWAP_CLUSTER_MAX,
6682 .gfp_mask = current_gfp_context(gfp_mask),
6683 .reclaim_idx = gfp_zone(gfp_mask),
6684 .order = order,
6685 .nodemask = nodemask,
6686 .priority = DEF_PRIORITY,
6687 .may_writepage = !laptop_mode,
6688 .may_unmap = 1,
6689 .may_swap = 1,
6690 };
6691
6692 /*
6693 * scan_control uses s8 fields for order, priority, and reclaim_idx.
6694 * Confirm they are large enough for max values.
6695 */
6696 BUILD_BUG_ON(MAX_ORDER > S8_MAX);
6697 BUILD_BUG_ON(DEF_PRIORITY > S8_MAX);
6698 BUILD_BUG_ON(MAX_NR_ZONES > S8_MAX);
6699
6700 /*
6701 * Do not enter reclaim if fatal signal was delivered while throttled.
6702 * 1 is returned so that the page allocator does not OOM kill at this
6703 * point.
6704 */
6705 if (throttle_direct_reclaim(sc.gfp_mask, zonelist, nodemask))
6706 return 1;
6707
6708 set_task_reclaim_state(current, &sc.reclaim_state);
6709 trace_mm_vmscan_direct_reclaim_begin(order, sc.gfp_mask);
6710
6711 nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
6712
6713 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
6714 set_task_reclaim_state(current, NULL);
6715
6716 return nr_reclaimed;
6717}
6718
6719#ifdef CONFIG_MEMCG
6720
6721/* Only used by soft limit reclaim. Do not reuse for anything else. */
6722unsigned long mem_cgroup_shrink_node(struct mem_cgroup *memcg,
6723 gfp_t gfp_mask, bool noswap,
6724 pg_data_t *pgdat,
6725 unsigned long *nr_scanned)
6726{
6727 struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
6728 struct scan_control sc = {
6729 .nr_to_reclaim = SWAP_CLUSTER_MAX,
6730 .target_mem_cgroup = memcg,
6731 .may_writepage = !laptop_mode,
6732 .may_unmap = 1,
6733 .reclaim_idx = MAX_NR_ZONES - 1,
6734 .may_swap = !noswap,
6735 };
6736
6737 WARN_ON_ONCE(!current->reclaim_state);
6738
6739 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
6740 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
6741
6742 trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc.order,
6743 sc.gfp_mask);
6744
6745 /*
6746 * NOTE: Although we can get the priority field, using it
6747 * here is not a good idea, since it limits the pages we can scan.
6748 * if we don't reclaim here, the shrink_node from balance_pgdat
6749 * will pick up pages from other mem cgroup's as well. We hack
6750 * the priority and make it zero.
6751 */
6752 shrink_lruvec(lruvec, &sc);
6753
6754 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
6755
6756 *nr_scanned = sc.nr_scanned;
6757
6758 return sc.nr_reclaimed;
6759}
6760
6761unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
6762 unsigned long nr_pages,
6763 gfp_t gfp_mask,
6764 unsigned int reclaim_options)
6765{
6766 unsigned long nr_reclaimed;
6767 unsigned int noreclaim_flag;
6768 struct scan_control sc = {
6769 .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
6770 .gfp_mask = (current_gfp_context(gfp_mask) & GFP_RECLAIM_MASK) |
6771 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
6772 .reclaim_idx = MAX_NR_ZONES - 1,
6773 .target_mem_cgroup = memcg,
6774 .priority = DEF_PRIORITY,
6775 .may_writepage = !laptop_mode,
6776 .may_unmap = 1,
6777 .may_swap = !!(reclaim_options & MEMCG_RECLAIM_MAY_SWAP),
6778 .proactive = !!(reclaim_options & MEMCG_RECLAIM_PROACTIVE),
6779 };
6780 /*
6781 * Traverse the ZONELIST_FALLBACK zonelist of the current node to put
6782 * equal pressure on all the nodes. This is based on the assumption that
6783 * the reclaim does not bail out early.
6784 */
6785 struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
6786
6787 set_task_reclaim_state(current, &sc.reclaim_state);
6788 trace_mm_vmscan_memcg_reclaim_begin(0, sc.gfp_mask);
6789 noreclaim_flag = memalloc_noreclaim_save();
6790
6791 nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
6792
6793 memalloc_noreclaim_restore(noreclaim_flag);
6794 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
6795 set_task_reclaim_state(current, NULL);
6796
6797 return nr_reclaimed;
6798}
6799#endif
6800
6801static void kswapd_age_node(struct pglist_data *pgdat, struct scan_control *sc)
6802{
6803 struct mem_cgroup *memcg;
6804 struct lruvec *lruvec;
6805
6806 if (lru_gen_enabled()) {
6807 lru_gen_age_node(pgdat, sc);
6808 return;
6809 }
6810
6811 if (!can_age_anon_pages(pgdat, sc))
6812 return;
6813
6814 lruvec = mem_cgroup_lruvec(NULL, pgdat);
6815 if (!inactive_is_low(lruvec, LRU_INACTIVE_ANON))
6816 return;
6817
6818 memcg = mem_cgroup_iter(NULL, NULL, NULL);
6819 do {
6820 lruvec = mem_cgroup_lruvec(memcg, pgdat);
6821 shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
6822 sc, LRU_ACTIVE_ANON);
6823 memcg = mem_cgroup_iter(NULL, memcg, NULL);
6824 } while (memcg);
6825}
6826
6827static bool pgdat_watermark_boosted(pg_data_t *pgdat, int highest_zoneidx)
6828{
6829 int i;
6830 struct zone *zone;
6831
6832 /*
6833 * Check for watermark boosts top-down as the higher zones
6834 * are more likely to be boosted. Both watermarks and boosts
6835 * should not be checked at the same time as reclaim would
6836 * start prematurely when there is no boosting and a lower
6837 * zone is balanced.
6838 */
6839 for (i = highest_zoneidx; i >= 0; i--) {
6840 zone = pgdat->node_zones + i;
6841 if (!managed_zone(zone))
6842 continue;
6843
6844 if (zone->watermark_boost)
6845 return true;
6846 }
6847
6848 return false;
6849}
6850
6851/*
6852 * Returns true if there is an eligible zone balanced for the request order
6853 * and highest_zoneidx
6854 */
6855static bool pgdat_balanced(pg_data_t *pgdat, int order, int highest_zoneidx)
6856{
6857 int i;
6858 unsigned long mark = -1;
6859 struct zone *zone;
6860
6861 /*
6862 * Check watermarks bottom-up as lower zones are more likely to
6863 * meet watermarks.
6864 */
6865 for (i = 0; i <= highest_zoneidx; i++) {
6866 zone = pgdat->node_zones + i;
6867
6868 if (!managed_zone(zone))
6869 continue;
6870
6871 if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING)
6872 mark = wmark_pages(zone, WMARK_PROMO);
6873 else
6874 mark = high_wmark_pages(zone);
6875 if (zone_watermark_ok_safe(zone, order, mark, highest_zoneidx))
6876 return true;
6877 }
6878
6879 /*
6880 * If a node has no managed zone within highest_zoneidx, it does not
6881 * need balancing by definition. This can happen if a zone-restricted
6882 * allocation tries to wake a remote kswapd.
6883 */
6884 if (mark == -1)
6885 return true;
6886
6887 return false;
6888}
6889
6890/* Clear pgdat state for congested, dirty or under writeback. */
6891static void clear_pgdat_congested(pg_data_t *pgdat)
6892{
6893 struct lruvec *lruvec = mem_cgroup_lruvec(NULL, pgdat);
6894
6895 clear_bit(LRUVEC_CONGESTED, &lruvec->flags);
6896 clear_bit(PGDAT_DIRTY, &pgdat->flags);
6897 clear_bit(PGDAT_WRITEBACK, &pgdat->flags);
6898}
6899
6900/*
6901 * Prepare kswapd for sleeping. This verifies that there are no processes
6902 * waiting in throttle_direct_reclaim() and that watermarks have been met.
6903 *
6904 * Returns true if kswapd is ready to sleep
6905 */
6906static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order,
6907 int highest_zoneidx)
6908{
6909 /*
6910 * The throttled processes are normally woken up in balance_pgdat() as
6911 * soon as allow_direct_reclaim() is true. But there is a potential
6912 * race between when kswapd checks the watermarks and a process gets
6913 * throttled. There is also a potential race if processes get
6914 * throttled, kswapd wakes, a large process exits thereby balancing the
6915 * zones, which causes kswapd to exit balance_pgdat() before reaching
6916 * the wake up checks. If kswapd is going to sleep, no process should
6917 * be sleeping on pfmemalloc_wait, so wake them now if necessary. If
6918 * the wake up is premature, processes will wake kswapd and get
6919 * throttled again. The difference from wake ups in balance_pgdat() is
6920 * that here we are under prepare_to_wait().
6921 */
6922 if (waitqueue_active(&pgdat->pfmemalloc_wait))
6923 wake_up_all(&pgdat->pfmemalloc_wait);
6924
6925 /* Hopeless node, leave it to direct reclaim */
6926 if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES)
6927 return true;
6928
6929 if (pgdat_balanced(pgdat, order, highest_zoneidx)) {
6930 clear_pgdat_congested(pgdat);
6931 return true;
6932 }
6933
6934 return false;
6935}
6936
6937/*
6938 * kswapd shrinks a node of pages that are at or below the highest usable
6939 * zone that is currently unbalanced.
6940 *
6941 * Returns true if kswapd scanned at least the requested number of pages to
6942 * reclaim or if the lack of progress was due to pages under writeback.
6943 * This is used to determine if the scanning priority needs to be raised.
6944 */
6945static bool kswapd_shrink_node(pg_data_t *pgdat,
6946 struct scan_control *sc)
6947{
6948 struct zone *zone;
6949 int z;
6950
6951 /* Reclaim a number of pages proportional to the number of zones */
6952 sc->nr_to_reclaim = 0;
6953 for (z = 0; z <= sc->reclaim_idx; z++) {
6954 zone = pgdat->node_zones + z;
6955 if (!managed_zone(zone))
6956 continue;
6957
6958 sc->nr_to_reclaim += max(high_wmark_pages(zone), SWAP_CLUSTER_MAX);
6959 }
6960
6961 /*
6962 * Historically care was taken to put equal pressure on all zones but
6963 * now pressure is applied based on node LRU order.
6964 */
6965 shrink_node(pgdat, sc);
6966
6967 /*
6968 * Fragmentation may mean that the system cannot be rebalanced for
6969 * high-order allocations. If twice the allocation size has been
6970 * reclaimed then recheck watermarks only at order-0 to prevent
6971 * excessive reclaim. Assume that a process requested a high-order
6972 * can direct reclaim/compact.
6973 */
6974 if (sc->order && sc->nr_reclaimed >= compact_gap(sc->order))
6975 sc->order = 0;
6976
6977 return sc->nr_scanned >= sc->nr_to_reclaim;
6978}
6979
6980/* Page allocator PCP high watermark is lowered if reclaim is active. */
6981static inline void
6982update_reclaim_active(pg_data_t *pgdat, int highest_zoneidx, bool active)
6983{
6984 int i;
6985 struct zone *zone;
6986
6987 for (i = 0; i <= highest_zoneidx; i++) {
6988 zone = pgdat->node_zones + i;
6989
6990 if (!managed_zone(zone))
6991 continue;
6992
6993 if (active)
6994 set_bit(ZONE_RECLAIM_ACTIVE, &zone->flags);
6995 else
6996 clear_bit(ZONE_RECLAIM_ACTIVE, &zone->flags);
6997 }
6998}
6999
7000static inline void
7001set_reclaim_active(pg_data_t *pgdat, int highest_zoneidx)
7002{
7003 update_reclaim_active(pgdat, highest_zoneidx, true);
7004}
7005
7006static inline void
7007clear_reclaim_active(pg_data_t *pgdat, int highest_zoneidx)
7008{
7009 update_reclaim_active(pgdat, highest_zoneidx, false);
7010}
7011
7012/*
7013 * For kswapd, balance_pgdat() will reclaim pages across a node from zones
7014 * that are eligible for use by the caller until at least one zone is
7015 * balanced.
7016 *
7017 * Returns the order kswapd finished reclaiming at.
7018 *
7019 * kswapd scans the zones in the highmem->normal->dma direction. It skips
7020 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
7021 * found to have free_pages <= high_wmark_pages(zone), any page in that zone
7022 * or lower is eligible for reclaim until at least one usable zone is
7023 * balanced.
7024 */
7025static int balance_pgdat(pg_data_t *pgdat, int order, int highest_zoneidx)
7026{
7027 int i;
7028 unsigned long nr_soft_reclaimed;
7029 unsigned long nr_soft_scanned;
7030 unsigned long pflags;
7031 unsigned long nr_boost_reclaim;
7032 unsigned long zone_boosts[MAX_NR_ZONES] = { 0, };
7033 bool boosted;
7034 struct zone *zone;
7035 struct scan_control sc = {
7036 .gfp_mask = GFP_KERNEL,
7037 .order = order,
7038 .may_unmap = 1,
7039 };
7040
7041 set_task_reclaim_state(current, &sc.reclaim_state);
7042 psi_memstall_enter(&pflags);
7043 __fs_reclaim_acquire(_THIS_IP_);
7044
7045 count_vm_event(PAGEOUTRUN);
7046
7047 /*
7048 * Account for the reclaim boost. Note that the zone boost is left in
7049 * place so that parallel allocations that are near the watermark will
7050 * stall or direct reclaim until kswapd is finished.
7051 */
7052 nr_boost_reclaim = 0;
7053 for (i = 0; i <= highest_zoneidx; i++) {
7054 zone = pgdat->node_zones + i;
7055 if (!managed_zone(zone))
7056 continue;
7057
7058 nr_boost_reclaim += zone->watermark_boost;
7059 zone_boosts[i] = zone->watermark_boost;
7060 }
7061 boosted = nr_boost_reclaim;
7062
7063restart:
7064 set_reclaim_active(pgdat, highest_zoneidx);
7065 sc.priority = DEF_PRIORITY;
7066 do {
7067 unsigned long nr_reclaimed = sc.nr_reclaimed;
7068 bool raise_priority = true;
7069 bool balanced;
7070 bool ret;
7071
7072 sc.reclaim_idx = highest_zoneidx;
7073
7074 /*
7075 * If the number of buffer_heads exceeds the maximum allowed
7076 * then consider reclaiming from all zones. This has a dual
7077 * purpose -- on 64-bit systems it is expected that
7078 * buffer_heads are stripped during active rotation. On 32-bit
7079 * systems, highmem pages can pin lowmem memory and shrinking
7080 * buffers can relieve lowmem pressure. Reclaim may still not
7081 * go ahead if all eligible zones for the original allocation
7082 * request are balanced to avoid excessive reclaim from kswapd.
7083 */
7084 if (buffer_heads_over_limit) {
7085 for (i = MAX_NR_ZONES - 1; i >= 0; i--) {
7086 zone = pgdat->node_zones + i;
7087 if (!managed_zone(zone))
7088 continue;
7089
7090 sc.reclaim_idx = i;
7091 break;
7092 }
7093 }
7094
7095 /*
7096 * If the pgdat is imbalanced then ignore boosting and preserve
7097 * the watermarks for a later time and restart. Note that the
7098 * zone watermarks will be still reset at the end of balancing
7099 * on the grounds that the normal reclaim should be enough to
7100 * re-evaluate if boosting is required when kswapd next wakes.
7101 */
7102 balanced = pgdat_balanced(pgdat, sc.order, highest_zoneidx);
7103 if (!balanced && nr_boost_reclaim) {
7104 nr_boost_reclaim = 0;
7105 goto restart;
7106 }
7107
7108 /*
7109 * If boosting is not active then only reclaim if there are no
7110 * eligible zones. Note that sc.reclaim_idx is not used as
7111 * buffer_heads_over_limit may have adjusted it.
7112 */
7113 if (!nr_boost_reclaim && balanced)
7114 goto out;
7115
7116 /* Limit the priority of boosting to avoid reclaim writeback */
7117 if (nr_boost_reclaim && sc.priority == DEF_PRIORITY - 2)
7118 raise_priority = false;
7119
7120 /*
7121 * Do not writeback or swap pages for boosted reclaim. The
7122 * intent is to relieve pressure not issue sub-optimal IO
7123 * from reclaim context. If no pages are reclaimed, the
7124 * reclaim will be aborted.
7125 */
7126 sc.may_writepage = !laptop_mode && !nr_boost_reclaim;
7127 sc.may_swap = !nr_boost_reclaim;
7128
7129 /*
7130 * Do some background aging, to give pages a chance to be
7131 * referenced before reclaiming. All pages are rotated
7132 * regardless of classzone as this is about consistent aging.
7133 */
7134 kswapd_age_node(pgdat, &sc);
7135
7136 /*
7137 * If we're getting trouble reclaiming, start doing writepage
7138 * even in laptop mode.
7139 */
7140 if (sc.priority < DEF_PRIORITY - 2)
7141 sc.may_writepage = 1;
7142
7143 /* Call soft limit reclaim before calling shrink_node. */
7144 sc.nr_scanned = 0;
7145 nr_soft_scanned = 0;
7146 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(pgdat, sc.order,
7147 sc.gfp_mask, &nr_soft_scanned);
7148 sc.nr_reclaimed += nr_soft_reclaimed;
7149
7150 /*
7151 * There should be no need to raise the scanning priority if
7152 * enough pages are already being scanned that that high
7153 * watermark would be met at 100% efficiency.
7154 */
7155 if (kswapd_shrink_node(pgdat, &sc))
7156 raise_priority = false;
7157
7158 /*
7159 * If the low watermark is met there is no need for processes
7160 * to be throttled on pfmemalloc_wait as they should not be
7161 * able to safely make forward progress. Wake them
7162 */
7163 if (waitqueue_active(&pgdat->pfmemalloc_wait) &&
7164 allow_direct_reclaim(pgdat))
7165 wake_up_all(&pgdat->pfmemalloc_wait);
7166
7167 /* Check if kswapd should be suspending */
7168 __fs_reclaim_release(_THIS_IP_);
7169 ret = try_to_freeze();
7170 __fs_reclaim_acquire(_THIS_IP_);
7171 if (ret || kthread_should_stop())
7172 break;
7173
7174 /*
7175 * Raise priority if scanning rate is too low or there was no
7176 * progress in reclaiming pages
7177 */
7178 nr_reclaimed = sc.nr_reclaimed - nr_reclaimed;
7179 nr_boost_reclaim -= min(nr_boost_reclaim, nr_reclaimed);
7180
7181 /*
7182 * If reclaim made no progress for a boost, stop reclaim as
7183 * IO cannot be queued and it could be an infinite loop in
7184 * extreme circumstances.
7185 */
7186 if (nr_boost_reclaim && !nr_reclaimed)
7187 break;
7188
7189 if (raise_priority || !nr_reclaimed)
7190 sc.priority--;
7191 } while (sc.priority >= 1);
7192
7193 if (!sc.nr_reclaimed)
7194 pgdat->kswapd_failures++;
7195
7196out:
7197 clear_reclaim_active(pgdat, highest_zoneidx);
7198
7199 /* If reclaim was boosted, account for the reclaim done in this pass */
7200 if (boosted) {
7201 unsigned long flags;
7202
7203 for (i = 0; i <= highest_zoneidx; i++) {
7204 if (!zone_boosts[i])
7205 continue;
7206
7207 /* Increments are under the zone lock */
7208 zone = pgdat->node_zones + i;
7209 spin_lock_irqsave(&zone->lock, flags);
7210 zone->watermark_boost -= min(zone->watermark_boost, zone_boosts[i]);
7211 spin_unlock_irqrestore(&zone->lock, flags);
7212 }
7213
7214 /*
7215 * As there is now likely space, wakeup kcompact to defragment
7216 * pageblocks.
7217 */
7218 wakeup_kcompactd(pgdat, pageblock_order, highest_zoneidx);
7219 }
7220
7221 snapshot_refaults(NULL, pgdat);
7222 __fs_reclaim_release(_THIS_IP_);
7223 psi_memstall_leave(&pflags);
7224 set_task_reclaim_state(current, NULL);
7225
7226 /*
7227 * Return the order kswapd stopped reclaiming at as
7228 * prepare_kswapd_sleep() takes it into account. If another caller
7229 * entered the allocator slow path while kswapd was awake, order will
7230 * remain at the higher level.
7231 */
7232 return sc.order;
7233}
7234
7235/*
7236 * The pgdat->kswapd_highest_zoneidx is used to pass the highest zone index to
7237 * be reclaimed by kswapd from the waker. If the value is MAX_NR_ZONES which is
7238 * not a valid index then either kswapd runs for first time or kswapd couldn't
7239 * sleep after previous reclaim attempt (node is still unbalanced). In that
7240 * case return the zone index of the previous kswapd reclaim cycle.
7241 */
7242static enum zone_type kswapd_highest_zoneidx(pg_data_t *pgdat,
7243 enum zone_type prev_highest_zoneidx)
7244{
7245 enum zone_type curr_idx = READ_ONCE(pgdat->kswapd_highest_zoneidx);
7246
7247 return curr_idx == MAX_NR_ZONES ? prev_highest_zoneidx : curr_idx;
7248}
7249
7250static void kswapd_try_to_sleep(pg_data_t *pgdat, int alloc_order, int reclaim_order,
7251 unsigned int highest_zoneidx)
7252{
7253 long remaining = 0;
7254 DEFINE_WAIT(wait);
7255
7256 if (freezing(current) || kthread_should_stop())
7257 return;
7258
7259 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
7260
7261 /*
7262 * Try to sleep for a short interval. Note that kcompactd will only be
7263 * woken if it is possible to sleep for a short interval. This is
7264 * deliberate on the assumption that if reclaim cannot keep an
7265 * eligible zone balanced that it's also unlikely that compaction will
7266 * succeed.
7267 */
7268 if (prepare_kswapd_sleep(pgdat, reclaim_order, highest_zoneidx)) {
7269 /*
7270 * Compaction records what page blocks it recently failed to
7271 * isolate pages from and skips them in the future scanning.
7272 * When kswapd is going to sleep, it is reasonable to assume
7273 * that pages and compaction may succeed so reset the cache.
7274 */
7275 reset_isolation_suitable(pgdat);
7276
7277 /*
7278 * We have freed the memory, now we should compact it to make
7279 * allocation of the requested order possible.
7280 */
7281 wakeup_kcompactd(pgdat, alloc_order, highest_zoneidx);
7282
7283 remaining = schedule_timeout(HZ/10);
7284
7285 /*
7286 * If woken prematurely then reset kswapd_highest_zoneidx and
7287 * order. The values will either be from a wakeup request or
7288 * the previous request that slept prematurely.
7289 */
7290 if (remaining) {
7291 WRITE_ONCE(pgdat->kswapd_highest_zoneidx,
7292 kswapd_highest_zoneidx(pgdat,
7293 highest_zoneidx));
7294
7295 if (READ_ONCE(pgdat->kswapd_order) < reclaim_order)
7296 WRITE_ONCE(pgdat->kswapd_order, reclaim_order);
7297 }
7298
7299 finish_wait(&pgdat->kswapd_wait, &wait);
7300 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
7301 }
7302
7303 /*
7304 * After a short sleep, check if it was a premature sleep. If not, then
7305 * go fully to sleep until explicitly woken up.
7306 */
7307 if (!remaining &&
7308 prepare_kswapd_sleep(pgdat, reclaim_order, highest_zoneidx)) {
7309 trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
7310
7311 /*
7312 * vmstat counters are not perfectly accurate and the estimated
7313 * value for counters such as NR_FREE_PAGES can deviate from the
7314 * true value by nr_online_cpus * threshold. To avoid the zone
7315 * watermarks being breached while under pressure, we reduce the
7316 * per-cpu vmstat threshold while kswapd is awake and restore
7317 * them before going back to sleep.
7318 */
7319 set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold);
7320
7321 if (!kthread_should_stop())
7322 schedule();
7323
7324 set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold);
7325 } else {
7326 if (remaining)
7327 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
7328 else
7329 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
7330 }
7331 finish_wait(&pgdat->kswapd_wait, &wait);
7332}
7333
7334/*
7335 * The background pageout daemon, started as a kernel thread
7336 * from the init process.
7337 *
7338 * This basically trickles out pages so that we have _some_
7339 * free memory available even if there is no other activity
7340 * that frees anything up. This is needed for things like routing
7341 * etc, where we otherwise might have all activity going on in
7342 * asynchronous contexts that cannot page things out.
7343 *
7344 * If there are applications that are active memory-allocators
7345 * (most normal use), this basically shouldn't matter.
7346 */
7347static int kswapd(void *p)
7348{
7349 unsigned int alloc_order, reclaim_order;
7350 unsigned int highest_zoneidx = MAX_NR_ZONES - 1;
7351 pg_data_t *pgdat = (pg_data_t *)p;
7352 struct task_struct *tsk = current;
7353 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
7354
7355 if (!cpumask_empty(cpumask))
7356 set_cpus_allowed_ptr(tsk, cpumask);
7357
7358 /*
7359 * Tell the memory management that we're a "memory allocator",
7360 * and that if we need more memory we should get access to it
7361 * regardless (see "__alloc_pages()"). "kswapd" should
7362 * never get caught in the normal page freeing logic.
7363 *
7364 * (Kswapd normally doesn't need memory anyway, but sometimes
7365 * you need a small amount of memory in order to be able to
7366 * page out something else, and this flag essentially protects
7367 * us from recursively trying to free more memory as we're
7368 * trying to free the first piece of memory in the first place).
7369 */
7370 tsk->flags |= PF_MEMALLOC | PF_KSWAPD;
7371 set_freezable();
7372
7373 WRITE_ONCE(pgdat->kswapd_order, 0);
7374 WRITE_ONCE(pgdat->kswapd_highest_zoneidx, MAX_NR_ZONES);
7375 atomic_set(&pgdat->nr_writeback_throttled, 0);
7376 for ( ; ; ) {
7377 bool ret;
7378
7379 alloc_order = reclaim_order = READ_ONCE(pgdat->kswapd_order);
7380 highest_zoneidx = kswapd_highest_zoneidx(pgdat,
7381 highest_zoneidx);
7382
7383kswapd_try_sleep:
7384 kswapd_try_to_sleep(pgdat, alloc_order, reclaim_order,
7385 highest_zoneidx);
7386
7387 /* Read the new order and highest_zoneidx */
7388 alloc_order = READ_ONCE(pgdat->kswapd_order);
7389 highest_zoneidx = kswapd_highest_zoneidx(pgdat,
7390 highest_zoneidx);
7391 WRITE_ONCE(pgdat->kswapd_order, 0);
7392 WRITE_ONCE(pgdat->kswapd_highest_zoneidx, MAX_NR_ZONES);
7393
7394 ret = try_to_freeze();
7395 if (kthread_should_stop())
7396 break;
7397
7398 /*
7399 * We can speed up thawing tasks if we don't call balance_pgdat
7400 * after returning from the refrigerator
7401 */
7402 if (ret)
7403 continue;
7404
7405 /*
7406 * Reclaim begins at the requested order but if a high-order
7407 * reclaim fails then kswapd falls back to reclaiming for
7408 * order-0. If that happens, kswapd will consider sleeping
7409 * for the order it finished reclaiming at (reclaim_order)
7410 * but kcompactd is woken to compact for the original
7411 * request (alloc_order).
7412 */
7413 trace_mm_vmscan_kswapd_wake(pgdat->node_id, highest_zoneidx,
7414 alloc_order);
7415 reclaim_order = balance_pgdat(pgdat, alloc_order,
7416 highest_zoneidx);
7417 if (reclaim_order < alloc_order)
7418 goto kswapd_try_sleep;
7419 }
7420
7421 tsk->flags &= ~(PF_MEMALLOC | PF_KSWAPD);
7422
7423 return 0;
7424}
7425
7426/*
7427 * A zone is low on free memory or too fragmented for high-order memory. If
7428 * kswapd should reclaim (direct reclaim is deferred), wake it up for the zone's
7429 * pgdat. It will wake up kcompactd after reclaiming memory. If kswapd reclaim
7430 * has failed or is not needed, still wake up kcompactd if only compaction is
7431 * needed.
7432 */
7433void wakeup_kswapd(struct zone *zone, gfp_t gfp_flags, int order,
7434 enum zone_type highest_zoneidx)
7435{
7436 pg_data_t *pgdat;
7437 enum zone_type curr_idx;
7438
7439 if (!managed_zone(zone))
7440 return;
7441
7442 if (!cpuset_zone_allowed(zone, gfp_flags))
7443 return;
7444
7445 pgdat = zone->zone_pgdat;
7446 curr_idx = READ_ONCE(pgdat->kswapd_highest_zoneidx);
7447
7448 if (curr_idx == MAX_NR_ZONES || curr_idx < highest_zoneidx)
7449 WRITE_ONCE(pgdat->kswapd_highest_zoneidx, highest_zoneidx);
7450
7451 if (READ_ONCE(pgdat->kswapd_order) < order)
7452 WRITE_ONCE(pgdat->kswapd_order, order);
7453
7454 if (!waitqueue_active(&pgdat->kswapd_wait))
7455 return;
7456
7457 /* Hopeless node, leave it to direct reclaim if possible */
7458 if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES ||
7459 (pgdat_balanced(pgdat, order, highest_zoneidx) &&
7460 !pgdat_watermark_boosted(pgdat, highest_zoneidx))) {
7461 /*
7462 * There may be plenty of free memory available, but it's too
7463 * fragmented for high-order allocations. Wake up kcompactd
7464 * and rely on compaction_suitable() to determine if it's
7465 * needed. If it fails, it will defer subsequent attempts to
7466 * ratelimit its work.
7467 */
7468 if (!(gfp_flags & __GFP_DIRECT_RECLAIM))
7469 wakeup_kcompactd(pgdat, order, highest_zoneidx);
7470 return;
7471 }
7472
7473 trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, highest_zoneidx, order,
7474 gfp_flags);
7475 wake_up_interruptible(&pgdat->kswapd_wait);
7476}
7477
7478#ifdef CONFIG_HIBERNATION
7479/*
7480 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
7481 * freed pages.
7482 *
7483 * Rather than trying to age LRUs the aim is to preserve the overall
7484 * LRU order by reclaiming preferentially
7485 * inactive > active > active referenced > active mapped
7486 */
7487unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
7488{
7489 struct scan_control sc = {
7490 .nr_to_reclaim = nr_to_reclaim,
7491 .gfp_mask = GFP_HIGHUSER_MOVABLE,
7492 .reclaim_idx = MAX_NR_ZONES - 1,
7493 .priority = DEF_PRIORITY,
7494 .may_writepage = 1,
7495 .may_unmap = 1,
7496 .may_swap = 1,
7497 .hibernation_mode = 1,
7498 };
7499 struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
7500 unsigned long nr_reclaimed;
7501 unsigned int noreclaim_flag;
7502
7503 fs_reclaim_acquire(sc.gfp_mask);
7504 noreclaim_flag = memalloc_noreclaim_save();
7505 set_task_reclaim_state(current, &sc.reclaim_state);
7506
7507 nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
7508
7509 set_task_reclaim_state(current, NULL);
7510 memalloc_noreclaim_restore(noreclaim_flag);
7511 fs_reclaim_release(sc.gfp_mask);
7512
7513 return nr_reclaimed;
7514}
7515#endif /* CONFIG_HIBERNATION */
7516
7517/*
7518 * This kswapd start function will be called by init and node-hot-add.
7519 */
7520void kswapd_run(int nid)
7521{
7522 pg_data_t *pgdat = NODE_DATA(nid);
7523
7524 pgdat_kswapd_lock(pgdat);
7525 if (!pgdat->kswapd) {
7526 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
7527 if (IS_ERR(pgdat->kswapd)) {
7528 /* failure at boot is fatal */
7529 BUG_ON(system_state < SYSTEM_RUNNING);
7530 pr_err("Failed to start kswapd on node %d\n", nid);
7531 pgdat->kswapd = NULL;
7532 }
7533 }
7534 pgdat_kswapd_unlock(pgdat);
7535}
7536
7537/*
7538 * Called by memory hotplug when all memory in a node is offlined. Caller must
7539 * be holding mem_hotplug_begin/done().
7540 */
7541void kswapd_stop(int nid)
7542{
7543 pg_data_t *pgdat = NODE_DATA(nid);
7544 struct task_struct *kswapd;
7545
7546 pgdat_kswapd_lock(pgdat);
7547 kswapd = pgdat->kswapd;
7548 if (kswapd) {
7549 kthread_stop(kswapd);
7550 pgdat->kswapd = NULL;
7551 }
7552 pgdat_kswapd_unlock(pgdat);
7553}
7554
7555static int __init kswapd_init(void)
7556{
7557 int nid;
7558
7559 swap_setup();
7560 for_each_node_state(nid, N_MEMORY)
7561 kswapd_run(nid);
7562 return 0;
7563}
7564
7565module_init(kswapd_init)
7566
7567#ifdef CONFIG_NUMA
7568/*
7569 * Node reclaim mode
7570 *
7571 * If non-zero call node_reclaim when the number of free pages falls below
7572 * the watermarks.
7573 */
7574int node_reclaim_mode __read_mostly;
7575
7576/*
7577 * Priority for NODE_RECLAIM. This determines the fraction of pages
7578 * of a node considered for each zone_reclaim. 4 scans 1/16th of
7579 * a zone.
7580 */
7581#define NODE_RECLAIM_PRIORITY 4
7582
7583/*
7584 * Percentage of pages in a zone that must be unmapped for node_reclaim to
7585 * occur.
7586 */
7587int sysctl_min_unmapped_ratio = 1;
7588
7589/*
7590 * If the number of slab pages in a zone grows beyond this percentage then
7591 * slab reclaim needs to occur.
7592 */
7593int sysctl_min_slab_ratio = 5;
7594
7595static inline unsigned long node_unmapped_file_pages(struct pglist_data *pgdat)
7596{
7597 unsigned long file_mapped = node_page_state(pgdat, NR_FILE_MAPPED);
7598 unsigned long file_lru = node_page_state(pgdat, NR_INACTIVE_FILE) +
7599 node_page_state(pgdat, NR_ACTIVE_FILE);
7600
7601 /*
7602 * It's possible for there to be more file mapped pages than
7603 * accounted for by the pages on the file LRU lists because
7604 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
7605 */
7606 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
7607}
7608
7609/* Work out how many page cache pages we can reclaim in this reclaim_mode */
7610static unsigned long node_pagecache_reclaimable(struct pglist_data *pgdat)
7611{
7612 unsigned long nr_pagecache_reclaimable;
7613 unsigned long delta = 0;
7614
7615 /*
7616 * If RECLAIM_UNMAP is set, then all file pages are considered
7617 * potentially reclaimable. Otherwise, we have to worry about
7618 * pages like swapcache and node_unmapped_file_pages() provides
7619 * a better estimate
7620 */
7621 if (node_reclaim_mode & RECLAIM_UNMAP)
7622 nr_pagecache_reclaimable = node_page_state(pgdat, NR_FILE_PAGES);
7623 else
7624 nr_pagecache_reclaimable = node_unmapped_file_pages(pgdat);
7625
7626 /* If we can't clean pages, remove dirty pages from consideration */
7627 if (!(node_reclaim_mode & RECLAIM_WRITE))
7628 delta += node_page_state(pgdat, NR_FILE_DIRTY);
7629
7630 /* Watch for any possible underflows due to delta */
7631 if (unlikely(delta > nr_pagecache_reclaimable))
7632 delta = nr_pagecache_reclaimable;
7633
7634 return nr_pagecache_reclaimable - delta;
7635}
7636
7637/*
7638 * Try to free up some pages from this node through reclaim.
7639 */
7640static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order)
7641{
7642 /* Minimum pages needed in order to stay on node */
7643 const unsigned long nr_pages = 1 << order;
7644 struct task_struct *p = current;
7645 unsigned int noreclaim_flag;
7646 struct scan_control sc = {
7647 .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
7648 .gfp_mask = current_gfp_context(gfp_mask),
7649 .order = order,
7650 .priority = NODE_RECLAIM_PRIORITY,
7651 .may_writepage = !!(node_reclaim_mode & RECLAIM_WRITE),
7652 .may_unmap = !!(node_reclaim_mode & RECLAIM_UNMAP),
7653 .may_swap = 1,
7654 .reclaim_idx = gfp_zone(gfp_mask),
7655 };
7656 unsigned long pflags;
7657
7658 trace_mm_vmscan_node_reclaim_begin(pgdat->node_id, order,
7659 sc.gfp_mask);
7660
7661 cond_resched();
7662 psi_memstall_enter(&pflags);
7663 fs_reclaim_acquire(sc.gfp_mask);
7664 /*
7665 * We need to be able to allocate from the reserves for RECLAIM_UNMAP
7666 */
7667 noreclaim_flag = memalloc_noreclaim_save();
7668 set_task_reclaim_state(p, &sc.reclaim_state);
7669
7670 if (node_pagecache_reclaimable(pgdat) > pgdat->min_unmapped_pages ||
7671 node_page_state_pages(pgdat, NR_SLAB_RECLAIMABLE_B) > pgdat->min_slab_pages) {
7672 /*
7673 * Free memory by calling shrink node with increasing
7674 * priorities until we have enough memory freed.
7675 */
7676 do {
7677 shrink_node(pgdat, &sc);
7678 } while (sc.nr_reclaimed < nr_pages && --sc.priority >= 0);
7679 }
7680
7681 set_task_reclaim_state(p, NULL);
7682 memalloc_noreclaim_restore(noreclaim_flag);
7683 fs_reclaim_release(sc.gfp_mask);
7684 psi_memstall_leave(&pflags);
7685
7686 trace_mm_vmscan_node_reclaim_end(sc.nr_reclaimed);
7687
7688 return sc.nr_reclaimed >= nr_pages;
7689}
7690
7691int node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order)
7692{
7693 int ret;
7694
7695 /*
7696 * Node reclaim reclaims unmapped file backed pages and
7697 * slab pages if we are over the defined limits.
7698 *
7699 * A small portion of unmapped file backed pages is needed for
7700 * file I/O otherwise pages read by file I/O will be immediately
7701 * thrown out if the node is overallocated. So we do not reclaim
7702 * if less than a specified percentage of the node is used by
7703 * unmapped file backed pages.
7704 */
7705 if (node_pagecache_reclaimable(pgdat) <= pgdat->min_unmapped_pages &&
7706 node_page_state_pages(pgdat, NR_SLAB_RECLAIMABLE_B) <=
7707 pgdat->min_slab_pages)
7708 return NODE_RECLAIM_FULL;
7709
7710 /*
7711 * Do not scan if the allocation should not be delayed.
7712 */
7713 if (!gfpflags_allow_blocking(gfp_mask) || (current->flags & PF_MEMALLOC))
7714 return NODE_RECLAIM_NOSCAN;
7715
7716 /*
7717 * Only run node reclaim on the local node or on nodes that do not
7718 * have associated processors. This will favor the local processor
7719 * over remote processors and spread off node memory allocations
7720 * as wide as possible.
7721 */
7722 if (node_state(pgdat->node_id, N_CPU) && pgdat->node_id != numa_node_id())
7723 return NODE_RECLAIM_NOSCAN;
7724
7725 if (test_and_set_bit(PGDAT_RECLAIM_LOCKED, &pgdat->flags))
7726 return NODE_RECLAIM_NOSCAN;
7727
7728 ret = __node_reclaim(pgdat, gfp_mask, order);
7729 clear_bit(PGDAT_RECLAIM_LOCKED, &pgdat->flags);
7730
7731 if (!ret)
7732 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
7733
7734 return ret;
7735}
7736#endif
7737
7738void check_move_unevictable_pages(struct pagevec *pvec)
7739{
7740 struct folio_batch fbatch;
7741 unsigned i;
7742
7743 folio_batch_init(&fbatch);
7744 for (i = 0; i < pvec->nr; i++) {
7745 struct page *page = pvec->pages[i];
7746
7747 if (PageTransTail(page))
7748 continue;
7749 folio_batch_add(&fbatch, page_folio(page));
7750 }
7751 check_move_unevictable_folios(&fbatch);
7752}
7753EXPORT_SYMBOL_GPL(check_move_unevictable_pages);
7754
7755/**
7756 * check_move_unevictable_folios - Move evictable folios to appropriate zone
7757 * lru list
7758 * @fbatch: Batch of lru folios to check.
7759 *
7760 * Checks folios for evictability, if an evictable folio is in the unevictable
7761 * lru list, moves it to the appropriate evictable lru list. This function
7762 * should be only used for lru folios.
7763 */
7764void check_move_unevictable_folios(struct folio_batch *fbatch)
7765{
7766 struct lruvec *lruvec = NULL;
7767 int pgscanned = 0;
7768 int pgrescued = 0;
7769 int i;
7770
7771 for (i = 0; i < fbatch->nr; i++) {
7772 struct folio *folio = fbatch->folios[i];
7773 int nr_pages = folio_nr_pages(folio);
7774
7775 pgscanned += nr_pages;
7776
7777 /* block memcg migration while the folio moves between lrus */
7778 if (!folio_test_clear_lru(folio))
7779 continue;
7780
7781 lruvec = folio_lruvec_relock_irq(folio, lruvec);
7782 if (folio_evictable(folio) && folio_test_unevictable(folio)) {
7783 lruvec_del_folio(lruvec, folio);
7784 folio_clear_unevictable(folio);
7785 lruvec_add_folio(lruvec, folio);
7786 pgrescued += nr_pages;
7787 }
7788 folio_set_lru(folio);
7789 }
7790
7791 if (lruvec) {
7792 __count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
7793 __count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned);
7794 unlock_page_lruvec_irq(lruvec);
7795 } else if (pgscanned) {
7796 count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned);
7797 }
7798}
7799EXPORT_SYMBOL_GPL(check_move_unevictable_folios);