Loading...
1/*
2 * linux/mm/vmscan.c
3 *
4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
5 *
6 * Swap reorganised 29.12.95, Stephen Tweedie.
7 * kswapd added: 7.1.96 sct
8 * Removed kswapd_ctl limits, and swap out as many pages as needed
9 * to bring the system back to freepages.high: 2.4.97, Rik van Riel.
10 * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
11 * Multiqueue VM started 5.8.00, Rik van Riel.
12 */
13
14#include <linux/mm.h>
15#include <linux/module.h>
16#include <linux/gfp.h>
17#include <linux/kernel_stat.h>
18#include <linux/swap.h>
19#include <linux/pagemap.h>
20#include <linux/init.h>
21#include <linux/highmem.h>
22#include <linux/vmstat.h>
23#include <linux/file.h>
24#include <linux/writeback.h>
25#include <linux/blkdev.h>
26#include <linux/buffer_head.h> /* for try_to_release_page(),
27 buffer_heads_over_limit */
28#include <linux/mm_inline.h>
29#include <linux/pagevec.h>
30#include <linux/backing-dev.h>
31#include <linux/rmap.h>
32#include <linux/topology.h>
33#include <linux/cpu.h>
34#include <linux/cpuset.h>
35#include <linux/compaction.h>
36#include <linux/notifier.h>
37#include <linux/rwsem.h>
38#include <linux/delay.h>
39#include <linux/kthread.h>
40#include <linux/freezer.h>
41#include <linux/memcontrol.h>
42#include <linux/delayacct.h>
43#include <linux/sysctl.h>
44#include <linux/oom.h>
45#include <linux/prefetch.h>
46
47#include <asm/tlbflush.h>
48#include <asm/div64.h>
49
50#include <linux/swapops.h>
51
52#include "internal.h"
53
54#define CREATE_TRACE_POINTS
55#include <trace/events/vmscan.h>
56
57/*
58 * reclaim_mode determines how the inactive list is shrunk
59 * RECLAIM_MODE_SINGLE: Reclaim only order-0 pages
60 * RECLAIM_MODE_ASYNC: Do not block
61 * RECLAIM_MODE_SYNC: Allow blocking e.g. call wait_on_page_writeback
62 * RECLAIM_MODE_LUMPYRECLAIM: For high-order allocations, take a reference
63 * page from the LRU and reclaim all pages within a
64 * naturally aligned range
65 * RECLAIM_MODE_COMPACTION: For high-order allocations, reclaim a number of
66 * order-0 pages and then compact the zone
67 */
68typedef unsigned __bitwise__ reclaim_mode_t;
69#define RECLAIM_MODE_SINGLE ((__force reclaim_mode_t)0x01u)
70#define RECLAIM_MODE_ASYNC ((__force reclaim_mode_t)0x02u)
71#define RECLAIM_MODE_SYNC ((__force reclaim_mode_t)0x04u)
72#define RECLAIM_MODE_LUMPYRECLAIM ((__force reclaim_mode_t)0x08u)
73#define RECLAIM_MODE_COMPACTION ((__force reclaim_mode_t)0x10u)
74
75struct scan_control {
76 /* Incremented by the number of inactive pages that were scanned */
77 unsigned long nr_scanned;
78
79 /* Number of pages freed so far during a call to shrink_zones() */
80 unsigned long nr_reclaimed;
81
82 /* How many pages shrink_list() should reclaim */
83 unsigned long nr_to_reclaim;
84
85 unsigned long hibernation_mode;
86
87 /* This context's GFP mask */
88 gfp_t gfp_mask;
89
90 int may_writepage;
91
92 /* Can mapped pages be reclaimed? */
93 int may_unmap;
94
95 /* Can pages be swapped as part of reclaim? */
96 int may_swap;
97
98 int order;
99
100 /*
101 * Intend to reclaim enough continuous memory rather than reclaim
102 * enough amount of memory. i.e, mode for high order allocation.
103 */
104 reclaim_mode_t reclaim_mode;
105
106 /* Which cgroup do we reclaim from */
107 struct mem_cgroup *mem_cgroup;
108
109 /*
110 * Nodemask of nodes allowed by the caller. If NULL, all nodes
111 * are scanned.
112 */
113 nodemask_t *nodemask;
114};
115
116#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
117
118#ifdef ARCH_HAS_PREFETCH
119#define prefetch_prev_lru_page(_page, _base, _field) \
120 do { \
121 if ((_page)->lru.prev != _base) { \
122 struct page *prev; \
123 \
124 prev = lru_to_page(&(_page->lru)); \
125 prefetch(&prev->_field); \
126 } \
127 } while (0)
128#else
129#define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
130#endif
131
132#ifdef ARCH_HAS_PREFETCHW
133#define prefetchw_prev_lru_page(_page, _base, _field) \
134 do { \
135 if ((_page)->lru.prev != _base) { \
136 struct page *prev; \
137 \
138 prev = lru_to_page(&(_page->lru)); \
139 prefetchw(&prev->_field); \
140 } \
141 } while (0)
142#else
143#define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
144#endif
145
146/*
147 * From 0 .. 100. Higher means more swappy.
148 */
149int vm_swappiness = 60;
150long vm_total_pages; /* The total number of pages which the VM controls */
151
152static LIST_HEAD(shrinker_list);
153static DECLARE_RWSEM(shrinker_rwsem);
154
155#ifdef CONFIG_CGROUP_MEM_RES_CTLR
156#define scanning_global_lru(sc) (!(sc)->mem_cgroup)
157#else
158#define scanning_global_lru(sc) (1)
159#endif
160
161static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone,
162 struct scan_control *sc)
163{
164 if (!scanning_global_lru(sc))
165 return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone);
166
167 return &zone->reclaim_stat;
168}
169
170static unsigned long zone_nr_lru_pages(struct zone *zone,
171 struct scan_control *sc, enum lru_list lru)
172{
173 if (!scanning_global_lru(sc))
174 return mem_cgroup_zone_nr_lru_pages(sc->mem_cgroup,
175 zone_to_nid(zone), zone_idx(zone), BIT(lru));
176
177 return zone_page_state(zone, NR_LRU_BASE + lru);
178}
179
180
181/*
182 * Add a shrinker callback to be called from the vm
183 */
184void register_shrinker(struct shrinker *shrinker)
185{
186 shrinker->nr = 0;
187 down_write(&shrinker_rwsem);
188 list_add_tail(&shrinker->list, &shrinker_list);
189 up_write(&shrinker_rwsem);
190}
191EXPORT_SYMBOL(register_shrinker);
192
193/*
194 * Remove one
195 */
196void unregister_shrinker(struct shrinker *shrinker)
197{
198 down_write(&shrinker_rwsem);
199 list_del(&shrinker->list);
200 up_write(&shrinker_rwsem);
201}
202EXPORT_SYMBOL(unregister_shrinker);
203
204static inline int do_shrinker_shrink(struct shrinker *shrinker,
205 struct shrink_control *sc,
206 unsigned long nr_to_scan)
207{
208 sc->nr_to_scan = nr_to_scan;
209 return (*shrinker->shrink)(shrinker, sc);
210}
211
212#define SHRINK_BATCH 128
213/*
214 * Call the shrink functions to age shrinkable caches
215 *
216 * Here we assume it costs one seek to replace a lru page and that it also
217 * takes a seek to recreate a cache object. With this in mind we age equal
218 * percentages of the lru and ageable caches. This should balance the seeks
219 * generated by these structures.
220 *
221 * If the vm encountered mapped pages on the LRU it increase the pressure on
222 * slab to avoid swapping.
223 *
224 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
225 *
226 * `lru_pages' represents the number of on-LRU pages in all the zones which
227 * are eligible for the caller's allocation attempt. It is used for balancing
228 * slab reclaim versus page reclaim.
229 *
230 * Returns the number of slab objects which we shrunk.
231 */
232unsigned long shrink_slab(struct shrink_control *shrink,
233 unsigned long nr_pages_scanned,
234 unsigned long lru_pages)
235{
236 struct shrinker *shrinker;
237 unsigned long ret = 0;
238
239 if (nr_pages_scanned == 0)
240 nr_pages_scanned = SWAP_CLUSTER_MAX;
241
242 if (!down_read_trylock(&shrinker_rwsem)) {
243 /* Assume we'll be able to shrink next time */
244 ret = 1;
245 goto out;
246 }
247
248 list_for_each_entry(shrinker, &shrinker_list, list) {
249 unsigned long long delta;
250 unsigned long total_scan;
251 unsigned long max_pass;
252 int shrink_ret = 0;
253 long nr;
254 long new_nr;
255 long batch_size = shrinker->batch ? shrinker->batch
256 : SHRINK_BATCH;
257
258 /*
259 * copy the current shrinker scan count into a local variable
260 * and zero it so that other concurrent shrinker invocations
261 * don't also do this scanning work.
262 */
263 do {
264 nr = shrinker->nr;
265 } while (cmpxchg(&shrinker->nr, nr, 0) != nr);
266
267 total_scan = nr;
268 max_pass = do_shrinker_shrink(shrinker, shrink, 0);
269 delta = (4 * nr_pages_scanned) / shrinker->seeks;
270 delta *= max_pass;
271 do_div(delta, lru_pages + 1);
272 total_scan += delta;
273 if (total_scan < 0) {
274 printk(KERN_ERR "shrink_slab: %pF negative objects to "
275 "delete nr=%ld\n",
276 shrinker->shrink, total_scan);
277 total_scan = max_pass;
278 }
279
280 /*
281 * We need to avoid excessive windup on filesystem shrinkers
282 * due to large numbers of GFP_NOFS allocations causing the
283 * shrinkers to return -1 all the time. This results in a large
284 * nr being built up so when a shrink that can do some work
285 * comes along it empties the entire cache due to nr >>>
286 * max_pass. This is bad for sustaining a working set in
287 * memory.
288 *
289 * Hence only allow the shrinker to scan the entire cache when
290 * a large delta change is calculated directly.
291 */
292 if (delta < max_pass / 4)
293 total_scan = min(total_scan, max_pass / 2);
294
295 /*
296 * Avoid risking looping forever due to too large nr value:
297 * never try to free more than twice the estimate number of
298 * freeable entries.
299 */
300 if (total_scan > max_pass * 2)
301 total_scan = max_pass * 2;
302
303 trace_mm_shrink_slab_start(shrinker, shrink, nr,
304 nr_pages_scanned, lru_pages,
305 max_pass, delta, total_scan);
306
307 while (total_scan >= batch_size) {
308 int nr_before;
309
310 nr_before = do_shrinker_shrink(shrinker, shrink, 0);
311 shrink_ret = do_shrinker_shrink(shrinker, shrink,
312 batch_size);
313 if (shrink_ret == -1)
314 break;
315 if (shrink_ret < nr_before)
316 ret += nr_before - shrink_ret;
317 count_vm_events(SLABS_SCANNED, batch_size);
318 total_scan -= batch_size;
319
320 cond_resched();
321 }
322
323 /*
324 * move the unused scan count back into the shrinker in a
325 * manner that handles concurrent updates. If we exhausted the
326 * scan, there is no need to do an update.
327 */
328 do {
329 nr = shrinker->nr;
330 new_nr = total_scan + nr;
331 if (total_scan <= 0)
332 break;
333 } while (cmpxchg(&shrinker->nr, nr, new_nr) != nr);
334
335 trace_mm_shrink_slab_end(shrinker, shrink_ret, nr, new_nr);
336 }
337 up_read(&shrinker_rwsem);
338out:
339 cond_resched();
340 return ret;
341}
342
343static void set_reclaim_mode(int priority, struct scan_control *sc,
344 bool sync)
345{
346 reclaim_mode_t syncmode = sync ? RECLAIM_MODE_SYNC : RECLAIM_MODE_ASYNC;
347
348 /*
349 * Initially assume we are entering either lumpy reclaim or
350 * reclaim/compaction.Depending on the order, we will either set the
351 * sync mode or just reclaim order-0 pages later.
352 */
353 if (COMPACTION_BUILD)
354 sc->reclaim_mode = RECLAIM_MODE_COMPACTION;
355 else
356 sc->reclaim_mode = RECLAIM_MODE_LUMPYRECLAIM;
357
358 /*
359 * Avoid using lumpy reclaim or reclaim/compaction if possible by
360 * restricting when its set to either costly allocations or when
361 * under memory pressure
362 */
363 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
364 sc->reclaim_mode |= syncmode;
365 else if (sc->order && priority < DEF_PRIORITY - 2)
366 sc->reclaim_mode |= syncmode;
367 else
368 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC;
369}
370
371static void reset_reclaim_mode(struct scan_control *sc)
372{
373 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC;
374}
375
376static inline int is_page_cache_freeable(struct page *page)
377{
378 /*
379 * A freeable page cache page is referenced only by the caller
380 * that isolated the page, the page cache radix tree and
381 * optional buffer heads at page->private.
382 */
383 return page_count(page) - page_has_private(page) == 2;
384}
385
386static int may_write_to_queue(struct backing_dev_info *bdi,
387 struct scan_control *sc)
388{
389 if (current->flags & PF_SWAPWRITE)
390 return 1;
391 if (!bdi_write_congested(bdi))
392 return 1;
393 if (bdi == current->backing_dev_info)
394 return 1;
395
396 /* lumpy reclaim for hugepage often need a lot of write */
397 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
398 return 1;
399 return 0;
400}
401
402/*
403 * We detected a synchronous write error writing a page out. Probably
404 * -ENOSPC. We need to propagate that into the address_space for a subsequent
405 * fsync(), msync() or close().
406 *
407 * The tricky part is that after writepage we cannot touch the mapping: nothing
408 * prevents it from being freed up. But we have a ref on the page and once
409 * that page is locked, the mapping is pinned.
410 *
411 * We're allowed to run sleeping lock_page() here because we know the caller has
412 * __GFP_FS.
413 */
414static void handle_write_error(struct address_space *mapping,
415 struct page *page, int error)
416{
417 lock_page(page);
418 if (page_mapping(page) == mapping)
419 mapping_set_error(mapping, error);
420 unlock_page(page);
421}
422
423/* possible outcome of pageout() */
424typedef enum {
425 /* failed to write page out, page is locked */
426 PAGE_KEEP,
427 /* move page to the active list, page is locked */
428 PAGE_ACTIVATE,
429 /* page has been sent to the disk successfully, page is unlocked */
430 PAGE_SUCCESS,
431 /* page is clean and locked */
432 PAGE_CLEAN,
433} pageout_t;
434
435/*
436 * pageout is called by shrink_page_list() for each dirty page.
437 * Calls ->writepage().
438 */
439static pageout_t pageout(struct page *page, struct address_space *mapping,
440 struct scan_control *sc)
441{
442 /*
443 * If the page is dirty, only perform writeback if that write
444 * will be non-blocking. To prevent this allocation from being
445 * stalled by pagecache activity. But note that there may be
446 * stalls if we need to run get_block(). We could test
447 * PagePrivate for that.
448 *
449 * If this process is currently in __generic_file_aio_write() against
450 * this page's queue, we can perform writeback even if that
451 * will block.
452 *
453 * If the page is swapcache, write it back even if that would
454 * block, for some throttling. This happens by accident, because
455 * swap_backing_dev_info is bust: it doesn't reflect the
456 * congestion state of the swapdevs. Easy to fix, if needed.
457 */
458 if (!is_page_cache_freeable(page))
459 return PAGE_KEEP;
460 if (!mapping) {
461 /*
462 * Some data journaling orphaned pages can have
463 * page->mapping == NULL while being dirty with clean buffers.
464 */
465 if (page_has_private(page)) {
466 if (try_to_free_buffers(page)) {
467 ClearPageDirty(page);
468 printk("%s: orphaned page\n", __func__);
469 return PAGE_CLEAN;
470 }
471 }
472 return PAGE_KEEP;
473 }
474 if (mapping->a_ops->writepage == NULL)
475 return PAGE_ACTIVATE;
476 if (!may_write_to_queue(mapping->backing_dev_info, sc))
477 return PAGE_KEEP;
478
479 if (clear_page_dirty_for_io(page)) {
480 int res;
481 struct writeback_control wbc = {
482 .sync_mode = WB_SYNC_NONE,
483 .nr_to_write = SWAP_CLUSTER_MAX,
484 .range_start = 0,
485 .range_end = LLONG_MAX,
486 .for_reclaim = 1,
487 };
488
489 SetPageReclaim(page);
490 res = mapping->a_ops->writepage(page, &wbc);
491 if (res < 0)
492 handle_write_error(mapping, page, res);
493 if (res == AOP_WRITEPAGE_ACTIVATE) {
494 ClearPageReclaim(page);
495 return PAGE_ACTIVATE;
496 }
497
498 /*
499 * Wait on writeback if requested to. This happens when
500 * direct reclaiming a large contiguous area and the
501 * first attempt to free a range of pages fails.
502 */
503 if (PageWriteback(page) &&
504 (sc->reclaim_mode & RECLAIM_MODE_SYNC))
505 wait_on_page_writeback(page);
506
507 if (!PageWriteback(page)) {
508 /* synchronous write or broken a_ops? */
509 ClearPageReclaim(page);
510 }
511 trace_mm_vmscan_writepage(page,
512 trace_reclaim_flags(page, sc->reclaim_mode));
513 inc_zone_page_state(page, NR_VMSCAN_WRITE);
514 return PAGE_SUCCESS;
515 }
516
517 return PAGE_CLEAN;
518}
519
520/*
521 * Same as remove_mapping, but if the page is removed from the mapping, it
522 * gets returned with a refcount of 0.
523 */
524static int __remove_mapping(struct address_space *mapping, struct page *page)
525{
526 BUG_ON(!PageLocked(page));
527 BUG_ON(mapping != page_mapping(page));
528
529 spin_lock_irq(&mapping->tree_lock);
530 /*
531 * The non racy check for a busy page.
532 *
533 * Must be careful with the order of the tests. When someone has
534 * a ref to the page, it may be possible that they dirty it then
535 * drop the reference. So if PageDirty is tested before page_count
536 * here, then the following race may occur:
537 *
538 * get_user_pages(&page);
539 * [user mapping goes away]
540 * write_to(page);
541 * !PageDirty(page) [good]
542 * SetPageDirty(page);
543 * put_page(page);
544 * !page_count(page) [good, discard it]
545 *
546 * [oops, our write_to data is lost]
547 *
548 * Reversing the order of the tests ensures such a situation cannot
549 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
550 * load is not satisfied before that of page->_count.
551 *
552 * Note that if SetPageDirty is always performed via set_page_dirty,
553 * and thus under tree_lock, then this ordering is not required.
554 */
555 if (!page_freeze_refs(page, 2))
556 goto cannot_free;
557 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
558 if (unlikely(PageDirty(page))) {
559 page_unfreeze_refs(page, 2);
560 goto cannot_free;
561 }
562
563 if (PageSwapCache(page)) {
564 swp_entry_t swap = { .val = page_private(page) };
565 __delete_from_swap_cache(page);
566 spin_unlock_irq(&mapping->tree_lock);
567 swapcache_free(swap, page);
568 } else {
569 void (*freepage)(struct page *);
570
571 freepage = mapping->a_ops->freepage;
572
573 __delete_from_page_cache(page);
574 spin_unlock_irq(&mapping->tree_lock);
575 mem_cgroup_uncharge_cache_page(page);
576
577 if (freepage != NULL)
578 freepage(page);
579 }
580
581 return 1;
582
583cannot_free:
584 spin_unlock_irq(&mapping->tree_lock);
585 return 0;
586}
587
588/*
589 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
590 * someone else has a ref on the page, abort and return 0. If it was
591 * successfully detached, return 1. Assumes the caller has a single ref on
592 * this page.
593 */
594int remove_mapping(struct address_space *mapping, struct page *page)
595{
596 if (__remove_mapping(mapping, page)) {
597 /*
598 * Unfreezing the refcount with 1 rather than 2 effectively
599 * drops the pagecache ref for us without requiring another
600 * atomic operation.
601 */
602 page_unfreeze_refs(page, 1);
603 return 1;
604 }
605 return 0;
606}
607
608/**
609 * putback_lru_page - put previously isolated page onto appropriate LRU list
610 * @page: page to be put back to appropriate lru list
611 *
612 * Add previously isolated @page to appropriate LRU list.
613 * Page may still be unevictable for other reasons.
614 *
615 * lru_lock must not be held, interrupts must be enabled.
616 */
617void putback_lru_page(struct page *page)
618{
619 int lru;
620 int active = !!TestClearPageActive(page);
621 int was_unevictable = PageUnevictable(page);
622
623 VM_BUG_ON(PageLRU(page));
624
625redo:
626 ClearPageUnevictable(page);
627
628 if (page_evictable(page, NULL)) {
629 /*
630 * For evictable pages, we can use the cache.
631 * In event of a race, worst case is we end up with an
632 * unevictable page on [in]active list.
633 * We know how to handle that.
634 */
635 lru = active + page_lru_base_type(page);
636 lru_cache_add_lru(page, lru);
637 } else {
638 /*
639 * Put unevictable pages directly on zone's unevictable
640 * list.
641 */
642 lru = LRU_UNEVICTABLE;
643 add_page_to_unevictable_list(page);
644 /*
645 * When racing with an mlock clearing (page is
646 * unlocked), make sure that if the other thread does
647 * not observe our setting of PG_lru and fails
648 * isolation, we see PG_mlocked cleared below and move
649 * the page back to the evictable list.
650 *
651 * The other side is TestClearPageMlocked().
652 */
653 smp_mb();
654 }
655
656 /*
657 * page's status can change while we move it among lru. If an evictable
658 * page is on unevictable list, it never be freed. To avoid that,
659 * check after we added it to the list, again.
660 */
661 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
662 if (!isolate_lru_page(page)) {
663 put_page(page);
664 goto redo;
665 }
666 /* This means someone else dropped this page from LRU
667 * So, it will be freed or putback to LRU again. There is
668 * nothing to do here.
669 */
670 }
671
672 if (was_unevictable && lru != LRU_UNEVICTABLE)
673 count_vm_event(UNEVICTABLE_PGRESCUED);
674 else if (!was_unevictable && lru == LRU_UNEVICTABLE)
675 count_vm_event(UNEVICTABLE_PGCULLED);
676
677 put_page(page); /* drop ref from isolate */
678}
679
680enum page_references {
681 PAGEREF_RECLAIM,
682 PAGEREF_RECLAIM_CLEAN,
683 PAGEREF_KEEP,
684 PAGEREF_ACTIVATE,
685};
686
687static enum page_references page_check_references(struct page *page,
688 struct scan_control *sc)
689{
690 int referenced_ptes, referenced_page;
691 unsigned long vm_flags;
692
693 referenced_ptes = page_referenced(page, 1, sc->mem_cgroup, &vm_flags);
694 referenced_page = TestClearPageReferenced(page);
695
696 /* Lumpy reclaim - ignore references */
697 if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM)
698 return PAGEREF_RECLAIM;
699
700 /*
701 * Mlock lost the isolation race with us. Let try_to_unmap()
702 * move the page to the unevictable list.
703 */
704 if (vm_flags & VM_LOCKED)
705 return PAGEREF_RECLAIM;
706
707 if (referenced_ptes) {
708 if (PageAnon(page))
709 return PAGEREF_ACTIVATE;
710 /*
711 * All mapped pages start out with page table
712 * references from the instantiating fault, so we need
713 * to look twice if a mapped file page is used more
714 * than once.
715 *
716 * Mark it and spare it for another trip around the
717 * inactive list. Another page table reference will
718 * lead to its activation.
719 *
720 * Note: the mark is set for activated pages as well
721 * so that recently deactivated but used pages are
722 * quickly recovered.
723 */
724 SetPageReferenced(page);
725
726 if (referenced_page)
727 return PAGEREF_ACTIVATE;
728
729 return PAGEREF_KEEP;
730 }
731
732 /* Reclaim if clean, defer dirty pages to writeback */
733 if (referenced_page && !PageSwapBacked(page))
734 return PAGEREF_RECLAIM_CLEAN;
735
736 return PAGEREF_RECLAIM;
737}
738
739static noinline_for_stack void free_page_list(struct list_head *free_pages)
740{
741 struct pagevec freed_pvec;
742 struct page *page, *tmp;
743
744 pagevec_init(&freed_pvec, 1);
745
746 list_for_each_entry_safe(page, tmp, free_pages, lru) {
747 list_del(&page->lru);
748 if (!pagevec_add(&freed_pvec, page)) {
749 __pagevec_free(&freed_pvec);
750 pagevec_reinit(&freed_pvec);
751 }
752 }
753
754 pagevec_free(&freed_pvec);
755}
756
757/*
758 * shrink_page_list() returns the number of reclaimed pages
759 */
760static unsigned long shrink_page_list(struct list_head *page_list,
761 struct zone *zone,
762 struct scan_control *sc)
763{
764 LIST_HEAD(ret_pages);
765 LIST_HEAD(free_pages);
766 int pgactivate = 0;
767 unsigned long nr_dirty = 0;
768 unsigned long nr_congested = 0;
769 unsigned long nr_reclaimed = 0;
770
771 cond_resched();
772
773 while (!list_empty(page_list)) {
774 enum page_references references;
775 struct address_space *mapping;
776 struct page *page;
777 int may_enter_fs;
778
779 cond_resched();
780
781 page = lru_to_page(page_list);
782 list_del(&page->lru);
783
784 if (!trylock_page(page))
785 goto keep;
786
787 VM_BUG_ON(PageActive(page));
788 VM_BUG_ON(page_zone(page) != zone);
789
790 sc->nr_scanned++;
791
792 if (unlikely(!page_evictable(page, NULL)))
793 goto cull_mlocked;
794
795 if (!sc->may_unmap && page_mapped(page))
796 goto keep_locked;
797
798 /* Double the slab pressure for mapped and swapcache pages */
799 if (page_mapped(page) || PageSwapCache(page))
800 sc->nr_scanned++;
801
802 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
803 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
804
805 if (PageWriteback(page)) {
806 /*
807 * Synchronous reclaim is performed in two passes,
808 * first an asynchronous pass over the list to
809 * start parallel writeback, and a second synchronous
810 * pass to wait for the IO to complete. Wait here
811 * for any page for which writeback has already
812 * started.
813 */
814 if ((sc->reclaim_mode & RECLAIM_MODE_SYNC) &&
815 may_enter_fs)
816 wait_on_page_writeback(page);
817 else {
818 unlock_page(page);
819 goto keep_lumpy;
820 }
821 }
822
823 references = page_check_references(page, sc);
824 switch (references) {
825 case PAGEREF_ACTIVATE:
826 goto activate_locked;
827 case PAGEREF_KEEP:
828 goto keep_locked;
829 case PAGEREF_RECLAIM:
830 case PAGEREF_RECLAIM_CLEAN:
831 ; /* try to reclaim the page below */
832 }
833
834 /*
835 * Anonymous process memory has backing store?
836 * Try to allocate it some swap space here.
837 */
838 if (PageAnon(page) && !PageSwapCache(page)) {
839 if (!(sc->gfp_mask & __GFP_IO))
840 goto keep_locked;
841 if (!add_to_swap(page))
842 goto activate_locked;
843 may_enter_fs = 1;
844 }
845
846 mapping = page_mapping(page);
847
848 /*
849 * The page is mapped into the page tables of one or more
850 * processes. Try to unmap it here.
851 */
852 if (page_mapped(page) && mapping) {
853 switch (try_to_unmap(page, TTU_UNMAP)) {
854 case SWAP_FAIL:
855 goto activate_locked;
856 case SWAP_AGAIN:
857 goto keep_locked;
858 case SWAP_MLOCK:
859 goto cull_mlocked;
860 case SWAP_SUCCESS:
861 ; /* try to free the page below */
862 }
863 }
864
865 if (PageDirty(page)) {
866 nr_dirty++;
867
868 if (references == PAGEREF_RECLAIM_CLEAN)
869 goto keep_locked;
870 if (!may_enter_fs)
871 goto keep_locked;
872 if (!sc->may_writepage)
873 goto keep_locked;
874
875 /* Page is dirty, try to write it out here */
876 switch (pageout(page, mapping, sc)) {
877 case PAGE_KEEP:
878 nr_congested++;
879 goto keep_locked;
880 case PAGE_ACTIVATE:
881 goto activate_locked;
882 case PAGE_SUCCESS:
883 if (PageWriteback(page))
884 goto keep_lumpy;
885 if (PageDirty(page))
886 goto keep;
887
888 /*
889 * A synchronous write - probably a ramdisk. Go
890 * ahead and try to reclaim the page.
891 */
892 if (!trylock_page(page))
893 goto keep;
894 if (PageDirty(page) || PageWriteback(page))
895 goto keep_locked;
896 mapping = page_mapping(page);
897 case PAGE_CLEAN:
898 ; /* try to free the page below */
899 }
900 }
901
902 /*
903 * If the page has buffers, try to free the buffer mappings
904 * associated with this page. If we succeed we try to free
905 * the page as well.
906 *
907 * We do this even if the page is PageDirty().
908 * try_to_release_page() does not perform I/O, but it is
909 * possible for a page to have PageDirty set, but it is actually
910 * clean (all its buffers are clean). This happens if the
911 * buffers were written out directly, with submit_bh(). ext3
912 * will do this, as well as the blockdev mapping.
913 * try_to_release_page() will discover that cleanness and will
914 * drop the buffers and mark the page clean - it can be freed.
915 *
916 * Rarely, pages can have buffers and no ->mapping. These are
917 * the pages which were not successfully invalidated in
918 * truncate_complete_page(). We try to drop those buffers here
919 * and if that worked, and the page is no longer mapped into
920 * process address space (page_count == 1) it can be freed.
921 * Otherwise, leave the page on the LRU so it is swappable.
922 */
923 if (page_has_private(page)) {
924 if (!try_to_release_page(page, sc->gfp_mask))
925 goto activate_locked;
926 if (!mapping && page_count(page) == 1) {
927 unlock_page(page);
928 if (put_page_testzero(page))
929 goto free_it;
930 else {
931 /*
932 * rare race with speculative reference.
933 * the speculative reference will free
934 * this page shortly, so we may
935 * increment nr_reclaimed here (and
936 * leave it off the LRU).
937 */
938 nr_reclaimed++;
939 continue;
940 }
941 }
942 }
943
944 if (!mapping || !__remove_mapping(mapping, page))
945 goto keep_locked;
946
947 /*
948 * At this point, we have no other references and there is
949 * no way to pick any more up (removed from LRU, removed
950 * from pagecache). Can use non-atomic bitops now (and
951 * we obviously don't have to worry about waking up a process
952 * waiting on the page lock, because there are no references.
953 */
954 __clear_page_locked(page);
955free_it:
956 nr_reclaimed++;
957
958 /*
959 * Is there need to periodically free_page_list? It would
960 * appear not as the counts should be low
961 */
962 list_add(&page->lru, &free_pages);
963 continue;
964
965cull_mlocked:
966 if (PageSwapCache(page))
967 try_to_free_swap(page);
968 unlock_page(page);
969 putback_lru_page(page);
970 reset_reclaim_mode(sc);
971 continue;
972
973activate_locked:
974 /* Not a candidate for swapping, so reclaim swap space. */
975 if (PageSwapCache(page) && vm_swap_full())
976 try_to_free_swap(page);
977 VM_BUG_ON(PageActive(page));
978 SetPageActive(page);
979 pgactivate++;
980keep_locked:
981 unlock_page(page);
982keep:
983 reset_reclaim_mode(sc);
984keep_lumpy:
985 list_add(&page->lru, &ret_pages);
986 VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
987 }
988
989 /*
990 * Tag a zone as congested if all the dirty pages encountered were
991 * backed by a congested BDI. In this case, reclaimers should just
992 * back off and wait for congestion to clear because further reclaim
993 * will encounter the same problem
994 */
995 if (nr_dirty && nr_dirty == nr_congested && scanning_global_lru(sc))
996 zone_set_flag(zone, ZONE_CONGESTED);
997
998 free_page_list(&free_pages);
999
1000 list_splice(&ret_pages, page_list);
1001 count_vm_events(PGACTIVATE, pgactivate);
1002 return nr_reclaimed;
1003}
1004
1005/*
1006 * Attempt to remove the specified page from its LRU. Only take this page
1007 * if it is of the appropriate PageActive status. Pages which are being
1008 * freed elsewhere are also ignored.
1009 *
1010 * page: page to consider
1011 * mode: one of the LRU isolation modes defined above
1012 *
1013 * returns 0 on success, -ve errno on failure.
1014 */
1015int __isolate_lru_page(struct page *page, int mode, int file)
1016{
1017 int ret = -EINVAL;
1018
1019 /* Only take pages on the LRU. */
1020 if (!PageLRU(page))
1021 return ret;
1022
1023 /*
1024 * When checking the active state, we need to be sure we are
1025 * dealing with comparible boolean values. Take the logical not
1026 * of each.
1027 */
1028 if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode))
1029 return ret;
1030
1031 if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file)
1032 return ret;
1033
1034 /*
1035 * When this function is being called for lumpy reclaim, we
1036 * initially look into all LRU pages, active, inactive and
1037 * unevictable; only give shrink_page_list evictable pages.
1038 */
1039 if (PageUnevictable(page))
1040 return ret;
1041
1042 ret = -EBUSY;
1043
1044 if (likely(get_page_unless_zero(page))) {
1045 /*
1046 * Be careful not to clear PageLRU until after we're
1047 * sure the page is not being freed elsewhere -- the
1048 * page release code relies on it.
1049 */
1050 ClearPageLRU(page);
1051 ret = 0;
1052 }
1053
1054 return ret;
1055}
1056
1057/*
1058 * zone->lru_lock is heavily contended. Some of the functions that
1059 * shrink the lists perform better by taking out a batch of pages
1060 * and working on them outside the LRU lock.
1061 *
1062 * For pagecache intensive workloads, this function is the hottest
1063 * spot in the kernel (apart from copy_*_user functions).
1064 *
1065 * Appropriate locks must be held before calling this function.
1066 *
1067 * @nr_to_scan: The number of pages to look through on the list.
1068 * @src: The LRU list to pull pages off.
1069 * @dst: The temp list to put pages on to.
1070 * @scanned: The number of pages that were scanned.
1071 * @order: The caller's attempted allocation order
1072 * @mode: One of the LRU isolation modes
1073 * @file: True [1] if isolating file [!anon] pages
1074 *
1075 * returns how many pages were moved onto *@dst.
1076 */
1077static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
1078 struct list_head *src, struct list_head *dst,
1079 unsigned long *scanned, int order, int mode, int file)
1080{
1081 unsigned long nr_taken = 0;
1082 unsigned long nr_lumpy_taken = 0;
1083 unsigned long nr_lumpy_dirty = 0;
1084 unsigned long nr_lumpy_failed = 0;
1085 unsigned long scan;
1086
1087 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
1088 struct page *page;
1089 unsigned long pfn;
1090 unsigned long end_pfn;
1091 unsigned long page_pfn;
1092 int zone_id;
1093
1094 page = lru_to_page(src);
1095 prefetchw_prev_lru_page(page, src, flags);
1096
1097 VM_BUG_ON(!PageLRU(page));
1098
1099 switch (__isolate_lru_page(page, mode, file)) {
1100 case 0:
1101 list_move(&page->lru, dst);
1102 mem_cgroup_del_lru(page);
1103 nr_taken += hpage_nr_pages(page);
1104 break;
1105
1106 case -EBUSY:
1107 /* else it is being freed elsewhere */
1108 list_move(&page->lru, src);
1109 mem_cgroup_rotate_lru_list(page, page_lru(page));
1110 continue;
1111
1112 default:
1113 BUG();
1114 }
1115
1116 if (!order)
1117 continue;
1118
1119 /*
1120 * Attempt to take all pages in the order aligned region
1121 * surrounding the tag page. Only take those pages of
1122 * the same active state as that tag page. We may safely
1123 * round the target page pfn down to the requested order
1124 * as the mem_map is guaranteed valid out to MAX_ORDER,
1125 * where that page is in a different zone we will detect
1126 * it from its zone id and abort this block scan.
1127 */
1128 zone_id = page_zone_id(page);
1129 page_pfn = page_to_pfn(page);
1130 pfn = page_pfn & ~((1 << order) - 1);
1131 end_pfn = pfn + (1 << order);
1132 for (; pfn < end_pfn; pfn++) {
1133 struct page *cursor_page;
1134
1135 /* The target page is in the block, ignore it. */
1136 if (unlikely(pfn == page_pfn))
1137 continue;
1138
1139 /* Avoid holes within the zone. */
1140 if (unlikely(!pfn_valid_within(pfn)))
1141 break;
1142
1143 cursor_page = pfn_to_page(pfn);
1144
1145 /* Check that we have not crossed a zone boundary. */
1146 if (unlikely(page_zone_id(cursor_page) != zone_id))
1147 break;
1148
1149 /*
1150 * If we don't have enough swap space, reclaiming of
1151 * anon page which don't already have a swap slot is
1152 * pointless.
1153 */
1154 if (nr_swap_pages <= 0 && PageAnon(cursor_page) &&
1155 !PageSwapCache(cursor_page))
1156 break;
1157
1158 if (__isolate_lru_page(cursor_page, mode, file) == 0) {
1159 list_move(&cursor_page->lru, dst);
1160 mem_cgroup_del_lru(cursor_page);
1161 nr_taken += hpage_nr_pages(page);
1162 nr_lumpy_taken++;
1163 if (PageDirty(cursor_page))
1164 nr_lumpy_dirty++;
1165 scan++;
1166 } else {
1167 /*
1168 * Check if the page is freed already.
1169 *
1170 * We can't use page_count() as that
1171 * requires compound_head and we don't
1172 * have a pin on the page here. If a
1173 * page is tail, we may or may not
1174 * have isolated the head, so assume
1175 * it's not free, it'd be tricky to
1176 * track the head status without a
1177 * page pin.
1178 */
1179 if (!PageTail(cursor_page) &&
1180 !atomic_read(&cursor_page->_count))
1181 continue;
1182 break;
1183 }
1184 }
1185
1186 /* If we break out of the loop above, lumpy reclaim failed */
1187 if (pfn < end_pfn)
1188 nr_lumpy_failed++;
1189 }
1190
1191 *scanned = scan;
1192
1193 trace_mm_vmscan_lru_isolate(order,
1194 nr_to_scan, scan,
1195 nr_taken,
1196 nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed,
1197 mode);
1198 return nr_taken;
1199}
1200
1201static unsigned long isolate_pages_global(unsigned long nr,
1202 struct list_head *dst,
1203 unsigned long *scanned, int order,
1204 int mode, struct zone *z,
1205 int active, int file)
1206{
1207 int lru = LRU_BASE;
1208 if (active)
1209 lru += LRU_ACTIVE;
1210 if (file)
1211 lru += LRU_FILE;
1212 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
1213 mode, file);
1214}
1215
1216/*
1217 * clear_active_flags() is a helper for shrink_active_list(), clearing
1218 * any active bits from the pages in the list.
1219 */
1220static unsigned long clear_active_flags(struct list_head *page_list,
1221 unsigned int *count)
1222{
1223 int nr_active = 0;
1224 int lru;
1225 struct page *page;
1226
1227 list_for_each_entry(page, page_list, lru) {
1228 int numpages = hpage_nr_pages(page);
1229 lru = page_lru_base_type(page);
1230 if (PageActive(page)) {
1231 lru += LRU_ACTIVE;
1232 ClearPageActive(page);
1233 nr_active += numpages;
1234 }
1235 if (count)
1236 count[lru] += numpages;
1237 }
1238
1239 return nr_active;
1240}
1241
1242/**
1243 * isolate_lru_page - tries to isolate a page from its LRU list
1244 * @page: page to isolate from its LRU list
1245 *
1246 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1247 * vmstat statistic corresponding to whatever LRU list the page was on.
1248 *
1249 * Returns 0 if the page was removed from an LRU list.
1250 * Returns -EBUSY if the page was not on an LRU list.
1251 *
1252 * The returned page will have PageLRU() cleared. If it was found on
1253 * the active list, it will have PageActive set. If it was found on
1254 * the unevictable list, it will have the PageUnevictable bit set. That flag
1255 * may need to be cleared by the caller before letting the page go.
1256 *
1257 * The vmstat statistic corresponding to the list on which the page was
1258 * found will be decremented.
1259 *
1260 * Restrictions:
1261 * (1) Must be called with an elevated refcount on the page. This is a
1262 * fundamentnal difference from isolate_lru_pages (which is called
1263 * without a stable reference).
1264 * (2) the lru_lock must not be held.
1265 * (3) interrupts must be enabled.
1266 */
1267int isolate_lru_page(struct page *page)
1268{
1269 int ret = -EBUSY;
1270
1271 VM_BUG_ON(!page_count(page));
1272
1273 if (PageLRU(page)) {
1274 struct zone *zone = page_zone(page);
1275
1276 spin_lock_irq(&zone->lru_lock);
1277 if (PageLRU(page)) {
1278 int lru = page_lru(page);
1279 ret = 0;
1280 get_page(page);
1281 ClearPageLRU(page);
1282
1283 del_page_from_lru_list(zone, page, lru);
1284 }
1285 spin_unlock_irq(&zone->lru_lock);
1286 }
1287 return ret;
1288}
1289
1290/*
1291 * Are there way too many processes in the direct reclaim path already?
1292 */
1293static int too_many_isolated(struct zone *zone, int file,
1294 struct scan_control *sc)
1295{
1296 unsigned long inactive, isolated;
1297
1298 if (current_is_kswapd())
1299 return 0;
1300
1301 if (!scanning_global_lru(sc))
1302 return 0;
1303
1304 if (file) {
1305 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1306 isolated = zone_page_state(zone, NR_ISOLATED_FILE);
1307 } else {
1308 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1309 isolated = zone_page_state(zone, NR_ISOLATED_ANON);
1310 }
1311
1312 return isolated > inactive;
1313}
1314
1315/*
1316 * TODO: Try merging with migrations version of putback_lru_pages
1317 */
1318static noinline_for_stack void
1319putback_lru_pages(struct zone *zone, struct scan_control *sc,
1320 unsigned long nr_anon, unsigned long nr_file,
1321 struct list_head *page_list)
1322{
1323 struct page *page;
1324 struct pagevec pvec;
1325 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1326
1327 pagevec_init(&pvec, 1);
1328
1329 /*
1330 * Put back any unfreeable pages.
1331 */
1332 spin_lock(&zone->lru_lock);
1333 while (!list_empty(page_list)) {
1334 int lru;
1335 page = lru_to_page(page_list);
1336 VM_BUG_ON(PageLRU(page));
1337 list_del(&page->lru);
1338 if (unlikely(!page_evictable(page, NULL))) {
1339 spin_unlock_irq(&zone->lru_lock);
1340 putback_lru_page(page);
1341 spin_lock_irq(&zone->lru_lock);
1342 continue;
1343 }
1344 SetPageLRU(page);
1345 lru = page_lru(page);
1346 add_page_to_lru_list(zone, page, lru);
1347 if (is_active_lru(lru)) {
1348 int file = is_file_lru(lru);
1349 int numpages = hpage_nr_pages(page);
1350 reclaim_stat->recent_rotated[file] += numpages;
1351 }
1352 if (!pagevec_add(&pvec, page)) {
1353 spin_unlock_irq(&zone->lru_lock);
1354 __pagevec_release(&pvec);
1355 spin_lock_irq(&zone->lru_lock);
1356 }
1357 }
1358 __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
1359 __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
1360
1361 spin_unlock_irq(&zone->lru_lock);
1362 pagevec_release(&pvec);
1363}
1364
1365static noinline_for_stack void update_isolated_counts(struct zone *zone,
1366 struct scan_control *sc,
1367 unsigned long *nr_anon,
1368 unsigned long *nr_file,
1369 struct list_head *isolated_list)
1370{
1371 unsigned long nr_active;
1372 unsigned int count[NR_LRU_LISTS] = { 0, };
1373 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1374
1375 nr_active = clear_active_flags(isolated_list, count);
1376 __count_vm_events(PGDEACTIVATE, nr_active);
1377
1378 __mod_zone_page_state(zone, NR_ACTIVE_FILE,
1379 -count[LRU_ACTIVE_FILE]);
1380 __mod_zone_page_state(zone, NR_INACTIVE_FILE,
1381 -count[LRU_INACTIVE_FILE]);
1382 __mod_zone_page_state(zone, NR_ACTIVE_ANON,
1383 -count[LRU_ACTIVE_ANON]);
1384 __mod_zone_page_state(zone, NR_INACTIVE_ANON,
1385 -count[LRU_INACTIVE_ANON]);
1386
1387 *nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
1388 *nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
1389 __mod_zone_page_state(zone, NR_ISOLATED_ANON, *nr_anon);
1390 __mod_zone_page_state(zone, NR_ISOLATED_FILE, *nr_file);
1391
1392 reclaim_stat->recent_scanned[0] += *nr_anon;
1393 reclaim_stat->recent_scanned[1] += *nr_file;
1394}
1395
1396/*
1397 * Returns true if the caller should wait to clean dirty/writeback pages.
1398 *
1399 * If we are direct reclaiming for contiguous pages and we do not reclaim
1400 * everything in the list, try again and wait for writeback IO to complete.
1401 * This will stall high-order allocations noticeably. Only do that when really
1402 * need to free the pages under high memory pressure.
1403 */
1404static inline bool should_reclaim_stall(unsigned long nr_taken,
1405 unsigned long nr_freed,
1406 int priority,
1407 struct scan_control *sc)
1408{
1409 int lumpy_stall_priority;
1410
1411 /* kswapd should not stall on sync IO */
1412 if (current_is_kswapd())
1413 return false;
1414
1415 /* Only stall on lumpy reclaim */
1416 if (sc->reclaim_mode & RECLAIM_MODE_SINGLE)
1417 return false;
1418
1419 /* If we have relaimed everything on the isolated list, no stall */
1420 if (nr_freed == nr_taken)
1421 return false;
1422
1423 /*
1424 * For high-order allocations, there are two stall thresholds.
1425 * High-cost allocations stall immediately where as lower
1426 * order allocations such as stacks require the scanning
1427 * priority to be much higher before stalling.
1428 */
1429 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
1430 lumpy_stall_priority = DEF_PRIORITY;
1431 else
1432 lumpy_stall_priority = DEF_PRIORITY / 3;
1433
1434 return priority <= lumpy_stall_priority;
1435}
1436
1437/*
1438 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1439 * of reclaimed pages
1440 */
1441static noinline_for_stack unsigned long
1442shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
1443 struct scan_control *sc, int priority, int file)
1444{
1445 LIST_HEAD(page_list);
1446 unsigned long nr_scanned;
1447 unsigned long nr_reclaimed = 0;
1448 unsigned long nr_taken;
1449 unsigned long nr_anon;
1450 unsigned long nr_file;
1451
1452 while (unlikely(too_many_isolated(zone, file, sc))) {
1453 congestion_wait(BLK_RW_ASYNC, HZ/10);
1454
1455 /* We are about to die and free our memory. Return now. */
1456 if (fatal_signal_pending(current))
1457 return SWAP_CLUSTER_MAX;
1458 }
1459
1460 set_reclaim_mode(priority, sc, false);
1461 lru_add_drain();
1462 spin_lock_irq(&zone->lru_lock);
1463
1464 if (scanning_global_lru(sc)) {
1465 nr_taken = isolate_pages_global(nr_to_scan,
1466 &page_list, &nr_scanned, sc->order,
1467 sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ?
1468 ISOLATE_BOTH : ISOLATE_INACTIVE,
1469 zone, 0, file);
1470 zone->pages_scanned += nr_scanned;
1471 if (current_is_kswapd())
1472 __count_zone_vm_events(PGSCAN_KSWAPD, zone,
1473 nr_scanned);
1474 else
1475 __count_zone_vm_events(PGSCAN_DIRECT, zone,
1476 nr_scanned);
1477 } else {
1478 nr_taken = mem_cgroup_isolate_pages(nr_to_scan,
1479 &page_list, &nr_scanned, sc->order,
1480 sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ?
1481 ISOLATE_BOTH : ISOLATE_INACTIVE,
1482 zone, sc->mem_cgroup,
1483 0, file);
1484 /*
1485 * mem_cgroup_isolate_pages() keeps track of
1486 * scanned pages on its own.
1487 */
1488 }
1489
1490 if (nr_taken == 0) {
1491 spin_unlock_irq(&zone->lru_lock);
1492 return 0;
1493 }
1494
1495 update_isolated_counts(zone, sc, &nr_anon, &nr_file, &page_list);
1496
1497 spin_unlock_irq(&zone->lru_lock);
1498
1499 nr_reclaimed = shrink_page_list(&page_list, zone, sc);
1500
1501 /* Check if we should syncronously wait for writeback */
1502 if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) {
1503 set_reclaim_mode(priority, sc, true);
1504 nr_reclaimed += shrink_page_list(&page_list, zone, sc);
1505 }
1506
1507 local_irq_disable();
1508 if (current_is_kswapd())
1509 __count_vm_events(KSWAPD_STEAL, nr_reclaimed);
1510 __count_zone_vm_events(PGSTEAL, zone, nr_reclaimed);
1511
1512 putback_lru_pages(zone, sc, nr_anon, nr_file, &page_list);
1513
1514 trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id,
1515 zone_idx(zone),
1516 nr_scanned, nr_reclaimed,
1517 priority,
1518 trace_shrink_flags(file, sc->reclaim_mode));
1519 return nr_reclaimed;
1520}
1521
1522/*
1523 * This moves pages from the active list to the inactive list.
1524 *
1525 * We move them the other way if the page is referenced by one or more
1526 * processes, from rmap.
1527 *
1528 * If the pages are mostly unmapped, the processing is fast and it is
1529 * appropriate to hold zone->lru_lock across the whole operation. But if
1530 * the pages are mapped, the processing is slow (page_referenced()) so we
1531 * should drop zone->lru_lock around each page. It's impossible to balance
1532 * this, so instead we remove the pages from the LRU while processing them.
1533 * It is safe to rely on PG_active against the non-LRU pages in here because
1534 * nobody will play with that bit on a non-LRU page.
1535 *
1536 * The downside is that we have to touch page->_count against each page.
1537 * But we had to alter page->flags anyway.
1538 */
1539
1540static void move_active_pages_to_lru(struct zone *zone,
1541 struct list_head *list,
1542 enum lru_list lru)
1543{
1544 unsigned long pgmoved = 0;
1545 struct pagevec pvec;
1546 struct page *page;
1547
1548 pagevec_init(&pvec, 1);
1549
1550 while (!list_empty(list)) {
1551 page = lru_to_page(list);
1552
1553 VM_BUG_ON(PageLRU(page));
1554 SetPageLRU(page);
1555
1556 list_move(&page->lru, &zone->lru[lru].list);
1557 mem_cgroup_add_lru_list(page, lru);
1558 pgmoved += hpage_nr_pages(page);
1559
1560 if (!pagevec_add(&pvec, page) || list_empty(list)) {
1561 spin_unlock_irq(&zone->lru_lock);
1562 if (buffer_heads_over_limit)
1563 pagevec_strip(&pvec);
1564 __pagevec_release(&pvec);
1565 spin_lock_irq(&zone->lru_lock);
1566 }
1567 }
1568 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1569 if (!is_active_lru(lru))
1570 __count_vm_events(PGDEACTIVATE, pgmoved);
1571}
1572
1573static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1574 struct scan_control *sc, int priority, int file)
1575{
1576 unsigned long nr_taken;
1577 unsigned long pgscanned;
1578 unsigned long vm_flags;
1579 LIST_HEAD(l_hold); /* The pages which were snipped off */
1580 LIST_HEAD(l_active);
1581 LIST_HEAD(l_inactive);
1582 struct page *page;
1583 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1584 unsigned long nr_rotated = 0;
1585
1586 lru_add_drain();
1587 spin_lock_irq(&zone->lru_lock);
1588 if (scanning_global_lru(sc)) {
1589 nr_taken = isolate_pages_global(nr_pages, &l_hold,
1590 &pgscanned, sc->order,
1591 ISOLATE_ACTIVE, zone,
1592 1, file);
1593 zone->pages_scanned += pgscanned;
1594 } else {
1595 nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold,
1596 &pgscanned, sc->order,
1597 ISOLATE_ACTIVE, zone,
1598 sc->mem_cgroup, 1, file);
1599 /*
1600 * mem_cgroup_isolate_pages() keeps track of
1601 * scanned pages on its own.
1602 */
1603 }
1604
1605 reclaim_stat->recent_scanned[file] += nr_taken;
1606
1607 __count_zone_vm_events(PGREFILL, zone, pgscanned);
1608 if (file)
1609 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken);
1610 else
1611 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken);
1612 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
1613 spin_unlock_irq(&zone->lru_lock);
1614
1615 while (!list_empty(&l_hold)) {
1616 cond_resched();
1617 page = lru_to_page(&l_hold);
1618 list_del(&page->lru);
1619
1620 if (unlikely(!page_evictable(page, NULL))) {
1621 putback_lru_page(page);
1622 continue;
1623 }
1624
1625 if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) {
1626 nr_rotated += hpage_nr_pages(page);
1627 /*
1628 * Identify referenced, file-backed active pages and
1629 * give them one more trip around the active list. So
1630 * that executable code get better chances to stay in
1631 * memory under moderate memory pressure. Anon pages
1632 * are not likely to be evicted by use-once streaming
1633 * IO, plus JVM can create lots of anon VM_EXEC pages,
1634 * so we ignore them here.
1635 */
1636 if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
1637 list_add(&page->lru, &l_active);
1638 continue;
1639 }
1640 }
1641
1642 ClearPageActive(page); /* we are de-activating */
1643 list_add(&page->lru, &l_inactive);
1644 }
1645
1646 /*
1647 * Move pages back to the lru list.
1648 */
1649 spin_lock_irq(&zone->lru_lock);
1650 /*
1651 * Count referenced pages from currently used mappings as rotated,
1652 * even though only some of them are actually re-activated. This
1653 * helps balance scan pressure between file and anonymous pages in
1654 * get_scan_ratio.
1655 */
1656 reclaim_stat->recent_rotated[file] += nr_rotated;
1657
1658 move_active_pages_to_lru(zone, &l_active,
1659 LRU_ACTIVE + file * LRU_FILE);
1660 move_active_pages_to_lru(zone, &l_inactive,
1661 LRU_BASE + file * LRU_FILE);
1662 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1663 spin_unlock_irq(&zone->lru_lock);
1664}
1665
1666#ifdef CONFIG_SWAP
1667static int inactive_anon_is_low_global(struct zone *zone)
1668{
1669 unsigned long active, inactive;
1670
1671 active = zone_page_state(zone, NR_ACTIVE_ANON);
1672 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1673
1674 if (inactive * zone->inactive_ratio < active)
1675 return 1;
1676
1677 return 0;
1678}
1679
1680/**
1681 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1682 * @zone: zone to check
1683 * @sc: scan control of this context
1684 *
1685 * Returns true if the zone does not have enough inactive anon pages,
1686 * meaning some active anon pages need to be deactivated.
1687 */
1688static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc)
1689{
1690 int low;
1691
1692 /*
1693 * If we don't have swap space, anonymous page deactivation
1694 * is pointless.
1695 */
1696 if (!total_swap_pages)
1697 return 0;
1698
1699 if (scanning_global_lru(sc))
1700 low = inactive_anon_is_low_global(zone);
1701 else
1702 low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup);
1703 return low;
1704}
1705#else
1706static inline int inactive_anon_is_low(struct zone *zone,
1707 struct scan_control *sc)
1708{
1709 return 0;
1710}
1711#endif
1712
1713static int inactive_file_is_low_global(struct zone *zone)
1714{
1715 unsigned long active, inactive;
1716
1717 active = zone_page_state(zone, NR_ACTIVE_FILE);
1718 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1719
1720 return (active > inactive);
1721}
1722
1723/**
1724 * inactive_file_is_low - check if file pages need to be deactivated
1725 * @zone: zone to check
1726 * @sc: scan control of this context
1727 *
1728 * When the system is doing streaming IO, memory pressure here
1729 * ensures that active file pages get deactivated, until more
1730 * than half of the file pages are on the inactive list.
1731 *
1732 * Once we get to that situation, protect the system's working
1733 * set from being evicted by disabling active file page aging.
1734 *
1735 * This uses a different ratio than the anonymous pages, because
1736 * the page cache uses a use-once replacement algorithm.
1737 */
1738static int inactive_file_is_low(struct zone *zone, struct scan_control *sc)
1739{
1740 int low;
1741
1742 if (scanning_global_lru(sc))
1743 low = inactive_file_is_low_global(zone);
1744 else
1745 low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup);
1746 return low;
1747}
1748
1749static int inactive_list_is_low(struct zone *zone, struct scan_control *sc,
1750 int file)
1751{
1752 if (file)
1753 return inactive_file_is_low(zone, sc);
1754 else
1755 return inactive_anon_is_low(zone, sc);
1756}
1757
1758static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1759 struct zone *zone, struct scan_control *sc, int priority)
1760{
1761 int file = is_file_lru(lru);
1762
1763 if (is_active_lru(lru)) {
1764 if (inactive_list_is_low(zone, sc, file))
1765 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1766 return 0;
1767 }
1768
1769 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1770}
1771
1772static int vmscan_swappiness(struct scan_control *sc)
1773{
1774 if (scanning_global_lru(sc))
1775 return vm_swappiness;
1776 return mem_cgroup_swappiness(sc->mem_cgroup);
1777}
1778
1779/*
1780 * Determine how aggressively the anon and file LRU lists should be
1781 * scanned. The relative value of each set of LRU lists is determined
1782 * by looking at the fraction of the pages scanned we did rotate back
1783 * onto the active list instead of evict.
1784 *
1785 * nr[0] = anon pages to scan; nr[1] = file pages to scan
1786 */
1787static void get_scan_count(struct zone *zone, struct scan_control *sc,
1788 unsigned long *nr, int priority)
1789{
1790 unsigned long anon, file, free;
1791 unsigned long anon_prio, file_prio;
1792 unsigned long ap, fp;
1793 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1794 u64 fraction[2], denominator;
1795 enum lru_list l;
1796 int noswap = 0;
1797 bool force_scan = false;
1798 unsigned long nr_force_scan[2];
1799
1800 /* kswapd does zone balancing and needs to scan this zone */
1801 if (scanning_global_lru(sc) && current_is_kswapd())
1802 force_scan = true;
1803 /* memcg may have small limit and need to avoid priority drop */
1804 if (!scanning_global_lru(sc))
1805 force_scan = true;
1806
1807 /* If we have no swap space, do not bother scanning anon pages. */
1808 if (!sc->may_swap || (nr_swap_pages <= 0)) {
1809 noswap = 1;
1810 fraction[0] = 0;
1811 fraction[1] = 1;
1812 denominator = 1;
1813 nr_force_scan[0] = 0;
1814 nr_force_scan[1] = SWAP_CLUSTER_MAX;
1815 goto out;
1816 }
1817
1818 anon = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) +
1819 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON);
1820 file = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) +
1821 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
1822
1823 if (scanning_global_lru(sc)) {
1824 free = zone_page_state(zone, NR_FREE_PAGES);
1825 /* If we have very few page cache pages,
1826 force-scan anon pages. */
1827 if (unlikely(file + free <= high_wmark_pages(zone))) {
1828 fraction[0] = 1;
1829 fraction[1] = 0;
1830 denominator = 1;
1831 nr_force_scan[0] = SWAP_CLUSTER_MAX;
1832 nr_force_scan[1] = 0;
1833 goto out;
1834 }
1835 }
1836
1837 /*
1838 * With swappiness at 100, anonymous and file have the same priority.
1839 * This scanning priority is essentially the inverse of IO cost.
1840 */
1841 anon_prio = vmscan_swappiness(sc);
1842 file_prio = 200 - vmscan_swappiness(sc);
1843
1844 /*
1845 * OK, so we have swap space and a fair amount of page cache
1846 * pages. We use the recently rotated / recently scanned
1847 * ratios to determine how valuable each cache is.
1848 *
1849 * Because workloads change over time (and to avoid overflow)
1850 * we keep these statistics as a floating average, which ends
1851 * up weighing recent references more than old ones.
1852 *
1853 * anon in [0], file in [1]
1854 */
1855 spin_lock_irq(&zone->lru_lock);
1856 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
1857 reclaim_stat->recent_scanned[0] /= 2;
1858 reclaim_stat->recent_rotated[0] /= 2;
1859 }
1860
1861 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
1862 reclaim_stat->recent_scanned[1] /= 2;
1863 reclaim_stat->recent_rotated[1] /= 2;
1864 }
1865
1866 /*
1867 * The amount of pressure on anon vs file pages is inversely
1868 * proportional to the fraction of recently scanned pages on
1869 * each list that were recently referenced and in active use.
1870 */
1871 ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
1872 ap /= reclaim_stat->recent_rotated[0] + 1;
1873
1874 fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
1875 fp /= reclaim_stat->recent_rotated[1] + 1;
1876 spin_unlock_irq(&zone->lru_lock);
1877
1878 fraction[0] = ap;
1879 fraction[1] = fp;
1880 denominator = ap + fp + 1;
1881 if (force_scan) {
1882 unsigned long scan = SWAP_CLUSTER_MAX;
1883 nr_force_scan[0] = div64_u64(scan * ap, denominator);
1884 nr_force_scan[1] = div64_u64(scan * fp, denominator);
1885 }
1886out:
1887 for_each_evictable_lru(l) {
1888 int file = is_file_lru(l);
1889 unsigned long scan;
1890
1891 scan = zone_nr_lru_pages(zone, sc, l);
1892 if (priority || noswap) {
1893 scan >>= priority;
1894 scan = div64_u64(scan * fraction[file], denominator);
1895 }
1896
1897 /*
1898 * If zone is small or memcg is small, nr[l] can be 0.
1899 * This results no-scan on this priority and priority drop down.
1900 * For global direct reclaim, it can visit next zone and tend
1901 * not to have problems. For global kswapd, it's for zone
1902 * balancing and it need to scan a small amounts. When using
1903 * memcg, priority drop can cause big latency. So, it's better
1904 * to scan small amount. See may_noscan above.
1905 */
1906 if (!scan && force_scan)
1907 scan = nr_force_scan[file];
1908 nr[l] = scan;
1909 }
1910}
1911
1912/*
1913 * Reclaim/compaction depends on a number of pages being freed. To avoid
1914 * disruption to the system, a small number of order-0 pages continue to be
1915 * rotated and reclaimed in the normal fashion. However, by the time we get
1916 * back to the allocator and call try_to_compact_zone(), we ensure that
1917 * there are enough free pages for it to be likely successful
1918 */
1919static inline bool should_continue_reclaim(struct zone *zone,
1920 unsigned long nr_reclaimed,
1921 unsigned long nr_scanned,
1922 struct scan_control *sc)
1923{
1924 unsigned long pages_for_compaction;
1925 unsigned long inactive_lru_pages;
1926
1927 /* If not in reclaim/compaction mode, stop */
1928 if (!(sc->reclaim_mode & RECLAIM_MODE_COMPACTION))
1929 return false;
1930
1931 /* Consider stopping depending on scan and reclaim activity */
1932 if (sc->gfp_mask & __GFP_REPEAT) {
1933 /*
1934 * For __GFP_REPEAT allocations, stop reclaiming if the
1935 * full LRU list has been scanned and we are still failing
1936 * to reclaim pages. This full LRU scan is potentially
1937 * expensive but a __GFP_REPEAT caller really wants to succeed
1938 */
1939 if (!nr_reclaimed && !nr_scanned)
1940 return false;
1941 } else {
1942 /*
1943 * For non-__GFP_REPEAT allocations which can presumably
1944 * fail without consequence, stop if we failed to reclaim
1945 * any pages from the last SWAP_CLUSTER_MAX number of
1946 * pages that were scanned. This will return to the
1947 * caller faster at the risk reclaim/compaction and
1948 * the resulting allocation attempt fails
1949 */
1950 if (!nr_reclaimed)
1951 return false;
1952 }
1953
1954 /*
1955 * If we have not reclaimed enough pages for compaction and the
1956 * inactive lists are large enough, continue reclaiming
1957 */
1958 pages_for_compaction = (2UL << sc->order);
1959 inactive_lru_pages = zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON) +
1960 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
1961 if (sc->nr_reclaimed < pages_for_compaction &&
1962 inactive_lru_pages > pages_for_compaction)
1963 return true;
1964
1965 /* If compaction would go ahead or the allocation would succeed, stop */
1966 switch (compaction_suitable(zone, sc->order)) {
1967 case COMPACT_PARTIAL:
1968 case COMPACT_CONTINUE:
1969 return false;
1970 default:
1971 return true;
1972 }
1973}
1974
1975/*
1976 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1977 */
1978static void shrink_zone(int priority, struct zone *zone,
1979 struct scan_control *sc)
1980{
1981 unsigned long nr[NR_LRU_LISTS];
1982 unsigned long nr_to_scan;
1983 enum lru_list l;
1984 unsigned long nr_reclaimed, nr_scanned;
1985 unsigned long nr_to_reclaim = sc->nr_to_reclaim;
1986
1987restart:
1988 nr_reclaimed = 0;
1989 nr_scanned = sc->nr_scanned;
1990 get_scan_count(zone, sc, nr, priority);
1991
1992 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
1993 nr[LRU_INACTIVE_FILE]) {
1994 for_each_evictable_lru(l) {
1995 if (nr[l]) {
1996 nr_to_scan = min_t(unsigned long,
1997 nr[l], SWAP_CLUSTER_MAX);
1998 nr[l] -= nr_to_scan;
1999
2000 nr_reclaimed += shrink_list(l, nr_to_scan,
2001 zone, sc, priority);
2002 }
2003 }
2004 /*
2005 * On large memory systems, scan >> priority can become
2006 * really large. This is fine for the starting priority;
2007 * we want to put equal scanning pressure on each zone.
2008 * However, if the VM has a harder time of freeing pages,
2009 * with multiple processes reclaiming pages, the total
2010 * freeing target can get unreasonably large.
2011 */
2012 if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY)
2013 break;
2014 }
2015 sc->nr_reclaimed += nr_reclaimed;
2016
2017 /*
2018 * Even if we did not try to evict anon pages at all, we want to
2019 * rebalance the anon lru active/inactive ratio.
2020 */
2021 if (inactive_anon_is_low(zone, sc))
2022 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
2023
2024 /* reclaim/compaction might need reclaim to continue */
2025 if (should_continue_reclaim(zone, nr_reclaimed,
2026 sc->nr_scanned - nr_scanned, sc))
2027 goto restart;
2028
2029 throttle_vm_writeout(sc->gfp_mask);
2030}
2031
2032/*
2033 * This is the direct reclaim path, for page-allocating processes. We only
2034 * try to reclaim pages from zones which will satisfy the caller's allocation
2035 * request.
2036 *
2037 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
2038 * Because:
2039 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
2040 * allocation or
2041 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
2042 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
2043 * zone defense algorithm.
2044 *
2045 * If a zone is deemed to be full of pinned pages then just give it a light
2046 * scan then give up on it.
2047 */
2048static void shrink_zones(int priority, struct zonelist *zonelist,
2049 struct scan_control *sc)
2050{
2051 struct zoneref *z;
2052 struct zone *zone;
2053 unsigned long nr_soft_reclaimed;
2054 unsigned long nr_soft_scanned;
2055
2056 for_each_zone_zonelist_nodemask(zone, z, zonelist,
2057 gfp_zone(sc->gfp_mask), sc->nodemask) {
2058 if (!populated_zone(zone))
2059 continue;
2060 /*
2061 * Take care memory controller reclaiming has small influence
2062 * to global LRU.
2063 */
2064 if (scanning_global_lru(sc)) {
2065 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2066 continue;
2067 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2068 continue; /* Let kswapd poll it */
2069 /*
2070 * This steals pages from memory cgroups over softlimit
2071 * and returns the number of reclaimed pages and
2072 * scanned pages. This works for global memory pressure
2073 * and balancing, not for a memcg's limit.
2074 */
2075 nr_soft_scanned = 0;
2076 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
2077 sc->order, sc->gfp_mask,
2078 &nr_soft_scanned);
2079 sc->nr_reclaimed += nr_soft_reclaimed;
2080 sc->nr_scanned += nr_soft_scanned;
2081 /* need some check for avoid more shrink_zone() */
2082 }
2083
2084 shrink_zone(priority, zone, sc);
2085 }
2086}
2087
2088static bool zone_reclaimable(struct zone *zone)
2089{
2090 return zone->pages_scanned < zone_reclaimable_pages(zone) * 6;
2091}
2092
2093/* All zones in zonelist are unreclaimable? */
2094static bool all_unreclaimable(struct zonelist *zonelist,
2095 struct scan_control *sc)
2096{
2097 struct zoneref *z;
2098 struct zone *zone;
2099
2100 for_each_zone_zonelist_nodemask(zone, z, zonelist,
2101 gfp_zone(sc->gfp_mask), sc->nodemask) {
2102 if (!populated_zone(zone))
2103 continue;
2104 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2105 continue;
2106 if (!zone->all_unreclaimable)
2107 return false;
2108 }
2109
2110 return true;
2111}
2112
2113/*
2114 * This is the main entry point to direct page reclaim.
2115 *
2116 * If a full scan of the inactive list fails to free enough memory then we
2117 * are "out of memory" and something needs to be killed.
2118 *
2119 * If the caller is !__GFP_FS then the probability of a failure is reasonably
2120 * high - the zone may be full of dirty or under-writeback pages, which this
2121 * caller can't do much about. We kick the writeback threads and take explicit
2122 * naps in the hope that some of these pages can be written. But if the
2123 * allocating task holds filesystem locks which prevent writeout this might not
2124 * work, and the allocation attempt will fail.
2125 *
2126 * returns: 0, if no pages reclaimed
2127 * else, the number of pages reclaimed
2128 */
2129static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
2130 struct scan_control *sc,
2131 struct shrink_control *shrink)
2132{
2133 int priority;
2134 unsigned long total_scanned = 0;
2135 struct reclaim_state *reclaim_state = current->reclaim_state;
2136 struct zoneref *z;
2137 struct zone *zone;
2138 unsigned long writeback_threshold;
2139
2140 get_mems_allowed();
2141 delayacct_freepages_start();
2142
2143 if (scanning_global_lru(sc))
2144 count_vm_event(ALLOCSTALL);
2145
2146 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2147 sc->nr_scanned = 0;
2148 if (!priority)
2149 disable_swap_token(sc->mem_cgroup);
2150 shrink_zones(priority, zonelist, sc);
2151 /*
2152 * Don't shrink slabs when reclaiming memory from
2153 * over limit cgroups
2154 */
2155 if (scanning_global_lru(sc)) {
2156 unsigned long lru_pages = 0;
2157 for_each_zone_zonelist(zone, z, zonelist,
2158 gfp_zone(sc->gfp_mask)) {
2159 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2160 continue;
2161
2162 lru_pages += zone_reclaimable_pages(zone);
2163 }
2164
2165 shrink_slab(shrink, sc->nr_scanned, lru_pages);
2166 if (reclaim_state) {
2167 sc->nr_reclaimed += reclaim_state->reclaimed_slab;
2168 reclaim_state->reclaimed_slab = 0;
2169 }
2170 }
2171 total_scanned += sc->nr_scanned;
2172 if (sc->nr_reclaimed >= sc->nr_to_reclaim)
2173 goto out;
2174
2175 /*
2176 * Try to write back as many pages as we just scanned. This
2177 * tends to cause slow streaming writers to write data to the
2178 * disk smoothly, at the dirtying rate, which is nice. But
2179 * that's undesirable in laptop mode, where we *want* lumpy
2180 * writeout. So in laptop mode, write out the whole world.
2181 */
2182 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
2183 if (total_scanned > writeback_threshold) {
2184 wakeup_flusher_threads(laptop_mode ? 0 : total_scanned);
2185 sc->may_writepage = 1;
2186 }
2187
2188 /* Take a nap, wait for some writeback to complete */
2189 if (!sc->hibernation_mode && sc->nr_scanned &&
2190 priority < DEF_PRIORITY - 2) {
2191 struct zone *preferred_zone;
2192
2193 first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask),
2194 &cpuset_current_mems_allowed,
2195 &preferred_zone);
2196 wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10);
2197 }
2198 }
2199
2200out:
2201 delayacct_freepages_end();
2202 put_mems_allowed();
2203
2204 if (sc->nr_reclaimed)
2205 return sc->nr_reclaimed;
2206
2207 /*
2208 * As hibernation is going on, kswapd is freezed so that it can't mark
2209 * the zone into all_unreclaimable. Thus bypassing all_unreclaimable
2210 * check.
2211 */
2212 if (oom_killer_disabled)
2213 return 0;
2214
2215 /* top priority shrink_zones still had more to do? don't OOM, then */
2216 if (scanning_global_lru(sc) && !all_unreclaimable(zonelist, sc))
2217 return 1;
2218
2219 return 0;
2220}
2221
2222unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
2223 gfp_t gfp_mask, nodemask_t *nodemask)
2224{
2225 unsigned long nr_reclaimed;
2226 struct scan_control sc = {
2227 .gfp_mask = gfp_mask,
2228 .may_writepage = !laptop_mode,
2229 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2230 .may_unmap = 1,
2231 .may_swap = 1,
2232 .order = order,
2233 .mem_cgroup = NULL,
2234 .nodemask = nodemask,
2235 };
2236 struct shrink_control shrink = {
2237 .gfp_mask = sc.gfp_mask,
2238 };
2239
2240 trace_mm_vmscan_direct_reclaim_begin(order,
2241 sc.may_writepage,
2242 gfp_mask);
2243
2244 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2245
2246 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
2247
2248 return nr_reclaimed;
2249}
2250
2251#ifdef CONFIG_CGROUP_MEM_RES_CTLR
2252
2253unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
2254 gfp_t gfp_mask, bool noswap,
2255 struct zone *zone,
2256 unsigned long *nr_scanned)
2257{
2258 struct scan_control sc = {
2259 .nr_scanned = 0,
2260 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2261 .may_writepage = !laptop_mode,
2262 .may_unmap = 1,
2263 .may_swap = !noswap,
2264 .order = 0,
2265 .mem_cgroup = mem,
2266 };
2267
2268 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2269 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
2270
2271 trace_mm_vmscan_memcg_softlimit_reclaim_begin(0,
2272 sc.may_writepage,
2273 sc.gfp_mask);
2274
2275 /*
2276 * NOTE: Although we can get the priority field, using it
2277 * here is not a good idea, since it limits the pages we can scan.
2278 * if we don't reclaim here, the shrink_zone from balance_pgdat
2279 * will pick up pages from other mem cgroup's as well. We hack
2280 * the priority and make it zero.
2281 */
2282 shrink_zone(0, zone, &sc);
2283
2284 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
2285
2286 *nr_scanned = sc.nr_scanned;
2287 return sc.nr_reclaimed;
2288}
2289
2290unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
2291 gfp_t gfp_mask,
2292 bool noswap)
2293{
2294 struct zonelist *zonelist;
2295 unsigned long nr_reclaimed;
2296 int nid;
2297 struct scan_control sc = {
2298 .may_writepage = !laptop_mode,
2299 .may_unmap = 1,
2300 .may_swap = !noswap,
2301 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2302 .order = 0,
2303 .mem_cgroup = mem_cont,
2304 .nodemask = NULL, /* we don't care the placement */
2305 .gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2306 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
2307 };
2308 struct shrink_control shrink = {
2309 .gfp_mask = sc.gfp_mask,
2310 };
2311
2312 /*
2313 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
2314 * take care of from where we get pages. So the node where we start the
2315 * scan does not need to be the current node.
2316 */
2317 nid = mem_cgroup_select_victim_node(mem_cont);
2318
2319 zonelist = NODE_DATA(nid)->node_zonelists;
2320
2321 trace_mm_vmscan_memcg_reclaim_begin(0,
2322 sc.may_writepage,
2323 sc.gfp_mask);
2324
2325 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2326
2327 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
2328
2329 return nr_reclaimed;
2330}
2331#endif
2332
2333/*
2334 * pgdat_balanced is used when checking if a node is balanced for high-order
2335 * allocations. Only zones that meet watermarks and are in a zone allowed
2336 * by the callers classzone_idx are added to balanced_pages. The total of
2337 * balanced pages must be at least 25% of the zones allowed by classzone_idx
2338 * for the node to be considered balanced. Forcing all zones to be balanced
2339 * for high orders can cause excessive reclaim when there are imbalanced zones.
2340 * The choice of 25% is due to
2341 * o a 16M DMA zone that is balanced will not balance a zone on any
2342 * reasonable sized machine
2343 * o On all other machines, the top zone must be at least a reasonable
2344 * percentage of the middle zones. For example, on 32-bit x86, highmem
2345 * would need to be at least 256M for it to be balance a whole node.
2346 * Similarly, on x86-64 the Normal zone would need to be at least 1G
2347 * to balance a node on its own. These seemed like reasonable ratios.
2348 */
2349static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages,
2350 int classzone_idx)
2351{
2352 unsigned long present_pages = 0;
2353 int i;
2354
2355 for (i = 0; i <= classzone_idx; i++)
2356 present_pages += pgdat->node_zones[i].present_pages;
2357
2358 /* A special case here: if zone has no page, we think it's balanced */
2359 return balanced_pages >= (present_pages >> 2);
2360}
2361
2362/* is kswapd sleeping prematurely? */
2363static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining,
2364 int classzone_idx)
2365{
2366 int i;
2367 unsigned long balanced = 0;
2368 bool all_zones_ok = true;
2369
2370 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
2371 if (remaining)
2372 return true;
2373
2374 /* Check the watermark levels */
2375 for (i = 0; i <= classzone_idx; i++) {
2376 struct zone *zone = pgdat->node_zones + i;
2377
2378 if (!populated_zone(zone))
2379 continue;
2380
2381 /*
2382 * balance_pgdat() skips over all_unreclaimable after
2383 * DEF_PRIORITY. Effectively, it considers them balanced so
2384 * they must be considered balanced here as well if kswapd
2385 * is to sleep
2386 */
2387 if (zone->all_unreclaimable) {
2388 balanced += zone->present_pages;
2389 continue;
2390 }
2391
2392 if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone),
2393 i, 0))
2394 all_zones_ok = false;
2395 else
2396 balanced += zone->present_pages;
2397 }
2398
2399 /*
2400 * For high-order requests, the balanced zones must contain at least
2401 * 25% of the nodes pages for kswapd to sleep. For order-0, all zones
2402 * must be balanced
2403 */
2404 if (order)
2405 return !pgdat_balanced(pgdat, balanced, classzone_idx);
2406 else
2407 return !all_zones_ok;
2408}
2409
2410/*
2411 * For kswapd, balance_pgdat() will work across all this node's zones until
2412 * they are all at high_wmark_pages(zone).
2413 *
2414 * Returns the final order kswapd was reclaiming at
2415 *
2416 * There is special handling here for zones which are full of pinned pages.
2417 * This can happen if the pages are all mlocked, or if they are all used by
2418 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
2419 * What we do is to detect the case where all pages in the zone have been
2420 * scanned twice and there has been zero successful reclaim. Mark the zone as
2421 * dead and from now on, only perform a short scan. Basically we're polling
2422 * the zone for when the problem goes away.
2423 *
2424 * kswapd scans the zones in the highmem->normal->dma direction. It skips
2425 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
2426 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
2427 * lower zones regardless of the number of free pages in the lower zones. This
2428 * interoperates with the page allocator fallback scheme to ensure that aging
2429 * of pages is balanced across the zones.
2430 */
2431static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
2432 int *classzone_idx)
2433{
2434 int all_zones_ok;
2435 unsigned long balanced;
2436 int priority;
2437 int i;
2438 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
2439 unsigned long total_scanned;
2440 struct reclaim_state *reclaim_state = current->reclaim_state;
2441 unsigned long nr_soft_reclaimed;
2442 unsigned long nr_soft_scanned;
2443 struct scan_control sc = {
2444 .gfp_mask = GFP_KERNEL,
2445 .may_unmap = 1,
2446 .may_swap = 1,
2447 /*
2448 * kswapd doesn't want to be bailed out while reclaim. because
2449 * we want to put equal scanning pressure on each zone.
2450 */
2451 .nr_to_reclaim = ULONG_MAX,
2452 .order = order,
2453 .mem_cgroup = NULL,
2454 };
2455 struct shrink_control shrink = {
2456 .gfp_mask = sc.gfp_mask,
2457 };
2458loop_again:
2459 total_scanned = 0;
2460 sc.nr_reclaimed = 0;
2461 sc.may_writepage = !laptop_mode;
2462 count_vm_event(PAGEOUTRUN);
2463
2464 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2465 unsigned long lru_pages = 0;
2466 int has_under_min_watermark_zone = 0;
2467
2468 /* The swap token gets in the way of swapout... */
2469 if (!priority)
2470 disable_swap_token(NULL);
2471
2472 all_zones_ok = 1;
2473 balanced = 0;
2474
2475 /*
2476 * Scan in the highmem->dma direction for the highest
2477 * zone which needs scanning
2478 */
2479 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
2480 struct zone *zone = pgdat->node_zones + i;
2481
2482 if (!populated_zone(zone))
2483 continue;
2484
2485 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2486 continue;
2487
2488 /*
2489 * Do some background aging of the anon list, to give
2490 * pages a chance to be referenced before reclaiming.
2491 */
2492 if (inactive_anon_is_low(zone, &sc))
2493 shrink_active_list(SWAP_CLUSTER_MAX, zone,
2494 &sc, priority, 0);
2495
2496 if (!zone_watermark_ok_safe(zone, order,
2497 high_wmark_pages(zone), 0, 0)) {
2498 end_zone = i;
2499 break;
2500 } else {
2501 /* If balanced, clear the congested flag */
2502 zone_clear_flag(zone, ZONE_CONGESTED);
2503 }
2504 }
2505 if (i < 0)
2506 goto out;
2507
2508 for (i = 0; i <= end_zone; i++) {
2509 struct zone *zone = pgdat->node_zones + i;
2510
2511 lru_pages += zone_reclaimable_pages(zone);
2512 }
2513
2514 /*
2515 * Now scan the zone in the dma->highmem direction, stopping
2516 * at the last zone which needs scanning.
2517 *
2518 * We do this because the page allocator works in the opposite
2519 * direction. This prevents the page allocator from allocating
2520 * pages behind kswapd's direction of progress, which would
2521 * cause too much scanning of the lower zones.
2522 */
2523 for (i = 0; i <= end_zone; i++) {
2524 struct zone *zone = pgdat->node_zones + i;
2525 int nr_slab;
2526 unsigned long balance_gap;
2527
2528 if (!populated_zone(zone))
2529 continue;
2530
2531 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2532 continue;
2533
2534 sc.nr_scanned = 0;
2535
2536 nr_soft_scanned = 0;
2537 /*
2538 * Call soft limit reclaim before calling shrink_zone.
2539 */
2540 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
2541 order, sc.gfp_mask,
2542 &nr_soft_scanned);
2543 sc.nr_reclaimed += nr_soft_reclaimed;
2544 total_scanned += nr_soft_scanned;
2545
2546 /*
2547 * We put equal pressure on every zone, unless
2548 * one zone has way too many pages free
2549 * already. The "too many pages" is defined
2550 * as the high wmark plus a "gap" where the
2551 * gap is either the low watermark or 1%
2552 * of the zone, whichever is smaller.
2553 */
2554 balance_gap = min(low_wmark_pages(zone),
2555 (zone->present_pages +
2556 KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
2557 KSWAPD_ZONE_BALANCE_GAP_RATIO);
2558 if (!zone_watermark_ok_safe(zone, order,
2559 high_wmark_pages(zone) + balance_gap,
2560 end_zone, 0)) {
2561 shrink_zone(priority, zone, &sc);
2562
2563 reclaim_state->reclaimed_slab = 0;
2564 nr_slab = shrink_slab(&shrink, sc.nr_scanned, lru_pages);
2565 sc.nr_reclaimed += reclaim_state->reclaimed_slab;
2566 total_scanned += sc.nr_scanned;
2567
2568 if (nr_slab == 0 && !zone_reclaimable(zone))
2569 zone->all_unreclaimable = 1;
2570 }
2571
2572 /*
2573 * If we've done a decent amount of scanning and
2574 * the reclaim ratio is low, start doing writepage
2575 * even in laptop mode
2576 */
2577 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
2578 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
2579 sc.may_writepage = 1;
2580
2581 if (zone->all_unreclaimable) {
2582 if (end_zone && end_zone == i)
2583 end_zone--;
2584 continue;
2585 }
2586
2587 if (!zone_watermark_ok_safe(zone, order,
2588 high_wmark_pages(zone), end_zone, 0)) {
2589 all_zones_ok = 0;
2590 /*
2591 * We are still under min water mark. This
2592 * means that we have a GFP_ATOMIC allocation
2593 * failure risk. Hurry up!
2594 */
2595 if (!zone_watermark_ok_safe(zone, order,
2596 min_wmark_pages(zone), end_zone, 0))
2597 has_under_min_watermark_zone = 1;
2598 } else {
2599 /*
2600 * If a zone reaches its high watermark,
2601 * consider it to be no longer congested. It's
2602 * possible there are dirty pages backed by
2603 * congested BDIs but as pressure is relieved,
2604 * spectulatively avoid congestion waits
2605 */
2606 zone_clear_flag(zone, ZONE_CONGESTED);
2607 if (i <= *classzone_idx)
2608 balanced += zone->present_pages;
2609 }
2610
2611 }
2612 if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))
2613 break; /* kswapd: all done */
2614 /*
2615 * OK, kswapd is getting into trouble. Take a nap, then take
2616 * another pass across the zones.
2617 */
2618 if (total_scanned && (priority < DEF_PRIORITY - 2)) {
2619 if (has_under_min_watermark_zone)
2620 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT);
2621 else
2622 congestion_wait(BLK_RW_ASYNC, HZ/10);
2623 }
2624
2625 /*
2626 * We do this so kswapd doesn't build up large priorities for
2627 * example when it is freeing in parallel with allocators. It
2628 * matches the direct reclaim path behaviour in terms of impact
2629 * on zone->*_priority.
2630 */
2631 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
2632 break;
2633 }
2634out:
2635
2636 /*
2637 * order-0: All zones must meet high watermark for a balanced node
2638 * high-order: Balanced zones must make up at least 25% of the node
2639 * for the node to be balanced
2640 */
2641 if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) {
2642 cond_resched();
2643
2644 try_to_freeze();
2645
2646 /*
2647 * Fragmentation may mean that the system cannot be
2648 * rebalanced for high-order allocations in all zones.
2649 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
2650 * it means the zones have been fully scanned and are still
2651 * not balanced. For high-order allocations, there is
2652 * little point trying all over again as kswapd may
2653 * infinite loop.
2654 *
2655 * Instead, recheck all watermarks at order-0 as they
2656 * are the most important. If watermarks are ok, kswapd will go
2657 * back to sleep. High-order users can still perform direct
2658 * reclaim if they wish.
2659 */
2660 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX)
2661 order = sc.order = 0;
2662
2663 goto loop_again;
2664 }
2665
2666 /*
2667 * If kswapd was reclaiming at a higher order, it has the option of
2668 * sleeping without all zones being balanced. Before it does, it must
2669 * ensure that the watermarks for order-0 on *all* zones are met and
2670 * that the congestion flags are cleared. The congestion flag must
2671 * be cleared as kswapd is the only mechanism that clears the flag
2672 * and it is potentially going to sleep here.
2673 */
2674 if (order) {
2675 for (i = 0; i <= end_zone; i++) {
2676 struct zone *zone = pgdat->node_zones + i;
2677
2678 if (!populated_zone(zone))
2679 continue;
2680
2681 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2682 continue;
2683
2684 /* Confirm the zone is balanced for order-0 */
2685 if (!zone_watermark_ok(zone, 0,
2686 high_wmark_pages(zone), 0, 0)) {
2687 order = sc.order = 0;
2688 goto loop_again;
2689 }
2690
2691 /* If balanced, clear the congested flag */
2692 zone_clear_flag(zone, ZONE_CONGESTED);
2693 }
2694 }
2695
2696 /*
2697 * Return the order we were reclaiming at so sleeping_prematurely()
2698 * makes a decision on the order we were last reclaiming at. However,
2699 * if another caller entered the allocator slow path while kswapd
2700 * was awake, order will remain at the higher level
2701 */
2702 *classzone_idx = end_zone;
2703 return order;
2704}
2705
2706static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx)
2707{
2708 long remaining = 0;
2709 DEFINE_WAIT(wait);
2710
2711 if (freezing(current) || kthread_should_stop())
2712 return;
2713
2714 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2715
2716 /* Try to sleep for a short interval */
2717 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2718 remaining = schedule_timeout(HZ/10);
2719 finish_wait(&pgdat->kswapd_wait, &wait);
2720 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2721 }
2722
2723 /*
2724 * After a short sleep, check if it was a premature sleep. If not, then
2725 * go fully to sleep until explicitly woken up.
2726 */
2727 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2728 trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
2729
2730 /*
2731 * vmstat counters are not perfectly accurate and the estimated
2732 * value for counters such as NR_FREE_PAGES can deviate from the
2733 * true value by nr_online_cpus * threshold. To avoid the zone
2734 * watermarks being breached while under pressure, we reduce the
2735 * per-cpu vmstat threshold while kswapd is awake and restore
2736 * them before going back to sleep.
2737 */
2738 set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold);
2739 schedule();
2740 set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold);
2741 } else {
2742 if (remaining)
2743 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
2744 else
2745 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
2746 }
2747 finish_wait(&pgdat->kswapd_wait, &wait);
2748}
2749
2750/*
2751 * The background pageout daemon, started as a kernel thread
2752 * from the init process.
2753 *
2754 * This basically trickles out pages so that we have _some_
2755 * free memory available even if there is no other activity
2756 * that frees anything up. This is needed for things like routing
2757 * etc, where we otherwise might have all activity going on in
2758 * asynchronous contexts that cannot page things out.
2759 *
2760 * If there are applications that are active memory-allocators
2761 * (most normal use), this basically shouldn't matter.
2762 */
2763static int kswapd(void *p)
2764{
2765 unsigned long order, new_order;
2766 int classzone_idx, new_classzone_idx;
2767 pg_data_t *pgdat = (pg_data_t*)p;
2768 struct task_struct *tsk = current;
2769
2770 struct reclaim_state reclaim_state = {
2771 .reclaimed_slab = 0,
2772 };
2773 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
2774
2775 lockdep_set_current_reclaim_state(GFP_KERNEL);
2776
2777 if (!cpumask_empty(cpumask))
2778 set_cpus_allowed_ptr(tsk, cpumask);
2779 current->reclaim_state = &reclaim_state;
2780
2781 /*
2782 * Tell the memory management that we're a "memory allocator",
2783 * and that if we need more memory we should get access to it
2784 * regardless (see "__alloc_pages()"). "kswapd" should
2785 * never get caught in the normal page freeing logic.
2786 *
2787 * (Kswapd normally doesn't need memory anyway, but sometimes
2788 * you need a small amount of memory in order to be able to
2789 * page out something else, and this flag essentially protects
2790 * us from recursively trying to free more memory as we're
2791 * trying to free the first piece of memory in the first place).
2792 */
2793 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
2794 set_freezable();
2795
2796 order = new_order = 0;
2797 classzone_idx = new_classzone_idx = pgdat->nr_zones - 1;
2798 for ( ; ; ) {
2799 int ret;
2800
2801 /*
2802 * If the last balance_pgdat was unsuccessful it's unlikely a
2803 * new request of a similar or harder type will succeed soon
2804 * so consider going to sleep on the basis we reclaimed at
2805 */
2806 if (classzone_idx >= new_classzone_idx && order == new_order) {
2807 new_order = pgdat->kswapd_max_order;
2808 new_classzone_idx = pgdat->classzone_idx;
2809 pgdat->kswapd_max_order = 0;
2810 pgdat->classzone_idx = pgdat->nr_zones - 1;
2811 }
2812
2813 if (order < new_order || classzone_idx > new_classzone_idx) {
2814 /*
2815 * Don't sleep if someone wants a larger 'order'
2816 * allocation or has tigher zone constraints
2817 */
2818 order = new_order;
2819 classzone_idx = new_classzone_idx;
2820 } else {
2821 kswapd_try_to_sleep(pgdat, order, classzone_idx);
2822 order = pgdat->kswapd_max_order;
2823 classzone_idx = pgdat->classzone_idx;
2824 pgdat->kswapd_max_order = 0;
2825 pgdat->classzone_idx = pgdat->nr_zones - 1;
2826 }
2827
2828 ret = try_to_freeze();
2829 if (kthread_should_stop())
2830 break;
2831
2832 /*
2833 * We can speed up thawing tasks if we don't call balance_pgdat
2834 * after returning from the refrigerator
2835 */
2836 if (!ret) {
2837 trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
2838 order = balance_pgdat(pgdat, order, &classzone_idx);
2839 }
2840 }
2841 return 0;
2842}
2843
2844/*
2845 * A zone is low on free memory, so wake its kswapd task to service it.
2846 */
2847void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
2848{
2849 pg_data_t *pgdat;
2850
2851 if (!populated_zone(zone))
2852 return;
2853
2854 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2855 return;
2856 pgdat = zone->zone_pgdat;
2857 if (pgdat->kswapd_max_order < order) {
2858 pgdat->kswapd_max_order = order;
2859 pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx);
2860 }
2861 if (!waitqueue_active(&pgdat->kswapd_wait))
2862 return;
2863 if (zone_watermark_ok_safe(zone, order, low_wmark_pages(zone), 0, 0))
2864 return;
2865
2866 trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);
2867 wake_up_interruptible(&pgdat->kswapd_wait);
2868}
2869
2870/*
2871 * The reclaimable count would be mostly accurate.
2872 * The less reclaimable pages may be
2873 * - mlocked pages, which will be moved to unevictable list when encountered
2874 * - mapped pages, which may require several travels to be reclaimed
2875 * - dirty pages, which is not "instantly" reclaimable
2876 */
2877unsigned long global_reclaimable_pages(void)
2878{
2879 int nr;
2880
2881 nr = global_page_state(NR_ACTIVE_FILE) +
2882 global_page_state(NR_INACTIVE_FILE);
2883
2884 if (nr_swap_pages > 0)
2885 nr += global_page_state(NR_ACTIVE_ANON) +
2886 global_page_state(NR_INACTIVE_ANON);
2887
2888 return nr;
2889}
2890
2891unsigned long zone_reclaimable_pages(struct zone *zone)
2892{
2893 int nr;
2894
2895 nr = zone_page_state(zone, NR_ACTIVE_FILE) +
2896 zone_page_state(zone, NR_INACTIVE_FILE);
2897
2898 if (nr_swap_pages > 0)
2899 nr += zone_page_state(zone, NR_ACTIVE_ANON) +
2900 zone_page_state(zone, NR_INACTIVE_ANON);
2901
2902 return nr;
2903}
2904
2905#ifdef CONFIG_HIBERNATION
2906/*
2907 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
2908 * freed pages.
2909 *
2910 * Rather than trying to age LRUs the aim is to preserve the overall
2911 * LRU order by reclaiming preferentially
2912 * inactive > active > active referenced > active mapped
2913 */
2914unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
2915{
2916 struct reclaim_state reclaim_state;
2917 struct scan_control sc = {
2918 .gfp_mask = GFP_HIGHUSER_MOVABLE,
2919 .may_swap = 1,
2920 .may_unmap = 1,
2921 .may_writepage = 1,
2922 .nr_to_reclaim = nr_to_reclaim,
2923 .hibernation_mode = 1,
2924 .order = 0,
2925 };
2926 struct shrink_control shrink = {
2927 .gfp_mask = sc.gfp_mask,
2928 };
2929 struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
2930 struct task_struct *p = current;
2931 unsigned long nr_reclaimed;
2932
2933 p->flags |= PF_MEMALLOC;
2934 lockdep_set_current_reclaim_state(sc.gfp_mask);
2935 reclaim_state.reclaimed_slab = 0;
2936 p->reclaim_state = &reclaim_state;
2937
2938 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2939
2940 p->reclaim_state = NULL;
2941 lockdep_clear_current_reclaim_state();
2942 p->flags &= ~PF_MEMALLOC;
2943
2944 return nr_reclaimed;
2945}
2946#endif /* CONFIG_HIBERNATION */
2947
2948/* It's optimal to keep kswapds on the same CPUs as their memory, but
2949 not required for correctness. So if the last cpu in a node goes
2950 away, we get changed to run anywhere: as the first one comes back,
2951 restore their cpu bindings. */
2952static int __devinit cpu_callback(struct notifier_block *nfb,
2953 unsigned long action, void *hcpu)
2954{
2955 int nid;
2956
2957 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2958 for_each_node_state(nid, N_HIGH_MEMORY) {
2959 pg_data_t *pgdat = NODE_DATA(nid);
2960 const struct cpumask *mask;
2961
2962 mask = cpumask_of_node(pgdat->node_id);
2963
2964 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
2965 /* One of our CPUs online: restore mask */
2966 set_cpus_allowed_ptr(pgdat->kswapd, mask);
2967 }
2968 }
2969 return NOTIFY_OK;
2970}
2971
2972/*
2973 * This kswapd start function will be called by init and node-hot-add.
2974 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2975 */
2976int kswapd_run(int nid)
2977{
2978 pg_data_t *pgdat = NODE_DATA(nid);
2979 int ret = 0;
2980
2981 if (pgdat->kswapd)
2982 return 0;
2983
2984 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
2985 if (IS_ERR(pgdat->kswapd)) {
2986 /* failure at boot is fatal */
2987 BUG_ON(system_state == SYSTEM_BOOTING);
2988 printk("Failed to start kswapd on node %d\n",nid);
2989 ret = -1;
2990 }
2991 return ret;
2992}
2993
2994/*
2995 * Called by memory hotplug when all memory in a node is offlined.
2996 */
2997void kswapd_stop(int nid)
2998{
2999 struct task_struct *kswapd = NODE_DATA(nid)->kswapd;
3000
3001 if (kswapd)
3002 kthread_stop(kswapd);
3003}
3004
3005static int __init kswapd_init(void)
3006{
3007 int nid;
3008
3009 swap_setup();
3010 for_each_node_state(nid, N_HIGH_MEMORY)
3011 kswapd_run(nid);
3012 hotcpu_notifier(cpu_callback, 0);
3013 return 0;
3014}
3015
3016module_init(kswapd_init)
3017
3018#ifdef CONFIG_NUMA
3019/*
3020 * Zone reclaim mode
3021 *
3022 * If non-zero call zone_reclaim when the number of free pages falls below
3023 * the watermarks.
3024 */
3025int zone_reclaim_mode __read_mostly;
3026
3027#define RECLAIM_OFF 0
3028#define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
3029#define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
3030#define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
3031
3032/*
3033 * Priority for ZONE_RECLAIM. This determines the fraction of pages
3034 * of a node considered for each zone_reclaim. 4 scans 1/16th of
3035 * a zone.
3036 */
3037#define ZONE_RECLAIM_PRIORITY 4
3038
3039/*
3040 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
3041 * occur.
3042 */
3043int sysctl_min_unmapped_ratio = 1;
3044
3045/*
3046 * If the number of slab pages in a zone grows beyond this percentage then
3047 * slab reclaim needs to occur.
3048 */
3049int sysctl_min_slab_ratio = 5;
3050
3051static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
3052{
3053 unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
3054 unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
3055 zone_page_state(zone, NR_ACTIVE_FILE);
3056
3057 /*
3058 * It's possible for there to be more file mapped pages than
3059 * accounted for by the pages on the file LRU lists because
3060 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
3061 */
3062 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
3063}
3064
3065/* Work out how many page cache pages we can reclaim in this reclaim_mode */
3066static long zone_pagecache_reclaimable(struct zone *zone)
3067{
3068 long nr_pagecache_reclaimable;
3069 long delta = 0;
3070
3071 /*
3072 * If RECLAIM_SWAP is set, then all file pages are considered
3073 * potentially reclaimable. Otherwise, we have to worry about
3074 * pages like swapcache and zone_unmapped_file_pages() provides
3075 * a better estimate
3076 */
3077 if (zone_reclaim_mode & RECLAIM_SWAP)
3078 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
3079 else
3080 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
3081
3082 /* If we can't clean pages, remove dirty pages from consideration */
3083 if (!(zone_reclaim_mode & RECLAIM_WRITE))
3084 delta += zone_page_state(zone, NR_FILE_DIRTY);
3085
3086 /* Watch for any possible underflows due to delta */
3087 if (unlikely(delta > nr_pagecache_reclaimable))
3088 delta = nr_pagecache_reclaimable;
3089
3090 return nr_pagecache_reclaimable - delta;
3091}
3092
3093/*
3094 * Try to free up some pages from this zone through reclaim.
3095 */
3096static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
3097{
3098 /* Minimum pages needed in order to stay on node */
3099 const unsigned long nr_pages = 1 << order;
3100 struct task_struct *p = current;
3101 struct reclaim_state reclaim_state;
3102 int priority;
3103 struct scan_control sc = {
3104 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
3105 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
3106 .may_swap = 1,
3107 .nr_to_reclaim = max_t(unsigned long, nr_pages,
3108 SWAP_CLUSTER_MAX),
3109 .gfp_mask = gfp_mask,
3110 .order = order,
3111 };
3112 struct shrink_control shrink = {
3113 .gfp_mask = sc.gfp_mask,
3114 };
3115 unsigned long nr_slab_pages0, nr_slab_pages1;
3116
3117 cond_resched();
3118 /*
3119 * We need to be able to allocate from the reserves for RECLAIM_SWAP
3120 * and we also need to be able to write out pages for RECLAIM_WRITE
3121 * and RECLAIM_SWAP.
3122 */
3123 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
3124 lockdep_set_current_reclaim_state(gfp_mask);
3125 reclaim_state.reclaimed_slab = 0;
3126 p->reclaim_state = &reclaim_state;
3127
3128 if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
3129 /*
3130 * Free memory by calling shrink zone with increasing
3131 * priorities until we have enough memory freed.
3132 */
3133 priority = ZONE_RECLAIM_PRIORITY;
3134 do {
3135 shrink_zone(priority, zone, &sc);
3136 priority--;
3137 } while (priority >= 0 && sc.nr_reclaimed < nr_pages);
3138 }
3139
3140 nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
3141 if (nr_slab_pages0 > zone->min_slab_pages) {
3142 /*
3143 * shrink_slab() does not currently allow us to determine how
3144 * many pages were freed in this zone. So we take the current
3145 * number of slab pages and shake the slab until it is reduced
3146 * by the same nr_pages that we used for reclaiming unmapped
3147 * pages.
3148 *
3149 * Note that shrink_slab will free memory on all zones and may
3150 * take a long time.
3151 */
3152 for (;;) {
3153 unsigned long lru_pages = zone_reclaimable_pages(zone);
3154
3155 /* No reclaimable slab or very low memory pressure */
3156 if (!shrink_slab(&shrink, sc.nr_scanned, lru_pages))
3157 break;
3158
3159 /* Freed enough memory */
3160 nr_slab_pages1 = zone_page_state(zone,
3161 NR_SLAB_RECLAIMABLE);
3162 if (nr_slab_pages1 + nr_pages <= nr_slab_pages0)
3163 break;
3164 }
3165
3166 /*
3167 * Update nr_reclaimed by the number of slab pages we
3168 * reclaimed from this zone.
3169 */
3170 nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
3171 if (nr_slab_pages1 < nr_slab_pages0)
3172 sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1;
3173 }
3174
3175 p->reclaim_state = NULL;
3176 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
3177 lockdep_clear_current_reclaim_state();
3178 return sc.nr_reclaimed >= nr_pages;
3179}
3180
3181int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
3182{
3183 int node_id;
3184 int ret;
3185
3186 /*
3187 * Zone reclaim reclaims unmapped file backed pages and
3188 * slab pages if we are over the defined limits.
3189 *
3190 * A small portion of unmapped file backed pages is needed for
3191 * file I/O otherwise pages read by file I/O will be immediately
3192 * thrown out if the zone is overallocated. So we do not reclaim
3193 * if less than a specified percentage of the zone is used by
3194 * unmapped file backed pages.
3195 */
3196 if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
3197 zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
3198 return ZONE_RECLAIM_FULL;
3199
3200 if (zone->all_unreclaimable)
3201 return ZONE_RECLAIM_FULL;
3202
3203 /*
3204 * Do not scan if the allocation should not be delayed.
3205 */
3206 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
3207 return ZONE_RECLAIM_NOSCAN;
3208
3209 /*
3210 * Only run zone reclaim on the local zone or on zones that do not
3211 * have associated processors. This will favor the local processor
3212 * over remote processors and spread off node memory allocations
3213 * as wide as possible.
3214 */
3215 node_id = zone_to_nid(zone);
3216 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
3217 return ZONE_RECLAIM_NOSCAN;
3218
3219 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
3220 return ZONE_RECLAIM_NOSCAN;
3221
3222 ret = __zone_reclaim(zone, gfp_mask, order);
3223 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
3224
3225 if (!ret)
3226 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
3227
3228 return ret;
3229}
3230#endif
3231
3232/*
3233 * page_evictable - test whether a page is evictable
3234 * @page: the page to test
3235 * @vma: the VMA in which the page is or will be mapped, may be NULL
3236 *
3237 * Test whether page is evictable--i.e., should be placed on active/inactive
3238 * lists vs unevictable list. The vma argument is !NULL when called from the
3239 * fault path to determine how to instantate a new page.
3240 *
3241 * Reasons page might not be evictable:
3242 * (1) page's mapping marked unevictable
3243 * (2) page is part of an mlocked VMA
3244 *
3245 */
3246int page_evictable(struct page *page, struct vm_area_struct *vma)
3247{
3248
3249 if (mapping_unevictable(page_mapping(page)))
3250 return 0;
3251
3252 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
3253 return 0;
3254
3255 return 1;
3256}
3257
3258/**
3259 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
3260 * @page: page to check evictability and move to appropriate lru list
3261 * @zone: zone page is in
3262 *
3263 * Checks a page for evictability and moves the page to the appropriate
3264 * zone lru list.
3265 *
3266 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
3267 * have PageUnevictable set.
3268 */
3269static void check_move_unevictable_page(struct page *page, struct zone *zone)
3270{
3271 VM_BUG_ON(PageActive(page));
3272
3273retry:
3274 ClearPageUnevictable(page);
3275 if (page_evictable(page, NULL)) {
3276 enum lru_list l = page_lru_base_type(page);
3277
3278 __dec_zone_state(zone, NR_UNEVICTABLE);
3279 list_move(&page->lru, &zone->lru[l].list);
3280 mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l);
3281 __inc_zone_state(zone, NR_INACTIVE_ANON + l);
3282 __count_vm_event(UNEVICTABLE_PGRESCUED);
3283 } else {
3284 /*
3285 * rotate unevictable list
3286 */
3287 SetPageUnevictable(page);
3288 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
3289 mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE);
3290 if (page_evictable(page, NULL))
3291 goto retry;
3292 }
3293}
3294
3295/**
3296 * scan_mapping_unevictable_pages - scan an address space for evictable pages
3297 * @mapping: struct address_space to scan for evictable pages
3298 *
3299 * Scan all pages in mapping. Check unevictable pages for
3300 * evictability and move them to the appropriate zone lru list.
3301 */
3302void scan_mapping_unevictable_pages(struct address_space *mapping)
3303{
3304 pgoff_t next = 0;
3305 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >>
3306 PAGE_CACHE_SHIFT;
3307 struct zone *zone;
3308 struct pagevec pvec;
3309
3310 if (mapping->nrpages == 0)
3311 return;
3312
3313 pagevec_init(&pvec, 0);
3314 while (next < end &&
3315 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
3316 int i;
3317 int pg_scanned = 0;
3318
3319 zone = NULL;
3320
3321 for (i = 0; i < pagevec_count(&pvec); i++) {
3322 struct page *page = pvec.pages[i];
3323 pgoff_t page_index = page->index;
3324 struct zone *pagezone = page_zone(page);
3325
3326 pg_scanned++;
3327 if (page_index > next)
3328 next = page_index;
3329 next++;
3330
3331 if (pagezone != zone) {
3332 if (zone)
3333 spin_unlock_irq(&zone->lru_lock);
3334 zone = pagezone;
3335 spin_lock_irq(&zone->lru_lock);
3336 }
3337
3338 if (PageLRU(page) && PageUnevictable(page))
3339 check_move_unevictable_page(page, zone);
3340 }
3341 if (zone)
3342 spin_unlock_irq(&zone->lru_lock);
3343 pagevec_release(&pvec);
3344
3345 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
3346 }
3347
3348}
3349
3350/**
3351 * scan_zone_unevictable_pages - check unevictable list for evictable pages
3352 * @zone - zone of which to scan the unevictable list
3353 *
3354 * Scan @zone's unevictable LRU lists to check for pages that have become
3355 * evictable. Move those that have to @zone's inactive list where they
3356 * become candidates for reclaim, unless shrink_inactive_zone() decides
3357 * to reactivate them. Pages that are still unevictable are rotated
3358 * back onto @zone's unevictable list.
3359 */
3360#define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
3361static void scan_zone_unevictable_pages(struct zone *zone)
3362{
3363 struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list;
3364 unsigned long scan;
3365 unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE);
3366
3367 while (nr_to_scan > 0) {
3368 unsigned long batch_size = min(nr_to_scan,
3369 SCAN_UNEVICTABLE_BATCH_SIZE);
3370
3371 spin_lock_irq(&zone->lru_lock);
3372 for (scan = 0; scan < batch_size; scan++) {
3373 struct page *page = lru_to_page(l_unevictable);
3374
3375 if (!trylock_page(page))
3376 continue;
3377
3378 prefetchw_prev_lru_page(page, l_unevictable, flags);
3379
3380 if (likely(PageLRU(page) && PageUnevictable(page)))
3381 check_move_unevictable_page(page, zone);
3382
3383 unlock_page(page);
3384 }
3385 spin_unlock_irq(&zone->lru_lock);
3386
3387 nr_to_scan -= batch_size;
3388 }
3389}
3390
3391
3392/**
3393 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
3394 *
3395 * A really big hammer: scan all zones' unevictable LRU lists to check for
3396 * pages that have become evictable. Move those back to the zones'
3397 * inactive list where they become candidates for reclaim.
3398 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
3399 * and we add swap to the system. As such, it runs in the context of a task
3400 * that has possibly/probably made some previously unevictable pages
3401 * evictable.
3402 */
3403static void scan_all_zones_unevictable_pages(void)
3404{
3405 struct zone *zone;
3406
3407 for_each_zone(zone) {
3408 scan_zone_unevictable_pages(zone);
3409 }
3410}
3411
3412/*
3413 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
3414 * all nodes' unevictable lists for evictable pages
3415 */
3416unsigned long scan_unevictable_pages;
3417
3418int scan_unevictable_handler(struct ctl_table *table, int write,
3419 void __user *buffer,
3420 size_t *length, loff_t *ppos)
3421{
3422 proc_doulongvec_minmax(table, write, buffer, length, ppos);
3423
3424 if (write && *(unsigned long *)table->data)
3425 scan_all_zones_unevictable_pages();
3426
3427 scan_unevictable_pages = 0;
3428 return 0;
3429}
3430
3431#ifdef CONFIG_NUMA
3432/*
3433 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
3434 * a specified node's per zone unevictable lists for evictable pages.
3435 */
3436
3437static ssize_t read_scan_unevictable_node(struct sys_device *dev,
3438 struct sysdev_attribute *attr,
3439 char *buf)
3440{
3441 return sprintf(buf, "0\n"); /* always zero; should fit... */
3442}
3443
3444static ssize_t write_scan_unevictable_node(struct sys_device *dev,
3445 struct sysdev_attribute *attr,
3446 const char *buf, size_t count)
3447{
3448 struct zone *node_zones = NODE_DATA(dev->id)->node_zones;
3449 struct zone *zone;
3450 unsigned long res;
3451 unsigned long req = strict_strtoul(buf, 10, &res);
3452
3453 if (!req)
3454 return 1; /* zero is no-op */
3455
3456 for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
3457 if (!populated_zone(zone))
3458 continue;
3459 scan_zone_unevictable_pages(zone);
3460 }
3461 return 1;
3462}
3463
3464
3465static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
3466 read_scan_unevictable_node,
3467 write_scan_unevictable_node);
3468
3469int scan_unevictable_register_node(struct node *node)
3470{
3471 return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages);
3472}
3473
3474void scan_unevictable_unregister_node(struct node *node)
3475{
3476 sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages);
3477}
3478#endif
1/*
2 * linux/mm/vmscan.c
3 *
4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
5 *
6 * Swap reorganised 29.12.95, Stephen Tweedie.
7 * kswapd added: 7.1.96 sct
8 * Removed kswapd_ctl limits, and swap out as many pages as needed
9 * to bring the system back to freepages.high: 2.4.97, Rik van Riel.
10 * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
11 * Multiqueue VM started 5.8.00, Rik van Riel.
12 */
13
14#include <linux/mm.h>
15#include <linux/module.h>
16#include <linux/gfp.h>
17#include <linux/kernel_stat.h>
18#include <linux/swap.h>
19#include <linux/pagemap.h>
20#include <linux/init.h>
21#include <linux/highmem.h>
22#include <linux/vmpressure.h>
23#include <linux/vmstat.h>
24#include <linux/file.h>
25#include <linux/writeback.h>
26#include <linux/blkdev.h>
27#include <linux/buffer_head.h> /* for try_to_release_page(),
28 buffer_heads_over_limit */
29#include <linux/mm_inline.h>
30#include <linux/backing-dev.h>
31#include <linux/rmap.h>
32#include <linux/topology.h>
33#include <linux/cpu.h>
34#include <linux/cpuset.h>
35#include <linux/compaction.h>
36#include <linux/notifier.h>
37#include <linux/rwsem.h>
38#include <linux/delay.h>
39#include <linux/kthread.h>
40#include <linux/freezer.h>
41#include <linux/memcontrol.h>
42#include <linux/delayacct.h>
43#include <linux/sysctl.h>
44#include <linux/oom.h>
45#include <linux/prefetch.h>
46
47#include <asm/tlbflush.h>
48#include <asm/div64.h>
49
50#include <linux/swapops.h>
51#include <linux/balloon_compaction.h>
52
53#include "internal.h"
54
55#define CREATE_TRACE_POINTS
56#include <trace/events/vmscan.h>
57
58struct scan_control {
59 /* Incremented by the number of inactive pages that were scanned */
60 unsigned long nr_scanned;
61
62 /* Number of pages freed so far during a call to shrink_zones() */
63 unsigned long nr_reclaimed;
64
65 /* How many pages shrink_list() should reclaim */
66 unsigned long nr_to_reclaim;
67
68 unsigned long hibernation_mode;
69
70 /* This context's GFP mask */
71 gfp_t gfp_mask;
72
73 int may_writepage;
74
75 /* Can mapped pages be reclaimed? */
76 int may_unmap;
77
78 /* Can pages be swapped as part of reclaim? */
79 int may_swap;
80
81 int order;
82
83 /* Scan (total_size >> priority) pages at once */
84 int priority;
85
86 /*
87 * The memory cgroup that hit its limit and as a result is the
88 * primary target of this reclaim invocation.
89 */
90 struct mem_cgroup *target_mem_cgroup;
91
92 /*
93 * Nodemask of nodes allowed by the caller. If NULL, all nodes
94 * are scanned.
95 */
96 nodemask_t *nodemask;
97};
98
99#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
100
101#ifdef ARCH_HAS_PREFETCH
102#define prefetch_prev_lru_page(_page, _base, _field) \
103 do { \
104 if ((_page)->lru.prev != _base) { \
105 struct page *prev; \
106 \
107 prev = lru_to_page(&(_page->lru)); \
108 prefetch(&prev->_field); \
109 } \
110 } while (0)
111#else
112#define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
113#endif
114
115#ifdef ARCH_HAS_PREFETCHW
116#define prefetchw_prev_lru_page(_page, _base, _field) \
117 do { \
118 if ((_page)->lru.prev != _base) { \
119 struct page *prev; \
120 \
121 prev = lru_to_page(&(_page->lru)); \
122 prefetchw(&prev->_field); \
123 } \
124 } while (0)
125#else
126#define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
127#endif
128
129/*
130 * From 0 .. 100. Higher means more swappy.
131 */
132int vm_swappiness = 60;
133unsigned long vm_total_pages; /* The total number of pages which the VM controls */
134
135static LIST_HEAD(shrinker_list);
136static DECLARE_RWSEM(shrinker_rwsem);
137
138#ifdef CONFIG_MEMCG
139static bool global_reclaim(struct scan_control *sc)
140{
141 return !sc->target_mem_cgroup;
142}
143#else
144static bool global_reclaim(struct scan_control *sc)
145{
146 return true;
147}
148#endif
149
150static unsigned long zone_reclaimable_pages(struct zone *zone)
151{
152 int nr;
153
154 nr = zone_page_state(zone, NR_ACTIVE_FILE) +
155 zone_page_state(zone, NR_INACTIVE_FILE);
156
157 if (get_nr_swap_pages() > 0)
158 nr += zone_page_state(zone, NR_ACTIVE_ANON) +
159 zone_page_state(zone, NR_INACTIVE_ANON);
160
161 return nr;
162}
163
164bool zone_reclaimable(struct zone *zone)
165{
166 return zone->pages_scanned < zone_reclaimable_pages(zone) * 6;
167}
168
169static unsigned long get_lru_size(struct lruvec *lruvec, enum lru_list lru)
170{
171 if (!mem_cgroup_disabled())
172 return mem_cgroup_get_lru_size(lruvec, lru);
173
174 return zone_page_state(lruvec_zone(lruvec), NR_LRU_BASE + lru);
175}
176
177/*
178 * Add a shrinker callback to be called from the vm.
179 */
180int register_shrinker(struct shrinker *shrinker)
181{
182 size_t size = sizeof(*shrinker->nr_deferred);
183
184 /*
185 * If we only have one possible node in the system anyway, save
186 * ourselves the trouble and disable NUMA aware behavior. This way we
187 * will save memory and some small loop time later.
188 */
189 if (nr_node_ids == 1)
190 shrinker->flags &= ~SHRINKER_NUMA_AWARE;
191
192 if (shrinker->flags & SHRINKER_NUMA_AWARE)
193 size *= nr_node_ids;
194
195 shrinker->nr_deferred = kzalloc(size, GFP_KERNEL);
196 if (!shrinker->nr_deferred)
197 return -ENOMEM;
198
199 down_write(&shrinker_rwsem);
200 list_add_tail(&shrinker->list, &shrinker_list);
201 up_write(&shrinker_rwsem);
202 return 0;
203}
204EXPORT_SYMBOL(register_shrinker);
205
206/*
207 * Remove one
208 */
209void unregister_shrinker(struct shrinker *shrinker)
210{
211 down_write(&shrinker_rwsem);
212 list_del(&shrinker->list);
213 up_write(&shrinker_rwsem);
214 kfree(shrinker->nr_deferred);
215}
216EXPORT_SYMBOL(unregister_shrinker);
217
218#define SHRINK_BATCH 128
219
220static unsigned long
221shrink_slab_node(struct shrink_control *shrinkctl, struct shrinker *shrinker,
222 unsigned long nr_pages_scanned, unsigned long lru_pages)
223{
224 unsigned long freed = 0;
225 unsigned long long delta;
226 long total_scan;
227 long freeable;
228 long nr;
229 long new_nr;
230 int nid = shrinkctl->nid;
231 long batch_size = shrinker->batch ? shrinker->batch
232 : SHRINK_BATCH;
233
234 freeable = shrinker->count_objects(shrinker, shrinkctl);
235 if (freeable == 0)
236 return 0;
237
238 /*
239 * copy the current shrinker scan count into a local variable
240 * and zero it so that other concurrent shrinker invocations
241 * don't also do this scanning work.
242 */
243 nr = atomic_long_xchg(&shrinker->nr_deferred[nid], 0);
244
245 total_scan = nr;
246 delta = (4 * nr_pages_scanned) / shrinker->seeks;
247 delta *= freeable;
248 do_div(delta, lru_pages + 1);
249 total_scan += delta;
250 if (total_scan < 0) {
251 printk(KERN_ERR
252 "shrink_slab: %pF negative objects to delete nr=%ld\n",
253 shrinker->scan_objects, total_scan);
254 total_scan = freeable;
255 }
256
257 /*
258 * We need to avoid excessive windup on filesystem shrinkers
259 * due to large numbers of GFP_NOFS allocations causing the
260 * shrinkers to return -1 all the time. This results in a large
261 * nr being built up so when a shrink that can do some work
262 * comes along it empties the entire cache due to nr >>>
263 * freeable. This is bad for sustaining a working set in
264 * memory.
265 *
266 * Hence only allow the shrinker to scan the entire cache when
267 * a large delta change is calculated directly.
268 */
269 if (delta < freeable / 4)
270 total_scan = min(total_scan, freeable / 2);
271
272 /*
273 * Avoid risking looping forever due to too large nr value:
274 * never try to free more than twice the estimate number of
275 * freeable entries.
276 */
277 if (total_scan > freeable * 2)
278 total_scan = freeable * 2;
279
280 trace_mm_shrink_slab_start(shrinker, shrinkctl, nr,
281 nr_pages_scanned, lru_pages,
282 freeable, delta, total_scan);
283
284 /*
285 * Normally, we should not scan less than batch_size objects in one
286 * pass to avoid too frequent shrinker calls, but if the slab has less
287 * than batch_size objects in total and we are really tight on memory,
288 * we will try to reclaim all available objects, otherwise we can end
289 * up failing allocations although there are plenty of reclaimable
290 * objects spread over several slabs with usage less than the
291 * batch_size.
292 *
293 * We detect the "tight on memory" situations by looking at the total
294 * number of objects we want to scan (total_scan). If it is greater
295 * than the total number of objects on slab (freeable), we must be
296 * scanning at high prio and therefore should try to reclaim as much as
297 * possible.
298 */
299 while (total_scan >= batch_size ||
300 total_scan >= freeable) {
301 unsigned long ret;
302 unsigned long nr_to_scan = min(batch_size, total_scan);
303
304 shrinkctl->nr_to_scan = nr_to_scan;
305 ret = shrinker->scan_objects(shrinker, shrinkctl);
306 if (ret == SHRINK_STOP)
307 break;
308 freed += ret;
309
310 count_vm_events(SLABS_SCANNED, nr_to_scan);
311 total_scan -= nr_to_scan;
312
313 cond_resched();
314 }
315
316 /*
317 * move the unused scan count back into the shrinker in a
318 * manner that handles concurrent updates. If we exhausted the
319 * scan, there is no need to do an update.
320 */
321 if (total_scan > 0)
322 new_nr = atomic_long_add_return(total_scan,
323 &shrinker->nr_deferred[nid]);
324 else
325 new_nr = atomic_long_read(&shrinker->nr_deferred[nid]);
326
327 trace_mm_shrink_slab_end(shrinker, freed, nr, new_nr);
328 return freed;
329}
330
331/*
332 * Call the shrink functions to age shrinkable caches
333 *
334 * Here we assume it costs one seek to replace a lru page and that it also
335 * takes a seek to recreate a cache object. With this in mind we age equal
336 * percentages of the lru and ageable caches. This should balance the seeks
337 * generated by these structures.
338 *
339 * If the vm encountered mapped pages on the LRU it increase the pressure on
340 * slab to avoid swapping.
341 *
342 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
343 *
344 * `lru_pages' represents the number of on-LRU pages in all the zones which
345 * are eligible for the caller's allocation attempt. It is used for balancing
346 * slab reclaim versus page reclaim.
347 *
348 * Returns the number of slab objects which we shrunk.
349 */
350unsigned long shrink_slab(struct shrink_control *shrinkctl,
351 unsigned long nr_pages_scanned,
352 unsigned long lru_pages)
353{
354 struct shrinker *shrinker;
355 unsigned long freed = 0;
356
357 if (nr_pages_scanned == 0)
358 nr_pages_scanned = SWAP_CLUSTER_MAX;
359
360 if (!down_read_trylock(&shrinker_rwsem)) {
361 /*
362 * If we would return 0, our callers would understand that we
363 * have nothing else to shrink and give up trying. By returning
364 * 1 we keep it going and assume we'll be able to shrink next
365 * time.
366 */
367 freed = 1;
368 goto out;
369 }
370
371 list_for_each_entry(shrinker, &shrinker_list, list) {
372 if (!(shrinker->flags & SHRINKER_NUMA_AWARE)) {
373 shrinkctl->nid = 0;
374 freed += shrink_slab_node(shrinkctl, shrinker,
375 nr_pages_scanned, lru_pages);
376 continue;
377 }
378
379 for_each_node_mask(shrinkctl->nid, shrinkctl->nodes_to_scan) {
380 if (node_online(shrinkctl->nid))
381 freed += shrink_slab_node(shrinkctl, shrinker,
382 nr_pages_scanned, lru_pages);
383
384 }
385 }
386 up_read(&shrinker_rwsem);
387out:
388 cond_resched();
389 return freed;
390}
391
392static inline int is_page_cache_freeable(struct page *page)
393{
394 /*
395 * A freeable page cache page is referenced only by the caller
396 * that isolated the page, the page cache radix tree and
397 * optional buffer heads at page->private.
398 */
399 return page_count(page) - page_has_private(page) == 2;
400}
401
402static int may_write_to_queue(struct backing_dev_info *bdi,
403 struct scan_control *sc)
404{
405 if (current->flags & PF_SWAPWRITE)
406 return 1;
407 if (!bdi_write_congested(bdi))
408 return 1;
409 if (bdi == current->backing_dev_info)
410 return 1;
411 return 0;
412}
413
414/*
415 * We detected a synchronous write error writing a page out. Probably
416 * -ENOSPC. We need to propagate that into the address_space for a subsequent
417 * fsync(), msync() or close().
418 *
419 * The tricky part is that after writepage we cannot touch the mapping: nothing
420 * prevents it from being freed up. But we have a ref on the page and once
421 * that page is locked, the mapping is pinned.
422 *
423 * We're allowed to run sleeping lock_page() here because we know the caller has
424 * __GFP_FS.
425 */
426static void handle_write_error(struct address_space *mapping,
427 struct page *page, int error)
428{
429 lock_page(page);
430 if (page_mapping(page) == mapping)
431 mapping_set_error(mapping, error);
432 unlock_page(page);
433}
434
435/* possible outcome of pageout() */
436typedef enum {
437 /* failed to write page out, page is locked */
438 PAGE_KEEP,
439 /* move page to the active list, page is locked */
440 PAGE_ACTIVATE,
441 /* page has been sent to the disk successfully, page is unlocked */
442 PAGE_SUCCESS,
443 /* page is clean and locked */
444 PAGE_CLEAN,
445} pageout_t;
446
447/*
448 * pageout is called by shrink_page_list() for each dirty page.
449 * Calls ->writepage().
450 */
451static pageout_t pageout(struct page *page, struct address_space *mapping,
452 struct scan_control *sc)
453{
454 /*
455 * If the page is dirty, only perform writeback if that write
456 * will be non-blocking. To prevent this allocation from being
457 * stalled by pagecache activity. But note that there may be
458 * stalls if we need to run get_block(). We could test
459 * PagePrivate for that.
460 *
461 * If this process is currently in __generic_file_aio_write() against
462 * this page's queue, we can perform writeback even if that
463 * will block.
464 *
465 * If the page is swapcache, write it back even if that would
466 * block, for some throttling. This happens by accident, because
467 * swap_backing_dev_info is bust: it doesn't reflect the
468 * congestion state of the swapdevs. Easy to fix, if needed.
469 */
470 if (!is_page_cache_freeable(page))
471 return PAGE_KEEP;
472 if (!mapping) {
473 /*
474 * Some data journaling orphaned pages can have
475 * page->mapping == NULL while being dirty with clean buffers.
476 */
477 if (page_has_private(page)) {
478 if (try_to_free_buffers(page)) {
479 ClearPageDirty(page);
480 printk("%s: orphaned page\n", __func__);
481 return PAGE_CLEAN;
482 }
483 }
484 return PAGE_KEEP;
485 }
486 if (mapping->a_ops->writepage == NULL)
487 return PAGE_ACTIVATE;
488 if (!may_write_to_queue(mapping->backing_dev_info, sc))
489 return PAGE_KEEP;
490
491 if (clear_page_dirty_for_io(page)) {
492 int res;
493 struct writeback_control wbc = {
494 .sync_mode = WB_SYNC_NONE,
495 .nr_to_write = SWAP_CLUSTER_MAX,
496 .range_start = 0,
497 .range_end = LLONG_MAX,
498 .for_reclaim = 1,
499 };
500
501 SetPageReclaim(page);
502 res = mapping->a_ops->writepage(page, &wbc);
503 if (res < 0)
504 handle_write_error(mapping, page, res);
505 if (res == AOP_WRITEPAGE_ACTIVATE) {
506 ClearPageReclaim(page);
507 return PAGE_ACTIVATE;
508 }
509
510 if (!PageWriteback(page)) {
511 /* synchronous write or broken a_ops? */
512 ClearPageReclaim(page);
513 }
514 trace_mm_vmscan_writepage(page, trace_reclaim_flags(page));
515 inc_zone_page_state(page, NR_VMSCAN_WRITE);
516 return PAGE_SUCCESS;
517 }
518
519 return PAGE_CLEAN;
520}
521
522/*
523 * Same as remove_mapping, but if the page is removed from the mapping, it
524 * gets returned with a refcount of 0.
525 */
526static int __remove_mapping(struct address_space *mapping, struct page *page,
527 bool reclaimed)
528{
529 BUG_ON(!PageLocked(page));
530 BUG_ON(mapping != page_mapping(page));
531
532 spin_lock_irq(&mapping->tree_lock);
533 /*
534 * The non racy check for a busy page.
535 *
536 * Must be careful with the order of the tests. When someone has
537 * a ref to the page, it may be possible that they dirty it then
538 * drop the reference. So if PageDirty is tested before page_count
539 * here, then the following race may occur:
540 *
541 * get_user_pages(&page);
542 * [user mapping goes away]
543 * write_to(page);
544 * !PageDirty(page) [good]
545 * SetPageDirty(page);
546 * put_page(page);
547 * !page_count(page) [good, discard it]
548 *
549 * [oops, our write_to data is lost]
550 *
551 * Reversing the order of the tests ensures such a situation cannot
552 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
553 * load is not satisfied before that of page->_count.
554 *
555 * Note that if SetPageDirty is always performed via set_page_dirty,
556 * and thus under tree_lock, then this ordering is not required.
557 */
558 if (!page_freeze_refs(page, 2))
559 goto cannot_free;
560 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
561 if (unlikely(PageDirty(page))) {
562 page_unfreeze_refs(page, 2);
563 goto cannot_free;
564 }
565
566 if (PageSwapCache(page)) {
567 swp_entry_t swap = { .val = page_private(page) };
568 __delete_from_swap_cache(page);
569 spin_unlock_irq(&mapping->tree_lock);
570 swapcache_free(swap, page);
571 } else {
572 void (*freepage)(struct page *);
573 void *shadow = NULL;
574
575 freepage = mapping->a_ops->freepage;
576 /*
577 * Remember a shadow entry for reclaimed file cache in
578 * order to detect refaults, thus thrashing, later on.
579 *
580 * But don't store shadows in an address space that is
581 * already exiting. This is not just an optizimation,
582 * inode reclaim needs to empty out the radix tree or
583 * the nodes are lost. Don't plant shadows behind its
584 * back.
585 */
586 if (reclaimed && page_is_file_cache(page) &&
587 !mapping_exiting(mapping))
588 shadow = workingset_eviction(mapping, page);
589 __delete_from_page_cache(page, shadow);
590 spin_unlock_irq(&mapping->tree_lock);
591 mem_cgroup_uncharge_cache_page(page);
592
593 if (freepage != NULL)
594 freepage(page);
595 }
596
597 return 1;
598
599cannot_free:
600 spin_unlock_irq(&mapping->tree_lock);
601 return 0;
602}
603
604/*
605 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
606 * someone else has a ref on the page, abort and return 0. If it was
607 * successfully detached, return 1. Assumes the caller has a single ref on
608 * this page.
609 */
610int remove_mapping(struct address_space *mapping, struct page *page)
611{
612 if (__remove_mapping(mapping, page, false)) {
613 /*
614 * Unfreezing the refcount with 1 rather than 2 effectively
615 * drops the pagecache ref for us without requiring another
616 * atomic operation.
617 */
618 page_unfreeze_refs(page, 1);
619 return 1;
620 }
621 return 0;
622}
623
624/**
625 * putback_lru_page - put previously isolated page onto appropriate LRU list
626 * @page: page to be put back to appropriate lru list
627 *
628 * Add previously isolated @page to appropriate LRU list.
629 * Page may still be unevictable for other reasons.
630 *
631 * lru_lock must not be held, interrupts must be enabled.
632 */
633void putback_lru_page(struct page *page)
634{
635 bool is_unevictable;
636 int was_unevictable = PageUnevictable(page);
637
638 VM_BUG_ON_PAGE(PageLRU(page), page);
639
640redo:
641 ClearPageUnevictable(page);
642
643 if (page_evictable(page)) {
644 /*
645 * For evictable pages, we can use the cache.
646 * In event of a race, worst case is we end up with an
647 * unevictable page on [in]active list.
648 * We know how to handle that.
649 */
650 is_unevictable = false;
651 lru_cache_add(page);
652 } else {
653 /*
654 * Put unevictable pages directly on zone's unevictable
655 * list.
656 */
657 is_unevictable = true;
658 add_page_to_unevictable_list(page);
659 /*
660 * When racing with an mlock or AS_UNEVICTABLE clearing
661 * (page is unlocked) make sure that if the other thread
662 * does not observe our setting of PG_lru and fails
663 * isolation/check_move_unevictable_pages,
664 * we see PG_mlocked/AS_UNEVICTABLE cleared below and move
665 * the page back to the evictable list.
666 *
667 * The other side is TestClearPageMlocked() or shmem_lock().
668 */
669 smp_mb();
670 }
671
672 /*
673 * page's status can change while we move it among lru. If an evictable
674 * page is on unevictable list, it never be freed. To avoid that,
675 * check after we added it to the list, again.
676 */
677 if (is_unevictable && page_evictable(page)) {
678 if (!isolate_lru_page(page)) {
679 put_page(page);
680 goto redo;
681 }
682 /* This means someone else dropped this page from LRU
683 * So, it will be freed or putback to LRU again. There is
684 * nothing to do here.
685 */
686 }
687
688 if (was_unevictable && !is_unevictable)
689 count_vm_event(UNEVICTABLE_PGRESCUED);
690 else if (!was_unevictable && is_unevictable)
691 count_vm_event(UNEVICTABLE_PGCULLED);
692
693 put_page(page); /* drop ref from isolate */
694}
695
696enum page_references {
697 PAGEREF_RECLAIM,
698 PAGEREF_RECLAIM_CLEAN,
699 PAGEREF_KEEP,
700 PAGEREF_ACTIVATE,
701};
702
703static enum page_references page_check_references(struct page *page,
704 struct scan_control *sc)
705{
706 int referenced_ptes, referenced_page;
707 unsigned long vm_flags;
708
709 referenced_ptes = page_referenced(page, 1, sc->target_mem_cgroup,
710 &vm_flags);
711 referenced_page = TestClearPageReferenced(page);
712
713 /*
714 * Mlock lost the isolation race with us. Let try_to_unmap()
715 * move the page to the unevictable list.
716 */
717 if (vm_flags & VM_LOCKED)
718 return PAGEREF_RECLAIM;
719
720 if (referenced_ptes) {
721 if (PageSwapBacked(page))
722 return PAGEREF_ACTIVATE;
723 /*
724 * All mapped pages start out with page table
725 * references from the instantiating fault, so we need
726 * to look twice if a mapped file page is used more
727 * than once.
728 *
729 * Mark it and spare it for another trip around the
730 * inactive list. Another page table reference will
731 * lead to its activation.
732 *
733 * Note: the mark is set for activated pages as well
734 * so that recently deactivated but used pages are
735 * quickly recovered.
736 */
737 SetPageReferenced(page);
738
739 if (referenced_page || referenced_ptes > 1)
740 return PAGEREF_ACTIVATE;
741
742 /*
743 * Activate file-backed executable pages after first usage.
744 */
745 if (vm_flags & VM_EXEC)
746 return PAGEREF_ACTIVATE;
747
748 return PAGEREF_KEEP;
749 }
750
751 /* Reclaim if clean, defer dirty pages to writeback */
752 if (referenced_page && !PageSwapBacked(page))
753 return PAGEREF_RECLAIM_CLEAN;
754
755 return PAGEREF_RECLAIM;
756}
757
758/* Check if a page is dirty or under writeback */
759static void page_check_dirty_writeback(struct page *page,
760 bool *dirty, bool *writeback)
761{
762 struct address_space *mapping;
763
764 /*
765 * Anonymous pages are not handled by flushers and must be written
766 * from reclaim context. Do not stall reclaim based on them
767 */
768 if (!page_is_file_cache(page)) {
769 *dirty = false;
770 *writeback = false;
771 return;
772 }
773
774 /* By default assume that the page flags are accurate */
775 *dirty = PageDirty(page);
776 *writeback = PageWriteback(page);
777
778 /* Verify dirty/writeback state if the filesystem supports it */
779 if (!page_has_private(page))
780 return;
781
782 mapping = page_mapping(page);
783 if (mapping && mapping->a_ops->is_dirty_writeback)
784 mapping->a_ops->is_dirty_writeback(page, dirty, writeback);
785}
786
787/*
788 * shrink_page_list() returns the number of reclaimed pages
789 */
790static unsigned long shrink_page_list(struct list_head *page_list,
791 struct zone *zone,
792 struct scan_control *sc,
793 enum ttu_flags ttu_flags,
794 unsigned long *ret_nr_dirty,
795 unsigned long *ret_nr_unqueued_dirty,
796 unsigned long *ret_nr_congested,
797 unsigned long *ret_nr_writeback,
798 unsigned long *ret_nr_immediate,
799 bool force_reclaim)
800{
801 LIST_HEAD(ret_pages);
802 LIST_HEAD(free_pages);
803 int pgactivate = 0;
804 unsigned long nr_unqueued_dirty = 0;
805 unsigned long nr_dirty = 0;
806 unsigned long nr_congested = 0;
807 unsigned long nr_reclaimed = 0;
808 unsigned long nr_writeback = 0;
809 unsigned long nr_immediate = 0;
810
811 cond_resched();
812
813 mem_cgroup_uncharge_start();
814 while (!list_empty(page_list)) {
815 struct address_space *mapping;
816 struct page *page;
817 int may_enter_fs;
818 enum page_references references = PAGEREF_RECLAIM_CLEAN;
819 bool dirty, writeback;
820
821 cond_resched();
822
823 page = lru_to_page(page_list);
824 list_del(&page->lru);
825
826 if (!trylock_page(page))
827 goto keep;
828
829 VM_BUG_ON_PAGE(PageActive(page), page);
830 VM_BUG_ON_PAGE(page_zone(page) != zone, page);
831
832 sc->nr_scanned++;
833
834 if (unlikely(!page_evictable(page)))
835 goto cull_mlocked;
836
837 if (!sc->may_unmap && page_mapped(page))
838 goto keep_locked;
839
840 /* Double the slab pressure for mapped and swapcache pages */
841 if (page_mapped(page) || PageSwapCache(page))
842 sc->nr_scanned++;
843
844 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
845 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
846
847 /*
848 * The number of dirty pages determines if a zone is marked
849 * reclaim_congested which affects wait_iff_congested. kswapd
850 * will stall and start writing pages if the tail of the LRU
851 * is all dirty unqueued pages.
852 */
853 page_check_dirty_writeback(page, &dirty, &writeback);
854 if (dirty || writeback)
855 nr_dirty++;
856
857 if (dirty && !writeback)
858 nr_unqueued_dirty++;
859
860 /*
861 * Treat this page as congested if the underlying BDI is or if
862 * pages are cycling through the LRU so quickly that the
863 * pages marked for immediate reclaim are making it to the
864 * end of the LRU a second time.
865 */
866 mapping = page_mapping(page);
867 if ((mapping && bdi_write_congested(mapping->backing_dev_info)) ||
868 (writeback && PageReclaim(page)))
869 nr_congested++;
870
871 /*
872 * If a page at the tail of the LRU is under writeback, there
873 * are three cases to consider.
874 *
875 * 1) If reclaim is encountering an excessive number of pages
876 * under writeback and this page is both under writeback and
877 * PageReclaim then it indicates that pages are being queued
878 * for IO but are being recycled through the LRU before the
879 * IO can complete. Waiting on the page itself risks an
880 * indefinite stall if it is impossible to writeback the
881 * page due to IO error or disconnected storage so instead
882 * note that the LRU is being scanned too quickly and the
883 * caller can stall after page list has been processed.
884 *
885 * 2) Global reclaim encounters a page, memcg encounters a
886 * page that is not marked for immediate reclaim or
887 * the caller does not have __GFP_IO. In this case mark
888 * the page for immediate reclaim and continue scanning.
889 *
890 * __GFP_IO is checked because a loop driver thread might
891 * enter reclaim, and deadlock if it waits on a page for
892 * which it is needed to do the write (loop masks off
893 * __GFP_IO|__GFP_FS for this reason); but more thought
894 * would probably show more reasons.
895 *
896 * Don't require __GFP_FS, since we're not going into the
897 * FS, just waiting on its writeback completion. Worryingly,
898 * ext4 gfs2 and xfs allocate pages with
899 * grab_cache_page_write_begin(,,AOP_FLAG_NOFS), so testing
900 * may_enter_fs here is liable to OOM on them.
901 *
902 * 3) memcg encounters a page that is not already marked
903 * PageReclaim. memcg does not have any dirty pages
904 * throttling so we could easily OOM just because too many
905 * pages are in writeback and there is nothing else to
906 * reclaim. Wait for the writeback to complete.
907 */
908 if (PageWriteback(page)) {
909 /* Case 1 above */
910 if (current_is_kswapd() &&
911 PageReclaim(page) &&
912 zone_is_reclaim_writeback(zone)) {
913 nr_immediate++;
914 goto keep_locked;
915
916 /* Case 2 above */
917 } else if (global_reclaim(sc) ||
918 !PageReclaim(page) || !(sc->gfp_mask & __GFP_IO)) {
919 /*
920 * This is slightly racy - end_page_writeback()
921 * might have just cleared PageReclaim, then
922 * setting PageReclaim here end up interpreted
923 * as PageReadahead - but that does not matter
924 * enough to care. What we do want is for this
925 * page to have PageReclaim set next time memcg
926 * reclaim reaches the tests above, so it will
927 * then wait_on_page_writeback() to avoid OOM;
928 * and it's also appropriate in global reclaim.
929 */
930 SetPageReclaim(page);
931 nr_writeback++;
932
933 goto keep_locked;
934
935 /* Case 3 above */
936 } else {
937 wait_on_page_writeback(page);
938 }
939 }
940
941 if (!force_reclaim)
942 references = page_check_references(page, sc);
943
944 switch (references) {
945 case PAGEREF_ACTIVATE:
946 goto activate_locked;
947 case PAGEREF_KEEP:
948 goto keep_locked;
949 case PAGEREF_RECLAIM:
950 case PAGEREF_RECLAIM_CLEAN:
951 ; /* try to reclaim the page below */
952 }
953
954 /*
955 * Anonymous process memory has backing store?
956 * Try to allocate it some swap space here.
957 */
958 if (PageAnon(page) && !PageSwapCache(page)) {
959 if (!(sc->gfp_mask & __GFP_IO))
960 goto keep_locked;
961 if (!add_to_swap(page, page_list))
962 goto activate_locked;
963 may_enter_fs = 1;
964
965 /* Adding to swap updated mapping */
966 mapping = page_mapping(page);
967 }
968
969 /*
970 * The page is mapped into the page tables of one or more
971 * processes. Try to unmap it here.
972 */
973 if (page_mapped(page) && mapping) {
974 switch (try_to_unmap(page, ttu_flags)) {
975 case SWAP_FAIL:
976 goto activate_locked;
977 case SWAP_AGAIN:
978 goto keep_locked;
979 case SWAP_MLOCK:
980 goto cull_mlocked;
981 case SWAP_SUCCESS:
982 ; /* try to free the page below */
983 }
984 }
985
986 if (PageDirty(page)) {
987 /*
988 * Only kswapd can writeback filesystem pages to
989 * avoid risk of stack overflow but only writeback
990 * if many dirty pages have been encountered.
991 */
992 if (page_is_file_cache(page) &&
993 (!current_is_kswapd() ||
994 !zone_is_reclaim_dirty(zone))) {
995 /*
996 * Immediately reclaim when written back.
997 * Similar in principal to deactivate_page()
998 * except we already have the page isolated
999 * and know it's dirty
1000 */
1001 inc_zone_page_state(page, NR_VMSCAN_IMMEDIATE);
1002 SetPageReclaim(page);
1003
1004 goto keep_locked;
1005 }
1006
1007 if (references == PAGEREF_RECLAIM_CLEAN)
1008 goto keep_locked;
1009 if (!may_enter_fs)
1010 goto keep_locked;
1011 if (!sc->may_writepage)
1012 goto keep_locked;
1013
1014 /* Page is dirty, try to write it out here */
1015 switch (pageout(page, mapping, sc)) {
1016 case PAGE_KEEP:
1017 goto keep_locked;
1018 case PAGE_ACTIVATE:
1019 goto activate_locked;
1020 case PAGE_SUCCESS:
1021 if (PageWriteback(page))
1022 goto keep;
1023 if (PageDirty(page))
1024 goto keep;
1025
1026 /*
1027 * A synchronous write - probably a ramdisk. Go
1028 * ahead and try to reclaim the page.
1029 */
1030 if (!trylock_page(page))
1031 goto keep;
1032 if (PageDirty(page) || PageWriteback(page))
1033 goto keep_locked;
1034 mapping = page_mapping(page);
1035 case PAGE_CLEAN:
1036 ; /* try to free the page below */
1037 }
1038 }
1039
1040 /*
1041 * If the page has buffers, try to free the buffer mappings
1042 * associated with this page. If we succeed we try to free
1043 * the page as well.
1044 *
1045 * We do this even if the page is PageDirty().
1046 * try_to_release_page() does not perform I/O, but it is
1047 * possible for a page to have PageDirty set, but it is actually
1048 * clean (all its buffers are clean). This happens if the
1049 * buffers were written out directly, with submit_bh(). ext3
1050 * will do this, as well as the blockdev mapping.
1051 * try_to_release_page() will discover that cleanness and will
1052 * drop the buffers and mark the page clean - it can be freed.
1053 *
1054 * Rarely, pages can have buffers and no ->mapping. These are
1055 * the pages which were not successfully invalidated in
1056 * truncate_complete_page(). We try to drop those buffers here
1057 * and if that worked, and the page is no longer mapped into
1058 * process address space (page_count == 1) it can be freed.
1059 * Otherwise, leave the page on the LRU so it is swappable.
1060 */
1061 if (page_has_private(page)) {
1062 if (!try_to_release_page(page, sc->gfp_mask))
1063 goto activate_locked;
1064 if (!mapping && page_count(page) == 1) {
1065 unlock_page(page);
1066 if (put_page_testzero(page))
1067 goto free_it;
1068 else {
1069 /*
1070 * rare race with speculative reference.
1071 * the speculative reference will free
1072 * this page shortly, so we may
1073 * increment nr_reclaimed here (and
1074 * leave it off the LRU).
1075 */
1076 nr_reclaimed++;
1077 continue;
1078 }
1079 }
1080 }
1081
1082 if (!mapping || !__remove_mapping(mapping, page, true))
1083 goto keep_locked;
1084
1085 /*
1086 * At this point, we have no other references and there is
1087 * no way to pick any more up (removed from LRU, removed
1088 * from pagecache). Can use non-atomic bitops now (and
1089 * we obviously don't have to worry about waking up a process
1090 * waiting on the page lock, because there are no references.
1091 */
1092 __clear_page_locked(page);
1093free_it:
1094 nr_reclaimed++;
1095
1096 /*
1097 * Is there need to periodically free_page_list? It would
1098 * appear not as the counts should be low
1099 */
1100 list_add(&page->lru, &free_pages);
1101 continue;
1102
1103cull_mlocked:
1104 if (PageSwapCache(page))
1105 try_to_free_swap(page);
1106 unlock_page(page);
1107 putback_lru_page(page);
1108 continue;
1109
1110activate_locked:
1111 /* Not a candidate for swapping, so reclaim swap space. */
1112 if (PageSwapCache(page) && vm_swap_full())
1113 try_to_free_swap(page);
1114 VM_BUG_ON_PAGE(PageActive(page), page);
1115 SetPageActive(page);
1116 pgactivate++;
1117keep_locked:
1118 unlock_page(page);
1119keep:
1120 list_add(&page->lru, &ret_pages);
1121 VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page), page);
1122 }
1123
1124 free_hot_cold_page_list(&free_pages, 1);
1125
1126 list_splice(&ret_pages, page_list);
1127 count_vm_events(PGACTIVATE, pgactivate);
1128 mem_cgroup_uncharge_end();
1129 *ret_nr_dirty += nr_dirty;
1130 *ret_nr_congested += nr_congested;
1131 *ret_nr_unqueued_dirty += nr_unqueued_dirty;
1132 *ret_nr_writeback += nr_writeback;
1133 *ret_nr_immediate += nr_immediate;
1134 return nr_reclaimed;
1135}
1136
1137unsigned long reclaim_clean_pages_from_list(struct zone *zone,
1138 struct list_head *page_list)
1139{
1140 struct scan_control sc = {
1141 .gfp_mask = GFP_KERNEL,
1142 .priority = DEF_PRIORITY,
1143 .may_unmap = 1,
1144 };
1145 unsigned long ret, dummy1, dummy2, dummy3, dummy4, dummy5;
1146 struct page *page, *next;
1147 LIST_HEAD(clean_pages);
1148
1149 list_for_each_entry_safe(page, next, page_list, lru) {
1150 if (page_is_file_cache(page) && !PageDirty(page) &&
1151 !isolated_balloon_page(page)) {
1152 ClearPageActive(page);
1153 list_move(&page->lru, &clean_pages);
1154 }
1155 }
1156
1157 ret = shrink_page_list(&clean_pages, zone, &sc,
1158 TTU_UNMAP|TTU_IGNORE_ACCESS,
1159 &dummy1, &dummy2, &dummy3, &dummy4, &dummy5, true);
1160 list_splice(&clean_pages, page_list);
1161 mod_zone_page_state(zone, NR_ISOLATED_FILE, -ret);
1162 return ret;
1163}
1164
1165/*
1166 * Attempt to remove the specified page from its LRU. Only take this page
1167 * if it is of the appropriate PageActive status. Pages which are being
1168 * freed elsewhere are also ignored.
1169 *
1170 * page: page to consider
1171 * mode: one of the LRU isolation modes defined above
1172 *
1173 * returns 0 on success, -ve errno on failure.
1174 */
1175int __isolate_lru_page(struct page *page, isolate_mode_t mode)
1176{
1177 int ret = -EINVAL;
1178
1179 /* Only take pages on the LRU. */
1180 if (!PageLRU(page))
1181 return ret;
1182
1183 /* Compaction should not handle unevictable pages but CMA can do so */
1184 if (PageUnevictable(page) && !(mode & ISOLATE_UNEVICTABLE))
1185 return ret;
1186
1187 ret = -EBUSY;
1188
1189 /*
1190 * To minimise LRU disruption, the caller can indicate that it only
1191 * wants to isolate pages it will be able to operate on without
1192 * blocking - clean pages for the most part.
1193 *
1194 * ISOLATE_CLEAN means that only clean pages should be isolated. This
1195 * is used by reclaim when it is cannot write to backing storage
1196 *
1197 * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages
1198 * that it is possible to migrate without blocking
1199 */
1200 if (mode & (ISOLATE_CLEAN|ISOLATE_ASYNC_MIGRATE)) {
1201 /* All the caller can do on PageWriteback is block */
1202 if (PageWriteback(page))
1203 return ret;
1204
1205 if (PageDirty(page)) {
1206 struct address_space *mapping;
1207
1208 /* ISOLATE_CLEAN means only clean pages */
1209 if (mode & ISOLATE_CLEAN)
1210 return ret;
1211
1212 /*
1213 * Only pages without mappings or that have a
1214 * ->migratepage callback are possible to migrate
1215 * without blocking
1216 */
1217 mapping = page_mapping(page);
1218 if (mapping && !mapping->a_ops->migratepage)
1219 return ret;
1220 }
1221 }
1222
1223 if ((mode & ISOLATE_UNMAPPED) && page_mapped(page))
1224 return ret;
1225
1226 if (likely(get_page_unless_zero(page))) {
1227 /*
1228 * Be careful not to clear PageLRU until after we're
1229 * sure the page is not being freed elsewhere -- the
1230 * page release code relies on it.
1231 */
1232 ClearPageLRU(page);
1233 ret = 0;
1234 }
1235
1236 return ret;
1237}
1238
1239/*
1240 * zone->lru_lock is heavily contended. Some of the functions that
1241 * shrink the lists perform better by taking out a batch of pages
1242 * and working on them outside the LRU lock.
1243 *
1244 * For pagecache intensive workloads, this function is the hottest
1245 * spot in the kernel (apart from copy_*_user functions).
1246 *
1247 * Appropriate locks must be held before calling this function.
1248 *
1249 * @nr_to_scan: The number of pages to look through on the list.
1250 * @lruvec: The LRU vector to pull pages from.
1251 * @dst: The temp list to put pages on to.
1252 * @nr_scanned: The number of pages that were scanned.
1253 * @sc: The scan_control struct for this reclaim session
1254 * @mode: One of the LRU isolation modes
1255 * @lru: LRU list id for isolating
1256 *
1257 * returns how many pages were moved onto *@dst.
1258 */
1259static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
1260 struct lruvec *lruvec, struct list_head *dst,
1261 unsigned long *nr_scanned, struct scan_control *sc,
1262 isolate_mode_t mode, enum lru_list lru)
1263{
1264 struct list_head *src = &lruvec->lists[lru];
1265 unsigned long nr_taken = 0;
1266 unsigned long scan;
1267
1268 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
1269 struct page *page;
1270 int nr_pages;
1271
1272 page = lru_to_page(src);
1273 prefetchw_prev_lru_page(page, src, flags);
1274
1275 VM_BUG_ON_PAGE(!PageLRU(page), page);
1276
1277 switch (__isolate_lru_page(page, mode)) {
1278 case 0:
1279 nr_pages = hpage_nr_pages(page);
1280 mem_cgroup_update_lru_size(lruvec, lru, -nr_pages);
1281 list_move(&page->lru, dst);
1282 nr_taken += nr_pages;
1283 break;
1284
1285 case -EBUSY:
1286 /* else it is being freed elsewhere */
1287 list_move(&page->lru, src);
1288 continue;
1289
1290 default:
1291 BUG();
1292 }
1293 }
1294
1295 *nr_scanned = scan;
1296 trace_mm_vmscan_lru_isolate(sc->order, nr_to_scan, scan,
1297 nr_taken, mode, is_file_lru(lru));
1298 return nr_taken;
1299}
1300
1301/**
1302 * isolate_lru_page - tries to isolate a page from its LRU list
1303 * @page: page to isolate from its LRU list
1304 *
1305 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1306 * vmstat statistic corresponding to whatever LRU list the page was on.
1307 *
1308 * Returns 0 if the page was removed from an LRU list.
1309 * Returns -EBUSY if the page was not on an LRU list.
1310 *
1311 * The returned page will have PageLRU() cleared. If it was found on
1312 * the active list, it will have PageActive set. If it was found on
1313 * the unevictable list, it will have the PageUnevictable bit set. That flag
1314 * may need to be cleared by the caller before letting the page go.
1315 *
1316 * The vmstat statistic corresponding to the list on which the page was
1317 * found will be decremented.
1318 *
1319 * Restrictions:
1320 * (1) Must be called with an elevated refcount on the page. This is a
1321 * fundamentnal difference from isolate_lru_pages (which is called
1322 * without a stable reference).
1323 * (2) the lru_lock must not be held.
1324 * (3) interrupts must be enabled.
1325 */
1326int isolate_lru_page(struct page *page)
1327{
1328 int ret = -EBUSY;
1329
1330 VM_BUG_ON_PAGE(!page_count(page), page);
1331
1332 if (PageLRU(page)) {
1333 struct zone *zone = page_zone(page);
1334 struct lruvec *lruvec;
1335
1336 spin_lock_irq(&zone->lru_lock);
1337 lruvec = mem_cgroup_page_lruvec(page, zone);
1338 if (PageLRU(page)) {
1339 int lru = page_lru(page);
1340 get_page(page);
1341 ClearPageLRU(page);
1342 del_page_from_lru_list(page, lruvec, lru);
1343 ret = 0;
1344 }
1345 spin_unlock_irq(&zone->lru_lock);
1346 }
1347 return ret;
1348}
1349
1350/*
1351 * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and
1352 * then get resheduled. When there are massive number of tasks doing page
1353 * allocation, such sleeping direct reclaimers may keep piling up on each CPU,
1354 * the LRU list will go small and be scanned faster than necessary, leading to
1355 * unnecessary swapping, thrashing and OOM.
1356 */
1357static int too_many_isolated(struct zone *zone, int file,
1358 struct scan_control *sc)
1359{
1360 unsigned long inactive, isolated;
1361
1362 if (current_is_kswapd())
1363 return 0;
1364
1365 if (!global_reclaim(sc))
1366 return 0;
1367
1368 if (file) {
1369 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1370 isolated = zone_page_state(zone, NR_ISOLATED_FILE);
1371 } else {
1372 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1373 isolated = zone_page_state(zone, NR_ISOLATED_ANON);
1374 }
1375
1376 /*
1377 * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they
1378 * won't get blocked by normal direct-reclaimers, forming a circular
1379 * deadlock.
1380 */
1381 if ((sc->gfp_mask & GFP_IOFS) == GFP_IOFS)
1382 inactive >>= 3;
1383
1384 return isolated > inactive;
1385}
1386
1387static noinline_for_stack void
1388putback_inactive_pages(struct lruvec *lruvec, struct list_head *page_list)
1389{
1390 struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
1391 struct zone *zone = lruvec_zone(lruvec);
1392 LIST_HEAD(pages_to_free);
1393
1394 /*
1395 * Put back any unfreeable pages.
1396 */
1397 while (!list_empty(page_list)) {
1398 struct page *page = lru_to_page(page_list);
1399 int lru;
1400
1401 VM_BUG_ON_PAGE(PageLRU(page), page);
1402 list_del(&page->lru);
1403 if (unlikely(!page_evictable(page))) {
1404 spin_unlock_irq(&zone->lru_lock);
1405 putback_lru_page(page);
1406 spin_lock_irq(&zone->lru_lock);
1407 continue;
1408 }
1409
1410 lruvec = mem_cgroup_page_lruvec(page, zone);
1411
1412 SetPageLRU(page);
1413 lru = page_lru(page);
1414 add_page_to_lru_list(page, lruvec, lru);
1415
1416 if (is_active_lru(lru)) {
1417 int file = is_file_lru(lru);
1418 int numpages = hpage_nr_pages(page);
1419 reclaim_stat->recent_rotated[file] += numpages;
1420 }
1421 if (put_page_testzero(page)) {
1422 __ClearPageLRU(page);
1423 __ClearPageActive(page);
1424 del_page_from_lru_list(page, lruvec, lru);
1425
1426 if (unlikely(PageCompound(page))) {
1427 spin_unlock_irq(&zone->lru_lock);
1428 (*get_compound_page_dtor(page))(page);
1429 spin_lock_irq(&zone->lru_lock);
1430 } else
1431 list_add(&page->lru, &pages_to_free);
1432 }
1433 }
1434
1435 /*
1436 * To save our caller's stack, now use input list for pages to free.
1437 */
1438 list_splice(&pages_to_free, page_list);
1439}
1440
1441/*
1442 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1443 * of reclaimed pages
1444 */
1445static noinline_for_stack unsigned long
1446shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
1447 struct scan_control *sc, enum lru_list lru)
1448{
1449 LIST_HEAD(page_list);
1450 unsigned long nr_scanned;
1451 unsigned long nr_reclaimed = 0;
1452 unsigned long nr_taken;
1453 unsigned long nr_dirty = 0;
1454 unsigned long nr_congested = 0;
1455 unsigned long nr_unqueued_dirty = 0;
1456 unsigned long nr_writeback = 0;
1457 unsigned long nr_immediate = 0;
1458 isolate_mode_t isolate_mode = 0;
1459 int file = is_file_lru(lru);
1460 struct zone *zone = lruvec_zone(lruvec);
1461 struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
1462
1463 while (unlikely(too_many_isolated(zone, file, sc))) {
1464 congestion_wait(BLK_RW_ASYNC, HZ/10);
1465
1466 /* We are about to die and free our memory. Return now. */
1467 if (fatal_signal_pending(current))
1468 return SWAP_CLUSTER_MAX;
1469 }
1470
1471 lru_add_drain();
1472
1473 if (!sc->may_unmap)
1474 isolate_mode |= ISOLATE_UNMAPPED;
1475 if (!sc->may_writepage)
1476 isolate_mode |= ISOLATE_CLEAN;
1477
1478 spin_lock_irq(&zone->lru_lock);
1479
1480 nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &page_list,
1481 &nr_scanned, sc, isolate_mode, lru);
1482
1483 __mod_zone_page_state(zone, NR_LRU_BASE + lru, -nr_taken);
1484 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
1485
1486 if (global_reclaim(sc)) {
1487 zone->pages_scanned += nr_scanned;
1488 if (current_is_kswapd())
1489 __count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scanned);
1490 else
1491 __count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scanned);
1492 }
1493 spin_unlock_irq(&zone->lru_lock);
1494
1495 if (nr_taken == 0)
1496 return 0;
1497
1498 nr_reclaimed = shrink_page_list(&page_list, zone, sc, TTU_UNMAP,
1499 &nr_dirty, &nr_unqueued_dirty, &nr_congested,
1500 &nr_writeback, &nr_immediate,
1501 false);
1502
1503 spin_lock_irq(&zone->lru_lock);
1504
1505 reclaim_stat->recent_scanned[file] += nr_taken;
1506
1507 if (global_reclaim(sc)) {
1508 if (current_is_kswapd())
1509 __count_zone_vm_events(PGSTEAL_KSWAPD, zone,
1510 nr_reclaimed);
1511 else
1512 __count_zone_vm_events(PGSTEAL_DIRECT, zone,
1513 nr_reclaimed);
1514 }
1515
1516 putback_inactive_pages(lruvec, &page_list);
1517
1518 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1519
1520 spin_unlock_irq(&zone->lru_lock);
1521
1522 free_hot_cold_page_list(&page_list, 1);
1523
1524 /*
1525 * If reclaim is isolating dirty pages under writeback, it implies
1526 * that the long-lived page allocation rate is exceeding the page
1527 * laundering rate. Either the global limits are not being effective
1528 * at throttling processes due to the page distribution throughout
1529 * zones or there is heavy usage of a slow backing device. The
1530 * only option is to throttle from reclaim context which is not ideal
1531 * as there is no guarantee the dirtying process is throttled in the
1532 * same way balance_dirty_pages() manages.
1533 *
1534 * Once a zone is flagged ZONE_WRITEBACK, kswapd will count the number
1535 * of pages under pages flagged for immediate reclaim and stall if any
1536 * are encountered in the nr_immediate check below.
1537 */
1538 if (nr_writeback && nr_writeback == nr_taken)
1539 zone_set_flag(zone, ZONE_WRITEBACK);
1540
1541 /*
1542 * memcg will stall in page writeback so only consider forcibly
1543 * stalling for global reclaim
1544 */
1545 if (global_reclaim(sc)) {
1546 /*
1547 * Tag a zone as congested if all the dirty pages scanned were
1548 * backed by a congested BDI and wait_iff_congested will stall.
1549 */
1550 if (nr_dirty && nr_dirty == nr_congested)
1551 zone_set_flag(zone, ZONE_CONGESTED);
1552
1553 /*
1554 * If dirty pages are scanned that are not queued for IO, it
1555 * implies that flushers are not keeping up. In this case, flag
1556 * the zone ZONE_TAIL_LRU_DIRTY and kswapd will start writing
1557 * pages from reclaim context. It will forcibly stall in the
1558 * next check.
1559 */
1560 if (nr_unqueued_dirty == nr_taken)
1561 zone_set_flag(zone, ZONE_TAIL_LRU_DIRTY);
1562
1563 /*
1564 * In addition, if kswapd scans pages marked marked for
1565 * immediate reclaim and under writeback (nr_immediate), it
1566 * implies that pages are cycling through the LRU faster than
1567 * they are written so also forcibly stall.
1568 */
1569 if (nr_unqueued_dirty == nr_taken || nr_immediate)
1570 congestion_wait(BLK_RW_ASYNC, HZ/10);
1571 }
1572
1573 /*
1574 * Stall direct reclaim for IO completions if underlying BDIs or zone
1575 * is congested. Allow kswapd to continue until it starts encountering
1576 * unqueued dirty pages or cycling through the LRU too quickly.
1577 */
1578 if (!sc->hibernation_mode && !current_is_kswapd())
1579 wait_iff_congested(zone, BLK_RW_ASYNC, HZ/10);
1580
1581 trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id,
1582 zone_idx(zone),
1583 nr_scanned, nr_reclaimed,
1584 sc->priority,
1585 trace_shrink_flags(file));
1586 return nr_reclaimed;
1587}
1588
1589/*
1590 * This moves pages from the active list to the inactive list.
1591 *
1592 * We move them the other way if the page is referenced by one or more
1593 * processes, from rmap.
1594 *
1595 * If the pages are mostly unmapped, the processing is fast and it is
1596 * appropriate to hold zone->lru_lock across the whole operation. But if
1597 * the pages are mapped, the processing is slow (page_referenced()) so we
1598 * should drop zone->lru_lock around each page. It's impossible to balance
1599 * this, so instead we remove the pages from the LRU while processing them.
1600 * It is safe to rely on PG_active against the non-LRU pages in here because
1601 * nobody will play with that bit on a non-LRU page.
1602 *
1603 * The downside is that we have to touch page->_count against each page.
1604 * But we had to alter page->flags anyway.
1605 */
1606
1607static void move_active_pages_to_lru(struct lruvec *lruvec,
1608 struct list_head *list,
1609 struct list_head *pages_to_free,
1610 enum lru_list lru)
1611{
1612 struct zone *zone = lruvec_zone(lruvec);
1613 unsigned long pgmoved = 0;
1614 struct page *page;
1615 int nr_pages;
1616
1617 while (!list_empty(list)) {
1618 page = lru_to_page(list);
1619 lruvec = mem_cgroup_page_lruvec(page, zone);
1620
1621 VM_BUG_ON_PAGE(PageLRU(page), page);
1622 SetPageLRU(page);
1623
1624 nr_pages = hpage_nr_pages(page);
1625 mem_cgroup_update_lru_size(lruvec, lru, nr_pages);
1626 list_move(&page->lru, &lruvec->lists[lru]);
1627 pgmoved += nr_pages;
1628
1629 if (put_page_testzero(page)) {
1630 __ClearPageLRU(page);
1631 __ClearPageActive(page);
1632 del_page_from_lru_list(page, lruvec, lru);
1633
1634 if (unlikely(PageCompound(page))) {
1635 spin_unlock_irq(&zone->lru_lock);
1636 (*get_compound_page_dtor(page))(page);
1637 spin_lock_irq(&zone->lru_lock);
1638 } else
1639 list_add(&page->lru, pages_to_free);
1640 }
1641 }
1642 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1643 if (!is_active_lru(lru))
1644 __count_vm_events(PGDEACTIVATE, pgmoved);
1645}
1646
1647static void shrink_active_list(unsigned long nr_to_scan,
1648 struct lruvec *lruvec,
1649 struct scan_control *sc,
1650 enum lru_list lru)
1651{
1652 unsigned long nr_taken;
1653 unsigned long nr_scanned;
1654 unsigned long vm_flags;
1655 LIST_HEAD(l_hold); /* The pages which were snipped off */
1656 LIST_HEAD(l_active);
1657 LIST_HEAD(l_inactive);
1658 struct page *page;
1659 struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
1660 unsigned long nr_rotated = 0;
1661 isolate_mode_t isolate_mode = 0;
1662 int file = is_file_lru(lru);
1663 struct zone *zone = lruvec_zone(lruvec);
1664
1665 lru_add_drain();
1666
1667 if (!sc->may_unmap)
1668 isolate_mode |= ISOLATE_UNMAPPED;
1669 if (!sc->may_writepage)
1670 isolate_mode |= ISOLATE_CLEAN;
1671
1672 spin_lock_irq(&zone->lru_lock);
1673
1674 nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &l_hold,
1675 &nr_scanned, sc, isolate_mode, lru);
1676 if (global_reclaim(sc))
1677 zone->pages_scanned += nr_scanned;
1678
1679 reclaim_stat->recent_scanned[file] += nr_taken;
1680
1681 __count_zone_vm_events(PGREFILL, zone, nr_scanned);
1682 __mod_zone_page_state(zone, NR_LRU_BASE + lru, -nr_taken);
1683 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
1684 spin_unlock_irq(&zone->lru_lock);
1685
1686 while (!list_empty(&l_hold)) {
1687 cond_resched();
1688 page = lru_to_page(&l_hold);
1689 list_del(&page->lru);
1690
1691 if (unlikely(!page_evictable(page))) {
1692 putback_lru_page(page);
1693 continue;
1694 }
1695
1696 if (unlikely(buffer_heads_over_limit)) {
1697 if (page_has_private(page) && trylock_page(page)) {
1698 if (page_has_private(page))
1699 try_to_release_page(page, 0);
1700 unlock_page(page);
1701 }
1702 }
1703
1704 if (page_referenced(page, 0, sc->target_mem_cgroup,
1705 &vm_flags)) {
1706 nr_rotated += hpage_nr_pages(page);
1707 /*
1708 * Identify referenced, file-backed active pages and
1709 * give them one more trip around the active list. So
1710 * that executable code get better chances to stay in
1711 * memory under moderate memory pressure. Anon pages
1712 * are not likely to be evicted by use-once streaming
1713 * IO, plus JVM can create lots of anon VM_EXEC pages,
1714 * so we ignore them here.
1715 */
1716 if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
1717 list_add(&page->lru, &l_active);
1718 continue;
1719 }
1720 }
1721
1722 ClearPageActive(page); /* we are de-activating */
1723 list_add(&page->lru, &l_inactive);
1724 }
1725
1726 /*
1727 * Move pages back to the lru list.
1728 */
1729 spin_lock_irq(&zone->lru_lock);
1730 /*
1731 * Count referenced pages from currently used mappings as rotated,
1732 * even though only some of them are actually re-activated. This
1733 * helps balance scan pressure between file and anonymous pages in
1734 * get_scan_ratio.
1735 */
1736 reclaim_stat->recent_rotated[file] += nr_rotated;
1737
1738 move_active_pages_to_lru(lruvec, &l_active, &l_hold, lru);
1739 move_active_pages_to_lru(lruvec, &l_inactive, &l_hold, lru - LRU_ACTIVE);
1740 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1741 spin_unlock_irq(&zone->lru_lock);
1742
1743 free_hot_cold_page_list(&l_hold, 1);
1744}
1745
1746#ifdef CONFIG_SWAP
1747static int inactive_anon_is_low_global(struct zone *zone)
1748{
1749 unsigned long active, inactive;
1750
1751 active = zone_page_state(zone, NR_ACTIVE_ANON);
1752 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1753
1754 if (inactive * zone->inactive_ratio < active)
1755 return 1;
1756
1757 return 0;
1758}
1759
1760/**
1761 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1762 * @lruvec: LRU vector to check
1763 *
1764 * Returns true if the zone does not have enough inactive anon pages,
1765 * meaning some active anon pages need to be deactivated.
1766 */
1767static int inactive_anon_is_low(struct lruvec *lruvec)
1768{
1769 /*
1770 * If we don't have swap space, anonymous page deactivation
1771 * is pointless.
1772 */
1773 if (!total_swap_pages)
1774 return 0;
1775
1776 if (!mem_cgroup_disabled())
1777 return mem_cgroup_inactive_anon_is_low(lruvec);
1778
1779 return inactive_anon_is_low_global(lruvec_zone(lruvec));
1780}
1781#else
1782static inline int inactive_anon_is_low(struct lruvec *lruvec)
1783{
1784 return 0;
1785}
1786#endif
1787
1788/**
1789 * inactive_file_is_low - check if file pages need to be deactivated
1790 * @lruvec: LRU vector to check
1791 *
1792 * When the system is doing streaming IO, memory pressure here
1793 * ensures that active file pages get deactivated, until more
1794 * than half of the file pages are on the inactive list.
1795 *
1796 * Once we get to that situation, protect the system's working
1797 * set from being evicted by disabling active file page aging.
1798 *
1799 * This uses a different ratio than the anonymous pages, because
1800 * the page cache uses a use-once replacement algorithm.
1801 */
1802static int inactive_file_is_low(struct lruvec *lruvec)
1803{
1804 unsigned long inactive;
1805 unsigned long active;
1806
1807 inactive = get_lru_size(lruvec, LRU_INACTIVE_FILE);
1808 active = get_lru_size(lruvec, LRU_ACTIVE_FILE);
1809
1810 return active > inactive;
1811}
1812
1813static int inactive_list_is_low(struct lruvec *lruvec, enum lru_list lru)
1814{
1815 if (is_file_lru(lru))
1816 return inactive_file_is_low(lruvec);
1817 else
1818 return inactive_anon_is_low(lruvec);
1819}
1820
1821static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1822 struct lruvec *lruvec, struct scan_control *sc)
1823{
1824 if (is_active_lru(lru)) {
1825 if (inactive_list_is_low(lruvec, lru))
1826 shrink_active_list(nr_to_scan, lruvec, sc, lru);
1827 return 0;
1828 }
1829
1830 return shrink_inactive_list(nr_to_scan, lruvec, sc, lru);
1831}
1832
1833static int vmscan_swappiness(struct scan_control *sc)
1834{
1835 if (global_reclaim(sc))
1836 return vm_swappiness;
1837 return mem_cgroup_swappiness(sc->target_mem_cgroup);
1838}
1839
1840enum scan_balance {
1841 SCAN_EQUAL,
1842 SCAN_FRACT,
1843 SCAN_ANON,
1844 SCAN_FILE,
1845};
1846
1847/*
1848 * Determine how aggressively the anon and file LRU lists should be
1849 * scanned. The relative value of each set of LRU lists is determined
1850 * by looking at the fraction of the pages scanned we did rotate back
1851 * onto the active list instead of evict.
1852 *
1853 * nr[0] = anon inactive pages to scan; nr[1] = anon active pages to scan
1854 * nr[2] = file inactive pages to scan; nr[3] = file active pages to scan
1855 */
1856static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
1857 unsigned long *nr)
1858{
1859 struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
1860 u64 fraction[2];
1861 u64 denominator = 0; /* gcc */
1862 struct zone *zone = lruvec_zone(lruvec);
1863 unsigned long anon_prio, file_prio;
1864 enum scan_balance scan_balance;
1865 unsigned long anon, file;
1866 bool force_scan = false;
1867 unsigned long ap, fp;
1868 enum lru_list lru;
1869
1870 /*
1871 * If the zone or memcg is small, nr[l] can be 0. This
1872 * results in no scanning on this priority and a potential
1873 * priority drop. Global direct reclaim can go to the next
1874 * zone and tends to have no problems. Global kswapd is for
1875 * zone balancing and it needs to scan a minimum amount. When
1876 * reclaiming for a memcg, a priority drop can cause high
1877 * latencies, so it's better to scan a minimum amount there as
1878 * well.
1879 */
1880 if (current_is_kswapd() && !zone_reclaimable(zone))
1881 force_scan = true;
1882 if (!global_reclaim(sc))
1883 force_scan = true;
1884
1885 /* If we have no swap space, do not bother scanning anon pages. */
1886 if (!sc->may_swap || (get_nr_swap_pages() <= 0)) {
1887 scan_balance = SCAN_FILE;
1888 goto out;
1889 }
1890
1891 /*
1892 * Global reclaim will swap to prevent OOM even with no
1893 * swappiness, but memcg users want to use this knob to
1894 * disable swapping for individual groups completely when
1895 * using the memory controller's swap limit feature would be
1896 * too expensive.
1897 */
1898 if (!global_reclaim(sc) && !vmscan_swappiness(sc)) {
1899 scan_balance = SCAN_FILE;
1900 goto out;
1901 }
1902
1903 /*
1904 * Do not apply any pressure balancing cleverness when the
1905 * system is close to OOM, scan both anon and file equally
1906 * (unless the swappiness setting disagrees with swapping).
1907 */
1908 if (!sc->priority && vmscan_swappiness(sc)) {
1909 scan_balance = SCAN_EQUAL;
1910 goto out;
1911 }
1912
1913 anon = get_lru_size(lruvec, LRU_ACTIVE_ANON) +
1914 get_lru_size(lruvec, LRU_INACTIVE_ANON);
1915 file = get_lru_size(lruvec, LRU_ACTIVE_FILE) +
1916 get_lru_size(lruvec, LRU_INACTIVE_FILE);
1917
1918 /*
1919 * Prevent the reclaimer from falling into the cache trap: as
1920 * cache pages start out inactive, every cache fault will tip
1921 * the scan balance towards the file LRU. And as the file LRU
1922 * shrinks, so does the window for rotation from references.
1923 * This means we have a runaway feedback loop where a tiny
1924 * thrashing file LRU becomes infinitely more attractive than
1925 * anon pages. Try to detect this based on file LRU size.
1926 */
1927 if (global_reclaim(sc)) {
1928 unsigned long free = zone_page_state(zone, NR_FREE_PAGES);
1929
1930 if (unlikely(file + free <= high_wmark_pages(zone))) {
1931 scan_balance = SCAN_ANON;
1932 goto out;
1933 }
1934 }
1935
1936 /*
1937 * There is enough inactive page cache, do not reclaim
1938 * anything from the anonymous working set right now.
1939 */
1940 if (!inactive_file_is_low(lruvec)) {
1941 scan_balance = SCAN_FILE;
1942 goto out;
1943 }
1944
1945 scan_balance = SCAN_FRACT;
1946
1947 /*
1948 * With swappiness at 100, anonymous and file have the same priority.
1949 * This scanning priority is essentially the inverse of IO cost.
1950 */
1951 anon_prio = vmscan_swappiness(sc);
1952 file_prio = 200 - anon_prio;
1953
1954 /*
1955 * OK, so we have swap space and a fair amount of page cache
1956 * pages. We use the recently rotated / recently scanned
1957 * ratios to determine how valuable each cache is.
1958 *
1959 * Because workloads change over time (and to avoid overflow)
1960 * we keep these statistics as a floating average, which ends
1961 * up weighing recent references more than old ones.
1962 *
1963 * anon in [0], file in [1]
1964 */
1965 spin_lock_irq(&zone->lru_lock);
1966 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
1967 reclaim_stat->recent_scanned[0] /= 2;
1968 reclaim_stat->recent_rotated[0] /= 2;
1969 }
1970
1971 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
1972 reclaim_stat->recent_scanned[1] /= 2;
1973 reclaim_stat->recent_rotated[1] /= 2;
1974 }
1975
1976 /*
1977 * The amount of pressure on anon vs file pages is inversely
1978 * proportional to the fraction of recently scanned pages on
1979 * each list that were recently referenced and in active use.
1980 */
1981 ap = anon_prio * (reclaim_stat->recent_scanned[0] + 1);
1982 ap /= reclaim_stat->recent_rotated[0] + 1;
1983
1984 fp = file_prio * (reclaim_stat->recent_scanned[1] + 1);
1985 fp /= reclaim_stat->recent_rotated[1] + 1;
1986 spin_unlock_irq(&zone->lru_lock);
1987
1988 fraction[0] = ap;
1989 fraction[1] = fp;
1990 denominator = ap + fp + 1;
1991out:
1992 for_each_evictable_lru(lru) {
1993 int file = is_file_lru(lru);
1994 unsigned long size;
1995 unsigned long scan;
1996
1997 size = get_lru_size(lruvec, lru);
1998 scan = size >> sc->priority;
1999
2000 if (!scan && force_scan)
2001 scan = min(size, SWAP_CLUSTER_MAX);
2002
2003 switch (scan_balance) {
2004 case SCAN_EQUAL:
2005 /* Scan lists relative to size */
2006 break;
2007 case SCAN_FRACT:
2008 /*
2009 * Scan types proportional to swappiness and
2010 * their relative recent reclaim efficiency.
2011 */
2012 scan = div64_u64(scan * fraction[file], denominator);
2013 break;
2014 case SCAN_FILE:
2015 case SCAN_ANON:
2016 /* Scan one type exclusively */
2017 if ((scan_balance == SCAN_FILE) != file)
2018 scan = 0;
2019 break;
2020 default:
2021 /* Look ma, no brain */
2022 BUG();
2023 }
2024 nr[lru] = scan;
2025 }
2026}
2027
2028/*
2029 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
2030 */
2031static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
2032{
2033 unsigned long nr[NR_LRU_LISTS];
2034 unsigned long targets[NR_LRU_LISTS];
2035 unsigned long nr_to_scan;
2036 enum lru_list lru;
2037 unsigned long nr_reclaimed = 0;
2038 unsigned long nr_to_reclaim = sc->nr_to_reclaim;
2039 struct blk_plug plug;
2040 bool scan_adjusted = false;
2041
2042 get_scan_count(lruvec, sc, nr);
2043
2044 /* Record the original scan target for proportional adjustments later */
2045 memcpy(targets, nr, sizeof(nr));
2046
2047 blk_start_plug(&plug);
2048 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
2049 nr[LRU_INACTIVE_FILE]) {
2050 unsigned long nr_anon, nr_file, percentage;
2051 unsigned long nr_scanned;
2052
2053 for_each_evictable_lru(lru) {
2054 if (nr[lru]) {
2055 nr_to_scan = min(nr[lru], SWAP_CLUSTER_MAX);
2056 nr[lru] -= nr_to_scan;
2057
2058 nr_reclaimed += shrink_list(lru, nr_to_scan,
2059 lruvec, sc);
2060 }
2061 }
2062
2063 if (nr_reclaimed < nr_to_reclaim || scan_adjusted)
2064 continue;
2065
2066 /*
2067 * For global direct reclaim, reclaim only the number of pages
2068 * requested. Less care is taken to scan proportionally as it
2069 * is more important to minimise direct reclaim stall latency
2070 * than it is to properly age the LRU lists.
2071 */
2072 if (global_reclaim(sc) && !current_is_kswapd())
2073 break;
2074
2075 /*
2076 * For kswapd and memcg, reclaim at least the number of pages
2077 * requested. Ensure that the anon and file LRUs shrink
2078 * proportionally what was requested by get_scan_count(). We
2079 * stop reclaiming one LRU and reduce the amount scanning
2080 * proportional to the original scan target.
2081 */
2082 nr_file = nr[LRU_INACTIVE_FILE] + nr[LRU_ACTIVE_FILE];
2083 nr_anon = nr[LRU_INACTIVE_ANON] + nr[LRU_ACTIVE_ANON];
2084
2085 if (nr_file > nr_anon) {
2086 unsigned long scan_target = targets[LRU_INACTIVE_ANON] +
2087 targets[LRU_ACTIVE_ANON] + 1;
2088 lru = LRU_BASE;
2089 percentage = nr_anon * 100 / scan_target;
2090 } else {
2091 unsigned long scan_target = targets[LRU_INACTIVE_FILE] +
2092 targets[LRU_ACTIVE_FILE] + 1;
2093 lru = LRU_FILE;
2094 percentage = nr_file * 100 / scan_target;
2095 }
2096
2097 /* Stop scanning the smaller of the LRU */
2098 nr[lru] = 0;
2099 nr[lru + LRU_ACTIVE] = 0;
2100
2101 /*
2102 * Recalculate the other LRU scan count based on its original
2103 * scan target and the percentage scanning already complete
2104 */
2105 lru = (lru == LRU_FILE) ? LRU_BASE : LRU_FILE;
2106 nr_scanned = targets[lru] - nr[lru];
2107 nr[lru] = targets[lru] * (100 - percentage) / 100;
2108 nr[lru] -= min(nr[lru], nr_scanned);
2109
2110 lru += LRU_ACTIVE;
2111 nr_scanned = targets[lru] - nr[lru];
2112 nr[lru] = targets[lru] * (100 - percentage) / 100;
2113 nr[lru] -= min(nr[lru], nr_scanned);
2114
2115 scan_adjusted = true;
2116 }
2117 blk_finish_plug(&plug);
2118 sc->nr_reclaimed += nr_reclaimed;
2119
2120 /*
2121 * Even if we did not try to evict anon pages at all, we want to
2122 * rebalance the anon lru active/inactive ratio.
2123 */
2124 if (inactive_anon_is_low(lruvec))
2125 shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
2126 sc, LRU_ACTIVE_ANON);
2127
2128 throttle_vm_writeout(sc->gfp_mask);
2129}
2130
2131/* Use reclaim/compaction for costly allocs or under memory pressure */
2132static bool in_reclaim_compaction(struct scan_control *sc)
2133{
2134 if (IS_ENABLED(CONFIG_COMPACTION) && sc->order &&
2135 (sc->order > PAGE_ALLOC_COSTLY_ORDER ||
2136 sc->priority < DEF_PRIORITY - 2))
2137 return true;
2138
2139 return false;
2140}
2141
2142/*
2143 * Reclaim/compaction is used for high-order allocation requests. It reclaims
2144 * order-0 pages before compacting the zone. should_continue_reclaim() returns
2145 * true if more pages should be reclaimed such that when the page allocator
2146 * calls try_to_compact_zone() that it will have enough free pages to succeed.
2147 * It will give up earlier than that if there is difficulty reclaiming pages.
2148 */
2149static inline bool should_continue_reclaim(struct zone *zone,
2150 unsigned long nr_reclaimed,
2151 unsigned long nr_scanned,
2152 struct scan_control *sc)
2153{
2154 unsigned long pages_for_compaction;
2155 unsigned long inactive_lru_pages;
2156
2157 /* If not in reclaim/compaction mode, stop */
2158 if (!in_reclaim_compaction(sc))
2159 return false;
2160
2161 /* Consider stopping depending on scan and reclaim activity */
2162 if (sc->gfp_mask & __GFP_REPEAT) {
2163 /*
2164 * For __GFP_REPEAT allocations, stop reclaiming if the
2165 * full LRU list has been scanned and we are still failing
2166 * to reclaim pages. This full LRU scan is potentially
2167 * expensive but a __GFP_REPEAT caller really wants to succeed
2168 */
2169 if (!nr_reclaimed && !nr_scanned)
2170 return false;
2171 } else {
2172 /*
2173 * For non-__GFP_REPEAT allocations which can presumably
2174 * fail without consequence, stop if we failed to reclaim
2175 * any pages from the last SWAP_CLUSTER_MAX number of
2176 * pages that were scanned. This will return to the
2177 * caller faster at the risk reclaim/compaction and
2178 * the resulting allocation attempt fails
2179 */
2180 if (!nr_reclaimed)
2181 return false;
2182 }
2183
2184 /*
2185 * If we have not reclaimed enough pages for compaction and the
2186 * inactive lists are large enough, continue reclaiming
2187 */
2188 pages_for_compaction = (2UL << sc->order);
2189 inactive_lru_pages = zone_page_state(zone, NR_INACTIVE_FILE);
2190 if (get_nr_swap_pages() > 0)
2191 inactive_lru_pages += zone_page_state(zone, NR_INACTIVE_ANON);
2192 if (sc->nr_reclaimed < pages_for_compaction &&
2193 inactive_lru_pages > pages_for_compaction)
2194 return true;
2195
2196 /* If compaction would go ahead or the allocation would succeed, stop */
2197 switch (compaction_suitable(zone, sc->order)) {
2198 case COMPACT_PARTIAL:
2199 case COMPACT_CONTINUE:
2200 return false;
2201 default:
2202 return true;
2203 }
2204}
2205
2206static void shrink_zone(struct zone *zone, struct scan_control *sc)
2207{
2208 unsigned long nr_reclaimed, nr_scanned;
2209
2210 do {
2211 struct mem_cgroup *root = sc->target_mem_cgroup;
2212 struct mem_cgroup_reclaim_cookie reclaim = {
2213 .zone = zone,
2214 .priority = sc->priority,
2215 };
2216 struct mem_cgroup *memcg;
2217
2218 nr_reclaimed = sc->nr_reclaimed;
2219 nr_scanned = sc->nr_scanned;
2220
2221 memcg = mem_cgroup_iter(root, NULL, &reclaim);
2222 do {
2223 struct lruvec *lruvec;
2224
2225 lruvec = mem_cgroup_zone_lruvec(zone, memcg);
2226
2227 shrink_lruvec(lruvec, sc);
2228
2229 /*
2230 * Direct reclaim and kswapd have to scan all memory
2231 * cgroups to fulfill the overall scan target for the
2232 * zone.
2233 *
2234 * Limit reclaim, on the other hand, only cares about
2235 * nr_to_reclaim pages to be reclaimed and it will
2236 * retry with decreasing priority if one round over the
2237 * whole hierarchy is not sufficient.
2238 */
2239 if (!global_reclaim(sc) &&
2240 sc->nr_reclaimed >= sc->nr_to_reclaim) {
2241 mem_cgroup_iter_break(root, memcg);
2242 break;
2243 }
2244 memcg = mem_cgroup_iter(root, memcg, &reclaim);
2245 } while (memcg);
2246
2247 vmpressure(sc->gfp_mask, sc->target_mem_cgroup,
2248 sc->nr_scanned - nr_scanned,
2249 sc->nr_reclaimed - nr_reclaimed);
2250
2251 } while (should_continue_reclaim(zone, sc->nr_reclaimed - nr_reclaimed,
2252 sc->nr_scanned - nr_scanned, sc));
2253}
2254
2255/* Returns true if compaction should go ahead for a high-order request */
2256static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
2257{
2258 unsigned long balance_gap, watermark;
2259 bool watermark_ok;
2260
2261 /* Do not consider compaction for orders reclaim is meant to satisfy */
2262 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER)
2263 return false;
2264
2265 /*
2266 * Compaction takes time to run and there are potentially other
2267 * callers using the pages just freed. Continue reclaiming until
2268 * there is a buffer of free pages available to give compaction
2269 * a reasonable chance of completing and allocating the page
2270 */
2271 balance_gap = min(low_wmark_pages(zone),
2272 (zone->managed_pages + KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
2273 KSWAPD_ZONE_BALANCE_GAP_RATIO);
2274 watermark = high_wmark_pages(zone) + balance_gap + (2UL << sc->order);
2275 watermark_ok = zone_watermark_ok_safe(zone, 0, watermark, 0, 0);
2276
2277 /*
2278 * If compaction is deferred, reclaim up to a point where
2279 * compaction will have a chance of success when re-enabled
2280 */
2281 if (compaction_deferred(zone, sc->order))
2282 return watermark_ok;
2283
2284 /* If compaction is not ready to start, keep reclaiming */
2285 if (!compaction_suitable(zone, sc->order))
2286 return false;
2287
2288 return watermark_ok;
2289}
2290
2291/*
2292 * This is the direct reclaim path, for page-allocating processes. We only
2293 * try to reclaim pages from zones which will satisfy the caller's allocation
2294 * request.
2295 *
2296 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
2297 * Because:
2298 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
2299 * allocation or
2300 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
2301 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
2302 * zone defense algorithm.
2303 *
2304 * If a zone is deemed to be full of pinned pages then just give it a light
2305 * scan then give up on it.
2306 *
2307 * This function returns true if a zone is being reclaimed for a costly
2308 * high-order allocation and compaction is ready to begin. This indicates to
2309 * the caller that it should consider retrying the allocation instead of
2310 * further reclaim.
2311 */
2312static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
2313{
2314 struct zoneref *z;
2315 struct zone *zone;
2316 unsigned long nr_soft_reclaimed;
2317 unsigned long nr_soft_scanned;
2318 unsigned long lru_pages = 0;
2319 bool aborted_reclaim = false;
2320 struct reclaim_state *reclaim_state = current->reclaim_state;
2321 gfp_t orig_mask;
2322 struct shrink_control shrink = {
2323 .gfp_mask = sc->gfp_mask,
2324 };
2325 enum zone_type requested_highidx = gfp_zone(sc->gfp_mask);
2326
2327 /*
2328 * If the number of buffer_heads in the machine exceeds the maximum
2329 * allowed level, force direct reclaim to scan the highmem zone as
2330 * highmem pages could be pinning lowmem pages storing buffer_heads
2331 */
2332 orig_mask = sc->gfp_mask;
2333 if (buffer_heads_over_limit)
2334 sc->gfp_mask |= __GFP_HIGHMEM;
2335
2336 nodes_clear(shrink.nodes_to_scan);
2337
2338 for_each_zone_zonelist_nodemask(zone, z, zonelist,
2339 gfp_zone(sc->gfp_mask), sc->nodemask) {
2340 if (!populated_zone(zone))
2341 continue;
2342 /*
2343 * Take care memory controller reclaiming has small influence
2344 * to global LRU.
2345 */
2346 if (global_reclaim(sc)) {
2347 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2348 continue;
2349
2350 lru_pages += zone_reclaimable_pages(zone);
2351 node_set(zone_to_nid(zone), shrink.nodes_to_scan);
2352
2353 if (sc->priority != DEF_PRIORITY &&
2354 !zone_reclaimable(zone))
2355 continue; /* Let kswapd poll it */
2356 if (IS_ENABLED(CONFIG_COMPACTION)) {
2357 /*
2358 * If we already have plenty of memory free for
2359 * compaction in this zone, don't free any more.
2360 * Even though compaction is invoked for any
2361 * non-zero order, only frequent costly order
2362 * reclamation is disruptive enough to become a
2363 * noticeable problem, like transparent huge
2364 * page allocations.
2365 */
2366 if ((zonelist_zone_idx(z) <= requested_highidx)
2367 && compaction_ready(zone, sc)) {
2368 aborted_reclaim = true;
2369 continue;
2370 }
2371 }
2372 /*
2373 * This steals pages from memory cgroups over softlimit
2374 * and returns the number of reclaimed pages and
2375 * scanned pages. This works for global memory pressure
2376 * and balancing, not for a memcg's limit.
2377 */
2378 nr_soft_scanned = 0;
2379 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
2380 sc->order, sc->gfp_mask,
2381 &nr_soft_scanned);
2382 sc->nr_reclaimed += nr_soft_reclaimed;
2383 sc->nr_scanned += nr_soft_scanned;
2384 /* need some check for avoid more shrink_zone() */
2385 }
2386
2387 shrink_zone(zone, sc);
2388 }
2389
2390 /*
2391 * Don't shrink slabs when reclaiming memory from over limit cgroups
2392 * but do shrink slab at least once when aborting reclaim for
2393 * compaction to avoid unevenly scanning file/anon LRU pages over slab
2394 * pages.
2395 */
2396 if (global_reclaim(sc)) {
2397 shrink_slab(&shrink, sc->nr_scanned, lru_pages);
2398 if (reclaim_state) {
2399 sc->nr_reclaimed += reclaim_state->reclaimed_slab;
2400 reclaim_state->reclaimed_slab = 0;
2401 }
2402 }
2403
2404 /*
2405 * Restore to original mask to avoid the impact on the caller if we
2406 * promoted it to __GFP_HIGHMEM.
2407 */
2408 sc->gfp_mask = orig_mask;
2409
2410 return aborted_reclaim;
2411}
2412
2413/* All zones in zonelist are unreclaimable? */
2414static bool all_unreclaimable(struct zonelist *zonelist,
2415 struct scan_control *sc)
2416{
2417 struct zoneref *z;
2418 struct zone *zone;
2419
2420 for_each_zone_zonelist_nodemask(zone, z, zonelist,
2421 gfp_zone(sc->gfp_mask), sc->nodemask) {
2422 if (!populated_zone(zone))
2423 continue;
2424 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2425 continue;
2426 if (zone_reclaimable(zone))
2427 return false;
2428 }
2429
2430 return true;
2431}
2432
2433/*
2434 * This is the main entry point to direct page reclaim.
2435 *
2436 * If a full scan of the inactive list fails to free enough memory then we
2437 * are "out of memory" and something needs to be killed.
2438 *
2439 * If the caller is !__GFP_FS then the probability of a failure is reasonably
2440 * high - the zone may be full of dirty or under-writeback pages, which this
2441 * caller can't do much about. We kick the writeback threads and take explicit
2442 * naps in the hope that some of these pages can be written. But if the
2443 * allocating task holds filesystem locks which prevent writeout this might not
2444 * work, and the allocation attempt will fail.
2445 *
2446 * returns: 0, if no pages reclaimed
2447 * else, the number of pages reclaimed
2448 */
2449static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
2450 struct scan_control *sc)
2451{
2452 unsigned long total_scanned = 0;
2453 unsigned long writeback_threshold;
2454 bool aborted_reclaim;
2455
2456 delayacct_freepages_start();
2457
2458 if (global_reclaim(sc))
2459 count_vm_event(ALLOCSTALL);
2460
2461 do {
2462 vmpressure_prio(sc->gfp_mask, sc->target_mem_cgroup,
2463 sc->priority);
2464 sc->nr_scanned = 0;
2465 aborted_reclaim = shrink_zones(zonelist, sc);
2466
2467 total_scanned += sc->nr_scanned;
2468 if (sc->nr_reclaimed >= sc->nr_to_reclaim)
2469 goto out;
2470
2471 /*
2472 * If we're getting trouble reclaiming, start doing
2473 * writepage even in laptop mode.
2474 */
2475 if (sc->priority < DEF_PRIORITY - 2)
2476 sc->may_writepage = 1;
2477
2478 /*
2479 * Try to write back as many pages as we just scanned. This
2480 * tends to cause slow streaming writers to write data to the
2481 * disk smoothly, at the dirtying rate, which is nice. But
2482 * that's undesirable in laptop mode, where we *want* lumpy
2483 * writeout. So in laptop mode, write out the whole world.
2484 */
2485 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
2486 if (total_scanned > writeback_threshold) {
2487 wakeup_flusher_threads(laptop_mode ? 0 : total_scanned,
2488 WB_REASON_TRY_TO_FREE_PAGES);
2489 sc->may_writepage = 1;
2490 }
2491 } while (--sc->priority >= 0 && !aborted_reclaim);
2492
2493out:
2494 delayacct_freepages_end();
2495
2496 if (sc->nr_reclaimed)
2497 return sc->nr_reclaimed;
2498
2499 /*
2500 * As hibernation is going on, kswapd is freezed so that it can't mark
2501 * the zone into all_unreclaimable. Thus bypassing all_unreclaimable
2502 * check.
2503 */
2504 if (oom_killer_disabled)
2505 return 0;
2506
2507 /* Aborted reclaim to try compaction? don't OOM, then */
2508 if (aborted_reclaim)
2509 return 1;
2510
2511 /* top priority shrink_zones still had more to do? don't OOM, then */
2512 if (global_reclaim(sc) && !all_unreclaimable(zonelist, sc))
2513 return 1;
2514
2515 return 0;
2516}
2517
2518static bool pfmemalloc_watermark_ok(pg_data_t *pgdat)
2519{
2520 struct zone *zone;
2521 unsigned long pfmemalloc_reserve = 0;
2522 unsigned long free_pages = 0;
2523 int i;
2524 bool wmark_ok;
2525
2526 for (i = 0; i <= ZONE_NORMAL; i++) {
2527 zone = &pgdat->node_zones[i];
2528 pfmemalloc_reserve += min_wmark_pages(zone);
2529 free_pages += zone_page_state(zone, NR_FREE_PAGES);
2530 }
2531
2532 wmark_ok = free_pages > pfmemalloc_reserve / 2;
2533
2534 /* kswapd must be awake if processes are being throttled */
2535 if (!wmark_ok && waitqueue_active(&pgdat->kswapd_wait)) {
2536 pgdat->classzone_idx = min(pgdat->classzone_idx,
2537 (enum zone_type)ZONE_NORMAL);
2538 wake_up_interruptible(&pgdat->kswapd_wait);
2539 }
2540
2541 return wmark_ok;
2542}
2543
2544/*
2545 * Throttle direct reclaimers if backing storage is backed by the network
2546 * and the PFMEMALLOC reserve for the preferred node is getting dangerously
2547 * depleted. kswapd will continue to make progress and wake the processes
2548 * when the low watermark is reached.
2549 *
2550 * Returns true if a fatal signal was delivered during throttling. If this
2551 * happens, the page allocator should not consider triggering the OOM killer.
2552 */
2553static bool throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist *zonelist,
2554 nodemask_t *nodemask)
2555{
2556 struct zone *zone;
2557 int high_zoneidx = gfp_zone(gfp_mask);
2558 pg_data_t *pgdat;
2559
2560 /*
2561 * Kernel threads should not be throttled as they may be indirectly
2562 * responsible for cleaning pages necessary for reclaim to make forward
2563 * progress. kjournald for example may enter direct reclaim while
2564 * committing a transaction where throttling it could forcing other
2565 * processes to block on log_wait_commit().
2566 */
2567 if (current->flags & PF_KTHREAD)
2568 goto out;
2569
2570 /*
2571 * If a fatal signal is pending, this process should not throttle.
2572 * It should return quickly so it can exit and free its memory
2573 */
2574 if (fatal_signal_pending(current))
2575 goto out;
2576
2577 /* Check if the pfmemalloc reserves are ok */
2578 first_zones_zonelist(zonelist, high_zoneidx, NULL, &zone);
2579 pgdat = zone->zone_pgdat;
2580 if (pfmemalloc_watermark_ok(pgdat))
2581 goto out;
2582
2583 /* Account for the throttling */
2584 count_vm_event(PGSCAN_DIRECT_THROTTLE);
2585
2586 /*
2587 * If the caller cannot enter the filesystem, it's possible that it
2588 * is due to the caller holding an FS lock or performing a journal
2589 * transaction in the case of a filesystem like ext[3|4]. In this case,
2590 * it is not safe to block on pfmemalloc_wait as kswapd could be
2591 * blocked waiting on the same lock. Instead, throttle for up to a
2592 * second before continuing.
2593 */
2594 if (!(gfp_mask & __GFP_FS)) {
2595 wait_event_interruptible_timeout(pgdat->pfmemalloc_wait,
2596 pfmemalloc_watermark_ok(pgdat), HZ);
2597
2598 goto check_pending;
2599 }
2600
2601 /* Throttle until kswapd wakes the process */
2602 wait_event_killable(zone->zone_pgdat->pfmemalloc_wait,
2603 pfmemalloc_watermark_ok(pgdat));
2604
2605check_pending:
2606 if (fatal_signal_pending(current))
2607 return true;
2608
2609out:
2610 return false;
2611}
2612
2613unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
2614 gfp_t gfp_mask, nodemask_t *nodemask)
2615{
2616 unsigned long nr_reclaimed;
2617 struct scan_control sc = {
2618 .gfp_mask = (gfp_mask = memalloc_noio_flags(gfp_mask)),
2619 .may_writepage = !laptop_mode,
2620 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2621 .may_unmap = 1,
2622 .may_swap = 1,
2623 .order = order,
2624 .priority = DEF_PRIORITY,
2625 .target_mem_cgroup = NULL,
2626 .nodemask = nodemask,
2627 };
2628
2629 /*
2630 * Do not enter reclaim if fatal signal was delivered while throttled.
2631 * 1 is returned so that the page allocator does not OOM kill at this
2632 * point.
2633 */
2634 if (throttle_direct_reclaim(gfp_mask, zonelist, nodemask))
2635 return 1;
2636
2637 trace_mm_vmscan_direct_reclaim_begin(order,
2638 sc.may_writepage,
2639 gfp_mask);
2640
2641 nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
2642
2643 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
2644
2645 return nr_reclaimed;
2646}
2647
2648#ifdef CONFIG_MEMCG
2649
2650unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *memcg,
2651 gfp_t gfp_mask, bool noswap,
2652 struct zone *zone,
2653 unsigned long *nr_scanned)
2654{
2655 struct scan_control sc = {
2656 .nr_scanned = 0,
2657 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2658 .may_writepage = !laptop_mode,
2659 .may_unmap = 1,
2660 .may_swap = !noswap,
2661 .order = 0,
2662 .priority = 0,
2663 .target_mem_cgroup = memcg,
2664 };
2665 struct lruvec *lruvec = mem_cgroup_zone_lruvec(zone, memcg);
2666
2667 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2668 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
2669
2670 trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc.order,
2671 sc.may_writepage,
2672 sc.gfp_mask);
2673
2674 /*
2675 * NOTE: Although we can get the priority field, using it
2676 * here is not a good idea, since it limits the pages we can scan.
2677 * if we don't reclaim here, the shrink_zone from balance_pgdat
2678 * will pick up pages from other mem cgroup's as well. We hack
2679 * the priority and make it zero.
2680 */
2681 shrink_lruvec(lruvec, &sc);
2682
2683 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
2684
2685 *nr_scanned = sc.nr_scanned;
2686 return sc.nr_reclaimed;
2687}
2688
2689unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
2690 gfp_t gfp_mask,
2691 bool noswap)
2692{
2693 struct zonelist *zonelist;
2694 unsigned long nr_reclaimed;
2695 int nid;
2696 struct scan_control sc = {
2697 .may_writepage = !laptop_mode,
2698 .may_unmap = 1,
2699 .may_swap = !noswap,
2700 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2701 .order = 0,
2702 .priority = DEF_PRIORITY,
2703 .target_mem_cgroup = memcg,
2704 .nodemask = NULL, /* we don't care the placement */
2705 .gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2706 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
2707 };
2708
2709 /*
2710 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
2711 * take care of from where we get pages. So the node where we start the
2712 * scan does not need to be the current node.
2713 */
2714 nid = mem_cgroup_select_victim_node(memcg);
2715
2716 zonelist = NODE_DATA(nid)->node_zonelists;
2717
2718 trace_mm_vmscan_memcg_reclaim_begin(0,
2719 sc.may_writepage,
2720 sc.gfp_mask);
2721
2722 nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
2723
2724 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
2725
2726 return nr_reclaimed;
2727}
2728#endif
2729
2730static void age_active_anon(struct zone *zone, struct scan_control *sc)
2731{
2732 struct mem_cgroup *memcg;
2733
2734 if (!total_swap_pages)
2735 return;
2736
2737 memcg = mem_cgroup_iter(NULL, NULL, NULL);
2738 do {
2739 struct lruvec *lruvec = mem_cgroup_zone_lruvec(zone, memcg);
2740
2741 if (inactive_anon_is_low(lruvec))
2742 shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
2743 sc, LRU_ACTIVE_ANON);
2744
2745 memcg = mem_cgroup_iter(NULL, memcg, NULL);
2746 } while (memcg);
2747}
2748
2749static bool zone_balanced(struct zone *zone, int order,
2750 unsigned long balance_gap, int classzone_idx)
2751{
2752 if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone) +
2753 balance_gap, classzone_idx, 0))
2754 return false;
2755
2756 if (IS_ENABLED(CONFIG_COMPACTION) && order &&
2757 !compaction_suitable(zone, order))
2758 return false;
2759
2760 return true;
2761}
2762
2763/*
2764 * pgdat_balanced() is used when checking if a node is balanced.
2765 *
2766 * For order-0, all zones must be balanced!
2767 *
2768 * For high-order allocations only zones that meet watermarks and are in a
2769 * zone allowed by the callers classzone_idx are added to balanced_pages. The
2770 * total of balanced pages must be at least 25% of the zones allowed by
2771 * classzone_idx for the node to be considered balanced. Forcing all zones to
2772 * be balanced for high orders can cause excessive reclaim when there are
2773 * imbalanced zones.
2774 * The choice of 25% is due to
2775 * o a 16M DMA zone that is balanced will not balance a zone on any
2776 * reasonable sized machine
2777 * o On all other machines, the top zone must be at least a reasonable
2778 * percentage of the middle zones. For example, on 32-bit x86, highmem
2779 * would need to be at least 256M for it to be balance a whole node.
2780 * Similarly, on x86-64 the Normal zone would need to be at least 1G
2781 * to balance a node on its own. These seemed like reasonable ratios.
2782 */
2783static bool pgdat_balanced(pg_data_t *pgdat, int order, int classzone_idx)
2784{
2785 unsigned long managed_pages = 0;
2786 unsigned long balanced_pages = 0;
2787 int i;
2788
2789 /* Check the watermark levels */
2790 for (i = 0; i <= classzone_idx; i++) {
2791 struct zone *zone = pgdat->node_zones + i;
2792
2793 if (!populated_zone(zone))
2794 continue;
2795
2796 managed_pages += zone->managed_pages;
2797
2798 /*
2799 * A special case here:
2800 *
2801 * balance_pgdat() skips over all_unreclaimable after
2802 * DEF_PRIORITY. Effectively, it considers them balanced so
2803 * they must be considered balanced here as well!
2804 */
2805 if (!zone_reclaimable(zone)) {
2806 balanced_pages += zone->managed_pages;
2807 continue;
2808 }
2809
2810 if (zone_balanced(zone, order, 0, i))
2811 balanced_pages += zone->managed_pages;
2812 else if (!order)
2813 return false;
2814 }
2815
2816 if (order)
2817 return balanced_pages >= (managed_pages >> 2);
2818 else
2819 return true;
2820}
2821
2822/*
2823 * Prepare kswapd for sleeping. This verifies that there are no processes
2824 * waiting in throttle_direct_reclaim() and that watermarks have been met.
2825 *
2826 * Returns true if kswapd is ready to sleep
2827 */
2828static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, long remaining,
2829 int classzone_idx)
2830{
2831 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
2832 if (remaining)
2833 return false;
2834
2835 /*
2836 * There is a potential race between when kswapd checks its watermarks
2837 * and a process gets throttled. There is also a potential race if
2838 * processes get throttled, kswapd wakes, a large process exits therby
2839 * balancing the zones that causes kswapd to miss a wakeup. If kswapd
2840 * is going to sleep, no process should be sleeping on pfmemalloc_wait
2841 * so wake them now if necessary. If necessary, processes will wake
2842 * kswapd and get throttled again
2843 */
2844 if (waitqueue_active(&pgdat->pfmemalloc_wait)) {
2845 wake_up(&pgdat->pfmemalloc_wait);
2846 return false;
2847 }
2848
2849 return pgdat_balanced(pgdat, order, classzone_idx);
2850}
2851
2852/*
2853 * kswapd shrinks the zone by the number of pages required to reach
2854 * the high watermark.
2855 *
2856 * Returns true if kswapd scanned at least the requested number of pages to
2857 * reclaim or if the lack of progress was due to pages under writeback.
2858 * This is used to determine if the scanning priority needs to be raised.
2859 */
2860static bool kswapd_shrink_zone(struct zone *zone,
2861 int classzone_idx,
2862 struct scan_control *sc,
2863 unsigned long lru_pages,
2864 unsigned long *nr_attempted)
2865{
2866 int testorder = sc->order;
2867 unsigned long balance_gap;
2868 struct reclaim_state *reclaim_state = current->reclaim_state;
2869 struct shrink_control shrink = {
2870 .gfp_mask = sc->gfp_mask,
2871 };
2872 bool lowmem_pressure;
2873
2874 /* Reclaim above the high watermark. */
2875 sc->nr_to_reclaim = max(SWAP_CLUSTER_MAX, high_wmark_pages(zone));
2876
2877 /*
2878 * Kswapd reclaims only single pages with compaction enabled. Trying
2879 * too hard to reclaim until contiguous free pages have become
2880 * available can hurt performance by evicting too much useful data
2881 * from memory. Do not reclaim more than needed for compaction.
2882 */
2883 if (IS_ENABLED(CONFIG_COMPACTION) && sc->order &&
2884 compaction_suitable(zone, sc->order) !=
2885 COMPACT_SKIPPED)
2886 testorder = 0;
2887
2888 /*
2889 * We put equal pressure on every zone, unless one zone has way too
2890 * many pages free already. The "too many pages" is defined as the
2891 * high wmark plus a "gap" where the gap is either the low
2892 * watermark or 1% of the zone, whichever is smaller.
2893 */
2894 balance_gap = min(low_wmark_pages(zone),
2895 (zone->managed_pages + KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
2896 KSWAPD_ZONE_BALANCE_GAP_RATIO);
2897
2898 /*
2899 * If there is no low memory pressure or the zone is balanced then no
2900 * reclaim is necessary
2901 */
2902 lowmem_pressure = (buffer_heads_over_limit && is_highmem(zone));
2903 if (!lowmem_pressure && zone_balanced(zone, testorder,
2904 balance_gap, classzone_idx))
2905 return true;
2906
2907 shrink_zone(zone, sc);
2908 nodes_clear(shrink.nodes_to_scan);
2909 node_set(zone_to_nid(zone), shrink.nodes_to_scan);
2910
2911 reclaim_state->reclaimed_slab = 0;
2912 shrink_slab(&shrink, sc->nr_scanned, lru_pages);
2913 sc->nr_reclaimed += reclaim_state->reclaimed_slab;
2914
2915 /* Account for the number of pages attempted to reclaim */
2916 *nr_attempted += sc->nr_to_reclaim;
2917
2918 zone_clear_flag(zone, ZONE_WRITEBACK);
2919
2920 /*
2921 * If a zone reaches its high watermark, consider it to be no longer
2922 * congested. It's possible there are dirty pages backed by congested
2923 * BDIs but as pressure is relieved, speculatively avoid congestion
2924 * waits.
2925 */
2926 if (zone_reclaimable(zone) &&
2927 zone_balanced(zone, testorder, 0, classzone_idx)) {
2928 zone_clear_flag(zone, ZONE_CONGESTED);
2929 zone_clear_flag(zone, ZONE_TAIL_LRU_DIRTY);
2930 }
2931
2932 return sc->nr_scanned >= sc->nr_to_reclaim;
2933}
2934
2935/*
2936 * For kswapd, balance_pgdat() will work across all this node's zones until
2937 * they are all at high_wmark_pages(zone).
2938 *
2939 * Returns the final order kswapd was reclaiming at
2940 *
2941 * There is special handling here for zones which are full of pinned pages.
2942 * This can happen if the pages are all mlocked, or if they are all used by
2943 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
2944 * What we do is to detect the case where all pages in the zone have been
2945 * scanned twice and there has been zero successful reclaim. Mark the zone as
2946 * dead and from now on, only perform a short scan. Basically we're polling
2947 * the zone for when the problem goes away.
2948 *
2949 * kswapd scans the zones in the highmem->normal->dma direction. It skips
2950 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
2951 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
2952 * lower zones regardless of the number of free pages in the lower zones. This
2953 * interoperates with the page allocator fallback scheme to ensure that aging
2954 * of pages is balanced across the zones.
2955 */
2956static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
2957 int *classzone_idx)
2958{
2959 int i;
2960 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
2961 unsigned long nr_soft_reclaimed;
2962 unsigned long nr_soft_scanned;
2963 struct scan_control sc = {
2964 .gfp_mask = GFP_KERNEL,
2965 .priority = DEF_PRIORITY,
2966 .may_unmap = 1,
2967 .may_swap = 1,
2968 .may_writepage = !laptop_mode,
2969 .order = order,
2970 .target_mem_cgroup = NULL,
2971 };
2972 count_vm_event(PAGEOUTRUN);
2973
2974 do {
2975 unsigned long lru_pages = 0;
2976 unsigned long nr_attempted = 0;
2977 bool raise_priority = true;
2978 bool pgdat_needs_compaction = (order > 0);
2979
2980 sc.nr_reclaimed = 0;
2981
2982 /*
2983 * Scan in the highmem->dma direction for the highest
2984 * zone which needs scanning
2985 */
2986 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
2987 struct zone *zone = pgdat->node_zones + i;
2988
2989 if (!populated_zone(zone))
2990 continue;
2991
2992 if (sc.priority != DEF_PRIORITY &&
2993 !zone_reclaimable(zone))
2994 continue;
2995
2996 /*
2997 * Do some background aging of the anon list, to give
2998 * pages a chance to be referenced before reclaiming.
2999 */
3000 age_active_anon(zone, &sc);
3001
3002 /*
3003 * If the number of buffer_heads in the machine
3004 * exceeds the maximum allowed level and this node
3005 * has a highmem zone, force kswapd to reclaim from
3006 * it to relieve lowmem pressure.
3007 */
3008 if (buffer_heads_over_limit && is_highmem_idx(i)) {
3009 end_zone = i;
3010 break;
3011 }
3012
3013 if (!zone_balanced(zone, order, 0, 0)) {
3014 end_zone = i;
3015 break;
3016 } else {
3017 /*
3018 * If balanced, clear the dirty and congested
3019 * flags
3020 */
3021 zone_clear_flag(zone, ZONE_CONGESTED);
3022 zone_clear_flag(zone, ZONE_TAIL_LRU_DIRTY);
3023 }
3024 }
3025
3026 if (i < 0)
3027 goto out;
3028
3029 for (i = 0; i <= end_zone; i++) {
3030 struct zone *zone = pgdat->node_zones + i;
3031
3032 if (!populated_zone(zone))
3033 continue;
3034
3035 lru_pages += zone_reclaimable_pages(zone);
3036
3037 /*
3038 * If any zone is currently balanced then kswapd will
3039 * not call compaction as it is expected that the
3040 * necessary pages are already available.
3041 */
3042 if (pgdat_needs_compaction &&
3043 zone_watermark_ok(zone, order,
3044 low_wmark_pages(zone),
3045 *classzone_idx, 0))
3046 pgdat_needs_compaction = false;
3047 }
3048
3049 /*
3050 * If we're getting trouble reclaiming, start doing writepage
3051 * even in laptop mode.
3052 */
3053 if (sc.priority < DEF_PRIORITY - 2)
3054 sc.may_writepage = 1;
3055
3056 /*
3057 * Now scan the zone in the dma->highmem direction, stopping
3058 * at the last zone which needs scanning.
3059 *
3060 * We do this because the page allocator works in the opposite
3061 * direction. This prevents the page allocator from allocating
3062 * pages behind kswapd's direction of progress, which would
3063 * cause too much scanning of the lower zones.
3064 */
3065 for (i = 0; i <= end_zone; i++) {
3066 struct zone *zone = pgdat->node_zones + i;
3067
3068 if (!populated_zone(zone))
3069 continue;
3070
3071 if (sc.priority != DEF_PRIORITY &&
3072 !zone_reclaimable(zone))
3073 continue;
3074
3075 sc.nr_scanned = 0;
3076
3077 nr_soft_scanned = 0;
3078 /*
3079 * Call soft limit reclaim before calling shrink_zone.
3080 */
3081 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
3082 order, sc.gfp_mask,
3083 &nr_soft_scanned);
3084 sc.nr_reclaimed += nr_soft_reclaimed;
3085
3086 /*
3087 * There should be no need to raise the scanning
3088 * priority if enough pages are already being scanned
3089 * that that high watermark would be met at 100%
3090 * efficiency.
3091 */
3092 if (kswapd_shrink_zone(zone, end_zone, &sc,
3093 lru_pages, &nr_attempted))
3094 raise_priority = false;
3095 }
3096
3097 /*
3098 * If the low watermark is met there is no need for processes
3099 * to be throttled on pfmemalloc_wait as they should not be
3100 * able to safely make forward progress. Wake them
3101 */
3102 if (waitqueue_active(&pgdat->pfmemalloc_wait) &&
3103 pfmemalloc_watermark_ok(pgdat))
3104 wake_up(&pgdat->pfmemalloc_wait);
3105
3106 /*
3107 * Fragmentation may mean that the system cannot be rebalanced
3108 * for high-order allocations in all zones. If twice the
3109 * allocation size has been reclaimed and the zones are still
3110 * not balanced then recheck the watermarks at order-0 to
3111 * prevent kswapd reclaiming excessively. Assume that a
3112 * process requested a high-order can direct reclaim/compact.
3113 */
3114 if (order && sc.nr_reclaimed >= 2UL << order)
3115 order = sc.order = 0;
3116
3117 /* Check if kswapd should be suspending */
3118 if (try_to_freeze() || kthread_should_stop())
3119 break;
3120
3121 /*
3122 * Compact if necessary and kswapd is reclaiming at least the
3123 * high watermark number of pages as requsted
3124 */
3125 if (pgdat_needs_compaction && sc.nr_reclaimed > nr_attempted)
3126 compact_pgdat(pgdat, order);
3127
3128 /*
3129 * Raise priority if scanning rate is too low or there was no
3130 * progress in reclaiming pages
3131 */
3132 if (raise_priority || !sc.nr_reclaimed)
3133 sc.priority--;
3134 } while (sc.priority >= 1 &&
3135 !pgdat_balanced(pgdat, order, *classzone_idx));
3136
3137out:
3138 /*
3139 * Return the order we were reclaiming at so prepare_kswapd_sleep()
3140 * makes a decision on the order we were last reclaiming at. However,
3141 * if another caller entered the allocator slow path while kswapd
3142 * was awake, order will remain at the higher level
3143 */
3144 *classzone_idx = end_zone;
3145 return order;
3146}
3147
3148static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx)
3149{
3150 long remaining = 0;
3151 DEFINE_WAIT(wait);
3152
3153 if (freezing(current) || kthread_should_stop())
3154 return;
3155
3156 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
3157
3158 /* Try to sleep for a short interval */
3159 if (prepare_kswapd_sleep(pgdat, order, remaining, classzone_idx)) {
3160 remaining = schedule_timeout(HZ/10);
3161 finish_wait(&pgdat->kswapd_wait, &wait);
3162 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
3163 }
3164
3165 /*
3166 * After a short sleep, check if it was a premature sleep. If not, then
3167 * go fully to sleep until explicitly woken up.
3168 */
3169 if (prepare_kswapd_sleep(pgdat, order, remaining, classzone_idx)) {
3170 trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
3171
3172 /*
3173 * vmstat counters are not perfectly accurate and the estimated
3174 * value for counters such as NR_FREE_PAGES can deviate from the
3175 * true value by nr_online_cpus * threshold. To avoid the zone
3176 * watermarks being breached while under pressure, we reduce the
3177 * per-cpu vmstat threshold while kswapd is awake and restore
3178 * them before going back to sleep.
3179 */
3180 set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold);
3181
3182 /*
3183 * Compaction records what page blocks it recently failed to
3184 * isolate pages from and skips them in the future scanning.
3185 * When kswapd is going to sleep, it is reasonable to assume
3186 * that pages and compaction may succeed so reset the cache.
3187 */
3188 reset_isolation_suitable(pgdat);
3189
3190 if (!kthread_should_stop())
3191 schedule();
3192
3193 set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold);
3194 } else {
3195 if (remaining)
3196 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
3197 else
3198 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
3199 }
3200 finish_wait(&pgdat->kswapd_wait, &wait);
3201}
3202
3203/*
3204 * The background pageout daemon, started as a kernel thread
3205 * from the init process.
3206 *
3207 * This basically trickles out pages so that we have _some_
3208 * free memory available even if there is no other activity
3209 * that frees anything up. This is needed for things like routing
3210 * etc, where we otherwise might have all activity going on in
3211 * asynchronous contexts that cannot page things out.
3212 *
3213 * If there are applications that are active memory-allocators
3214 * (most normal use), this basically shouldn't matter.
3215 */
3216static int kswapd(void *p)
3217{
3218 unsigned long order, new_order;
3219 unsigned balanced_order;
3220 int classzone_idx, new_classzone_idx;
3221 int balanced_classzone_idx;
3222 pg_data_t *pgdat = (pg_data_t*)p;
3223 struct task_struct *tsk = current;
3224
3225 struct reclaim_state reclaim_state = {
3226 .reclaimed_slab = 0,
3227 };
3228 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
3229
3230 lockdep_set_current_reclaim_state(GFP_KERNEL);
3231
3232 if (!cpumask_empty(cpumask))
3233 set_cpus_allowed_ptr(tsk, cpumask);
3234 current->reclaim_state = &reclaim_state;
3235
3236 /*
3237 * Tell the memory management that we're a "memory allocator",
3238 * and that if we need more memory we should get access to it
3239 * regardless (see "__alloc_pages()"). "kswapd" should
3240 * never get caught in the normal page freeing logic.
3241 *
3242 * (Kswapd normally doesn't need memory anyway, but sometimes
3243 * you need a small amount of memory in order to be able to
3244 * page out something else, and this flag essentially protects
3245 * us from recursively trying to free more memory as we're
3246 * trying to free the first piece of memory in the first place).
3247 */
3248 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
3249 set_freezable();
3250
3251 order = new_order = 0;
3252 balanced_order = 0;
3253 classzone_idx = new_classzone_idx = pgdat->nr_zones - 1;
3254 balanced_classzone_idx = classzone_idx;
3255 for ( ; ; ) {
3256 bool ret;
3257
3258 /*
3259 * If the last balance_pgdat was unsuccessful it's unlikely a
3260 * new request of a similar or harder type will succeed soon
3261 * so consider going to sleep on the basis we reclaimed at
3262 */
3263 if (balanced_classzone_idx >= new_classzone_idx &&
3264 balanced_order == new_order) {
3265 new_order = pgdat->kswapd_max_order;
3266 new_classzone_idx = pgdat->classzone_idx;
3267 pgdat->kswapd_max_order = 0;
3268 pgdat->classzone_idx = pgdat->nr_zones - 1;
3269 }
3270
3271 if (order < new_order || classzone_idx > new_classzone_idx) {
3272 /*
3273 * Don't sleep if someone wants a larger 'order'
3274 * allocation or has tigher zone constraints
3275 */
3276 order = new_order;
3277 classzone_idx = new_classzone_idx;
3278 } else {
3279 kswapd_try_to_sleep(pgdat, balanced_order,
3280 balanced_classzone_idx);
3281 order = pgdat->kswapd_max_order;
3282 classzone_idx = pgdat->classzone_idx;
3283 new_order = order;
3284 new_classzone_idx = classzone_idx;
3285 pgdat->kswapd_max_order = 0;
3286 pgdat->classzone_idx = pgdat->nr_zones - 1;
3287 }
3288
3289 ret = try_to_freeze();
3290 if (kthread_should_stop())
3291 break;
3292
3293 /*
3294 * We can speed up thawing tasks if we don't call balance_pgdat
3295 * after returning from the refrigerator
3296 */
3297 if (!ret) {
3298 trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
3299 balanced_classzone_idx = classzone_idx;
3300 balanced_order = balance_pgdat(pgdat, order,
3301 &balanced_classzone_idx);
3302 }
3303 }
3304
3305 current->reclaim_state = NULL;
3306 return 0;
3307}
3308
3309/*
3310 * A zone is low on free memory, so wake its kswapd task to service it.
3311 */
3312void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
3313{
3314 pg_data_t *pgdat;
3315
3316 if (!populated_zone(zone))
3317 return;
3318
3319 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
3320 return;
3321 pgdat = zone->zone_pgdat;
3322 if (pgdat->kswapd_max_order < order) {
3323 pgdat->kswapd_max_order = order;
3324 pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx);
3325 }
3326 if (!waitqueue_active(&pgdat->kswapd_wait))
3327 return;
3328 if (zone_balanced(zone, order, 0, 0))
3329 return;
3330
3331 trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);
3332 wake_up_interruptible(&pgdat->kswapd_wait);
3333}
3334
3335#ifdef CONFIG_HIBERNATION
3336/*
3337 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
3338 * freed pages.
3339 *
3340 * Rather than trying to age LRUs the aim is to preserve the overall
3341 * LRU order by reclaiming preferentially
3342 * inactive > active > active referenced > active mapped
3343 */
3344unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
3345{
3346 struct reclaim_state reclaim_state;
3347 struct scan_control sc = {
3348 .gfp_mask = GFP_HIGHUSER_MOVABLE,
3349 .may_swap = 1,
3350 .may_unmap = 1,
3351 .may_writepage = 1,
3352 .nr_to_reclaim = nr_to_reclaim,
3353 .hibernation_mode = 1,
3354 .order = 0,
3355 .priority = DEF_PRIORITY,
3356 };
3357 struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
3358 struct task_struct *p = current;
3359 unsigned long nr_reclaimed;
3360
3361 p->flags |= PF_MEMALLOC;
3362 lockdep_set_current_reclaim_state(sc.gfp_mask);
3363 reclaim_state.reclaimed_slab = 0;
3364 p->reclaim_state = &reclaim_state;
3365
3366 nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
3367
3368 p->reclaim_state = NULL;
3369 lockdep_clear_current_reclaim_state();
3370 p->flags &= ~PF_MEMALLOC;
3371
3372 return nr_reclaimed;
3373}
3374#endif /* CONFIG_HIBERNATION */
3375
3376/* It's optimal to keep kswapds on the same CPUs as their memory, but
3377 not required for correctness. So if the last cpu in a node goes
3378 away, we get changed to run anywhere: as the first one comes back,
3379 restore their cpu bindings. */
3380static int cpu_callback(struct notifier_block *nfb, unsigned long action,
3381 void *hcpu)
3382{
3383 int nid;
3384
3385 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
3386 for_each_node_state(nid, N_MEMORY) {
3387 pg_data_t *pgdat = NODE_DATA(nid);
3388 const struct cpumask *mask;
3389
3390 mask = cpumask_of_node(pgdat->node_id);
3391
3392 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
3393 /* One of our CPUs online: restore mask */
3394 set_cpus_allowed_ptr(pgdat->kswapd, mask);
3395 }
3396 }
3397 return NOTIFY_OK;
3398}
3399
3400/*
3401 * This kswapd start function will be called by init and node-hot-add.
3402 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
3403 */
3404int kswapd_run(int nid)
3405{
3406 pg_data_t *pgdat = NODE_DATA(nid);
3407 int ret = 0;
3408
3409 if (pgdat->kswapd)
3410 return 0;
3411
3412 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
3413 if (IS_ERR(pgdat->kswapd)) {
3414 /* failure at boot is fatal */
3415 BUG_ON(system_state == SYSTEM_BOOTING);
3416 pr_err("Failed to start kswapd on node %d\n", nid);
3417 ret = PTR_ERR(pgdat->kswapd);
3418 pgdat->kswapd = NULL;
3419 }
3420 return ret;
3421}
3422
3423/*
3424 * Called by memory hotplug when all memory in a node is offlined. Caller must
3425 * hold lock_memory_hotplug().
3426 */
3427void kswapd_stop(int nid)
3428{
3429 struct task_struct *kswapd = NODE_DATA(nid)->kswapd;
3430
3431 if (kswapd) {
3432 kthread_stop(kswapd);
3433 NODE_DATA(nid)->kswapd = NULL;
3434 }
3435}
3436
3437static int __init kswapd_init(void)
3438{
3439 int nid;
3440
3441 swap_setup();
3442 for_each_node_state(nid, N_MEMORY)
3443 kswapd_run(nid);
3444 hotcpu_notifier(cpu_callback, 0);
3445 return 0;
3446}
3447
3448module_init(kswapd_init)
3449
3450#ifdef CONFIG_NUMA
3451/*
3452 * Zone reclaim mode
3453 *
3454 * If non-zero call zone_reclaim when the number of free pages falls below
3455 * the watermarks.
3456 */
3457int zone_reclaim_mode __read_mostly;
3458
3459#define RECLAIM_OFF 0
3460#define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
3461#define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
3462#define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
3463
3464/*
3465 * Priority for ZONE_RECLAIM. This determines the fraction of pages
3466 * of a node considered for each zone_reclaim. 4 scans 1/16th of
3467 * a zone.
3468 */
3469#define ZONE_RECLAIM_PRIORITY 4
3470
3471/*
3472 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
3473 * occur.
3474 */
3475int sysctl_min_unmapped_ratio = 1;
3476
3477/*
3478 * If the number of slab pages in a zone grows beyond this percentage then
3479 * slab reclaim needs to occur.
3480 */
3481int sysctl_min_slab_ratio = 5;
3482
3483static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
3484{
3485 unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
3486 unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
3487 zone_page_state(zone, NR_ACTIVE_FILE);
3488
3489 /*
3490 * It's possible for there to be more file mapped pages than
3491 * accounted for by the pages on the file LRU lists because
3492 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
3493 */
3494 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
3495}
3496
3497/* Work out how many page cache pages we can reclaim in this reclaim_mode */
3498static long zone_pagecache_reclaimable(struct zone *zone)
3499{
3500 long nr_pagecache_reclaimable;
3501 long delta = 0;
3502
3503 /*
3504 * If RECLAIM_SWAP is set, then all file pages are considered
3505 * potentially reclaimable. Otherwise, we have to worry about
3506 * pages like swapcache and zone_unmapped_file_pages() provides
3507 * a better estimate
3508 */
3509 if (zone_reclaim_mode & RECLAIM_SWAP)
3510 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
3511 else
3512 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
3513
3514 /* If we can't clean pages, remove dirty pages from consideration */
3515 if (!(zone_reclaim_mode & RECLAIM_WRITE))
3516 delta += zone_page_state(zone, NR_FILE_DIRTY);
3517
3518 /* Watch for any possible underflows due to delta */
3519 if (unlikely(delta > nr_pagecache_reclaimable))
3520 delta = nr_pagecache_reclaimable;
3521
3522 return nr_pagecache_reclaimable - delta;
3523}
3524
3525/*
3526 * Try to free up some pages from this zone through reclaim.
3527 */
3528static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
3529{
3530 /* Minimum pages needed in order to stay on node */
3531 const unsigned long nr_pages = 1 << order;
3532 struct task_struct *p = current;
3533 struct reclaim_state reclaim_state;
3534 struct scan_control sc = {
3535 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
3536 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
3537 .may_swap = 1,
3538 .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
3539 .gfp_mask = (gfp_mask = memalloc_noio_flags(gfp_mask)),
3540 .order = order,
3541 .priority = ZONE_RECLAIM_PRIORITY,
3542 };
3543 struct shrink_control shrink = {
3544 .gfp_mask = sc.gfp_mask,
3545 };
3546 unsigned long nr_slab_pages0, nr_slab_pages1;
3547
3548 cond_resched();
3549 /*
3550 * We need to be able to allocate from the reserves for RECLAIM_SWAP
3551 * and we also need to be able to write out pages for RECLAIM_WRITE
3552 * and RECLAIM_SWAP.
3553 */
3554 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
3555 lockdep_set_current_reclaim_state(gfp_mask);
3556 reclaim_state.reclaimed_slab = 0;
3557 p->reclaim_state = &reclaim_state;
3558
3559 if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
3560 /*
3561 * Free memory by calling shrink zone with increasing
3562 * priorities until we have enough memory freed.
3563 */
3564 do {
3565 shrink_zone(zone, &sc);
3566 } while (sc.nr_reclaimed < nr_pages && --sc.priority >= 0);
3567 }
3568
3569 nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
3570 if (nr_slab_pages0 > zone->min_slab_pages) {
3571 /*
3572 * shrink_slab() does not currently allow us to determine how
3573 * many pages were freed in this zone. So we take the current
3574 * number of slab pages and shake the slab until it is reduced
3575 * by the same nr_pages that we used for reclaiming unmapped
3576 * pages.
3577 */
3578 nodes_clear(shrink.nodes_to_scan);
3579 node_set(zone_to_nid(zone), shrink.nodes_to_scan);
3580 for (;;) {
3581 unsigned long lru_pages = zone_reclaimable_pages(zone);
3582
3583 /* No reclaimable slab or very low memory pressure */
3584 if (!shrink_slab(&shrink, sc.nr_scanned, lru_pages))
3585 break;
3586
3587 /* Freed enough memory */
3588 nr_slab_pages1 = zone_page_state(zone,
3589 NR_SLAB_RECLAIMABLE);
3590 if (nr_slab_pages1 + nr_pages <= nr_slab_pages0)
3591 break;
3592 }
3593
3594 /*
3595 * Update nr_reclaimed by the number of slab pages we
3596 * reclaimed from this zone.
3597 */
3598 nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
3599 if (nr_slab_pages1 < nr_slab_pages0)
3600 sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1;
3601 }
3602
3603 p->reclaim_state = NULL;
3604 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
3605 lockdep_clear_current_reclaim_state();
3606 return sc.nr_reclaimed >= nr_pages;
3607}
3608
3609int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
3610{
3611 int node_id;
3612 int ret;
3613
3614 /*
3615 * Zone reclaim reclaims unmapped file backed pages and
3616 * slab pages if we are over the defined limits.
3617 *
3618 * A small portion of unmapped file backed pages is needed for
3619 * file I/O otherwise pages read by file I/O will be immediately
3620 * thrown out if the zone is overallocated. So we do not reclaim
3621 * if less than a specified percentage of the zone is used by
3622 * unmapped file backed pages.
3623 */
3624 if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
3625 zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
3626 return ZONE_RECLAIM_FULL;
3627
3628 if (!zone_reclaimable(zone))
3629 return ZONE_RECLAIM_FULL;
3630
3631 /*
3632 * Do not scan if the allocation should not be delayed.
3633 */
3634 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
3635 return ZONE_RECLAIM_NOSCAN;
3636
3637 /*
3638 * Only run zone reclaim on the local zone or on zones that do not
3639 * have associated processors. This will favor the local processor
3640 * over remote processors and spread off node memory allocations
3641 * as wide as possible.
3642 */
3643 node_id = zone_to_nid(zone);
3644 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
3645 return ZONE_RECLAIM_NOSCAN;
3646
3647 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
3648 return ZONE_RECLAIM_NOSCAN;
3649
3650 ret = __zone_reclaim(zone, gfp_mask, order);
3651 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
3652
3653 if (!ret)
3654 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
3655
3656 return ret;
3657}
3658#endif
3659
3660/*
3661 * page_evictable - test whether a page is evictable
3662 * @page: the page to test
3663 *
3664 * Test whether page is evictable--i.e., should be placed on active/inactive
3665 * lists vs unevictable list.
3666 *
3667 * Reasons page might not be evictable:
3668 * (1) page's mapping marked unevictable
3669 * (2) page is part of an mlocked VMA
3670 *
3671 */
3672int page_evictable(struct page *page)
3673{
3674 return !mapping_unevictable(page_mapping(page)) && !PageMlocked(page);
3675}
3676
3677#ifdef CONFIG_SHMEM
3678/**
3679 * check_move_unevictable_pages - check pages for evictability and move to appropriate zone lru list
3680 * @pages: array of pages to check
3681 * @nr_pages: number of pages to check
3682 *
3683 * Checks pages for evictability and moves them to the appropriate lru list.
3684 *
3685 * This function is only used for SysV IPC SHM_UNLOCK.
3686 */
3687void check_move_unevictable_pages(struct page **pages, int nr_pages)
3688{
3689 struct lruvec *lruvec;
3690 struct zone *zone = NULL;
3691 int pgscanned = 0;
3692 int pgrescued = 0;
3693 int i;
3694
3695 for (i = 0; i < nr_pages; i++) {
3696 struct page *page = pages[i];
3697 struct zone *pagezone;
3698
3699 pgscanned++;
3700 pagezone = page_zone(page);
3701 if (pagezone != zone) {
3702 if (zone)
3703 spin_unlock_irq(&zone->lru_lock);
3704 zone = pagezone;
3705 spin_lock_irq(&zone->lru_lock);
3706 }
3707 lruvec = mem_cgroup_page_lruvec(page, zone);
3708
3709 if (!PageLRU(page) || !PageUnevictable(page))
3710 continue;
3711
3712 if (page_evictable(page)) {
3713 enum lru_list lru = page_lru_base_type(page);
3714
3715 VM_BUG_ON_PAGE(PageActive(page), page);
3716 ClearPageUnevictable(page);
3717 del_page_from_lru_list(page, lruvec, LRU_UNEVICTABLE);
3718 add_page_to_lru_list(page, lruvec, lru);
3719 pgrescued++;
3720 }
3721 }
3722
3723 if (zone) {
3724 __count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
3725 __count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned);
3726 spin_unlock_irq(&zone->lru_lock);
3727 }
3728}
3729#endif /* CONFIG_SHMEM */
3730
3731static void warn_scan_unevictable_pages(void)
3732{
3733 printk_once(KERN_WARNING
3734 "%s: The scan_unevictable_pages sysctl/node-interface has been "
3735 "disabled for lack of a legitimate use case. If you have "
3736 "one, please send an email to linux-mm@kvack.org.\n",
3737 current->comm);
3738}
3739
3740/*
3741 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
3742 * all nodes' unevictable lists for evictable pages
3743 */
3744unsigned long scan_unevictable_pages;
3745
3746int scan_unevictable_handler(struct ctl_table *table, int write,
3747 void __user *buffer,
3748 size_t *length, loff_t *ppos)
3749{
3750 warn_scan_unevictable_pages();
3751 proc_doulongvec_minmax(table, write, buffer, length, ppos);
3752 scan_unevictable_pages = 0;
3753 return 0;
3754}
3755
3756#ifdef CONFIG_NUMA
3757/*
3758 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
3759 * a specified node's per zone unevictable lists for evictable pages.
3760 */
3761
3762static ssize_t read_scan_unevictable_node(struct device *dev,
3763 struct device_attribute *attr,
3764 char *buf)
3765{
3766 warn_scan_unevictable_pages();
3767 return sprintf(buf, "0\n"); /* always zero; should fit... */
3768}
3769
3770static ssize_t write_scan_unevictable_node(struct device *dev,
3771 struct device_attribute *attr,
3772 const char *buf, size_t count)
3773{
3774 warn_scan_unevictable_pages();
3775 return 1;
3776}
3777
3778
3779static DEVICE_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
3780 read_scan_unevictable_node,
3781 write_scan_unevictable_node);
3782
3783int scan_unevictable_register_node(struct node *node)
3784{
3785 return device_create_file(&node->dev, &dev_attr_scan_unevictable_pages);
3786}
3787
3788void scan_unevictable_unregister_node(struct node *node)
3789{
3790 device_remove_file(&node->dev, &dev_attr_scan_unevictable_pages);
3791}
3792#endif