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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * linux/mm/swap.c
4 *
5 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
6 */
7
8/*
9 * This file contains the default values for the operation of the
10 * Linux VM subsystem. Fine-tuning documentation can be found in
11 * Documentation/admin-guide/sysctl/vm.rst.
12 * Started 18.12.91
13 * Swap aging added 23.2.95, Stephen Tweedie.
14 * Buffermem limits added 12.3.98, Rik van Riel.
15 */
16
17#include <linux/mm.h>
18#include <linux/sched.h>
19#include <linux/kernel_stat.h>
20#include <linux/swap.h>
21#include <linux/mman.h>
22#include <linux/pagemap.h>
23#include <linux/pagevec.h>
24#include <linux/init.h>
25#include <linux/export.h>
26#include <linux/mm_inline.h>
27#include <linux/percpu_counter.h>
28#include <linux/memremap.h>
29#include <linux/percpu.h>
30#include <linux/cpu.h>
31#include <linux/notifier.h>
32#include <linux/backing-dev.h>
33#include <linux/memcontrol.h>
34#include <linux/gfp.h>
35#include <linux/uio.h>
36#include <linux/hugetlb.h>
37#include <linux/page_idle.h>
38
39#include "internal.h"
40
41#define CREATE_TRACE_POINTS
42#include <trace/events/pagemap.h>
43
44/* How many pages do we try to swap or page in/out together? */
45int page_cluster;
46
47static DEFINE_PER_CPU(struct pagevec, lru_add_pvec);
48static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs);
49static DEFINE_PER_CPU(struct pagevec, lru_deactivate_file_pvecs);
50static DEFINE_PER_CPU(struct pagevec, lru_deactivate_pvecs);
51static DEFINE_PER_CPU(struct pagevec, lru_lazyfree_pvecs);
52#ifdef CONFIG_SMP
53static DEFINE_PER_CPU(struct pagevec, activate_page_pvecs);
54#endif
55
56/*
57 * This path almost never happens for VM activity - pages are normally
58 * freed via pagevecs. But it gets used by networking.
59 */
60static void __page_cache_release(struct page *page)
61{
62 if (PageLRU(page)) {
63 pg_data_t *pgdat = page_pgdat(page);
64 struct lruvec *lruvec;
65 unsigned long flags;
66
67 spin_lock_irqsave(&pgdat->lru_lock, flags);
68 lruvec = mem_cgroup_page_lruvec(page, pgdat);
69 VM_BUG_ON_PAGE(!PageLRU(page), page);
70 __ClearPageLRU(page);
71 del_page_from_lru_list(page, lruvec, page_off_lru(page));
72 spin_unlock_irqrestore(&pgdat->lru_lock, flags);
73 }
74 __ClearPageWaiters(page);
75}
76
77static void __put_single_page(struct page *page)
78{
79 __page_cache_release(page);
80 mem_cgroup_uncharge(page);
81 free_unref_page(page);
82}
83
84static void __put_compound_page(struct page *page)
85{
86 compound_page_dtor *dtor;
87
88 /*
89 * __page_cache_release() is supposed to be called for thp, not for
90 * hugetlb. This is because hugetlb page does never have PageLRU set
91 * (it's never listed to any LRU lists) and no memcg routines should
92 * be called for hugetlb (it has a separate hugetlb_cgroup.)
93 */
94 if (!PageHuge(page))
95 __page_cache_release(page);
96 dtor = get_compound_page_dtor(page);
97 (*dtor)(page);
98}
99
100void __put_page(struct page *page)
101{
102 if (is_zone_device_page(page)) {
103 put_dev_pagemap(page->pgmap);
104
105 /*
106 * The page belongs to the device that created pgmap. Do
107 * not return it to page allocator.
108 */
109 return;
110 }
111
112 if (unlikely(PageCompound(page)))
113 __put_compound_page(page);
114 else
115 __put_single_page(page);
116}
117EXPORT_SYMBOL(__put_page);
118
119/**
120 * put_pages_list() - release a list of pages
121 * @pages: list of pages threaded on page->lru
122 *
123 * Release a list of pages which are strung together on page.lru. Currently
124 * used by read_cache_pages() and related error recovery code.
125 */
126void put_pages_list(struct list_head *pages)
127{
128 while (!list_empty(pages)) {
129 struct page *victim;
130
131 victim = lru_to_page(pages);
132 list_del(&victim->lru);
133 put_page(victim);
134 }
135}
136EXPORT_SYMBOL(put_pages_list);
137
138/*
139 * get_kernel_pages() - pin kernel pages in memory
140 * @kiov: An array of struct kvec structures
141 * @nr_segs: number of segments to pin
142 * @write: pinning for read/write, currently ignored
143 * @pages: array that receives pointers to the pages pinned.
144 * Should be at least nr_segs long.
145 *
146 * Returns number of pages pinned. This may be fewer than the number
147 * requested. If nr_pages is 0 or negative, returns 0. If no pages
148 * were pinned, returns -errno. Each page returned must be released
149 * with a put_page() call when it is finished with.
150 */
151int get_kernel_pages(const struct kvec *kiov, int nr_segs, int write,
152 struct page **pages)
153{
154 int seg;
155
156 for (seg = 0; seg < nr_segs; seg++) {
157 if (WARN_ON(kiov[seg].iov_len != PAGE_SIZE))
158 return seg;
159
160 pages[seg] = kmap_to_page(kiov[seg].iov_base);
161 get_page(pages[seg]);
162 }
163
164 return seg;
165}
166EXPORT_SYMBOL_GPL(get_kernel_pages);
167
168/*
169 * get_kernel_page() - pin a kernel page in memory
170 * @start: starting kernel address
171 * @write: pinning for read/write, currently ignored
172 * @pages: array that receives pointer to the page pinned.
173 * Must be at least nr_segs long.
174 *
175 * Returns 1 if page is pinned. If the page was not pinned, returns
176 * -errno. The page returned must be released with a put_page() call
177 * when it is finished with.
178 */
179int get_kernel_page(unsigned long start, int write, struct page **pages)
180{
181 const struct kvec kiov = {
182 .iov_base = (void *)start,
183 .iov_len = PAGE_SIZE
184 };
185
186 return get_kernel_pages(&kiov, 1, write, pages);
187}
188EXPORT_SYMBOL_GPL(get_kernel_page);
189
190static void pagevec_lru_move_fn(struct pagevec *pvec,
191 void (*move_fn)(struct page *page, struct lruvec *lruvec, void *arg),
192 void *arg)
193{
194 int i;
195 struct pglist_data *pgdat = NULL;
196 struct lruvec *lruvec;
197 unsigned long flags = 0;
198
199 for (i = 0; i < pagevec_count(pvec); i++) {
200 struct page *page = pvec->pages[i];
201 struct pglist_data *pagepgdat = page_pgdat(page);
202
203 if (pagepgdat != pgdat) {
204 if (pgdat)
205 spin_unlock_irqrestore(&pgdat->lru_lock, flags);
206 pgdat = pagepgdat;
207 spin_lock_irqsave(&pgdat->lru_lock, flags);
208 }
209
210 lruvec = mem_cgroup_page_lruvec(page, pgdat);
211 (*move_fn)(page, lruvec, arg);
212 }
213 if (pgdat)
214 spin_unlock_irqrestore(&pgdat->lru_lock, flags);
215 release_pages(pvec->pages, pvec->nr);
216 pagevec_reinit(pvec);
217}
218
219static void pagevec_move_tail_fn(struct page *page, struct lruvec *lruvec,
220 void *arg)
221{
222 int *pgmoved = arg;
223
224 if (PageLRU(page) && !PageUnevictable(page)) {
225 del_page_from_lru_list(page, lruvec, page_lru(page));
226 ClearPageActive(page);
227 add_page_to_lru_list_tail(page, lruvec, page_lru(page));
228 (*pgmoved)++;
229 }
230}
231
232/*
233 * pagevec_move_tail() must be called with IRQ disabled.
234 * Otherwise this may cause nasty races.
235 */
236static void pagevec_move_tail(struct pagevec *pvec)
237{
238 int pgmoved = 0;
239
240 pagevec_lru_move_fn(pvec, pagevec_move_tail_fn, &pgmoved);
241 __count_vm_events(PGROTATED, pgmoved);
242}
243
244/*
245 * Writeback is about to end against a page which has been marked for immediate
246 * reclaim. If it still appears to be reclaimable, move it to the tail of the
247 * inactive list.
248 */
249void rotate_reclaimable_page(struct page *page)
250{
251 if (!PageLocked(page) && !PageDirty(page) &&
252 !PageUnevictable(page) && PageLRU(page)) {
253 struct pagevec *pvec;
254 unsigned long flags;
255
256 get_page(page);
257 local_irq_save(flags);
258 pvec = this_cpu_ptr(&lru_rotate_pvecs);
259 if (!pagevec_add(pvec, page) || PageCompound(page))
260 pagevec_move_tail(pvec);
261 local_irq_restore(flags);
262 }
263}
264
265static void update_page_reclaim_stat(struct lruvec *lruvec,
266 int file, int rotated)
267{
268 struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
269
270 reclaim_stat->recent_scanned[file]++;
271 if (rotated)
272 reclaim_stat->recent_rotated[file]++;
273}
274
275static void __activate_page(struct page *page, struct lruvec *lruvec,
276 void *arg)
277{
278 if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
279 int file = page_is_file_cache(page);
280 int lru = page_lru_base_type(page);
281
282 del_page_from_lru_list(page, lruvec, lru);
283 SetPageActive(page);
284 lru += LRU_ACTIVE;
285 add_page_to_lru_list(page, lruvec, lru);
286 trace_mm_lru_activate(page);
287
288 __count_vm_event(PGACTIVATE);
289 update_page_reclaim_stat(lruvec, file, 1);
290 }
291}
292
293#ifdef CONFIG_SMP
294static void activate_page_drain(int cpu)
295{
296 struct pagevec *pvec = &per_cpu(activate_page_pvecs, cpu);
297
298 if (pagevec_count(pvec))
299 pagevec_lru_move_fn(pvec, __activate_page, NULL);
300}
301
302static bool need_activate_page_drain(int cpu)
303{
304 return pagevec_count(&per_cpu(activate_page_pvecs, cpu)) != 0;
305}
306
307void activate_page(struct page *page)
308{
309 page = compound_head(page);
310 if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
311 struct pagevec *pvec = &get_cpu_var(activate_page_pvecs);
312
313 get_page(page);
314 if (!pagevec_add(pvec, page) || PageCompound(page))
315 pagevec_lru_move_fn(pvec, __activate_page, NULL);
316 put_cpu_var(activate_page_pvecs);
317 }
318}
319
320#else
321static inline void activate_page_drain(int cpu)
322{
323}
324
325void activate_page(struct page *page)
326{
327 pg_data_t *pgdat = page_pgdat(page);
328
329 page = compound_head(page);
330 spin_lock_irq(&pgdat->lru_lock);
331 __activate_page(page, mem_cgroup_page_lruvec(page, pgdat), NULL);
332 spin_unlock_irq(&pgdat->lru_lock);
333}
334#endif
335
336static void __lru_cache_activate_page(struct page *page)
337{
338 struct pagevec *pvec = &get_cpu_var(lru_add_pvec);
339 int i;
340
341 /*
342 * Search backwards on the optimistic assumption that the page being
343 * activated has just been added to this pagevec. Note that only
344 * the local pagevec is examined as a !PageLRU page could be in the
345 * process of being released, reclaimed, migrated or on a remote
346 * pagevec that is currently being drained. Furthermore, marking
347 * a remote pagevec's page PageActive potentially hits a race where
348 * a page is marked PageActive just after it is added to the inactive
349 * list causing accounting errors and BUG_ON checks to trigger.
350 */
351 for (i = pagevec_count(pvec) - 1; i >= 0; i--) {
352 struct page *pagevec_page = pvec->pages[i];
353
354 if (pagevec_page == page) {
355 SetPageActive(page);
356 break;
357 }
358 }
359
360 put_cpu_var(lru_add_pvec);
361}
362
363/*
364 * Mark a page as having seen activity.
365 *
366 * inactive,unreferenced -> inactive,referenced
367 * inactive,referenced -> active,unreferenced
368 * active,unreferenced -> active,referenced
369 *
370 * When a newly allocated page is not yet visible, so safe for non-atomic ops,
371 * __SetPageReferenced(page) may be substituted for mark_page_accessed(page).
372 */
373void mark_page_accessed(struct page *page)
374{
375 page = compound_head(page);
376 if (!PageActive(page) && !PageUnevictable(page) &&
377 PageReferenced(page)) {
378
379 /*
380 * If the page is on the LRU, queue it for activation via
381 * activate_page_pvecs. Otherwise, assume the page is on a
382 * pagevec, mark it active and it'll be moved to the active
383 * LRU on the next drain.
384 */
385 if (PageLRU(page))
386 activate_page(page);
387 else
388 __lru_cache_activate_page(page);
389 ClearPageReferenced(page);
390 if (page_is_file_cache(page))
391 workingset_activation(page);
392 } else if (!PageReferenced(page)) {
393 SetPageReferenced(page);
394 }
395 if (page_is_idle(page))
396 clear_page_idle(page);
397}
398EXPORT_SYMBOL(mark_page_accessed);
399
400static void __lru_cache_add(struct page *page)
401{
402 struct pagevec *pvec = &get_cpu_var(lru_add_pvec);
403
404 get_page(page);
405 if (!pagevec_add(pvec, page) || PageCompound(page))
406 __pagevec_lru_add(pvec);
407 put_cpu_var(lru_add_pvec);
408}
409
410/**
411 * lru_cache_add_anon - add a page to the page lists
412 * @page: the page to add
413 */
414void lru_cache_add_anon(struct page *page)
415{
416 if (PageActive(page))
417 ClearPageActive(page);
418 __lru_cache_add(page);
419}
420
421void lru_cache_add_file(struct page *page)
422{
423 if (PageActive(page))
424 ClearPageActive(page);
425 __lru_cache_add(page);
426}
427EXPORT_SYMBOL(lru_cache_add_file);
428
429/**
430 * lru_cache_add - add a page to a page list
431 * @page: the page to be added to the LRU.
432 *
433 * Queue the page for addition to the LRU via pagevec. The decision on whether
434 * to add the page to the [in]active [file|anon] list is deferred until the
435 * pagevec is drained. This gives a chance for the caller of lru_cache_add()
436 * have the page added to the active list using mark_page_accessed().
437 */
438void lru_cache_add(struct page *page)
439{
440 VM_BUG_ON_PAGE(PageActive(page) && PageUnevictable(page), page);
441 VM_BUG_ON_PAGE(PageLRU(page), page);
442 __lru_cache_add(page);
443}
444
445/**
446 * lru_cache_add_active_or_unevictable
447 * @page: the page to be added to LRU
448 * @vma: vma in which page is mapped for determining reclaimability
449 *
450 * Place @page on the active or unevictable LRU list, depending on its
451 * evictability. Note that if the page is not evictable, it goes
452 * directly back onto it's zone's unevictable list, it does NOT use a
453 * per cpu pagevec.
454 */
455void lru_cache_add_active_or_unevictable(struct page *page,
456 struct vm_area_struct *vma)
457{
458 VM_BUG_ON_PAGE(PageLRU(page), page);
459
460 if (likely((vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) != VM_LOCKED))
461 SetPageActive(page);
462 else if (!TestSetPageMlocked(page)) {
463 /*
464 * We use the irq-unsafe __mod_zone_page_stat because this
465 * counter is not modified from interrupt context, and the pte
466 * lock is held(spinlock), which implies preemption disabled.
467 */
468 __mod_zone_page_state(page_zone(page), NR_MLOCK,
469 hpage_nr_pages(page));
470 count_vm_event(UNEVICTABLE_PGMLOCKED);
471 }
472 lru_cache_add(page);
473}
474
475/*
476 * If the page can not be invalidated, it is moved to the
477 * inactive list to speed up its reclaim. It is moved to the
478 * head of the list, rather than the tail, to give the flusher
479 * threads some time to write it out, as this is much more
480 * effective than the single-page writeout from reclaim.
481 *
482 * If the page isn't page_mapped and dirty/writeback, the page
483 * could reclaim asap using PG_reclaim.
484 *
485 * 1. active, mapped page -> none
486 * 2. active, dirty/writeback page -> inactive, head, PG_reclaim
487 * 3. inactive, mapped page -> none
488 * 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim
489 * 5. inactive, clean -> inactive, tail
490 * 6. Others -> none
491 *
492 * In 4, why it moves inactive's head, the VM expects the page would
493 * be write it out by flusher threads as this is much more effective
494 * than the single-page writeout from reclaim.
495 */
496static void lru_deactivate_file_fn(struct page *page, struct lruvec *lruvec,
497 void *arg)
498{
499 int lru, file;
500 bool active;
501
502 if (!PageLRU(page))
503 return;
504
505 if (PageUnevictable(page))
506 return;
507
508 /* Some processes are using the page */
509 if (page_mapped(page))
510 return;
511
512 active = PageActive(page);
513 file = page_is_file_cache(page);
514 lru = page_lru_base_type(page);
515
516 del_page_from_lru_list(page, lruvec, lru + active);
517 ClearPageActive(page);
518 ClearPageReferenced(page);
519
520 if (PageWriteback(page) || PageDirty(page)) {
521 /*
522 * PG_reclaim could be raced with end_page_writeback
523 * It can make readahead confusing. But race window
524 * is _really_ small and it's non-critical problem.
525 */
526 add_page_to_lru_list(page, lruvec, lru);
527 SetPageReclaim(page);
528 } else {
529 /*
530 * The page's writeback ends up during pagevec
531 * We moves tha page into tail of inactive.
532 */
533 add_page_to_lru_list_tail(page, lruvec, lru);
534 __count_vm_event(PGROTATED);
535 }
536
537 if (active)
538 __count_vm_event(PGDEACTIVATE);
539 update_page_reclaim_stat(lruvec, file, 0);
540}
541
542static void lru_deactivate_fn(struct page *page, struct lruvec *lruvec,
543 void *arg)
544{
545 if (PageLRU(page) && PageActive(page) && !PageUnevictable(page)) {
546 int file = page_is_file_cache(page);
547 int lru = page_lru_base_type(page);
548
549 del_page_from_lru_list(page, lruvec, lru + LRU_ACTIVE);
550 ClearPageActive(page);
551 ClearPageReferenced(page);
552 add_page_to_lru_list(page, lruvec, lru);
553
554 __count_vm_events(PGDEACTIVATE, hpage_nr_pages(page));
555 update_page_reclaim_stat(lruvec, file, 0);
556 }
557}
558
559static void lru_lazyfree_fn(struct page *page, struct lruvec *lruvec,
560 void *arg)
561{
562 if (PageLRU(page) && PageAnon(page) && PageSwapBacked(page) &&
563 !PageSwapCache(page) && !PageUnevictable(page)) {
564 bool active = PageActive(page);
565
566 del_page_from_lru_list(page, lruvec,
567 LRU_INACTIVE_ANON + active);
568 ClearPageActive(page);
569 ClearPageReferenced(page);
570 /*
571 * lazyfree pages are clean anonymous pages. They have
572 * SwapBacked flag cleared to distinguish normal anonymous
573 * pages
574 */
575 ClearPageSwapBacked(page);
576 add_page_to_lru_list(page, lruvec, LRU_INACTIVE_FILE);
577
578 __count_vm_events(PGLAZYFREE, hpage_nr_pages(page));
579 count_memcg_page_event(page, PGLAZYFREE);
580 update_page_reclaim_stat(lruvec, 1, 0);
581 }
582}
583
584/*
585 * Drain pages out of the cpu's pagevecs.
586 * Either "cpu" is the current CPU, and preemption has already been
587 * disabled; or "cpu" is being hot-unplugged, and is already dead.
588 */
589void lru_add_drain_cpu(int cpu)
590{
591 struct pagevec *pvec = &per_cpu(lru_add_pvec, cpu);
592
593 if (pagevec_count(pvec))
594 __pagevec_lru_add(pvec);
595
596 pvec = &per_cpu(lru_rotate_pvecs, cpu);
597 if (pagevec_count(pvec)) {
598 unsigned long flags;
599
600 /* No harm done if a racing interrupt already did this */
601 local_irq_save(flags);
602 pagevec_move_tail(pvec);
603 local_irq_restore(flags);
604 }
605
606 pvec = &per_cpu(lru_deactivate_file_pvecs, cpu);
607 if (pagevec_count(pvec))
608 pagevec_lru_move_fn(pvec, lru_deactivate_file_fn, NULL);
609
610 pvec = &per_cpu(lru_deactivate_pvecs, cpu);
611 if (pagevec_count(pvec))
612 pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
613
614 pvec = &per_cpu(lru_lazyfree_pvecs, cpu);
615 if (pagevec_count(pvec))
616 pagevec_lru_move_fn(pvec, lru_lazyfree_fn, NULL);
617
618 activate_page_drain(cpu);
619}
620
621/**
622 * deactivate_file_page - forcefully deactivate a file page
623 * @page: page to deactivate
624 *
625 * This function hints the VM that @page is a good reclaim candidate,
626 * for example if its invalidation fails due to the page being dirty
627 * or under writeback.
628 */
629void deactivate_file_page(struct page *page)
630{
631 /*
632 * In a workload with many unevictable page such as mprotect,
633 * unevictable page deactivation for accelerating reclaim is pointless.
634 */
635 if (PageUnevictable(page))
636 return;
637
638 if (likely(get_page_unless_zero(page))) {
639 struct pagevec *pvec = &get_cpu_var(lru_deactivate_file_pvecs);
640
641 if (!pagevec_add(pvec, page) || PageCompound(page))
642 pagevec_lru_move_fn(pvec, lru_deactivate_file_fn, NULL);
643 put_cpu_var(lru_deactivate_file_pvecs);
644 }
645}
646
647/*
648 * deactivate_page - deactivate a page
649 * @page: page to deactivate
650 *
651 * deactivate_page() moves @page to the inactive list if @page was on the active
652 * list and was not an unevictable page. This is done to accelerate the reclaim
653 * of @page.
654 */
655void deactivate_page(struct page *page)
656{
657 if (PageLRU(page) && PageActive(page) && !PageUnevictable(page)) {
658 struct pagevec *pvec = &get_cpu_var(lru_deactivate_pvecs);
659
660 get_page(page);
661 if (!pagevec_add(pvec, page) || PageCompound(page))
662 pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
663 put_cpu_var(lru_deactivate_pvecs);
664 }
665}
666
667/**
668 * mark_page_lazyfree - make an anon page lazyfree
669 * @page: page to deactivate
670 *
671 * mark_page_lazyfree() moves @page to the inactive file list.
672 * This is done to accelerate the reclaim of @page.
673 */
674void mark_page_lazyfree(struct page *page)
675{
676 if (PageLRU(page) && PageAnon(page) && PageSwapBacked(page) &&
677 !PageSwapCache(page) && !PageUnevictable(page)) {
678 struct pagevec *pvec = &get_cpu_var(lru_lazyfree_pvecs);
679
680 get_page(page);
681 if (!pagevec_add(pvec, page) || PageCompound(page))
682 pagevec_lru_move_fn(pvec, lru_lazyfree_fn, NULL);
683 put_cpu_var(lru_lazyfree_pvecs);
684 }
685}
686
687void lru_add_drain(void)
688{
689 lru_add_drain_cpu(get_cpu());
690 put_cpu();
691}
692
693#ifdef CONFIG_SMP
694
695static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work);
696
697static void lru_add_drain_per_cpu(struct work_struct *dummy)
698{
699 lru_add_drain();
700}
701
702/*
703 * Doesn't need any cpu hotplug locking because we do rely on per-cpu
704 * kworkers being shut down before our page_alloc_cpu_dead callback is
705 * executed on the offlined cpu.
706 * Calling this function with cpu hotplug locks held can actually lead
707 * to obscure indirect dependencies via WQ context.
708 */
709void lru_add_drain_all(void)
710{
711 static DEFINE_MUTEX(lock);
712 static struct cpumask has_work;
713 int cpu;
714
715 /*
716 * Make sure nobody triggers this path before mm_percpu_wq is fully
717 * initialized.
718 */
719 if (WARN_ON(!mm_percpu_wq))
720 return;
721
722 mutex_lock(&lock);
723 cpumask_clear(&has_work);
724
725 for_each_online_cpu(cpu) {
726 struct work_struct *work = &per_cpu(lru_add_drain_work, cpu);
727
728 if (pagevec_count(&per_cpu(lru_add_pvec, cpu)) ||
729 pagevec_count(&per_cpu(lru_rotate_pvecs, cpu)) ||
730 pagevec_count(&per_cpu(lru_deactivate_file_pvecs, cpu)) ||
731 pagevec_count(&per_cpu(lru_deactivate_pvecs, cpu)) ||
732 pagevec_count(&per_cpu(lru_lazyfree_pvecs, cpu)) ||
733 need_activate_page_drain(cpu)) {
734 INIT_WORK(work, lru_add_drain_per_cpu);
735 queue_work_on(cpu, mm_percpu_wq, work);
736 cpumask_set_cpu(cpu, &has_work);
737 }
738 }
739
740 for_each_cpu(cpu, &has_work)
741 flush_work(&per_cpu(lru_add_drain_work, cpu));
742
743 mutex_unlock(&lock);
744}
745#else
746void lru_add_drain_all(void)
747{
748 lru_add_drain();
749}
750#endif
751
752/**
753 * release_pages - batched put_page()
754 * @pages: array of pages to release
755 * @nr: number of pages
756 *
757 * Decrement the reference count on all the pages in @pages. If it
758 * fell to zero, remove the page from the LRU and free it.
759 */
760void release_pages(struct page **pages, int nr)
761{
762 int i;
763 LIST_HEAD(pages_to_free);
764 struct pglist_data *locked_pgdat = NULL;
765 struct lruvec *lruvec;
766 unsigned long uninitialized_var(flags);
767 unsigned int uninitialized_var(lock_batch);
768
769 for (i = 0; i < nr; i++) {
770 struct page *page = pages[i];
771
772 /*
773 * Make sure the IRQ-safe lock-holding time does not get
774 * excessive with a continuous string of pages from the
775 * same pgdat. The lock is held only if pgdat != NULL.
776 */
777 if (locked_pgdat && ++lock_batch == SWAP_CLUSTER_MAX) {
778 spin_unlock_irqrestore(&locked_pgdat->lru_lock, flags);
779 locked_pgdat = NULL;
780 }
781
782 if (is_huge_zero_page(page))
783 continue;
784
785 if (is_zone_device_page(page)) {
786 if (locked_pgdat) {
787 spin_unlock_irqrestore(&locked_pgdat->lru_lock,
788 flags);
789 locked_pgdat = NULL;
790 }
791 /*
792 * ZONE_DEVICE pages that return 'false' from
793 * put_devmap_managed_page() do not require special
794 * processing, and instead, expect a call to
795 * put_page_testzero().
796 */
797 if (put_devmap_managed_page(page))
798 continue;
799 }
800
801 page = compound_head(page);
802 if (!put_page_testzero(page))
803 continue;
804
805 if (PageCompound(page)) {
806 if (locked_pgdat) {
807 spin_unlock_irqrestore(&locked_pgdat->lru_lock, flags);
808 locked_pgdat = NULL;
809 }
810 __put_compound_page(page);
811 continue;
812 }
813
814 if (PageLRU(page)) {
815 struct pglist_data *pgdat = page_pgdat(page);
816
817 if (pgdat != locked_pgdat) {
818 if (locked_pgdat)
819 spin_unlock_irqrestore(&locked_pgdat->lru_lock,
820 flags);
821 lock_batch = 0;
822 locked_pgdat = pgdat;
823 spin_lock_irqsave(&locked_pgdat->lru_lock, flags);
824 }
825
826 lruvec = mem_cgroup_page_lruvec(page, locked_pgdat);
827 VM_BUG_ON_PAGE(!PageLRU(page), page);
828 __ClearPageLRU(page);
829 del_page_from_lru_list(page, lruvec, page_off_lru(page));
830 }
831
832 /* Clear Active bit in case of parallel mark_page_accessed */
833 __ClearPageActive(page);
834 __ClearPageWaiters(page);
835
836 list_add(&page->lru, &pages_to_free);
837 }
838 if (locked_pgdat)
839 spin_unlock_irqrestore(&locked_pgdat->lru_lock, flags);
840
841 mem_cgroup_uncharge_list(&pages_to_free);
842 free_unref_page_list(&pages_to_free);
843}
844EXPORT_SYMBOL(release_pages);
845
846/*
847 * The pages which we're about to release may be in the deferred lru-addition
848 * queues. That would prevent them from really being freed right now. That's
849 * OK from a correctness point of view but is inefficient - those pages may be
850 * cache-warm and we want to give them back to the page allocator ASAP.
851 *
852 * So __pagevec_release() will drain those queues here. __pagevec_lru_add()
853 * and __pagevec_lru_add_active() call release_pages() directly to avoid
854 * mutual recursion.
855 */
856void __pagevec_release(struct pagevec *pvec)
857{
858 if (!pvec->percpu_pvec_drained) {
859 lru_add_drain();
860 pvec->percpu_pvec_drained = true;
861 }
862 release_pages(pvec->pages, pagevec_count(pvec));
863 pagevec_reinit(pvec);
864}
865EXPORT_SYMBOL(__pagevec_release);
866
867#ifdef CONFIG_TRANSPARENT_HUGEPAGE
868/* used by __split_huge_page_refcount() */
869void lru_add_page_tail(struct page *page, struct page *page_tail,
870 struct lruvec *lruvec, struct list_head *list)
871{
872 const int file = 0;
873
874 VM_BUG_ON_PAGE(!PageHead(page), page);
875 VM_BUG_ON_PAGE(PageCompound(page_tail), page);
876 VM_BUG_ON_PAGE(PageLRU(page_tail), page);
877 lockdep_assert_held(&lruvec_pgdat(lruvec)->lru_lock);
878
879 if (!list)
880 SetPageLRU(page_tail);
881
882 if (likely(PageLRU(page)))
883 list_add_tail(&page_tail->lru, &page->lru);
884 else if (list) {
885 /* page reclaim is reclaiming a huge page */
886 get_page(page_tail);
887 list_add_tail(&page_tail->lru, list);
888 } else {
889 /*
890 * Head page has not yet been counted, as an hpage,
891 * so we must account for each subpage individually.
892 *
893 * Put page_tail on the list at the correct position
894 * so they all end up in order.
895 */
896 add_page_to_lru_list_tail(page_tail, lruvec,
897 page_lru(page_tail));
898 }
899
900 if (!PageUnevictable(page))
901 update_page_reclaim_stat(lruvec, file, PageActive(page_tail));
902}
903#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
904
905static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec,
906 void *arg)
907{
908 enum lru_list lru;
909 int was_unevictable = TestClearPageUnevictable(page);
910
911 VM_BUG_ON_PAGE(PageLRU(page), page);
912
913 SetPageLRU(page);
914 /*
915 * Page becomes evictable in two ways:
916 * 1) Within LRU lock [munlock_vma_page() and __munlock_pagevec()].
917 * 2) Before acquiring LRU lock to put the page to correct LRU and then
918 * a) do PageLRU check with lock [check_move_unevictable_pages]
919 * b) do PageLRU check before lock [clear_page_mlock]
920 *
921 * (1) & (2a) are ok as LRU lock will serialize them. For (2b), we need
922 * following strict ordering:
923 *
924 * #0: __pagevec_lru_add_fn #1: clear_page_mlock
925 *
926 * SetPageLRU() TestClearPageMlocked()
927 * smp_mb() // explicit ordering // above provides strict
928 * // ordering
929 * PageMlocked() PageLRU()
930 *
931 *
932 * if '#1' does not observe setting of PG_lru by '#0' and fails
933 * isolation, the explicit barrier will make sure that page_evictable
934 * check will put the page in correct LRU. Without smp_mb(), SetPageLRU
935 * can be reordered after PageMlocked check and can make '#1' to fail
936 * the isolation of the page whose Mlocked bit is cleared (#0 is also
937 * looking at the same page) and the evictable page will be stranded
938 * in an unevictable LRU.
939 */
940 smp_mb();
941
942 if (page_evictable(page)) {
943 lru = page_lru(page);
944 update_page_reclaim_stat(lruvec, page_is_file_cache(page),
945 PageActive(page));
946 if (was_unevictable)
947 count_vm_event(UNEVICTABLE_PGRESCUED);
948 } else {
949 lru = LRU_UNEVICTABLE;
950 ClearPageActive(page);
951 SetPageUnevictable(page);
952 if (!was_unevictable)
953 count_vm_event(UNEVICTABLE_PGCULLED);
954 }
955
956 add_page_to_lru_list(page, lruvec, lru);
957 trace_mm_lru_insertion(page, lru);
958}
959
960/*
961 * Add the passed pages to the LRU, then drop the caller's refcount
962 * on them. Reinitialises the caller's pagevec.
963 */
964void __pagevec_lru_add(struct pagevec *pvec)
965{
966 pagevec_lru_move_fn(pvec, __pagevec_lru_add_fn, NULL);
967}
968EXPORT_SYMBOL(__pagevec_lru_add);
969
970/**
971 * pagevec_lookup_entries - gang pagecache lookup
972 * @pvec: Where the resulting entries are placed
973 * @mapping: The address_space to search
974 * @start: The starting entry index
975 * @nr_entries: The maximum number of pages
976 * @indices: The cache indices corresponding to the entries in @pvec
977 *
978 * pagevec_lookup_entries() will search for and return a group of up
979 * to @nr_pages pages and shadow entries in the mapping. All
980 * entries are placed in @pvec. pagevec_lookup_entries() takes a
981 * reference against actual pages in @pvec.
982 *
983 * The search returns a group of mapping-contiguous entries with
984 * ascending indexes. There may be holes in the indices due to
985 * not-present entries.
986 *
987 * pagevec_lookup_entries() returns the number of entries which were
988 * found.
989 */
990unsigned pagevec_lookup_entries(struct pagevec *pvec,
991 struct address_space *mapping,
992 pgoff_t start, unsigned nr_entries,
993 pgoff_t *indices)
994{
995 pvec->nr = find_get_entries(mapping, start, nr_entries,
996 pvec->pages, indices);
997 return pagevec_count(pvec);
998}
999
1000/**
1001 * pagevec_remove_exceptionals - pagevec exceptionals pruning
1002 * @pvec: The pagevec to prune
1003 *
1004 * pagevec_lookup_entries() fills both pages and exceptional radix
1005 * tree entries into the pagevec. This function prunes all
1006 * exceptionals from @pvec without leaving holes, so that it can be
1007 * passed on to page-only pagevec operations.
1008 */
1009void pagevec_remove_exceptionals(struct pagevec *pvec)
1010{
1011 int i, j;
1012
1013 for (i = 0, j = 0; i < pagevec_count(pvec); i++) {
1014 struct page *page = pvec->pages[i];
1015 if (!xa_is_value(page))
1016 pvec->pages[j++] = page;
1017 }
1018 pvec->nr = j;
1019}
1020
1021/**
1022 * pagevec_lookup_range - gang pagecache lookup
1023 * @pvec: Where the resulting pages are placed
1024 * @mapping: The address_space to search
1025 * @start: The starting page index
1026 * @end: The final page index
1027 *
1028 * pagevec_lookup_range() will search for & return a group of up to PAGEVEC_SIZE
1029 * pages in the mapping starting from index @start and upto index @end
1030 * (inclusive). The pages are placed in @pvec. pagevec_lookup() takes a
1031 * reference against the pages in @pvec.
1032 *
1033 * The search returns a group of mapping-contiguous pages with ascending
1034 * indexes. There may be holes in the indices due to not-present pages. We
1035 * also update @start to index the next page for the traversal.
1036 *
1037 * pagevec_lookup_range() returns the number of pages which were found. If this
1038 * number is smaller than PAGEVEC_SIZE, the end of specified range has been
1039 * reached.
1040 */
1041unsigned pagevec_lookup_range(struct pagevec *pvec,
1042 struct address_space *mapping, pgoff_t *start, pgoff_t end)
1043{
1044 pvec->nr = find_get_pages_range(mapping, start, end, PAGEVEC_SIZE,
1045 pvec->pages);
1046 return pagevec_count(pvec);
1047}
1048EXPORT_SYMBOL(pagevec_lookup_range);
1049
1050unsigned pagevec_lookup_range_tag(struct pagevec *pvec,
1051 struct address_space *mapping, pgoff_t *index, pgoff_t end,
1052 xa_mark_t tag)
1053{
1054 pvec->nr = find_get_pages_range_tag(mapping, index, end, tag,
1055 PAGEVEC_SIZE, pvec->pages);
1056 return pagevec_count(pvec);
1057}
1058EXPORT_SYMBOL(pagevec_lookup_range_tag);
1059
1060unsigned pagevec_lookup_range_nr_tag(struct pagevec *pvec,
1061 struct address_space *mapping, pgoff_t *index, pgoff_t end,
1062 xa_mark_t tag, unsigned max_pages)
1063{
1064 pvec->nr = find_get_pages_range_tag(mapping, index, end, tag,
1065 min_t(unsigned int, max_pages, PAGEVEC_SIZE), pvec->pages);
1066 return pagevec_count(pvec);
1067}
1068EXPORT_SYMBOL(pagevec_lookup_range_nr_tag);
1069/*
1070 * Perform any setup for the swap system
1071 */
1072void __init swap_setup(void)
1073{
1074 unsigned long megs = totalram_pages() >> (20 - PAGE_SHIFT);
1075
1076 /* Use a smaller cluster for small-memory machines */
1077 if (megs < 16)
1078 page_cluster = 2;
1079 else
1080 page_cluster = 3;
1081 /*
1082 * Right now other parts of the system means that we
1083 * _really_ don't want to cluster much more
1084 */
1085}
1/*
2 * linux/mm/swap.c
3 *
4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
5 */
6
7/*
8 * This file contains the default values for the operation of the
9 * Linux VM subsystem. Fine-tuning documentation can be found in
10 * Documentation/sysctl/vm.txt.
11 * Started 18.12.91
12 * Swap aging added 23.2.95, Stephen Tweedie.
13 * Buffermem limits added 12.3.98, Rik van Riel.
14 */
15
16#include <linux/mm.h>
17#include <linux/sched.h>
18#include <linux/kernel_stat.h>
19#include <linux/swap.h>
20#include <linux/mman.h>
21#include <linux/pagemap.h>
22#include <linux/pagevec.h>
23#include <linux/init.h>
24#include <linux/export.h>
25#include <linux/mm_inline.h>
26#include <linux/percpu_counter.h>
27#include <linux/percpu.h>
28#include <linux/cpu.h>
29#include <linux/notifier.h>
30#include <linux/backing-dev.h>
31#include <linux/memcontrol.h>
32#include <linux/gfp.h>
33#include <linux/uio.h>
34
35#include "internal.h"
36
37#define CREATE_TRACE_POINTS
38#include <trace/events/pagemap.h>
39
40/* How many pages do we try to swap or page in/out together? */
41int page_cluster;
42
43static DEFINE_PER_CPU(struct pagevec, lru_add_pvec);
44static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs);
45static DEFINE_PER_CPU(struct pagevec, lru_deactivate_pvecs);
46
47/*
48 * This path almost never happens for VM activity - pages are normally
49 * freed via pagevecs. But it gets used by networking.
50 */
51static void __page_cache_release(struct page *page)
52{
53 if (PageLRU(page)) {
54 struct zone *zone = page_zone(page);
55 struct lruvec *lruvec;
56 unsigned long flags;
57
58 spin_lock_irqsave(&zone->lru_lock, flags);
59 lruvec = mem_cgroup_page_lruvec(page, zone);
60 VM_BUG_ON_PAGE(!PageLRU(page), page);
61 __ClearPageLRU(page);
62 del_page_from_lru_list(page, lruvec, page_off_lru(page));
63 spin_unlock_irqrestore(&zone->lru_lock, flags);
64 }
65}
66
67static void __put_single_page(struct page *page)
68{
69 __page_cache_release(page);
70 free_hot_cold_page(page, 0);
71}
72
73static void __put_compound_page(struct page *page)
74{
75 compound_page_dtor *dtor;
76
77 __page_cache_release(page);
78 dtor = get_compound_page_dtor(page);
79 (*dtor)(page);
80}
81
82static void put_compound_page(struct page *page)
83{
84 struct page *page_head;
85
86 if (likely(!PageTail(page))) {
87 if (put_page_testzero(page)) {
88 /*
89 * By the time all refcounts have been released
90 * split_huge_page cannot run anymore from under us.
91 */
92 if (PageHead(page))
93 __put_compound_page(page);
94 else
95 __put_single_page(page);
96 }
97 return;
98 }
99
100 /* __split_huge_page_refcount can run under us */
101 page_head = compound_head(page);
102
103 /*
104 * THP can not break up slab pages so avoid taking
105 * compound_lock() and skip the tail page refcounting (in
106 * _mapcount) too. Slab performs non-atomic bit ops on
107 * page->flags for better performance. In particular
108 * slab_unlock() in slub used to be a hot path. It is still
109 * hot on arches that do not support
110 * this_cpu_cmpxchg_double().
111 *
112 * If "page" is part of a slab or hugetlbfs page it cannot be
113 * splitted and the head page cannot change from under us. And
114 * if "page" is part of a THP page under splitting, if the
115 * head page pointed by the THP tail isn't a THP head anymore,
116 * we'll find PageTail clear after smp_rmb() and we'll treat
117 * it as a single page.
118 */
119 if (!__compound_tail_refcounted(page_head)) {
120 /*
121 * If "page" is a THP tail, we must read the tail page
122 * flags after the head page flags. The
123 * split_huge_page side enforces write memory barriers
124 * between clearing PageTail and before the head page
125 * can be freed and reallocated.
126 */
127 smp_rmb();
128 if (likely(PageTail(page))) {
129 /*
130 * __split_huge_page_refcount cannot race
131 * here.
132 */
133 VM_BUG_ON_PAGE(!PageHead(page_head), page_head);
134 VM_BUG_ON_PAGE(page_mapcount(page) != 0, page);
135 if (put_page_testzero(page_head)) {
136 /*
137 * If this is the tail of a slab
138 * compound page, the tail pin must
139 * not be the last reference held on
140 * the page, because the PG_slab
141 * cannot be cleared before all tail
142 * pins (which skips the _mapcount
143 * tail refcounting) have been
144 * released. For hugetlbfs the tail
145 * pin may be the last reference on
146 * the page instead, because
147 * PageHeadHuge will not go away until
148 * the compound page enters the buddy
149 * allocator.
150 */
151 VM_BUG_ON_PAGE(PageSlab(page_head), page_head);
152 __put_compound_page(page_head);
153 }
154 return;
155 } else
156 /*
157 * __split_huge_page_refcount run before us,
158 * "page" was a THP tail. The split page_head
159 * has been freed and reallocated as slab or
160 * hugetlbfs page of smaller order (only
161 * possible if reallocated as slab on x86).
162 */
163 goto out_put_single;
164 }
165
166 if (likely(page != page_head && get_page_unless_zero(page_head))) {
167 unsigned long flags;
168
169 /*
170 * page_head wasn't a dangling pointer but it may not
171 * be a head page anymore by the time we obtain the
172 * lock. That is ok as long as it can't be freed from
173 * under us.
174 */
175 flags = compound_lock_irqsave(page_head);
176 if (unlikely(!PageTail(page))) {
177 /* __split_huge_page_refcount run before us */
178 compound_unlock_irqrestore(page_head, flags);
179 if (put_page_testzero(page_head)) {
180 /*
181 * The head page may have been freed
182 * and reallocated as a compound page
183 * of smaller order and then freed
184 * again. All we know is that it
185 * cannot have become: a THP page, a
186 * compound page of higher order, a
187 * tail page. That is because we
188 * still hold the refcount of the
189 * split THP tail and page_head was
190 * the THP head before the split.
191 */
192 if (PageHead(page_head))
193 __put_compound_page(page_head);
194 else
195 __put_single_page(page_head);
196 }
197out_put_single:
198 if (put_page_testzero(page))
199 __put_single_page(page);
200 return;
201 }
202 VM_BUG_ON_PAGE(page_head != page->first_page, page);
203 /*
204 * We can release the refcount taken by
205 * get_page_unless_zero() now that
206 * __split_huge_page_refcount() is blocked on the
207 * compound_lock.
208 */
209 if (put_page_testzero(page_head))
210 VM_BUG_ON_PAGE(1, page_head);
211 /* __split_huge_page_refcount will wait now */
212 VM_BUG_ON_PAGE(page_mapcount(page) <= 0, page);
213 atomic_dec(&page->_mapcount);
214 VM_BUG_ON_PAGE(atomic_read(&page_head->_count) <= 0, page_head);
215 VM_BUG_ON_PAGE(atomic_read(&page->_count) != 0, page);
216 compound_unlock_irqrestore(page_head, flags);
217
218 if (put_page_testzero(page_head)) {
219 if (PageHead(page_head))
220 __put_compound_page(page_head);
221 else
222 __put_single_page(page_head);
223 }
224 } else {
225 /* page_head is a dangling pointer */
226 VM_BUG_ON_PAGE(PageTail(page), page);
227 goto out_put_single;
228 }
229}
230
231void put_page(struct page *page)
232{
233 if (unlikely(PageCompound(page)))
234 put_compound_page(page);
235 else if (put_page_testzero(page))
236 __put_single_page(page);
237}
238EXPORT_SYMBOL(put_page);
239
240/*
241 * This function is exported but must not be called by anything other
242 * than get_page(). It implements the slow path of get_page().
243 */
244bool __get_page_tail(struct page *page)
245{
246 /*
247 * This takes care of get_page() if run on a tail page
248 * returned by one of the get_user_pages/follow_page variants.
249 * get_user_pages/follow_page itself doesn't need the compound
250 * lock because it runs __get_page_tail_foll() under the
251 * proper PT lock that already serializes against
252 * split_huge_page().
253 */
254 unsigned long flags;
255 bool got;
256 struct page *page_head = compound_head(page);
257
258 /* Ref to put_compound_page() comment. */
259 if (!__compound_tail_refcounted(page_head)) {
260 smp_rmb();
261 if (likely(PageTail(page))) {
262 /*
263 * This is a hugetlbfs page or a slab
264 * page. __split_huge_page_refcount
265 * cannot race here.
266 */
267 VM_BUG_ON_PAGE(!PageHead(page_head), page_head);
268 __get_page_tail_foll(page, true);
269 return true;
270 } else {
271 /*
272 * __split_huge_page_refcount run
273 * before us, "page" was a THP
274 * tail. The split page_head has been
275 * freed and reallocated as slab or
276 * hugetlbfs page of smaller order
277 * (only possible if reallocated as
278 * slab on x86).
279 */
280 return false;
281 }
282 }
283
284 got = false;
285 if (likely(page != page_head && get_page_unless_zero(page_head))) {
286 /*
287 * page_head wasn't a dangling pointer but it
288 * may not be a head page anymore by the time
289 * we obtain the lock. That is ok as long as it
290 * can't be freed from under us.
291 */
292 flags = compound_lock_irqsave(page_head);
293 /* here __split_huge_page_refcount won't run anymore */
294 if (likely(PageTail(page))) {
295 __get_page_tail_foll(page, false);
296 got = true;
297 }
298 compound_unlock_irqrestore(page_head, flags);
299 if (unlikely(!got))
300 put_page(page_head);
301 }
302 return got;
303}
304EXPORT_SYMBOL(__get_page_tail);
305
306/**
307 * put_pages_list() - release a list of pages
308 * @pages: list of pages threaded on page->lru
309 *
310 * Release a list of pages which are strung together on page.lru. Currently
311 * used by read_cache_pages() and related error recovery code.
312 */
313void put_pages_list(struct list_head *pages)
314{
315 while (!list_empty(pages)) {
316 struct page *victim;
317
318 victim = list_entry(pages->prev, struct page, lru);
319 list_del(&victim->lru);
320 page_cache_release(victim);
321 }
322}
323EXPORT_SYMBOL(put_pages_list);
324
325/*
326 * get_kernel_pages() - pin kernel pages in memory
327 * @kiov: An array of struct kvec structures
328 * @nr_segs: number of segments to pin
329 * @write: pinning for read/write, currently ignored
330 * @pages: array that receives pointers to the pages pinned.
331 * Should be at least nr_segs long.
332 *
333 * Returns number of pages pinned. This may be fewer than the number
334 * requested. If nr_pages is 0 or negative, returns 0. If no pages
335 * were pinned, returns -errno. Each page returned must be released
336 * with a put_page() call when it is finished with.
337 */
338int get_kernel_pages(const struct kvec *kiov, int nr_segs, int write,
339 struct page **pages)
340{
341 int seg;
342
343 for (seg = 0; seg < nr_segs; seg++) {
344 if (WARN_ON(kiov[seg].iov_len != PAGE_SIZE))
345 return seg;
346
347 pages[seg] = kmap_to_page(kiov[seg].iov_base);
348 page_cache_get(pages[seg]);
349 }
350
351 return seg;
352}
353EXPORT_SYMBOL_GPL(get_kernel_pages);
354
355/*
356 * get_kernel_page() - pin a kernel page in memory
357 * @start: starting kernel address
358 * @write: pinning for read/write, currently ignored
359 * @pages: array that receives pointer to the page pinned.
360 * Must be at least nr_segs long.
361 *
362 * Returns 1 if page is pinned. If the page was not pinned, returns
363 * -errno. The page returned must be released with a put_page() call
364 * when it is finished with.
365 */
366int get_kernel_page(unsigned long start, int write, struct page **pages)
367{
368 const struct kvec kiov = {
369 .iov_base = (void *)start,
370 .iov_len = PAGE_SIZE
371 };
372
373 return get_kernel_pages(&kiov, 1, write, pages);
374}
375EXPORT_SYMBOL_GPL(get_kernel_page);
376
377static void pagevec_lru_move_fn(struct pagevec *pvec,
378 void (*move_fn)(struct page *page, struct lruvec *lruvec, void *arg),
379 void *arg)
380{
381 int i;
382 struct zone *zone = NULL;
383 struct lruvec *lruvec;
384 unsigned long flags = 0;
385
386 for (i = 0; i < pagevec_count(pvec); i++) {
387 struct page *page = pvec->pages[i];
388 struct zone *pagezone = page_zone(page);
389
390 if (pagezone != zone) {
391 if (zone)
392 spin_unlock_irqrestore(&zone->lru_lock, flags);
393 zone = pagezone;
394 spin_lock_irqsave(&zone->lru_lock, flags);
395 }
396
397 lruvec = mem_cgroup_page_lruvec(page, zone);
398 (*move_fn)(page, lruvec, arg);
399 }
400 if (zone)
401 spin_unlock_irqrestore(&zone->lru_lock, flags);
402 release_pages(pvec->pages, pvec->nr, pvec->cold);
403 pagevec_reinit(pvec);
404}
405
406static void pagevec_move_tail_fn(struct page *page, struct lruvec *lruvec,
407 void *arg)
408{
409 int *pgmoved = arg;
410
411 if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
412 enum lru_list lru = page_lru_base_type(page);
413 list_move_tail(&page->lru, &lruvec->lists[lru]);
414 (*pgmoved)++;
415 }
416}
417
418/*
419 * pagevec_move_tail() must be called with IRQ disabled.
420 * Otherwise this may cause nasty races.
421 */
422static void pagevec_move_tail(struct pagevec *pvec)
423{
424 int pgmoved = 0;
425
426 pagevec_lru_move_fn(pvec, pagevec_move_tail_fn, &pgmoved);
427 __count_vm_events(PGROTATED, pgmoved);
428}
429
430/*
431 * Writeback is about to end against a page which has been marked for immediate
432 * reclaim. If it still appears to be reclaimable, move it to the tail of the
433 * inactive list.
434 */
435void rotate_reclaimable_page(struct page *page)
436{
437 if (!PageLocked(page) && !PageDirty(page) && !PageActive(page) &&
438 !PageUnevictable(page) && PageLRU(page)) {
439 struct pagevec *pvec;
440 unsigned long flags;
441
442 page_cache_get(page);
443 local_irq_save(flags);
444 pvec = &__get_cpu_var(lru_rotate_pvecs);
445 if (!pagevec_add(pvec, page))
446 pagevec_move_tail(pvec);
447 local_irq_restore(flags);
448 }
449}
450
451static void update_page_reclaim_stat(struct lruvec *lruvec,
452 int file, int rotated)
453{
454 struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
455
456 reclaim_stat->recent_scanned[file]++;
457 if (rotated)
458 reclaim_stat->recent_rotated[file]++;
459}
460
461static void __activate_page(struct page *page, struct lruvec *lruvec,
462 void *arg)
463{
464 if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
465 int file = page_is_file_cache(page);
466 int lru = page_lru_base_type(page);
467
468 del_page_from_lru_list(page, lruvec, lru);
469 SetPageActive(page);
470 lru += LRU_ACTIVE;
471 add_page_to_lru_list(page, lruvec, lru);
472 trace_mm_lru_activate(page, page_to_pfn(page));
473
474 __count_vm_event(PGACTIVATE);
475 update_page_reclaim_stat(lruvec, file, 1);
476 }
477}
478
479#ifdef CONFIG_SMP
480static DEFINE_PER_CPU(struct pagevec, activate_page_pvecs);
481
482static void activate_page_drain(int cpu)
483{
484 struct pagevec *pvec = &per_cpu(activate_page_pvecs, cpu);
485
486 if (pagevec_count(pvec))
487 pagevec_lru_move_fn(pvec, __activate_page, NULL);
488}
489
490static bool need_activate_page_drain(int cpu)
491{
492 return pagevec_count(&per_cpu(activate_page_pvecs, cpu)) != 0;
493}
494
495void activate_page(struct page *page)
496{
497 if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
498 struct pagevec *pvec = &get_cpu_var(activate_page_pvecs);
499
500 page_cache_get(page);
501 if (!pagevec_add(pvec, page))
502 pagevec_lru_move_fn(pvec, __activate_page, NULL);
503 put_cpu_var(activate_page_pvecs);
504 }
505}
506
507#else
508static inline void activate_page_drain(int cpu)
509{
510}
511
512static bool need_activate_page_drain(int cpu)
513{
514 return false;
515}
516
517void activate_page(struct page *page)
518{
519 struct zone *zone = page_zone(page);
520
521 spin_lock_irq(&zone->lru_lock);
522 __activate_page(page, mem_cgroup_page_lruvec(page, zone), NULL);
523 spin_unlock_irq(&zone->lru_lock);
524}
525#endif
526
527static void __lru_cache_activate_page(struct page *page)
528{
529 struct pagevec *pvec = &get_cpu_var(lru_add_pvec);
530 int i;
531
532 /*
533 * Search backwards on the optimistic assumption that the page being
534 * activated has just been added to this pagevec. Note that only
535 * the local pagevec is examined as a !PageLRU page could be in the
536 * process of being released, reclaimed, migrated or on a remote
537 * pagevec that is currently being drained. Furthermore, marking
538 * a remote pagevec's page PageActive potentially hits a race where
539 * a page is marked PageActive just after it is added to the inactive
540 * list causing accounting errors and BUG_ON checks to trigger.
541 */
542 for (i = pagevec_count(pvec) - 1; i >= 0; i--) {
543 struct page *pagevec_page = pvec->pages[i];
544
545 if (pagevec_page == page) {
546 SetPageActive(page);
547 break;
548 }
549 }
550
551 put_cpu_var(lru_add_pvec);
552}
553
554/*
555 * Mark a page as having seen activity.
556 *
557 * inactive,unreferenced -> inactive,referenced
558 * inactive,referenced -> active,unreferenced
559 * active,unreferenced -> active,referenced
560 */
561void mark_page_accessed(struct page *page)
562{
563 if (!PageActive(page) && !PageUnevictable(page) &&
564 PageReferenced(page)) {
565
566 /*
567 * If the page is on the LRU, queue it for activation via
568 * activate_page_pvecs. Otherwise, assume the page is on a
569 * pagevec, mark it active and it'll be moved to the active
570 * LRU on the next drain.
571 */
572 if (PageLRU(page))
573 activate_page(page);
574 else
575 __lru_cache_activate_page(page);
576 ClearPageReferenced(page);
577 if (page_is_file_cache(page))
578 workingset_activation(page);
579 } else if (!PageReferenced(page)) {
580 SetPageReferenced(page);
581 }
582}
583EXPORT_SYMBOL(mark_page_accessed);
584
585/*
586 * Queue the page for addition to the LRU via pagevec. The decision on whether
587 * to add the page to the [in]active [file|anon] list is deferred until the
588 * pagevec is drained. This gives a chance for the caller of __lru_cache_add()
589 * have the page added to the active list using mark_page_accessed().
590 */
591void __lru_cache_add(struct page *page)
592{
593 struct pagevec *pvec = &get_cpu_var(lru_add_pvec);
594
595 page_cache_get(page);
596 if (!pagevec_space(pvec))
597 __pagevec_lru_add(pvec);
598 pagevec_add(pvec, page);
599 put_cpu_var(lru_add_pvec);
600}
601EXPORT_SYMBOL(__lru_cache_add);
602
603/**
604 * lru_cache_add - add a page to a page list
605 * @page: the page to be added to the LRU.
606 */
607void lru_cache_add(struct page *page)
608{
609 VM_BUG_ON_PAGE(PageActive(page) && PageUnevictable(page), page);
610 VM_BUG_ON_PAGE(PageLRU(page), page);
611 __lru_cache_add(page);
612}
613
614/**
615 * add_page_to_unevictable_list - add a page to the unevictable list
616 * @page: the page to be added to the unevictable list
617 *
618 * Add page directly to its zone's unevictable list. To avoid races with
619 * tasks that might be making the page evictable, through eg. munlock,
620 * munmap or exit, while it's not on the lru, we want to add the page
621 * while it's locked or otherwise "invisible" to other tasks. This is
622 * difficult to do when using the pagevec cache, so bypass that.
623 */
624void add_page_to_unevictable_list(struct page *page)
625{
626 struct zone *zone = page_zone(page);
627 struct lruvec *lruvec;
628
629 spin_lock_irq(&zone->lru_lock);
630 lruvec = mem_cgroup_page_lruvec(page, zone);
631 ClearPageActive(page);
632 SetPageUnevictable(page);
633 SetPageLRU(page);
634 add_page_to_lru_list(page, lruvec, LRU_UNEVICTABLE);
635 spin_unlock_irq(&zone->lru_lock);
636}
637
638/*
639 * If the page can not be invalidated, it is moved to the
640 * inactive list to speed up its reclaim. It is moved to the
641 * head of the list, rather than the tail, to give the flusher
642 * threads some time to write it out, as this is much more
643 * effective than the single-page writeout from reclaim.
644 *
645 * If the page isn't page_mapped and dirty/writeback, the page
646 * could reclaim asap using PG_reclaim.
647 *
648 * 1. active, mapped page -> none
649 * 2. active, dirty/writeback page -> inactive, head, PG_reclaim
650 * 3. inactive, mapped page -> none
651 * 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim
652 * 5. inactive, clean -> inactive, tail
653 * 6. Others -> none
654 *
655 * In 4, why it moves inactive's head, the VM expects the page would
656 * be write it out by flusher threads as this is much more effective
657 * than the single-page writeout from reclaim.
658 */
659static void lru_deactivate_fn(struct page *page, struct lruvec *lruvec,
660 void *arg)
661{
662 int lru, file;
663 bool active;
664
665 if (!PageLRU(page))
666 return;
667
668 if (PageUnevictable(page))
669 return;
670
671 /* Some processes are using the page */
672 if (page_mapped(page))
673 return;
674
675 active = PageActive(page);
676 file = page_is_file_cache(page);
677 lru = page_lru_base_type(page);
678
679 del_page_from_lru_list(page, lruvec, lru + active);
680 ClearPageActive(page);
681 ClearPageReferenced(page);
682 add_page_to_lru_list(page, lruvec, lru);
683
684 if (PageWriteback(page) || PageDirty(page)) {
685 /*
686 * PG_reclaim could be raced with end_page_writeback
687 * It can make readahead confusing. But race window
688 * is _really_ small and it's non-critical problem.
689 */
690 SetPageReclaim(page);
691 } else {
692 /*
693 * The page's writeback ends up during pagevec
694 * We moves tha page into tail of inactive.
695 */
696 list_move_tail(&page->lru, &lruvec->lists[lru]);
697 __count_vm_event(PGROTATED);
698 }
699
700 if (active)
701 __count_vm_event(PGDEACTIVATE);
702 update_page_reclaim_stat(lruvec, file, 0);
703}
704
705/*
706 * Drain pages out of the cpu's pagevecs.
707 * Either "cpu" is the current CPU, and preemption has already been
708 * disabled; or "cpu" is being hot-unplugged, and is already dead.
709 */
710void lru_add_drain_cpu(int cpu)
711{
712 struct pagevec *pvec = &per_cpu(lru_add_pvec, cpu);
713
714 if (pagevec_count(pvec))
715 __pagevec_lru_add(pvec);
716
717 pvec = &per_cpu(lru_rotate_pvecs, cpu);
718 if (pagevec_count(pvec)) {
719 unsigned long flags;
720
721 /* No harm done if a racing interrupt already did this */
722 local_irq_save(flags);
723 pagevec_move_tail(pvec);
724 local_irq_restore(flags);
725 }
726
727 pvec = &per_cpu(lru_deactivate_pvecs, cpu);
728 if (pagevec_count(pvec))
729 pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
730
731 activate_page_drain(cpu);
732}
733
734/**
735 * deactivate_page - forcefully deactivate a page
736 * @page: page to deactivate
737 *
738 * This function hints the VM that @page is a good reclaim candidate,
739 * for example if its invalidation fails due to the page being dirty
740 * or under writeback.
741 */
742void deactivate_page(struct page *page)
743{
744 /*
745 * In a workload with many unevictable page such as mprotect, unevictable
746 * page deactivation for accelerating reclaim is pointless.
747 */
748 if (PageUnevictable(page))
749 return;
750
751 if (likely(get_page_unless_zero(page))) {
752 struct pagevec *pvec = &get_cpu_var(lru_deactivate_pvecs);
753
754 if (!pagevec_add(pvec, page))
755 pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
756 put_cpu_var(lru_deactivate_pvecs);
757 }
758}
759
760void lru_add_drain(void)
761{
762 lru_add_drain_cpu(get_cpu());
763 put_cpu();
764}
765
766static void lru_add_drain_per_cpu(struct work_struct *dummy)
767{
768 lru_add_drain();
769}
770
771static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work);
772
773void lru_add_drain_all(void)
774{
775 static DEFINE_MUTEX(lock);
776 static struct cpumask has_work;
777 int cpu;
778
779 mutex_lock(&lock);
780 get_online_cpus();
781 cpumask_clear(&has_work);
782
783 for_each_online_cpu(cpu) {
784 struct work_struct *work = &per_cpu(lru_add_drain_work, cpu);
785
786 if (pagevec_count(&per_cpu(lru_add_pvec, cpu)) ||
787 pagevec_count(&per_cpu(lru_rotate_pvecs, cpu)) ||
788 pagevec_count(&per_cpu(lru_deactivate_pvecs, cpu)) ||
789 need_activate_page_drain(cpu)) {
790 INIT_WORK(work, lru_add_drain_per_cpu);
791 schedule_work_on(cpu, work);
792 cpumask_set_cpu(cpu, &has_work);
793 }
794 }
795
796 for_each_cpu(cpu, &has_work)
797 flush_work(&per_cpu(lru_add_drain_work, cpu));
798
799 put_online_cpus();
800 mutex_unlock(&lock);
801}
802
803/*
804 * Batched page_cache_release(). Decrement the reference count on all the
805 * passed pages. If it fell to zero then remove the page from the LRU and
806 * free it.
807 *
808 * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
809 * for the remainder of the operation.
810 *
811 * The locking in this function is against shrink_inactive_list(): we recheck
812 * the page count inside the lock to see whether shrink_inactive_list()
813 * grabbed the page via the LRU. If it did, give up: shrink_inactive_list()
814 * will free it.
815 */
816void release_pages(struct page **pages, int nr, int cold)
817{
818 int i;
819 LIST_HEAD(pages_to_free);
820 struct zone *zone = NULL;
821 struct lruvec *lruvec;
822 unsigned long uninitialized_var(flags);
823
824 for (i = 0; i < nr; i++) {
825 struct page *page = pages[i];
826
827 if (unlikely(PageCompound(page))) {
828 if (zone) {
829 spin_unlock_irqrestore(&zone->lru_lock, flags);
830 zone = NULL;
831 }
832 put_compound_page(page);
833 continue;
834 }
835
836 if (!put_page_testzero(page))
837 continue;
838
839 if (PageLRU(page)) {
840 struct zone *pagezone = page_zone(page);
841
842 if (pagezone != zone) {
843 if (zone)
844 spin_unlock_irqrestore(&zone->lru_lock,
845 flags);
846 zone = pagezone;
847 spin_lock_irqsave(&zone->lru_lock, flags);
848 }
849
850 lruvec = mem_cgroup_page_lruvec(page, zone);
851 VM_BUG_ON_PAGE(!PageLRU(page), page);
852 __ClearPageLRU(page);
853 del_page_from_lru_list(page, lruvec, page_off_lru(page));
854 }
855
856 /* Clear Active bit in case of parallel mark_page_accessed */
857 ClearPageActive(page);
858
859 list_add(&page->lru, &pages_to_free);
860 }
861 if (zone)
862 spin_unlock_irqrestore(&zone->lru_lock, flags);
863
864 free_hot_cold_page_list(&pages_to_free, cold);
865}
866EXPORT_SYMBOL(release_pages);
867
868/*
869 * The pages which we're about to release may be in the deferred lru-addition
870 * queues. That would prevent them from really being freed right now. That's
871 * OK from a correctness point of view but is inefficient - those pages may be
872 * cache-warm and we want to give them back to the page allocator ASAP.
873 *
874 * So __pagevec_release() will drain those queues here. __pagevec_lru_add()
875 * and __pagevec_lru_add_active() call release_pages() directly to avoid
876 * mutual recursion.
877 */
878void __pagevec_release(struct pagevec *pvec)
879{
880 lru_add_drain();
881 release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
882 pagevec_reinit(pvec);
883}
884EXPORT_SYMBOL(__pagevec_release);
885
886#ifdef CONFIG_TRANSPARENT_HUGEPAGE
887/* used by __split_huge_page_refcount() */
888void lru_add_page_tail(struct page *page, struct page *page_tail,
889 struct lruvec *lruvec, struct list_head *list)
890{
891 const int file = 0;
892
893 VM_BUG_ON_PAGE(!PageHead(page), page);
894 VM_BUG_ON_PAGE(PageCompound(page_tail), page);
895 VM_BUG_ON_PAGE(PageLRU(page_tail), page);
896 VM_BUG_ON(NR_CPUS != 1 &&
897 !spin_is_locked(&lruvec_zone(lruvec)->lru_lock));
898
899 if (!list)
900 SetPageLRU(page_tail);
901
902 if (likely(PageLRU(page)))
903 list_add_tail(&page_tail->lru, &page->lru);
904 else if (list) {
905 /* page reclaim is reclaiming a huge page */
906 get_page(page_tail);
907 list_add_tail(&page_tail->lru, list);
908 } else {
909 struct list_head *list_head;
910 /*
911 * Head page has not yet been counted, as an hpage,
912 * so we must account for each subpage individually.
913 *
914 * Use the standard add function to put page_tail on the list,
915 * but then correct its position so they all end up in order.
916 */
917 add_page_to_lru_list(page_tail, lruvec, page_lru(page_tail));
918 list_head = page_tail->lru.prev;
919 list_move_tail(&page_tail->lru, list_head);
920 }
921
922 if (!PageUnevictable(page))
923 update_page_reclaim_stat(lruvec, file, PageActive(page_tail));
924}
925#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
926
927static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec,
928 void *arg)
929{
930 int file = page_is_file_cache(page);
931 int active = PageActive(page);
932 enum lru_list lru = page_lru(page);
933
934 VM_BUG_ON_PAGE(PageLRU(page), page);
935
936 SetPageLRU(page);
937 add_page_to_lru_list(page, lruvec, lru);
938 update_page_reclaim_stat(lruvec, file, active);
939 trace_mm_lru_insertion(page, page_to_pfn(page), lru, trace_pagemap_flags(page));
940}
941
942/*
943 * Add the passed pages to the LRU, then drop the caller's refcount
944 * on them. Reinitialises the caller's pagevec.
945 */
946void __pagevec_lru_add(struct pagevec *pvec)
947{
948 pagevec_lru_move_fn(pvec, __pagevec_lru_add_fn, NULL);
949}
950EXPORT_SYMBOL(__pagevec_lru_add);
951
952/**
953 * pagevec_lookup_entries - gang pagecache lookup
954 * @pvec: Where the resulting entries are placed
955 * @mapping: The address_space to search
956 * @start: The starting entry index
957 * @nr_entries: The maximum number of entries
958 * @indices: The cache indices corresponding to the entries in @pvec
959 *
960 * pagevec_lookup_entries() will search for and return a group of up
961 * to @nr_entries pages and shadow entries in the mapping. All
962 * entries are placed in @pvec. pagevec_lookup_entries() takes a
963 * reference against actual pages in @pvec.
964 *
965 * The search returns a group of mapping-contiguous entries with
966 * ascending indexes. There may be holes in the indices due to
967 * not-present entries.
968 *
969 * pagevec_lookup_entries() returns the number of entries which were
970 * found.
971 */
972unsigned pagevec_lookup_entries(struct pagevec *pvec,
973 struct address_space *mapping,
974 pgoff_t start, unsigned nr_pages,
975 pgoff_t *indices)
976{
977 pvec->nr = find_get_entries(mapping, start, nr_pages,
978 pvec->pages, indices);
979 return pagevec_count(pvec);
980}
981
982/**
983 * pagevec_remove_exceptionals - pagevec exceptionals pruning
984 * @pvec: The pagevec to prune
985 *
986 * pagevec_lookup_entries() fills both pages and exceptional radix
987 * tree entries into the pagevec. This function prunes all
988 * exceptionals from @pvec without leaving holes, so that it can be
989 * passed on to page-only pagevec operations.
990 */
991void pagevec_remove_exceptionals(struct pagevec *pvec)
992{
993 int i, j;
994
995 for (i = 0, j = 0; i < pagevec_count(pvec); i++) {
996 struct page *page = pvec->pages[i];
997 if (!radix_tree_exceptional_entry(page))
998 pvec->pages[j++] = page;
999 }
1000 pvec->nr = j;
1001}
1002
1003/**
1004 * pagevec_lookup - gang pagecache lookup
1005 * @pvec: Where the resulting pages are placed
1006 * @mapping: The address_space to search
1007 * @start: The starting page index
1008 * @nr_pages: The maximum number of pages
1009 *
1010 * pagevec_lookup() will search for and return a group of up to @nr_pages pages
1011 * in the mapping. The pages are placed in @pvec. pagevec_lookup() takes a
1012 * reference against the pages in @pvec.
1013 *
1014 * The search returns a group of mapping-contiguous pages with ascending
1015 * indexes. There may be holes in the indices due to not-present pages.
1016 *
1017 * pagevec_lookup() returns the number of pages which were found.
1018 */
1019unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
1020 pgoff_t start, unsigned nr_pages)
1021{
1022 pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
1023 return pagevec_count(pvec);
1024}
1025EXPORT_SYMBOL(pagevec_lookup);
1026
1027unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping,
1028 pgoff_t *index, int tag, unsigned nr_pages)
1029{
1030 pvec->nr = find_get_pages_tag(mapping, index, tag,
1031 nr_pages, pvec->pages);
1032 return pagevec_count(pvec);
1033}
1034EXPORT_SYMBOL(pagevec_lookup_tag);
1035
1036/*
1037 * Perform any setup for the swap system
1038 */
1039void __init swap_setup(void)
1040{
1041 unsigned long megs = totalram_pages >> (20 - PAGE_SHIFT);
1042#ifdef CONFIG_SWAP
1043 int i;
1044
1045 if (bdi_init(swapper_spaces[0].backing_dev_info))
1046 panic("Failed to init swap bdi");
1047 for (i = 0; i < MAX_SWAPFILES; i++) {
1048 spin_lock_init(&swapper_spaces[i].tree_lock);
1049 INIT_LIST_HEAD(&swapper_spaces[i].i_mmap_nonlinear);
1050 }
1051#endif
1052
1053 /* Use a smaller cluster for small-memory machines */
1054 if (megs < 16)
1055 page_cluster = 2;
1056 else
1057 page_cluster = 3;
1058 /*
1059 * Right now other parts of the system means that we
1060 * _really_ don't want to cluster much more
1061 */
1062}