1 // SPDX-License-Identifier: GPL-2.0-only
5 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
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.
13 * Swap aging added 23.2.95, Stephen Tweedie.
14 * Buffermem limits added 12.3.98, Rik van Riel.
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 #include <linux/local_lock.h>
42 #define CREATE_TRACE_POINTS
43 #include <trace/events/pagemap.h>
45 /* How many pages do we try to swap or page in/out together? */
48 /* Protecting only lru_rotate.pvec which requires disabling interrupts */
53 static DEFINE_PER_CPU(struct lru_rotate
, lru_rotate
) = {
54 .lock
= INIT_LOCAL_LOCK(lock
),
58 * The following struct pagevec are grouped together because they are protected
59 * by disabling preemption (and interrupts remain enabled).
63 struct pagevec lru_add
;
64 struct pagevec lru_deactivate_file
;
65 struct pagevec lru_deactivate
;
66 struct pagevec lru_lazyfree
;
68 struct pagevec activate_page
;
71 static DEFINE_PER_CPU(struct lru_pvecs
, lru_pvecs
) = {
72 .lock
= INIT_LOCAL_LOCK(lock
),
76 * This path almost never happens for VM activity - pages are normally
77 * freed via pagevecs. But it gets used by networking.
79 static void __page_cache_release(struct page
*page
)
82 struct lruvec
*lruvec
;
85 lruvec
= lock_page_lruvec_irqsave(page
, &flags
);
86 del_page_from_lru_list(page
, lruvec
);
87 __clear_page_lru_flags(page
);
88 unlock_page_lruvec_irqrestore(lruvec
, flags
);
90 __ClearPageWaiters(page
);
93 static void __put_single_page(struct page
*page
)
95 __page_cache_release(page
);
96 mem_cgroup_uncharge(page
);
97 free_unref_page(page
);
100 static void __put_compound_page(struct page
*page
)
103 * __page_cache_release() is supposed to be called for thp, not for
104 * hugetlb. This is because hugetlb page does never have PageLRU set
105 * (it's never listed to any LRU lists) and no memcg routines should
106 * be called for hugetlb (it has a separate hugetlb_cgroup.)
109 __page_cache_release(page
);
110 destroy_compound_page(page
);
113 void __put_page(struct page
*page
)
115 if (is_zone_device_page(page
)) {
116 put_dev_pagemap(page
->pgmap
);
119 * The page belongs to the device that created pgmap. Do
120 * not return it to page allocator.
125 if (unlikely(PageCompound(page
)))
126 __put_compound_page(page
);
128 __put_single_page(page
);
130 EXPORT_SYMBOL(__put_page
);
133 * put_pages_list() - release a list of pages
134 * @pages: list of pages threaded on page->lru
136 * Release a list of pages which are strung together on page.lru. Currently
137 * used by read_cache_pages() and related error recovery code.
139 void put_pages_list(struct list_head
*pages
)
141 while (!list_empty(pages
)) {
144 victim
= lru_to_page(pages
);
145 list_del(&victim
->lru
);
149 EXPORT_SYMBOL(put_pages_list
);
152 * get_kernel_pages() - pin kernel pages in memory
153 * @kiov: An array of struct kvec structures
154 * @nr_segs: number of segments to pin
155 * @write: pinning for read/write, currently ignored
156 * @pages: array that receives pointers to the pages pinned.
157 * Should be at least nr_segs long.
159 * Returns number of pages pinned. This may be fewer than the number
160 * requested. If nr_pages is 0 or negative, returns 0. If no pages
161 * were pinned, returns -errno. Each page returned must be released
162 * with a put_page() call when it is finished with.
164 int get_kernel_pages(const struct kvec
*kiov
, int nr_segs
, int write
,
169 for (seg
= 0; seg
< nr_segs
; seg
++) {
170 if (WARN_ON(kiov
[seg
].iov_len
!= PAGE_SIZE
))
173 pages
[seg
] = kmap_to_page(kiov
[seg
].iov_base
);
174 get_page(pages
[seg
]);
179 EXPORT_SYMBOL_GPL(get_kernel_pages
);
182 * get_kernel_page() - pin a kernel page in memory
183 * @start: starting kernel address
184 * @write: pinning for read/write, currently ignored
185 * @pages: array that receives pointer to the page pinned.
186 * Must be at least nr_segs long.
188 * Returns 1 if page is pinned. If the page was not pinned, returns
189 * -errno. The page returned must be released with a put_page() call
190 * when it is finished with.
192 int get_kernel_page(unsigned long start
, int write
, struct page
**pages
)
194 const struct kvec kiov
= {
195 .iov_base
= (void *)start
,
199 return get_kernel_pages(&kiov
, 1, write
, pages
);
201 EXPORT_SYMBOL_GPL(get_kernel_page
);
203 static void pagevec_lru_move_fn(struct pagevec
*pvec
,
204 void (*move_fn
)(struct page
*page
, struct lruvec
*lruvec
))
207 struct lruvec
*lruvec
= NULL
;
208 unsigned long flags
= 0;
210 for (i
= 0; i
< pagevec_count(pvec
); i
++) {
211 struct page
*page
= pvec
->pages
[i
];
213 /* block memcg migration during page moving between lru */
214 if (!TestClearPageLRU(page
))
217 lruvec
= relock_page_lruvec_irqsave(page
, lruvec
, &flags
);
218 (*move_fn
)(page
, lruvec
);
223 unlock_page_lruvec_irqrestore(lruvec
, flags
);
224 release_pages(pvec
->pages
, pvec
->nr
);
225 pagevec_reinit(pvec
);
228 static void pagevec_move_tail_fn(struct page
*page
, struct lruvec
*lruvec
)
230 if (!PageUnevictable(page
)) {
231 del_page_from_lru_list(page
, lruvec
);
232 ClearPageActive(page
);
233 add_page_to_lru_list_tail(page
, lruvec
);
234 __count_vm_events(PGROTATED
, thp_nr_pages(page
));
239 * Writeback is about to end against a page which has been marked for immediate
240 * reclaim. If it still appears to be reclaimable, move it to the tail of the
243 * rotate_reclaimable_page() must disable IRQs, to prevent nasty races.
245 void rotate_reclaimable_page(struct page
*page
)
247 if (!PageLocked(page
) && !PageDirty(page
) &&
248 !PageUnevictable(page
) && PageLRU(page
)) {
249 struct pagevec
*pvec
;
253 local_lock_irqsave(&lru_rotate
.lock
, flags
);
254 pvec
= this_cpu_ptr(&lru_rotate
.pvec
);
255 if (!pagevec_add(pvec
, page
) || PageCompound(page
))
256 pagevec_lru_move_fn(pvec
, pagevec_move_tail_fn
);
257 local_unlock_irqrestore(&lru_rotate
.lock
, flags
);
261 void lru_note_cost(struct lruvec
*lruvec
, bool file
, unsigned int nr_pages
)
264 unsigned long lrusize
;
267 * Hold lruvec->lru_lock is safe here, since
268 * 1) The pinned lruvec in reclaim, or
269 * 2) From a pre-LRU page during refault (which also holds the
270 * rcu lock, so would be safe even if the page was on the LRU
271 * and could move simultaneously to a new lruvec).
273 spin_lock_irq(&lruvec
->lru_lock
);
274 /* Record cost event */
276 lruvec
->file_cost
+= nr_pages
;
278 lruvec
->anon_cost
+= nr_pages
;
281 * Decay previous events
283 * Because workloads change over time (and to avoid
284 * overflow) we keep these statistics as a floating
285 * average, which ends up weighing recent refaults
286 * more than old ones.
288 lrusize
= lruvec_page_state(lruvec
, NR_INACTIVE_ANON
) +
289 lruvec_page_state(lruvec
, NR_ACTIVE_ANON
) +
290 lruvec_page_state(lruvec
, NR_INACTIVE_FILE
) +
291 lruvec_page_state(lruvec
, NR_ACTIVE_FILE
);
293 if (lruvec
->file_cost
+ lruvec
->anon_cost
> lrusize
/ 4) {
294 lruvec
->file_cost
/= 2;
295 lruvec
->anon_cost
/= 2;
297 spin_unlock_irq(&lruvec
->lru_lock
);
298 } while ((lruvec
= parent_lruvec(lruvec
)));
301 void lru_note_cost_page(struct page
*page
)
303 lru_note_cost(mem_cgroup_page_lruvec(page
, page_pgdat(page
)),
304 page_is_file_lru(page
), thp_nr_pages(page
));
307 static void __activate_page(struct page
*page
, struct lruvec
*lruvec
)
309 if (!PageActive(page
) && !PageUnevictable(page
)) {
310 int nr_pages
= thp_nr_pages(page
);
312 del_page_from_lru_list(page
, lruvec
);
314 add_page_to_lru_list(page
, lruvec
);
315 trace_mm_lru_activate(page
);
317 __count_vm_events(PGACTIVATE
, nr_pages
);
318 __count_memcg_events(lruvec_memcg(lruvec
), PGACTIVATE
,
324 static void activate_page_drain(int cpu
)
326 struct pagevec
*pvec
= &per_cpu(lru_pvecs
.activate_page
, cpu
);
328 if (pagevec_count(pvec
))
329 pagevec_lru_move_fn(pvec
, __activate_page
);
332 static bool need_activate_page_drain(int cpu
)
334 return pagevec_count(&per_cpu(lru_pvecs
.activate_page
, cpu
)) != 0;
337 static void activate_page(struct page
*page
)
339 page
= compound_head(page
);
340 if (PageLRU(page
) && !PageActive(page
) && !PageUnevictable(page
)) {
341 struct pagevec
*pvec
;
343 local_lock(&lru_pvecs
.lock
);
344 pvec
= this_cpu_ptr(&lru_pvecs
.activate_page
);
346 if (!pagevec_add(pvec
, page
) || PageCompound(page
))
347 pagevec_lru_move_fn(pvec
, __activate_page
);
348 local_unlock(&lru_pvecs
.lock
);
353 static inline void activate_page_drain(int cpu
)
357 static void activate_page(struct page
*page
)
359 struct lruvec
*lruvec
;
361 page
= compound_head(page
);
362 if (TestClearPageLRU(page
)) {
363 lruvec
= lock_page_lruvec_irq(page
);
364 __activate_page(page
, lruvec
);
365 unlock_page_lruvec_irq(lruvec
);
371 static void __lru_cache_activate_page(struct page
*page
)
373 struct pagevec
*pvec
;
376 local_lock(&lru_pvecs
.lock
);
377 pvec
= this_cpu_ptr(&lru_pvecs
.lru_add
);
380 * Search backwards on the optimistic assumption that the page being
381 * activated has just been added to this pagevec. Note that only
382 * the local pagevec is examined as a !PageLRU page could be in the
383 * process of being released, reclaimed, migrated or on a remote
384 * pagevec that is currently being drained. Furthermore, marking
385 * a remote pagevec's page PageActive potentially hits a race where
386 * a page is marked PageActive just after it is added to the inactive
387 * list causing accounting errors and BUG_ON checks to trigger.
389 for (i
= pagevec_count(pvec
) - 1; i
>= 0; i
--) {
390 struct page
*pagevec_page
= pvec
->pages
[i
];
392 if (pagevec_page
== page
) {
398 local_unlock(&lru_pvecs
.lock
);
402 * Mark a page as having seen activity.
404 * inactive,unreferenced -> inactive,referenced
405 * inactive,referenced -> active,unreferenced
406 * active,unreferenced -> active,referenced
408 * When a newly allocated page is not yet visible, so safe for non-atomic ops,
409 * __SetPageReferenced(page) may be substituted for mark_page_accessed(page).
411 void mark_page_accessed(struct page
*page
)
413 page
= compound_head(page
);
415 if (!PageReferenced(page
)) {
416 SetPageReferenced(page
);
417 } else if (PageUnevictable(page
)) {
419 * Unevictable pages are on the "LRU_UNEVICTABLE" list. But,
420 * this list is never rotated or maintained, so marking an
421 * evictable page accessed has no effect.
423 } else if (!PageActive(page
)) {
425 * If the page is on the LRU, queue it for activation via
426 * lru_pvecs.activate_page. Otherwise, assume the page is on a
427 * pagevec, mark it active and it'll be moved to the active
428 * LRU on the next drain.
433 __lru_cache_activate_page(page
);
434 ClearPageReferenced(page
);
435 workingset_activation(page
);
437 if (page_is_idle(page
))
438 clear_page_idle(page
);
440 EXPORT_SYMBOL(mark_page_accessed
);
443 * lru_cache_add - add a page to a page list
444 * @page: the page to be added to the LRU.
446 * Queue the page for addition to the LRU via pagevec. The decision on whether
447 * to add the page to the [in]active [file|anon] list is deferred until the
448 * pagevec is drained. This gives a chance for the caller of lru_cache_add()
449 * have the page added to the active list using mark_page_accessed().
451 void lru_cache_add(struct page
*page
)
453 struct pagevec
*pvec
;
455 VM_BUG_ON_PAGE(PageActive(page
) && PageUnevictable(page
), page
);
456 VM_BUG_ON_PAGE(PageLRU(page
), page
);
459 local_lock(&lru_pvecs
.lock
);
460 pvec
= this_cpu_ptr(&lru_pvecs
.lru_add
);
461 if (!pagevec_add(pvec
, page
) || PageCompound(page
))
462 __pagevec_lru_add(pvec
);
463 local_unlock(&lru_pvecs
.lock
);
465 EXPORT_SYMBOL(lru_cache_add
);
468 * lru_cache_add_inactive_or_unevictable
469 * @page: the page to be added to LRU
470 * @vma: vma in which page is mapped for determining reclaimability
472 * Place @page on the inactive or unevictable LRU list, depending on its
475 void lru_cache_add_inactive_or_unevictable(struct page
*page
,
476 struct vm_area_struct
*vma
)
480 VM_BUG_ON_PAGE(PageLRU(page
), page
);
482 unevictable
= (vma
->vm_flags
& (VM_LOCKED
| VM_SPECIAL
)) == VM_LOCKED
;
483 if (unlikely(unevictable
) && !TestSetPageMlocked(page
)) {
484 int nr_pages
= thp_nr_pages(page
);
486 * We use the irq-unsafe __mod_zone_page_stat because this
487 * counter is not modified from interrupt context, and the pte
488 * lock is held(spinlock), which implies preemption disabled.
490 __mod_zone_page_state(page_zone(page
), NR_MLOCK
, nr_pages
);
491 count_vm_events(UNEVICTABLE_PGMLOCKED
, nr_pages
);
497 * If the page can not be invalidated, it is moved to the
498 * inactive list to speed up its reclaim. It is moved to the
499 * head of the list, rather than the tail, to give the flusher
500 * threads some time to write it out, as this is much more
501 * effective than the single-page writeout from reclaim.
503 * If the page isn't page_mapped and dirty/writeback, the page
504 * could reclaim asap using PG_reclaim.
506 * 1. active, mapped page -> none
507 * 2. active, dirty/writeback page -> inactive, head, PG_reclaim
508 * 3. inactive, mapped page -> none
509 * 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim
510 * 5. inactive, clean -> inactive, tail
513 * In 4, why it moves inactive's head, the VM expects the page would
514 * be write it out by flusher threads as this is much more effective
515 * than the single-page writeout from reclaim.
517 static void lru_deactivate_file_fn(struct page
*page
, struct lruvec
*lruvec
)
519 bool active
= PageActive(page
);
520 int nr_pages
= thp_nr_pages(page
);
522 if (PageUnevictable(page
))
525 /* Some processes are using the page */
526 if (page_mapped(page
))
529 del_page_from_lru_list(page
, lruvec
);
530 ClearPageActive(page
);
531 ClearPageReferenced(page
);
533 if (PageWriteback(page
) || PageDirty(page
)) {
535 * PG_reclaim could be raced with end_page_writeback
536 * It can make readahead confusing. But race window
537 * is _really_ small and it's non-critical problem.
539 add_page_to_lru_list(page
, lruvec
);
540 SetPageReclaim(page
);
543 * The page's writeback ends up during pagevec
544 * We moves tha page into tail of inactive.
546 add_page_to_lru_list_tail(page
, lruvec
);
547 __count_vm_events(PGROTATED
, nr_pages
);
551 __count_vm_events(PGDEACTIVATE
, nr_pages
);
552 __count_memcg_events(lruvec_memcg(lruvec
), PGDEACTIVATE
,
557 static void lru_deactivate_fn(struct page
*page
, struct lruvec
*lruvec
)
559 if (PageActive(page
) && !PageUnevictable(page
)) {
560 int nr_pages
= thp_nr_pages(page
);
562 del_page_from_lru_list(page
, lruvec
);
563 ClearPageActive(page
);
564 ClearPageReferenced(page
);
565 add_page_to_lru_list(page
, lruvec
);
567 __count_vm_events(PGDEACTIVATE
, nr_pages
);
568 __count_memcg_events(lruvec_memcg(lruvec
), PGDEACTIVATE
,
573 static void lru_lazyfree_fn(struct page
*page
, struct lruvec
*lruvec
)
575 if (PageAnon(page
) && PageSwapBacked(page
) &&
576 !PageSwapCache(page
) && !PageUnevictable(page
)) {
577 int nr_pages
= thp_nr_pages(page
);
579 del_page_from_lru_list(page
, lruvec
);
580 ClearPageActive(page
);
581 ClearPageReferenced(page
);
583 * Lazyfree pages are clean anonymous pages. They have
584 * PG_swapbacked flag cleared, to distinguish them from normal
587 ClearPageSwapBacked(page
);
588 add_page_to_lru_list(page
, lruvec
);
590 __count_vm_events(PGLAZYFREE
, nr_pages
);
591 __count_memcg_events(lruvec_memcg(lruvec
), PGLAZYFREE
,
597 * Drain pages out of the cpu's pagevecs.
598 * Either "cpu" is the current CPU, and preemption has already been
599 * disabled; or "cpu" is being hot-unplugged, and is already dead.
601 void lru_add_drain_cpu(int cpu
)
603 struct pagevec
*pvec
= &per_cpu(lru_pvecs
.lru_add
, cpu
);
605 if (pagevec_count(pvec
))
606 __pagevec_lru_add(pvec
);
608 pvec
= &per_cpu(lru_rotate
.pvec
, cpu
);
609 /* Disabling interrupts below acts as a compiler barrier. */
610 if (data_race(pagevec_count(pvec
))) {
613 /* No harm done if a racing interrupt already did this */
614 local_lock_irqsave(&lru_rotate
.lock
, flags
);
615 pagevec_lru_move_fn(pvec
, pagevec_move_tail_fn
);
616 local_unlock_irqrestore(&lru_rotate
.lock
, flags
);
619 pvec
= &per_cpu(lru_pvecs
.lru_deactivate_file
, cpu
);
620 if (pagevec_count(pvec
))
621 pagevec_lru_move_fn(pvec
, lru_deactivate_file_fn
);
623 pvec
= &per_cpu(lru_pvecs
.lru_deactivate
, cpu
);
624 if (pagevec_count(pvec
))
625 pagevec_lru_move_fn(pvec
, lru_deactivate_fn
);
627 pvec
= &per_cpu(lru_pvecs
.lru_lazyfree
, cpu
);
628 if (pagevec_count(pvec
))
629 pagevec_lru_move_fn(pvec
, lru_lazyfree_fn
);
631 activate_page_drain(cpu
);
635 * deactivate_file_page - forcefully deactivate a file page
636 * @page: page to deactivate
638 * This function hints the VM that @page is a good reclaim candidate,
639 * for example if its invalidation fails due to the page being dirty
640 * or under writeback.
642 void deactivate_file_page(struct page
*page
)
645 * In a workload with many unevictable page such as mprotect,
646 * unevictable page deactivation for accelerating reclaim is pointless.
648 if (PageUnevictable(page
))
651 if (likely(get_page_unless_zero(page
))) {
652 struct pagevec
*pvec
;
654 local_lock(&lru_pvecs
.lock
);
655 pvec
= this_cpu_ptr(&lru_pvecs
.lru_deactivate_file
);
657 if (!pagevec_add(pvec
, page
) || PageCompound(page
))
658 pagevec_lru_move_fn(pvec
, lru_deactivate_file_fn
);
659 local_unlock(&lru_pvecs
.lock
);
664 * deactivate_page - deactivate a page
665 * @page: page to deactivate
667 * deactivate_page() moves @page to the inactive list if @page was on the active
668 * list and was not an unevictable page. This is done to accelerate the reclaim
671 void deactivate_page(struct page
*page
)
673 if (PageLRU(page
) && PageActive(page
) && !PageUnevictable(page
)) {
674 struct pagevec
*pvec
;
676 local_lock(&lru_pvecs
.lock
);
677 pvec
= this_cpu_ptr(&lru_pvecs
.lru_deactivate
);
679 if (!pagevec_add(pvec
, page
) || PageCompound(page
))
680 pagevec_lru_move_fn(pvec
, lru_deactivate_fn
);
681 local_unlock(&lru_pvecs
.lock
);
686 * mark_page_lazyfree - make an anon page lazyfree
687 * @page: page to deactivate
689 * mark_page_lazyfree() moves @page to the inactive file list.
690 * This is done to accelerate the reclaim of @page.
692 void mark_page_lazyfree(struct page
*page
)
694 if (PageLRU(page
) && PageAnon(page
) && PageSwapBacked(page
) &&
695 !PageSwapCache(page
) && !PageUnevictable(page
)) {
696 struct pagevec
*pvec
;
698 local_lock(&lru_pvecs
.lock
);
699 pvec
= this_cpu_ptr(&lru_pvecs
.lru_lazyfree
);
701 if (!pagevec_add(pvec
, page
) || PageCompound(page
))
702 pagevec_lru_move_fn(pvec
, lru_lazyfree_fn
);
703 local_unlock(&lru_pvecs
.lock
);
707 void lru_add_drain(void)
709 local_lock(&lru_pvecs
.lock
);
710 lru_add_drain_cpu(smp_processor_id());
711 local_unlock(&lru_pvecs
.lock
);
714 void lru_add_drain_cpu_zone(struct zone
*zone
)
716 local_lock(&lru_pvecs
.lock
);
717 lru_add_drain_cpu(smp_processor_id());
718 drain_local_pages(zone
);
719 local_unlock(&lru_pvecs
.lock
);
724 static DEFINE_PER_CPU(struct work_struct
, lru_add_drain_work
);
726 static void lru_add_drain_per_cpu(struct work_struct
*dummy
)
732 * Doesn't need any cpu hotplug locking because we do rely on per-cpu
733 * kworkers being shut down before our page_alloc_cpu_dead callback is
734 * executed on the offlined cpu.
735 * Calling this function with cpu hotplug locks held can actually lead
736 * to obscure indirect dependencies via WQ context.
738 void lru_add_drain_all(void)
741 * lru_drain_gen - Global pages generation number
743 * (A) Definition: global lru_drain_gen = x implies that all generations
744 * 0 < n <= x are already *scheduled* for draining.
746 * This is an optimization for the highly-contended use case where a
747 * user space workload keeps constantly generating a flow of pages for
750 static unsigned int lru_drain_gen
;
751 static struct cpumask has_work
;
752 static DEFINE_MUTEX(lock
);
753 unsigned cpu
, this_gen
;
756 * Make sure nobody triggers this path before mm_percpu_wq is fully
759 if (WARN_ON(!mm_percpu_wq
))
763 * Guarantee pagevec counter stores visible by this CPU are visible to
764 * other CPUs before loading the current drain generation.
769 * (B) Locally cache global LRU draining generation number
771 * The read barrier ensures that the counter is loaded before the mutex
772 * is taken. It pairs with smp_mb() inside the mutex critical section
775 this_gen
= smp_load_acquire(&lru_drain_gen
);
780 * (C) Exit the draining operation if a newer generation, from another
781 * lru_add_drain_all(), was already scheduled for draining. Check (A).
783 if (unlikely(this_gen
!= lru_drain_gen
))
787 * (D) Increment global generation number
789 * Pairs with smp_load_acquire() at (B), outside of the critical
790 * section. Use a full memory barrier to guarantee that the new global
791 * drain generation number is stored before loading pagevec counters.
793 * This pairing must be done here, before the for_each_online_cpu loop
794 * below which drains the page vectors.
796 * Let x, y, and z represent some system CPU numbers, where x < y < z.
797 * Assume CPU #z is is in the middle of the for_each_online_cpu loop
798 * below and has already reached CPU #y's per-cpu data. CPU #x comes
799 * along, adds some pages to its per-cpu vectors, then calls
800 * lru_add_drain_all().
802 * If the paired barrier is done at any later step, e.g. after the
803 * loop, CPU #x will just exit at (C) and miss flushing out all of its
806 WRITE_ONCE(lru_drain_gen
, lru_drain_gen
+ 1);
809 cpumask_clear(&has_work
);
810 for_each_online_cpu(cpu
) {
811 struct work_struct
*work
= &per_cpu(lru_add_drain_work
, cpu
);
813 if (pagevec_count(&per_cpu(lru_pvecs
.lru_add
, cpu
)) ||
814 data_race(pagevec_count(&per_cpu(lru_rotate
.pvec
, cpu
))) ||
815 pagevec_count(&per_cpu(lru_pvecs
.lru_deactivate_file
, cpu
)) ||
816 pagevec_count(&per_cpu(lru_pvecs
.lru_deactivate
, cpu
)) ||
817 pagevec_count(&per_cpu(lru_pvecs
.lru_lazyfree
, cpu
)) ||
818 need_activate_page_drain(cpu
)) {
819 INIT_WORK(work
, lru_add_drain_per_cpu
);
820 queue_work_on(cpu
, mm_percpu_wq
, work
);
821 __cpumask_set_cpu(cpu
, &has_work
);
825 for_each_cpu(cpu
, &has_work
)
826 flush_work(&per_cpu(lru_add_drain_work
, cpu
));
832 void lru_add_drain_all(void)
836 #endif /* CONFIG_SMP */
839 * release_pages - batched put_page()
840 * @pages: array of pages to release
841 * @nr: number of pages
843 * Decrement the reference count on all the pages in @pages. If it
844 * fell to zero, remove the page from the LRU and free it.
846 void release_pages(struct page
**pages
, int nr
)
849 LIST_HEAD(pages_to_free
);
850 struct lruvec
*lruvec
= NULL
;
852 unsigned int lock_batch
;
854 for (i
= 0; i
< nr
; i
++) {
855 struct page
*page
= pages
[i
];
858 * Make sure the IRQ-safe lock-holding time does not get
859 * excessive with a continuous string of pages from the
860 * same lruvec. The lock is held only if lruvec != NULL.
862 if (lruvec
&& ++lock_batch
== SWAP_CLUSTER_MAX
) {
863 unlock_page_lruvec_irqrestore(lruvec
, flags
);
867 page
= compound_head(page
);
868 if (is_huge_zero_page(page
))
871 if (is_zone_device_page(page
)) {
873 unlock_page_lruvec_irqrestore(lruvec
, flags
);
877 * ZONE_DEVICE pages that return 'false' from
878 * page_is_devmap_managed() do not require special
879 * processing, and instead, expect a call to
880 * put_page_testzero().
882 if (page_is_devmap_managed(page
)) {
883 put_devmap_managed_page(page
);
886 if (put_page_testzero(page
))
887 put_dev_pagemap(page
->pgmap
);
891 if (!put_page_testzero(page
))
894 if (PageCompound(page
)) {
896 unlock_page_lruvec_irqrestore(lruvec
, flags
);
899 __put_compound_page(page
);
904 struct lruvec
*prev_lruvec
= lruvec
;
906 lruvec
= relock_page_lruvec_irqsave(page
, lruvec
,
908 if (prev_lruvec
!= lruvec
)
911 del_page_from_lru_list(page
, lruvec
);
912 __clear_page_lru_flags(page
);
915 __ClearPageWaiters(page
);
917 list_add(&page
->lru
, &pages_to_free
);
920 unlock_page_lruvec_irqrestore(lruvec
, flags
);
922 mem_cgroup_uncharge_list(&pages_to_free
);
923 free_unref_page_list(&pages_to_free
);
925 EXPORT_SYMBOL(release_pages
);
928 * The pages which we're about to release may be in the deferred lru-addition
929 * queues. That would prevent them from really being freed right now. That's
930 * OK from a correctness point of view but is inefficient - those pages may be
931 * cache-warm and we want to give them back to the page allocator ASAP.
933 * So __pagevec_release() will drain those queues here. __pagevec_lru_add()
934 * and __pagevec_lru_add_active() call release_pages() directly to avoid
937 void __pagevec_release(struct pagevec
*pvec
)
939 if (!pvec
->percpu_pvec_drained
) {
941 pvec
->percpu_pvec_drained
= true;
943 release_pages(pvec
->pages
, pagevec_count(pvec
));
944 pagevec_reinit(pvec
);
946 EXPORT_SYMBOL(__pagevec_release
);
948 static void __pagevec_lru_add_fn(struct page
*page
, struct lruvec
*lruvec
)
950 int was_unevictable
= TestClearPageUnevictable(page
);
951 int nr_pages
= thp_nr_pages(page
);
953 VM_BUG_ON_PAGE(PageLRU(page
), page
);
956 * Page becomes evictable in two ways:
957 * 1) Within LRU lock [munlock_vma_page() and __munlock_pagevec()].
958 * 2) Before acquiring LRU lock to put the page to correct LRU and then
959 * a) do PageLRU check with lock [check_move_unevictable_pages]
960 * b) do PageLRU check before lock [clear_page_mlock]
962 * (1) & (2a) are ok as LRU lock will serialize them. For (2b), we need
963 * following strict ordering:
965 * #0: __pagevec_lru_add_fn #1: clear_page_mlock
967 * SetPageLRU() TestClearPageMlocked()
968 * smp_mb() // explicit ordering // above provides strict
970 * PageMlocked() PageLRU()
973 * if '#1' does not observe setting of PG_lru by '#0' and fails
974 * isolation, the explicit barrier will make sure that page_evictable
975 * check will put the page in correct LRU. Without smp_mb(), SetPageLRU
976 * can be reordered after PageMlocked check and can make '#1' to fail
977 * the isolation of the page whose Mlocked bit is cleared (#0 is also
978 * looking at the same page) and the evictable page will be stranded
979 * in an unevictable LRU.
982 smp_mb__after_atomic();
984 if (page_evictable(page
)) {
986 __count_vm_events(UNEVICTABLE_PGRESCUED
, nr_pages
);
988 ClearPageActive(page
);
989 SetPageUnevictable(page
);
990 if (!was_unevictable
)
991 __count_vm_events(UNEVICTABLE_PGCULLED
, nr_pages
);
994 add_page_to_lru_list(page
, lruvec
);
995 trace_mm_lru_insertion(page
);
999 * Add the passed pages to the LRU, then drop the caller's refcount
1000 * on them. Reinitialises the caller's pagevec.
1002 void __pagevec_lru_add(struct pagevec
*pvec
)
1005 struct lruvec
*lruvec
= NULL
;
1006 unsigned long flags
= 0;
1008 for (i
= 0; i
< pagevec_count(pvec
); i
++) {
1009 struct page
*page
= pvec
->pages
[i
];
1011 lruvec
= relock_page_lruvec_irqsave(page
, lruvec
, &flags
);
1012 __pagevec_lru_add_fn(page
, lruvec
);
1015 unlock_page_lruvec_irqrestore(lruvec
, flags
);
1016 release_pages(pvec
->pages
, pvec
->nr
);
1017 pagevec_reinit(pvec
);
1021 * pagevec_remove_exceptionals - pagevec exceptionals pruning
1022 * @pvec: The pagevec to prune
1024 * find_get_entries() fills both pages and XArray value entries (aka
1025 * exceptional entries) into the pagevec. This function prunes all
1026 * exceptionals from @pvec without leaving holes, so that it can be
1027 * passed on to page-only pagevec operations.
1029 void pagevec_remove_exceptionals(struct pagevec
*pvec
)
1033 for (i
= 0, j
= 0; i
< pagevec_count(pvec
); i
++) {
1034 struct page
*page
= pvec
->pages
[i
];
1035 if (!xa_is_value(page
))
1036 pvec
->pages
[j
++] = page
;
1042 * pagevec_lookup_range - gang pagecache lookup
1043 * @pvec: Where the resulting pages are placed
1044 * @mapping: The address_space to search
1045 * @start: The starting page index
1046 * @end: The final page index
1048 * pagevec_lookup_range() will search for & return a group of up to PAGEVEC_SIZE
1049 * pages in the mapping starting from index @start and upto index @end
1050 * (inclusive). The pages are placed in @pvec. pagevec_lookup() takes a
1051 * reference against the pages in @pvec.
1053 * The search returns a group of mapping-contiguous pages with ascending
1054 * indexes. There may be holes in the indices due to not-present pages. We
1055 * also update @start to index the next page for the traversal.
1057 * pagevec_lookup_range() returns the number of pages which were found. If this
1058 * number is smaller than PAGEVEC_SIZE, the end of specified range has been
1061 unsigned pagevec_lookup_range(struct pagevec
*pvec
,
1062 struct address_space
*mapping
, pgoff_t
*start
, pgoff_t end
)
1064 pvec
->nr
= find_get_pages_range(mapping
, start
, end
, PAGEVEC_SIZE
,
1066 return pagevec_count(pvec
);
1068 EXPORT_SYMBOL(pagevec_lookup_range
);
1070 unsigned pagevec_lookup_range_tag(struct pagevec
*pvec
,
1071 struct address_space
*mapping
, pgoff_t
*index
, pgoff_t end
,
1074 pvec
->nr
= find_get_pages_range_tag(mapping
, index
, end
, tag
,
1075 PAGEVEC_SIZE
, pvec
->pages
);
1076 return pagevec_count(pvec
);
1078 EXPORT_SYMBOL(pagevec_lookup_range_tag
);
1081 * Perform any setup for the swap system
1083 void __init
swap_setup(void)
1085 unsigned long megs
= totalram_pages() >> (20 - PAGE_SHIFT
);
1087 /* Use a smaller cluster for small-memory machines */
1093 * Right now other parts of the system means that we
1094 * _really_ don't want to cluster much more
1098 #ifdef CONFIG_DEV_PAGEMAP_OPS
1099 void put_devmap_managed_page(struct page
*page
)
1103 if (WARN_ON_ONCE(!page_is_devmap_managed(page
)))
1106 count
= page_ref_dec_return(page
);
1109 * devmap page refcounts are 1-based, rather than 0-based: if
1110 * refcount is 1, then the page is free and the refcount is
1111 * stable because nobody holds a reference on the page.
1114 free_devmap_managed_page(page
);
1118 EXPORT_SYMBOL(put_devmap_managed_page
);