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#include <linux/local_lock.h>
39#include <linux/buffer_head.h>
40
41#include "internal.h"
42
43#define CREATE_TRACE_POINTS
44#include <trace/events/pagemap.h>
45
46/* How many pages do we try to swap or page in/out together? As a power of 2 */
47int page_cluster;
48const int page_cluster_max = 31;
49
50/* Protecting only lru_rotate.fbatch which requires disabling interrupts */
51struct lru_rotate {
52 local_lock_t lock;
53 struct folio_batch fbatch;
54};
55static DEFINE_PER_CPU(struct lru_rotate, lru_rotate) = {
56 .lock = INIT_LOCAL_LOCK(lock),
57};
58
59/*
60 * The following folio batches are grouped together because they are protected
61 * by disabling preemption (and interrupts remain enabled).
62 */
63struct cpu_fbatches {
64 local_lock_t lock;
65 struct folio_batch lru_add;
66 struct folio_batch lru_deactivate_file;
67 struct folio_batch lru_deactivate;
68 struct folio_batch lru_lazyfree;
69#ifdef CONFIG_SMP
70 struct folio_batch activate;
71#endif
72};
73static DEFINE_PER_CPU(struct cpu_fbatches, cpu_fbatches) = {
74 .lock = INIT_LOCAL_LOCK(lock),
75};
76
77/*
78 * This path almost never happens for VM activity - pages are normally freed
79 * in batches. But it gets used by networking - and for compound pages.
80 */
81static void __page_cache_release(struct folio *folio)
82{
83 if (folio_test_lru(folio)) {
84 struct lruvec *lruvec;
85 unsigned long flags;
86
87 lruvec = folio_lruvec_lock_irqsave(folio, flags: &flags);
88 lruvec_del_folio(lruvec, folio);
89 __folio_clear_lru_flags(folio);
90 unlock_page_lruvec_irqrestore(lruvec, flags);
91 }
92 /* See comment on folio_test_mlocked in release_pages() */
93 if (unlikely(folio_test_mlocked(folio))) {
94 long nr_pages = folio_nr_pages(folio);
95
96 __folio_clear_mlocked(folio);
97 zone_stat_mod_folio(folio, item: NR_MLOCK, nr: -nr_pages);
98 count_vm_events(item: UNEVICTABLE_PGCLEARED, delta: nr_pages);
99 }
100}
101
102static void __folio_put_small(struct folio *folio)
103{
104 __page_cache_release(folio);
105 mem_cgroup_uncharge(folio);
106 free_unref_page(page: &folio->page, order: 0);
107}
108
109static void __folio_put_large(struct folio *folio)
110{
111 /*
112 * __page_cache_release() is supposed to be called for thp, not for
113 * hugetlb. This is because hugetlb page does never have PageLRU set
114 * (it's never listed to any LRU lists) and no memcg routines should
115 * be called for hugetlb (it has a separate hugetlb_cgroup.)
116 */
117 if (!folio_test_hugetlb(folio))
118 __page_cache_release(folio);
119 destroy_large_folio(folio);
120}
121
122void __folio_put(struct folio *folio)
123{
124 if (unlikely(folio_is_zone_device(folio)))
125 free_zone_device_page(page: &folio->page);
126 else if (unlikely(folio_test_large(folio)))
127 __folio_put_large(folio);
128 else
129 __folio_put_small(folio);
130}
131EXPORT_SYMBOL(__folio_put);
132
133/**
134 * put_pages_list() - release a list of pages
135 * @pages: list of pages threaded on page->lru
136 *
137 * Release a list of pages which are strung together on page.lru.
138 */
139void put_pages_list(struct list_head *pages)
140{
141 struct folio *folio, *next;
142
143 list_for_each_entry_safe(folio, next, pages, lru) {
144 if (!folio_put_testzero(folio)) {
145 list_del(entry: &folio->lru);
146 continue;
147 }
148 if (folio_test_large(folio)) {
149 list_del(entry: &folio->lru);
150 __folio_put_large(folio);
151 continue;
152 }
153 /* LRU flag must be clear because it's passed using the lru */
154 }
155
156 free_unref_page_list(list: pages);
157 INIT_LIST_HEAD(list: pages);
158}
159EXPORT_SYMBOL(put_pages_list);
160
161typedef void (*move_fn_t)(struct lruvec *lruvec, struct folio *folio);
162
163static void lru_add_fn(struct lruvec *lruvec, struct folio *folio)
164{
165 int was_unevictable = folio_test_clear_unevictable(folio);
166 long nr_pages = folio_nr_pages(folio);
167
168 VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
169
170 /*
171 * Is an smp_mb__after_atomic() still required here, before
172 * folio_evictable() tests the mlocked flag, to rule out the possibility
173 * of stranding an evictable folio on an unevictable LRU? I think
174 * not, because __munlock_folio() only clears the mlocked flag
175 * while the LRU lock is held.
176 *
177 * (That is not true of __page_cache_release(), and not necessarily
178 * true of release_pages(): but those only clear the mlocked flag after
179 * folio_put_testzero() has excluded any other users of the folio.)
180 */
181 if (folio_evictable(folio)) {
182 if (was_unevictable)
183 __count_vm_events(item: UNEVICTABLE_PGRESCUED, delta: nr_pages);
184 } else {
185 folio_clear_active(folio);
186 folio_set_unevictable(folio);
187 /*
188 * folio->mlock_count = !!folio_test_mlocked(folio)?
189 * But that leaves __mlock_folio() in doubt whether another
190 * actor has already counted the mlock or not. Err on the
191 * safe side, underestimate, let page reclaim fix it, rather
192 * than leaving a page on the unevictable LRU indefinitely.
193 */
194 folio->mlock_count = 0;
195 if (!was_unevictable)
196 __count_vm_events(item: UNEVICTABLE_PGCULLED, delta: nr_pages);
197 }
198
199 lruvec_add_folio(lruvec, folio);
200 trace_mm_lru_insertion(folio);
201}
202
203static void folio_batch_move_lru(struct folio_batch *fbatch, move_fn_t move_fn)
204{
205 int i;
206 struct lruvec *lruvec = NULL;
207 unsigned long flags = 0;
208
209 for (i = 0; i < folio_batch_count(fbatch); i++) {
210 struct folio *folio = fbatch->folios[i];
211
212 /* block memcg migration while the folio moves between lru */
213 if (move_fn != lru_add_fn && !folio_test_clear_lru(folio))
214 continue;
215
216 lruvec = folio_lruvec_relock_irqsave(folio, locked_lruvec: lruvec, flags: &flags);
217 move_fn(lruvec, folio);
218
219 folio_set_lru(folio);
220 }
221
222 if (lruvec)
223 unlock_page_lruvec_irqrestore(lruvec, flags);
224 folios_put(folios: fbatch->folios, nr: folio_batch_count(fbatch));
225 folio_batch_reinit(fbatch);
226}
227
228static void folio_batch_add_and_move(struct folio_batch *fbatch,
229 struct folio *folio, move_fn_t move_fn)
230{
231 if (folio_batch_add(fbatch, folio) && !folio_test_large(folio) &&
232 !lru_cache_disabled())
233 return;
234 folio_batch_move_lru(fbatch, move_fn);
235}
236
237static void lru_move_tail_fn(struct lruvec *lruvec, struct folio *folio)
238{
239 if (!folio_test_unevictable(folio)) {
240 lruvec_del_folio(lruvec, folio);
241 folio_clear_active(folio);
242 lruvec_add_folio_tail(lruvec, folio);
243 __count_vm_events(item: PGROTATED, delta: folio_nr_pages(folio));
244 }
245}
246
247/*
248 * Writeback is about to end against a folio which has been marked for
249 * immediate reclaim. If it still appears to be reclaimable, move it
250 * to the tail of the inactive list.
251 *
252 * folio_rotate_reclaimable() must disable IRQs, to prevent nasty races.
253 */
254void folio_rotate_reclaimable(struct folio *folio)
255{
256 if (!folio_test_locked(folio) && !folio_test_dirty(folio) &&
257 !folio_test_unevictable(folio) && folio_test_lru(folio)) {
258 struct folio_batch *fbatch;
259 unsigned long flags;
260
261 folio_get(folio);
262 local_lock_irqsave(&lru_rotate.lock, flags);
263 fbatch = this_cpu_ptr(&lru_rotate.fbatch);
264 folio_batch_add_and_move(fbatch, folio, move_fn: lru_move_tail_fn);
265 local_unlock_irqrestore(&lru_rotate.lock, flags);
266 }
267}
268
269void lru_note_cost(struct lruvec *lruvec, bool file,
270 unsigned int nr_io, unsigned int nr_rotated)
271{
272 unsigned long cost;
273
274 /*
275 * Reflect the relative cost of incurring IO and spending CPU
276 * time on rotations. This doesn't attempt to make a precise
277 * comparison, it just says: if reloads are about comparable
278 * between the LRU lists, or rotations are overwhelmingly
279 * different between them, adjust scan balance for CPU work.
280 */
281 cost = nr_io * SWAP_CLUSTER_MAX + nr_rotated;
282
283 do {
284 unsigned long lrusize;
285
286 /*
287 * Hold lruvec->lru_lock is safe here, since
288 * 1) The pinned lruvec in reclaim, or
289 * 2) From a pre-LRU page during refault (which also holds the
290 * rcu lock, so would be safe even if the page was on the LRU
291 * and could move simultaneously to a new lruvec).
292 */
293 spin_lock_irq(lock: &lruvec->lru_lock);
294 /* Record cost event */
295 if (file)
296 lruvec->file_cost += cost;
297 else
298 lruvec->anon_cost += cost;
299
300 /*
301 * Decay previous events
302 *
303 * Because workloads change over time (and to avoid
304 * overflow) we keep these statistics as a floating
305 * average, which ends up weighing recent refaults
306 * more than old ones.
307 */
308 lrusize = lruvec_page_state(lruvec, idx: NR_INACTIVE_ANON) +
309 lruvec_page_state(lruvec, idx: NR_ACTIVE_ANON) +
310 lruvec_page_state(lruvec, idx: NR_INACTIVE_FILE) +
311 lruvec_page_state(lruvec, idx: NR_ACTIVE_FILE);
312
313 if (lruvec->file_cost + lruvec->anon_cost > lrusize / 4) {
314 lruvec->file_cost /= 2;
315 lruvec->anon_cost /= 2;
316 }
317 spin_unlock_irq(lock: &lruvec->lru_lock);
318 } while ((lruvec = parent_lruvec(lruvec)));
319}
320
321void lru_note_cost_refault(struct folio *folio)
322{
323 lru_note_cost(lruvec: folio_lruvec(folio), file: folio_is_file_lru(folio),
324 nr_io: folio_nr_pages(folio), nr_rotated: 0);
325}
326
327static void folio_activate_fn(struct lruvec *lruvec, struct folio *folio)
328{
329 if (!folio_test_active(folio) && !folio_test_unevictable(folio)) {
330 long nr_pages = folio_nr_pages(folio);
331
332 lruvec_del_folio(lruvec, folio);
333 folio_set_active(folio);
334 lruvec_add_folio(lruvec, folio);
335 trace_mm_lru_activate(folio);
336
337 __count_vm_events(item: PGACTIVATE, delta: nr_pages);
338 __count_memcg_events(memcg: lruvec_memcg(lruvec), idx: PGACTIVATE,
339 count: nr_pages);
340 }
341}
342
343#ifdef CONFIG_SMP
344static void folio_activate_drain(int cpu)
345{
346 struct folio_batch *fbatch = &per_cpu(cpu_fbatches.activate, cpu);
347
348 if (folio_batch_count(fbatch))
349 folio_batch_move_lru(fbatch, move_fn: folio_activate_fn);
350}
351
352void folio_activate(struct folio *folio)
353{
354 if (folio_test_lru(folio) && !folio_test_active(folio) &&
355 !folio_test_unevictable(folio)) {
356 struct folio_batch *fbatch;
357
358 folio_get(folio);
359 local_lock(&cpu_fbatches.lock);
360 fbatch = this_cpu_ptr(&cpu_fbatches.activate);
361 folio_batch_add_and_move(fbatch, folio, move_fn: folio_activate_fn);
362 local_unlock(&cpu_fbatches.lock);
363 }
364}
365
366#else
367static inline void folio_activate_drain(int cpu)
368{
369}
370
371void folio_activate(struct folio *folio)
372{
373 struct lruvec *lruvec;
374
375 if (folio_test_clear_lru(folio)) {
376 lruvec = folio_lruvec_lock_irq(folio);
377 folio_activate_fn(lruvec, folio);
378 unlock_page_lruvec_irq(lruvec);
379 folio_set_lru(folio);
380 }
381}
382#endif
383
384static void __lru_cache_activate_folio(struct folio *folio)
385{
386 struct folio_batch *fbatch;
387 int i;
388
389 local_lock(&cpu_fbatches.lock);
390 fbatch = this_cpu_ptr(&cpu_fbatches.lru_add);
391
392 /*
393 * Search backwards on the optimistic assumption that the folio being
394 * activated has just been added to this batch. Note that only
395 * the local batch is examined as a !LRU folio could be in the
396 * process of being released, reclaimed, migrated or on a remote
397 * batch that is currently being drained. Furthermore, marking
398 * a remote batch's folio active potentially hits a race where
399 * a folio is marked active just after it is added to the inactive
400 * list causing accounting errors and BUG_ON checks to trigger.
401 */
402 for (i = folio_batch_count(fbatch) - 1; i >= 0; i--) {
403 struct folio *batch_folio = fbatch->folios[i];
404
405 if (batch_folio == folio) {
406 folio_set_active(folio);
407 break;
408 }
409 }
410
411 local_unlock(&cpu_fbatches.lock);
412}
413
414#ifdef CONFIG_LRU_GEN
415static void folio_inc_refs(struct folio *folio)
416{
417 unsigned long new_flags, old_flags = READ_ONCE(folio->flags);
418
419 if (folio_test_unevictable(folio))
420 return;
421
422 if (!folio_test_referenced(folio)) {
423 folio_set_referenced(folio);
424 return;
425 }
426
427 if (!folio_test_workingset(folio)) {
428 folio_set_workingset(folio);
429 return;
430 }
431
432 /* see the comment on MAX_NR_TIERS */
433 do {
434 new_flags = old_flags & LRU_REFS_MASK;
435 if (new_flags == LRU_REFS_MASK)
436 break;
437
438 new_flags += BIT(LRU_REFS_PGOFF);
439 new_flags |= old_flags & ~LRU_REFS_MASK;
440 } while (!try_cmpxchg(&folio->flags, &old_flags, new_flags));
441}
442#else
443static void folio_inc_refs(struct folio *folio)
444{
445}
446#endif /* CONFIG_LRU_GEN */
447
448/*
449 * Mark a page as having seen activity.
450 *
451 * inactive,unreferenced -> inactive,referenced
452 * inactive,referenced -> active,unreferenced
453 * active,unreferenced -> active,referenced
454 *
455 * When a newly allocated page is not yet visible, so safe for non-atomic ops,
456 * __SetPageReferenced(page) may be substituted for mark_page_accessed(page).
457 */
458void folio_mark_accessed(struct folio *folio)
459{
460 if (lru_gen_enabled()) {
461 folio_inc_refs(folio);
462 return;
463 }
464
465 if (!folio_test_referenced(folio)) {
466 folio_set_referenced(folio);
467 } else if (folio_test_unevictable(folio)) {
468 /*
469 * Unevictable pages are on the "LRU_UNEVICTABLE" list. But,
470 * this list is never rotated or maintained, so marking an
471 * unevictable page accessed has no effect.
472 */
473 } else if (!folio_test_active(folio)) {
474 /*
475 * If the folio is on the LRU, queue it for activation via
476 * cpu_fbatches.activate. Otherwise, assume the folio is in a
477 * folio_batch, mark it active and it'll be moved to the active
478 * LRU on the next drain.
479 */
480 if (folio_test_lru(folio))
481 folio_activate(folio);
482 else
483 __lru_cache_activate_folio(folio);
484 folio_clear_referenced(folio);
485 workingset_activation(folio);
486 }
487 if (folio_test_idle(folio))
488 folio_clear_idle(folio);
489}
490EXPORT_SYMBOL(folio_mark_accessed);
491
492/**
493 * folio_add_lru - Add a folio to an LRU list.
494 * @folio: The folio to be added to the LRU.
495 *
496 * Queue the folio for addition to the LRU. The decision on whether
497 * to add the page to the [in]active [file|anon] list is deferred until the
498 * folio_batch is drained. This gives a chance for the caller of folio_add_lru()
499 * have the folio added to the active list using folio_mark_accessed().
500 */
501void folio_add_lru(struct folio *folio)
502{
503 struct folio_batch *fbatch;
504
505 VM_BUG_ON_FOLIO(folio_test_active(folio) &&
506 folio_test_unevictable(folio), folio);
507 VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
508
509 /* see the comment in lru_gen_add_folio() */
510 if (lru_gen_enabled() && !folio_test_unevictable(folio) &&
511 lru_gen_in_fault() && !(current->flags & PF_MEMALLOC))
512 folio_set_active(folio);
513
514 folio_get(folio);
515 local_lock(&cpu_fbatches.lock);
516 fbatch = this_cpu_ptr(&cpu_fbatches.lru_add);
517 folio_batch_add_and_move(fbatch, folio, move_fn: lru_add_fn);
518 local_unlock(&cpu_fbatches.lock);
519}
520EXPORT_SYMBOL(folio_add_lru);
521
522/**
523 * folio_add_lru_vma() - Add a folio to the appropate LRU list for this VMA.
524 * @folio: The folio to be added to the LRU.
525 * @vma: VMA in which the folio is mapped.
526 *
527 * If the VMA is mlocked, @folio is added to the unevictable list.
528 * Otherwise, it is treated the same way as folio_add_lru().
529 */
530void folio_add_lru_vma(struct folio *folio, struct vm_area_struct *vma)
531{
532 VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
533
534 if (unlikely((vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) == VM_LOCKED))
535 mlock_new_folio(folio);
536 else
537 folio_add_lru(folio);
538}
539
540/*
541 * If the folio cannot be invalidated, it is moved to the
542 * inactive list to speed up its reclaim. It is moved to the
543 * head of the list, rather than the tail, to give the flusher
544 * threads some time to write it out, as this is much more
545 * effective than the single-page writeout from reclaim.
546 *
547 * If the folio isn't mapped and dirty/writeback, the folio
548 * could be reclaimed asap using the reclaim flag.
549 *
550 * 1. active, mapped folio -> none
551 * 2. active, dirty/writeback folio -> inactive, head, reclaim
552 * 3. inactive, mapped folio -> none
553 * 4. inactive, dirty/writeback folio -> inactive, head, reclaim
554 * 5. inactive, clean -> inactive, tail
555 * 6. Others -> none
556 *
557 * In 4, it moves to the head of the inactive list so the folio is
558 * written out by flusher threads as this is much more efficient
559 * than the single-page writeout from reclaim.
560 */
561static void lru_deactivate_file_fn(struct lruvec *lruvec, struct folio *folio)
562{
563 bool active = folio_test_active(folio);
564 long nr_pages = folio_nr_pages(folio);
565
566 if (folio_test_unevictable(folio))
567 return;
568
569 /* Some processes are using the folio */
570 if (folio_mapped(folio))
571 return;
572
573 lruvec_del_folio(lruvec, folio);
574 folio_clear_active(folio);
575 folio_clear_referenced(folio);
576
577 if (folio_test_writeback(folio) || folio_test_dirty(folio)) {
578 /*
579 * Setting the reclaim flag could race with
580 * folio_end_writeback() and confuse readahead. But the
581 * race window is _really_ small and it's not a critical
582 * problem.
583 */
584 lruvec_add_folio(lruvec, folio);
585 folio_set_reclaim(folio);
586 } else {
587 /*
588 * The folio's writeback ended while it was in the batch.
589 * We move that folio to the tail of the inactive list.
590 */
591 lruvec_add_folio_tail(lruvec, folio);
592 __count_vm_events(item: PGROTATED, delta: nr_pages);
593 }
594
595 if (active) {
596 __count_vm_events(item: PGDEACTIVATE, delta: nr_pages);
597 __count_memcg_events(memcg: lruvec_memcg(lruvec), idx: PGDEACTIVATE,
598 count: nr_pages);
599 }
600}
601
602static void lru_deactivate_fn(struct lruvec *lruvec, struct folio *folio)
603{
604 if (!folio_test_unevictable(folio) && (folio_test_active(folio) || lru_gen_enabled())) {
605 long nr_pages = folio_nr_pages(folio);
606
607 lruvec_del_folio(lruvec, folio);
608 folio_clear_active(folio);
609 folio_clear_referenced(folio);
610 lruvec_add_folio(lruvec, folio);
611
612 __count_vm_events(item: PGDEACTIVATE, delta: nr_pages);
613 __count_memcg_events(memcg: lruvec_memcg(lruvec), idx: PGDEACTIVATE,
614 count: nr_pages);
615 }
616}
617
618static void lru_lazyfree_fn(struct lruvec *lruvec, struct folio *folio)
619{
620 if (folio_test_anon(folio) && folio_test_swapbacked(folio) &&
621 !folio_test_swapcache(folio) && !folio_test_unevictable(folio)) {
622 long nr_pages = folio_nr_pages(folio);
623
624 lruvec_del_folio(lruvec, folio);
625 folio_clear_active(folio);
626 folio_clear_referenced(folio);
627 /*
628 * Lazyfree folios are clean anonymous folios. They have
629 * the swapbacked flag cleared, to distinguish them from normal
630 * anonymous folios
631 */
632 folio_clear_swapbacked(folio);
633 lruvec_add_folio(lruvec, folio);
634
635 __count_vm_events(item: PGLAZYFREE, delta: nr_pages);
636 __count_memcg_events(memcg: lruvec_memcg(lruvec), idx: PGLAZYFREE,
637 count: nr_pages);
638 }
639}
640
641/*
642 * Drain pages out of the cpu's folio_batch.
643 * Either "cpu" is the current CPU, and preemption has already been
644 * disabled; or "cpu" is being hot-unplugged, and is already dead.
645 */
646void lru_add_drain_cpu(int cpu)
647{
648 struct cpu_fbatches *fbatches = &per_cpu(cpu_fbatches, cpu);
649 struct folio_batch *fbatch = &fbatches->lru_add;
650
651 if (folio_batch_count(fbatch))
652 folio_batch_move_lru(fbatch, move_fn: lru_add_fn);
653
654 fbatch = &per_cpu(lru_rotate.fbatch, cpu);
655 /* Disabling interrupts below acts as a compiler barrier. */
656 if (data_race(folio_batch_count(fbatch))) {
657 unsigned long flags;
658
659 /* No harm done if a racing interrupt already did this */
660 local_lock_irqsave(&lru_rotate.lock, flags);
661 folio_batch_move_lru(fbatch, move_fn: lru_move_tail_fn);
662 local_unlock_irqrestore(&lru_rotate.lock, flags);
663 }
664
665 fbatch = &fbatches->lru_deactivate_file;
666 if (folio_batch_count(fbatch))
667 folio_batch_move_lru(fbatch, move_fn: lru_deactivate_file_fn);
668
669 fbatch = &fbatches->lru_deactivate;
670 if (folio_batch_count(fbatch))
671 folio_batch_move_lru(fbatch, move_fn: lru_deactivate_fn);
672
673 fbatch = &fbatches->lru_lazyfree;
674 if (folio_batch_count(fbatch))
675 folio_batch_move_lru(fbatch, move_fn: lru_lazyfree_fn);
676
677 folio_activate_drain(cpu);
678}
679
680/**
681 * deactivate_file_folio() - Deactivate a file folio.
682 * @folio: Folio to deactivate.
683 *
684 * This function hints to the VM that @folio is a good reclaim candidate,
685 * for example if its invalidation fails due to the folio being dirty
686 * or under writeback.
687 *
688 * Context: Caller holds a reference on the folio.
689 */
690void deactivate_file_folio(struct folio *folio)
691{
692 struct folio_batch *fbatch;
693
694 /* Deactivating an unevictable folio will not accelerate reclaim */
695 if (folio_test_unevictable(folio))
696 return;
697
698 folio_get(folio);
699 local_lock(&cpu_fbatches.lock);
700 fbatch = this_cpu_ptr(&cpu_fbatches.lru_deactivate_file);
701 folio_batch_add_and_move(fbatch, folio, move_fn: lru_deactivate_file_fn);
702 local_unlock(&cpu_fbatches.lock);
703}
704
705/*
706 * folio_deactivate - deactivate a folio
707 * @folio: folio to deactivate
708 *
709 * folio_deactivate() moves @folio to the inactive list if @folio was on the
710 * active list and was not unevictable. This is done to accelerate the
711 * reclaim of @folio.
712 */
713void folio_deactivate(struct folio *folio)
714{
715 if (folio_test_lru(folio) && !folio_test_unevictable(folio) &&
716 (folio_test_active(folio) || lru_gen_enabled())) {
717 struct folio_batch *fbatch;
718
719 folio_get(folio);
720 local_lock(&cpu_fbatches.lock);
721 fbatch = this_cpu_ptr(&cpu_fbatches.lru_deactivate);
722 folio_batch_add_and_move(fbatch, folio, move_fn: lru_deactivate_fn);
723 local_unlock(&cpu_fbatches.lock);
724 }
725}
726
727/**
728 * folio_mark_lazyfree - make an anon folio lazyfree
729 * @folio: folio to deactivate
730 *
731 * folio_mark_lazyfree() moves @folio to the inactive file list.
732 * This is done to accelerate the reclaim of @folio.
733 */
734void folio_mark_lazyfree(struct folio *folio)
735{
736 if (folio_test_lru(folio) && folio_test_anon(folio) &&
737 folio_test_swapbacked(folio) && !folio_test_swapcache(folio) &&
738 !folio_test_unevictable(folio)) {
739 struct folio_batch *fbatch;
740
741 folio_get(folio);
742 local_lock(&cpu_fbatches.lock);
743 fbatch = this_cpu_ptr(&cpu_fbatches.lru_lazyfree);
744 folio_batch_add_and_move(fbatch, folio, move_fn: lru_lazyfree_fn);
745 local_unlock(&cpu_fbatches.lock);
746 }
747}
748
749void lru_add_drain(void)
750{
751 local_lock(&cpu_fbatches.lock);
752 lru_add_drain_cpu(smp_processor_id());
753 local_unlock(&cpu_fbatches.lock);
754 mlock_drain_local();
755}
756
757/*
758 * It's called from per-cpu workqueue context in SMP case so
759 * lru_add_drain_cpu and invalidate_bh_lrus_cpu should run on
760 * the same cpu. It shouldn't be a problem in !SMP case since
761 * the core is only one and the locks will disable preemption.
762 */
763static void lru_add_and_bh_lrus_drain(void)
764{
765 local_lock(&cpu_fbatches.lock);
766 lru_add_drain_cpu(smp_processor_id());
767 local_unlock(&cpu_fbatches.lock);
768 invalidate_bh_lrus_cpu();
769 mlock_drain_local();
770}
771
772void lru_add_drain_cpu_zone(struct zone *zone)
773{
774 local_lock(&cpu_fbatches.lock);
775 lru_add_drain_cpu(smp_processor_id());
776 drain_local_pages(zone);
777 local_unlock(&cpu_fbatches.lock);
778 mlock_drain_local();
779}
780
781#ifdef CONFIG_SMP
782
783static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work);
784
785static void lru_add_drain_per_cpu(struct work_struct *dummy)
786{
787 lru_add_and_bh_lrus_drain();
788}
789
790static bool cpu_needs_drain(unsigned int cpu)
791{
792 struct cpu_fbatches *fbatches = &per_cpu(cpu_fbatches, cpu);
793
794 /* Check these in order of likelihood that they're not zero */
795 return folio_batch_count(fbatch: &fbatches->lru_add) ||
796 data_race(folio_batch_count(&per_cpu(lru_rotate.fbatch, cpu))) ||
797 folio_batch_count(fbatch: &fbatches->lru_deactivate_file) ||
798 folio_batch_count(fbatch: &fbatches->lru_deactivate) ||
799 folio_batch_count(fbatch: &fbatches->lru_lazyfree) ||
800 folio_batch_count(fbatch: &fbatches->activate) ||
801 need_mlock_drain(cpu) ||
802 has_bh_in_lru(cpu, NULL);
803}
804
805/*
806 * Doesn't need any cpu hotplug locking because we do rely on per-cpu
807 * kworkers being shut down before our page_alloc_cpu_dead callback is
808 * executed on the offlined cpu.
809 * Calling this function with cpu hotplug locks held can actually lead
810 * to obscure indirect dependencies via WQ context.
811 */
812static inline void __lru_add_drain_all(bool force_all_cpus)
813{
814 /*
815 * lru_drain_gen - Global pages generation number
816 *
817 * (A) Definition: global lru_drain_gen = x implies that all generations
818 * 0 < n <= x are already *scheduled* for draining.
819 *
820 * This is an optimization for the highly-contended use case where a
821 * user space workload keeps constantly generating a flow of pages for
822 * each CPU.
823 */
824 static unsigned int lru_drain_gen;
825 static struct cpumask has_work;
826 static DEFINE_MUTEX(lock);
827 unsigned cpu, this_gen;
828
829 /*
830 * Make sure nobody triggers this path before mm_percpu_wq is fully
831 * initialized.
832 */
833 if (WARN_ON(!mm_percpu_wq))
834 return;
835
836 /*
837 * Guarantee folio_batch counter stores visible by this CPU
838 * are visible to other CPUs before loading the current drain
839 * generation.
840 */
841 smp_mb();
842
843 /*
844 * (B) Locally cache global LRU draining generation number
845 *
846 * The read barrier ensures that the counter is loaded before the mutex
847 * is taken. It pairs with smp_mb() inside the mutex critical section
848 * at (D).
849 */
850 this_gen = smp_load_acquire(&lru_drain_gen);
851
852 mutex_lock(&lock);
853
854 /*
855 * (C) Exit the draining operation if a newer generation, from another
856 * lru_add_drain_all(), was already scheduled for draining. Check (A).
857 */
858 if (unlikely(this_gen != lru_drain_gen && !force_all_cpus))
859 goto done;
860
861 /*
862 * (D) Increment global generation number
863 *
864 * Pairs with smp_load_acquire() at (B), outside of the critical
865 * section. Use a full memory barrier to guarantee that the
866 * new global drain generation number is stored before loading
867 * folio_batch counters.
868 *
869 * This pairing must be done here, before the for_each_online_cpu loop
870 * below which drains the page vectors.
871 *
872 * Let x, y, and z represent some system CPU numbers, where x < y < z.
873 * Assume CPU #z is in the middle of the for_each_online_cpu loop
874 * below and has already reached CPU #y's per-cpu data. CPU #x comes
875 * along, adds some pages to its per-cpu vectors, then calls
876 * lru_add_drain_all().
877 *
878 * If the paired barrier is done at any later step, e.g. after the
879 * loop, CPU #x will just exit at (C) and miss flushing out all of its
880 * added pages.
881 */
882 WRITE_ONCE(lru_drain_gen, lru_drain_gen + 1);
883 smp_mb();
884
885 cpumask_clear(dstp: &has_work);
886 for_each_online_cpu(cpu) {
887 struct work_struct *work = &per_cpu(lru_add_drain_work, cpu);
888
889 if (cpu_needs_drain(cpu)) {
890 INIT_WORK(work, lru_add_drain_per_cpu);
891 queue_work_on(cpu, wq: mm_percpu_wq, work);
892 __cpumask_set_cpu(cpu, dstp: &has_work);
893 }
894 }
895
896 for_each_cpu(cpu, &has_work)
897 flush_work(work: &per_cpu(lru_add_drain_work, cpu));
898
899done:
900 mutex_unlock(lock: &lock);
901}
902
903void lru_add_drain_all(void)
904{
905 __lru_add_drain_all(force_all_cpus: false);
906}
907#else
908void lru_add_drain_all(void)
909{
910 lru_add_drain();
911}
912#endif /* CONFIG_SMP */
913
914atomic_t lru_disable_count = ATOMIC_INIT(0);
915
916/*
917 * lru_cache_disable() needs to be called before we start compiling
918 * a list of pages to be migrated using isolate_lru_page().
919 * It drains pages on LRU cache and then disable on all cpus until
920 * lru_cache_enable is called.
921 *
922 * Must be paired with a call to lru_cache_enable().
923 */
924void lru_cache_disable(void)
925{
926 atomic_inc(v: &lru_disable_count);
927 /*
928 * Readers of lru_disable_count are protected by either disabling
929 * preemption or rcu_read_lock:
930 *
931 * preempt_disable, local_irq_disable [bh_lru_lock()]
932 * rcu_read_lock [rt_spin_lock CONFIG_PREEMPT_RT]
933 * preempt_disable [local_lock !CONFIG_PREEMPT_RT]
934 *
935 * Since v5.1 kernel, synchronize_rcu() is guaranteed to wait on
936 * preempt_disable() regions of code. So any CPU which sees
937 * lru_disable_count = 0 will have exited the critical
938 * section when synchronize_rcu() returns.
939 */
940 synchronize_rcu_expedited();
941#ifdef CONFIG_SMP
942 __lru_add_drain_all(force_all_cpus: true);
943#else
944 lru_add_and_bh_lrus_drain();
945#endif
946}
947
948/**
949 * release_pages - batched put_page()
950 * @arg: array of pages to release
951 * @nr: number of pages
952 *
953 * Decrement the reference count on all the pages in @arg. If it
954 * fell to zero, remove the page from the LRU and free it.
955 *
956 * Note that the argument can be an array of pages, encoded pages,
957 * or folio pointers. We ignore any encoded bits, and turn any of
958 * them into just a folio that gets free'd.
959 */
960void release_pages(release_pages_arg arg, int nr)
961{
962 int i;
963 struct encoded_page **encoded = arg.encoded_pages;
964 LIST_HEAD(pages_to_free);
965 struct lruvec *lruvec = NULL;
966 unsigned long flags = 0;
967 unsigned int lock_batch;
968
969 for (i = 0; i < nr; i++) {
970 struct folio *folio;
971
972 /* Turn any of the argument types into a folio */
973 folio = page_folio(encoded_page_ptr(encoded[i]));
974
975 /*
976 * Make sure the IRQ-safe lock-holding time does not get
977 * excessive with a continuous string of pages from the
978 * same lruvec. The lock is held only if lruvec != NULL.
979 */
980 if (lruvec && ++lock_batch == SWAP_CLUSTER_MAX) {
981 unlock_page_lruvec_irqrestore(lruvec, flags);
982 lruvec = NULL;
983 }
984
985 if (is_huge_zero_page(page: &folio->page))
986 continue;
987
988 if (folio_is_zone_device(folio)) {
989 if (lruvec) {
990 unlock_page_lruvec_irqrestore(lruvec, flags);
991 lruvec = NULL;
992 }
993 if (put_devmap_managed_page(page: &folio->page))
994 continue;
995 if (folio_put_testzero(folio))
996 free_zone_device_page(page: &folio->page);
997 continue;
998 }
999
1000 if (!folio_put_testzero(folio))
1001 continue;
1002
1003 if (folio_test_large(folio)) {
1004 if (lruvec) {
1005 unlock_page_lruvec_irqrestore(lruvec, flags);
1006 lruvec = NULL;
1007 }
1008 __folio_put_large(folio);
1009 continue;
1010 }
1011
1012 if (folio_test_lru(folio)) {
1013 struct lruvec *prev_lruvec = lruvec;
1014
1015 lruvec = folio_lruvec_relock_irqsave(folio, locked_lruvec: lruvec,
1016 flags: &flags);
1017 if (prev_lruvec != lruvec)
1018 lock_batch = 0;
1019
1020 lruvec_del_folio(lruvec, folio);
1021 __folio_clear_lru_flags(folio);
1022 }
1023
1024 /*
1025 * In rare cases, when truncation or holepunching raced with
1026 * munlock after VM_LOCKED was cleared, Mlocked may still be
1027 * found set here. This does not indicate a problem, unless
1028 * "unevictable_pgs_cleared" appears worryingly large.
1029 */
1030 if (unlikely(folio_test_mlocked(folio))) {
1031 __folio_clear_mlocked(folio);
1032 zone_stat_sub_folio(folio, item: NR_MLOCK);
1033 count_vm_event(item: UNEVICTABLE_PGCLEARED);
1034 }
1035
1036 list_add(new: &folio->lru, head: &pages_to_free);
1037 }
1038 if (lruvec)
1039 unlock_page_lruvec_irqrestore(lruvec, flags);
1040
1041 mem_cgroup_uncharge_list(page_list: &pages_to_free);
1042 free_unref_page_list(list: &pages_to_free);
1043}
1044EXPORT_SYMBOL(release_pages);
1045
1046/*
1047 * The folios which we're about to release may be in the deferred lru-addition
1048 * queues. That would prevent them from really being freed right now. That's
1049 * OK from a correctness point of view but is inefficient - those folios may be
1050 * cache-warm and we want to give them back to the page allocator ASAP.
1051 *
1052 * So __folio_batch_release() will drain those queues here.
1053 * folio_batch_move_lru() calls folios_put() directly to avoid
1054 * mutual recursion.
1055 */
1056void __folio_batch_release(struct folio_batch *fbatch)
1057{
1058 if (!fbatch->percpu_pvec_drained) {
1059 lru_add_drain();
1060 fbatch->percpu_pvec_drained = true;
1061 }
1062 release_pages(fbatch->folios, folio_batch_count(fbatch));
1063 folio_batch_reinit(fbatch);
1064}
1065EXPORT_SYMBOL(__folio_batch_release);
1066
1067/**
1068 * folio_batch_remove_exceptionals() - Prune non-folios from a batch.
1069 * @fbatch: The batch to prune
1070 *
1071 * find_get_entries() fills a batch with both folios and shadow/swap/DAX
1072 * entries. This function prunes all the non-folio entries from @fbatch
1073 * without leaving holes, so that it can be passed on to folio-only batch
1074 * operations.
1075 */
1076void folio_batch_remove_exceptionals(struct folio_batch *fbatch)
1077{
1078 unsigned int i, j;
1079
1080 for (i = 0, j = 0; i < folio_batch_count(fbatch); i++) {
1081 struct folio *folio = fbatch->folios[i];
1082 if (!xa_is_value(entry: folio))
1083 fbatch->folios[j++] = folio;
1084 }
1085 fbatch->nr = j;
1086}
1087
1088/*
1089 * Perform any setup for the swap system
1090 */
1091void __init swap_setup(void)
1092{
1093 unsigned long megs = totalram_pages() >> (20 - PAGE_SHIFT);
1094
1095 /* Use a smaller cluster for small-memory machines */
1096 if (megs < 16)
1097 page_cluster = 2;
1098 else
1099 page_cluster = 3;
1100 /*
1101 * Right now other parts of the system means that we
1102 * _really_ don't want to cluster much more
1103 */
1104}
1105

source code of linux/mm/swap.c