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;
48static const int page_cluster_max = 31;
49
50struct cpu_fbatches {
51 /*
52 * The following folio batches are grouped together because they are protected
53 * by disabling preemption (and interrupts remain enabled).
54 */
55 local_lock_t lock;
56 struct folio_batch lru_add;
57 struct folio_batch lru_deactivate_file;
58 struct folio_batch lru_deactivate;
59 struct folio_batch lru_lazyfree;
60#ifdef CONFIG_SMP
61 struct folio_batch lru_activate;
62#endif
63 /* Protecting the following batches which require disabling interrupts */
64 local_lock_t lock_irq;
65 struct folio_batch lru_move_tail;
66};
67
68static DEFINE_PER_CPU(struct cpu_fbatches, cpu_fbatches) = {
69 .lock = INIT_LOCAL_LOCK(lock),
70 .lock_irq = INIT_LOCAL_LOCK(lock_irq),
71};
72
73static void __page_cache_release(struct folio *folio, struct lruvec **lruvecp,
74 unsigned long *flagsp)
75{
76 if (folio_test_lru(folio)) {
77 folio_lruvec_relock_irqsave(folio, lruvecp, flags: flagsp);
78 lruvec_del_folio(lruvec: *lruvecp, folio);
79 __folio_clear_lru_flags(folio);
80 }
81}
82
83/*
84 * This path almost never happens for VM activity - pages are normally freed
85 * in batches. But it gets used by networking - and for compound pages.
86 */
87static void page_cache_release(struct folio *folio)
88{
89 struct lruvec *lruvec = NULL;
90 unsigned long flags;
91
92 __page_cache_release(folio, lruvecp: &lruvec, flagsp: &flags);
93 if (lruvec)
94 unlock_page_lruvec_irqrestore(lruvec, flags);
95}
96
97void __folio_put(struct folio *folio)
98{
99 if (unlikely(folio_is_zone_device(folio))) {
100 free_zone_device_folio(folio);
101 return;
102 }
103
104 if (folio_test_hugetlb(folio)) {
105 free_huge_folio(folio);
106 return;
107 }
108
109 page_cache_release(folio);
110 folio_unqueue_deferred_split(folio);
111 mem_cgroup_uncharge(folio);
112 free_frozen_pages(page: &folio->page, order: folio_order(folio));
113}
114EXPORT_SYMBOL(__folio_put);
115
116typedef void (*move_fn_t)(struct lruvec *lruvec, struct folio *folio);
117
118static void lru_add(struct lruvec *lruvec, struct folio *folio)
119{
120 int was_unevictable = folio_test_clear_unevictable(folio);
121 long nr_pages = folio_nr_pages(folio);
122
123 VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
124
125 /*
126 * Is an smp_mb__after_atomic() still required here, before
127 * folio_evictable() tests the mlocked flag, to rule out the possibility
128 * of stranding an evictable folio on an unevictable LRU? I think
129 * not, because __munlock_folio() only clears the mlocked flag
130 * while the LRU lock is held.
131 *
132 * (That is not true of __page_cache_release(), and not necessarily
133 * true of folios_put(): but those only clear the mlocked flag after
134 * folio_put_testzero() has excluded any other users of the folio.)
135 */
136 if (folio_evictable(folio)) {
137 if (was_unevictable)
138 __count_vm_events(item: UNEVICTABLE_PGRESCUED, delta: nr_pages);
139 } else {
140 folio_clear_active(folio);
141 folio_set_unevictable(folio);
142 /*
143 * folio->mlock_count = !!folio_test_mlocked(folio)?
144 * But that leaves __mlock_folio() in doubt whether another
145 * actor has already counted the mlock or not. Err on the
146 * safe side, underestimate, let page reclaim fix it, rather
147 * than leaving a page on the unevictable LRU indefinitely.
148 */
149 folio->mlock_count = 0;
150 if (!was_unevictable)
151 __count_vm_events(item: UNEVICTABLE_PGCULLED, delta: nr_pages);
152 }
153
154 lruvec_add_folio(lruvec, folio);
155 trace_mm_lru_insertion(folio);
156}
157
158static void folio_batch_move_lru(struct folio_batch *fbatch, move_fn_t move_fn)
159{
160 int i;
161 struct lruvec *lruvec = NULL;
162 unsigned long flags = 0;
163
164 for (i = 0; i < folio_batch_count(fbatch); i++) {
165 struct folio *folio = fbatch->folios[i];
166
167 /* block memcg migration while the folio moves between lru */
168 if (move_fn != lru_add && !folio_test_clear_lru(folio))
169 continue;
170
171 folio_lruvec_relock_irqsave(folio, lruvecp: &lruvec, flags: &flags);
172 move_fn(lruvec, folio);
173
174 folio_set_lru(folio);
175 }
176
177 if (lruvec)
178 unlock_page_lruvec_irqrestore(lruvec, flags);
179 folios_put(folios: fbatch);
180}
181
182static void __folio_batch_add_and_move(struct folio_batch __percpu *fbatch,
183 struct folio *folio, move_fn_t move_fn, bool disable_irq)
184{
185 unsigned long flags;
186
187 folio_get(folio);
188
189 if (disable_irq)
190 local_lock_irqsave(&cpu_fbatches.lock_irq, flags);
191 else
192 local_lock(&cpu_fbatches.lock);
193
194 if (!folio_batch_add(this_cpu_ptr(fbatch), folio) ||
195 !folio_may_be_lru_cached(folio) || lru_cache_disabled())
196 folio_batch_move_lru(this_cpu_ptr(fbatch), move_fn);
197
198 if (disable_irq)
199 local_unlock_irqrestore(&cpu_fbatches.lock_irq, flags);
200 else
201 local_unlock(&cpu_fbatches.lock);
202}
203
204#define folio_batch_add_and_move(folio, op) \
205 __folio_batch_add_and_move( \
206 &cpu_fbatches.op, \
207 folio, \
208 op, \
209 offsetof(struct cpu_fbatches, op) >= \
210 offsetof(struct cpu_fbatches, lock_irq) \
211 )
212
213static void lru_move_tail(struct lruvec *lruvec, struct folio *folio)
214{
215 if (folio_test_unevictable(folio))
216 return;
217
218 lruvec_del_folio(lruvec, folio);
219 folio_clear_active(folio);
220 lruvec_add_folio_tail(lruvec, folio);
221 __count_vm_events(item: PGROTATED, delta: folio_nr_pages(folio));
222}
223
224/*
225 * Writeback is about to end against a folio which has been marked for
226 * immediate reclaim. If it still appears to be reclaimable, move it
227 * to the tail of the inactive list.
228 *
229 * folio_rotate_reclaimable() must disable IRQs, to prevent nasty races.
230 */
231void folio_rotate_reclaimable(struct folio *folio)
232{
233 if (folio_test_locked(folio) || folio_test_dirty(folio) ||
234 folio_test_unevictable(folio) || !folio_test_lru(folio))
235 return;
236
237 folio_batch_add_and_move(folio, lru_move_tail);
238}
239
240void lru_note_cost_unlock_irq(struct lruvec *lruvec, bool file,
241 unsigned int nr_io, unsigned int nr_rotated)
242 __releases(lruvec->lru_lock)
243{
244 unsigned long cost;
245
246 /*
247 * Reflect the relative cost of incurring IO and spending CPU
248 * time on rotations. This doesn't attempt to make a precise
249 * comparison, it just says: if reloads are about comparable
250 * between the LRU lists, or rotations are overwhelmingly
251 * different between them, adjust scan balance for CPU work.
252 */
253 cost = nr_io * SWAP_CLUSTER_MAX + nr_rotated;
254 if (!cost) {
255 spin_unlock_irq(lock: &lruvec->lru_lock);
256 return;
257 }
258
259 for (;;) {
260 unsigned long lrusize;
261
262 /* Record cost event */
263 if (file)
264 lruvec->file_cost += cost;
265 else
266 lruvec->anon_cost += cost;
267
268 /*
269 * Decay previous events
270 *
271 * Because workloads change over time (and to avoid
272 * overflow) we keep these statistics as a floating
273 * average, which ends up weighing recent refaults
274 * more than old ones.
275 */
276 lrusize = lruvec_page_state(lruvec, idx: NR_INACTIVE_ANON) +
277 lruvec_page_state(lruvec, idx: NR_ACTIVE_ANON) +
278 lruvec_page_state(lruvec, idx: NR_INACTIVE_FILE) +
279 lruvec_page_state(lruvec, idx: NR_ACTIVE_FILE);
280
281 if (lruvec->file_cost + lruvec->anon_cost > lrusize / 4) {
282 lruvec->file_cost /= 2;
283 lruvec->anon_cost /= 2;
284 }
285
286 spin_unlock_irq(lock: &lruvec->lru_lock);
287 lruvec = parent_lruvec(lruvec);
288 if (!lruvec)
289 break;
290 spin_lock_irq(lock: &lruvec->lru_lock);
291 }
292}
293
294void lru_note_cost_refault(struct folio *folio)
295{
296 struct lruvec *lruvec;
297
298 lruvec = folio_lruvec_lock_irq(folio);
299 lru_note_cost_unlock_irq(lruvec, file: folio_is_file_lru(folio),
300 nr_io: folio_nr_pages(folio), nr_rotated: 0);
301}
302
303static void lru_activate(struct lruvec *lruvec, struct folio *folio)
304{
305 long nr_pages = folio_nr_pages(folio);
306
307 if (folio_test_active(folio) || folio_test_unevictable(folio))
308 return;
309
310
311 lruvec_del_folio(lruvec, folio);
312 folio_set_active(folio);
313 lruvec_add_folio(lruvec, folio);
314 trace_mm_lru_activate(folio);
315
316 __count_vm_events(item: PGACTIVATE, delta: nr_pages);
317 count_memcg_events(memcg: lruvec_memcg(lruvec), idx: PGACTIVATE, count: nr_pages);
318}
319
320#ifdef CONFIG_SMP
321static void folio_activate_drain(int cpu)
322{
323 struct folio_batch *fbatch = &per_cpu(cpu_fbatches.lru_activate, cpu);
324
325 if (folio_batch_count(fbatch))
326 folio_batch_move_lru(fbatch, move_fn: lru_activate);
327}
328
329void folio_activate(struct folio *folio)
330{
331 if (folio_test_active(folio) || folio_test_unevictable(folio) ||
332 !folio_test_lru(folio))
333 return;
334
335 folio_batch_add_and_move(folio, lru_activate);
336}
337
338#else
339static inline void folio_activate_drain(int cpu)
340{
341}
342
343void folio_activate(struct folio *folio)
344{
345 struct lruvec *lruvec;
346
347 if (!folio_test_clear_lru(folio))
348 return;
349
350 lruvec = folio_lruvec_lock_irq(folio);
351 lru_activate(lruvec, folio);
352 unlock_page_lruvec_irq(lruvec);
353 folio_set_lru(folio);
354}
355#endif
356
357static void __lru_cache_activate_folio(struct folio *folio)
358{
359 struct folio_batch *fbatch;
360 int i;
361
362 local_lock(&cpu_fbatches.lock);
363 fbatch = this_cpu_ptr(&cpu_fbatches.lru_add);
364
365 /*
366 * Search backwards on the optimistic assumption that the folio being
367 * activated has just been added to this batch. Note that only
368 * the local batch is examined as a !LRU folio could be in the
369 * process of being released, reclaimed, migrated or on a remote
370 * batch that is currently being drained. Furthermore, marking
371 * a remote batch's folio active potentially hits a race where
372 * a folio is marked active just after it is added to the inactive
373 * list causing accounting errors and BUG_ON checks to trigger.
374 */
375 for (i = folio_batch_count(fbatch) - 1; i >= 0; i--) {
376 struct folio *batch_folio = fbatch->folios[i];
377
378 if (batch_folio == folio) {
379 folio_set_active(folio);
380 break;
381 }
382 }
383
384 local_unlock(&cpu_fbatches.lock);
385}
386
387#ifdef CONFIG_LRU_GEN
388
389static void lru_gen_inc_refs(struct folio *folio)
390{
391 unsigned long new_flags, old_flags = READ_ONCE(folio->flags.f);
392
393 if (folio_test_unevictable(folio))
394 return;
395
396 /* see the comment on LRU_REFS_FLAGS */
397 if (!folio_test_referenced(folio)) {
398 set_mask_bits(&folio->flags.f, LRU_REFS_MASK, BIT(PG_referenced));
399 return;
400 }
401
402 do {
403 if ((old_flags & LRU_REFS_MASK) == LRU_REFS_MASK) {
404 if (!folio_test_workingset(folio))
405 folio_set_workingset(folio);
406 return;
407 }
408
409 new_flags = old_flags + BIT(LRU_REFS_PGOFF);
410 } while (!try_cmpxchg(&folio->flags.f, &old_flags, new_flags));
411}
412
413static bool lru_gen_clear_refs(struct folio *folio)
414{
415 struct lru_gen_folio *lrugen;
416 int gen = folio_lru_gen(folio);
417 int type = folio_is_file_lru(folio);
418
419 if (gen < 0)
420 return true;
421
422 set_mask_bits(&folio->flags.f, LRU_REFS_FLAGS | BIT(PG_workingset), 0);
423
424 lrugen = &folio_lruvec(folio)->lrugen;
425 /* whether can do without shuffling under the LRU lock */
426 return gen == lru_gen_from_seq(READ_ONCE(lrugen->min_seq[type]));
427}
428
429#else /* !CONFIG_LRU_GEN */
430
431static void lru_gen_inc_refs(struct folio *folio)
432{
433}
434
435static bool lru_gen_clear_refs(struct folio *folio)
436{
437 return false;
438}
439
440#endif /* CONFIG_LRU_GEN */
441
442/**
443 * folio_mark_accessed - Mark a folio as having seen activity.
444 * @folio: The folio to mark.
445 *
446 * This function will perform one of the following transitions:
447 *
448 * * inactive,unreferenced -> inactive,referenced
449 * * inactive,referenced -> active,unreferenced
450 * * active,unreferenced -> active,referenced
451 *
452 * When a newly allocated folio is not yet visible, so safe for non-atomic ops,
453 * __folio_set_referenced() may be substituted for folio_mark_accessed().
454 */
455void folio_mark_accessed(struct folio *folio)
456{
457 if (folio_test_dropbehind(folio))
458 return;
459 if (lru_gen_enabled()) {
460 lru_gen_inc_refs(folio);
461 return;
462 }
463
464 if (!folio_test_referenced(folio)) {
465 folio_set_referenced(folio);
466 } else if (folio_test_unevictable(folio)) {
467 /*
468 * Unevictable pages are on the "LRU_UNEVICTABLE" list. But,
469 * this list is never rotated or maintained, so marking an
470 * unevictable page accessed has no effect.
471 */
472 } else if (!folio_test_active(folio)) {
473 /*
474 * If the folio is on the LRU, queue it for activation via
475 * cpu_fbatches.lru_activate. Otherwise, assume the folio is in a
476 * folio_batch, mark it active and it'll be moved to the active
477 * LRU on the next drain.
478 */
479 if (folio_test_lru(folio))
480 folio_activate(folio);
481 else
482 __lru_cache_activate_folio(folio);
483 folio_clear_referenced(folio);
484 workingset_activation(folio);
485 }
486 if (folio_test_idle(folio))
487 folio_clear_idle(folio);
488}
489EXPORT_SYMBOL(folio_mark_accessed);
490
491/**
492 * folio_add_lru - Add a folio to an LRU list.
493 * @folio: The folio to be added to the LRU.
494 *
495 * Queue the folio for addition to the LRU. The decision on whether
496 * to add the page to the [in]active [file|anon] list is deferred until the
497 * folio_batch is drained. This gives a chance for the caller of folio_add_lru()
498 * have the folio added to the active list using folio_mark_accessed().
499 */
500void folio_add_lru(struct folio *folio)
501{
502 VM_BUG_ON_FOLIO(folio_test_active(folio) &&
503 folio_test_unevictable(folio), folio);
504 VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
505
506 /* see the comment in lru_gen_folio_seq() */
507 if (lru_gen_enabled() && !folio_test_unevictable(folio) &&
508 lru_gen_in_fault() && !(current->flags & PF_MEMALLOC))
509 folio_set_active(folio);
510
511 folio_batch_add_and_move(folio, lru_add);
512}
513EXPORT_SYMBOL(folio_add_lru);
514
515/**
516 * folio_add_lru_vma() - Add a folio to the appropate LRU list for this VMA.
517 * @folio: The folio to be added to the LRU.
518 * @vma: VMA in which the folio is mapped.
519 *
520 * If the VMA is mlocked, @folio is added to the unevictable list.
521 * Otherwise, it is treated the same way as folio_add_lru().
522 */
523void folio_add_lru_vma(struct folio *folio, struct vm_area_struct *vma)
524{
525 VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
526
527 if (unlikely((vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) == VM_LOCKED))
528 mlock_new_folio(folio);
529 else
530 folio_add_lru(folio);
531}
532
533/*
534 * If the folio cannot be invalidated, it is moved to the
535 * inactive list to speed up its reclaim. It is moved to the
536 * head of the list, rather than the tail, to give the flusher
537 * threads some time to write it out, as this is much more
538 * effective than the single-page writeout from reclaim.
539 *
540 * If the folio isn't mapped and dirty/writeback, the folio
541 * could be reclaimed asap using the reclaim flag.
542 *
543 * 1. active, mapped folio -> none
544 * 2. active, dirty/writeback folio -> inactive, head, reclaim
545 * 3. inactive, mapped folio -> none
546 * 4. inactive, dirty/writeback folio -> inactive, head, reclaim
547 * 5. inactive, clean -> inactive, tail
548 * 6. Others -> none
549 *
550 * In 4, it moves to the head of the inactive list so the folio is
551 * written out by flusher threads as this is much more efficient
552 * than the single-page writeout from reclaim.
553 */
554static void lru_deactivate_file(struct lruvec *lruvec, struct folio *folio)
555{
556 bool active = folio_test_active(folio) || lru_gen_enabled();
557 long nr_pages = folio_nr_pages(folio);
558
559 if (folio_test_unevictable(folio))
560 return;
561
562 /* Some processes are using the folio */
563 if (folio_mapped(folio))
564 return;
565
566 lruvec_del_folio(lruvec, folio);
567 folio_clear_active(folio);
568 folio_clear_referenced(folio);
569
570 if (folio_test_writeback(folio) || folio_test_dirty(folio)) {
571 /*
572 * Setting the reclaim flag could race with
573 * folio_end_writeback() and confuse readahead. But the
574 * race window is _really_ small and it's not a critical
575 * problem.
576 */
577 lruvec_add_folio(lruvec, folio);
578 folio_set_reclaim(folio);
579 } else {
580 /*
581 * The folio's writeback ended while it was in the batch.
582 * We move that folio to the tail of the inactive list.
583 */
584 lruvec_add_folio_tail(lruvec, folio);
585 __count_vm_events(item: PGROTATED, delta: nr_pages);
586 }
587
588 if (active) {
589 __count_vm_events(item: PGDEACTIVATE, delta: nr_pages);
590 count_memcg_events(memcg: lruvec_memcg(lruvec), idx: PGDEACTIVATE,
591 count: nr_pages);
592 }
593}
594
595static void lru_deactivate(struct lruvec *lruvec, struct folio *folio)
596{
597 long nr_pages = folio_nr_pages(folio);
598
599 if (folio_test_unevictable(folio) || !(folio_test_active(folio) || lru_gen_enabled()))
600 return;
601
602 lruvec_del_folio(lruvec, folio);
603 folio_clear_active(folio);
604 folio_clear_referenced(folio);
605 lruvec_add_folio(lruvec, folio);
606
607 __count_vm_events(item: PGDEACTIVATE, delta: nr_pages);
608 count_memcg_events(memcg: lruvec_memcg(lruvec), idx: PGDEACTIVATE, count: nr_pages);
609}
610
611static void lru_lazyfree(struct lruvec *lruvec, struct folio *folio)
612{
613 long nr_pages = folio_nr_pages(folio);
614
615 if (!folio_test_anon(folio) || !folio_test_swapbacked(folio) ||
616 folio_test_swapcache(folio) || folio_test_unevictable(folio))
617 return;
618
619 lruvec_del_folio(lruvec, folio);
620 folio_clear_active(folio);
621 if (lru_gen_enabled())
622 lru_gen_clear_refs(folio);
623 else
624 folio_clear_referenced(folio);
625 /*
626 * Lazyfree folios are clean anonymous folios. They have
627 * the swapbacked flag cleared, to distinguish them from normal
628 * anonymous folios
629 */
630 folio_clear_swapbacked(folio);
631 lruvec_add_folio(lruvec, folio);
632
633 __count_vm_events(item: PGLAZYFREE, delta: nr_pages);
634 count_memcg_events(memcg: lruvec_memcg(lruvec), idx: PGLAZYFREE, count: nr_pages);
635}
636
637/*
638 * Drain pages out of the cpu's folio_batch.
639 * Either "cpu" is the current CPU, and preemption has already been
640 * disabled; or "cpu" is being hot-unplugged, and is already dead.
641 */
642void lru_add_drain_cpu(int cpu)
643{
644 struct cpu_fbatches *fbatches = &per_cpu(cpu_fbatches, cpu);
645 struct folio_batch *fbatch = &fbatches->lru_add;
646
647 if (folio_batch_count(fbatch))
648 folio_batch_move_lru(fbatch, move_fn: lru_add);
649
650 fbatch = &fbatches->lru_move_tail;
651 /* Disabling interrupts below acts as a compiler barrier. */
652 if (data_race(folio_batch_count(fbatch))) {
653 unsigned long flags;
654
655 /* No harm done if a racing interrupt already did this */
656 local_lock_irqsave(&cpu_fbatches.lock_irq, flags);
657 folio_batch_move_lru(fbatch, move_fn: lru_move_tail);
658 local_unlock_irqrestore(&cpu_fbatches.lock_irq, flags);
659 }
660
661 fbatch = &fbatches->lru_deactivate_file;
662 if (folio_batch_count(fbatch))
663 folio_batch_move_lru(fbatch, move_fn: lru_deactivate_file);
664
665 fbatch = &fbatches->lru_deactivate;
666 if (folio_batch_count(fbatch))
667 folio_batch_move_lru(fbatch, move_fn: lru_deactivate);
668
669 fbatch = &fbatches->lru_lazyfree;
670 if (folio_batch_count(fbatch))
671 folio_batch_move_lru(fbatch, move_fn: lru_lazyfree);
672
673 folio_activate_drain(cpu);
674}
675
676/**
677 * deactivate_file_folio() - Deactivate a file folio.
678 * @folio: Folio to deactivate.
679 *
680 * This function hints to the VM that @folio is a good reclaim candidate,
681 * for example if its invalidation fails due to the folio being dirty
682 * or under writeback.
683 *
684 * Context: Caller holds a reference on the folio.
685 */
686void deactivate_file_folio(struct folio *folio)
687{
688 /* Deactivating an unevictable folio will not accelerate reclaim */
689 if (folio_test_unevictable(folio) || !folio_test_lru(folio))
690 return;
691
692 if (lru_gen_enabled() && lru_gen_clear_refs(folio))
693 return;
694
695 folio_batch_add_and_move(folio, lru_deactivate_file);
696}
697
698/*
699 * folio_deactivate - deactivate a folio
700 * @folio: folio to deactivate
701 *
702 * folio_deactivate() moves @folio to the inactive list if @folio was on the
703 * active list and was not unevictable. This is done to accelerate the
704 * reclaim of @folio.
705 */
706void folio_deactivate(struct folio *folio)
707{
708 if (folio_test_unevictable(folio) || !folio_test_lru(folio))
709 return;
710
711 if (lru_gen_enabled() ? lru_gen_clear_refs(folio) : !folio_test_active(folio))
712 return;
713
714 folio_batch_add_and_move(folio, lru_deactivate);
715}
716
717/**
718 * folio_mark_lazyfree - make an anon folio lazyfree
719 * @folio: folio to deactivate
720 *
721 * folio_mark_lazyfree() moves @folio to the inactive file list.
722 * This is done to accelerate the reclaim of @folio.
723 */
724void folio_mark_lazyfree(struct folio *folio)
725{
726 if (!folio_test_anon(folio) || !folio_test_swapbacked(folio) ||
727 !folio_test_lru(folio) ||
728 folio_test_swapcache(folio) || folio_test_unevictable(folio))
729 return;
730
731 folio_batch_add_and_move(folio, lru_lazyfree);
732}
733
734void lru_add_drain(void)
735{
736 local_lock(&cpu_fbatches.lock);
737 lru_add_drain_cpu(smp_processor_id());
738 local_unlock(&cpu_fbatches.lock);
739 mlock_drain_local();
740}
741
742/*
743 * It's called from per-cpu workqueue context in SMP case so
744 * lru_add_drain_cpu and invalidate_bh_lrus_cpu should run on
745 * the same cpu. It shouldn't be a problem in !SMP case since
746 * the core is only one and the locks will disable preemption.
747 */
748static void lru_add_and_bh_lrus_drain(void)
749{
750 local_lock(&cpu_fbatches.lock);
751 lru_add_drain_cpu(smp_processor_id());
752 local_unlock(&cpu_fbatches.lock);
753 invalidate_bh_lrus_cpu();
754 mlock_drain_local();
755}
756
757void lru_add_drain_cpu_zone(struct zone *zone)
758{
759 local_lock(&cpu_fbatches.lock);
760 lru_add_drain_cpu(smp_processor_id());
761 drain_local_pages(zone);
762 local_unlock(&cpu_fbatches.lock);
763 mlock_drain_local();
764}
765
766#ifdef CONFIG_SMP
767
768static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work);
769
770static void lru_add_drain_per_cpu(struct work_struct *dummy)
771{
772 lru_add_and_bh_lrus_drain();
773}
774
775static bool cpu_needs_drain(unsigned int cpu)
776{
777 struct cpu_fbatches *fbatches = &per_cpu(cpu_fbatches, cpu);
778
779 /* Check these in order of likelihood that they're not zero */
780 return folio_batch_count(fbatch: &fbatches->lru_add) ||
781 folio_batch_count(fbatch: &fbatches->lru_move_tail) ||
782 folio_batch_count(fbatch: &fbatches->lru_deactivate_file) ||
783 folio_batch_count(fbatch: &fbatches->lru_deactivate) ||
784 folio_batch_count(fbatch: &fbatches->lru_lazyfree) ||
785 folio_batch_count(fbatch: &fbatches->lru_activate) ||
786 need_mlock_drain(cpu) ||
787 has_bh_in_lru(cpu, NULL);
788}
789
790/*
791 * Doesn't need any cpu hotplug locking because we do rely on per-cpu
792 * kworkers being shut down before our page_alloc_cpu_dead callback is
793 * executed on the offlined cpu.
794 * Calling this function with cpu hotplug locks held can actually lead
795 * to obscure indirect dependencies via WQ context.
796 */
797static inline void __lru_add_drain_all(bool force_all_cpus)
798{
799 /*
800 * lru_drain_gen - Global pages generation number
801 *
802 * (A) Definition: global lru_drain_gen = x implies that all generations
803 * 0 < n <= x are already *scheduled* for draining.
804 *
805 * This is an optimization for the highly-contended use case where a
806 * user space workload keeps constantly generating a flow of pages for
807 * each CPU.
808 */
809 static unsigned int lru_drain_gen;
810 static struct cpumask has_work;
811 static DEFINE_MUTEX(lock);
812 unsigned cpu, this_gen;
813
814 /*
815 * Make sure nobody triggers this path before mm_percpu_wq is fully
816 * initialized.
817 */
818 if (WARN_ON(!mm_percpu_wq))
819 return;
820
821 /*
822 * Guarantee folio_batch counter stores visible by this CPU
823 * are visible to other CPUs before loading the current drain
824 * generation.
825 */
826 smp_mb();
827
828 /*
829 * (B) Locally cache global LRU draining generation number
830 *
831 * The read barrier ensures that the counter is loaded before the mutex
832 * is taken. It pairs with smp_mb() inside the mutex critical section
833 * at (D).
834 */
835 this_gen = smp_load_acquire(&lru_drain_gen);
836
837 /* It helps everyone if we do our own local drain immediately. */
838 lru_add_drain();
839
840 mutex_lock(lock: &lock);
841
842 /*
843 * (C) Exit the draining operation if a newer generation, from another
844 * lru_add_drain_all(), was already scheduled for draining. Check (A).
845 */
846 if (unlikely(this_gen != lru_drain_gen && !force_all_cpus))
847 goto done;
848
849 /*
850 * (D) Increment global generation number
851 *
852 * Pairs with smp_load_acquire() at (B), outside of the critical
853 * section. Use a full memory barrier to guarantee that the
854 * new global drain generation number is stored before loading
855 * folio_batch counters.
856 *
857 * This pairing must be done here, before the for_each_online_cpu loop
858 * below which drains the page vectors.
859 *
860 * Let x, y, and z represent some system CPU numbers, where x < y < z.
861 * Assume CPU #z is in the middle of the for_each_online_cpu loop
862 * below and has already reached CPU #y's per-cpu data. CPU #x comes
863 * along, adds some pages to its per-cpu vectors, then calls
864 * lru_add_drain_all().
865 *
866 * If the paired barrier is done at any later step, e.g. after the
867 * loop, CPU #x will just exit at (C) and miss flushing out all of its
868 * added pages.
869 */
870 WRITE_ONCE(lru_drain_gen, lru_drain_gen + 1);
871 smp_mb();
872
873 cpumask_clear(dstp: &has_work);
874 for_each_online_cpu(cpu) {
875 struct work_struct *work = &per_cpu(lru_add_drain_work, cpu);
876
877 if (cpu_needs_drain(cpu)) {
878 INIT_WORK(work, lru_add_drain_per_cpu);
879 queue_work_on(cpu, wq: mm_percpu_wq, work);
880 __cpumask_set_cpu(cpu, dstp: &has_work);
881 }
882 }
883
884 for_each_cpu(cpu, &has_work)
885 flush_work(work: &per_cpu(lru_add_drain_work, cpu));
886
887done:
888 mutex_unlock(lock: &lock);
889}
890
891void lru_add_drain_all(void)
892{
893 __lru_add_drain_all(force_all_cpus: false);
894}
895#else
896void lru_add_drain_all(void)
897{
898 lru_add_drain();
899}
900#endif /* CONFIG_SMP */
901
902atomic_t lru_disable_count = ATOMIC_INIT(0);
903
904/*
905 * lru_cache_disable() needs to be called before we start compiling
906 * a list of folios to be migrated using folio_isolate_lru().
907 * It drains folios on LRU cache and then disable on all cpus until
908 * lru_cache_enable is called.
909 *
910 * Must be paired with a call to lru_cache_enable().
911 */
912void lru_cache_disable(void)
913{
914 atomic_inc(v: &lru_disable_count);
915 /*
916 * Readers of lru_disable_count are protected by either disabling
917 * preemption or rcu_read_lock:
918 *
919 * preempt_disable, local_irq_disable [bh_lru_lock()]
920 * rcu_read_lock [rt_spin_lock CONFIG_PREEMPT_RT]
921 * preempt_disable [local_lock !CONFIG_PREEMPT_RT]
922 *
923 * Since v5.1 kernel, synchronize_rcu() is guaranteed to wait on
924 * preempt_disable() regions of code. So any CPU which sees
925 * lru_disable_count = 0 will have exited the critical
926 * section when synchronize_rcu() returns.
927 */
928 synchronize_rcu_expedited();
929#ifdef CONFIG_SMP
930 __lru_add_drain_all(force_all_cpus: true);
931#else
932 lru_add_and_bh_lrus_drain();
933#endif
934}
935
936/**
937 * folios_put_refs - Reduce the reference count on a batch of folios.
938 * @folios: The folios.
939 * @refs: The number of refs to subtract from each folio.
940 *
941 * Like folio_put(), but for a batch of folios. This is more efficient
942 * than writing the loop yourself as it will optimise the locks which need
943 * to be taken if the folios are freed. The folios batch is returned
944 * empty and ready to be reused for another batch; there is no need
945 * to reinitialise it. If @refs is NULL, we subtract one from each
946 * folio refcount.
947 *
948 * Context: May be called in process or interrupt context, but not in NMI
949 * context. May be called while holding a spinlock.
950 */
951void folios_put_refs(struct folio_batch *folios, unsigned int *refs)
952{
953 int i, j;
954 struct lruvec *lruvec = NULL;
955 unsigned long flags = 0;
956
957 for (i = 0, j = 0; i < folios->nr; i++) {
958 struct folio *folio = folios->folios[i];
959 unsigned int nr_refs = refs ? refs[i] : 1;
960
961 if (is_huge_zero_folio(folio))
962 continue;
963
964 if (folio_is_zone_device(folio)) {
965 if (lruvec) {
966 unlock_page_lruvec_irqrestore(lruvec, flags);
967 lruvec = NULL;
968 }
969 if (folio_ref_sub_and_test(folio, nr: nr_refs))
970 free_zone_device_folio(folio);
971 continue;
972 }
973
974 if (!folio_ref_sub_and_test(folio, nr: nr_refs))
975 continue;
976
977 /* hugetlb has its own memcg */
978 if (folio_test_hugetlb(folio)) {
979 if (lruvec) {
980 unlock_page_lruvec_irqrestore(lruvec, flags);
981 lruvec = NULL;
982 }
983 free_huge_folio(folio);
984 continue;
985 }
986 folio_unqueue_deferred_split(folio);
987 __page_cache_release(folio, lruvecp: &lruvec, flagsp: &flags);
988
989 if (j != i)
990 folios->folios[j] = folio;
991 j++;
992 }
993 if (lruvec)
994 unlock_page_lruvec_irqrestore(lruvec, flags);
995 if (!j) {
996 folio_batch_reinit(fbatch: folios);
997 return;
998 }
999
1000 folios->nr = j;
1001 mem_cgroup_uncharge_folios(folios);
1002 free_unref_folios(fbatch: folios);
1003}
1004EXPORT_SYMBOL(folios_put_refs);
1005
1006/**
1007 * release_pages - batched put_page()
1008 * @arg: array of pages to release
1009 * @nr: number of pages
1010 *
1011 * Decrement the reference count on all the pages in @arg. If it
1012 * fell to zero, remove the page from the LRU and free it.
1013 *
1014 * Note that the argument can be an array of pages, encoded pages,
1015 * or folio pointers. We ignore any encoded bits, and turn any of
1016 * them into just a folio that gets free'd.
1017 */
1018void release_pages(release_pages_arg arg, int nr)
1019{
1020 struct folio_batch fbatch;
1021 int refs[PAGEVEC_SIZE];
1022 struct encoded_page **encoded = arg.encoded_pages;
1023 int i;
1024
1025 folio_batch_init(fbatch: &fbatch);
1026 for (i = 0; i < nr; i++) {
1027 /* Turn any of the argument types into a folio */
1028 struct folio *folio = page_folio(encoded_page_ptr(encoded[i]));
1029
1030 /* Is our next entry actually "nr_pages" -> "nr_refs" ? */
1031 refs[fbatch.nr] = 1;
1032 if (unlikely(encoded_page_flags(encoded[i]) &
1033 ENCODED_PAGE_BIT_NR_PAGES_NEXT))
1034 refs[fbatch.nr] = encoded_nr_pages(page: encoded[++i]);
1035
1036 if (folio_batch_add(fbatch: &fbatch, folio) > 0)
1037 continue;
1038 folios_put_refs(&fbatch, refs);
1039 }
1040
1041 if (fbatch.nr)
1042 folios_put_refs(&fbatch, refs);
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 folios_put(folios: fbatch);
1063}
1064EXPORT_SYMBOL(__folio_batch_release);
1065
1066/**
1067 * folio_batch_remove_exceptionals() - Prune non-folios from a batch.
1068 * @fbatch: The batch to prune
1069 *
1070 * find_get_entries() fills a batch with both folios and shadow/swap/DAX
1071 * entries. This function prunes all the non-folio entries from @fbatch
1072 * without leaving holes, so that it can be passed on to folio-only batch
1073 * operations.
1074 */
1075void folio_batch_remove_exceptionals(struct folio_batch *fbatch)
1076{
1077 unsigned int i, j;
1078
1079 for (i = 0, j = 0; i < folio_batch_count(fbatch); i++) {
1080 struct folio *folio = fbatch->folios[i];
1081 if (!xa_is_value(entry: folio))
1082 fbatch->folios[j++] = folio;
1083 }
1084 fbatch->nr = j;
1085}
1086
1087static const struct ctl_table swap_sysctl_table[] = {
1088 {
1089 .procname = "page-cluster",
1090 .data = &page_cluster,
1091 .maxlen = sizeof(int),
1092 .mode = 0644,
1093 .proc_handler = proc_dointvec_minmax,
1094 .extra1 = SYSCTL_ZERO,
1095 .extra2 = (void *)&page_cluster_max,
1096 }
1097};
1098
1099/*
1100 * Perform any setup for the swap system
1101 */
1102void __init swap_setup(void)
1103{
1104 unsigned long megs = PAGES_TO_MB(totalram_pages());
1105
1106 /* Use a smaller cluster for small-memory machines */
1107 if (megs < 16)
1108 page_cluster = 2;
1109 else
1110 page_cluster = 3;
1111 /*
1112 * Right now other parts of the system means that we
1113 * _really_ don't want to cluster much more
1114 */
1115
1116 register_sysctl_init("vm", swap_sysctl_table);
1117}
1118