Line data Source code
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 */
47 : int page_cluster;
48 : const int page_cluster_max = 31;
49 :
50 : /* Protecting only lru_rotate.fbatch which requires disabling interrupts */
51 : struct lru_rotate {
52 : local_lock_t lock;
53 : struct folio_batch fbatch;
54 : };
55 : static 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 : */
63 : struct 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 : };
73 : static 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 : */
81 0 : static void __page_cache_release(struct folio *folio)
82 : {
83 0 : if (folio_test_lru(folio)) {
84 : struct lruvec *lruvec;
85 : unsigned long flags;
86 :
87 0 : lruvec = folio_lruvec_lock_irqsave(folio, &flags);
88 0 : lruvec_del_folio(lruvec, folio);
89 0 : __folio_clear_lru_flags(folio);
90 0 : unlock_page_lruvec_irqrestore(lruvec, flags);
91 : }
92 : /* See comment on folio_test_mlocked in release_pages() */
93 0 : if (unlikely(folio_test_mlocked(folio))) {
94 0 : long nr_pages = folio_nr_pages(folio);
95 :
96 0 : __folio_clear_mlocked(folio);
97 0 : zone_stat_mod_folio(folio, NR_MLOCK, -nr_pages);
98 0 : count_vm_events(UNEVICTABLE_PGCLEARED, nr_pages);
99 : }
100 0 : }
101 :
102 : static void __folio_put_small(struct folio *folio)
103 : {
104 0 : __page_cache_release(folio);
105 0 : mem_cgroup_uncharge(folio);
106 0 : free_unref_page(&folio->page, 0);
107 : }
108 :
109 : static 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 0 : if (!folio_test_hugetlb(folio))
118 0 : __page_cache_release(folio);
119 0 : destroy_large_folio(folio);
120 : }
121 :
122 0 : void __folio_put(struct folio *folio)
123 : {
124 0 : if (unlikely(folio_is_zone_device(folio)))
125 : free_zone_device_page(&folio->page);
126 0 : else if (unlikely(folio_test_large(folio)))
127 : __folio_put_large(folio);
128 : else
129 : __folio_put_small(folio);
130 0 : }
131 : EXPORT_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 : */
139 0 : void put_pages_list(struct list_head *pages)
140 : {
141 : struct folio *folio, *next;
142 :
143 0 : list_for_each_entry_safe(folio, next, pages, lru) {
144 0 : if (!folio_put_testzero(folio)) {
145 0 : list_del(&folio->lru);
146 0 : continue;
147 : }
148 0 : if (folio_test_large(folio)) {
149 0 : list_del(&folio->lru);
150 0 : __folio_put_large(folio);
151 0 : continue;
152 : }
153 : /* LRU flag must be clear because it's passed using the lru */
154 : }
155 :
156 0 : free_unref_page_list(pages);
157 0 : INIT_LIST_HEAD(pages);
158 0 : }
159 : EXPORT_SYMBOL(put_pages_list);
160 :
161 : typedef void (*move_fn_t)(struct lruvec *lruvec, struct folio *folio);
162 :
163 0 : static void lru_add_fn(struct lruvec *lruvec, struct folio *folio)
164 : {
165 0 : int was_unevictable = folio_test_clear_unevictable(folio);
166 0 : 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 0 : if (folio_evictable(folio)) {
182 0 : if (was_unevictable)
183 : __count_vm_events(UNEVICTABLE_PGRESCUED, nr_pages);
184 : } else {
185 0 : folio_clear_active(folio);
186 0 : 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 0 : folio->mlock_count = 0;
195 0 : if (!was_unevictable)
196 : __count_vm_events(UNEVICTABLE_PGCULLED, nr_pages);
197 : }
198 :
199 0 : lruvec_add_folio(lruvec, folio);
200 0 : trace_mm_lru_insertion(folio);
201 0 : }
202 :
203 0 : static void folio_batch_move_lru(struct folio_batch *fbatch, move_fn_t move_fn)
204 : {
205 : int i;
206 0 : struct lruvec *lruvec = NULL;
207 0 : unsigned long flags = 0;
208 :
209 0 : for (i = 0; i < folio_batch_count(fbatch); i++) {
210 0 : struct folio *folio = fbatch->folios[i];
211 :
212 : /* block memcg migration while the folio moves between lru */
213 0 : if (move_fn != lru_add_fn && !folio_test_clear_lru(folio))
214 0 : continue;
215 :
216 0 : lruvec = folio_lruvec_relock_irqsave(folio, lruvec, &flags);
217 0 : move_fn(lruvec, folio);
218 :
219 : folio_set_lru(folio);
220 : }
221 :
222 0 : if (lruvec)
223 0 : unlock_page_lruvec_irqrestore(lruvec, flags);
224 0 : folios_put(fbatch->folios, folio_batch_count(fbatch));
225 0 : folio_batch_reinit(fbatch);
226 0 : }
227 :
228 0 : static void folio_batch_add_and_move(struct folio_batch *fbatch,
229 : struct folio *folio, move_fn_t move_fn)
230 : {
231 0 : if (folio_batch_add(fbatch, folio) && !folio_test_large(folio) &&
232 : !lru_cache_disabled())
233 : return;
234 0 : folio_batch_move_lru(fbatch, move_fn);
235 : }
236 :
237 0 : static void lru_move_tail_fn(struct lruvec *lruvec, struct folio *folio)
238 : {
239 0 : if (!folio_test_unevictable(folio)) {
240 0 : lruvec_del_folio(lruvec, folio);
241 0 : folio_clear_active(folio);
242 0 : lruvec_add_folio_tail(lruvec, folio);
243 0 : __count_vm_events(PGROTATED, folio_nr_pages(folio));
244 : }
245 0 : }
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 : */
254 0 : void folio_rotate_reclaimable(struct folio *folio)
255 : {
256 0 : if (!folio_test_locked(folio) && !folio_test_dirty(folio) &&
257 0 : !folio_test_unevictable(folio) && folio_test_lru(folio)) {
258 : struct folio_batch *fbatch;
259 : unsigned long flags;
260 :
261 0 : folio_get(folio);
262 0 : local_lock_irqsave(&lru_rotate.lock, flags);
263 0 : fbatch = this_cpu_ptr(&lru_rotate.fbatch);
264 0 : folio_batch_add_and_move(fbatch, folio, lru_move_tail_fn);
265 0 : local_unlock_irqrestore(&lru_rotate.lock, flags);
266 : }
267 0 : }
268 :
269 0 : void 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 0 : 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 0 : spin_lock_irq(&lruvec->lru_lock);
294 : /* Record cost event */
295 0 : if (file)
296 0 : lruvec->file_cost += cost;
297 : else
298 0 : 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 0 : lrusize = lruvec_page_state(lruvec, NR_INACTIVE_ANON) +
309 0 : lruvec_page_state(lruvec, NR_ACTIVE_ANON) +
310 0 : lruvec_page_state(lruvec, NR_INACTIVE_FILE) +
311 0 : lruvec_page_state(lruvec, NR_ACTIVE_FILE);
312 :
313 0 : if (lruvec->file_cost + lruvec->anon_cost > lrusize / 4) {
314 0 : lruvec->file_cost /= 2;
315 0 : lruvec->anon_cost /= 2;
316 : }
317 0 : spin_unlock_irq(&lruvec->lru_lock);
318 0 : } while ((lruvec = parent_lruvec(lruvec)));
319 0 : }
320 :
321 0 : void lru_note_cost_refault(struct folio *folio)
322 : {
323 0 : lru_note_cost(folio_lruvec(folio), folio_is_file_lru(folio),
324 0 : folio_nr_pages(folio), 0);
325 0 : }
326 :
327 0 : static void folio_activate_fn(struct lruvec *lruvec, struct folio *folio)
328 : {
329 0 : if (!folio_test_active(folio) && !folio_test_unevictable(folio)) {
330 0 : long nr_pages = folio_nr_pages(folio);
331 :
332 0 : lruvec_del_folio(lruvec, folio);
333 0 : folio_set_active(folio);
334 0 : lruvec_add_folio(lruvec, folio);
335 0 : trace_mm_lru_activate(folio);
336 :
337 0 : __count_vm_events(PGACTIVATE, nr_pages);
338 0 : __count_memcg_events(lruvec_memcg(lruvec), PGACTIVATE,
339 : nr_pages);
340 : }
341 0 : }
342 :
343 : #ifdef CONFIG_SMP
344 : static 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, folio_activate_fn);
350 : }
351 :
352 : void 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, folio_activate_fn);
362 : local_unlock(&cpu_fbatches.lock);
363 : }
364 : }
365 :
366 : #else
367 : static inline void folio_activate_drain(int cpu)
368 : {
369 : }
370 :
371 0 : void folio_activate(struct folio *folio)
372 : {
373 : struct lruvec *lruvec;
374 :
375 0 : if (folio_test_clear_lru(folio)) {
376 0 : lruvec = folio_lruvec_lock_irq(folio);
377 0 : folio_activate_fn(lruvec, folio);
378 0 : unlock_page_lruvec_irq(lruvec);
379 : folio_set_lru(folio);
380 : }
381 0 : }
382 : #endif
383 :
384 : static void __lru_cache_activate_folio(struct folio *folio)
385 : {
386 : struct folio_batch *fbatch;
387 : int i;
388 :
389 0 : local_lock(&cpu_fbatches.lock);
390 0 : 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 0 : for (i = folio_batch_count(fbatch) - 1; i >= 0; i--) {
403 0 : struct folio *batch_folio = fbatch->folios[i];
404 :
405 0 : if (batch_folio == folio) {
406 : folio_set_active(folio);
407 : break;
408 : }
409 : }
410 :
411 0 : local_unlock(&cpu_fbatches.lock);
412 : }
413 :
414 : #ifdef CONFIG_LRU_GEN
415 : static 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
443 : static 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 : */
458 0 : void folio_mark_accessed(struct folio *folio)
459 : {
460 : if (lru_gen_enabled()) {
461 : folio_inc_refs(folio);
462 : return;
463 : }
464 :
465 0 : if (!folio_test_referenced(folio)) {
466 : folio_set_referenced(folio);
467 0 : } 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 0 : } 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 0 : if (folio_test_lru(folio))
481 0 : folio_activate(folio);
482 : else
483 : __lru_cache_activate_folio(folio);
484 0 : folio_clear_referenced(folio);
485 0 : workingset_activation(folio);
486 : }
487 0 : if (folio_test_idle(folio))
488 : folio_clear_idle(folio);
489 : }
490 : EXPORT_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 : */
501 0 : void 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 0 : folio_get(folio);
515 0 : local_lock(&cpu_fbatches.lock);
516 0 : fbatch = this_cpu_ptr(&cpu_fbatches.lru_add);
517 0 : folio_batch_add_and_move(fbatch, folio, lru_add_fn);
518 0 : local_unlock(&cpu_fbatches.lock);
519 0 : }
520 : EXPORT_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 : */
530 0 : void 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 0 : if (unlikely((vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) == VM_LOCKED))
535 0 : mlock_new_folio(folio);
536 : else
537 : folio_add_lru(folio);
538 0 : }
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 : */
561 0 : static void lru_deactivate_file_fn(struct lruvec *lruvec, struct folio *folio)
562 : {
563 0 : bool active = folio_test_active(folio);
564 0 : long nr_pages = folio_nr_pages(folio);
565 :
566 0 : if (folio_test_unevictable(folio))
567 : return;
568 :
569 : /* Some processes are using the folio */
570 0 : if (folio_mapped(folio))
571 : return;
572 :
573 0 : lruvec_del_folio(lruvec, folio);
574 0 : folio_clear_active(folio);
575 0 : folio_clear_referenced(folio);
576 :
577 0 : 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 0 : 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 0 : lruvec_add_folio_tail(lruvec, folio);
592 : __count_vm_events(PGROTATED, nr_pages);
593 : }
594 :
595 0 : if (active) {
596 0 : __count_vm_events(PGDEACTIVATE, nr_pages);
597 0 : __count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE,
598 : nr_pages);
599 : }
600 : }
601 :
602 0 : static void lru_deactivate_fn(struct lruvec *lruvec, struct folio *folio)
603 : {
604 0 : if (!folio_test_unevictable(folio) && (folio_test_active(folio) || lru_gen_enabled())) {
605 0 : long nr_pages = folio_nr_pages(folio);
606 :
607 0 : lruvec_del_folio(lruvec, folio);
608 0 : folio_clear_active(folio);
609 0 : folio_clear_referenced(folio);
610 0 : lruvec_add_folio(lruvec, folio);
611 :
612 0 : __count_vm_events(PGDEACTIVATE, nr_pages);
613 0 : __count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE,
614 : nr_pages);
615 : }
616 0 : }
617 :
618 0 : static void lru_lazyfree_fn(struct lruvec *lruvec, struct folio *folio)
619 : {
620 0 : if (folio_test_anon(folio) && folio_test_swapbacked(folio) &&
621 0 : !folio_test_swapcache(folio) && !folio_test_unevictable(folio)) {
622 0 : long nr_pages = folio_nr_pages(folio);
623 :
624 0 : lruvec_del_folio(lruvec, folio);
625 0 : folio_clear_active(folio);
626 0 : 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 0 : folio_clear_swapbacked(folio);
633 0 : lruvec_add_folio(lruvec, folio);
634 :
635 0 : __count_vm_events(PGLAZYFREE, nr_pages);
636 0 : __count_memcg_events(lruvec_memcg(lruvec), PGLAZYFREE,
637 : nr_pages);
638 : }
639 0 : }
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 : */
646 0 : void lru_add_drain_cpu(int cpu)
647 : {
648 0 : struct cpu_fbatches *fbatches = &per_cpu(cpu_fbatches, cpu);
649 0 : struct folio_batch *fbatch = &fbatches->lru_add;
650 :
651 0 : if (folio_batch_count(fbatch))
652 0 : folio_batch_move_lru(fbatch, lru_add_fn);
653 :
654 0 : fbatch = &per_cpu(lru_rotate.fbatch, cpu);
655 : /* Disabling interrupts below acts as a compiler barrier. */
656 0 : if (data_race(folio_batch_count(fbatch))) {
657 : unsigned long flags;
658 :
659 : /* No harm done if a racing interrupt already did this */
660 0 : local_lock_irqsave(&lru_rotate.lock, flags);
661 0 : folio_batch_move_lru(fbatch, lru_move_tail_fn);
662 0 : local_unlock_irqrestore(&lru_rotate.lock, flags);
663 : }
664 :
665 0 : fbatch = &fbatches->lru_deactivate_file;
666 0 : if (folio_batch_count(fbatch))
667 0 : folio_batch_move_lru(fbatch, lru_deactivate_file_fn);
668 :
669 0 : fbatch = &fbatches->lru_deactivate;
670 0 : if (folio_batch_count(fbatch))
671 0 : folio_batch_move_lru(fbatch, lru_deactivate_fn);
672 :
673 0 : fbatch = &fbatches->lru_lazyfree;
674 0 : if (folio_batch_count(fbatch))
675 0 : folio_batch_move_lru(fbatch, lru_lazyfree_fn);
676 :
677 0 : folio_activate_drain(cpu);
678 0 : }
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 : */
690 0 : void deactivate_file_folio(struct folio *folio)
691 : {
692 : struct folio_batch *fbatch;
693 :
694 : /* Deactivating an unevictable folio will not accelerate reclaim */
695 0 : if (folio_test_unevictable(folio))
696 : return;
697 :
698 0 : folio_get(folio);
699 0 : local_lock(&cpu_fbatches.lock);
700 0 : fbatch = this_cpu_ptr(&cpu_fbatches.lru_deactivate_file);
701 0 : folio_batch_add_and_move(fbatch, folio, lru_deactivate_file_fn);
702 0 : 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 : */
713 0 : void folio_deactivate(struct folio *folio)
714 : {
715 0 : if (folio_test_lru(folio) && !folio_test_unevictable(folio) &&
716 0 : (folio_test_active(folio) || lru_gen_enabled())) {
717 : struct folio_batch *fbatch;
718 :
719 0 : folio_get(folio);
720 0 : local_lock(&cpu_fbatches.lock);
721 0 : fbatch = this_cpu_ptr(&cpu_fbatches.lru_deactivate);
722 0 : folio_batch_add_and_move(fbatch, folio, lru_deactivate_fn);
723 0 : local_unlock(&cpu_fbatches.lock);
724 : }
725 0 : }
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 : */
734 0 : void folio_mark_lazyfree(struct folio *folio)
735 : {
736 0 : if (folio_test_lru(folio) && folio_test_anon(folio) &&
737 0 : folio_test_swapbacked(folio) && !folio_test_swapcache(folio) &&
738 0 : !folio_test_unevictable(folio)) {
739 : struct folio_batch *fbatch;
740 :
741 0 : folio_get(folio);
742 0 : local_lock(&cpu_fbatches.lock);
743 0 : fbatch = this_cpu_ptr(&cpu_fbatches.lru_lazyfree);
744 0 : folio_batch_add_and_move(fbatch, folio, lru_lazyfree_fn);
745 0 : local_unlock(&cpu_fbatches.lock);
746 : }
747 0 : }
748 :
749 0 : void lru_add_drain(void)
750 : {
751 0 : local_lock(&cpu_fbatches.lock);
752 0 : lru_add_drain_cpu(smp_processor_id());
753 0 : local_unlock(&cpu_fbatches.lock);
754 0 : mlock_drain_local();
755 0 : }
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 : */
763 : static void lru_add_and_bh_lrus_drain(void)
764 : {
765 0 : local_lock(&cpu_fbatches.lock);
766 0 : lru_add_drain_cpu(smp_processor_id());
767 0 : local_unlock(&cpu_fbatches.lock);
768 0 : invalidate_bh_lrus_cpu();
769 0 : mlock_drain_local();
770 : }
771 :
772 0 : void lru_add_drain_cpu_zone(struct zone *zone)
773 : {
774 0 : local_lock(&cpu_fbatches.lock);
775 0 : lru_add_drain_cpu(smp_processor_id());
776 0 : drain_local_pages(zone);
777 0 : local_unlock(&cpu_fbatches.lock);
778 0 : mlock_drain_local();
779 0 : }
780 :
781 : #ifdef CONFIG_SMP
782 :
783 : static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work);
784 :
785 : static void lru_add_drain_per_cpu(struct work_struct *dummy)
786 : {
787 : lru_add_and_bh_lrus_drain();
788 : }
789 :
790 : static 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(&fbatches->lru_add) ||
796 : data_race(folio_batch_count(&per_cpu(lru_rotate.fbatch, cpu))) ||
797 : folio_batch_count(&fbatches->lru_deactivate_file) ||
798 : folio_batch_count(&fbatches->lru_deactivate) ||
799 : folio_batch_count(&fbatches->lru_lazyfree) ||
800 : folio_batch_count(&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 : */
812 : static 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(&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, mm_percpu_wq, work);
892 : __cpumask_set_cpu(cpu, &has_work);
893 : }
894 : }
895 :
896 : for_each_cpu(cpu, &has_work)
897 : flush_work(&per_cpu(lru_add_drain_work, cpu));
898 :
899 : done:
900 : mutex_unlock(&lock);
901 : }
902 :
903 : void lru_add_drain_all(void)
904 : {
905 : __lru_add_drain_all(false);
906 : }
907 : #else
908 0 : void lru_add_drain_all(void)
909 : {
910 : lru_add_drain();
911 0 : }
912 : #endif /* CONFIG_SMP */
913 :
914 : atomic_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 : */
924 0 : void lru_cache_disable(void)
925 : {
926 0 : atomic_inc(&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(true);
943 : #else
944 : lru_add_and_bh_lrus_drain();
945 : #endif
946 0 : }
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 : */
960 0 : void release_pages(release_pages_arg arg, int nr)
961 : {
962 : int i;
963 0 : struct encoded_page **encoded = arg.encoded_pages;
964 0 : LIST_HEAD(pages_to_free);
965 0 : struct lruvec *lruvec = NULL;
966 0 : unsigned long flags = 0;
967 : unsigned int lock_batch;
968 :
969 0 : for (i = 0; i < nr; i++) {
970 : struct folio *folio;
971 :
972 : /* Turn any of the argument types into a folio */
973 0 : 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 0 : if (lruvec && ++lock_batch == SWAP_CLUSTER_MAX) {
981 0 : unlock_page_lruvec_irqrestore(lruvec, flags);
982 0 : lruvec = NULL;
983 : }
984 :
985 0 : if (is_huge_zero_page(&folio->page))
986 : continue;
987 :
988 0 : 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(&folio->page))
994 : continue;
995 : if (folio_put_testzero(folio))
996 : free_zone_device_page(&folio->page);
997 : continue;
998 : }
999 :
1000 0 : if (!folio_put_testzero(folio))
1001 0 : continue;
1002 :
1003 0 : if (folio_test_large(folio)) {
1004 0 : if (lruvec) {
1005 0 : unlock_page_lruvec_irqrestore(lruvec, flags);
1006 0 : lruvec = NULL;
1007 : }
1008 0 : __folio_put_large(folio);
1009 0 : continue;
1010 : }
1011 :
1012 0 : if (folio_test_lru(folio)) {
1013 0 : struct lruvec *prev_lruvec = lruvec;
1014 :
1015 0 : lruvec = folio_lruvec_relock_irqsave(folio, lruvec,
1016 : &flags);
1017 0 : if (prev_lruvec != lruvec)
1018 0 : lock_batch = 0;
1019 :
1020 0 : 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 0 : if (unlikely(folio_test_mlocked(folio))) {
1031 0 : __folio_clear_mlocked(folio);
1032 0 : zone_stat_sub_folio(folio, NR_MLOCK);
1033 0 : count_vm_event(UNEVICTABLE_PGCLEARED);
1034 : }
1035 :
1036 0 : list_add(&folio->lru, &pages_to_free);
1037 : }
1038 0 : if (lruvec)
1039 0 : unlock_page_lruvec_irqrestore(lruvec, flags);
1040 :
1041 0 : mem_cgroup_uncharge_list(&pages_to_free);
1042 0 : free_unref_page_list(&pages_to_free);
1043 0 : }
1044 : EXPORT_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 : */
1056 0 : void __folio_batch_release(struct folio_batch *fbatch)
1057 : {
1058 0 : if (!fbatch->percpu_pvec_drained) {
1059 : lru_add_drain();
1060 0 : fbatch->percpu_pvec_drained = true;
1061 : }
1062 0 : release_pages(fbatch->folios, folio_batch_count(fbatch));
1063 0 : folio_batch_reinit(fbatch);
1064 0 : }
1065 : EXPORT_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 : */
1076 0 : void folio_batch_remove_exceptionals(struct folio_batch *fbatch)
1077 : {
1078 : unsigned int i, j;
1079 :
1080 0 : for (i = 0, j = 0; i < folio_batch_count(fbatch); i++) {
1081 0 : struct folio *folio = fbatch->folios[i];
1082 0 : if (!xa_is_value(folio))
1083 0 : fbatch->folios[j++] = folio;
1084 : }
1085 0 : fbatch->nr = j;
1086 0 : }
1087 :
1088 : /*
1089 : * Perform any setup for the swap system
1090 : */
1091 1 : void __init swap_setup(void)
1092 : {
1093 1 : unsigned long megs = totalram_pages() >> (20 - PAGE_SHIFT);
1094 :
1095 : /* Use a smaller cluster for small-memory machines */
1096 1 : if (megs < 16)
1097 0 : page_cluster = 2;
1098 : else
1099 1 : 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 1 : }
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