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Linux/mm/swap.c

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  1 // SPDX-License-Identifier: GPL-2.0-only
  2 /*
  3  *  linux/mm/swap.c
  4  *
  5  *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
  6  */
  7 
  8 /*
  9  * This file contains the default values for the operation of the
 10  * Linux VM subsystem. Fine-tuning documentation can be found in
 11  * Documentation/admin-guide/sysctl/vm.rst.
 12  * Started 18.12.91
 13  * Swap aging added 23.2.95, Stephen Tweedie.
 14  * Buffermem limits added 12.3.98, Rik van Riel.
 15  */
 16 
 17 #include <linux/mm.h>
 18 #include <linux/sched.h>
 19 #include <linux/kernel_stat.h>
 20 #include <linux/swap.h>
 21 #include <linux/mman.h>
 22 #include <linux/pagemap.h>
 23 #include <linux/pagevec.h>
 24 #include <linux/init.h>
 25 #include <linux/export.h>
 26 #include <linux/mm_inline.h>
 27 #include <linux/percpu_counter.h>
 28 #include <linux/memremap.h>
 29 #include <linux/percpu.h>
 30 #include <linux/cpu.h>
 31 #include <linux/notifier.h>
 32 #include <linux/backing-dev.h>
 33 #include <linux/memcontrol.h>
 34 #include <linux/gfp.h>
 35 #include <linux/uio.h>
 36 #include <linux/hugetlb.h>
 37 #include <linux/page_idle.h>
 38 #include <linux/local_lock.h>
 39 
 40 #include "internal.h"
 41 
 42 #define CREATE_TRACE_POINTS
 43 #include <trace/events/pagemap.h>
 44 
 45 /* How many pages do we try to swap or page in/out together? */
 46 int page_cluster;
 47 
 48 /* Protecting only lru_rotate.pvec which requires disabling interrupts */
 49 struct lru_rotate {
 50         local_lock_t lock;
 51         struct pagevec pvec;
 52 };
 53 static DEFINE_PER_CPU(struct lru_rotate, lru_rotate) = {
 54         .lock = INIT_LOCAL_LOCK(lock),
 55 };
 56 
 57 /*
 58  * The following struct pagevec are grouped together because they are protected
 59  * by disabling preemption (and interrupts remain enabled).
 60  */
 61 struct lru_pvecs {
 62         local_lock_t lock;
 63         struct pagevec lru_add;
 64         struct pagevec lru_deactivate_file;
 65         struct pagevec lru_deactivate;
 66         struct pagevec lru_lazyfree;
 67 #ifdef CONFIG_SMP
 68         struct pagevec activate_page;
 69 #endif
 70 };
 71 static DEFINE_PER_CPU(struct lru_pvecs, lru_pvecs) = {
 72         .lock = INIT_LOCAL_LOCK(lock),
 73 };
 74 
 75 /*
 76  * This path almost never happens for VM activity - pages are normally
 77  * freed via pagevecs.  But it gets used by networking.
 78  */
 79 static void __page_cache_release(struct page *page)
 80 {
 81         if (PageLRU(page)) {
 82                 pg_data_t *pgdat = page_pgdat(page);
 83                 struct lruvec *lruvec;
 84                 unsigned long flags;
 85 
 86                 spin_lock_irqsave(&pgdat->lru_lock, flags);
 87                 lruvec = mem_cgroup_page_lruvec(page, pgdat);
 88                 VM_BUG_ON_PAGE(!PageLRU(page), page);
 89                 __ClearPageLRU(page);
 90                 del_page_from_lru_list(page, lruvec, page_off_lru(page));
 91                 spin_unlock_irqrestore(&pgdat->lru_lock, flags);
 92         }
 93         __ClearPageWaiters(page);
 94 }
 95 
 96 static void __put_single_page(struct page *page)
 97 {
 98         __page_cache_release(page);
 99         mem_cgroup_uncharge(page);
100         free_unref_page(page);
101 }
102 
103 static void __put_compound_page(struct page *page)
104 {
105         /*
106          * __page_cache_release() is supposed to be called for thp, not for
107          * hugetlb. This is because hugetlb page does never have PageLRU set
108          * (it's never listed to any LRU lists) and no memcg routines should
109          * be called for hugetlb (it has a separate hugetlb_cgroup.)
110          */
111         if (!PageHuge(page))
112                 __page_cache_release(page);
113         destroy_compound_page(page);
114 }
115 
116 void __put_page(struct page *page)
117 {
118         if (is_zone_device_page(page)) {
119                 put_dev_pagemap(page->pgmap);
120 
121                 /*
122                  * The page belongs to the device that created pgmap. Do
123                  * not return it to page allocator.
124                  */
125                 return;
126         }
127 
128         if (unlikely(PageCompound(page)))
129                 __put_compound_page(page);
130         else
131                 __put_single_page(page);
132 }
133 EXPORT_SYMBOL(__put_page);
134 
135 /**
136  * put_pages_list() - release a list of pages
137  * @pages: list of pages threaded on page->lru
138  *
139  * Release a list of pages which are strung together on page.lru.  Currently
140  * used by read_cache_pages() and related error recovery code.
141  */
142 void put_pages_list(struct list_head *pages)
143 {
144         while (!list_empty(pages)) {
145                 struct page *victim;
146 
147                 victim = lru_to_page(pages);
148                 list_del(&victim->lru);
149                 put_page(victim);
150         }
151 }
152 EXPORT_SYMBOL(put_pages_list);
153 
154 /*
155  * get_kernel_pages() - pin kernel pages in memory
156  * @kiov:       An array of struct kvec structures
157  * @nr_segs:    number of segments to pin
158  * @write:      pinning for read/write, currently ignored
159  * @pages:      array that receives pointers to the pages pinned.
160  *              Should be at least nr_segs long.
161  *
162  * Returns number of pages pinned. This may be fewer than the number
163  * requested. If nr_pages is 0 or negative, returns 0. If no pages
164  * were pinned, returns -errno. Each page returned must be released
165  * with a put_page() call when it is finished with.
166  */
167 int get_kernel_pages(const struct kvec *kiov, int nr_segs, int write,
168                 struct page **pages)
169 {
170         int seg;
171 
172         for (seg = 0; seg < nr_segs; seg++) {
173                 if (WARN_ON(kiov[seg].iov_len != PAGE_SIZE))
174                         return seg;
175 
176                 pages[seg] = kmap_to_page(kiov[seg].iov_base);
177                 get_page(pages[seg]);
178         }
179 
180         return seg;
181 }
182 EXPORT_SYMBOL_GPL(get_kernel_pages);
183 
184 /*
185  * get_kernel_page() - pin a kernel page in memory
186  * @start:      starting kernel address
187  * @write:      pinning for read/write, currently ignored
188  * @pages:      array that receives pointer to the page pinned.
189  *              Must be at least nr_segs long.
190  *
191  * Returns 1 if page is pinned. If the page was not pinned, returns
192  * -errno. The page returned must be released with a put_page() call
193  * when it is finished with.
194  */
195 int get_kernel_page(unsigned long start, int write, struct page **pages)
196 {
197         const struct kvec kiov = {
198                 .iov_base = (void *)start,
199                 .iov_len = PAGE_SIZE
200         };
201 
202         return get_kernel_pages(&kiov, 1, write, pages);
203 }
204 EXPORT_SYMBOL_GPL(get_kernel_page);
205 
206 static void pagevec_lru_move_fn(struct pagevec *pvec,
207         void (*move_fn)(struct page *page, struct lruvec *lruvec, void *arg),
208         void *arg)
209 {
210         int i;
211         struct pglist_data *pgdat = NULL;
212         struct lruvec *lruvec;
213         unsigned long flags = 0;
214 
215         for (i = 0; i < pagevec_count(pvec); i++) {
216                 struct page *page = pvec->pages[i];
217                 struct pglist_data *pagepgdat = page_pgdat(page);
218 
219                 if (pagepgdat != pgdat) {
220                         if (pgdat)
221                                 spin_unlock_irqrestore(&pgdat->lru_lock, flags);
222                         pgdat = pagepgdat;
223                         spin_lock_irqsave(&pgdat->lru_lock, flags);
224                 }
225 
226                 lruvec = mem_cgroup_page_lruvec(page, pgdat);
227                 (*move_fn)(page, lruvec, arg);
228         }
229         if (pgdat)
230                 spin_unlock_irqrestore(&pgdat->lru_lock, flags);
231         release_pages(pvec->pages, pvec->nr);
232         pagevec_reinit(pvec);
233 }
234 
235 static void pagevec_move_tail_fn(struct page *page, struct lruvec *lruvec,
236                                  void *arg)
237 {
238         int *pgmoved = arg;
239 
240         if (PageLRU(page) && !PageUnevictable(page)) {
241                 del_page_from_lru_list(page, lruvec, page_lru(page));
242                 ClearPageActive(page);
243                 add_page_to_lru_list_tail(page, lruvec, page_lru(page));
244                 (*pgmoved) += thp_nr_pages(page);
245         }
246 }
247 
248 /*
249  * pagevec_move_tail() must be called with IRQ disabled.
250  * Otherwise this may cause nasty races.
251  */
252 static void pagevec_move_tail(struct pagevec *pvec)
253 {
254         int pgmoved = 0;
255 
256         pagevec_lru_move_fn(pvec, pagevec_move_tail_fn, &pgmoved);
257         __count_vm_events(PGROTATED, pgmoved);
258 }
259 
260 /*
261  * Writeback is about to end against a page which has been marked for immediate
262  * reclaim.  If it still appears to be reclaimable, move it to the tail of the
263  * inactive list.
264  */
265 void rotate_reclaimable_page(struct page *page)
266 {
267         if (!PageLocked(page) && !PageDirty(page) &&
268             !PageUnevictable(page) && PageLRU(page)) {
269                 struct pagevec *pvec;
270                 unsigned long flags;
271 
272                 get_page(page);
273                 local_lock_irqsave(&lru_rotate.lock, flags);
274                 pvec = this_cpu_ptr(&lru_rotate.pvec);
275                 if (!pagevec_add(pvec, page) || PageCompound(page))
276                         pagevec_move_tail(pvec);
277                 local_unlock_irqrestore(&lru_rotate.lock, flags);
278         }
279 }
280 
281 void lru_note_cost(struct lruvec *lruvec, bool file, unsigned int nr_pages)
282 {
283         do {
284                 unsigned long lrusize;
285 
286                 /* Record cost event */
287                 if (file)
288                         lruvec->file_cost += nr_pages;
289                 else
290                         lruvec->anon_cost += nr_pages;
291 
292                 /*
293                  * Decay previous events
294                  *
295                  * Because workloads change over time (and to avoid
296                  * overflow) we keep these statistics as a floating
297                  * average, which ends up weighing recent refaults
298                  * more than old ones.
299                  */
300                 lrusize = lruvec_page_state(lruvec, NR_INACTIVE_ANON) +
301                           lruvec_page_state(lruvec, NR_ACTIVE_ANON) +
302                           lruvec_page_state(lruvec, NR_INACTIVE_FILE) +
303                           lruvec_page_state(lruvec, NR_ACTIVE_FILE);
304 
305                 if (lruvec->file_cost + lruvec->anon_cost > lrusize / 4) {
306                         lruvec->file_cost /= 2;
307                         lruvec->anon_cost /= 2;
308                 }
309         } while ((lruvec = parent_lruvec(lruvec)));
310 }
311 
312 void lru_note_cost_page(struct page *page)
313 {
314         lru_note_cost(mem_cgroup_page_lruvec(page, page_pgdat(page)),
315                       page_is_file_lru(page), thp_nr_pages(page));
316 }
317 
318 static void __activate_page(struct page *page, struct lruvec *lruvec,
319                             void *arg)
320 {
321         if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
322                 int lru = page_lru_base_type(page);
323                 int nr_pages = thp_nr_pages(page);
324 
325                 del_page_from_lru_list(page, lruvec, lru);
326                 SetPageActive(page);
327                 lru += LRU_ACTIVE;
328                 add_page_to_lru_list(page, lruvec, lru);
329                 trace_mm_lru_activate(page);
330 
331                 __count_vm_events(PGACTIVATE, nr_pages);
332                 __count_memcg_events(lruvec_memcg(lruvec), PGACTIVATE,
333                                      nr_pages);
334         }
335 }
336 
337 #ifdef CONFIG_SMP
338 static void activate_page_drain(int cpu)
339 {
340         struct pagevec *pvec = &per_cpu(lru_pvecs.activate_page, cpu);
341 
342         if (pagevec_count(pvec))
343                 pagevec_lru_move_fn(pvec, __activate_page, NULL);
344 }
345 
346 static bool need_activate_page_drain(int cpu)
347 {
348         return pagevec_count(&per_cpu(lru_pvecs.activate_page, cpu)) != 0;
349 }
350 
351 void activate_page(struct page *page)
352 {
353         page = compound_head(page);
354         if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
355                 struct pagevec *pvec;
356 
357                 local_lock(&lru_pvecs.lock);
358                 pvec = this_cpu_ptr(&lru_pvecs.activate_page);
359                 get_page(page);
360                 if (!pagevec_add(pvec, page) || PageCompound(page))
361                         pagevec_lru_move_fn(pvec, __activate_page, NULL);
362                 local_unlock(&lru_pvecs.lock);
363         }
364 }
365 
366 #else
367 static inline void activate_page_drain(int cpu)
368 {
369 }
370 
371 void activate_page(struct page *page)
372 {
373         pg_data_t *pgdat = page_pgdat(page);
374 
375         page = compound_head(page);
376         spin_lock_irq(&pgdat->lru_lock);
377         __activate_page(page, mem_cgroup_page_lruvec(page, pgdat), NULL);
378         spin_unlock_irq(&pgdat->lru_lock);
379 }
380 #endif
381 
382 static void __lru_cache_activate_page(struct page *page)
383 {
384         struct pagevec *pvec;
385         int i;
386 
387         local_lock(&lru_pvecs.lock);
388         pvec = this_cpu_ptr(&lru_pvecs.lru_add);
389 
390         /*
391          * Search backwards on the optimistic assumption that the page being
392          * activated has just been added to this pagevec. Note that only
393          * the local pagevec is examined as a !PageLRU page could be in the
394          * process of being released, reclaimed, migrated or on a remote
395          * pagevec that is currently being drained. Furthermore, marking
396          * a remote pagevec's page PageActive potentially hits a race where
397          * a page is marked PageActive just after it is added to the inactive
398          * list causing accounting errors and BUG_ON checks to trigger.
399          */
400         for (i = pagevec_count(pvec) - 1; i >= 0; i--) {
401                 struct page *pagevec_page = pvec->pages[i];
402 
403                 if (pagevec_page == page) {
404                         SetPageActive(page);
405                         break;
406                 }
407         }
408 
409         local_unlock(&lru_pvecs.lock);
410 }
411 
412 /*
413  * Mark a page as having seen activity.
414  *
415  * inactive,unreferenced        ->      inactive,referenced
416  * inactive,referenced          ->      active,unreferenced
417  * active,unreferenced          ->      active,referenced
418  *
419  * When a newly allocated page is not yet visible, so safe for non-atomic ops,
420  * __SetPageReferenced(page) may be substituted for mark_page_accessed(page).
421  */
422 void mark_page_accessed(struct page *page)
423 {
424         page = compound_head(page);
425 
426         if (!PageReferenced(page)) {
427                 SetPageReferenced(page);
428         } else if (PageUnevictable(page)) {
429                 /*
430                  * Unevictable pages are on the "LRU_UNEVICTABLE" list. But,
431                  * this list is never rotated or maintained, so marking an
432                  * evictable page accessed has no effect.
433                  */
434         } else if (!PageActive(page)) {
435                 /*
436                  * If the page is on the LRU, queue it for activation via
437                  * lru_pvecs.activate_page. Otherwise, assume the page is on a
438                  * pagevec, mark it active and it'll be moved to the active
439                  * LRU on the next drain.
440                  */
441                 if (PageLRU(page))
442                         activate_page(page);
443                 else
444                         __lru_cache_activate_page(page);
445                 ClearPageReferenced(page);
446                 workingset_activation(page);
447         }
448         if (page_is_idle(page))
449                 clear_page_idle(page);
450 }
451 EXPORT_SYMBOL(mark_page_accessed);
452 
453 /**
454  * lru_cache_add - add a page to a page list
455  * @page: the page to be added to the LRU.
456  *
457  * Queue the page for addition to the LRU via pagevec. The decision on whether
458  * to add the page to the [in]active [file|anon] list is deferred until the
459  * pagevec is drained. This gives a chance for the caller of lru_cache_add()
460  * have the page added to the active list using mark_page_accessed().
461  */
462 void lru_cache_add(struct page *page)
463 {
464         struct pagevec *pvec;
465 
466         VM_BUG_ON_PAGE(PageActive(page) && PageUnevictable(page), page);
467         VM_BUG_ON_PAGE(PageLRU(page), page);
468 
469         get_page(page);
470         local_lock(&lru_pvecs.lock);
471         pvec = this_cpu_ptr(&lru_pvecs.lru_add);
472         if (!pagevec_add(pvec, page) || PageCompound(page))
473                 __pagevec_lru_add(pvec);
474         local_unlock(&lru_pvecs.lock);
475 }
476 EXPORT_SYMBOL(lru_cache_add);
477 
478 /**
479  * lru_cache_add_inactive_or_unevictable
480  * @page:  the page to be added to LRU
481  * @vma:   vma in which page is mapped for determining reclaimability
482  *
483  * Place @page on the inactive or unevictable LRU list, depending on its
484  * evictability.  Note that if the page is not evictable, it goes
485  * directly back onto it's zone's unevictable list, it does NOT use a
486  * per cpu pagevec.
487  */
488 void lru_cache_add_inactive_or_unevictable(struct page *page,
489                                          struct vm_area_struct *vma)
490 {
491         bool unevictable;
492 
493         VM_BUG_ON_PAGE(PageLRU(page), page);
494 
495         unevictable = (vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) == VM_LOCKED;
496         if (unlikely(unevictable) && !TestSetPageMlocked(page)) {
497                 int nr_pages = thp_nr_pages(page);
498                 /*
499                  * We use the irq-unsafe __mod_zone_page_stat because this
500                  * counter is not modified from interrupt context, and the pte
501                  * lock is held(spinlock), which implies preemption disabled.
502                  */
503                 __mod_zone_page_state(page_zone(page), NR_MLOCK, nr_pages);
504                 count_vm_events(UNEVICTABLE_PGMLOCKED, nr_pages);
505         }
506         lru_cache_add(page);
507 }
508 
509 /*
510  * If the page can not be invalidated, it is moved to the
511  * inactive list to speed up its reclaim.  It is moved to the
512  * head of the list, rather than the tail, to give the flusher
513  * threads some time to write it out, as this is much more
514  * effective than the single-page writeout from reclaim.
515  *
516  * If the page isn't page_mapped and dirty/writeback, the page
517  * could reclaim asap using PG_reclaim.
518  *
519  * 1. active, mapped page -> none
520  * 2. active, dirty/writeback page -> inactive, head, PG_reclaim
521  * 3. inactive, mapped page -> none
522  * 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim
523  * 5. inactive, clean -> inactive, tail
524  * 6. Others -> none
525  *
526  * In 4, why it moves inactive's head, the VM expects the page would
527  * be write it out by flusher threads as this is much more effective
528  * than the single-page writeout from reclaim.
529  */
530 static void lru_deactivate_file_fn(struct page *page, struct lruvec *lruvec,
531                               void *arg)
532 {
533         int lru;
534         bool active;
535         int nr_pages = thp_nr_pages(page);
536 
537         if (!PageLRU(page))
538                 return;
539 
540         if (PageUnevictable(page))
541                 return;
542 
543         /* Some processes are using the page */
544         if (page_mapped(page))
545                 return;
546 
547         active = PageActive(page);
548         lru = page_lru_base_type(page);
549 
550         del_page_from_lru_list(page, lruvec, lru + active);
551         ClearPageActive(page);
552         ClearPageReferenced(page);
553 
554         if (PageWriteback(page) || PageDirty(page)) {
555                 /*
556                  * PG_reclaim could be raced with end_page_writeback
557                  * It can make readahead confusing.  But race window
558                  * is _really_ small and  it's non-critical problem.
559                  */
560                 add_page_to_lru_list(page, lruvec, lru);
561                 SetPageReclaim(page);
562         } else {
563                 /*
564                  * The page's writeback ends up during pagevec
565                  * We moves tha page into tail of inactive.
566                  */
567                 add_page_to_lru_list_tail(page, lruvec, lru);
568                 __count_vm_events(PGROTATED, nr_pages);
569         }
570 
571         if (active) {
572                 __count_vm_events(PGDEACTIVATE, nr_pages);
573                 __count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE,
574                                      nr_pages);
575         }
576 }
577 
578 static void lru_deactivate_fn(struct page *page, struct lruvec *lruvec,
579                             void *arg)
580 {
581         if (PageLRU(page) && PageActive(page) && !PageUnevictable(page)) {
582                 int lru = page_lru_base_type(page);
583                 int nr_pages = thp_nr_pages(page);
584 
585                 del_page_from_lru_list(page, lruvec, lru + LRU_ACTIVE);
586                 ClearPageActive(page);
587                 ClearPageReferenced(page);
588                 add_page_to_lru_list(page, lruvec, lru);
589 
590                 __count_vm_events(PGDEACTIVATE, nr_pages);
591                 __count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE,
592                                      nr_pages);
593         }
594 }
595 
596 static void lru_lazyfree_fn(struct page *page, struct lruvec *lruvec,
597                             void *arg)
598 {
599         if (PageLRU(page) && PageAnon(page) && PageSwapBacked(page) &&
600             !PageSwapCache(page) && !PageUnevictable(page)) {
601                 bool active = PageActive(page);
602                 int nr_pages = thp_nr_pages(page);
603 
604                 del_page_from_lru_list(page, lruvec,
605                                        LRU_INACTIVE_ANON + active);
606                 ClearPageActive(page);
607                 ClearPageReferenced(page);
608                 /*
609                  * Lazyfree pages are clean anonymous pages.  They have
610                  * PG_swapbacked flag cleared, to distinguish them from normal
611                  * anonymous pages
612                  */
613                 ClearPageSwapBacked(page);
614                 add_page_to_lru_list(page, lruvec, LRU_INACTIVE_FILE);
615 
616                 __count_vm_events(PGLAZYFREE, nr_pages);
617                 __count_memcg_events(lruvec_memcg(lruvec), PGLAZYFREE,
618                                      nr_pages);
619         }
620 }
621 
622 /*
623  * Drain pages out of the cpu's pagevecs.
624  * Either "cpu" is the current CPU, and preemption has already been
625  * disabled; or "cpu" is being hot-unplugged, and is already dead.
626  */
627 void lru_add_drain_cpu(int cpu)
628 {
629         struct pagevec *pvec = &per_cpu(lru_pvecs.lru_add, cpu);
630 
631         if (pagevec_count(pvec))
632                 __pagevec_lru_add(pvec);
633 
634         pvec = &per_cpu(lru_rotate.pvec, cpu);
635         /* Disabling interrupts below acts as a compiler barrier. */
636         if (data_race(pagevec_count(pvec))) {
637                 unsigned long flags;
638 
639                 /* No harm done if a racing interrupt already did this */
640                 local_lock_irqsave(&lru_rotate.lock, flags);
641                 pagevec_move_tail(pvec);
642                 local_unlock_irqrestore(&lru_rotate.lock, flags);
643         }
644 
645         pvec = &per_cpu(lru_pvecs.lru_deactivate_file, cpu);
646         if (pagevec_count(pvec))
647                 pagevec_lru_move_fn(pvec, lru_deactivate_file_fn, NULL);
648 
649         pvec = &per_cpu(lru_pvecs.lru_deactivate, cpu);
650         if (pagevec_count(pvec))
651                 pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
652 
653         pvec = &per_cpu(lru_pvecs.lru_lazyfree, cpu);
654         if (pagevec_count(pvec))
655                 pagevec_lru_move_fn(pvec, lru_lazyfree_fn, NULL);
656 
657         activate_page_drain(cpu);
658 }
659 
660 /**
661  * deactivate_file_page - forcefully deactivate a file page
662  * @page: page to deactivate
663  *
664  * This function hints the VM that @page is a good reclaim candidate,
665  * for example if its invalidation fails due to the page being dirty
666  * or under writeback.
667  */
668 void deactivate_file_page(struct page *page)
669 {
670         /*
671          * In a workload with many unevictable page such as mprotect,
672          * unevictable page deactivation for accelerating reclaim is pointless.
673          */
674         if (PageUnevictable(page))
675                 return;
676 
677         if (likely(get_page_unless_zero(page))) {
678                 struct pagevec *pvec;
679 
680                 local_lock(&lru_pvecs.lock);
681                 pvec = this_cpu_ptr(&lru_pvecs.lru_deactivate_file);
682 
683                 if (!pagevec_add(pvec, page) || PageCompound(page))
684                         pagevec_lru_move_fn(pvec, lru_deactivate_file_fn, NULL);
685                 local_unlock(&lru_pvecs.lock);
686         }
687 }
688 
689 /*
690  * deactivate_page - deactivate a page
691  * @page: page to deactivate
692  *
693  * deactivate_page() moves @page to the inactive list if @page was on the active
694  * list and was not an unevictable page.  This is done to accelerate the reclaim
695  * of @page.
696  */
697 void deactivate_page(struct page *page)
698 {
699         if (PageLRU(page) && PageActive(page) && !PageUnevictable(page)) {
700                 struct pagevec *pvec;
701 
702                 local_lock(&lru_pvecs.lock);
703                 pvec = this_cpu_ptr(&lru_pvecs.lru_deactivate);
704                 get_page(page);
705                 if (!pagevec_add(pvec, page) || PageCompound(page))
706                         pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
707                 local_unlock(&lru_pvecs.lock);
708         }
709 }
710 
711 /**
712  * mark_page_lazyfree - make an anon page lazyfree
713  * @page: page to deactivate
714  *
715  * mark_page_lazyfree() moves @page to the inactive file list.
716  * This is done to accelerate the reclaim of @page.
717  */
718 void mark_page_lazyfree(struct page *page)
719 {
720         if (PageLRU(page) && PageAnon(page) && PageSwapBacked(page) &&
721             !PageSwapCache(page) && !PageUnevictable(page)) {
722                 struct pagevec *pvec;
723 
724                 local_lock(&lru_pvecs.lock);
725                 pvec = this_cpu_ptr(&lru_pvecs.lru_lazyfree);
726                 get_page(page);
727                 if (!pagevec_add(pvec, page) || PageCompound(page))
728                         pagevec_lru_move_fn(pvec, lru_lazyfree_fn, NULL);
729                 local_unlock(&lru_pvecs.lock);
730         }
731 }
732 
733 void lru_add_drain(void)
734 {
735         local_lock(&lru_pvecs.lock);
736         lru_add_drain_cpu(smp_processor_id());
737         local_unlock(&lru_pvecs.lock);
738 }
739 
740 void lru_add_drain_cpu_zone(struct zone *zone)
741 {
742         local_lock(&lru_pvecs.lock);
743         lru_add_drain_cpu(smp_processor_id());
744         drain_local_pages(zone);
745         local_unlock(&lru_pvecs.lock);
746 }
747 
748 #ifdef CONFIG_SMP
749 
750 static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work);
751 
752 static void lru_add_drain_per_cpu(struct work_struct *dummy)
753 {
754         lru_add_drain();
755 }
756 
757 /*
758  * Doesn't need any cpu hotplug locking because we do rely on per-cpu
759  * kworkers being shut down before our page_alloc_cpu_dead callback is
760  * executed on the offlined cpu.
761  * Calling this function with cpu hotplug locks held can actually lead
762  * to obscure indirect dependencies via WQ context.
763  */
764 void lru_add_drain_all(void)
765 {
766         static seqcount_t seqcount = SEQCNT_ZERO(seqcount);
767         static DEFINE_MUTEX(lock);
768         static struct cpumask has_work;
769         int cpu, seq;
770 
771         /*
772          * Make sure nobody triggers this path before mm_percpu_wq is fully
773          * initialized.
774          */
775         if (WARN_ON(!mm_percpu_wq))
776                 return;
777 
778         seq = raw_read_seqcount_latch(&seqcount);
779 
780         mutex_lock(&lock);
781 
782         /*
783          * Piggyback on drain started and finished while we waited for lock:
784          * all pages pended at the time of our enter were drained from vectors.
785          */
786         if (__read_seqcount_retry(&seqcount, seq))
787                 goto done;
788 
789         raw_write_seqcount_latch(&seqcount);
790 
791         cpumask_clear(&has_work);
792 
793         for_each_online_cpu(cpu) {
794                 struct work_struct *work = &per_cpu(lru_add_drain_work, cpu);
795 
796                 if (pagevec_count(&per_cpu(lru_pvecs.lru_add, cpu)) ||
797                     data_race(pagevec_count(&per_cpu(lru_rotate.pvec, cpu))) ||
798                     pagevec_count(&per_cpu(lru_pvecs.lru_deactivate_file, cpu)) ||
799                     pagevec_count(&per_cpu(lru_pvecs.lru_deactivate, cpu)) ||
800                     pagevec_count(&per_cpu(lru_pvecs.lru_lazyfree, cpu)) ||
801                     need_activate_page_drain(cpu)) {
802                         INIT_WORK(work, lru_add_drain_per_cpu);
803                         queue_work_on(cpu, mm_percpu_wq, work);
804                         cpumask_set_cpu(cpu, &has_work);
805                 }
806         }
807 
808         for_each_cpu(cpu, &has_work)
809                 flush_work(&per_cpu(lru_add_drain_work, cpu));
810 
811 done:
812         mutex_unlock(&lock);
813 }
814 #else
815 void lru_add_drain_all(void)
816 {
817         lru_add_drain();
818 }
819 #endif
820 
821 /**
822  * release_pages - batched put_page()
823  * @pages: array of pages to release
824  * @nr: number of pages
825  *
826  * Decrement the reference count on all the pages in @pages.  If it
827  * fell to zero, remove the page from the LRU and free it.
828  */
829 void release_pages(struct page **pages, int nr)
830 {
831         int i;
832         LIST_HEAD(pages_to_free);
833         struct pglist_data *locked_pgdat = NULL;
834         struct lruvec *lruvec;
835         unsigned long flags;
836         unsigned int lock_batch;
837 
838         for (i = 0; i < nr; i++) {
839                 struct page *page = pages[i];
840 
841                 /*
842                  * Make sure the IRQ-safe lock-holding time does not get
843                  * excessive with a continuous string of pages from the
844                  * same pgdat. The lock is held only if pgdat != NULL.
845                  */
846                 if (locked_pgdat && ++lock_batch == SWAP_CLUSTER_MAX) {
847                         spin_unlock_irqrestore(&locked_pgdat->lru_lock, flags);
848                         locked_pgdat = NULL;
849                 }
850 
851                 if (is_huge_zero_page(page))
852                         continue;
853 
854                 if (is_zone_device_page(page)) {
855                         if (locked_pgdat) {
856                                 spin_unlock_irqrestore(&locked_pgdat->lru_lock,
857                                                        flags);
858                                 locked_pgdat = NULL;
859                         }
860                         /*
861                          * ZONE_DEVICE pages that return 'false' from
862                          * put_devmap_managed_page() do not require special
863                          * processing, and instead, expect a call to
864                          * put_page_testzero().
865                          */
866                         if (page_is_devmap_managed(page)) {
867                                 put_devmap_managed_page(page);
868                                 continue;
869                         }
870                 }
871 
872                 page = compound_head(page);
873                 if (!put_page_testzero(page))
874                         continue;
875 
876                 if (PageCompound(page)) {
877                         if (locked_pgdat) {
878                                 spin_unlock_irqrestore(&locked_pgdat->lru_lock, flags);
879                                 locked_pgdat = NULL;
880                         }
881                         __put_compound_page(page);
882                         continue;
883                 }
884 
885                 if (PageLRU(page)) {
886                         struct pglist_data *pgdat = page_pgdat(page);
887 
888                         if (pgdat != locked_pgdat) {
889                                 if (locked_pgdat)
890                                         spin_unlock_irqrestore(&locked_pgdat->lru_lock,
891                                                                         flags);
892                                 lock_batch = 0;
893                                 locked_pgdat = pgdat;
894                                 spin_lock_irqsave(&locked_pgdat->lru_lock, flags);
895                         }
896 
897                         lruvec = mem_cgroup_page_lruvec(page, locked_pgdat);
898                         VM_BUG_ON_PAGE(!PageLRU(page), page);
899                         __ClearPageLRU(page);
900                         del_page_from_lru_list(page, lruvec, page_off_lru(page));
901                 }
902 
903                 /* Clear Active bit in case of parallel mark_page_accessed */
904                 __ClearPageActive(page);
905                 __ClearPageWaiters(page);
906 
907                 list_add(&page->lru, &pages_to_free);
908         }
909         if (locked_pgdat)
910                 spin_unlock_irqrestore(&locked_pgdat->lru_lock, flags);
911 
912         mem_cgroup_uncharge_list(&pages_to_free);
913         free_unref_page_list(&pages_to_free);
914 }
915 EXPORT_SYMBOL(release_pages);
916 
917 /*
918  * The pages which we're about to release may be in the deferred lru-addition
919  * queues.  That would prevent them from really being freed right now.  That's
920  * OK from a correctness point of view but is inefficient - those pages may be
921  * cache-warm and we want to give them back to the page allocator ASAP.
922  *
923  * So __pagevec_release() will drain those queues here.  __pagevec_lru_add()
924  * and __pagevec_lru_add_active() call release_pages() directly to avoid
925  * mutual recursion.
926  */
927 void __pagevec_release(struct pagevec *pvec)
928 {
929         if (!pvec->percpu_pvec_drained) {
930                 lru_add_drain();
931                 pvec->percpu_pvec_drained = true;
932         }
933         release_pages(pvec->pages, pagevec_count(pvec));
934         pagevec_reinit(pvec);
935 }
936 EXPORT_SYMBOL(__pagevec_release);
937 
938 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
939 /* used by __split_huge_page_refcount() */
940 void lru_add_page_tail(struct page *page, struct page *page_tail,
941                        struct lruvec *lruvec, struct list_head *list)
942 {
943         VM_BUG_ON_PAGE(!PageHead(page), page);
944         VM_BUG_ON_PAGE(PageCompound(page_tail), page);
945         VM_BUG_ON_PAGE(PageLRU(page_tail), page);
946         lockdep_assert_held(&lruvec_pgdat(lruvec)->lru_lock);
947 
948         if (!list)
949                 SetPageLRU(page_tail);
950 
951         if (likely(PageLRU(page)))
952                 list_add_tail(&page_tail->lru, &page->lru);
953         else if (list) {
954                 /* page reclaim is reclaiming a huge page */
955                 get_page(page_tail);
956                 list_add_tail(&page_tail->lru, list);
957         } else {
958                 /*
959                  * Head page has not yet been counted, as an hpage,
960                  * so we must account for each subpage individually.
961                  *
962                  * Put page_tail on the list at the correct position
963                  * so they all end up in order.
964                  */
965                 add_page_to_lru_list_tail(page_tail, lruvec,
966                                           page_lru(page_tail));
967         }
968 }
969 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
970 
971 static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec,
972                                  void *arg)
973 {
974         enum lru_list lru;
975         int was_unevictable = TestClearPageUnevictable(page);
976         int nr_pages = thp_nr_pages(page);
977 
978         VM_BUG_ON_PAGE(PageLRU(page), page);
979 
980         /*
981          * Page becomes evictable in two ways:
982          * 1) Within LRU lock [munlock_vma_page() and __munlock_pagevec()].
983          * 2) Before acquiring LRU lock to put the page to correct LRU and then
984          *   a) do PageLRU check with lock [check_move_unevictable_pages]
985          *   b) do PageLRU check before lock [clear_page_mlock]
986          *
987          * (1) & (2a) are ok as LRU lock will serialize them. For (2b), we need
988          * following strict ordering:
989          *
990          * #0: __pagevec_lru_add_fn             #1: clear_page_mlock
991          *
992          * SetPageLRU()                         TestClearPageMlocked()
993          * smp_mb() // explicit ordering        // above provides strict
994          *                                      // ordering
995          * PageMlocked()                        PageLRU()
996          *
997          *
998          * if '#1' does not observe setting of PG_lru by '#0' and fails
999          * isolation, the explicit barrier will make sure that page_evictable
1000          * check will put the page in correct LRU. Without smp_mb(), SetPageLRU
1001          * can be reordered after PageMlocked check and can make '#1' to fail
1002          * the isolation of the page whose Mlocked bit is cleared (#0 is also
1003          * looking at the same page) and the evictable page will be stranded
1004          * in an unevictable LRU.
1005          */
1006         SetPageLRU(page);
1007         smp_mb__after_atomic();
1008 
1009         if (page_evictable(page)) {
1010                 lru = page_lru(page);
1011                 if (was_unevictable)
1012                         __count_vm_events(UNEVICTABLE_PGRESCUED, nr_pages);
1013         } else {
1014                 lru = LRU_UNEVICTABLE;
1015                 ClearPageActive(page);
1016                 SetPageUnevictable(page);
1017                 if (!was_unevictable)
1018                         __count_vm_events(UNEVICTABLE_PGCULLED, nr_pages);
1019         }
1020 
1021         add_page_to_lru_list(page, lruvec, lru);
1022         trace_mm_lru_insertion(page, lru);
1023 }
1024 
1025 /*
1026  * Add the passed pages to the LRU, then drop the caller's refcount
1027  * on them.  Reinitialises the caller's pagevec.
1028  */
1029 void __pagevec_lru_add(struct pagevec *pvec)
1030 {
1031         pagevec_lru_move_fn(pvec, __pagevec_lru_add_fn, NULL);
1032 }
1033 
1034 /**
1035  * pagevec_lookup_entries - gang pagecache lookup
1036  * @pvec:       Where the resulting entries are placed
1037  * @mapping:    The address_space to search
1038  * @start:      The starting entry index
1039  * @nr_entries: The maximum number of pages
1040  * @indices:    The cache indices corresponding to the entries in @pvec
1041  *
1042  * pagevec_lookup_entries() will search for and return a group of up
1043  * to @nr_pages pages and shadow entries in the mapping.  All
1044  * entries are placed in @pvec.  pagevec_lookup_entries() takes a
1045  * reference against actual pages in @pvec.
1046  *
1047  * The search returns a group of mapping-contiguous entries with
1048  * ascending indexes.  There may be holes in the indices due to
1049  * not-present entries.
1050  *
1051  * Only one subpage of a Transparent Huge Page is returned in one call:
1052  * allowing truncate_inode_pages_range() to evict the whole THP without
1053  * cycling through a pagevec of extra references.
1054  *
1055  * pagevec_lookup_entries() returns the number of entries which were
1056  * found.
1057  */
1058 unsigned pagevec_lookup_entries(struct pagevec *pvec,
1059                                 struct address_space *mapping,
1060                                 pgoff_t start, unsigned nr_entries,
1061                                 pgoff_t *indices)
1062 {
1063         pvec->nr = find_get_entries(mapping, start, nr_entries,
1064                                     pvec->pages, indices);
1065         return pagevec_count(pvec);
1066 }
1067 
1068 /**
1069  * pagevec_remove_exceptionals - pagevec exceptionals pruning
1070  * @pvec:       The pagevec to prune
1071  *
1072  * pagevec_lookup_entries() fills both pages and exceptional radix
1073  * tree entries into the pagevec.  This function prunes all
1074  * exceptionals from @pvec without leaving holes, so that it can be
1075  * passed on to page-only pagevec operations.
1076  */
1077 void pagevec_remove_exceptionals(struct pagevec *pvec)
1078 {
1079         int i, j;
1080 
1081         for (i = 0, j = 0; i < pagevec_count(pvec); i++) {
1082                 struct page *page = pvec->pages[i];
1083                 if (!xa_is_value(page))
1084                         pvec->pages[j++] = page;
1085         }
1086         pvec->nr = j;
1087 }
1088 
1089 /**
1090  * pagevec_lookup_range - gang pagecache lookup
1091  * @pvec:       Where the resulting pages are placed
1092  * @mapping:    The address_space to search
1093  * @start:      The starting page index
1094  * @end:        The final page index
1095  *
1096  * pagevec_lookup_range() will search for & return a group of up to PAGEVEC_SIZE
1097  * pages in the mapping starting from index @start and upto index @end
1098  * (inclusive).  The pages are placed in @pvec.  pagevec_lookup() takes a
1099  * reference against the pages in @pvec.
1100  *
1101  * The search returns a group of mapping-contiguous pages with ascending
1102  * indexes.  There may be holes in the indices due to not-present pages. We
1103  * also update @start to index the next page for the traversal.
1104  *
1105  * pagevec_lookup_range() returns the number of pages which were found. If this
1106  * number is smaller than PAGEVEC_SIZE, the end of specified range has been
1107  * reached.
1108  */
1109 unsigned pagevec_lookup_range(struct pagevec *pvec,
1110                 struct address_space *mapping, pgoff_t *start, pgoff_t end)
1111 {
1112         pvec->nr = find_get_pages_range(mapping, start, end, PAGEVEC_SIZE,
1113                                         pvec->pages);
1114         return pagevec_count(pvec);
1115 }
1116 EXPORT_SYMBOL(pagevec_lookup_range);
1117 
1118 unsigned pagevec_lookup_range_tag(struct pagevec *pvec,
1119                 struct address_space *mapping, pgoff_t *index, pgoff_t end,
1120                 xa_mark_t tag)
1121 {
1122         pvec->nr = find_get_pages_range_tag(mapping, index, end, tag,
1123                                         PAGEVEC_SIZE, pvec->pages);
1124         return pagevec_count(pvec);
1125 }
1126 EXPORT_SYMBOL(pagevec_lookup_range_tag);
1127 
1128 unsigned pagevec_lookup_range_nr_tag(struct pagevec *pvec,
1129                 struct address_space *mapping, pgoff_t *index, pgoff_t end,
1130                 xa_mark_t tag, unsigned max_pages)
1131 {
1132         pvec->nr = find_get_pages_range_tag(mapping, index, end, tag,
1133                 min_t(unsigned int, max_pages, PAGEVEC_SIZE), pvec->pages);
1134         return pagevec_count(pvec);
1135 }
1136 EXPORT_SYMBOL(pagevec_lookup_range_nr_tag);
1137 /*
1138  * Perform any setup for the swap system
1139  */
1140 void __init swap_setup(void)
1141 {
1142         unsigned long megs = totalram_pages() >> (20 - PAGE_SHIFT);
1143 
1144         /* Use a smaller cluster for small-memory machines */
1145         if (megs < 16)
1146                 page_cluster = 2;
1147         else
1148                 page_cluster = 3;
1149         /*
1150          * Right now other parts of the system means that we
1151          * _really_ don't want to cluster much more
1152          */
1153 }
1154 
1155 #ifdef CONFIG_DEV_PAGEMAP_OPS
1156 void put_devmap_managed_page(struct page *page)
1157 {
1158         int count;
1159 
1160         if (WARN_ON_ONCE(!page_is_devmap_managed(page)))
1161                 return;
1162 
1163         count = page_ref_dec_return(page);
1164 
1165         /*
1166          * devmap page refcounts are 1-based, rather than 0-based: if
1167          * refcount is 1, then the page is free and the refcount is
1168          * stable because nobody holds a reference on the page.
1169          */
1170         if (count == 1)
1171                 free_devmap_managed_page(page);
1172         else if (!count)
1173                 __put_page(page);
1174 }
1175 EXPORT_SYMBOL(put_devmap_managed_page);
1176 #endif
1177 

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