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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) += hpage_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), hpage_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 = hpage_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_active_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 active 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_active_or_unevictable(struct page *page,
489                                          struct vm_area_struct *vma)
490 {
491         VM_BUG_ON_PAGE(PageLRU(page), page);
492 
493         if (likely((vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) != VM_LOCKED))
494                 SetPageActive(page);
495         else if (!TestSetPageMlocked(page)) {
496                 /*
497                  * We use the irq-unsafe __mod_zone_page_stat because this
498                  * counter is not modified from interrupt context, and the pte
499                  * lock is held(spinlock), which implies preemption disabled.
500                  */
501                 __mod_zone_page_state(page_zone(page), NR_MLOCK,
502                                     hpage_nr_pages(page));
503                 count_vm_event(UNEVICTABLE_PGMLOCKED);
504         }
505         lru_cache_add(page);
506 }
507 
508 /*
509  * If the page can not be invalidated, it is moved to the
510  * inactive list to speed up its reclaim.  It is moved to the
511  * head of the list, rather than the tail, to give the flusher
512  * threads some time to write it out, as this is much more
513  * effective than the single-page writeout from reclaim.
514  *
515  * If the page isn't page_mapped and dirty/writeback, the page
516  * could reclaim asap using PG_reclaim.
517  *
518  * 1. active, mapped page -> none
519  * 2. active, dirty/writeback page -> inactive, head, PG_reclaim
520  * 3. inactive, mapped page -> none
521  * 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim
522  * 5. inactive, clean -> inactive, tail
523  * 6. Others -> none
524  *
525  * In 4, why it moves inactive's head, the VM expects the page would
526  * be write it out by flusher threads as this is much more effective
527  * than the single-page writeout from reclaim.
528  */
529 static void lru_deactivate_file_fn(struct page *page, struct lruvec *lruvec,
530                               void *arg)
531 {
532         int lru;
533         bool active;
534         int nr_pages = hpage_nr_pages(page);
535 
536         if (!PageLRU(page))
537                 return;
538 
539         if (PageUnevictable(page))
540                 return;
541 
542         /* Some processes are using the page */
543         if (page_mapped(page))
544                 return;
545 
546         active = PageActive(page);
547         lru = page_lru_base_type(page);
548 
549         del_page_from_lru_list(page, lruvec, lru + active);
550         ClearPageActive(page);
551         ClearPageReferenced(page);
552 
553         if (PageWriteback(page) || PageDirty(page)) {
554                 /*
555                  * PG_reclaim could be raced with end_page_writeback
556                  * It can make readahead confusing.  But race window
557                  * is _really_ small and  it's non-critical problem.
558                  */
559                 add_page_to_lru_list(page, lruvec, lru);
560                 SetPageReclaim(page);
561         } else {
562                 /*
563                  * The page's writeback ends up during pagevec
564                  * We moves tha page into tail of inactive.
565                  */
566                 add_page_to_lru_list_tail(page, lruvec, lru);
567                 __count_vm_events(PGROTATED, nr_pages);
568         }
569 
570         if (active) {
571                 __count_vm_events(PGDEACTIVATE, nr_pages);
572                 __count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE,
573                                      nr_pages);
574         }
575 }
576 
577 static void lru_deactivate_fn(struct page *page, struct lruvec *lruvec,
578                             void *arg)
579 {
580         if (PageLRU(page) && PageActive(page) && !PageUnevictable(page)) {
581                 int lru = page_lru_base_type(page);
582                 int nr_pages = hpage_nr_pages(page);
583 
584                 del_page_from_lru_list(page, lruvec, lru + LRU_ACTIVE);
585                 ClearPageActive(page);
586                 ClearPageReferenced(page);
587                 add_page_to_lru_list(page, lruvec, lru);
588 
589                 __count_vm_events(PGDEACTIVATE, nr_pages);
590                 __count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE,
591                                      nr_pages);
592         }
593 }
594 
595 static void lru_lazyfree_fn(struct page *page, struct lruvec *lruvec,
596                             void *arg)
597 {
598         if (PageLRU(page) && PageAnon(page) && PageSwapBacked(page) &&
599             !PageSwapCache(page) && !PageUnevictable(page)) {
600                 bool active = PageActive(page);
601                 int nr_pages = hpage_nr_pages(page);
602 
603                 del_page_from_lru_list(page, lruvec,
604                                        LRU_INACTIVE_ANON + active);
605                 ClearPageActive(page);
606                 ClearPageReferenced(page);
607                 /*
608                  * Lazyfree pages are clean anonymous pages.  They have
609                  * PG_swapbacked flag cleared, to distinguish them from normal
610                  * anonymous pages
611                  */
612                 ClearPageSwapBacked(page);
613                 add_page_to_lru_list(page, lruvec, LRU_INACTIVE_FILE);
614 
615                 __count_vm_events(PGLAZYFREE, nr_pages);
616                 __count_memcg_events(lruvec_memcg(lruvec), PGLAZYFREE,
617                                      nr_pages);
618         }
619 }
620 
621 /*
622  * Drain pages out of the cpu's pagevecs.
623  * Either "cpu" is the current CPU, and preemption has already been
624  * disabled; or "cpu" is being hot-unplugged, and is already dead.
625  */
626 void lru_add_drain_cpu(int cpu)
627 {
628         struct pagevec *pvec = &per_cpu(lru_pvecs.lru_add, cpu);
629 
630         if (pagevec_count(pvec))
631                 __pagevec_lru_add(pvec);
632 
633         pvec = &per_cpu(lru_rotate.pvec, cpu);
634         if (pagevec_count(pvec)) {
635                 unsigned long flags;
636 
637                 /* No harm done if a racing interrupt already did this */
638                 local_lock_irqsave(&lru_rotate.lock, flags);
639                 pagevec_move_tail(pvec);
640                 local_unlock_irqrestore(&lru_rotate.lock, flags);
641         }
642 
643         pvec = &per_cpu(lru_pvecs.lru_deactivate_file, cpu);
644         if (pagevec_count(pvec))
645                 pagevec_lru_move_fn(pvec, lru_deactivate_file_fn, NULL);
646 
647         pvec = &per_cpu(lru_pvecs.lru_deactivate, cpu);
648         if (pagevec_count(pvec))
649                 pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
650 
651         pvec = &per_cpu(lru_pvecs.lru_lazyfree, cpu);
652         if (pagevec_count(pvec))
653                 pagevec_lru_move_fn(pvec, lru_lazyfree_fn, NULL);
654 
655         activate_page_drain(cpu);
656 }
657 
658 /**
659  * deactivate_file_page - forcefully deactivate a file page
660  * @page: page to deactivate
661  *
662  * This function hints the VM that @page is a good reclaim candidate,
663  * for example if its invalidation fails due to the page being dirty
664  * or under writeback.
665  */
666 void deactivate_file_page(struct page *page)
667 {
668         /*
669          * In a workload with many unevictable page such as mprotect,
670          * unevictable page deactivation for accelerating reclaim is pointless.
671          */
672         if (PageUnevictable(page))
673                 return;
674 
675         if (likely(get_page_unless_zero(page))) {
676                 struct pagevec *pvec;
677 
678                 local_lock(&lru_pvecs.lock);
679                 pvec = this_cpu_ptr(&lru_pvecs.lru_deactivate_file);
680 
681                 if (!pagevec_add(pvec, page) || PageCompound(page))
682                         pagevec_lru_move_fn(pvec, lru_deactivate_file_fn, NULL);
683                 local_unlock(&lru_pvecs.lock);
684         }
685 }
686 
687 /*
688  * deactivate_page - deactivate a page
689  * @page: page to deactivate
690  *
691  * deactivate_page() moves @page to the inactive list if @page was on the active
692  * list and was not an unevictable page.  This is done to accelerate the reclaim
693  * of @page.
694  */
695 void deactivate_page(struct page *page)
696 {
697         if (PageLRU(page) && PageActive(page) && !PageUnevictable(page)) {
698                 struct pagevec *pvec;
699 
700                 local_lock(&lru_pvecs.lock);
701                 pvec = this_cpu_ptr(&lru_pvecs.lru_deactivate);
702                 get_page(page);
703                 if (!pagevec_add(pvec, page) || PageCompound(page))
704                         pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
705                 local_unlock(&lru_pvecs.lock);
706         }
707 }
708 
709 /**
710  * mark_page_lazyfree - make an anon page lazyfree
711  * @page: page to deactivate
712  *
713  * mark_page_lazyfree() moves @page to the inactive file list.
714  * This is done to accelerate the reclaim of @page.
715  */
716 void mark_page_lazyfree(struct page *page)
717 {
718         if (PageLRU(page) && PageAnon(page) && PageSwapBacked(page) &&
719             !PageSwapCache(page) && !PageUnevictable(page)) {
720                 struct pagevec *pvec;
721 
722                 local_lock(&lru_pvecs.lock);
723                 pvec = this_cpu_ptr(&lru_pvecs.lru_lazyfree);
724                 get_page(page);
725                 if (!pagevec_add(pvec, page) || PageCompound(page))
726                         pagevec_lru_move_fn(pvec, lru_lazyfree_fn, NULL);
727                 local_unlock(&lru_pvecs.lock);
728         }
729 }
730 
731 void lru_add_drain(void)
732 {
733         local_lock(&lru_pvecs.lock);
734         lru_add_drain_cpu(smp_processor_id());
735         local_unlock(&lru_pvecs.lock);
736 }
737 
738 void lru_add_drain_cpu_zone(struct zone *zone)
739 {
740         local_lock(&lru_pvecs.lock);
741         lru_add_drain_cpu(smp_processor_id());
742         drain_local_pages(zone);
743         local_unlock(&lru_pvecs.lock);
744 }
745 
746 #ifdef CONFIG_SMP
747 
748 static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work);
749 
750 static void lru_add_drain_per_cpu(struct work_struct *dummy)
751 {
752         lru_add_drain();
753 }
754 
755 /*
756  * Doesn't need any cpu hotplug locking because we do rely on per-cpu
757  * kworkers being shut down before our page_alloc_cpu_dead callback is
758  * executed on the offlined cpu.
759  * Calling this function with cpu hotplug locks held can actually lead
760  * to obscure indirect dependencies via WQ context.
761  */
762 void lru_add_drain_all(void)
763 {
764         static seqcount_t seqcount = SEQCNT_ZERO(seqcount);
765         static DEFINE_MUTEX(lock);
766         static struct cpumask has_work;
767         int cpu, seq;
768 
769         /*
770          * Make sure nobody triggers this path before mm_percpu_wq is fully
771          * initialized.
772          */
773         if (WARN_ON(!mm_percpu_wq))
774                 return;
775 
776         seq = raw_read_seqcount_latch(&seqcount);
777 
778         mutex_lock(&lock);
779 
780         /*
781          * Piggyback on drain started and finished while we waited for lock:
782          * all pages pended at the time of our enter were drained from vectors.
783          */
784         if (__read_seqcount_retry(&seqcount, seq))
785                 goto done;
786 
787         raw_write_seqcount_latch(&seqcount);
788 
789         cpumask_clear(&has_work);
790 
791         for_each_online_cpu(cpu) {
792                 struct work_struct *work = &per_cpu(lru_add_drain_work, cpu);
793 
794                 if (pagevec_count(&per_cpu(lru_pvecs.lru_add, cpu)) ||
795                     pagevec_count(&per_cpu(lru_rotate.pvec, cpu)) ||
796                     pagevec_count(&per_cpu(lru_pvecs.lru_deactivate_file, cpu)) ||
797                     pagevec_count(&per_cpu(lru_pvecs.lru_deactivate, cpu)) ||
798                     pagevec_count(&per_cpu(lru_pvecs.lru_lazyfree, cpu)) ||
799                     need_activate_page_drain(cpu)) {
800                         INIT_WORK(work, lru_add_drain_per_cpu);
801                         queue_work_on(cpu, mm_percpu_wq, work);
802                         cpumask_set_cpu(cpu, &has_work);
803                 }
804         }
805 
806         for_each_cpu(cpu, &has_work)
807                 flush_work(&per_cpu(lru_add_drain_work, cpu));
808 
809 done:
810         mutex_unlock(&lock);
811 }
812 #else
813 void lru_add_drain_all(void)
814 {
815         lru_add_drain();
816 }
817 #endif
818 
819 /**
820  * release_pages - batched put_page()
821  * @pages: array of pages to release
822  * @nr: number of pages
823  *
824  * Decrement the reference count on all the pages in @pages.  If it
825  * fell to zero, remove the page from the LRU and free it.
826  */
827 void release_pages(struct page **pages, int nr)
828 {
829         int i;
830         LIST_HEAD(pages_to_free);
831         struct pglist_data *locked_pgdat = NULL;
832         struct lruvec *lruvec;
833         unsigned long uninitialized_var(flags);
834         unsigned int uninitialized_var(lock_batch);
835 
836         for (i = 0; i < nr; i++) {
837                 struct page *page = pages[i];
838 
839                 /*
840                  * Make sure the IRQ-safe lock-holding time does not get
841                  * excessive with a continuous string of pages from the
842                  * same pgdat. The lock is held only if pgdat != NULL.
843                  */
844                 if (locked_pgdat && ++lock_batch == SWAP_CLUSTER_MAX) {
845                         spin_unlock_irqrestore(&locked_pgdat->lru_lock, flags);
846                         locked_pgdat = NULL;
847                 }
848 
849                 if (is_huge_zero_page(page))
850                         continue;
851 
852                 if (is_zone_device_page(page)) {
853                         if (locked_pgdat) {
854                                 spin_unlock_irqrestore(&locked_pgdat->lru_lock,
855                                                        flags);
856                                 locked_pgdat = NULL;
857                         }
858                         /*
859                          * ZONE_DEVICE pages that return 'false' from
860                          * put_devmap_managed_page() do not require special
861                          * processing, and instead, expect a call to
862                          * put_page_testzero().
863                          */
864                         if (page_is_devmap_managed(page)) {
865                                 put_devmap_managed_page(page);
866                                 continue;
867                         }
868                 }
869 
870                 page = compound_head(page);
871                 if (!put_page_testzero(page))
872                         continue;
873 
874                 if (PageCompound(page)) {
875                         if (locked_pgdat) {
876                                 spin_unlock_irqrestore(&locked_pgdat->lru_lock, flags);
877                                 locked_pgdat = NULL;
878                         }
879                         __put_compound_page(page);
880                         continue;
881                 }
882 
883                 if (PageLRU(page)) {
884                         struct pglist_data *pgdat = page_pgdat(page);
885 
886                         if (pgdat != locked_pgdat) {
887                                 if (locked_pgdat)
888                                         spin_unlock_irqrestore(&locked_pgdat->lru_lock,
889                                                                         flags);
890                                 lock_batch = 0;
891                                 locked_pgdat = pgdat;
892                                 spin_lock_irqsave(&locked_pgdat->lru_lock, flags);
893                         }
894 
895                         lruvec = mem_cgroup_page_lruvec(page, locked_pgdat);
896                         VM_BUG_ON_PAGE(!PageLRU(page), page);
897                         __ClearPageLRU(page);
898                         del_page_from_lru_list(page, lruvec, page_off_lru(page));
899                 }
900 
901                 /* Clear Active bit in case of parallel mark_page_accessed */
902                 __ClearPageActive(page);
903                 __ClearPageWaiters(page);
904 
905                 list_add(&page->lru, &pages_to_free);
906         }
907         if (locked_pgdat)
908                 spin_unlock_irqrestore(&locked_pgdat->lru_lock, flags);
909 
910         mem_cgroup_uncharge_list(&pages_to_free);
911         free_unref_page_list(&pages_to_free);
912 }
913 EXPORT_SYMBOL(release_pages);
914 
915 /*
916  * The pages which we're about to release may be in the deferred lru-addition
917  * queues.  That would prevent them from really being freed right now.  That's
918  * OK from a correctness point of view but is inefficient - those pages may be
919  * cache-warm and we want to give them back to the page allocator ASAP.
920  *
921  * So __pagevec_release() will drain those queues here.  __pagevec_lru_add()
922  * and __pagevec_lru_add_active() call release_pages() directly to avoid
923  * mutual recursion.
924  */
925 void __pagevec_release(struct pagevec *pvec)
926 {
927         if (!pvec->percpu_pvec_drained) {
928                 lru_add_drain();
929                 pvec->percpu_pvec_drained = true;
930         }
931         release_pages(pvec->pages, pagevec_count(pvec));
932         pagevec_reinit(pvec);
933 }
934 EXPORT_SYMBOL(__pagevec_release);
935 
936 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
937 /* used by __split_huge_page_refcount() */
938 void lru_add_page_tail(struct page *page, struct page *page_tail,
939                        struct lruvec *lruvec, struct list_head *list)
940 {
941         VM_BUG_ON_PAGE(!PageHead(page), page);
942         VM_BUG_ON_PAGE(PageCompound(page_tail), page);
943         VM_BUG_ON_PAGE(PageLRU(page_tail), page);
944         lockdep_assert_held(&lruvec_pgdat(lruvec)->lru_lock);
945 
946         if (!list)
947                 SetPageLRU(page_tail);
948 
949         if (likely(PageLRU(page)))
950                 list_add_tail(&page_tail->lru, &page->lru);
951         else if (list) {
952                 /* page reclaim is reclaiming a huge page */
953                 get_page(page_tail);
954                 list_add_tail(&page_tail->lru, list);
955         } else {
956                 /*
957                  * Head page has not yet been counted, as an hpage,
958                  * so we must account for each subpage individually.
959                  *
960                  * Put page_tail on the list at the correct position
961                  * so they all end up in order.
962                  */
963                 add_page_to_lru_list_tail(page_tail, lruvec,
964                                           page_lru(page_tail));
965         }
966 }
967 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
968 
969 static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec,
970                                  void *arg)
971 {
972         enum lru_list lru;
973         int was_unevictable = TestClearPageUnevictable(page);
974         int nr_pages = hpage_nr_pages(page);
975 
976         VM_BUG_ON_PAGE(PageLRU(page), page);
977 
978         /*
979          * Page becomes evictable in two ways:
980          * 1) Within LRU lock [munlock_vma_page() and __munlock_pagevec()].
981          * 2) Before acquiring LRU lock to put the page to correct LRU and then
982          *   a) do PageLRU check with lock [check_move_unevictable_pages]
983          *   b) do PageLRU check before lock [clear_page_mlock]
984          *
985          * (1) & (2a) are ok as LRU lock will serialize them. For (2b), we need
986          * following strict ordering:
987          *
988          * #0: __pagevec_lru_add_fn             #1: clear_page_mlock
989          *
990          * SetPageLRU()                         TestClearPageMlocked()
991          * smp_mb() // explicit ordering        // above provides strict
992          *                                      // ordering
993          * PageMlocked()                        PageLRU()
994          *
995          *
996          * if '#1' does not observe setting of PG_lru by '#0' and fails
997          * isolation, the explicit barrier will make sure that page_evictable
998          * check will put the page in correct LRU. Without smp_mb(), SetPageLRU
999          * can be reordered after PageMlocked check and can make '#1' to fail
1000          * the isolation of the page whose Mlocked bit is cleared (#0 is also
1001          * looking at the same page) and the evictable page will be stranded
1002          * in an unevictable LRU.
1003          */
1004         SetPageLRU(page);
1005         smp_mb__after_atomic();
1006 
1007         if (page_evictable(page)) {
1008                 lru = page_lru(page);
1009                 if (was_unevictable)
1010                         __count_vm_events(UNEVICTABLE_PGRESCUED, nr_pages);
1011         } else {
1012                 lru = LRU_UNEVICTABLE;
1013                 ClearPageActive(page);
1014                 SetPageUnevictable(page);
1015                 if (!was_unevictable)
1016                         __count_vm_events(UNEVICTABLE_PGCULLED, nr_pages);
1017         }
1018 
1019         add_page_to_lru_list(page, lruvec, lru);
1020         trace_mm_lru_insertion(page, lru);
1021 }
1022 
1023 /*
1024  * Add the passed pages to the LRU, then drop the caller's refcount
1025  * on them.  Reinitialises the caller's pagevec.
1026  */
1027 void __pagevec_lru_add(struct pagevec *pvec)
1028 {
1029         pagevec_lru_move_fn(pvec, __pagevec_lru_add_fn, NULL);
1030 }
1031 
1032 /**
1033  * pagevec_lookup_entries - gang pagecache lookup
1034  * @pvec:       Where the resulting entries are placed
1035  * @mapping:    The address_space to search
1036  * @start:      The starting entry index
1037  * @nr_entries: The maximum number of pages
1038  * @indices:    The cache indices corresponding to the entries in @pvec
1039  *
1040  * pagevec_lookup_entries() will search for and return a group of up
1041  * to @nr_pages pages and shadow entries in the mapping.  All
1042  * entries are placed in @pvec.  pagevec_lookup_entries() takes a
1043  * reference against actual pages in @pvec.
1044  *
1045  * The search returns a group of mapping-contiguous entries with
1046  * ascending indexes.  There may be holes in the indices due to
1047  * not-present entries.
1048  *
1049  * Only one subpage of a Transparent Huge Page is returned in one call:
1050  * allowing truncate_inode_pages_range() to evict the whole THP without
1051  * cycling through a pagevec of extra references.
1052  *
1053  * pagevec_lookup_entries() returns the number of entries which were
1054  * found.
1055  */
1056 unsigned pagevec_lookup_entries(struct pagevec *pvec,
1057                                 struct address_space *mapping,
1058                                 pgoff_t start, unsigned nr_entries,
1059                                 pgoff_t *indices)
1060 {
1061         pvec->nr = find_get_entries(mapping, start, nr_entries,
1062                                     pvec->pages, indices);
1063         return pagevec_count(pvec);
1064 }
1065 
1066 /**
1067  * pagevec_remove_exceptionals - pagevec exceptionals pruning
1068  * @pvec:       The pagevec to prune
1069  *
1070  * pagevec_lookup_entries() fills both pages and exceptional radix
1071  * tree entries into the pagevec.  This function prunes all
1072  * exceptionals from @pvec without leaving holes, so that it can be
1073  * passed on to page-only pagevec operations.
1074  */
1075 void pagevec_remove_exceptionals(struct pagevec *pvec)
1076 {
1077         int i, j;
1078 
1079         for (i = 0, j = 0; i < pagevec_count(pvec); i++) {
1080                 struct page *page = pvec->pages[i];
1081                 if (!xa_is_value(page))
1082                         pvec->pages[j++] = page;
1083         }
1084         pvec->nr = j;
1085 }
1086 
1087 /**
1088  * pagevec_lookup_range - gang pagecache lookup
1089  * @pvec:       Where the resulting pages are placed
1090  * @mapping:    The address_space to search
1091  * @start:      The starting page index
1092  * @end:        The final page index
1093  *
1094  * pagevec_lookup_range() will search for & return a group of up to PAGEVEC_SIZE
1095  * pages in the mapping starting from index @start and upto index @end
1096  * (inclusive).  The pages are placed in @pvec.  pagevec_lookup() takes a
1097  * reference against the pages in @pvec.
1098  *
1099  * The search returns a group of mapping-contiguous pages with ascending
1100  * indexes.  There may be holes in the indices due to not-present pages. We
1101  * also update @start to index the next page for the traversal.
1102  *
1103  * pagevec_lookup_range() returns the number of pages which were found. If this
1104  * number is smaller than PAGEVEC_SIZE, the end of specified range has been
1105  * reached.
1106  */
1107 unsigned pagevec_lookup_range(struct pagevec *pvec,
1108                 struct address_space *mapping, pgoff_t *start, pgoff_t end)
1109 {
1110         pvec->nr = find_get_pages_range(mapping, start, end, PAGEVEC_SIZE,
1111                                         pvec->pages);
1112         return pagevec_count(pvec);
1113 }
1114 EXPORT_SYMBOL(pagevec_lookup_range);
1115 
1116 unsigned pagevec_lookup_range_tag(struct pagevec *pvec,
1117                 struct address_space *mapping, pgoff_t *index, pgoff_t end,
1118                 xa_mark_t tag)
1119 {
1120         pvec->nr = find_get_pages_range_tag(mapping, index, end, tag,
1121                                         PAGEVEC_SIZE, pvec->pages);
1122         return pagevec_count(pvec);
1123 }
1124 EXPORT_SYMBOL(pagevec_lookup_range_tag);
1125 
1126 unsigned pagevec_lookup_range_nr_tag(struct pagevec *pvec,
1127                 struct address_space *mapping, pgoff_t *index, pgoff_t end,
1128                 xa_mark_t tag, unsigned max_pages)
1129 {
1130         pvec->nr = find_get_pages_range_tag(mapping, index, end, tag,
1131                 min_t(unsigned int, max_pages, PAGEVEC_SIZE), pvec->pages);
1132         return pagevec_count(pvec);
1133 }
1134 EXPORT_SYMBOL(pagevec_lookup_range_nr_tag);
1135 /*
1136  * Perform any setup for the swap system
1137  */
1138 void __init swap_setup(void)
1139 {
1140         unsigned long megs = totalram_pages() >> (20 - PAGE_SHIFT);
1141 
1142         /* Use a smaller cluster for small-memory machines */
1143         if (megs < 16)
1144                 page_cluster = 2;
1145         else
1146                 page_cluster = 3;
1147         /*
1148          * Right now other parts of the system means that we
1149          * _really_ don't want to cluster much more
1150          */
1151 }
1152 
1153 #ifdef CONFIG_DEV_PAGEMAP_OPS
1154 void put_devmap_managed_page(struct page *page)
1155 {
1156         int count;
1157 
1158         if (WARN_ON_ONCE(!page_is_devmap_managed(page)))
1159                 return;
1160 
1161         count = page_ref_dec_return(page);
1162 
1163         /*
1164          * devmap page refcounts are 1-based, rather than 0-based: if
1165          * refcount is 1, then the page is free and the refcount is
1166          * stable because nobody holds a reference on the page.
1167          */
1168         if (count == 1)
1169                 free_devmap_managed_page(page);
1170         else if (!count)
1171                 __put_page(page);
1172 }
1173 EXPORT_SYMBOL(put_devmap_managed_page);
1174 #endif
1175 

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