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Linux/mm/swap.c

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

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