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TOMOYO Linux Cross Reference
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 = list_entry(pages->prev, struct page, lru);
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 static bool need_activate_page_drain(int cpu)
324 {
325         return false;
326 }
327 
328 void activate_page(struct page *page)
329 {
330         struct zone *zone = page_zone(page);
331 
332         page = compound_head(page);
333         spin_lock_irq(zone_lru_lock(zone));
334         __activate_page(page, mem_cgroup_page_lruvec(page, zone->zone_pgdat), NULL);
335         spin_unlock_irq(zone_lru_lock(zone));
336 }
337 #endif
338 
339 static void __lru_cache_activate_page(struct page *page)
340 {
341         struct pagevec *pvec = &get_cpu_var(lru_add_pvec);
342         int i;
343 
344         /*
345          * Search backwards on the optimistic assumption that the page being
346          * activated has just been added to this pagevec. Note that only
347          * the local pagevec is examined as a !PageLRU page could be in the
348          * process of being released, reclaimed, migrated or on a remote
349          * pagevec that is currently being drained. Furthermore, marking
350          * a remote pagevec's page PageActive potentially hits a race where
351          * a page is marked PageActive just after it is added to the inactive
352          * list causing accounting errors and BUG_ON checks to trigger.
353          */
354         for (i = pagevec_count(pvec) - 1; i >= 0; i--) {
355                 struct page *pagevec_page = pvec->pages[i];
356 
357                 if (pagevec_page == page) {
358                         SetPageActive(page);
359                         break;
360                 }
361         }
362 
363         put_cpu_var(lru_add_pvec);
364 }
365 
366 /*
367  * Mark a page as having seen activity.
368  *
369  * inactive,unreferenced        ->      inactive,referenced
370  * inactive,referenced          ->      active,unreferenced
371  * active,unreferenced          ->      active,referenced
372  *
373  * When a newly allocated page is not yet visible, so safe for non-atomic ops,
374  * __SetPageReferenced(page) may be substituted for mark_page_accessed(page).
375  */
376 void mark_page_accessed(struct page *page)
377 {
378         page = compound_head(page);
379         if (!PageActive(page) && !PageUnevictable(page) &&
380                         PageReferenced(page)) {
381 
382                 /*
383                  * If the page is on the LRU, queue it for activation via
384                  * activate_page_pvecs. Otherwise, assume the page is on a
385                  * pagevec, mark it active and it'll be moved to the active
386                  * LRU on the next drain.
387                  */
388                 if (PageLRU(page))
389                         activate_page(page);
390                 else
391                         __lru_cache_activate_page(page);
392                 ClearPageReferenced(page);
393                 if (page_is_file_cache(page))
394                         workingset_activation(page);
395         } else if (!PageReferenced(page)) {
396                 SetPageReferenced(page);
397         }
398         if (page_is_idle(page))
399                 clear_page_idle(page);
400 }
401 EXPORT_SYMBOL(mark_page_accessed);
402 
403 static void __lru_cache_add(struct page *page)
404 {
405         struct pagevec *pvec = &get_cpu_var(lru_add_pvec);
406 
407         get_page(page);
408         if (!pagevec_add(pvec, page) || PageCompound(page))
409                 __pagevec_lru_add(pvec);
410         put_cpu_var(lru_add_pvec);
411 }
412 
413 /**
414  * lru_cache_add_anon - add a page to the page lists
415  * @page: the page to add
416  */
417 void lru_cache_add_anon(struct page *page)
418 {
419         if (PageActive(page))
420                 ClearPageActive(page);
421         __lru_cache_add(page);
422 }
423 
424 void lru_cache_add_file(struct page *page)
425 {
426         if (PageActive(page))
427                 ClearPageActive(page);
428         __lru_cache_add(page);
429 }
430 EXPORT_SYMBOL(lru_cache_add_file);
431 
432 /**
433  * lru_cache_add - add a page to a page list
434  * @page: the page to be added to the LRU.
435  *
436  * Queue the page for addition to the LRU via pagevec. The decision on whether
437  * to add the page to the [in]active [file|anon] list is deferred until the
438  * pagevec is drained. This gives a chance for the caller of lru_cache_add()
439  * have the page added to the active list using mark_page_accessed().
440  */
441 void lru_cache_add(struct page *page)
442 {
443         VM_BUG_ON_PAGE(PageActive(page) && PageUnevictable(page), page);
444         VM_BUG_ON_PAGE(PageLRU(page), page);
445         __lru_cache_add(page);
446 }
447 
448 /**
449  * lru_cache_add_active_or_unevictable
450  * @page:  the page to be added to LRU
451  * @vma:   vma in which page is mapped for determining reclaimability
452  *
453  * Place @page on the active or unevictable LRU list, depending on its
454  * evictability.  Note that if the page is not evictable, it goes
455  * directly back onto it's zone's unevictable list, it does NOT use a
456  * per cpu pagevec.
457  */
458 void lru_cache_add_active_or_unevictable(struct page *page,
459                                          struct vm_area_struct *vma)
460 {
461         VM_BUG_ON_PAGE(PageLRU(page), page);
462 
463         if (likely((vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) != VM_LOCKED))
464                 SetPageActive(page);
465         else if (!TestSetPageMlocked(page)) {
466                 /*
467                  * We use the irq-unsafe __mod_zone_page_stat because this
468                  * counter is not modified from interrupt context, and the pte
469                  * lock is held(spinlock), which implies preemption disabled.
470                  */
471                 __mod_zone_page_state(page_zone(page), NR_MLOCK,
472                                     hpage_nr_pages(page));
473                 count_vm_event(UNEVICTABLE_PGMLOCKED);
474         }
475         lru_cache_add(page);
476 }
477 
478 /*
479  * If the page can not be invalidated, it is moved to the
480  * inactive list to speed up its reclaim.  It is moved to the
481  * head of the list, rather than the tail, to give the flusher
482  * threads some time to write it out, as this is much more
483  * effective than the single-page writeout from reclaim.
484  *
485  * If the page isn't page_mapped and dirty/writeback, the page
486  * could reclaim asap using PG_reclaim.
487  *
488  * 1. active, mapped page -> none
489  * 2. active, dirty/writeback page -> inactive, head, PG_reclaim
490  * 3. inactive, mapped page -> none
491  * 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim
492  * 5. inactive, clean -> inactive, tail
493  * 6. Others -> none
494  *
495  * In 4, why it moves inactive's head, the VM expects the page would
496  * be write it out by flusher threads as this is much more effective
497  * than the single-page writeout from reclaim.
498  */
499 static void lru_deactivate_file_fn(struct page *page, struct lruvec *lruvec,
500                               void *arg)
501 {
502         int lru, file;
503         bool active;
504 
505         if (!PageLRU(page))
506                 return;
507 
508         if (PageUnevictable(page))
509                 return;
510 
511         /* Some processes are using the page */
512         if (page_mapped(page))
513                 return;
514 
515         active = PageActive(page);
516         file = page_is_file_cache(page);
517         lru = page_lru_base_type(page);
518 
519         del_page_from_lru_list(page, lruvec, lru + active);
520         ClearPageActive(page);
521         ClearPageReferenced(page);
522         add_page_to_lru_list(page, lruvec, lru);
523 
524         if (PageWriteback(page) || PageDirty(page)) {
525                 /*
526                  * PG_reclaim could be raced with end_page_writeback
527                  * It can make readahead confusing.  But race window
528                  * is _really_ small and  it's non-critical problem.
529                  */
530                 SetPageReclaim(page);
531         } else {
532                 /*
533                  * The page's writeback ends up during pagevec
534                  * We moves tha page into tail of inactive.
535                  */
536                 list_move_tail(&page->lru, &lruvec->lists[lru]);
537                 __count_vm_event(PGROTATED);
538         }
539 
540         if (active)
541                 __count_vm_event(PGDEACTIVATE);
542         update_page_reclaim_stat(lruvec, file, 0);
543 }
544 
545 
546 static void lru_lazyfree_fn(struct page *page, struct lruvec *lruvec,
547                             void *arg)
548 {
549         if (PageLRU(page) && PageAnon(page) && PageSwapBacked(page) &&
550             !PageSwapCache(page) && !PageUnevictable(page)) {
551                 bool active = PageActive(page);
552 
553                 del_page_from_lru_list(page, lruvec,
554                                        LRU_INACTIVE_ANON + active);
555                 ClearPageActive(page);
556                 ClearPageReferenced(page);
557                 /*
558                  * lazyfree pages are clean anonymous pages. They have
559                  * SwapBacked flag cleared to distinguish normal anonymous
560                  * pages
561                  */
562                 ClearPageSwapBacked(page);
563                 add_page_to_lru_list(page, lruvec, LRU_INACTIVE_FILE);
564 
565                 __count_vm_events(PGLAZYFREE, hpage_nr_pages(page));
566                 count_memcg_page_event(page, PGLAZYFREE);
567                 update_page_reclaim_stat(lruvec, 1, 0);
568         }
569 }
570 
571 /*
572  * Drain pages out of the cpu's pagevecs.
573  * Either "cpu" is the current CPU, and preemption has already been
574  * disabled; or "cpu" is being hot-unplugged, and is already dead.
575  */
576 void lru_add_drain_cpu(int cpu)
577 {
578         struct pagevec *pvec = &per_cpu(lru_add_pvec, cpu);
579 
580         if (pagevec_count(pvec))
581                 __pagevec_lru_add(pvec);
582 
583         pvec = &per_cpu(lru_rotate_pvecs, cpu);
584         if (pagevec_count(pvec)) {
585                 unsigned long flags;
586 
587                 /* No harm done if a racing interrupt already did this */
588                 local_irq_save(flags);
589                 pagevec_move_tail(pvec);
590                 local_irq_restore(flags);
591         }
592 
593         pvec = &per_cpu(lru_deactivate_file_pvecs, cpu);
594         if (pagevec_count(pvec))
595                 pagevec_lru_move_fn(pvec, lru_deactivate_file_fn, NULL);
596 
597         pvec = &per_cpu(lru_lazyfree_pvecs, cpu);
598         if (pagevec_count(pvec))
599                 pagevec_lru_move_fn(pvec, lru_lazyfree_fn, NULL);
600 
601         activate_page_drain(cpu);
602 }
603 
604 /**
605  * deactivate_file_page - forcefully deactivate a file page
606  * @page: page to deactivate
607  *
608  * This function hints the VM that @page is a good reclaim candidate,
609  * for example if its invalidation fails due to the page being dirty
610  * or under writeback.
611  */
612 void deactivate_file_page(struct page *page)
613 {
614         /*
615          * In a workload with many unevictable page such as mprotect,
616          * unevictable page deactivation for accelerating reclaim is pointless.
617          */
618         if (PageUnevictable(page))
619                 return;
620 
621         if (likely(get_page_unless_zero(page))) {
622                 struct pagevec *pvec = &get_cpu_var(lru_deactivate_file_pvecs);
623 
624                 if (!pagevec_add(pvec, page) || PageCompound(page))
625                         pagevec_lru_move_fn(pvec, lru_deactivate_file_fn, NULL);
626                 put_cpu_var(lru_deactivate_file_pvecs);
627         }
628 }
629 
630 /**
631  * mark_page_lazyfree - make an anon page lazyfree
632  * @page: page to deactivate
633  *
634  * mark_page_lazyfree() moves @page to the inactive file list.
635  * This is done to accelerate the reclaim of @page.
636  */
637 void mark_page_lazyfree(struct page *page)
638 {
639         if (PageLRU(page) && PageAnon(page) && PageSwapBacked(page) &&
640             !PageSwapCache(page) && !PageUnevictable(page)) {
641                 struct pagevec *pvec = &get_cpu_var(lru_lazyfree_pvecs);
642 
643                 get_page(page);
644                 if (!pagevec_add(pvec, page) || PageCompound(page))
645                         pagevec_lru_move_fn(pvec, lru_lazyfree_fn, NULL);
646                 put_cpu_var(lru_lazyfree_pvecs);
647         }
648 }
649 
650 void lru_add_drain(void)
651 {
652         lru_add_drain_cpu(get_cpu());
653         put_cpu();
654 }
655 
656 static void lru_add_drain_per_cpu(struct work_struct *dummy)
657 {
658         lru_add_drain();
659 }
660 
661 static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work);
662 
663 /*
664  * Doesn't need any cpu hotplug locking because we do rely on per-cpu
665  * kworkers being shut down before our page_alloc_cpu_dead callback is
666  * executed on the offlined cpu.
667  * Calling this function with cpu hotplug locks held can actually lead
668  * to obscure indirect dependencies via WQ context.
669  */
670 void lru_add_drain_all(void)
671 {
672         static DEFINE_MUTEX(lock);
673         static struct cpumask has_work;
674         int cpu;
675 
676         /*
677          * Make sure nobody triggers this path before mm_percpu_wq is fully
678          * initialized.
679          */
680         if (WARN_ON(!mm_percpu_wq))
681                 return;
682 
683         mutex_lock(&lock);
684         cpumask_clear(&has_work);
685 
686         for_each_online_cpu(cpu) {
687                 struct work_struct *work = &per_cpu(lru_add_drain_work, cpu);
688 
689                 if (pagevec_count(&per_cpu(lru_add_pvec, cpu)) ||
690                     pagevec_count(&per_cpu(lru_rotate_pvecs, cpu)) ||
691                     pagevec_count(&per_cpu(lru_deactivate_file_pvecs, cpu)) ||
692                     pagevec_count(&per_cpu(lru_lazyfree_pvecs, cpu)) ||
693                     need_activate_page_drain(cpu)) {
694                         INIT_WORK(work, lru_add_drain_per_cpu);
695                         queue_work_on(cpu, mm_percpu_wq, work);
696                         cpumask_set_cpu(cpu, &has_work);
697                 }
698         }
699 
700         for_each_cpu(cpu, &has_work)
701                 flush_work(&per_cpu(lru_add_drain_work, cpu));
702 
703         mutex_unlock(&lock);
704 }
705 
706 /**
707  * release_pages - batched put_page()
708  * @pages: array of pages to release
709  * @nr: number of pages
710  * @cold: whether the pages are cache cold
711  *
712  * Decrement the reference count on all the pages in @pages.  If it
713  * fell to zero, remove the page from the LRU and free it.
714  */
715 void release_pages(struct page **pages, int nr)
716 {
717         int i;
718         LIST_HEAD(pages_to_free);
719         struct pglist_data *locked_pgdat = NULL;
720         struct lruvec *lruvec;
721         unsigned long uninitialized_var(flags);
722         unsigned int uninitialized_var(lock_batch);
723 
724         for (i = 0; i < nr; i++) {
725                 struct page *page = pages[i];
726 
727                 /*
728                  * Make sure the IRQ-safe lock-holding time does not get
729                  * excessive with a continuous string of pages from the
730                  * same pgdat. The lock is held only if pgdat != NULL.
731                  */
732                 if (locked_pgdat && ++lock_batch == SWAP_CLUSTER_MAX) {
733                         spin_unlock_irqrestore(&locked_pgdat->lru_lock, flags);
734                         locked_pgdat = NULL;
735                 }
736 
737                 if (is_huge_zero_page(page))
738                         continue;
739 
740                 /* Device public page can not be huge page */
741                 if (is_device_public_page(page)) {
742                         if (locked_pgdat) {
743                                 spin_unlock_irqrestore(&locked_pgdat->lru_lock,
744                                                        flags);
745                                 locked_pgdat = NULL;
746                         }
747                         put_zone_device_private_or_public_page(page);
748                         continue;
749                 }
750 
751                 page = compound_head(page);
752                 if (!put_page_testzero(page))
753                         continue;
754 
755                 if (PageCompound(page)) {
756                         if (locked_pgdat) {
757                                 spin_unlock_irqrestore(&locked_pgdat->lru_lock, flags);
758                                 locked_pgdat = NULL;
759                         }
760                         __put_compound_page(page);
761                         continue;
762                 }
763 
764                 if (PageLRU(page)) {
765                         struct pglist_data *pgdat = page_pgdat(page);
766 
767                         if (pgdat != locked_pgdat) {
768                                 if (locked_pgdat)
769                                         spin_unlock_irqrestore(&locked_pgdat->lru_lock,
770                                                                         flags);
771                                 lock_batch = 0;
772                                 locked_pgdat = pgdat;
773                                 spin_lock_irqsave(&locked_pgdat->lru_lock, flags);
774                         }
775 
776                         lruvec = mem_cgroup_page_lruvec(page, locked_pgdat);
777                         VM_BUG_ON_PAGE(!PageLRU(page), page);
778                         __ClearPageLRU(page);
779                         del_page_from_lru_list(page, lruvec, page_off_lru(page));
780                 }
781 
782                 /* Clear Active bit in case of parallel mark_page_accessed */
783                 __ClearPageActive(page);
784                 __ClearPageWaiters(page);
785 
786                 list_add(&page->lru, &pages_to_free);
787         }
788         if (locked_pgdat)
789                 spin_unlock_irqrestore(&locked_pgdat->lru_lock, flags);
790 
791         mem_cgroup_uncharge_list(&pages_to_free);
792         free_unref_page_list(&pages_to_free);
793 }
794 EXPORT_SYMBOL(release_pages);
795 
796 /*
797  * The pages which we're about to release may be in the deferred lru-addition
798  * queues.  That would prevent them from really being freed right now.  That's
799  * OK from a correctness point of view but is inefficient - those pages may be
800  * cache-warm and we want to give them back to the page allocator ASAP.
801  *
802  * So __pagevec_release() will drain those queues here.  __pagevec_lru_add()
803  * and __pagevec_lru_add_active() call release_pages() directly to avoid
804  * mutual recursion.
805  */
806 void __pagevec_release(struct pagevec *pvec)
807 {
808         if (!pvec->percpu_pvec_drained) {
809                 lru_add_drain();
810                 pvec->percpu_pvec_drained = true;
811         }
812         release_pages(pvec->pages, pagevec_count(pvec));
813         pagevec_reinit(pvec);
814 }
815 EXPORT_SYMBOL(__pagevec_release);
816 
817 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
818 /* used by __split_huge_page_refcount() */
819 void lru_add_page_tail(struct page *page, struct page *page_tail,
820                        struct lruvec *lruvec, struct list_head *list)
821 {
822         const int file = 0;
823 
824         VM_BUG_ON_PAGE(!PageHead(page), page);
825         VM_BUG_ON_PAGE(PageCompound(page_tail), page);
826         VM_BUG_ON_PAGE(PageLRU(page_tail), page);
827         VM_BUG_ON(NR_CPUS != 1 &&
828                   !spin_is_locked(&lruvec_pgdat(lruvec)->lru_lock));
829 
830         if (!list)
831                 SetPageLRU(page_tail);
832 
833         if (likely(PageLRU(page)))
834                 list_add_tail(&page_tail->lru, &page->lru);
835         else if (list) {
836                 /* page reclaim is reclaiming a huge page */
837                 get_page(page_tail);
838                 list_add_tail(&page_tail->lru, list);
839         } else {
840                 struct list_head *list_head;
841                 /*
842                  * Head page has not yet been counted, as an hpage,
843                  * so we must account for each subpage individually.
844                  *
845                  * Use the standard add function to put page_tail on the list,
846                  * but then correct its position so they all end up in order.
847                  */
848                 add_page_to_lru_list(page_tail, lruvec, page_lru(page_tail));
849                 list_head = page_tail->lru.prev;
850                 list_move_tail(&page_tail->lru, list_head);
851         }
852 
853         if (!PageUnevictable(page))
854                 update_page_reclaim_stat(lruvec, file, PageActive(page_tail));
855 }
856 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
857 
858 static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec,
859                                  void *arg)
860 {
861         enum lru_list lru;
862         int was_unevictable = TestClearPageUnevictable(page);
863 
864         VM_BUG_ON_PAGE(PageLRU(page), page);
865 
866         SetPageLRU(page);
867         /*
868          * Page becomes evictable in two ways:
869          * 1) Within LRU lock [munlock_vma_pages() and __munlock_pagevec()].
870          * 2) Before acquiring LRU lock to put the page to correct LRU and then
871          *   a) do PageLRU check with lock [check_move_unevictable_pages]
872          *   b) do PageLRU check before lock [clear_page_mlock]
873          *
874          * (1) & (2a) are ok as LRU lock will serialize them. For (2b), we need
875          * following strict ordering:
876          *
877          * #0: __pagevec_lru_add_fn             #1: clear_page_mlock
878          *
879          * SetPageLRU()                         TestClearPageMlocked()
880          * smp_mb() // explicit ordering        // above provides strict
881          *                                      // ordering
882          * PageMlocked()                        PageLRU()
883          *
884          *
885          * if '#1' does not observe setting of PG_lru by '#0' and fails
886          * isolation, the explicit barrier will make sure that page_evictable
887          * check will put the page in correct LRU. Without smp_mb(), SetPageLRU
888          * can be reordered after PageMlocked check and can make '#1' to fail
889          * the isolation of the page whose Mlocked bit is cleared (#0 is also
890          * looking at the same page) and the evictable page will be stranded
891          * in an unevictable LRU.
892          */
893         smp_mb();
894 
895         if (page_evictable(page)) {
896                 lru = page_lru(page);
897                 update_page_reclaim_stat(lruvec, page_is_file_cache(page),
898                                          PageActive(page));
899                 if (was_unevictable)
900                         count_vm_event(UNEVICTABLE_PGRESCUED);
901         } else {
902                 lru = LRU_UNEVICTABLE;
903                 ClearPageActive(page);
904                 SetPageUnevictable(page);
905                 if (!was_unevictable)
906                         count_vm_event(UNEVICTABLE_PGCULLED);
907         }
908 
909         add_page_to_lru_list(page, lruvec, lru);
910         trace_mm_lru_insertion(page, lru);
911 }
912 
913 /*
914  * Add the passed pages to the LRU, then drop the caller's refcount
915  * on them.  Reinitialises the caller's pagevec.
916  */
917 void __pagevec_lru_add(struct pagevec *pvec)
918 {
919         pagevec_lru_move_fn(pvec, __pagevec_lru_add_fn, NULL);
920 }
921 EXPORT_SYMBOL(__pagevec_lru_add);
922 
923 /**
924  * pagevec_lookup_entries - gang pagecache lookup
925  * @pvec:       Where the resulting entries are placed
926  * @mapping:    The address_space to search
927  * @start:      The starting entry index
928  * @nr_entries: The maximum number of pages
929  * @indices:    The cache indices corresponding to the entries in @pvec
930  *
931  * pagevec_lookup_entries() will search for and return a group of up
932  * to @nr_pages pages and shadow entries in the mapping.  All
933  * entries are placed in @pvec.  pagevec_lookup_entries() takes a
934  * reference against actual pages in @pvec.
935  *
936  * The search returns a group of mapping-contiguous entries with
937  * ascending indexes.  There may be holes in the indices due to
938  * not-present entries.
939  *
940  * pagevec_lookup_entries() returns the number of entries which were
941  * found.
942  */
943 unsigned pagevec_lookup_entries(struct pagevec *pvec,
944                                 struct address_space *mapping,
945                                 pgoff_t start, unsigned nr_entries,
946                                 pgoff_t *indices)
947 {
948         pvec->nr = find_get_entries(mapping, start, nr_entries,
949                                     pvec->pages, indices);
950         return pagevec_count(pvec);
951 }
952 
953 /**
954  * pagevec_remove_exceptionals - pagevec exceptionals pruning
955  * @pvec:       The pagevec to prune
956  *
957  * pagevec_lookup_entries() fills both pages and exceptional radix
958  * tree entries into the pagevec.  This function prunes all
959  * exceptionals from @pvec without leaving holes, so that it can be
960  * passed on to page-only pagevec operations.
961  */
962 void pagevec_remove_exceptionals(struct pagevec *pvec)
963 {
964         int i, j;
965 
966         for (i = 0, j = 0; i < pagevec_count(pvec); i++) {
967                 struct page *page = pvec->pages[i];
968                 if (!radix_tree_exceptional_entry(page))
969                         pvec->pages[j++] = page;
970         }
971         pvec->nr = j;
972 }
973 
974 /**
975  * pagevec_lookup_range - gang pagecache lookup
976  * @pvec:       Where the resulting pages are placed
977  * @mapping:    The address_space to search
978  * @start:      The starting page index
979  * @end:        The final page index
980  *
981  * pagevec_lookup_range() will search for & return a group of up to PAGEVEC_SIZE
982  * pages in the mapping starting from index @start and upto index @end
983  * (inclusive).  The pages are placed in @pvec.  pagevec_lookup() takes a
984  * reference against the pages in @pvec.
985  *
986  * The search returns a group of mapping-contiguous pages with ascending
987  * indexes.  There may be holes in the indices due to not-present pages. We
988  * also update @start to index the next page for the traversal.
989  *
990  * pagevec_lookup_range() returns the number of pages which were found. If this
991  * number is smaller than PAGEVEC_SIZE, the end of specified range has been
992  * reached.
993  */
994 unsigned pagevec_lookup_range(struct pagevec *pvec,
995                 struct address_space *mapping, pgoff_t *start, pgoff_t end)
996 {
997         pvec->nr = find_get_pages_range(mapping, start, end, PAGEVEC_SIZE,
998                                         pvec->pages);
999         return pagevec_count(pvec);
1000 }
1001 EXPORT_SYMBOL(pagevec_lookup_range);
1002 
1003 unsigned pagevec_lookup_range_tag(struct pagevec *pvec,
1004                 struct address_space *mapping, pgoff_t *index, pgoff_t end,
1005                 int tag)
1006 {
1007         pvec->nr = find_get_pages_range_tag(mapping, index, end, tag,
1008                                         PAGEVEC_SIZE, pvec->pages);
1009         return pagevec_count(pvec);
1010 }
1011 EXPORT_SYMBOL(pagevec_lookup_range_tag);
1012 
1013 unsigned pagevec_lookup_range_nr_tag(struct pagevec *pvec,
1014                 struct address_space *mapping, pgoff_t *index, pgoff_t end,
1015                 int tag, unsigned max_pages)
1016 {
1017         pvec->nr = find_get_pages_range_tag(mapping, index, end, tag,
1018                 min_t(unsigned int, max_pages, PAGEVEC_SIZE), pvec->pages);
1019         return pagevec_count(pvec);
1020 }
1021 EXPORT_SYMBOL(pagevec_lookup_range_nr_tag);
1022 /*
1023  * Perform any setup for the swap system
1024  */
1025 void __init swap_setup(void)
1026 {
1027         unsigned long megs = totalram_pages >> (20 - PAGE_SHIFT);
1028 
1029         /* Use a smaller cluster for small-memory machines */
1030         if (megs < 16)
1031                 page_cluster = 2;
1032         else
1033                 page_cluster = 3;
1034         /*
1035          * Right now other parts of the system means that we
1036          * _really_ don't want to cluster much more
1037          */
1038 }
1039 

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