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Linux/mm/swap.c

  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_deactivate_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_hot_cold_page(page, false);
 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 (unlikely(PageCompound(page)))
101                 __put_compound_page(page);
102         else
103                 __put_single_page(page);
104 }
105 EXPORT_SYMBOL(__put_page);
106 
107 /**
108  * put_pages_list() - release a list of pages
109  * @pages: list of pages threaded on page->lru
110  *
111  * Release a list of pages which are strung together on page.lru.  Currently
112  * used by read_cache_pages() and related error recovery code.
113  */
114 void put_pages_list(struct list_head *pages)
115 {
116         while (!list_empty(pages)) {
117                 struct page *victim;
118 
119                 victim = list_entry(pages->prev, struct page, lru);
120                 list_del(&victim->lru);
121                 put_page(victim);
122         }
123 }
124 EXPORT_SYMBOL(put_pages_list);
125 
126 /*
127  * get_kernel_pages() - pin kernel pages in memory
128  * @kiov:       An array of struct kvec structures
129  * @nr_segs:    number of segments to pin
130  * @write:      pinning for read/write, currently ignored
131  * @pages:      array that receives pointers to the pages pinned.
132  *              Should be at least nr_segs long.
133  *
134  * Returns number of pages pinned. This may be fewer than the number
135  * requested. If nr_pages is 0 or negative, returns 0. If no pages
136  * were pinned, returns -errno. Each page returned must be released
137  * with a put_page() call when it is finished with.
138  */
139 int get_kernel_pages(const struct kvec *kiov, int nr_segs, int write,
140                 struct page **pages)
141 {
142         int seg;
143 
144         for (seg = 0; seg < nr_segs; seg++) {
145                 if (WARN_ON(kiov[seg].iov_len != PAGE_SIZE))
146                         return seg;
147 
148                 pages[seg] = kmap_to_page(kiov[seg].iov_base);
149                 get_page(pages[seg]);
150         }
151 
152         return seg;
153 }
154 EXPORT_SYMBOL_GPL(get_kernel_pages);
155 
156 /*
157  * get_kernel_page() - pin a kernel page in memory
158  * @start:      starting kernel address
159  * @write:      pinning for read/write, currently ignored
160  * @pages:      array that receives pointer to the page pinned.
161  *              Must be at least nr_segs long.
162  *
163  * Returns 1 if page is pinned. If the page was not pinned, returns
164  * -errno. The page returned must be released with a put_page() call
165  * when it is finished with.
166  */
167 int get_kernel_page(unsigned long start, int write, struct page **pages)
168 {
169         const struct kvec kiov = {
170                 .iov_base = (void *)start,
171                 .iov_len = PAGE_SIZE
172         };
173 
174         return get_kernel_pages(&kiov, 1, write, pages);
175 }
176 EXPORT_SYMBOL_GPL(get_kernel_page);
177 
178 static void pagevec_lru_move_fn(struct pagevec *pvec,
179         void (*move_fn)(struct page *page, struct lruvec *lruvec, void *arg),
180         void *arg)
181 {
182         int i;
183         struct pglist_data *pgdat = NULL;
184         struct lruvec *lruvec;
185         unsigned long flags = 0;
186 
187         for (i = 0; i < pagevec_count(pvec); i++) {
188                 struct page *page = pvec->pages[i];
189                 struct pglist_data *pagepgdat = page_pgdat(page);
190 
191                 if (pagepgdat != pgdat) {
192                         if (pgdat)
193                                 spin_unlock_irqrestore(&pgdat->lru_lock, flags);
194                         pgdat = pagepgdat;
195                         spin_lock_irqsave(&pgdat->lru_lock, flags);
196                 }
197 
198                 lruvec = mem_cgroup_page_lruvec(page, pgdat);
199                 (*move_fn)(page, lruvec, arg);
200         }
201         if (pgdat)
202                 spin_unlock_irqrestore(&pgdat->lru_lock, flags);
203         release_pages(pvec->pages, pvec->nr, pvec->cold);
204         pagevec_reinit(pvec);
205 }
206 
207 static void pagevec_move_tail_fn(struct page *page, struct lruvec *lruvec,
208                                  void *arg)
209 {
210         int *pgmoved = arg;
211 
212         if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
213                 enum lru_list lru = page_lru_base_type(page);
214                 list_move_tail(&page->lru, &lruvec->lists[lru]);
215                 (*pgmoved)++;
216         }
217 }
218 
219 /*
220  * pagevec_move_tail() must be called with IRQ disabled.
221  * Otherwise this may cause nasty races.
222  */
223 static void pagevec_move_tail(struct pagevec *pvec)
224 {
225         int pgmoved = 0;
226 
227         pagevec_lru_move_fn(pvec, pagevec_move_tail_fn, &pgmoved);
228         __count_vm_events(PGROTATED, pgmoved);
229 }
230 
231 /*
232  * Writeback is about to end against a page which has been marked for immediate
233  * reclaim.  If it still appears to be reclaimable, move it to the tail of the
234  * inactive list.
235  */
236 void rotate_reclaimable_page(struct page *page)
237 {
238         if (!PageLocked(page) && !PageDirty(page) && !PageActive(page) &&
239             !PageUnevictable(page) && PageLRU(page)) {
240                 struct pagevec *pvec;
241                 unsigned long flags;
242 
243                 get_page(page);
244                 local_irq_save(flags);
245                 pvec = this_cpu_ptr(&lru_rotate_pvecs);
246                 if (!pagevec_add(pvec, page) || PageCompound(page))
247                         pagevec_move_tail(pvec);
248                 local_irq_restore(flags);
249         }
250 }
251 
252 static void update_page_reclaim_stat(struct lruvec *lruvec,
253                                      int file, int rotated)
254 {
255         struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
256 
257         reclaim_stat->recent_scanned[file]++;
258         if (rotated)
259                 reclaim_stat->recent_rotated[file]++;
260 }
261 
262 static void __activate_page(struct page *page, struct lruvec *lruvec,
263                             void *arg)
264 {
265         if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
266                 int file = page_is_file_cache(page);
267                 int lru = page_lru_base_type(page);
268 
269                 del_page_from_lru_list(page, lruvec, lru);
270                 SetPageActive(page);
271                 lru += LRU_ACTIVE;
272                 add_page_to_lru_list(page, lruvec, lru);
273                 trace_mm_lru_activate(page);
274 
275                 __count_vm_event(PGACTIVATE);
276                 update_page_reclaim_stat(lruvec, file, 1);
277         }
278 }
279 
280 #ifdef CONFIG_SMP
281 static void activate_page_drain(int cpu)
282 {
283         struct pagevec *pvec = &per_cpu(activate_page_pvecs, cpu);
284 
285         if (pagevec_count(pvec))
286                 pagevec_lru_move_fn(pvec, __activate_page, NULL);
287 }
288 
289 static bool need_activate_page_drain(int cpu)
290 {
291         return pagevec_count(&per_cpu(activate_page_pvecs, cpu)) != 0;
292 }
293 
294 void activate_page(struct page *page)
295 {
296         page = compound_head(page);
297         if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
298                 struct pagevec *pvec = &get_cpu_var(activate_page_pvecs);
299 
300                 get_page(page);
301                 if (!pagevec_add(pvec, page) || PageCompound(page))
302                         pagevec_lru_move_fn(pvec, __activate_page, NULL);
303                 put_cpu_var(activate_page_pvecs);
304         }
305 }
306 
307 #else
308 static inline void activate_page_drain(int cpu)
309 {
310 }
311 
312 static bool need_activate_page_drain(int cpu)
313 {
314         return false;
315 }
316 
317 void activate_page(struct page *page)
318 {
319         struct zone *zone = page_zone(page);
320 
321         page = compound_head(page);
322         spin_lock_irq(zone_lru_lock(zone));
323         __activate_page(page, mem_cgroup_page_lruvec(page, zone->zone_pgdat), NULL);
324         spin_unlock_irq(zone_lru_lock(zone));
325 }
326 #endif
327 
328 static void __lru_cache_activate_page(struct page *page)
329 {
330         struct pagevec *pvec = &get_cpu_var(lru_add_pvec);
331         int i;
332 
333         /*
334          * Search backwards on the optimistic assumption that the page being
335          * activated has just been added to this pagevec. Note that only
336          * the local pagevec is examined as a !PageLRU page could be in the
337          * process of being released, reclaimed, migrated or on a remote
338          * pagevec that is currently being drained. Furthermore, marking
339          * a remote pagevec's page PageActive potentially hits a race where
340          * a page is marked PageActive just after it is added to the inactive
341          * list causing accounting errors and BUG_ON checks to trigger.
342          */
343         for (i = pagevec_count(pvec) - 1; i >= 0; i--) {
344                 struct page *pagevec_page = pvec->pages[i];
345 
346                 if (pagevec_page == page) {
347                         SetPageActive(page);
348                         break;
349                 }
350         }
351 
352         put_cpu_var(lru_add_pvec);
353 }
354 
355 /*
356  * Mark a page as having seen activity.
357  *
358  * inactive,unreferenced        ->      inactive,referenced
359  * inactive,referenced          ->      active,unreferenced
360  * active,unreferenced          ->      active,referenced
361  *
362  * When a newly allocated page is not yet visible, so safe for non-atomic ops,
363  * __SetPageReferenced(page) may be substituted for mark_page_accessed(page).
364  */
365 void mark_page_accessed(struct page *page)
366 {
367         page = compound_head(page);
368         if (!PageActive(page) && !PageUnevictable(page) &&
369                         PageReferenced(page)) {
370 
371                 /*
372                  * If the page is on the LRU, queue it for activation via
373                  * activate_page_pvecs. Otherwise, assume the page is on a
374                  * pagevec, mark it active and it'll be moved to the active
375                  * LRU on the next drain.
376                  */
377                 if (PageLRU(page))
378                         activate_page(page);
379                 else
380                         __lru_cache_activate_page(page);
381                 ClearPageReferenced(page);
382                 if (page_is_file_cache(page))
383                         workingset_activation(page);
384         } else if (!PageReferenced(page)) {
385                 SetPageReferenced(page);
386         }
387         if (page_is_idle(page))
388                 clear_page_idle(page);
389 }
390 EXPORT_SYMBOL(mark_page_accessed);
391 
392 static void __lru_cache_add(struct page *page)
393 {
394         struct pagevec *pvec = &get_cpu_var(lru_add_pvec);
395 
396         get_page(page);
397         if (!pagevec_add(pvec, page) || PageCompound(page))
398                 __pagevec_lru_add(pvec);
399         put_cpu_var(lru_add_pvec);
400 }
401 
402 /**
403  * lru_cache_add: add a page to the page lists
404  * @page: the page to add
405  */
406 void lru_cache_add_anon(struct page *page)
407 {
408         if (PageActive(page))
409                 ClearPageActive(page);
410         __lru_cache_add(page);
411 }
412 
413 void lru_cache_add_file(struct page *page)
414 {
415         if (PageActive(page))
416                 ClearPageActive(page);
417         __lru_cache_add(page);
418 }
419 EXPORT_SYMBOL(lru_cache_add_file);
420 
421 /**
422  * lru_cache_add - add a page to a page list
423  * @page: the page to be added to the LRU.
424  *
425  * Queue the page for addition to the LRU via pagevec. The decision on whether
426  * to add the page to the [in]active [file|anon] list is deferred until the
427  * pagevec is drained. This gives a chance for the caller of lru_cache_add()
428  * have the page added to the active list using mark_page_accessed().
429  */
430 void lru_cache_add(struct page *page)
431 {
432         VM_BUG_ON_PAGE(PageActive(page) && PageUnevictable(page), page);
433         VM_BUG_ON_PAGE(PageLRU(page), page);
434         __lru_cache_add(page);
435 }
436 
437 /**
438  * add_page_to_unevictable_list - add a page to the unevictable list
439  * @page:  the page to be added to the unevictable list
440  *
441  * Add page directly to its zone's unevictable list.  To avoid races with
442  * tasks that might be making the page evictable, through eg. munlock,
443  * munmap or exit, while it's not on the lru, we want to add the page
444  * while it's locked or otherwise "invisible" to other tasks.  This is
445  * difficult to do when using the pagevec cache, so bypass that.
446  */
447 void add_page_to_unevictable_list(struct page *page)
448 {
449         struct pglist_data *pgdat = page_pgdat(page);
450         struct lruvec *lruvec;
451 
452         spin_lock_irq(&pgdat->lru_lock);
453         lruvec = mem_cgroup_page_lruvec(page, pgdat);
454         ClearPageActive(page);
455         SetPageUnevictable(page);
456         SetPageLRU(page);
457         add_page_to_lru_list(page, lruvec, LRU_UNEVICTABLE);
458         spin_unlock_irq(&pgdat->lru_lock);
459 }
460 
461 /**
462  * lru_cache_add_active_or_unevictable
463  * @page:  the page to be added to LRU
464  * @vma:   vma in which page is mapped for determining reclaimability
465  *
466  * Place @page on the active or unevictable LRU list, depending on its
467  * evictability.  Note that if the page is not evictable, it goes
468  * directly back onto it's zone's unevictable list, it does NOT use a
469  * per cpu pagevec.
470  */
471 void lru_cache_add_active_or_unevictable(struct page *page,
472                                          struct vm_area_struct *vma)
473 {
474         VM_BUG_ON_PAGE(PageLRU(page), page);
475 
476         if (likely((vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) != VM_LOCKED)) {
477                 SetPageActive(page);
478                 lru_cache_add(page);
479                 return;
480         }
481 
482         if (!TestSetPageMlocked(page)) {
483                 /*
484                  * We use the irq-unsafe __mod_zone_page_stat because this
485                  * counter is not modified from interrupt context, and the pte
486                  * lock is held(spinlock), which implies preemption disabled.
487                  */
488                 __mod_zone_page_state(page_zone(page), NR_MLOCK,
489                                     hpage_nr_pages(page));
490                 count_vm_event(UNEVICTABLE_PGMLOCKED);
491         }
492         add_page_to_unevictable_list(page);
493 }
494 
495 /*
496  * If the page can not be invalidated, it is moved to the
497  * inactive list to speed up its reclaim.  It is moved to the
498  * head of the list, rather than the tail, to give the flusher
499  * threads some time to write it out, as this is much more
500  * effective than the single-page writeout from reclaim.
501  *
502  * If the page isn't page_mapped and dirty/writeback, the page
503  * could reclaim asap using PG_reclaim.
504  *
505  * 1. active, mapped page -> none
506  * 2. active, dirty/writeback page -> inactive, head, PG_reclaim
507  * 3. inactive, mapped page -> none
508  * 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim
509  * 5. inactive, clean -> inactive, tail
510  * 6. Others -> none
511  *
512  * In 4, why it moves inactive's head, the VM expects the page would
513  * be write it out by flusher threads as this is much more effective
514  * than the single-page writeout from reclaim.
515  */
516 static void lru_deactivate_file_fn(struct page *page, struct lruvec *lruvec,
517                               void *arg)
518 {
519         int lru, file;
520         bool active;
521 
522         if (!PageLRU(page))
523                 return;
524 
525         if (PageUnevictable(page))
526                 return;
527 
528         /* Some processes are using the page */
529         if (page_mapped(page))
530                 return;
531 
532         active = PageActive(page);
533         file = page_is_file_cache(page);
534         lru = page_lru_base_type(page);
535 
536         del_page_from_lru_list(page, lruvec, lru + active);
537         ClearPageActive(page);
538         ClearPageReferenced(page);
539         add_page_to_lru_list(page, lruvec, lru);
540 
541         if (PageWriteback(page) || PageDirty(page)) {
542                 /*
543                  * PG_reclaim could be raced with end_page_writeback
544                  * It can make readahead confusing.  But race window
545                  * is _really_ small and  it's non-critical problem.
546                  */
547                 SetPageReclaim(page);
548         } else {
549                 /*
550                  * The page's writeback ends up during pagevec
551                  * We moves tha page into tail of inactive.
552                  */
553                 list_move_tail(&page->lru, &lruvec->lists[lru]);
554                 __count_vm_event(PGROTATED);
555         }
556 
557         if (active)
558                 __count_vm_event(PGDEACTIVATE);
559         update_page_reclaim_stat(lruvec, file, 0);
560 }
561 
562 
563 static void lru_deactivate_fn(struct page *page, struct lruvec *lruvec,
564                             void *arg)
565 {
566         if (PageLRU(page) && PageActive(page) && !PageUnevictable(page)) {
567                 int file = page_is_file_cache(page);
568                 int lru = page_lru_base_type(page);
569 
570                 del_page_from_lru_list(page, lruvec, lru + LRU_ACTIVE);
571                 ClearPageActive(page);
572                 ClearPageReferenced(page);
573                 add_page_to_lru_list(page, lruvec, lru);
574 
575                 __count_vm_event(PGDEACTIVATE);
576                 update_page_reclaim_stat(lruvec, file, 0);
577         }
578 }
579 
580 /*
581  * Drain pages out of the cpu's pagevecs.
582  * Either "cpu" is the current CPU, and preemption has already been
583  * disabled; or "cpu" is being hot-unplugged, and is already dead.
584  */
585 void lru_add_drain_cpu(int cpu)
586 {
587         struct pagevec *pvec = &per_cpu(lru_add_pvec, cpu);
588 
589         if (pagevec_count(pvec))
590                 __pagevec_lru_add(pvec);
591 
592         pvec = &per_cpu(lru_rotate_pvecs, cpu);
593         if (pagevec_count(pvec)) {
594                 unsigned long flags;
595 
596                 /* No harm done if a racing interrupt already did this */
597                 local_irq_save(flags);
598                 pagevec_move_tail(pvec);
599                 local_irq_restore(flags);
600         }
601 
602         pvec = &per_cpu(lru_deactivate_file_pvecs, cpu);
603         if (pagevec_count(pvec))
604                 pagevec_lru_move_fn(pvec, lru_deactivate_file_fn, NULL);
605 
606         pvec = &per_cpu(lru_deactivate_pvecs, cpu);
607         if (pagevec_count(pvec))
608                 pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
609 
610         activate_page_drain(cpu);
611 }
612 
613 /**
614  * deactivate_file_page - forcefully deactivate a file page
615  * @page: page to deactivate
616  *
617  * This function hints the VM that @page is a good reclaim candidate,
618  * for example if its invalidation fails due to the page being dirty
619  * or under writeback.
620  */
621 void deactivate_file_page(struct page *page)
622 {
623         /*
624          * In a workload with many unevictable page such as mprotect,
625          * unevictable page deactivation for accelerating reclaim is pointless.
626          */
627         if (PageUnevictable(page))
628                 return;
629 
630         if (likely(get_page_unless_zero(page))) {
631                 struct pagevec *pvec = &get_cpu_var(lru_deactivate_file_pvecs);
632 
633                 if (!pagevec_add(pvec, page) || PageCompound(page))
634                         pagevec_lru_move_fn(pvec, lru_deactivate_file_fn, NULL);
635                 put_cpu_var(lru_deactivate_file_pvecs);
636         }
637 }
638 
639 /**
640  * deactivate_page - deactivate a page
641  * @page: page to deactivate
642  *
643  * deactivate_page() moves @page to the inactive list if @page was on the active
644  * list and was not an unevictable page.  This is done to accelerate the reclaim
645  * of @page.
646  */
647 void deactivate_page(struct page *page)
648 {
649         if (PageLRU(page) && PageActive(page) && !PageUnevictable(page)) {
650                 struct pagevec *pvec = &get_cpu_var(lru_deactivate_pvecs);
651 
652                 get_page(page);
653                 if (!pagevec_add(pvec, page) || PageCompound(page))
654                         pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
655                 put_cpu_var(lru_deactivate_pvecs);
656         }
657 }
658 
659 void lru_add_drain(void)
660 {
661         lru_add_drain_cpu(get_cpu());
662         put_cpu();
663 }
664 
665 static void lru_add_drain_per_cpu(struct work_struct *dummy)
666 {
667         lru_add_drain();
668 }
669 
670 static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work);
671 
672 /*
673  * lru_add_drain_wq is used to do lru_add_drain_all() from a WQ_MEM_RECLAIM
674  * workqueue, aiding in getting memory freed.
675  */
676 static struct workqueue_struct *lru_add_drain_wq;
677 
678 static int __init lru_init(void)
679 {
680         lru_add_drain_wq = alloc_workqueue("lru-add-drain", WQ_MEM_RECLAIM, 0);
681 
682         if (WARN(!lru_add_drain_wq,
683                 "Failed to create workqueue lru_add_drain_wq"))
684                 return -ENOMEM;
685 
686         return 0;
687 }
688 early_initcall(lru_init);
689 
690 void lru_add_drain_all(void)
691 {
692         static DEFINE_MUTEX(lock);
693         static struct cpumask has_work;
694         int cpu;
695 
696         mutex_lock(&lock);
697         get_online_cpus();
698         cpumask_clear(&has_work);
699 
700         for_each_online_cpu(cpu) {
701                 struct work_struct *work = &per_cpu(lru_add_drain_work, cpu);
702 
703                 if (pagevec_count(&per_cpu(lru_add_pvec, cpu)) ||
704                     pagevec_count(&per_cpu(lru_rotate_pvecs, cpu)) ||
705                     pagevec_count(&per_cpu(lru_deactivate_file_pvecs, cpu)) ||
706                     pagevec_count(&per_cpu(lru_deactivate_pvecs, cpu)) ||
707                     need_activate_page_drain(cpu)) {
708                         INIT_WORK(work, lru_add_drain_per_cpu);
709                         queue_work_on(cpu, lru_add_drain_wq, work);
710                         cpumask_set_cpu(cpu, &has_work);
711                 }
712         }
713 
714         for_each_cpu(cpu, &has_work)
715                 flush_work(&per_cpu(lru_add_drain_work, cpu));
716 
717         put_online_cpus();
718         mutex_unlock(&lock);
719 }
720 
721 /**
722  * release_pages - batched put_page()
723  * @pages: array of pages to release
724  * @nr: number of pages
725  * @cold: whether the pages are cache cold
726  *
727  * Decrement the reference count on all the pages in @pages.  If it
728  * fell to zero, remove the page from the LRU and free it.
729  */
730 void release_pages(struct page **pages, int nr, bool cold)
731 {
732         int i;
733         LIST_HEAD(pages_to_free);
734         struct pglist_data *locked_pgdat = NULL;
735         struct lruvec *lruvec;
736         unsigned long uninitialized_var(flags);
737         unsigned int uninitialized_var(lock_batch);
738 
739         for (i = 0; i < nr; i++) {
740                 struct page *page = pages[i];
741 
742                 /*
743                  * Make sure the IRQ-safe lock-holding time does not get
744                  * excessive with a continuous string of pages from the
745                  * same pgdat. The lock is held only if pgdat != NULL.
746                  */
747                 if (locked_pgdat && ++lock_batch == SWAP_CLUSTER_MAX) {
748                         spin_unlock_irqrestore(&locked_pgdat->lru_lock, flags);
749                         locked_pgdat = NULL;
750                 }
751 
752                 if (is_huge_zero_page(page))
753                         continue;
754 
755                 page = compound_head(page);
756                 if (!put_page_testzero(page))
757                         continue;
758 
759                 if (PageCompound(page)) {
760                         if (locked_pgdat) {
761                                 spin_unlock_irqrestore(&locked_pgdat->lru_lock, flags);
762                                 locked_pgdat = NULL;
763                         }
764                         __put_compound_page(page);
765                         continue;
766                 }
767 
768                 if (PageLRU(page)) {
769                         struct pglist_data *pgdat = page_pgdat(page);
770 
771                         if (pgdat != locked_pgdat) {
772                                 if (locked_pgdat)
773                                         spin_unlock_irqrestore(&locked_pgdat->lru_lock,
774                                                                         flags);
775                                 lock_batch = 0;
776                                 locked_pgdat = pgdat;
777                                 spin_lock_irqsave(&locked_pgdat->lru_lock, flags);
778                         }
779 
780                         lruvec = mem_cgroup_page_lruvec(page, locked_pgdat);
781                         VM_BUG_ON_PAGE(!PageLRU(page), page);
782                         __ClearPageLRU(page);
783                         del_page_from_lru_list(page, lruvec, page_off_lru(page));
784                 }
785 
786                 /* Clear Active bit in case of parallel mark_page_accessed */
787                 __ClearPageActive(page);
788                 __ClearPageWaiters(page);
789 
790                 list_add(&page->lru, &pages_to_free);
791         }
792         if (locked_pgdat)
793                 spin_unlock_irqrestore(&locked_pgdat->lru_lock, flags);
794 
795         mem_cgroup_uncharge_list(&pages_to_free);
796         free_hot_cold_page_list(&pages_to_free, cold);
797 }
798 EXPORT_SYMBOL(release_pages);
799 
800 /*
801  * The pages which we're about to release may be in the deferred lru-addition
802  * queues.  That would prevent them from really being freed right now.  That's
803  * OK from a correctness point of view but is inefficient - those pages may be
804  * cache-warm and we want to give them back to the page allocator ASAP.
805  *
806  * So __pagevec_release() will drain those queues here.  __pagevec_lru_add()
807  * and __pagevec_lru_add_active() call release_pages() directly to avoid
808  * mutual recursion.
809  */
810 void __pagevec_release(struct pagevec *pvec)
811 {
812         lru_add_drain();
813         release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
814         pagevec_reinit(pvec);
815 }
816 EXPORT_SYMBOL(__pagevec_release);
817 
818 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
819 /* used by __split_huge_page_refcount() */
820 void lru_add_page_tail(struct page *page, struct page *page_tail,
821                        struct lruvec *lruvec, struct list_head *list)
822 {
823         const int file = 0;
824 
825         VM_BUG_ON_PAGE(!PageHead(page), page);
826         VM_BUG_ON_PAGE(PageCompound(page_tail), page);
827         VM_BUG_ON_PAGE(PageLRU(page_tail), page);
828         VM_BUG_ON(NR_CPUS != 1 &&
829                   !spin_is_locked(&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         int file = page_is_file_cache(page);
863         int active = PageActive(page);
864         enum lru_list lru = page_lru(page);
865 
866         VM_BUG_ON_PAGE(PageLRU(page), page);
867 
868         SetPageLRU(page);
869         add_page_to_lru_list(page, lruvec, lru);
870         update_page_reclaim_stat(lruvec, file, active);
871         trace_mm_lru_insertion(page, lru);
872 }
873 
874 /*
875  * Add the passed pages to the LRU, then drop the caller's refcount
876  * on them.  Reinitialises the caller's pagevec.
877  */
878 void __pagevec_lru_add(struct pagevec *pvec)
879 {
880         pagevec_lru_move_fn(pvec, __pagevec_lru_add_fn, NULL);
881 }
882 EXPORT_SYMBOL(__pagevec_lru_add);
883 
884 /**
885  * pagevec_lookup_entries - gang pagecache lookup
886  * @pvec:       Where the resulting entries are placed
887  * @mapping:    The address_space to search
888  * @start:      The starting entry index
889  * @nr_entries: The maximum number of entries
890  * @indices:    The cache indices corresponding to the entries in @pvec
891  *
892  * pagevec_lookup_entries() will search for and return a group of up
893  * to @nr_entries pages and shadow entries in the mapping.  All
894  * entries are placed in @pvec.  pagevec_lookup_entries() takes a
895  * reference against actual pages in @pvec.
896  *
897  * The search returns a group of mapping-contiguous entries with
898  * ascending indexes.  There may be holes in the indices due to
899  * not-present entries.
900  *
901  * pagevec_lookup_entries() returns the number of entries which were
902  * found.
903  */
904 unsigned pagevec_lookup_entries(struct pagevec *pvec,
905                                 struct address_space *mapping,
906                                 pgoff_t start, unsigned nr_pages,
907                                 pgoff_t *indices)
908 {
909         pvec->nr = find_get_entries(mapping, start, nr_pages,
910                                     pvec->pages, indices);
911         return pagevec_count(pvec);
912 }
913 
914 /**
915  * pagevec_remove_exceptionals - pagevec exceptionals pruning
916  * @pvec:       The pagevec to prune
917  *
918  * pagevec_lookup_entries() fills both pages and exceptional radix
919  * tree entries into the pagevec.  This function prunes all
920  * exceptionals from @pvec without leaving holes, so that it can be
921  * passed on to page-only pagevec operations.
922  */
923 void pagevec_remove_exceptionals(struct pagevec *pvec)
924 {
925         int i, j;
926 
927         for (i = 0, j = 0; i < pagevec_count(pvec); i++) {
928                 struct page *page = pvec->pages[i];
929                 if (!radix_tree_exceptional_entry(page))
930                         pvec->pages[j++] = page;
931         }
932         pvec->nr = j;
933 }
934 
935 /**
936  * pagevec_lookup - gang pagecache lookup
937  * @pvec:       Where the resulting pages are placed
938  * @mapping:    The address_space to search
939  * @start:      The starting page index
940  * @nr_pages:   The maximum number of pages
941  *
942  * pagevec_lookup() will search for and return a group of up to @nr_pages pages
943  * in the mapping.  The pages are placed in @pvec.  pagevec_lookup() takes a
944  * reference against the pages in @pvec.
945  *
946  * The search returns a group of mapping-contiguous pages with ascending
947  * indexes.  There may be holes in the indices due to not-present pages.
948  *
949  * pagevec_lookup() returns the number of pages which were found.
950  */
951 unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
952                 pgoff_t start, unsigned nr_pages)
953 {
954         pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
955         return pagevec_count(pvec);
956 }
957 EXPORT_SYMBOL(pagevec_lookup);
958 
959 unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping,
960                 pgoff_t *index, int tag, unsigned nr_pages)
961 {
962         pvec->nr = find_get_pages_tag(mapping, index, tag,
963                                         nr_pages, pvec->pages);
964         return pagevec_count(pvec);
965 }
966 EXPORT_SYMBOL(pagevec_lookup_tag);
967 
968 /*
969  * Perform any setup for the swap system
970  */
971 void __init swap_setup(void)
972 {
973         unsigned long megs = totalram_pages >> (20 - PAGE_SHIFT);
974 #ifdef CONFIG_SWAP
975         int i;
976 
977         for (i = 0; i < MAX_SWAPFILES; i++)
978                 spin_lock_init(&swapper_spaces[i].tree_lock);
979 #endif
980 
981         /* Use a smaller cluster for small-memory machines */
982         if (megs < 16)
983                 page_cluster = 2;
984         else
985                 page_cluster = 3;
986         /*
987          * Right now other parts of the system means that we
988          * _really_ don't want to cluster much more
989          */
990 }
991 

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