Merge tag 'trace-fixes-v3.14-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git...
[platform/adaptation/renesas_rcar/renesas_kernel.git] / 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/percpu.h>
28 #include <linux/cpu.h>
29 #include <linux/notifier.h>
30 #include <linux/backing-dev.h>
31 #include <linux/memcontrol.h>
32 #include <linux/gfp.h>
33 #include <linux/uio.h>
34
35 #include "internal.h"
36
37 #define CREATE_TRACE_POINTS
38 #include <trace/events/pagemap.h>
39
40 /* How many pages do we try to swap or page in/out together? */
41 int page_cluster;
42
43 static DEFINE_PER_CPU(struct pagevec, lru_add_pvec);
44 static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs);
45 static DEFINE_PER_CPU(struct pagevec, lru_deactivate_pvecs);
46
47 /*
48  * This path almost never happens for VM activity - pages are normally
49  * freed via pagevecs.  But it gets used by networking.
50  */
51 static void __page_cache_release(struct page *page)
52 {
53         if (PageLRU(page)) {
54                 struct zone *zone = page_zone(page);
55                 struct lruvec *lruvec;
56                 unsigned long flags;
57
58                 spin_lock_irqsave(&zone->lru_lock, flags);
59                 lruvec = mem_cgroup_page_lruvec(page, zone);
60                 VM_BUG_ON_PAGE(!PageLRU(page), page);
61                 __ClearPageLRU(page);
62                 del_page_from_lru_list(page, lruvec, page_off_lru(page));
63                 spin_unlock_irqrestore(&zone->lru_lock, flags);
64         }
65 }
66
67 static void __put_single_page(struct page *page)
68 {
69         __page_cache_release(page);
70         free_hot_cold_page(page, 0);
71 }
72
73 static void __put_compound_page(struct page *page)
74 {
75         compound_page_dtor *dtor;
76
77         __page_cache_release(page);
78         dtor = get_compound_page_dtor(page);
79         (*dtor)(page);
80 }
81
82 static void put_compound_page(struct page *page)
83 {
84         struct page *page_head;
85
86         if (likely(!PageTail(page))) {
87                 if (put_page_testzero(page)) {
88                         /*
89                          * By the time all refcounts have been released
90                          * split_huge_page cannot run anymore from under us.
91                          */
92                         if (PageHead(page))
93                                 __put_compound_page(page);
94                         else
95                                 __put_single_page(page);
96                 }
97                 return;
98         }
99
100         /* __split_huge_page_refcount can run under us */
101         page_head = compound_head(page);
102
103         /*
104          * THP can not break up slab pages so avoid taking
105          * compound_lock() and skip the tail page refcounting (in
106          * _mapcount) too. Slab performs non-atomic bit ops on
107          * page->flags for better performance. In particular
108          * slab_unlock() in slub used to be a hot path. It is still
109          * hot on arches that do not support
110          * this_cpu_cmpxchg_double().
111          *
112          * If "page" is part of a slab or hugetlbfs page it cannot be
113          * splitted and the head page cannot change from under us. And
114          * if "page" is part of a THP page under splitting, if the
115          * head page pointed by the THP tail isn't a THP head anymore,
116          * we'll find PageTail clear after smp_rmb() and we'll treat
117          * it as a single page.
118          */
119         if (!__compound_tail_refcounted(page_head)) {
120                 /*
121                  * If "page" is a THP tail, we must read the tail page
122                  * flags after the head page flags. The
123                  * split_huge_page side enforces write memory barriers
124                  * between clearing PageTail and before the head page
125                  * can be freed and reallocated.
126                  */
127                 smp_rmb();
128                 if (likely(PageTail(page))) {
129                         /*
130                          * __split_huge_page_refcount cannot race
131                          * here.
132                          */
133                         VM_BUG_ON_PAGE(!PageHead(page_head), page_head);
134                         VM_BUG_ON_PAGE(page_mapcount(page) != 0, page);
135                         if (put_page_testzero(page_head)) {
136                                 /*
137                                  * If this is the tail of a slab
138                                  * compound page, the tail pin must
139                                  * not be the last reference held on
140                                  * the page, because the PG_slab
141                                  * cannot be cleared before all tail
142                                  * pins (which skips the _mapcount
143                                  * tail refcounting) have been
144                                  * released. For hugetlbfs the tail
145                                  * pin may be the last reference on
146                                  * the page instead, because
147                                  * PageHeadHuge will not go away until
148                                  * the compound page enters the buddy
149                                  * allocator.
150                                  */
151                                 VM_BUG_ON_PAGE(PageSlab(page_head), page_head);
152                                 __put_compound_page(page_head);
153                         }
154                         return;
155                 } else
156                         /*
157                          * __split_huge_page_refcount run before us,
158                          * "page" was a THP tail. The split page_head
159                          * has been freed and reallocated as slab or
160                          * hugetlbfs page of smaller order (only
161                          * possible if reallocated as slab on x86).
162                          */
163                         goto out_put_single;
164         }
165
166         if (likely(page != page_head && get_page_unless_zero(page_head))) {
167                 unsigned long flags;
168
169                 /*
170                  * page_head wasn't a dangling pointer but it may not
171                  * be a head page anymore by the time we obtain the
172                  * lock. That is ok as long as it can't be freed from
173                  * under us.
174                  */
175                 flags = compound_lock_irqsave(page_head);
176                 if (unlikely(!PageTail(page))) {
177                         /* __split_huge_page_refcount run before us */
178                         compound_unlock_irqrestore(page_head, flags);
179                         if (put_page_testzero(page_head)) {
180                                 /*
181                                  * The head page may have been freed
182                                  * and reallocated as a compound page
183                                  * of smaller order and then freed
184                                  * again.  All we know is that it
185                                  * cannot have become: a THP page, a
186                                  * compound page of higher order, a
187                                  * tail page.  That is because we
188                                  * still hold the refcount of the
189                                  * split THP tail and page_head was
190                                  * the THP head before the split.
191                                  */
192                                 if (PageHead(page_head))
193                                         __put_compound_page(page_head);
194                                 else
195                                         __put_single_page(page_head);
196                         }
197 out_put_single:
198                         if (put_page_testzero(page))
199                                 __put_single_page(page);
200                         return;
201                 }
202                 VM_BUG_ON_PAGE(page_head != page->first_page, page);
203                 /*
204                  * We can release the refcount taken by
205                  * get_page_unless_zero() now that
206                  * __split_huge_page_refcount() is blocked on the
207                  * compound_lock.
208                  */
209                 if (put_page_testzero(page_head))
210                         VM_BUG_ON_PAGE(1, page_head);
211                 /* __split_huge_page_refcount will wait now */
212                 VM_BUG_ON_PAGE(page_mapcount(page) <= 0, page);
213                 atomic_dec(&page->_mapcount);
214                 VM_BUG_ON_PAGE(atomic_read(&page_head->_count) <= 0, page_head);
215                 VM_BUG_ON_PAGE(atomic_read(&page->_count) != 0, page);
216                 compound_unlock_irqrestore(page_head, flags);
217
218                 if (put_page_testzero(page_head)) {
219                         if (PageHead(page_head))
220                                 __put_compound_page(page_head);
221                         else
222                                 __put_single_page(page_head);
223                 }
224         } else {
225                 /* page_head is a dangling pointer */
226                 VM_BUG_ON_PAGE(PageTail(page), page);
227                 goto out_put_single;
228         }
229 }
230
231 void put_page(struct page *page)
232 {
233         if (unlikely(PageCompound(page)))
234                 put_compound_page(page);
235         else if (put_page_testzero(page))
236                 __put_single_page(page);
237 }
238 EXPORT_SYMBOL(put_page);
239
240 /*
241  * This function is exported but must not be called by anything other
242  * than get_page(). It implements the slow path of get_page().
243  */
244 bool __get_page_tail(struct page *page)
245 {
246         /*
247          * This takes care of get_page() if run on a tail page
248          * returned by one of the get_user_pages/follow_page variants.
249          * get_user_pages/follow_page itself doesn't need the compound
250          * lock because it runs __get_page_tail_foll() under the
251          * proper PT lock that already serializes against
252          * split_huge_page().
253          */
254         unsigned long flags;
255         bool got;
256         struct page *page_head = compound_head(page);
257
258         /* Ref to put_compound_page() comment. */
259         if (!__compound_tail_refcounted(page_head)) {
260                 smp_rmb();
261                 if (likely(PageTail(page))) {
262                         /*
263                          * This is a hugetlbfs page or a slab
264                          * page. __split_huge_page_refcount
265                          * cannot race here.
266                          */
267                         VM_BUG_ON_PAGE(!PageHead(page_head), page_head);
268                         __get_page_tail_foll(page, true);
269                         return true;
270                 } else {
271                         /*
272                          * __split_huge_page_refcount run
273                          * before us, "page" was a THP
274                          * tail. The split page_head has been
275                          * freed and reallocated as slab or
276                          * hugetlbfs page of smaller order
277                          * (only possible if reallocated as
278                          * slab on x86).
279                          */
280                         return false;
281                 }
282         }
283
284         got = false;
285         if (likely(page != page_head && get_page_unless_zero(page_head))) {
286                 /*
287                  * page_head wasn't a dangling pointer but it
288                  * may not be a head page anymore by the time
289                  * we obtain the lock. That is ok as long as it
290                  * can't be freed from under us.
291                  */
292                 flags = compound_lock_irqsave(page_head);
293                 /* here __split_huge_page_refcount won't run anymore */
294                 if (likely(PageTail(page))) {
295                         __get_page_tail_foll(page, false);
296                         got = true;
297                 }
298                 compound_unlock_irqrestore(page_head, flags);
299                 if (unlikely(!got))
300                         put_page(page_head);
301         }
302         return got;
303 }
304 EXPORT_SYMBOL(__get_page_tail);
305
306 /**
307  * put_pages_list() - release a list of pages
308  * @pages: list of pages threaded on page->lru
309  *
310  * Release a list of pages which are strung together on page.lru.  Currently
311  * used by read_cache_pages() and related error recovery code.
312  */
313 void put_pages_list(struct list_head *pages)
314 {
315         while (!list_empty(pages)) {
316                 struct page *victim;
317
318                 victim = list_entry(pages->prev, struct page, lru);
319                 list_del(&victim->lru);
320                 page_cache_release(victim);
321         }
322 }
323 EXPORT_SYMBOL(put_pages_list);
324
325 /*
326  * get_kernel_pages() - pin kernel pages in memory
327  * @kiov:       An array of struct kvec structures
328  * @nr_segs:    number of segments to pin
329  * @write:      pinning for read/write, currently ignored
330  * @pages:      array that receives pointers to the pages pinned.
331  *              Should be at least nr_segs long.
332  *
333  * Returns number of pages pinned. This may be fewer than the number
334  * requested. If nr_pages is 0 or negative, returns 0. If no pages
335  * were pinned, returns -errno. Each page returned must be released
336  * with a put_page() call when it is finished with.
337  */
338 int get_kernel_pages(const struct kvec *kiov, int nr_segs, int write,
339                 struct page **pages)
340 {
341         int seg;
342
343         for (seg = 0; seg < nr_segs; seg++) {
344                 if (WARN_ON(kiov[seg].iov_len != PAGE_SIZE))
345                         return seg;
346
347                 pages[seg] = kmap_to_page(kiov[seg].iov_base);
348                 page_cache_get(pages[seg]);
349         }
350
351         return seg;
352 }
353 EXPORT_SYMBOL_GPL(get_kernel_pages);
354
355 /*
356  * get_kernel_page() - pin a kernel page in memory
357  * @start:      starting kernel address
358  * @write:      pinning for read/write, currently ignored
359  * @pages:      array that receives pointer to the page pinned.
360  *              Must be at least nr_segs long.
361  *
362  * Returns 1 if page is pinned. If the page was not pinned, returns
363  * -errno. The page returned must be released with a put_page() call
364  * when it is finished with.
365  */
366 int get_kernel_page(unsigned long start, int write, struct page **pages)
367 {
368         const struct kvec kiov = {
369                 .iov_base = (void *)start,
370                 .iov_len = PAGE_SIZE
371         };
372
373         return get_kernel_pages(&kiov, 1, write, pages);
374 }
375 EXPORT_SYMBOL_GPL(get_kernel_page);
376
377 static void pagevec_lru_move_fn(struct pagevec *pvec,
378         void (*move_fn)(struct page *page, struct lruvec *lruvec, void *arg),
379         void *arg)
380 {
381         int i;
382         struct zone *zone = NULL;
383         struct lruvec *lruvec;
384         unsigned long flags = 0;
385
386         for (i = 0; i < pagevec_count(pvec); i++) {
387                 struct page *page = pvec->pages[i];
388                 struct zone *pagezone = page_zone(page);
389
390                 if (pagezone != zone) {
391                         if (zone)
392                                 spin_unlock_irqrestore(&zone->lru_lock, flags);
393                         zone = pagezone;
394                         spin_lock_irqsave(&zone->lru_lock, flags);
395                 }
396
397                 lruvec = mem_cgroup_page_lruvec(page, zone);
398                 (*move_fn)(page, lruvec, arg);
399         }
400         if (zone)
401                 spin_unlock_irqrestore(&zone->lru_lock, flags);
402         release_pages(pvec->pages, pvec->nr, pvec->cold);
403         pagevec_reinit(pvec);
404 }
405
406 static void pagevec_move_tail_fn(struct page *page, struct lruvec *lruvec,
407                                  void *arg)
408 {
409         int *pgmoved = arg;
410
411         if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
412                 enum lru_list lru = page_lru_base_type(page);
413                 list_move_tail(&page->lru, &lruvec->lists[lru]);
414                 (*pgmoved)++;
415         }
416 }
417
418 /*
419  * pagevec_move_tail() must be called with IRQ disabled.
420  * Otherwise this may cause nasty races.
421  */
422 static void pagevec_move_tail(struct pagevec *pvec)
423 {
424         int pgmoved = 0;
425
426         pagevec_lru_move_fn(pvec, pagevec_move_tail_fn, &pgmoved);
427         __count_vm_events(PGROTATED, pgmoved);
428 }
429
430 /*
431  * Writeback is about to end against a page which has been marked for immediate
432  * reclaim.  If it still appears to be reclaimable, move it to the tail of the
433  * inactive list.
434  */
435 void rotate_reclaimable_page(struct page *page)
436 {
437         if (!PageLocked(page) && !PageDirty(page) && !PageActive(page) &&
438             !PageUnevictable(page) && PageLRU(page)) {
439                 struct pagevec *pvec;
440                 unsigned long flags;
441
442                 page_cache_get(page);
443                 local_irq_save(flags);
444                 pvec = &__get_cpu_var(lru_rotate_pvecs);
445                 if (!pagevec_add(pvec, page))
446                         pagevec_move_tail(pvec);
447                 local_irq_restore(flags);
448         }
449 }
450
451 static void update_page_reclaim_stat(struct lruvec *lruvec,
452                                      int file, int rotated)
453 {
454         struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
455
456         reclaim_stat->recent_scanned[file]++;
457         if (rotated)
458                 reclaim_stat->recent_rotated[file]++;
459 }
460
461 static void __activate_page(struct page *page, struct lruvec *lruvec,
462                             void *arg)
463 {
464         if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
465                 int file = page_is_file_cache(page);
466                 int lru = page_lru_base_type(page);
467
468                 del_page_from_lru_list(page, lruvec, lru);
469                 SetPageActive(page);
470                 lru += LRU_ACTIVE;
471                 add_page_to_lru_list(page, lruvec, lru);
472                 trace_mm_lru_activate(page, page_to_pfn(page));
473
474                 __count_vm_event(PGACTIVATE);
475                 update_page_reclaim_stat(lruvec, file, 1);
476         }
477 }
478
479 #ifdef CONFIG_SMP
480 static DEFINE_PER_CPU(struct pagevec, activate_page_pvecs);
481
482 static void activate_page_drain(int cpu)
483 {
484         struct pagevec *pvec = &per_cpu(activate_page_pvecs, cpu);
485
486         if (pagevec_count(pvec))
487                 pagevec_lru_move_fn(pvec, __activate_page, NULL);
488 }
489
490 static bool need_activate_page_drain(int cpu)
491 {
492         return pagevec_count(&per_cpu(activate_page_pvecs, cpu)) != 0;
493 }
494
495 void activate_page(struct page *page)
496 {
497         if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
498                 struct pagevec *pvec = &get_cpu_var(activate_page_pvecs);
499
500                 page_cache_get(page);
501                 if (!pagevec_add(pvec, page))
502                         pagevec_lru_move_fn(pvec, __activate_page, NULL);
503                 put_cpu_var(activate_page_pvecs);
504         }
505 }
506
507 #else
508 static inline void activate_page_drain(int cpu)
509 {
510 }
511
512 static bool need_activate_page_drain(int cpu)
513 {
514         return false;
515 }
516
517 void activate_page(struct page *page)
518 {
519         struct zone *zone = page_zone(page);
520
521         spin_lock_irq(&zone->lru_lock);
522         __activate_page(page, mem_cgroup_page_lruvec(page, zone), NULL);
523         spin_unlock_irq(&zone->lru_lock);
524 }
525 #endif
526
527 static void __lru_cache_activate_page(struct page *page)
528 {
529         struct pagevec *pvec = &get_cpu_var(lru_add_pvec);
530         int i;
531
532         /*
533          * Search backwards on the optimistic assumption that the page being
534          * activated has just been added to this pagevec. Note that only
535          * the local pagevec is examined as a !PageLRU page could be in the
536          * process of being released, reclaimed, migrated or on a remote
537          * pagevec that is currently being drained. Furthermore, marking
538          * a remote pagevec's page PageActive potentially hits a race where
539          * a page is marked PageActive just after it is added to the inactive
540          * list causing accounting errors and BUG_ON checks to trigger.
541          */
542         for (i = pagevec_count(pvec) - 1; i >= 0; i--) {
543                 struct page *pagevec_page = pvec->pages[i];
544
545                 if (pagevec_page == page) {
546                         SetPageActive(page);
547                         break;
548                 }
549         }
550
551         put_cpu_var(lru_add_pvec);
552 }
553
554 /*
555  * Mark a page as having seen activity.
556  *
557  * inactive,unreferenced        ->      inactive,referenced
558  * inactive,referenced          ->      active,unreferenced
559  * active,unreferenced          ->      active,referenced
560  */
561 void mark_page_accessed(struct page *page)
562 {
563         if (!PageActive(page) && !PageUnevictable(page) &&
564                         PageReferenced(page)) {
565
566                 /*
567                  * If the page is on the LRU, queue it for activation via
568                  * activate_page_pvecs. Otherwise, assume the page is on a
569                  * pagevec, mark it active and it'll be moved to the active
570                  * LRU on the next drain.
571                  */
572                 if (PageLRU(page))
573                         activate_page(page);
574                 else
575                         __lru_cache_activate_page(page);
576                 ClearPageReferenced(page);
577         } else if (!PageReferenced(page)) {
578                 SetPageReferenced(page);
579         }
580 }
581 EXPORT_SYMBOL(mark_page_accessed);
582
583 /*
584  * Queue the page for addition to the LRU via pagevec. The decision on whether
585  * to add the page to the [in]active [file|anon] list is deferred until the
586  * pagevec is drained. This gives a chance for the caller of __lru_cache_add()
587  * have the page added to the active list using mark_page_accessed().
588  */
589 void __lru_cache_add(struct page *page)
590 {
591         struct pagevec *pvec = &get_cpu_var(lru_add_pvec);
592
593         page_cache_get(page);
594         if (!pagevec_space(pvec))
595                 __pagevec_lru_add(pvec);
596         pagevec_add(pvec, page);
597         put_cpu_var(lru_add_pvec);
598 }
599 EXPORT_SYMBOL(__lru_cache_add);
600
601 /**
602  * lru_cache_add - add a page to a page list
603  * @page: the page to be added to the LRU.
604  */
605 void lru_cache_add(struct page *page)
606 {
607         VM_BUG_ON_PAGE(PageActive(page) && PageUnevictable(page), page);
608         VM_BUG_ON_PAGE(PageLRU(page), page);
609         __lru_cache_add(page);
610 }
611
612 /**
613  * add_page_to_unevictable_list - add a page to the unevictable list
614  * @page:  the page to be added to the unevictable list
615  *
616  * Add page directly to its zone's unevictable list.  To avoid races with
617  * tasks that might be making the page evictable, through eg. munlock,
618  * munmap or exit, while it's not on the lru, we want to add the page
619  * while it's locked or otherwise "invisible" to other tasks.  This is
620  * difficult to do when using the pagevec cache, so bypass that.
621  */
622 void add_page_to_unevictable_list(struct page *page)
623 {
624         struct zone *zone = page_zone(page);
625         struct lruvec *lruvec;
626
627         spin_lock_irq(&zone->lru_lock);
628         lruvec = mem_cgroup_page_lruvec(page, zone);
629         ClearPageActive(page);
630         SetPageUnevictable(page);
631         SetPageLRU(page);
632         add_page_to_lru_list(page, lruvec, LRU_UNEVICTABLE);
633         spin_unlock_irq(&zone->lru_lock);
634 }
635
636 /*
637  * If the page can not be invalidated, it is moved to the
638  * inactive list to speed up its reclaim.  It is moved to the
639  * head of the list, rather than the tail, to give the flusher
640  * threads some time to write it out, as this is much more
641  * effective than the single-page writeout from reclaim.
642  *
643  * If the page isn't page_mapped and dirty/writeback, the page
644  * could reclaim asap using PG_reclaim.
645  *
646  * 1. active, mapped page -> none
647  * 2. active, dirty/writeback page -> inactive, head, PG_reclaim
648  * 3. inactive, mapped page -> none
649  * 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim
650  * 5. inactive, clean -> inactive, tail
651  * 6. Others -> none
652  *
653  * In 4, why it moves inactive's head, the VM expects the page would
654  * be write it out by flusher threads as this is much more effective
655  * than the single-page writeout from reclaim.
656  */
657 static void lru_deactivate_fn(struct page *page, struct lruvec *lruvec,
658                               void *arg)
659 {
660         int lru, file;
661         bool active;
662
663         if (!PageLRU(page))
664                 return;
665
666         if (PageUnevictable(page))
667                 return;
668
669         /* Some processes are using the page */
670         if (page_mapped(page))
671                 return;
672
673         active = PageActive(page);
674         file = page_is_file_cache(page);
675         lru = page_lru_base_type(page);
676
677         del_page_from_lru_list(page, lruvec, lru + active);
678         ClearPageActive(page);
679         ClearPageReferenced(page);
680         add_page_to_lru_list(page, lruvec, lru);
681
682         if (PageWriteback(page) || PageDirty(page)) {
683                 /*
684                  * PG_reclaim could be raced with end_page_writeback
685                  * It can make readahead confusing.  But race window
686                  * is _really_ small and  it's non-critical problem.
687                  */
688                 SetPageReclaim(page);
689         } else {
690                 /*
691                  * The page's writeback ends up during pagevec
692                  * We moves tha page into tail of inactive.
693                  */
694                 list_move_tail(&page->lru, &lruvec->lists[lru]);
695                 __count_vm_event(PGROTATED);
696         }
697
698         if (active)
699                 __count_vm_event(PGDEACTIVATE);
700         update_page_reclaim_stat(lruvec, file, 0);
701 }
702
703 /*
704  * Drain pages out of the cpu's pagevecs.
705  * Either "cpu" is the current CPU, and preemption has already been
706  * disabled; or "cpu" is being hot-unplugged, and is already dead.
707  */
708 void lru_add_drain_cpu(int cpu)
709 {
710         struct pagevec *pvec = &per_cpu(lru_add_pvec, cpu);
711
712         if (pagevec_count(pvec))
713                 __pagevec_lru_add(pvec);
714
715         pvec = &per_cpu(lru_rotate_pvecs, cpu);
716         if (pagevec_count(pvec)) {
717                 unsigned long flags;
718
719                 /* No harm done if a racing interrupt already did this */
720                 local_irq_save(flags);
721                 pagevec_move_tail(pvec);
722                 local_irq_restore(flags);
723         }
724
725         pvec = &per_cpu(lru_deactivate_pvecs, cpu);
726         if (pagevec_count(pvec))
727                 pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
728
729         activate_page_drain(cpu);
730 }
731
732 /**
733  * deactivate_page - forcefully deactivate a page
734  * @page: page to deactivate
735  *
736  * This function hints the VM that @page is a good reclaim candidate,
737  * for example if its invalidation fails due to the page being dirty
738  * or under writeback.
739  */
740 void deactivate_page(struct page *page)
741 {
742         /*
743          * In a workload with many unevictable page such as mprotect, unevictable
744          * page deactivation for accelerating reclaim is pointless.
745          */
746         if (PageUnevictable(page))
747                 return;
748
749         if (likely(get_page_unless_zero(page))) {
750                 struct pagevec *pvec = &get_cpu_var(lru_deactivate_pvecs);
751
752                 if (!pagevec_add(pvec, page))
753                         pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
754                 put_cpu_var(lru_deactivate_pvecs);
755         }
756 }
757
758 void lru_add_drain(void)
759 {
760         lru_add_drain_cpu(get_cpu());
761         put_cpu();
762 }
763
764 static void lru_add_drain_per_cpu(struct work_struct *dummy)
765 {
766         lru_add_drain();
767 }
768
769 static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work);
770
771 void lru_add_drain_all(void)
772 {
773         static DEFINE_MUTEX(lock);
774         static struct cpumask has_work;
775         int cpu;
776
777         mutex_lock(&lock);
778         get_online_cpus();
779         cpumask_clear(&has_work);
780
781         for_each_online_cpu(cpu) {
782                 struct work_struct *work = &per_cpu(lru_add_drain_work, cpu);
783
784                 if (pagevec_count(&per_cpu(lru_add_pvec, cpu)) ||
785                     pagevec_count(&per_cpu(lru_rotate_pvecs, cpu)) ||
786                     pagevec_count(&per_cpu(lru_deactivate_pvecs, cpu)) ||
787                     need_activate_page_drain(cpu)) {
788                         INIT_WORK(work, lru_add_drain_per_cpu);
789                         schedule_work_on(cpu, work);
790                         cpumask_set_cpu(cpu, &has_work);
791                 }
792         }
793
794         for_each_cpu(cpu, &has_work)
795                 flush_work(&per_cpu(lru_add_drain_work, cpu));
796
797         put_online_cpus();
798         mutex_unlock(&lock);
799 }
800
801 /*
802  * Batched page_cache_release().  Decrement the reference count on all the
803  * passed pages.  If it fell to zero then remove the page from the LRU and
804  * free it.
805  *
806  * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
807  * for the remainder of the operation.
808  *
809  * The locking in this function is against shrink_inactive_list(): we recheck
810  * the page count inside the lock to see whether shrink_inactive_list()
811  * grabbed the page via the LRU.  If it did, give up: shrink_inactive_list()
812  * will free it.
813  */
814 void release_pages(struct page **pages, int nr, int cold)
815 {
816         int i;
817         LIST_HEAD(pages_to_free);
818         struct zone *zone = NULL;
819         struct lruvec *lruvec;
820         unsigned long uninitialized_var(flags);
821
822         for (i = 0; i < nr; i++) {
823                 struct page *page = pages[i];
824
825                 if (unlikely(PageCompound(page))) {
826                         if (zone) {
827                                 spin_unlock_irqrestore(&zone->lru_lock, flags);
828                                 zone = NULL;
829                         }
830                         put_compound_page(page);
831                         continue;
832                 }
833
834                 if (!put_page_testzero(page))
835                         continue;
836
837                 if (PageLRU(page)) {
838                         struct zone *pagezone = page_zone(page);
839
840                         if (pagezone != zone) {
841                                 if (zone)
842                                         spin_unlock_irqrestore(&zone->lru_lock,
843                                                                         flags);
844                                 zone = pagezone;
845                                 spin_lock_irqsave(&zone->lru_lock, flags);
846                         }
847
848                         lruvec = mem_cgroup_page_lruvec(page, zone);
849                         VM_BUG_ON_PAGE(!PageLRU(page), page);
850                         __ClearPageLRU(page);
851                         del_page_from_lru_list(page, lruvec, page_off_lru(page));
852                 }
853
854                 /* Clear Active bit in case of parallel mark_page_accessed */
855                 ClearPageActive(page);
856
857                 list_add(&page->lru, &pages_to_free);
858         }
859         if (zone)
860                 spin_unlock_irqrestore(&zone->lru_lock, flags);
861
862         free_hot_cold_page_list(&pages_to_free, cold);
863 }
864 EXPORT_SYMBOL(release_pages);
865
866 /*
867  * The pages which we're about to release may be in the deferred lru-addition
868  * queues.  That would prevent them from really being freed right now.  That's
869  * OK from a correctness point of view but is inefficient - those pages may be
870  * cache-warm and we want to give them back to the page allocator ASAP.
871  *
872  * So __pagevec_release() will drain those queues here.  __pagevec_lru_add()
873  * and __pagevec_lru_add_active() call release_pages() directly to avoid
874  * mutual recursion.
875  */
876 void __pagevec_release(struct pagevec *pvec)
877 {
878         lru_add_drain();
879         release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
880         pagevec_reinit(pvec);
881 }
882 EXPORT_SYMBOL(__pagevec_release);
883
884 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
885 /* used by __split_huge_page_refcount() */
886 void lru_add_page_tail(struct page *page, struct page *page_tail,
887                        struct lruvec *lruvec, struct list_head *list)
888 {
889         const int file = 0;
890
891         VM_BUG_ON_PAGE(!PageHead(page), page);
892         VM_BUG_ON_PAGE(PageCompound(page_tail), page);
893         VM_BUG_ON_PAGE(PageLRU(page_tail), page);
894         VM_BUG_ON(NR_CPUS != 1 &&
895                   !spin_is_locked(&lruvec_zone(lruvec)->lru_lock));
896
897         if (!list)
898                 SetPageLRU(page_tail);
899
900         if (likely(PageLRU(page)))
901                 list_add_tail(&page_tail->lru, &page->lru);
902         else if (list) {
903                 /* page reclaim is reclaiming a huge page */
904                 get_page(page_tail);
905                 list_add_tail(&page_tail->lru, list);
906         } else {
907                 struct list_head *list_head;
908                 /*
909                  * Head page has not yet been counted, as an hpage,
910                  * so we must account for each subpage individually.
911                  *
912                  * Use the standard add function to put page_tail on the list,
913                  * but then correct its position so they all end up in order.
914                  */
915                 add_page_to_lru_list(page_tail, lruvec, page_lru(page_tail));
916                 list_head = page_tail->lru.prev;
917                 list_move_tail(&page_tail->lru, list_head);
918         }
919
920         if (!PageUnevictable(page))
921                 update_page_reclaim_stat(lruvec, file, PageActive(page_tail));
922 }
923 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
924
925 static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec,
926                                  void *arg)
927 {
928         int file = page_is_file_cache(page);
929         int active = PageActive(page);
930         enum lru_list lru = page_lru(page);
931
932         VM_BUG_ON_PAGE(PageLRU(page), page);
933
934         SetPageLRU(page);
935         add_page_to_lru_list(page, lruvec, lru);
936         update_page_reclaim_stat(lruvec, file, active);
937         trace_mm_lru_insertion(page, page_to_pfn(page), lru, trace_pagemap_flags(page));
938 }
939
940 /*
941  * Add the passed pages to the LRU, then drop the caller's refcount
942  * on them.  Reinitialises the caller's pagevec.
943  */
944 void __pagevec_lru_add(struct pagevec *pvec)
945 {
946         pagevec_lru_move_fn(pvec, __pagevec_lru_add_fn, NULL);
947 }
948 EXPORT_SYMBOL(__pagevec_lru_add);
949
950 /**
951  * pagevec_lookup - gang pagecache lookup
952  * @pvec:       Where the resulting pages are placed
953  * @mapping:    The address_space to search
954  * @start:      The starting page index
955  * @nr_pages:   The maximum number of pages
956  *
957  * pagevec_lookup() will search for and return a group of up to @nr_pages pages
958  * in the mapping.  The pages are placed in @pvec.  pagevec_lookup() takes a
959  * reference against the pages in @pvec.
960  *
961  * The search returns a group of mapping-contiguous pages with ascending
962  * indexes.  There may be holes in the indices due to not-present pages.
963  *
964  * pagevec_lookup() returns the number of pages which were found.
965  */
966 unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
967                 pgoff_t start, unsigned nr_pages)
968 {
969         pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
970         return pagevec_count(pvec);
971 }
972 EXPORT_SYMBOL(pagevec_lookup);
973
974 unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping,
975                 pgoff_t *index, int tag, unsigned nr_pages)
976 {
977         pvec->nr = find_get_pages_tag(mapping, index, tag,
978                                         nr_pages, pvec->pages);
979         return pagevec_count(pvec);
980 }
981 EXPORT_SYMBOL(pagevec_lookup_tag);
982
983 /*
984  * Perform any setup for the swap system
985  */
986 void __init swap_setup(void)
987 {
988         unsigned long megs = totalram_pages >> (20 - PAGE_SHIFT);
989 #ifdef CONFIG_SWAP
990         int i;
991
992         if (bdi_init(swapper_spaces[0].backing_dev_info))
993                 panic("Failed to init swap bdi");
994         for (i = 0; i < MAX_SWAPFILES; i++) {
995                 spin_lock_init(&swapper_spaces[i].tree_lock);
996                 INIT_LIST_HEAD(&swapper_spaces[i].i_mmap_nonlinear);
997         }
998 #endif
999
1000         /* Use a smaller cluster for small-memory machines */
1001         if (megs < 16)
1002                 page_cluster = 2;
1003         else
1004                 page_cluster = 3;
1005         /*
1006          * Right now other parts of the system means that we
1007          * _really_ don't want to cluster much more
1008          */
1009 }