Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris...
[linux-3.10.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
34 #include "internal.h"
35
36 /* How many pages do we try to swap or page in/out together? */
37 int page_cluster;
38
39 static DEFINE_PER_CPU(struct pagevec[NR_LRU_LISTS], lru_add_pvecs);
40 static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs);
41 static DEFINE_PER_CPU(struct pagevec, lru_deactivate_pvecs);
42
43 /*
44  * This path almost never happens for VM activity - pages are normally
45  * freed via pagevecs.  But it gets used by networking.
46  */
47 static void __page_cache_release(struct page *page)
48 {
49         if (PageLRU(page)) {
50                 struct zone *zone = page_zone(page);
51                 struct lruvec *lruvec;
52                 unsigned long flags;
53
54                 spin_lock_irqsave(&zone->lru_lock, flags);
55                 lruvec = mem_cgroup_page_lruvec(page, zone);
56                 VM_BUG_ON(!PageLRU(page));
57                 __ClearPageLRU(page);
58                 del_page_from_lru_list(page, lruvec, page_off_lru(page));
59                 spin_unlock_irqrestore(&zone->lru_lock, flags);
60         }
61 }
62
63 static void __put_single_page(struct page *page)
64 {
65         __page_cache_release(page);
66         free_hot_cold_page(page, 0);
67 }
68
69 static void __put_compound_page(struct page *page)
70 {
71         compound_page_dtor *dtor;
72
73         __page_cache_release(page);
74         dtor = get_compound_page_dtor(page);
75         (*dtor)(page);
76 }
77
78 static void put_compound_page(struct page *page)
79 {
80         if (unlikely(PageTail(page))) {
81                 /* __split_huge_page_refcount can run under us */
82                 struct page *page_head = compound_trans_head(page);
83
84                 if (likely(page != page_head &&
85                            get_page_unless_zero(page_head))) {
86                         unsigned long flags;
87
88                         /*
89                          * THP can not break up slab pages so avoid taking
90                          * compound_lock().  Slab performs non-atomic bit ops
91                          * on page->flags for better performance.  In particular
92                          * slab_unlock() in slub used to be a hot path.  It is
93                          * still hot on arches that do not support
94                          * this_cpu_cmpxchg_double().
95                          */
96                         if (PageSlab(page_head)) {
97                                 if (PageTail(page)) {
98                                         if (put_page_testzero(page_head))
99                                                 VM_BUG_ON(1);
100
101                                         atomic_dec(&page->_mapcount);
102                                         goto skip_lock_tail;
103                                 } else
104                                         goto skip_lock;
105                         }
106                         /*
107                          * page_head wasn't a dangling pointer but it
108                          * may not be a head page anymore by the time
109                          * we obtain the lock. That is ok as long as it
110                          * can't be freed from under us.
111                          */
112                         flags = compound_lock_irqsave(page_head);
113                         if (unlikely(!PageTail(page))) {
114                                 /* __split_huge_page_refcount run before us */
115                                 compound_unlock_irqrestore(page_head, flags);
116 skip_lock:
117                                 if (put_page_testzero(page_head))
118                                         __put_single_page(page_head);
119 out_put_single:
120                                 if (put_page_testzero(page))
121                                         __put_single_page(page);
122                                 return;
123                         }
124                         VM_BUG_ON(page_head != page->first_page);
125                         /*
126                          * We can release the refcount taken by
127                          * get_page_unless_zero() now that
128                          * __split_huge_page_refcount() is blocked on
129                          * the compound_lock.
130                          */
131                         if (put_page_testzero(page_head))
132                                 VM_BUG_ON(1);
133                         /* __split_huge_page_refcount will wait now */
134                         VM_BUG_ON(page_mapcount(page) <= 0);
135                         atomic_dec(&page->_mapcount);
136                         VM_BUG_ON(atomic_read(&page_head->_count) <= 0);
137                         VM_BUG_ON(atomic_read(&page->_count) != 0);
138                         compound_unlock_irqrestore(page_head, flags);
139
140 skip_lock_tail:
141                         if (put_page_testzero(page_head)) {
142                                 if (PageHead(page_head))
143                                         __put_compound_page(page_head);
144                                 else
145                                         __put_single_page(page_head);
146                         }
147                 } else {
148                         /* page_head is a dangling pointer */
149                         VM_BUG_ON(PageTail(page));
150                         goto out_put_single;
151                 }
152         } else if (put_page_testzero(page)) {
153                 if (PageHead(page))
154                         __put_compound_page(page);
155                 else
156                         __put_single_page(page);
157         }
158 }
159
160 void put_page(struct page *page)
161 {
162         if (unlikely(PageCompound(page)))
163                 put_compound_page(page);
164         else if (put_page_testzero(page))
165                 __put_single_page(page);
166 }
167 EXPORT_SYMBOL(put_page);
168
169 /*
170  * This function is exported but must not be called by anything other
171  * than get_page(). It implements the slow path of get_page().
172  */
173 bool __get_page_tail(struct page *page)
174 {
175         /*
176          * This takes care of get_page() if run on a tail page
177          * returned by one of the get_user_pages/follow_page variants.
178          * get_user_pages/follow_page itself doesn't need the compound
179          * lock because it runs __get_page_tail_foll() under the
180          * proper PT lock that already serializes against
181          * split_huge_page().
182          */
183         unsigned long flags;
184         bool got = false;
185         struct page *page_head = compound_trans_head(page);
186
187         if (likely(page != page_head && get_page_unless_zero(page_head))) {
188
189                 /* Ref to put_compound_page() comment. */
190                 if (PageSlab(page_head)) {
191                         if (likely(PageTail(page))) {
192                                 __get_page_tail_foll(page, false);
193                                 return true;
194                         } else {
195                                 put_page(page_head);
196                                 return false;
197                         }
198                 }
199
200                 /*
201                  * page_head wasn't a dangling pointer but it
202                  * may not be a head page anymore by the time
203                  * we obtain the lock. That is ok as long as it
204                  * can't be freed from under us.
205                  */
206                 flags = compound_lock_irqsave(page_head);
207                 /* here __split_huge_page_refcount won't run anymore */
208                 if (likely(PageTail(page))) {
209                         __get_page_tail_foll(page, false);
210                         got = true;
211                 }
212                 compound_unlock_irqrestore(page_head, flags);
213                 if (unlikely(!got))
214                         put_page(page_head);
215         }
216         return got;
217 }
218 EXPORT_SYMBOL(__get_page_tail);
219
220 /**
221  * put_pages_list() - release a list of pages
222  * @pages: list of pages threaded on page->lru
223  *
224  * Release a list of pages which are strung together on page.lru.  Currently
225  * used by read_cache_pages() and related error recovery code.
226  */
227 void put_pages_list(struct list_head *pages)
228 {
229         while (!list_empty(pages)) {
230                 struct page *victim;
231
232                 victim = list_entry(pages->prev, struct page, lru);
233                 list_del(&victim->lru);
234                 page_cache_release(victim);
235         }
236 }
237 EXPORT_SYMBOL(put_pages_list);
238
239 /*
240  * get_kernel_pages() - pin kernel pages in memory
241  * @kiov:       An array of struct kvec structures
242  * @nr_segs:    number of segments to pin
243  * @write:      pinning for read/write, currently ignored
244  * @pages:      array that receives pointers to the pages pinned.
245  *              Should be at least nr_segs long.
246  *
247  * Returns number of pages pinned. This may be fewer than the number
248  * requested. If nr_pages is 0 or negative, returns 0. If no pages
249  * were pinned, returns -errno. Each page returned must be released
250  * with a put_page() call when it is finished with.
251  */
252 int get_kernel_pages(const struct kvec *kiov, int nr_segs, int write,
253                 struct page **pages)
254 {
255         int seg;
256
257         for (seg = 0; seg < nr_segs; seg++) {
258                 if (WARN_ON(kiov[seg].iov_len != PAGE_SIZE))
259                         return seg;
260
261                 pages[seg] = kmap_to_page(kiov[seg].iov_base);
262                 page_cache_get(pages[seg]);
263         }
264
265         return seg;
266 }
267 EXPORT_SYMBOL_GPL(get_kernel_pages);
268
269 /*
270  * get_kernel_page() - pin a kernel page in memory
271  * @start:      starting kernel address
272  * @write:      pinning for read/write, currently ignored
273  * @pages:      array that receives pointer to the page pinned.
274  *              Must be at least nr_segs long.
275  *
276  * Returns 1 if page is pinned. If the page was not pinned, returns
277  * -errno. The page returned must be released with a put_page() call
278  * when it is finished with.
279  */
280 int get_kernel_page(unsigned long start, int write, struct page **pages)
281 {
282         const struct kvec kiov = {
283                 .iov_base = (void *)start,
284                 .iov_len = PAGE_SIZE
285         };
286
287         return get_kernel_pages(&kiov, 1, write, pages);
288 }
289 EXPORT_SYMBOL_GPL(get_kernel_page);
290
291 static void pagevec_lru_move_fn(struct pagevec *pvec,
292         void (*move_fn)(struct page *page, struct lruvec *lruvec, void *arg),
293         void *arg)
294 {
295         int i;
296         struct zone *zone = NULL;
297         struct lruvec *lruvec;
298         unsigned long flags = 0;
299
300         for (i = 0; i < pagevec_count(pvec); i++) {
301                 struct page *page = pvec->pages[i];
302                 struct zone *pagezone = page_zone(page);
303
304                 if (pagezone != zone) {
305                         if (zone)
306                                 spin_unlock_irqrestore(&zone->lru_lock, flags);
307                         zone = pagezone;
308                         spin_lock_irqsave(&zone->lru_lock, flags);
309                 }
310
311                 lruvec = mem_cgroup_page_lruvec(page, zone);
312                 (*move_fn)(page, lruvec, arg);
313         }
314         if (zone)
315                 spin_unlock_irqrestore(&zone->lru_lock, flags);
316         release_pages(pvec->pages, pvec->nr, pvec->cold);
317         pagevec_reinit(pvec);
318 }
319
320 static void pagevec_move_tail_fn(struct page *page, struct lruvec *lruvec,
321                                  void *arg)
322 {
323         int *pgmoved = arg;
324
325         if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
326                 enum lru_list lru = page_lru_base_type(page);
327                 list_move_tail(&page->lru, &lruvec->lists[lru]);
328                 (*pgmoved)++;
329         }
330 }
331
332 /*
333  * pagevec_move_tail() must be called with IRQ disabled.
334  * Otherwise this may cause nasty races.
335  */
336 static void pagevec_move_tail(struct pagevec *pvec)
337 {
338         int pgmoved = 0;
339
340         pagevec_lru_move_fn(pvec, pagevec_move_tail_fn, &pgmoved);
341         __count_vm_events(PGROTATED, pgmoved);
342 }
343
344 /*
345  * Writeback is about to end against a page which has been marked for immediate
346  * reclaim.  If it still appears to be reclaimable, move it to the tail of the
347  * inactive list.
348  */
349 void rotate_reclaimable_page(struct page *page)
350 {
351         if (!PageLocked(page) && !PageDirty(page) && !PageActive(page) &&
352             !PageUnevictable(page) && PageLRU(page)) {
353                 struct pagevec *pvec;
354                 unsigned long flags;
355
356                 page_cache_get(page);
357                 local_irq_save(flags);
358                 pvec = &__get_cpu_var(lru_rotate_pvecs);
359                 if (!pagevec_add(pvec, page))
360                         pagevec_move_tail(pvec);
361                 local_irq_restore(flags);
362         }
363 }
364
365 static void update_page_reclaim_stat(struct lruvec *lruvec,
366                                      int file, int rotated)
367 {
368         struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
369
370         reclaim_stat->recent_scanned[file]++;
371         if (rotated)
372                 reclaim_stat->recent_rotated[file]++;
373 }
374
375 static void __activate_page(struct page *page, struct lruvec *lruvec,
376                             void *arg)
377 {
378         if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
379                 int file = page_is_file_cache(page);
380                 int lru = page_lru_base_type(page);
381
382                 del_page_from_lru_list(page, lruvec, lru);
383                 SetPageActive(page);
384                 lru += LRU_ACTIVE;
385                 add_page_to_lru_list(page, lruvec, lru);
386
387                 __count_vm_event(PGACTIVATE);
388                 update_page_reclaim_stat(lruvec, file, 1);
389         }
390 }
391
392 #ifdef CONFIG_SMP
393 static DEFINE_PER_CPU(struct pagevec, activate_page_pvecs);
394
395 static void activate_page_drain(int cpu)
396 {
397         struct pagevec *pvec = &per_cpu(activate_page_pvecs, cpu);
398
399         if (pagevec_count(pvec))
400                 pagevec_lru_move_fn(pvec, __activate_page, NULL);
401 }
402
403 void activate_page(struct page *page)
404 {
405         if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
406                 struct pagevec *pvec = &get_cpu_var(activate_page_pvecs);
407
408                 page_cache_get(page);
409                 if (!pagevec_add(pvec, page))
410                         pagevec_lru_move_fn(pvec, __activate_page, NULL);
411                 put_cpu_var(activate_page_pvecs);
412         }
413 }
414
415 #else
416 static inline void activate_page_drain(int cpu)
417 {
418 }
419
420 void activate_page(struct page *page)
421 {
422         struct zone *zone = page_zone(page);
423
424         spin_lock_irq(&zone->lru_lock);
425         __activate_page(page, mem_cgroup_page_lruvec(page, zone), NULL);
426         spin_unlock_irq(&zone->lru_lock);
427 }
428 #endif
429
430 /*
431  * Mark a page as having seen activity.
432  *
433  * inactive,unreferenced        ->      inactive,referenced
434  * inactive,referenced          ->      active,unreferenced
435  * active,unreferenced          ->      active,referenced
436  */
437 void mark_page_accessed(struct page *page)
438 {
439         if (!PageActive(page) && !PageUnevictable(page) &&
440                         PageReferenced(page) && PageLRU(page)) {
441                 activate_page(page);
442                 ClearPageReferenced(page);
443         } else if (!PageReferenced(page)) {
444                 SetPageReferenced(page);
445         }
446 }
447 EXPORT_SYMBOL(mark_page_accessed);
448
449 /*
450  * Order of operations is important: flush the pagevec when it's already
451  * full, not when adding the last page, to make sure that last page is
452  * not added to the LRU directly when passed to this function. Because
453  * mark_page_accessed() (called after this when writing) only activates
454  * pages that are on the LRU, linear writes in subpage chunks would see
455  * every PAGEVEC_SIZE page activated, which is unexpected.
456  */
457 void __lru_cache_add(struct page *page, enum lru_list lru)
458 {
459         struct pagevec *pvec = &get_cpu_var(lru_add_pvecs)[lru];
460
461         page_cache_get(page);
462         if (!pagevec_space(pvec))
463                 __pagevec_lru_add(pvec, lru);
464         pagevec_add(pvec, page);
465         put_cpu_var(lru_add_pvecs);
466 }
467 EXPORT_SYMBOL(__lru_cache_add);
468
469 /**
470  * lru_cache_add_lru - add a page to a page list
471  * @page: the page to be added to the LRU.
472  * @lru: the LRU list to which the page is added.
473  */
474 void lru_cache_add_lru(struct page *page, enum lru_list lru)
475 {
476         if (PageActive(page)) {
477                 VM_BUG_ON(PageUnevictable(page));
478                 ClearPageActive(page);
479         } else if (PageUnevictable(page)) {
480                 VM_BUG_ON(PageActive(page));
481                 ClearPageUnevictable(page);
482         }
483
484         VM_BUG_ON(PageLRU(page) || PageActive(page) || PageUnevictable(page));
485         __lru_cache_add(page, lru);
486 }
487
488 /**
489  * add_page_to_unevictable_list - add a page to the unevictable list
490  * @page:  the page to be added to the unevictable list
491  *
492  * Add page directly to its zone's unevictable list.  To avoid races with
493  * tasks that might be making the page evictable, through eg. munlock,
494  * munmap or exit, while it's not on the lru, we want to add the page
495  * while it's locked or otherwise "invisible" to other tasks.  This is
496  * difficult to do when using the pagevec cache, so bypass that.
497  */
498 void add_page_to_unevictable_list(struct page *page)
499 {
500         struct zone *zone = page_zone(page);
501         struct lruvec *lruvec;
502
503         spin_lock_irq(&zone->lru_lock);
504         lruvec = mem_cgroup_page_lruvec(page, zone);
505         SetPageUnevictable(page);
506         SetPageLRU(page);
507         add_page_to_lru_list(page, lruvec, LRU_UNEVICTABLE);
508         spin_unlock_irq(&zone->lru_lock);
509 }
510
511 /*
512  * If the page can not be invalidated, it is moved to the
513  * inactive list to speed up its reclaim.  It is moved to the
514  * head of the list, rather than the tail, to give the flusher
515  * threads some time to write it out, as this is much more
516  * effective than the single-page writeout from reclaim.
517  *
518  * If the page isn't page_mapped and dirty/writeback, the page
519  * could reclaim asap using PG_reclaim.
520  *
521  * 1. active, mapped page -> none
522  * 2. active, dirty/writeback page -> inactive, head, PG_reclaim
523  * 3. inactive, mapped page -> none
524  * 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim
525  * 5. inactive, clean -> inactive, tail
526  * 6. Others -> none
527  *
528  * In 4, why it moves inactive's head, the VM expects the page would
529  * be write it out by flusher threads as this is much more effective
530  * than the single-page writeout from reclaim.
531  */
532 static void lru_deactivate_fn(struct page *page, struct lruvec *lruvec,
533                               void *arg)
534 {
535         int lru, file;
536         bool active;
537
538         if (!PageLRU(page))
539                 return;
540
541         if (PageUnevictable(page))
542                 return;
543
544         /* Some processes are using the page */
545         if (page_mapped(page))
546                 return;
547
548         active = PageActive(page);
549         file = page_is_file_cache(page);
550         lru = page_lru_base_type(page);
551
552         del_page_from_lru_list(page, lruvec, lru + active);
553         ClearPageActive(page);
554         ClearPageReferenced(page);
555         add_page_to_lru_list(page, lruvec, lru);
556
557         if (PageWriteback(page) || PageDirty(page)) {
558                 /*
559                  * PG_reclaim could be raced with end_page_writeback
560                  * It can make readahead confusing.  But race window
561                  * is _really_ small and  it's non-critical problem.
562                  */
563                 SetPageReclaim(page);
564         } else {
565                 /*
566                  * The page's writeback ends up during pagevec
567                  * We moves tha page into tail of inactive.
568                  */
569                 list_move_tail(&page->lru, &lruvec->lists[lru]);
570                 __count_vm_event(PGROTATED);
571         }
572
573         if (active)
574                 __count_vm_event(PGDEACTIVATE);
575         update_page_reclaim_stat(lruvec, file, 0);
576 }
577
578 /*
579  * Drain pages out of the cpu's pagevecs.
580  * Either "cpu" is the current CPU, and preemption has already been
581  * disabled; or "cpu" is being hot-unplugged, and is already dead.
582  */
583 void lru_add_drain_cpu(int cpu)
584 {
585         struct pagevec *pvecs = per_cpu(lru_add_pvecs, cpu);
586         struct pagevec *pvec;
587         int lru;
588
589         for_each_lru(lru) {
590                 pvec = &pvecs[lru - LRU_BASE];
591                 if (pagevec_count(pvec))
592                         __pagevec_lru_add(pvec, lru);
593         }
594
595         pvec = &per_cpu(lru_rotate_pvecs, cpu);
596         if (pagevec_count(pvec)) {
597                 unsigned long flags;
598
599                 /* No harm done if a racing interrupt already did this */
600                 local_irq_save(flags);
601                 pagevec_move_tail(pvec);
602                 local_irq_restore(flags);
603         }
604
605         pvec = &per_cpu(lru_deactivate_pvecs, cpu);
606         if (pagevec_count(pvec))
607                 pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
608
609         activate_page_drain(cpu);
610 }
611
612 /**
613  * deactivate_page - forcefully deactivate a page
614  * @page: page to deactivate
615  *
616  * This function hints the VM that @page is a good reclaim candidate,
617  * for example if its invalidation fails due to the page being dirty
618  * or under writeback.
619  */
620 void deactivate_page(struct page *page)
621 {
622         /*
623          * In a workload with many unevictable page such as mprotect, unevictable
624          * page deactivation for accelerating reclaim is pointless.
625          */
626         if (PageUnevictable(page))
627                 return;
628
629         if (likely(get_page_unless_zero(page))) {
630                 struct pagevec *pvec = &get_cpu_var(lru_deactivate_pvecs);
631
632                 if (!pagevec_add(pvec, page))
633                         pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
634                 put_cpu_var(lru_deactivate_pvecs);
635         }
636 }
637
638 void lru_add_drain(void)
639 {
640         lru_add_drain_cpu(get_cpu());
641         put_cpu();
642 }
643
644 static void lru_add_drain_per_cpu(struct work_struct *dummy)
645 {
646         lru_add_drain();
647 }
648
649 /*
650  * Returns 0 for success
651  */
652 int lru_add_drain_all(void)
653 {
654         return schedule_on_each_cpu(lru_add_drain_per_cpu);
655 }
656
657 /*
658  * Batched page_cache_release().  Decrement the reference count on all the
659  * passed pages.  If it fell to zero then remove the page from the LRU and
660  * free it.
661  *
662  * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
663  * for the remainder of the operation.
664  *
665  * The locking in this function is against shrink_inactive_list(): we recheck
666  * the page count inside the lock to see whether shrink_inactive_list()
667  * grabbed the page via the LRU.  If it did, give up: shrink_inactive_list()
668  * will free it.
669  */
670 void release_pages(struct page **pages, int nr, int cold)
671 {
672         int i;
673         LIST_HEAD(pages_to_free);
674         struct zone *zone = NULL;
675         struct lruvec *lruvec;
676         unsigned long uninitialized_var(flags);
677
678         for (i = 0; i < nr; i++) {
679                 struct page *page = pages[i];
680
681                 if (unlikely(PageCompound(page))) {
682                         if (zone) {
683                                 spin_unlock_irqrestore(&zone->lru_lock, flags);
684                                 zone = NULL;
685                         }
686                         put_compound_page(page);
687                         continue;
688                 }
689
690                 if (!put_page_testzero(page))
691                         continue;
692
693                 if (PageLRU(page)) {
694                         struct zone *pagezone = page_zone(page);
695
696                         if (pagezone != zone) {
697                                 if (zone)
698                                         spin_unlock_irqrestore(&zone->lru_lock,
699                                                                         flags);
700                                 zone = pagezone;
701                                 spin_lock_irqsave(&zone->lru_lock, flags);
702                         }
703
704                         lruvec = mem_cgroup_page_lruvec(page, zone);
705                         VM_BUG_ON(!PageLRU(page));
706                         __ClearPageLRU(page);
707                         del_page_from_lru_list(page, lruvec, page_off_lru(page));
708                 }
709
710                 list_add(&page->lru, &pages_to_free);
711         }
712         if (zone)
713                 spin_unlock_irqrestore(&zone->lru_lock, flags);
714
715         free_hot_cold_page_list(&pages_to_free, cold);
716 }
717 EXPORT_SYMBOL(release_pages);
718
719 /*
720  * The pages which we're about to release may be in the deferred lru-addition
721  * queues.  That would prevent them from really being freed right now.  That's
722  * OK from a correctness point of view but is inefficient - those pages may be
723  * cache-warm and we want to give them back to the page allocator ASAP.
724  *
725  * So __pagevec_release() will drain those queues here.  __pagevec_lru_add()
726  * and __pagevec_lru_add_active() call release_pages() directly to avoid
727  * mutual recursion.
728  */
729 void __pagevec_release(struct pagevec *pvec)
730 {
731         lru_add_drain();
732         release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
733         pagevec_reinit(pvec);
734 }
735 EXPORT_SYMBOL(__pagevec_release);
736
737 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
738 /* used by __split_huge_page_refcount() */
739 void lru_add_page_tail(struct page *page, struct page *page_tail,
740                        struct lruvec *lruvec)
741 {
742         int uninitialized_var(active);
743         enum lru_list lru;
744         const int file = 0;
745
746         VM_BUG_ON(!PageHead(page));
747         VM_BUG_ON(PageCompound(page_tail));
748         VM_BUG_ON(PageLRU(page_tail));
749         VM_BUG_ON(NR_CPUS != 1 &&
750                   !spin_is_locked(&lruvec_zone(lruvec)->lru_lock));
751
752         SetPageLRU(page_tail);
753
754         if (page_evictable(page_tail)) {
755                 if (PageActive(page)) {
756                         SetPageActive(page_tail);
757                         active = 1;
758                         lru = LRU_ACTIVE_ANON;
759                 } else {
760                         active = 0;
761                         lru = LRU_INACTIVE_ANON;
762                 }
763         } else {
764                 SetPageUnevictable(page_tail);
765                 lru = LRU_UNEVICTABLE;
766         }
767
768         if (likely(PageLRU(page)))
769                 list_add_tail(&page_tail->lru, &page->lru);
770         else {
771                 struct list_head *list_head;
772                 /*
773                  * Head page has not yet been counted, as an hpage,
774                  * so we must account for each subpage individually.
775                  *
776                  * Use the standard add function to put page_tail on the list,
777                  * but then correct its position so they all end up in order.
778                  */
779                 add_page_to_lru_list(page_tail, lruvec, lru);
780                 list_head = page_tail->lru.prev;
781                 list_move_tail(&page_tail->lru, list_head);
782         }
783
784         if (!PageUnevictable(page))
785                 update_page_reclaim_stat(lruvec, file, active);
786 }
787 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
788
789 static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec,
790                                  void *arg)
791 {
792         enum lru_list lru = (enum lru_list)arg;
793         int file = is_file_lru(lru);
794         int active = is_active_lru(lru);
795
796         VM_BUG_ON(PageActive(page));
797         VM_BUG_ON(PageUnevictable(page));
798         VM_BUG_ON(PageLRU(page));
799
800         SetPageLRU(page);
801         if (active)
802                 SetPageActive(page);
803         add_page_to_lru_list(page, lruvec, lru);
804         update_page_reclaim_stat(lruvec, file, active);
805 }
806
807 /*
808  * Add the passed pages to the LRU, then drop the caller's refcount
809  * on them.  Reinitialises the caller's pagevec.
810  */
811 void __pagevec_lru_add(struct pagevec *pvec, enum lru_list lru)
812 {
813         VM_BUG_ON(is_unevictable_lru(lru));
814
815         pagevec_lru_move_fn(pvec, __pagevec_lru_add_fn, (void *)lru);
816 }
817 EXPORT_SYMBOL(__pagevec_lru_add);
818
819 /**
820  * pagevec_lookup - gang pagecache lookup
821  * @pvec:       Where the resulting pages are placed
822  * @mapping:    The address_space to search
823  * @start:      The starting page index
824  * @nr_pages:   The maximum number of pages
825  *
826  * pagevec_lookup() will search for and return a group of up to @nr_pages pages
827  * in the mapping.  The pages are placed in @pvec.  pagevec_lookup() takes a
828  * reference against the pages in @pvec.
829  *
830  * The search returns a group of mapping-contiguous pages with ascending
831  * indexes.  There may be holes in the indices due to not-present pages.
832  *
833  * pagevec_lookup() returns the number of pages which were found.
834  */
835 unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
836                 pgoff_t start, unsigned nr_pages)
837 {
838         pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
839         return pagevec_count(pvec);
840 }
841 EXPORT_SYMBOL(pagevec_lookup);
842
843 unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping,
844                 pgoff_t *index, int tag, unsigned nr_pages)
845 {
846         pvec->nr = find_get_pages_tag(mapping, index, tag,
847                                         nr_pages, pvec->pages);
848         return pagevec_count(pvec);
849 }
850 EXPORT_SYMBOL(pagevec_lookup_tag);
851
852 /*
853  * Perform any setup for the swap system
854  */
855 void __init swap_setup(void)
856 {
857         unsigned long megs = totalram_pages >> (20 - PAGE_SHIFT);
858
859 #ifdef CONFIG_SWAP
860         bdi_init(swapper_space.backing_dev_info);
861 #endif
862
863         /* Use a smaller cluster for small-memory machines */
864         if (megs < 16)
865                 page_cluster = 2;
866         else
867                 page_cluster = 3;
868         /*
869          * Right now other parts of the system means that we
870          * _really_ don't want to cluster much more
871          */
872 }