mm, lockdep: annotate reclaim context to zone reclaim too
[linux-2.6.git] / mm / vmscan.c
1 /*
2  *  linux/mm/vmscan.c
3  *
4  *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
5  *
6  *  Swap reorganised 29.12.95, Stephen Tweedie.
7  *  kswapd added: 7.1.96  sct
8  *  Removed kswapd_ctl limits, and swap out as many pages as needed
9  *  to bring the system back to freepages.high: 2.4.97, Rik van Riel.
10  *  Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
11  *  Multiqueue VM started 5.8.00, Rik van Riel.
12  */
13
14 #include <linux/mm.h>
15 #include <linux/module.h>
16 #include <linux/slab.h>
17 #include <linux/kernel_stat.h>
18 #include <linux/swap.h>
19 #include <linux/pagemap.h>
20 #include <linux/init.h>
21 #include <linux/highmem.h>
22 #include <linux/vmstat.h>
23 #include <linux/file.h>
24 #include <linux/writeback.h>
25 #include <linux/blkdev.h>
26 #include <linux/buffer_head.h>  /* for try_to_release_page(),
27                                         buffer_heads_over_limit */
28 #include <linux/mm_inline.h>
29 #include <linux/pagevec.h>
30 #include <linux/backing-dev.h>
31 #include <linux/rmap.h>
32 #include <linux/topology.h>
33 #include <linux/cpu.h>
34 #include <linux/cpuset.h>
35 #include <linux/notifier.h>
36 #include <linux/rwsem.h>
37 #include <linux/delay.h>
38 #include <linux/kthread.h>
39 #include <linux/freezer.h>
40 #include <linux/memcontrol.h>
41 #include <linux/delayacct.h>
42 #include <linux/sysctl.h>
43
44 #include <asm/tlbflush.h>
45 #include <asm/div64.h>
46
47 #include <linux/swapops.h>
48
49 #include "internal.h"
50
51 struct scan_control {
52         /* Incremented by the number of inactive pages that were scanned */
53         unsigned long nr_scanned;
54
55         /* Number of pages freed so far during a call to shrink_zones() */
56         unsigned long nr_reclaimed;
57
58         /* How many pages shrink_list() should reclaim */
59         unsigned long nr_to_reclaim;
60
61         unsigned long hibernation_mode;
62
63         /* This context's GFP mask */
64         gfp_t gfp_mask;
65
66         int may_writepage;
67
68         /* Can mapped pages be reclaimed? */
69         int may_unmap;
70
71         /* Can pages be swapped as part of reclaim? */
72         int may_swap;
73
74         int swappiness;
75
76         int all_unreclaimable;
77
78         int order;
79
80         /* Which cgroup do we reclaim from */
81         struct mem_cgroup *mem_cgroup;
82
83         /*
84          * Nodemask of nodes allowed by the caller. If NULL, all nodes
85          * are scanned.
86          */
87         nodemask_t      *nodemask;
88
89         /* Pluggable isolate pages callback */
90         unsigned long (*isolate_pages)(unsigned long nr, struct list_head *dst,
91                         unsigned long *scanned, int order, int mode,
92                         struct zone *z, struct mem_cgroup *mem_cont,
93                         int active, int file);
94 };
95
96 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
97
98 #ifdef ARCH_HAS_PREFETCH
99 #define prefetch_prev_lru_page(_page, _base, _field)                    \
100         do {                                                            \
101                 if ((_page)->lru.prev != _base) {                       \
102                         struct page *prev;                              \
103                                                                         \
104                         prev = lru_to_page(&(_page->lru));              \
105                         prefetch(&prev->_field);                        \
106                 }                                                       \
107         } while (0)
108 #else
109 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
110 #endif
111
112 #ifdef ARCH_HAS_PREFETCHW
113 #define prefetchw_prev_lru_page(_page, _base, _field)                   \
114         do {                                                            \
115                 if ((_page)->lru.prev != _base) {                       \
116                         struct page *prev;                              \
117                                                                         \
118                         prev = lru_to_page(&(_page->lru));              \
119                         prefetchw(&prev->_field);                       \
120                 }                                                       \
121         } while (0)
122 #else
123 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
124 #endif
125
126 /*
127  * From 0 .. 100.  Higher means more swappy.
128  */
129 int vm_swappiness = 60;
130 long vm_total_pages;    /* The total number of pages which the VM controls */
131
132 static LIST_HEAD(shrinker_list);
133 static DECLARE_RWSEM(shrinker_rwsem);
134
135 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
136 #define scanning_global_lru(sc) (!(sc)->mem_cgroup)
137 #else
138 #define scanning_global_lru(sc) (1)
139 #endif
140
141 static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone,
142                                                   struct scan_control *sc)
143 {
144         if (!scanning_global_lru(sc))
145                 return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone);
146
147         return &zone->reclaim_stat;
148 }
149
150 static unsigned long zone_nr_lru_pages(struct zone *zone,
151                                 struct scan_control *sc, enum lru_list lru)
152 {
153         if (!scanning_global_lru(sc))
154                 return mem_cgroup_zone_nr_pages(sc->mem_cgroup, zone, lru);
155
156         return zone_page_state(zone, NR_LRU_BASE + lru);
157 }
158
159
160 /*
161  * Add a shrinker callback to be called from the vm
162  */
163 void register_shrinker(struct shrinker *shrinker)
164 {
165         shrinker->nr = 0;
166         down_write(&shrinker_rwsem);
167         list_add_tail(&shrinker->list, &shrinker_list);
168         up_write(&shrinker_rwsem);
169 }
170 EXPORT_SYMBOL(register_shrinker);
171
172 /*
173  * Remove one
174  */
175 void unregister_shrinker(struct shrinker *shrinker)
176 {
177         down_write(&shrinker_rwsem);
178         list_del(&shrinker->list);
179         up_write(&shrinker_rwsem);
180 }
181 EXPORT_SYMBOL(unregister_shrinker);
182
183 #define SHRINK_BATCH 128
184 /*
185  * Call the shrink functions to age shrinkable caches
186  *
187  * Here we assume it costs one seek to replace a lru page and that it also
188  * takes a seek to recreate a cache object.  With this in mind we age equal
189  * percentages of the lru and ageable caches.  This should balance the seeks
190  * generated by these structures.
191  *
192  * If the vm encountered mapped pages on the LRU it increase the pressure on
193  * slab to avoid swapping.
194  *
195  * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
196  *
197  * `lru_pages' represents the number of on-LRU pages in all the zones which
198  * are eligible for the caller's allocation attempt.  It is used for balancing
199  * slab reclaim versus page reclaim.
200  *
201  * Returns the number of slab objects which we shrunk.
202  */
203 unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
204                         unsigned long lru_pages)
205 {
206         struct shrinker *shrinker;
207         unsigned long ret = 0;
208
209         if (scanned == 0)
210                 scanned = SWAP_CLUSTER_MAX;
211
212         if (!down_read_trylock(&shrinker_rwsem))
213                 return 1;       /* Assume we'll be able to shrink next time */
214
215         list_for_each_entry(shrinker, &shrinker_list, list) {
216                 unsigned long long delta;
217                 unsigned long total_scan;
218                 unsigned long max_pass = (*shrinker->shrink)(0, gfp_mask);
219
220                 delta = (4 * scanned) / shrinker->seeks;
221                 delta *= max_pass;
222                 do_div(delta, lru_pages + 1);
223                 shrinker->nr += delta;
224                 if (shrinker->nr < 0) {
225                         printk(KERN_ERR "shrink_slab: %pF negative objects to "
226                                "delete nr=%ld\n",
227                                shrinker->shrink, shrinker->nr);
228                         shrinker->nr = max_pass;
229                 }
230
231                 /*
232                  * Avoid risking looping forever due to too large nr value:
233                  * never try to free more than twice the estimate number of
234                  * freeable entries.
235                  */
236                 if (shrinker->nr > max_pass * 2)
237                         shrinker->nr = max_pass * 2;
238
239                 total_scan = shrinker->nr;
240                 shrinker->nr = 0;
241
242                 while (total_scan >= SHRINK_BATCH) {
243                         long this_scan = SHRINK_BATCH;
244                         int shrink_ret;
245                         int nr_before;
246
247                         nr_before = (*shrinker->shrink)(0, gfp_mask);
248                         shrink_ret = (*shrinker->shrink)(this_scan, gfp_mask);
249                         if (shrink_ret == -1)
250                                 break;
251                         if (shrink_ret < nr_before)
252                                 ret += nr_before - shrink_ret;
253                         count_vm_events(SLABS_SCANNED, this_scan);
254                         total_scan -= this_scan;
255
256                         cond_resched();
257                 }
258
259                 shrinker->nr += total_scan;
260         }
261         up_read(&shrinker_rwsem);
262         return ret;
263 }
264
265 /* Called without lock on whether page is mapped, so answer is unstable */
266 static inline int page_mapping_inuse(struct page *page)
267 {
268         struct address_space *mapping;
269
270         /* Page is in somebody's page tables. */
271         if (page_mapped(page))
272                 return 1;
273
274         /* Be more reluctant to reclaim swapcache than pagecache */
275         if (PageSwapCache(page))
276                 return 1;
277
278         mapping = page_mapping(page);
279         if (!mapping)
280                 return 0;
281
282         /* File is mmap'd by somebody? */
283         return mapping_mapped(mapping);
284 }
285
286 static inline int is_page_cache_freeable(struct page *page)
287 {
288         /*
289          * A freeable page cache page is referenced only by the caller
290          * that isolated the page, the page cache radix tree and
291          * optional buffer heads at page->private.
292          */
293         return page_count(page) - page_has_private(page) == 2;
294 }
295
296 static int may_write_to_queue(struct backing_dev_info *bdi)
297 {
298         if (current->flags & PF_SWAPWRITE)
299                 return 1;
300         if (!bdi_write_congested(bdi))
301                 return 1;
302         if (bdi == current->backing_dev_info)
303                 return 1;
304         return 0;
305 }
306
307 /*
308  * We detected a synchronous write error writing a page out.  Probably
309  * -ENOSPC.  We need to propagate that into the address_space for a subsequent
310  * fsync(), msync() or close().
311  *
312  * The tricky part is that after writepage we cannot touch the mapping: nothing
313  * prevents it from being freed up.  But we have a ref on the page and once
314  * that page is locked, the mapping is pinned.
315  *
316  * We're allowed to run sleeping lock_page() here because we know the caller has
317  * __GFP_FS.
318  */
319 static void handle_write_error(struct address_space *mapping,
320                                 struct page *page, int error)
321 {
322         lock_page(page);
323         if (page_mapping(page) == mapping)
324                 mapping_set_error(mapping, error);
325         unlock_page(page);
326 }
327
328 /* Request for sync pageout. */
329 enum pageout_io {
330         PAGEOUT_IO_ASYNC,
331         PAGEOUT_IO_SYNC,
332 };
333
334 /* possible outcome of pageout() */
335 typedef enum {
336         /* failed to write page out, page is locked */
337         PAGE_KEEP,
338         /* move page to the active list, page is locked */
339         PAGE_ACTIVATE,
340         /* page has been sent to the disk successfully, page is unlocked */
341         PAGE_SUCCESS,
342         /* page is clean and locked */
343         PAGE_CLEAN,
344 } pageout_t;
345
346 /*
347  * pageout is called by shrink_page_list() for each dirty page.
348  * Calls ->writepage().
349  */
350 static pageout_t pageout(struct page *page, struct address_space *mapping,
351                                                 enum pageout_io sync_writeback)
352 {
353         /*
354          * If the page is dirty, only perform writeback if that write
355          * will be non-blocking.  To prevent this allocation from being
356          * stalled by pagecache activity.  But note that there may be
357          * stalls if we need to run get_block().  We could test
358          * PagePrivate for that.
359          *
360          * If this process is currently in __generic_file_aio_write() against
361          * this page's queue, we can perform writeback even if that
362          * will block.
363          *
364          * If the page is swapcache, write it back even if that would
365          * block, for some throttling. This happens by accident, because
366          * swap_backing_dev_info is bust: it doesn't reflect the
367          * congestion state of the swapdevs.  Easy to fix, if needed.
368          */
369         if (!is_page_cache_freeable(page))
370                 return PAGE_KEEP;
371         if (!mapping) {
372                 /*
373                  * Some data journaling orphaned pages can have
374                  * page->mapping == NULL while being dirty with clean buffers.
375                  */
376                 if (page_has_private(page)) {
377                         if (try_to_free_buffers(page)) {
378                                 ClearPageDirty(page);
379                                 printk("%s: orphaned page\n", __func__);
380                                 return PAGE_CLEAN;
381                         }
382                 }
383                 return PAGE_KEEP;
384         }
385         if (mapping->a_ops->writepage == NULL)
386                 return PAGE_ACTIVATE;
387         if (!may_write_to_queue(mapping->backing_dev_info))
388                 return PAGE_KEEP;
389
390         if (clear_page_dirty_for_io(page)) {
391                 int res;
392                 struct writeback_control wbc = {
393                         .sync_mode = WB_SYNC_NONE,
394                         .nr_to_write = SWAP_CLUSTER_MAX,
395                         .range_start = 0,
396                         .range_end = LLONG_MAX,
397                         .nonblocking = 1,
398                         .for_reclaim = 1,
399                 };
400
401                 SetPageReclaim(page);
402                 res = mapping->a_ops->writepage(page, &wbc);
403                 if (res < 0)
404                         handle_write_error(mapping, page, res);
405                 if (res == AOP_WRITEPAGE_ACTIVATE) {
406                         ClearPageReclaim(page);
407                         return PAGE_ACTIVATE;
408                 }
409
410                 /*
411                  * Wait on writeback if requested to. This happens when
412                  * direct reclaiming a large contiguous area and the
413                  * first attempt to free a range of pages fails.
414                  */
415                 if (PageWriteback(page) && sync_writeback == PAGEOUT_IO_SYNC)
416                         wait_on_page_writeback(page);
417
418                 if (!PageWriteback(page)) {
419                         /* synchronous write or broken a_ops? */
420                         ClearPageReclaim(page);
421                 }
422                 inc_zone_page_state(page, NR_VMSCAN_WRITE);
423                 return PAGE_SUCCESS;
424         }
425
426         return PAGE_CLEAN;
427 }
428
429 /*
430  * Same as remove_mapping, but if the page is removed from the mapping, it
431  * gets returned with a refcount of 0.
432  */
433 static int __remove_mapping(struct address_space *mapping, struct page *page)
434 {
435         BUG_ON(!PageLocked(page));
436         BUG_ON(mapping != page_mapping(page));
437
438         spin_lock_irq(&mapping->tree_lock);
439         /*
440          * The non racy check for a busy page.
441          *
442          * Must be careful with the order of the tests. When someone has
443          * a ref to the page, it may be possible that they dirty it then
444          * drop the reference. So if PageDirty is tested before page_count
445          * here, then the following race may occur:
446          *
447          * get_user_pages(&page);
448          * [user mapping goes away]
449          * write_to(page);
450          *                              !PageDirty(page)    [good]
451          * SetPageDirty(page);
452          * put_page(page);
453          *                              !page_count(page)   [good, discard it]
454          *
455          * [oops, our write_to data is lost]
456          *
457          * Reversing the order of the tests ensures such a situation cannot
458          * escape unnoticed. The smp_rmb is needed to ensure the page->flags
459          * load is not satisfied before that of page->_count.
460          *
461          * Note that if SetPageDirty is always performed via set_page_dirty,
462          * and thus under tree_lock, then this ordering is not required.
463          */
464         if (!page_freeze_refs(page, 2))
465                 goto cannot_free;
466         /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
467         if (unlikely(PageDirty(page))) {
468                 page_unfreeze_refs(page, 2);
469                 goto cannot_free;
470         }
471
472         if (PageSwapCache(page)) {
473                 swp_entry_t swap = { .val = page_private(page) };
474                 __delete_from_swap_cache(page);
475                 spin_unlock_irq(&mapping->tree_lock);
476                 swapcache_free(swap, page);
477         } else {
478                 __remove_from_page_cache(page);
479                 spin_unlock_irq(&mapping->tree_lock);
480                 mem_cgroup_uncharge_cache_page(page);
481         }
482
483         return 1;
484
485 cannot_free:
486         spin_unlock_irq(&mapping->tree_lock);
487         return 0;
488 }
489
490 /*
491  * Attempt to detach a locked page from its ->mapping.  If it is dirty or if
492  * someone else has a ref on the page, abort and return 0.  If it was
493  * successfully detached, return 1.  Assumes the caller has a single ref on
494  * this page.
495  */
496 int remove_mapping(struct address_space *mapping, struct page *page)
497 {
498         if (__remove_mapping(mapping, page)) {
499                 /*
500                  * Unfreezing the refcount with 1 rather than 2 effectively
501                  * drops the pagecache ref for us without requiring another
502                  * atomic operation.
503                  */
504                 page_unfreeze_refs(page, 1);
505                 return 1;
506         }
507         return 0;
508 }
509
510 /**
511  * putback_lru_page - put previously isolated page onto appropriate LRU list
512  * @page: page to be put back to appropriate lru list
513  *
514  * Add previously isolated @page to appropriate LRU list.
515  * Page may still be unevictable for other reasons.
516  *
517  * lru_lock must not be held, interrupts must be enabled.
518  */
519 void putback_lru_page(struct page *page)
520 {
521         int lru;
522         int active = !!TestClearPageActive(page);
523         int was_unevictable = PageUnevictable(page);
524
525         VM_BUG_ON(PageLRU(page));
526
527 redo:
528         ClearPageUnevictable(page);
529
530         if (page_evictable(page, NULL)) {
531                 /*
532                  * For evictable pages, we can use the cache.
533                  * In event of a race, worst case is we end up with an
534                  * unevictable page on [in]active list.
535                  * We know how to handle that.
536                  */
537                 lru = active + page_lru_base_type(page);
538                 lru_cache_add_lru(page, lru);
539         } else {
540                 /*
541                  * Put unevictable pages directly on zone's unevictable
542                  * list.
543                  */
544                 lru = LRU_UNEVICTABLE;
545                 add_page_to_unevictable_list(page);
546                 /*
547                  * When racing with an mlock clearing (page is
548                  * unlocked), make sure that if the other thread does
549                  * not observe our setting of PG_lru and fails
550                  * isolation, we see PG_mlocked cleared below and move
551                  * the page back to the evictable list.
552                  *
553                  * The other side is TestClearPageMlocked().
554                  */
555                 smp_mb();
556         }
557
558         /*
559          * page's status can change while we move it among lru. If an evictable
560          * page is on unevictable list, it never be freed. To avoid that,
561          * check after we added it to the list, again.
562          */
563         if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
564                 if (!isolate_lru_page(page)) {
565                         put_page(page);
566                         goto redo;
567                 }
568                 /* This means someone else dropped this page from LRU
569                  * So, it will be freed or putback to LRU again. There is
570                  * nothing to do here.
571                  */
572         }
573
574         if (was_unevictable && lru != LRU_UNEVICTABLE)
575                 count_vm_event(UNEVICTABLE_PGRESCUED);
576         else if (!was_unevictable && lru == LRU_UNEVICTABLE)
577                 count_vm_event(UNEVICTABLE_PGCULLED);
578
579         put_page(page);         /* drop ref from isolate */
580 }
581
582 /*
583  * shrink_page_list() returns the number of reclaimed pages
584  */
585 static unsigned long shrink_page_list(struct list_head *page_list,
586                                         struct scan_control *sc,
587                                         enum pageout_io sync_writeback)
588 {
589         LIST_HEAD(ret_pages);
590         struct pagevec freed_pvec;
591         int pgactivate = 0;
592         unsigned long nr_reclaimed = 0;
593         unsigned long vm_flags;
594
595         cond_resched();
596
597         pagevec_init(&freed_pvec, 1);
598         while (!list_empty(page_list)) {
599                 struct address_space *mapping;
600                 struct page *page;
601                 int may_enter_fs;
602                 int referenced;
603
604                 cond_resched();
605
606                 page = lru_to_page(page_list);
607                 list_del(&page->lru);
608
609                 if (!trylock_page(page))
610                         goto keep;
611
612                 VM_BUG_ON(PageActive(page));
613
614                 sc->nr_scanned++;
615
616                 if (unlikely(!page_evictable(page, NULL)))
617                         goto cull_mlocked;
618
619                 if (!sc->may_unmap && page_mapped(page))
620                         goto keep_locked;
621
622                 /* Double the slab pressure for mapped and swapcache pages */
623                 if (page_mapped(page) || PageSwapCache(page))
624                         sc->nr_scanned++;
625
626                 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
627                         (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
628
629                 if (PageWriteback(page)) {
630                         /*
631                          * Synchronous reclaim is performed in two passes,
632                          * first an asynchronous pass over the list to
633                          * start parallel writeback, and a second synchronous
634                          * pass to wait for the IO to complete.  Wait here
635                          * for any page for which writeback has already
636                          * started.
637                          */
638                         if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs)
639                                 wait_on_page_writeback(page);
640                         else
641                                 goto keep_locked;
642                 }
643
644                 referenced = page_referenced(page, 1,
645                                                 sc->mem_cgroup, &vm_flags);
646                 /*
647                  * In active use or really unfreeable?  Activate it.
648                  * If page which have PG_mlocked lost isoltation race,
649                  * try_to_unmap moves it to unevictable list
650                  */
651                 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER &&
652                                         referenced && page_mapping_inuse(page)
653                                         && !(vm_flags & VM_LOCKED))
654                         goto activate_locked;
655
656                 /*
657                  * Anonymous process memory has backing store?
658                  * Try to allocate it some swap space here.
659                  */
660                 if (PageAnon(page) && !PageSwapCache(page)) {
661                         if (!(sc->gfp_mask & __GFP_IO))
662                                 goto keep_locked;
663                         if (!add_to_swap(page))
664                                 goto activate_locked;
665                         may_enter_fs = 1;
666                 }
667
668                 mapping = page_mapping(page);
669
670                 /*
671                  * The page is mapped into the page tables of one or more
672                  * processes. Try to unmap it here.
673                  */
674                 if (page_mapped(page) && mapping) {
675                         switch (try_to_unmap(page, TTU_UNMAP)) {
676                         case SWAP_FAIL:
677                                 goto activate_locked;
678                         case SWAP_AGAIN:
679                                 goto keep_locked;
680                         case SWAP_MLOCK:
681                                 goto cull_mlocked;
682                         case SWAP_SUCCESS:
683                                 ; /* try to free the page below */
684                         }
685                 }
686
687                 if (PageDirty(page)) {
688                         if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced)
689                                 goto keep_locked;
690                         if (!may_enter_fs)
691                                 goto keep_locked;
692                         if (!sc->may_writepage)
693                                 goto keep_locked;
694
695                         /* Page is dirty, try to write it out here */
696                         switch (pageout(page, mapping, sync_writeback)) {
697                         case PAGE_KEEP:
698                                 goto keep_locked;
699                         case PAGE_ACTIVATE:
700                                 goto activate_locked;
701                         case PAGE_SUCCESS:
702                                 if (PageWriteback(page) || PageDirty(page))
703                                         goto keep;
704                                 /*
705                                  * A synchronous write - probably a ramdisk.  Go
706                                  * ahead and try to reclaim the page.
707                                  */
708                                 if (!trylock_page(page))
709                                         goto keep;
710                                 if (PageDirty(page) || PageWriteback(page))
711                                         goto keep_locked;
712                                 mapping = page_mapping(page);
713                         case PAGE_CLEAN:
714                                 ; /* try to free the page below */
715                         }
716                 }
717
718                 /*
719                  * If the page has buffers, try to free the buffer mappings
720                  * associated with this page. If we succeed we try to free
721                  * the page as well.
722                  *
723                  * We do this even if the page is PageDirty().
724                  * try_to_release_page() does not perform I/O, but it is
725                  * possible for a page to have PageDirty set, but it is actually
726                  * clean (all its buffers are clean).  This happens if the
727                  * buffers were written out directly, with submit_bh(). ext3
728                  * will do this, as well as the blockdev mapping.
729                  * try_to_release_page() will discover that cleanness and will
730                  * drop the buffers and mark the page clean - it can be freed.
731                  *
732                  * Rarely, pages can have buffers and no ->mapping.  These are
733                  * the pages which were not successfully invalidated in
734                  * truncate_complete_page().  We try to drop those buffers here
735                  * and if that worked, and the page is no longer mapped into
736                  * process address space (page_count == 1) it can be freed.
737                  * Otherwise, leave the page on the LRU so it is swappable.
738                  */
739                 if (page_has_private(page)) {
740                         if (!try_to_release_page(page, sc->gfp_mask))
741                                 goto activate_locked;
742                         if (!mapping && page_count(page) == 1) {
743                                 unlock_page(page);
744                                 if (put_page_testzero(page))
745                                         goto free_it;
746                                 else {
747                                         /*
748                                          * rare race with speculative reference.
749                                          * the speculative reference will free
750                                          * this page shortly, so we may
751                                          * increment nr_reclaimed here (and
752                                          * leave it off the LRU).
753                                          */
754                                         nr_reclaimed++;
755                                         continue;
756                                 }
757                         }
758                 }
759
760                 if (!mapping || !__remove_mapping(mapping, page))
761                         goto keep_locked;
762
763                 /*
764                  * At this point, we have no other references and there is
765                  * no way to pick any more up (removed from LRU, removed
766                  * from pagecache). Can use non-atomic bitops now (and
767                  * we obviously don't have to worry about waking up a process
768                  * waiting on the page lock, because there are no references.
769                  */
770                 __clear_page_locked(page);
771 free_it:
772                 nr_reclaimed++;
773                 if (!pagevec_add(&freed_pvec, page)) {
774                         __pagevec_free(&freed_pvec);
775                         pagevec_reinit(&freed_pvec);
776                 }
777                 continue;
778
779 cull_mlocked:
780                 if (PageSwapCache(page))
781                         try_to_free_swap(page);
782                 unlock_page(page);
783                 putback_lru_page(page);
784                 continue;
785
786 activate_locked:
787                 /* Not a candidate for swapping, so reclaim swap space. */
788                 if (PageSwapCache(page) && vm_swap_full())
789                         try_to_free_swap(page);
790                 VM_BUG_ON(PageActive(page));
791                 SetPageActive(page);
792                 pgactivate++;
793 keep_locked:
794                 unlock_page(page);
795 keep:
796                 list_add(&page->lru, &ret_pages);
797                 VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
798         }
799         list_splice(&ret_pages, page_list);
800         if (pagevec_count(&freed_pvec))
801                 __pagevec_free(&freed_pvec);
802         count_vm_events(PGACTIVATE, pgactivate);
803         return nr_reclaimed;
804 }
805
806 /* LRU Isolation modes. */
807 #define ISOLATE_INACTIVE 0      /* Isolate inactive pages. */
808 #define ISOLATE_ACTIVE 1        /* Isolate active pages. */
809 #define ISOLATE_BOTH 2          /* Isolate both active and inactive pages. */
810
811 /*
812  * Attempt to remove the specified page from its LRU.  Only take this page
813  * if it is of the appropriate PageActive status.  Pages which are being
814  * freed elsewhere are also ignored.
815  *
816  * page:        page to consider
817  * mode:        one of the LRU isolation modes defined above
818  *
819  * returns 0 on success, -ve errno on failure.
820  */
821 int __isolate_lru_page(struct page *page, int mode, int file)
822 {
823         int ret = -EINVAL;
824
825         /* Only take pages on the LRU. */
826         if (!PageLRU(page))
827                 return ret;
828
829         /*
830          * When checking the active state, we need to be sure we are
831          * dealing with comparible boolean values.  Take the logical not
832          * of each.
833          */
834         if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode))
835                 return ret;
836
837         if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file)
838                 return ret;
839
840         /*
841          * When this function is being called for lumpy reclaim, we
842          * initially look into all LRU pages, active, inactive and
843          * unevictable; only give shrink_page_list evictable pages.
844          */
845         if (PageUnevictable(page))
846                 return ret;
847
848         ret = -EBUSY;
849
850         if (likely(get_page_unless_zero(page))) {
851                 /*
852                  * Be careful not to clear PageLRU until after we're
853                  * sure the page is not being freed elsewhere -- the
854                  * page release code relies on it.
855                  */
856                 ClearPageLRU(page);
857                 ret = 0;
858         }
859
860         return ret;
861 }
862
863 /*
864  * zone->lru_lock is heavily contended.  Some of the functions that
865  * shrink the lists perform better by taking out a batch of pages
866  * and working on them outside the LRU lock.
867  *
868  * For pagecache intensive workloads, this function is the hottest
869  * spot in the kernel (apart from copy_*_user functions).
870  *
871  * Appropriate locks must be held before calling this function.
872  *
873  * @nr_to_scan: The number of pages to look through on the list.
874  * @src:        The LRU list to pull pages off.
875  * @dst:        The temp list to put pages on to.
876  * @scanned:    The number of pages that were scanned.
877  * @order:      The caller's attempted allocation order
878  * @mode:       One of the LRU isolation modes
879  * @file:       True [1] if isolating file [!anon] pages
880  *
881  * returns how many pages were moved onto *@dst.
882  */
883 static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
884                 struct list_head *src, struct list_head *dst,
885                 unsigned long *scanned, int order, int mode, int file)
886 {
887         unsigned long nr_taken = 0;
888         unsigned long scan;
889
890         for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
891                 struct page *page;
892                 unsigned long pfn;
893                 unsigned long end_pfn;
894                 unsigned long page_pfn;
895                 int zone_id;
896
897                 page = lru_to_page(src);
898                 prefetchw_prev_lru_page(page, src, flags);
899
900                 VM_BUG_ON(!PageLRU(page));
901
902                 switch (__isolate_lru_page(page, mode, file)) {
903                 case 0:
904                         list_move(&page->lru, dst);
905                         mem_cgroup_del_lru(page);
906                         nr_taken++;
907                         break;
908
909                 case -EBUSY:
910                         /* else it is being freed elsewhere */
911                         list_move(&page->lru, src);
912                         mem_cgroup_rotate_lru_list(page, page_lru(page));
913                         continue;
914
915                 default:
916                         BUG();
917                 }
918
919                 if (!order)
920                         continue;
921
922                 /*
923                  * Attempt to take all pages in the order aligned region
924                  * surrounding the tag page.  Only take those pages of
925                  * the same active state as that tag page.  We may safely
926                  * round the target page pfn down to the requested order
927                  * as the mem_map is guarenteed valid out to MAX_ORDER,
928                  * where that page is in a different zone we will detect
929                  * it from its zone id and abort this block scan.
930                  */
931                 zone_id = page_zone_id(page);
932                 page_pfn = page_to_pfn(page);
933                 pfn = page_pfn & ~((1 << order) - 1);
934                 end_pfn = pfn + (1 << order);
935                 for (; pfn < end_pfn; pfn++) {
936                         struct page *cursor_page;
937
938                         /* The target page is in the block, ignore it. */
939                         if (unlikely(pfn == page_pfn))
940                                 continue;
941
942                         /* Avoid holes within the zone. */
943                         if (unlikely(!pfn_valid_within(pfn)))
944                                 break;
945
946                         cursor_page = pfn_to_page(pfn);
947
948                         /* Check that we have not crossed a zone boundary. */
949                         if (unlikely(page_zone_id(cursor_page) != zone_id))
950                                 continue;
951
952                         /*
953                          * If we don't have enough swap space, reclaiming of
954                          * anon page which don't already have a swap slot is
955                          * pointless.
956                          */
957                         if (nr_swap_pages <= 0 && PageAnon(cursor_page) &&
958                                         !PageSwapCache(cursor_page))
959                                 continue;
960
961                         if (__isolate_lru_page(cursor_page, mode, file) == 0) {
962                                 list_move(&cursor_page->lru, dst);
963                                 mem_cgroup_del_lru(cursor_page);
964                                 nr_taken++;
965                                 scan++;
966                         }
967                 }
968         }
969
970         *scanned = scan;
971         return nr_taken;
972 }
973
974 static unsigned long isolate_pages_global(unsigned long nr,
975                                         struct list_head *dst,
976                                         unsigned long *scanned, int order,
977                                         int mode, struct zone *z,
978                                         struct mem_cgroup *mem_cont,
979                                         int active, int file)
980 {
981         int lru = LRU_BASE;
982         if (active)
983                 lru += LRU_ACTIVE;
984         if (file)
985                 lru += LRU_FILE;
986         return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
987                                                                 mode, file);
988 }
989
990 /*
991  * clear_active_flags() is a helper for shrink_active_list(), clearing
992  * any active bits from the pages in the list.
993  */
994 static unsigned long clear_active_flags(struct list_head *page_list,
995                                         unsigned int *count)
996 {
997         int nr_active = 0;
998         int lru;
999         struct page *page;
1000
1001         list_for_each_entry(page, page_list, lru) {
1002                 lru = page_lru_base_type(page);
1003                 if (PageActive(page)) {
1004                         lru += LRU_ACTIVE;
1005                         ClearPageActive(page);
1006                         nr_active++;
1007                 }
1008                 count[lru]++;
1009         }
1010
1011         return nr_active;
1012 }
1013
1014 /**
1015  * isolate_lru_page - tries to isolate a page from its LRU list
1016  * @page: page to isolate from its LRU list
1017  *
1018  * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1019  * vmstat statistic corresponding to whatever LRU list the page was on.
1020  *
1021  * Returns 0 if the page was removed from an LRU list.
1022  * Returns -EBUSY if the page was not on an LRU list.
1023  *
1024  * The returned page will have PageLRU() cleared.  If it was found on
1025  * the active list, it will have PageActive set.  If it was found on
1026  * the unevictable list, it will have the PageUnevictable bit set. That flag
1027  * may need to be cleared by the caller before letting the page go.
1028  *
1029  * The vmstat statistic corresponding to the list on which the page was
1030  * found will be decremented.
1031  *
1032  * Restrictions:
1033  * (1) Must be called with an elevated refcount on the page. This is a
1034  *     fundamentnal difference from isolate_lru_pages (which is called
1035  *     without a stable reference).
1036  * (2) the lru_lock must not be held.
1037  * (3) interrupts must be enabled.
1038  */
1039 int isolate_lru_page(struct page *page)
1040 {
1041         int ret = -EBUSY;
1042
1043         if (PageLRU(page)) {
1044                 struct zone *zone = page_zone(page);
1045
1046                 spin_lock_irq(&zone->lru_lock);
1047                 if (PageLRU(page) && get_page_unless_zero(page)) {
1048                         int lru = page_lru(page);
1049                         ret = 0;
1050                         ClearPageLRU(page);
1051
1052                         del_page_from_lru_list(zone, page, lru);
1053                 }
1054                 spin_unlock_irq(&zone->lru_lock);
1055         }
1056         return ret;
1057 }
1058
1059 /*
1060  * Are there way too many processes in the direct reclaim path already?
1061  */
1062 static int too_many_isolated(struct zone *zone, int file,
1063                 struct scan_control *sc)
1064 {
1065         unsigned long inactive, isolated;
1066
1067         if (current_is_kswapd())
1068                 return 0;
1069
1070         if (!scanning_global_lru(sc))
1071                 return 0;
1072
1073         if (file) {
1074                 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1075                 isolated = zone_page_state(zone, NR_ISOLATED_FILE);
1076         } else {
1077                 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1078                 isolated = zone_page_state(zone, NR_ISOLATED_ANON);
1079         }
1080
1081         return isolated > inactive;
1082 }
1083
1084 /*
1085  * shrink_inactive_list() is a helper for shrink_zone().  It returns the number
1086  * of reclaimed pages
1087  */
1088 static unsigned long shrink_inactive_list(unsigned long max_scan,
1089                         struct zone *zone, struct scan_control *sc,
1090                         int priority, int file)
1091 {
1092         LIST_HEAD(page_list);
1093         struct pagevec pvec;
1094         unsigned long nr_scanned = 0;
1095         unsigned long nr_reclaimed = 0;
1096         struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1097         int lumpy_reclaim = 0;
1098
1099         while (unlikely(too_many_isolated(zone, file, sc))) {
1100                 congestion_wait(BLK_RW_ASYNC, HZ/10);
1101
1102                 /* We are about to die and free our memory. Return now. */
1103                 if (fatal_signal_pending(current))
1104                         return SWAP_CLUSTER_MAX;
1105         }
1106
1107         /*
1108          * If we need a large contiguous chunk of memory, or have
1109          * trouble getting a small set of contiguous pages, we
1110          * will reclaim both active and inactive pages.
1111          *
1112          * We use the same threshold as pageout congestion_wait below.
1113          */
1114         if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
1115                 lumpy_reclaim = 1;
1116         else if (sc->order && priority < DEF_PRIORITY - 2)
1117                 lumpy_reclaim = 1;
1118
1119         pagevec_init(&pvec, 1);
1120
1121         lru_add_drain();
1122         spin_lock_irq(&zone->lru_lock);
1123         do {
1124                 struct page *page;
1125                 unsigned long nr_taken;
1126                 unsigned long nr_scan;
1127                 unsigned long nr_freed;
1128                 unsigned long nr_active;
1129                 unsigned int count[NR_LRU_LISTS] = { 0, };
1130                 int mode = lumpy_reclaim ? ISOLATE_BOTH : ISOLATE_INACTIVE;
1131                 unsigned long nr_anon;
1132                 unsigned long nr_file;
1133
1134                 nr_taken = sc->isolate_pages(SWAP_CLUSTER_MAX,
1135                              &page_list, &nr_scan, sc->order, mode,
1136                                 zone, sc->mem_cgroup, 0, file);
1137
1138                 if (scanning_global_lru(sc)) {
1139                         zone->pages_scanned += nr_scan;
1140                         if (current_is_kswapd())
1141                                 __count_zone_vm_events(PGSCAN_KSWAPD, zone,
1142                                                        nr_scan);
1143                         else
1144                                 __count_zone_vm_events(PGSCAN_DIRECT, zone,
1145                                                        nr_scan);
1146                 }
1147
1148                 if (nr_taken == 0)
1149                         goto done;
1150
1151                 nr_active = clear_active_flags(&page_list, count);
1152                 __count_vm_events(PGDEACTIVATE, nr_active);
1153
1154                 __mod_zone_page_state(zone, NR_ACTIVE_FILE,
1155                                                 -count[LRU_ACTIVE_FILE]);
1156                 __mod_zone_page_state(zone, NR_INACTIVE_FILE,
1157                                                 -count[LRU_INACTIVE_FILE]);
1158                 __mod_zone_page_state(zone, NR_ACTIVE_ANON,
1159                                                 -count[LRU_ACTIVE_ANON]);
1160                 __mod_zone_page_state(zone, NR_INACTIVE_ANON,
1161                                                 -count[LRU_INACTIVE_ANON]);
1162
1163                 nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
1164                 nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
1165                 __mod_zone_page_state(zone, NR_ISOLATED_ANON, nr_anon);
1166                 __mod_zone_page_state(zone, NR_ISOLATED_FILE, nr_file);
1167
1168                 reclaim_stat->recent_scanned[0] += nr_anon;
1169                 reclaim_stat->recent_scanned[1] += nr_file;
1170
1171                 spin_unlock_irq(&zone->lru_lock);
1172
1173                 nr_scanned += nr_scan;
1174                 nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC);
1175
1176                 /*
1177                  * If we are direct reclaiming for contiguous pages and we do
1178                  * not reclaim everything in the list, try again and wait
1179                  * for IO to complete. This will stall high-order allocations
1180                  * but that should be acceptable to the caller
1181                  */
1182                 if (nr_freed < nr_taken && !current_is_kswapd() &&
1183                     lumpy_reclaim) {
1184                         congestion_wait(BLK_RW_ASYNC, HZ/10);
1185
1186                         /*
1187                          * The attempt at page out may have made some
1188                          * of the pages active, mark them inactive again.
1189                          */
1190                         nr_active = clear_active_flags(&page_list, count);
1191                         count_vm_events(PGDEACTIVATE, nr_active);
1192
1193                         nr_freed += shrink_page_list(&page_list, sc,
1194                                                         PAGEOUT_IO_SYNC);
1195                 }
1196
1197                 nr_reclaimed += nr_freed;
1198
1199                 local_irq_disable();
1200                 if (current_is_kswapd())
1201                         __count_vm_events(KSWAPD_STEAL, nr_freed);
1202                 __count_zone_vm_events(PGSTEAL, zone, nr_freed);
1203
1204                 spin_lock(&zone->lru_lock);
1205                 /*
1206                  * Put back any unfreeable pages.
1207                  */
1208                 while (!list_empty(&page_list)) {
1209                         int lru;
1210                         page = lru_to_page(&page_list);
1211                         VM_BUG_ON(PageLRU(page));
1212                         list_del(&page->lru);
1213                         if (unlikely(!page_evictable(page, NULL))) {
1214                                 spin_unlock_irq(&zone->lru_lock);
1215                                 putback_lru_page(page);
1216                                 spin_lock_irq(&zone->lru_lock);
1217                                 continue;
1218                         }
1219                         SetPageLRU(page);
1220                         lru = page_lru(page);
1221                         add_page_to_lru_list(zone, page, lru);
1222                         if (is_active_lru(lru)) {
1223                                 int file = is_file_lru(lru);
1224                                 reclaim_stat->recent_rotated[file]++;
1225                         }
1226                         if (!pagevec_add(&pvec, page)) {
1227                                 spin_unlock_irq(&zone->lru_lock);
1228                                 __pagevec_release(&pvec);
1229                                 spin_lock_irq(&zone->lru_lock);
1230                         }
1231                 }
1232                 __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
1233                 __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
1234
1235         } while (nr_scanned < max_scan);
1236
1237 done:
1238         spin_unlock_irq(&zone->lru_lock);
1239         pagevec_release(&pvec);
1240         return nr_reclaimed;
1241 }
1242
1243 /*
1244  * We are about to scan this zone at a certain priority level.  If that priority
1245  * level is smaller (ie: more urgent) than the previous priority, then note
1246  * that priority level within the zone.  This is done so that when the next
1247  * process comes in to scan this zone, it will immediately start out at this
1248  * priority level rather than having to build up its own scanning priority.
1249  * Here, this priority affects only the reclaim-mapped threshold.
1250  */
1251 static inline void note_zone_scanning_priority(struct zone *zone, int priority)
1252 {
1253         if (priority < zone->prev_priority)
1254                 zone->prev_priority = priority;
1255 }
1256
1257 /*
1258  * This moves pages from the active list to the inactive list.
1259  *
1260  * We move them the other way if the page is referenced by one or more
1261  * processes, from rmap.
1262  *
1263  * If the pages are mostly unmapped, the processing is fast and it is
1264  * appropriate to hold zone->lru_lock across the whole operation.  But if
1265  * the pages are mapped, the processing is slow (page_referenced()) so we
1266  * should drop zone->lru_lock around each page.  It's impossible to balance
1267  * this, so instead we remove the pages from the LRU while processing them.
1268  * It is safe to rely on PG_active against the non-LRU pages in here because
1269  * nobody will play with that bit on a non-LRU page.
1270  *
1271  * The downside is that we have to touch page->_count against each page.
1272  * But we had to alter page->flags anyway.
1273  */
1274
1275 static void move_active_pages_to_lru(struct zone *zone,
1276                                      struct list_head *list,
1277                                      enum lru_list lru)
1278 {
1279         unsigned long pgmoved = 0;
1280         struct pagevec pvec;
1281         struct page *page;
1282
1283         pagevec_init(&pvec, 1);
1284
1285         while (!list_empty(list)) {
1286                 page = lru_to_page(list);
1287
1288                 VM_BUG_ON(PageLRU(page));
1289                 SetPageLRU(page);
1290
1291                 list_move(&page->lru, &zone->lru[lru].list);
1292                 mem_cgroup_add_lru_list(page, lru);
1293                 pgmoved++;
1294
1295                 if (!pagevec_add(&pvec, page) || list_empty(list)) {
1296                         spin_unlock_irq(&zone->lru_lock);
1297                         if (buffer_heads_over_limit)
1298                                 pagevec_strip(&pvec);
1299                         __pagevec_release(&pvec);
1300                         spin_lock_irq(&zone->lru_lock);
1301                 }
1302         }
1303         __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1304         if (!is_active_lru(lru))
1305                 __count_vm_events(PGDEACTIVATE, pgmoved);
1306 }
1307
1308 static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1309                         struct scan_control *sc, int priority, int file)
1310 {
1311         unsigned long nr_taken;
1312         unsigned long pgscanned;
1313         unsigned long vm_flags;
1314         LIST_HEAD(l_hold);      /* The pages which were snipped off */
1315         LIST_HEAD(l_active);
1316         LIST_HEAD(l_inactive);
1317         struct page *page;
1318         struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1319         unsigned long nr_rotated = 0;
1320
1321         lru_add_drain();
1322         spin_lock_irq(&zone->lru_lock);
1323         nr_taken = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order,
1324                                         ISOLATE_ACTIVE, zone,
1325                                         sc->mem_cgroup, 1, file);
1326         /*
1327          * zone->pages_scanned is used for detect zone's oom
1328          * mem_cgroup remembers nr_scan by itself.
1329          */
1330         if (scanning_global_lru(sc)) {
1331                 zone->pages_scanned += pgscanned;
1332         }
1333         reclaim_stat->recent_scanned[file] += nr_taken;
1334
1335         __count_zone_vm_events(PGREFILL, zone, pgscanned);
1336         if (file)
1337                 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken);
1338         else
1339                 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken);
1340         __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
1341         spin_unlock_irq(&zone->lru_lock);
1342
1343         while (!list_empty(&l_hold)) {
1344                 cond_resched();
1345                 page = lru_to_page(&l_hold);
1346                 list_del(&page->lru);
1347
1348                 if (unlikely(!page_evictable(page, NULL))) {
1349                         putback_lru_page(page);
1350                         continue;
1351                 }
1352
1353                 /* page_referenced clears PageReferenced */
1354                 if (page_mapping_inuse(page) &&
1355                     page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) {
1356                         nr_rotated++;
1357                         /*
1358                          * Identify referenced, file-backed active pages and
1359                          * give them one more trip around the active list. So
1360                          * that executable code get better chances to stay in
1361                          * memory under moderate memory pressure.  Anon pages
1362                          * are not likely to be evicted by use-once streaming
1363                          * IO, plus JVM can create lots of anon VM_EXEC pages,
1364                          * so we ignore them here.
1365                          */
1366                         if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
1367                                 list_add(&page->lru, &l_active);
1368                                 continue;
1369                         }
1370                 }
1371
1372                 ClearPageActive(page);  /* we are de-activating */
1373                 list_add(&page->lru, &l_inactive);
1374         }
1375
1376         /*
1377          * Move pages back to the lru list.
1378          */
1379         spin_lock_irq(&zone->lru_lock);
1380         /*
1381          * Count referenced pages from currently used mappings as rotated,
1382          * even though only some of them are actually re-activated.  This
1383          * helps balance scan pressure between file and anonymous pages in
1384          * get_scan_ratio.
1385          */
1386         reclaim_stat->recent_rotated[file] += nr_rotated;
1387
1388         move_active_pages_to_lru(zone, &l_active,
1389                                                 LRU_ACTIVE + file * LRU_FILE);
1390         move_active_pages_to_lru(zone, &l_inactive,
1391                                                 LRU_BASE   + file * LRU_FILE);
1392         __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1393         spin_unlock_irq(&zone->lru_lock);
1394 }
1395
1396 static int inactive_anon_is_low_global(struct zone *zone)
1397 {
1398         unsigned long active, inactive;
1399
1400         active = zone_page_state(zone, NR_ACTIVE_ANON);
1401         inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1402
1403         if (inactive * zone->inactive_ratio < active)
1404                 return 1;
1405
1406         return 0;
1407 }
1408
1409 /**
1410  * inactive_anon_is_low - check if anonymous pages need to be deactivated
1411  * @zone: zone to check
1412  * @sc:   scan control of this context
1413  *
1414  * Returns true if the zone does not have enough inactive anon pages,
1415  * meaning some active anon pages need to be deactivated.
1416  */
1417 static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc)
1418 {
1419         int low;
1420
1421         if (scanning_global_lru(sc))
1422                 low = inactive_anon_is_low_global(zone);
1423         else
1424                 low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup);
1425         return low;
1426 }
1427
1428 static int inactive_file_is_low_global(struct zone *zone)
1429 {
1430         unsigned long active, inactive;
1431
1432         active = zone_page_state(zone, NR_ACTIVE_FILE);
1433         inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1434
1435         return (active > inactive);
1436 }
1437
1438 /**
1439  * inactive_file_is_low - check if file pages need to be deactivated
1440  * @zone: zone to check
1441  * @sc:   scan control of this context
1442  *
1443  * When the system is doing streaming IO, memory pressure here
1444  * ensures that active file pages get deactivated, until more
1445  * than half of the file pages are on the inactive list.
1446  *
1447  * Once we get to that situation, protect the system's working
1448  * set from being evicted by disabling active file page aging.
1449  *
1450  * This uses a different ratio than the anonymous pages, because
1451  * the page cache uses a use-once replacement algorithm.
1452  */
1453 static int inactive_file_is_low(struct zone *zone, struct scan_control *sc)
1454 {
1455         int low;
1456
1457         if (scanning_global_lru(sc))
1458                 low = inactive_file_is_low_global(zone);
1459         else
1460                 low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup);
1461         return low;
1462 }
1463
1464 static int inactive_list_is_low(struct zone *zone, struct scan_control *sc,
1465                                 int file)
1466 {
1467         if (file)
1468                 return inactive_file_is_low(zone, sc);
1469         else
1470                 return inactive_anon_is_low(zone, sc);
1471 }
1472
1473 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1474         struct zone *zone, struct scan_control *sc, int priority)
1475 {
1476         int file = is_file_lru(lru);
1477
1478         if (is_active_lru(lru)) {
1479                 if (inactive_list_is_low(zone, sc, file))
1480                     shrink_active_list(nr_to_scan, zone, sc, priority, file);
1481                 return 0;
1482         }
1483
1484         return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1485 }
1486
1487 /*
1488  * Determine how aggressively the anon and file LRU lists should be
1489  * scanned.  The relative value of each set of LRU lists is determined
1490  * by looking at the fraction of the pages scanned we did rotate back
1491  * onto the active list instead of evict.
1492  *
1493  * percent[0] specifies how much pressure to put on ram/swap backed
1494  * memory, while percent[1] determines pressure on the file LRUs.
1495  */
1496 static void get_scan_ratio(struct zone *zone, struct scan_control *sc,
1497                                         unsigned long *percent)
1498 {
1499         unsigned long anon, file, free;
1500         unsigned long anon_prio, file_prio;
1501         unsigned long ap, fp;
1502         struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1503
1504         /* If we have no swap space, do not bother scanning anon pages. */
1505         if (!sc->may_swap || (nr_swap_pages <= 0)) {
1506                 percent[0] = 0;
1507                 percent[1] = 100;
1508                 return;
1509         }
1510
1511         anon  = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) +
1512                 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON);
1513         file  = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) +
1514                 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
1515
1516         if (scanning_global_lru(sc)) {
1517                 free  = zone_page_state(zone, NR_FREE_PAGES);
1518                 /* If we have very few page cache pages,
1519                    force-scan anon pages. */
1520                 if (unlikely(file + free <= high_wmark_pages(zone))) {
1521                         percent[0] = 100;
1522                         percent[1] = 0;
1523                         return;
1524                 }
1525         }
1526
1527         /*
1528          * OK, so we have swap space and a fair amount of page cache
1529          * pages.  We use the recently rotated / recently scanned
1530          * ratios to determine how valuable each cache is.
1531          *
1532          * Because workloads change over time (and to avoid overflow)
1533          * we keep these statistics as a floating average, which ends
1534          * up weighing recent references more than old ones.
1535          *
1536          * anon in [0], file in [1]
1537          */
1538         if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
1539                 spin_lock_irq(&zone->lru_lock);
1540                 reclaim_stat->recent_scanned[0] /= 2;
1541                 reclaim_stat->recent_rotated[0] /= 2;
1542                 spin_unlock_irq(&zone->lru_lock);
1543         }
1544
1545         if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
1546                 spin_lock_irq(&zone->lru_lock);
1547                 reclaim_stat->recent_scanned[1] /= 2;
1548                 reclaim_stat->recent_rotated[1] /= 2;
1549                 spin_unlock_irq(&zone->lru_lock);
1550         }
1551
1552         /*
1553          * With swappiness at 100, anonymous and file have the same priority.
1554          * This scanning priority is essentially the inverse of IO cost.
1555          */
1556         anon_prio = sc->swappiness;
1557         file_prio = 200 - sc->swappiness;
1558
1559         /*
1560          * The amount of pressure on anon vs file pages is inversely
1561          * proportional to the fraction of recently scanned pages on
1562          * each list that were recently referenced and in active use.
1563          */
1564         ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
1565         ap /= reclaim_stat->recent_rotated[0] + 1;
1566
1567         fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
1568         fp /= reclaim_stat->recent_rotated[1] + 1;
1569
1570         /* Normalize to percentages */
1571         percent[0] = 100 * ap / (ap + fp + 1);
1572         percent[1] = 100 - percent[0];
1573 }
1574
1575 /*
1576  * Smallish @nr_to_scan's are deposited in @nr_saved_scan,
1577  * until we collected @swap_cluster_max pages to scan.
1578  */
1579 static unsigned long nr_scan_try_batch(unsigned long nr_to_scan,
1580                                        unsigned long *nr_saved_scan)
1581 {
1582         unsigned long nr;
1583
1584         *nr_saved_scan += nr_to_scan;
1585         nr = *nr_saved_scan;
1586
1587         if (nr >= SWAP_CLUSTER_MAX)
1588                 *nr_saved_scan = 0;
1589         else
1590                 nr = 0;
1591
1592         return nr;
1593 }
1594
1595 /*
1596  * This is a basic per-zone page freer.  Used by both kswapd and direct reclaim.
1597  */
1598 static void shrink_zone(int priority, struct zone *zone,
1599                                 struct scan_control *sc)
1600 {
1601         unsigned long nr[NR_LRU_LISTS];
1602         unsigned long nr_to_scan;
1603         unsigned long percent[2];       /* anon @ 0; file @ 1 */
1604         enum lru_list l;
1605         unsigned long nr_reclaimed = sc->nr_reclaimed;
1606         unsigned long nr_to_reclaim = sc->nr_to_reclaim;
1607         struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1608
1609         get_scan_ratio(zone, sc, percent);
1610
1611         for_each_evictable_lru(l) {
1612                 int file = is_file_lru(l);
1613                 unsigned long scan;
1614
1615                 if (percent[file] == 0) {
1616                         nr[l] = 0;
1617                         continue;
1618                 }
1619
1620                 scan = zone_nr_lru_pages(zone, sc, l);
1621                 if (priority) {
1622                         scan >>= priority;
1623                         scan = (scan * percent[file]) / 100;
1624                 }
1625                 nr[l] = nr_scan_try_batch(scan,
1626                                           &reclaim_stat->nr_saved_scan[l]);
1627         }
1628
1629         while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
1630                                         nr[LRU_INACTIVE_FILE]) {
1631                 for_each_evictable_lru(l) {
1632                         if (nr[l]) {
1633                                 nr_to_scan = min_t(unsigned long,
1634                                                    nr[l], SWAP_CLUSTER_MAX);
1635                                 nr[l] -= nr_to_scan;
1636
1637                                 nr_reclaimed += shrink_list(l, nr_to_scan,
1638                                                             zone, sc, priority);
1639                         }
1640                 }
1641                 /*
1642                  * On large memory systems, scan >> priority can become
1643                  * really large. This is fine for the starting priority;
1644                  * we want to put equal scanning pressure on each zone.
1645                  * However, if the VM has a harder time of freeing pages,
1646                  * with multiple processes reclaiming pages, the total
1647                  * freeing target can get unreasonably large.
1648                  */
1649                 if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY)
1650                         break;
1651         }
1652
1653         sc->nr_reclaimed = nr_reclaimed;
1654
1655         /*
1656          * Even if we did not try to evict anon pages at all, we want to
1657          * rebalance the anon lru active/inactive ratio.
1658          */
1659         if (inactive_anon_is_low(zone, sc) && nr_swap_pages > 0)
1660                 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
1661
1662         throttle_vm_writeout(sc->gfp_mask);
1663 }
1664
1665 /*
1666  * This is the direct reclaim path, for page-allocating processes.  We only
1667  * try to reclaim pages from zones which will satisfy the caller's allocation
1668  * request.
1669  *
1670  * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
1671  * Because:
1672  * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1673  *    allocation or
1674  * b) The target zone may be at high_wmark_pages(zone) but the lower zones
1675  *    must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
1676  *    zone defense algorithm.
1677  *
1678  * If a zone is deemed to be full of pinned pages then just give it a light
1679  * scan then give up on it.
1680  */
1681 static void shrink_zones(int priority, struct zonelist *zonelist,
1682                                         struct scan_control *sc)
1683 {
1684         enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1685         struct zoneref *z;
1686         struct zone *zone;
1687
1688         sc->all_unreclaimable = 1;
1689         for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx,
1690                                         sc->nodemask) {
1691                 if (!populated_zone(zone))
1692                         continue;
1693                 /*
1694                  * Take care memory controller reclaiming has small influence
1695                  * to global LRU.
1696                  */
1697                 if (scanning_global_lru(sc)) {
1698                         if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1699                                 continue;
1700                         note_zone_scanning_priority(zone, priority);
1701
1702                         if (zone_is_all_unreclaimable(zone) &&
1703                                                 priority != DEF_PRIORITY)
1704                                 continue;       /* Let kswapd poll it */
1705                         sc->all_unreclaimable = 0;
1706                 } else {
1707                         /*
1708                          * Ignore cpuset limitation here. We just want to reduce
1709                          * # of used pages by us regardless of memory shortage.
1710                          */
1711                         sc->all_unreclaimable = 0;
1712                         mem_cgroup_note_reclaim_priority(sc->mem_cgroup,
1713                                                         priority);
1714                 }
1715
1716                 shrink_zone(priority, zone, sc);
1717         }
1718 }
1719
1720 /*
1721  * This is the main entry point to direct page reclaim.
1722  *
1723  * If a full scan of the inactive list fails to free enough memory then we
1724  * are "out of memory" and something needs to be killed.
1725  *
1726  * If the caller is !__GFP_FS then the probability of a failure is reasonably
1727  * high - the zone may be full of dirty or under-writeback pages, which this
1728  * caller can't do much about.  We kick the writeback threads and take explicit
1729  * naps in the hope that some of these pages can be written.  But if the
1730  * allocating task holds filesystem locks which prevent writeout this might not
1731  * work, and the allocation attempt will fail.
1732  *
1733  * returns:     0, if no pages reclaimed
1734  *              else, the number of pages reclaimed
1735  */
1736 static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
1737                                         struct scan_control *sc)
1738 {
1739         int priority;
1740         unsigned long ret = 0;
1741         unsigned long total_scanned = 0;
1742         struct reclaim_state *reclaim_state = current->reclaim_state;
1743         unsigned long lru_pages = 0;
1744         struct zoneref *z;
1745         struct zone *zone;
1746         enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1747         unsigned long writeback_threshold;
1748
1749         delayacct_freepages_start();
1750
1751         if (scanning_global_lru(sc))
1752                 count_vm_event(ALLOCSTALL);
1753         /*
1754          * mem_cgroup will not do shrink_slab.
1755          */
1756         if (scanning_global_lru(sc)) {
1757                 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1758
1759                         if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1760                                 continue;
1761
1762                         lru_pages += zone_reclaimable_pages(zone);
1763                 }
1764         }
1765
1766         for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1767                 sc->nr_scanned = 0;
1768                 if (!priority)
1769                         disable_swap_token();
1770                 shrink_zones(priority, zonelist, sc);
1771                 /*
1772                  * Don't shrink slabs when reclaiming memory from
1773                  * over limit cgroups
1774                  */
1775                 if (scanning_global_lru(sc)) {
1776                         shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages);
1777                         if (reclaim_state) {
1778                                 sc->nr_reclaimed += reclaim_state->reclaimed_slab;
1779                                 reclaim_state->reclaimed_slab = 0;
1780                         }
1781                 }
1782                 total_scanned += sc->nr_scanned;
1783                 if (sc->nr_reclaimed >= sc->nr_to_reclaim) {
1784                         ret = sc->nr_reclaimed;
1785                         goto out;
1786                 }
1787
1788                 /*
1789                  * Try to write back as many pages as we just scanned.  This
1790                  * tends to cause slow streaming writers to write data to the
1791                  * disk smoothly, at the dirtying rate, which is nice.   But
1792                  * that's undesirable in laptop mode, where we *want* lumpy
1793                  * writeout.  So in laptop mode, write out the whole world.
1794                  */
1795                 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
1796                 if (total_scanned > writeback_threshold) {
1797                         wakeup_flusher_threads(laptop_mode ? 0 : total_scanned);
1798                         sc->may_writepage = 1;
1799                 }
1800
1801                 /* Take a nap, wait for some writeback to complete */
1802                 if (!sc->hibernation_mode && sc->nr_scanned &&
1803                     priority < DEF_PRIORITY - 2)
1804                         congestion_wait(BLK_RW_ASYNC, HZ/10);
1805         }
1806         /* top priority shrink_zones still had more to do? don't OOM, then */
1807         if (!sc->all_unreclaimable && scanning_global_lru(sc))
1808                 ret = sc->nr_reclaimed;
1809 out:
1810         /*
1811          * Now that we've scanned all the zones at this priority level, note
1812          * that level within the zone so that the next thread which performs
1813          * scanning of this zone will immediately start out at this priority
1814          * level.  This affects only the decision whether or not to bring
1815          * mapped pages onto the inactive list.
1816          */
1817         if (priority < 0)
1818                 priority = 0;
1819
1820         if (scanning_global_lru(sc)) {
1821                 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1822
1823                         if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1824                                 continue;
1825
1826                         zone->prev_priority = priority;
1827                 }
1828         } else
1829                 mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority);
1830
1831         delayacct_freepages_end();
1832
1833         return ret;
1834 }
1835
1836 unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
1837                                 gfp_t gfp_mask, nodemask_t *nodemask)
1838 {
1839         struct scan_control sc = {
1840                 .gfp_mask = gfp_mask,
1841                 .may_writepage = !laptop_mode,
1842                 .nr_to_reclaim = SWAP_CLUSTER_MAX,
1843                 .may_unmap = 1,
1844                 .may_swap = 1,
1845                 .swappiness = vm_swappiness,
1846                 .order = order,
1847                 .mem_cgroup = NULL,
1848                 .isolate_pages = isolate_pages_global,
1849                 .nodemask = nodemask,
1850         };
1851
1852         return do_try_to_free_pages(zonelist, &sc);
1853 }
1854
1855 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1856
1857 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
1858                                                 gfp_t gfp_mask, bool noswap,
1859                                                 unsigned int swappiness,
1860                                                 struct zone *zone, int nid)
1861 {
1862         struct scan_control sc = {
1863                 .may_writepage = !laptop_mode,
1864                 .may_unmap = 1,
1865                 .may_swap = !noswap,
1866                 .swappiness = swappiness,
1867                 .order = 0,
1868                 .mem_cgroup = mem,
1869                 .isolate_pages = mem_cgroup_isolate_pages,
1870         };
1871         nodemask_t nm  = nodemask_of_node(nid);
1872
1873         sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
1874                         (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
1875         sc.nodemask = &nm;
1876         sc.nr_reclaimed = 0;
1877         sc.nr_scanned = 0;
1878         /*
1879          * NOTE: Although we can get the priority field, using it
1880          * here is not a good idea, since it limits the pages we can scan.
1881          * if we don't reclaim here, the shrink_zone from balance_pgdat
1882          * will pick up pages from other mem cgroup's as well. We hack
1883          * the priority and make it zero.
1884          */
1885         shrink_zone(0, zone, &sc);
1886         return sc.nr_reclaimed;
1887 }
1888
1889 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
1890                                            gfp_t gfp_mask,
1891                                            bool noswap,
1892                                            unsigned int swappiness)
1893 {
1894         struct zonelist *zonelist;
1895         struct scan_control sc = {
1896                 .may_writepage = !laptop_mode,
1897                 .may_unmap = 1,
1898                 .may_swap = !noswap,
1899                 .nr_to_reclaim = SWAP_CLUSTER_MAX,
1900                 .swappiness = swappiness,
1901                 .order = 0,
1902                 .mem_cgroup = mem_cont,
1903                 .isolate_pages = mem_cgroup_isolate_pages,
1904                 .nodemask = NULL, /* we don't care the placement */
1905         };
1906
1907         sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
1908                         (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
1909         zonelist = NODE_DATA(numa_node_id())->node_zonelists;
1910         return do_try_to_free_pages(zonelist, &sc);
1911 }
1912 #endif
1913
1914 /* is kswapd sleeping prematurely? */
1915 static int sleeping_prematurely(pg_data_t *pgdat, int order, long remaining)
1916 {
1917         int i;
1918
1919         /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
1920         if (remaining)
1921                 return 1;
1922
1923         /* If after HZ/10, a zone is below the high mark, it's premature */
1924         for (i = 0; i < pgdat->nr_zones; i++) {
1925                 struct zone *zone = pgdat->node_zones + i;
1926
1927                 if (!populated_zone(zone))
1928                         continue;
1929
1930                 if (zone_is_all_unreclaimable(zone))
1931                         continue;
1932
1933                 if (!zone_watermark_ok(zone, order, high_wmark_pages(zone),
1934                                                                 0, 0))
1935                         return 1;
1936         }
1937
1938         return 0;
1939 }
1940
1941 /*
1942  * For kswapd, balance_pgdat() will work across all this node's zones until
1943  * they are all at high_wmark_pages(zone).
1944  *
1945  * Returns the number of pages which were actually freed.
1946  *
1947  * There is special handling here for zones which are full of pinned pages.
1948  * This can happen if the pages are all mlocked, or if they are all used by
1949  * device drivers (say, ZONE_DMA).  Or if they are all in use by hugetlb.
1950  * What we do is to detect the case where all pages in the zone have been
1951  * scanned twice and there has been zero successful reclaim.  Mark the zone as
1952  * dead and from now on, only perform a short scan.  Basically we're polling
1953  * the zone for when the problem goes away.
1954  *
1955  * kswapd scans the zones in the highmem->normal->dma direction.  It skips
1956  * zones which have free_pages > high_wmark_pages(zone), but once a zone is
1957  * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
1958  * lower zones regardless of the number of free pages in the lower zones. This
1959  * interoperates with the page allocator fallback scheme to ensure that aging
1960  * of pages is balanced across the zones.
1961  */
1962 static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
1963 {
1964         int all_zones_ok;
1965         int priority;
1966         int i;
1967         unsigned long total_scanned;
1968         struct reclaim_state *reclaim_state = current->reclaim_state;
1969         struct scan_control sc = {
1970                 .gfp_mask = GFP_KERNEL,
1971                 .may_unmap = 1,
1972                 .may_swap = 1,
1973                 /*
1974                  * kswapd doesn't want to be bailed out while reclaim. because
1975                  * we want to put equal scanning pressure on each zone.
1976                  */
1977                 .nr_to_reclaim = ULONG_MAX,
1978                 .swappiness = vm_swappiness,
1979                 .order = order,
1980                 .mem_cgroup = NULL,
1981                 .isolate_pages = isolate_pages_global,
1982         };
1983         /*
1984          * temp_priority is used to remember the scanning priority at which
1985          * this zone was successfully refilled to
1986          * free_pages == high_wmark_pages(zone).
1987          */
1988         int temp_priority[MAX_NR_ZONES];
1989
1990 loop_again:
1991         total_scanned = 0;
1992         sc.nr_reclaimed = 0;
1993         sc.may_writepage = !laptop_mode;
1994         count_vm_event(PAGEOUTRUN);
1995
1996         for (i = 0; i < pgdat->nr_zones; i++)
1997                 temp_priority[i] = DEF_PRIORITY;
1998
1999         for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2000                 int end_zone = 0;       /* Inclusive.  0 = ZONE_DMA */
2001                 unsigned long lru_pages = 0;
2002                 int has_under_min_watermark_zone = 0;
2003
2004                 /* The swap token gets in the way of swapout... */
2005                 if (!priority)
2006                         disable_swap_token();
2007
2008                 all_zones_ok = 1;
2009
2010                 /*
2011                  * Scan in the highmem->dma direction for the highest
2012                  * zone which needs scanning
2013                  */
2014                 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
2015                         struct zone *zone = pgdat->node_zones + i;
2016
2017                         if (!populated_zone(zone))
2018                                 continue;
2019
2020                         if (zone_is_all_unreclaimable(zone) &&
2021                             priority != DEF_PRIORITY)
2022                                 continue;
2023
2024                         /*
2025                          * Do some background aging of the anon list, to give
2026                          * pages a chance to be referenced before reclaiming.
2027                          */
2028                         if (inactive_anon_is_low(zone, &sc))
2029                                 shrink_active_list(SWAP_CLUSTER_MAX, zone,
2030                                                         &sc, priority, 0);
2031
2032                         if (!zone_watermark_ok(zone, order,
2033                                         high_wmark_pages(zone), 0, 0)) {
2034                                 end_zone = i;
2035                                 break;
2036                         }
2037                 }
2038                 if (i < 0)
2039                         goto out;
2040
2041                 for (i = 0; i <= end_zone; i++) {
2042                         struct zone *zone = pgdat->node_zones + i;
2043
2044                         lru_pages += zone_reclaimable_pages(zone);
2045                 }
2046
2047                 /*
2048                  * Now scan the zone in the dma->highmem direction, stopping
2049                  * at the last zone which needs scanning.
2050                  *
2051                  * We do this because the page allocator works in the opposite
2052                  * direction.  This prevents the page allocator from allocating
2053                  * pages behind kswapd's direction of progress, which would
2054                  * cause too much scanning of the lower zones.
2055                  */
2056                 for (i = 0; i <= end_zone; i++) {
2057                         struct zone *zone = pgdat->node_zones + i;
2058                         int nr_slab;
2059                         int nid, zid;
2060
2061                         if (!populated_zone(zone))
2062                                 continue;
2063
2064                         if (zone_is_all_unreclaimable(zone) &&
2065                                         priority != DEF_PRIORITY)
2066                                 continue;
2067
2068                         temp_priority[i] = priority;
2069                         sc.nr_scanned = 0;
2070                         note_zone_scanning_priority(zone, priority);
2071
2072                         nid = pgdat->node_id;
2073                         zid = zone_idx(zone);
2074                         /*
2075                          * Call soft limit reclaim before calling shrink_zone.
2076                          * For now we ignore the return value
2077                          */
2078                         mem_cgroup_soft_limit_reclaim(zone, order, sc.gfp_mask,
2079                                                         nid, zid);
2080                         /*
2081                          * We put equal pressure on every zone, unless one
2082                          * zone has way too many pages free already.
2083                          */
2084                         if (!zone_watermark_ok(zone, order,
2085                                         8*high_wmark_pages(zone), end_zone, 0))
2086                                 shrink_zone(priority, zone, &sc);
2087                         reclaim_state->reclaimed_slab = 0;
2088                         nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
2089                                                 lru_pages);
2090                         sc.nr_reclaimed += reclaim_state->reclaimed_slab;
2091                         total_scanned += sc.nr_scanned;
2092                         if (zone_is_all_unreclaimable(zone))
2093                                 continue;
2094                         if (nr_slab == 0 && zone->pages_scanned >=
2095                                         (zone_reclaimable_pages(zone) * 6))
2096                                         zone_set_flag(zone,
2097                                                       ZONE_ALL_UNRECLAIMABLE);
2098                         /*
2099                          * If we've done a decent amount of scanning and
2100                          * the reclaim ratio is low, start doing writepage
2101                          * even in laptop mode
2102                          */
2103                         if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
2104                             total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
2105                                 sc.may_writepage = 1;
2106
2107                         if (!zone_watermark_ok(zone, order,
2108                                         high_wmark_pages(zone), end_zone, 0)) {
2109                                 all_zones_ok = 0;
2110                                 /*
2111                                  * We are still under min water mark.  This
2112                                  * means that we have a GFP_ATOMIC allocation
2113                                  * failure risk. Hurry up!
2114                                  */
2115                                 if (!zone_watermark_ok(zone, order,
2116                                             min_wmark_pages(zone), end_zone, 0))
2117                                         has_under_min_watermark_zone = 1;
2118                         }
2119
2120                 }
2121                 if (all_zones_ok)
2122                         break;          /* kswapd: all done */
2123                 /*
2124                  * OK, kswapd is getting into trouble.  Take a nap, then take
2125                  * another pass across the zones.
2126                  */
2127                 if (total_scanned && (priority < DEF_PRIORITY - 2)) {
2128                         if (has_under_min_watermark_zone)
2129                                 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT);
2130                         else
2131                                 congestion_wait(BLK_RW_ASYNC, HZ/10);
2132                 }
2133
2134                 /*
2135                  * We do this so kswapd doesn't build up large priorities for
2136                  * example when it is freeing in parallel with allocators. It
2137                  * matches the direct reclaim path behaviour in terms of impact
2138                  * on zone->*_priority.
2139                  */
2140                 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
2141                         break;
2142         }
2143 out:
2144         /*
2145          * Note within each zone the priority level at which this zone was
2146          * brought into a happy state.  So that the next thread which scans this
2147          * zone will start out at that priority level.
2148          */
2149         for (i = 0; i < pgdat->nr_zones; i++) {
2150                 struct zone *zone = pgdat->node_zones + i;
2151
2152                 zone->prev_priority = temp_priority[i];
2153         }
2154         if (!all_zones_ok) {
2155                 cond_resched();
2156
2157                 try_to_freeze();
2158
2159                 /*
2160                  * Fragmentation may mean that the system cannot be
2161                  * rebalanced for high-order allocations in all zones.
2162                  * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
2163                  * it means the zones have been fully scanned and are still
2164                  * not balanced. For high-order allocations, there is
2165                  * little point trying all over again as kswapd may
2166                  * infinite loop.
2167                  *
2168                  * Instead, recheck all watermarks at order-0 as they
2169                  * are the most important. If watermarks are ok, kswapd will go
2170                  * back to sleep. High-order users can still perform direct
2171                  * reclaim if they wish.
2172                  */
2173                 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX)
2174                         order = sc.order = 0;
2175
2176                 goto loop_again;
2177         }
2178
2179         return sc.nr_reclaimed;
2180 }
2181
2182 /*
2183  * The background pageout daemon, started as a kernel thread
2184  * from the init process.
2185  *
2186  * This basically trickles out pages so that we have _some_
2187  * free memory available even if there is no other activity
2188  * that frees anything up. This is needed for things like routing
2189  * etc, where we otherwise might have all activity going on in
2190  * asynchronous contexts that cannot page things out.
2191  *
2192  * If there are applications that are active memory-allocators
2193  * (most normal use), this basically shouldn't matter.
2194  */
2195 static int kswapd(void *p)
2196 {
2197         unsigned long order;
2198         pg_data_t *pgdat = (pg_data_t*)p;
2199         struct task_struct *tsk = current;
2200         DEFINE_WAIT(wait);
2201         struct reclaim_state reclaim_state = {
2202                 .reclaimed_slab = 0,
2203         };
2204         const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
2205
2206         lockdep_set_current_reclaim_state(GFP_KERNEL);
2207
2208         if (!cpumask_empty(cpumask))
2209                 set_cpus_allowed_ptr(tsk, cpumask);
2210         current->reclaim_state = &reclaim_state;
2211
2212         /*
2213          * Tell the memory management that we're a "memory allocator",
2214          * and that if we need more memory we should get access to it
2215          * regardless (see "__alloc_pages()"). "kswapd" should
2216          * never get caught in the normal page freeing logic.
2217          *
2218          * (Kswapd normally doesn't need memory anyway, but sometimes
2219          * you need a small amount of memory in order to be able to
2220          * page out something else, and this flag essentially protects
2221          * us from recursively trying to free more memory as we're
2222          * trying to free the first piece of memory in the first place).
2223          */
2224         tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
2225         set_freezable();
2226
2227         order = 0;
2228         for ( ; ; ) {
2229                 unsigned long new_order;
2230                 int ret;
2231
2232                 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2233                 new_order = pgdat->kswapd_max_order;
2234                 pgdat->kswapd_max_order = 0;
2235                 if (order < new_order) {
2236                         /*
2237                          * Don't sleep if someone wants a larger 'order'
2238                          * allocation
2239                          */
2240                         order = new_order;
2241                 } else {
2242                         if (!freezing(current) && !kthread_should_stop()) {
2243                                 long remaining = 0;
2244
2245                                 /* Try to sleep for a short interval */
2246                                 if (!sleeping_prematurely(pgdat, order, remaining)) {
2247                                         remaining = schedule_timeout(HZ/10);
2248                                         finish_wait(&pgdat->kswapd_wait, &wait);
2249                                         prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2250                                 }
2251
2252                                 /*
2253                                  * After a short sleep, check if it was a
2254                                  * premature sleep. If not, then go fully
2255                                  * to sleep until explicitly woken up
2256                                  */
2257                                 if (!sleeping_prematurely(pgdat, order, remaining))
2258                                         schedule();
2259                                 else {
2260                                         if (remaining)
2261                                                 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
2262                                         else
2263                                                 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
2264                                 }
2265                         }
2266
2267                         order = pgdat->kswapd_max_order;
2268                 }
2269                 finish_wait(&pgdat->kswapd_wait, &wait);
2270
2271                 ret = try_to_freeze();
2272                 if (kthread_should_stop())
2273                         break;
2274
2275                 /*
2276                  * We can speed up thawing tasks if we don't call balance_pgdat
2277                  * after returning from the refrigerator
2278                  */
2279                 if (!ret)
2280                         balance_pgdat(pgdat, order);
2281         }
2282         return 0;
2283 }
2284
2285 /*
2286  * A zone is low on free memory, so wake its kswapd task to service it.
2287  */
2288 void wakeup_kswapd(struct zone *zone, int order)
2289 {
2290         pg_data_t *pgdat;
2291
2292         if (!populated_zone(zone))
2293                 return;
2294
2295         pgdat = zone->zone_pgdat;
2296         if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0, 0))
2297                 return;
2298         if (pgdat->kswapd_max_order < order)
2299                 pgdat->kswapd_max_order = order;
2300         if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2301                 return;
2302         if (!waitqueue_active(&pgdat->kswapd_wait))
2303                 return;
2304         wake_up_interruptible(&pgdat->kswapd_wait);
2305 }
2306
2307 /*
2308  * The reclaimable count would be mostly accurate.
2309  * The less reclaimable pages may be
2310  * - mlocked pages, which will be moved to unevictable list when encountered
2311  * - mapped pages, which may require several travels to be reclaimed
2312  * - dirty pages, which is not "instantly" reclaimable
2313  */
2314 unsigned long global_reclaimable_pages(void)
2315 {
2316         int nr;
2317
2318         nr = global_page_state(NR_ACTIVE_FILE) +
2319              global_page_state(NR_INACTIVE_FILE);
2320
2321         if (nr_swap_pages > 0)
2322                 nr += global_page_state(NR_ACTIVE_ANON) +
2323                       global_page_state(NR_INACTIVE_ANON);
2324
2325         return nr;
2326 }
2327
2328 unsigned long zone_reclaimable_pages(struct zone *zone)
2329 {
2330         int nr;
2331
2332         nr = zone_page_state(zone, NR_ACTIVE_FILE) +
2333              zone_page_state(zone, NR_INACTIVE_FILE);
2334
2335         if (nr_swap_pages > 0)
2336                 nr += zone_page_state(zone, NR_ACTIVE_ANON) +
2337                       zone_page_state(zone, NR_INACTIVE_ANON);
2338
2339         return nr;
2340 }
2341
2342 #ifdef CONFIG_HIBERNATION
2343 /*
2344  * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
2345  * freed pages.
2346  *
2347  * Rather than trying to age LRUs the aim is to preserve the overall
2348  * LRU order by reclaiming preferentially
2349  * inactive > active > active referenced > active mapped
2350  */
2351 unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
2352 {
2353         struct reclaim_state reclaim_state;
2354         struct scan_control sc = {
2355                 .gfp_mask = GFP_HIGHUSER_MOVABLE,
2356                 .may_swap = 1,
2357                 .may_unmap = 1,
2358                 .may_writepage = 1,
2359                 .nr_to_reclaim = nr_to_reclaim,
2360                 .hibernation_mode = 1,
2361                 .swappiness = vm_swappiness,
2362                 .order = 0,
2363                 .isolate_pages = isolate_pages_global,
2364         };
2365         struct zonelist * zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
2366         struct task_struct *p = current;
2367         unsigned long nr_reclaimed;
2368
2369         p->flags |= PF_MEMALLOC;
2370         lockdep_set_current_reclaim_state(sc.gfp_mask);
2371         reclaim_state.reclaimed_slab = 0;
2372         p->reclaim_state = &reclaim_state;
2373
2374         nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
2375
2376         p->reclaim_state = NULL;
2377         lockdep_clear_current_reclaim_state();
2378         p->flags &= ~PF_MEMALLOC;
2379
2380         return nr_reclaimed;
2381 }
2382 #endif /* CONFIG_HIBERNATION */
2383
2384 /* It's optimal to keep kswapds on the same CPUs as their memory, but
2385    not required for correctness.  So if the last cpu in a node goes
2386    away, we get changed to run anywhere: as the first one comes back,
2387    restore their cpu bindings. */
2388 static int __devinit cpu_callback(struct notifier_block *nfb,
2389                                   unsigned long action, void *hcpu)
2390 {
2391         int nid;
2392
2393         if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2394                 for_each_node_state(nid, N_HIGH_MEMORY) {
2395                         pg_data_t *pgdat = NODE_DATA(nid);
2396                         const struct cpumask *mask;
2397
2398                         mask = cpumask_of_node(pgdat->node_id);
2399
2400                         if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
2401                                 /* One of our CPUs online: restore mask */
2402                                 set_cpus_allowed_ptr(pgdat->kswapd, mask);
2403                 }
2404         }
2405         return NOTIFY_OK;
2406 }
2407
2408 /*
2409  * This kswapd start function will be called by init and node-hot-add.
2410  * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2411  */
2412 int kswapd_run(int nid)
2413 {
2414         pg_data_t *pgdat = NODE_DATA(nid);
2415         int ret = 0;
2416
2417         if (pgdat->kswapd)
2418                 return 0;
2419
2420         pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
2421         if (IS_ERR(pgdat->kswapd)) {
2422                 /* failure at boot is fatal */
2423                 BUG_ON(system_state == SYSTEM_BOOTING);
2424                 printk("Failed to start kswapd on node %d\n",nid);
2425                 ret = -1;
2426         }
2427         return ret;
2428 }
2429
2430 /*
2431  * Called by memory hotplug when all memory in a node is offlined.
2432  */
2433 void kswapd_stop(int nid)
2434 {
2435         struct task_struct *kswapd = NODE_DATA(nid)->kswapd;
2436
2437         if (kswapd)
2438                 kthread_stop(kswapd);
2439 }
2440
2441 static int __init kswapd_init(void)
2442 {
2443         int nid;
2444
2445         swap_setup();
2446         for_each_node_state(nid, N_HIGH_MEMORY)
2447                 kswapd_run(nid);
2448         hotcpu_notifier(cpu_callback, 0);
2449         return 0;
2450 }
2451
2452 module_init(kswapd_init)
2453
2454 #ifdef CONFIG_NUMA
2455 /*
2456  * Zone reclaim mode
2457  *
2458  * If non-zero call zone_reclaim when the number of free pages falls below
2459  * the watermarks.
2460  */
2461 int zone_reclaim_mode __read_mostly;
2462
2463 #define RECLAIM_OFF 0
2464 #define RECLAIM_ZONE (1<<0)     /* Run shrink_inactive_list on the zone */
2465 #define RECLAIM_WRITE (1<<1)    /* Writeout pages during reclaim */
2466 #define RECLAIM_SWAP (1<<2)     /* Swap pages out during reclaim */
2467
2468 /*
2469  * Priority for ZONE_RECLAIM. This determines the fraction of pages
2470  * of a node considered for each zone_reclaim. 4 scans 1/16th of
2471  * a zone.
2472  */
2473 #define ZONE_RECLAIM_PRIORITY 4
2474
2475 /*
2476  * Percentage of pages in a zone that must be unmapped for zone_reclaim to
2477  * occur.
2478  */
2479 int sysctl_min_unmapped_ratio = 1;
2480
2481 /*
2482  * If the number of slab pages in a zone grows beyond this percentage then
2483  * slab reclaim needs to occur.
2484  */
2485 int sysctl_min_slab_ratio = 5;
2486
2487 static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
2488 {
2489         unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
2490         unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
2491                 zone_page_state(zone, NR_ACTIVE_FILE);
2492
2493         /*
2494          * It's possible for there to be more file mapped pages than
2495          * accounted for by the pages on the file LRU lists because
2496          * tmpfs pages accounted for as ANON can also be FILE_MAPPED
2497          */
2498         return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
2499 }
2500
2501 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
2502 static long zone_pagecache_reclaimable(struct zone *zone)
2503 {
2504         long nr_pagecache_reclaimable;
2505         long delta = 0;
2506
2507         /*
2508          * If RECLAIM_SWAP is set, then all file pages are considered
2509          * potentially reclaimable. Otherwise, we have to worry about
2510          * pages like swapcache and zone_unmapped_file_pages() provides
2511          * a better estimate
2512          */
2513         if (zone_reclaim_mode & RECLAIM_SWAP)
2514                 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
2515         else
2516                 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
2517
2518         /* If we can't clean pages, remove dirty pages from consideration */
2519         if (!(zone_reclaim_mode & RECLAIM_WRITE))
2520                 delta += zone_page_state(zone, NR_FILE_DIRTY);
2521
2522         /* Watch for any possible underflows due to delta */
2523         if (unlikely(delta > nr_pagecache_reclaimable))
2524                 delta = nr_pagecache_reclaimable;
2525
2526         return nr_pagecache_reclaimable - delta;
2527 }
2528
2529 /*
2530  * Try to free up some pages from this zone through reclaim.
2531  */
2532 static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2533 {
2534         /* Minimum pages needed in order to stay on node */
2535         const unsigned long nr_pages = 1 << order;
2536         struct task_struct *p = current;
2537         struct reclaim_state reclaim_state;
2538         int priority;
2539         struct scan_control sc = {
2540                 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
2541                 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
2542                 .may_swap = 1,
2543                 .nr_to_reclaim = max_t(unsigned long, nr_pages,
2544                                        SWAP_CLUSTER_MAX),
2545                 .gfp_mask = gfp_mask,
2546                 .swappiness = vm_swappiness,
2547                 .order = order,
2548                 .isolate_pages = isolate_pages_global,
2549         };
2550         unsigned long slab_reclaimable;
2551
2552         disable_swap_token();
2553         cond_resched();
2554         /*
2555          * We need to be able to allocate from the reserves for RECLAIM_SWAP
2556          * and we also need to be able to write out pages for RECLAIM_WRITE
2557          * and RECLAIM_SWAP.
2558          */
2559         p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
2560         lockdep_set_current_reclaim_state(gfp_mask);
2561         reclaim_state.reclaimed_slab = 0;
2562         p->reclaim_state = &reclaim_state;
2563
2564         if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
2565                 /*
2566                  * Free memory by calling shrink zone with increasing
2567                  * priorities until we have enough memory freed.
2568                  */
2569                 priority = ZONE_RECLAIM_PRIORITY;
2570                 do {
2571                         note_zone_scanning_priority(zone, priority);
2572                         shrink_zone(priority, zone, &sc);
2573                         priority--;
2574                 } while (priority >= 0 && sc.nr_reclaimed < nr_pages);
2575         }
2576
2577         slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2578         if (slab_reclaimable > zone->min_slab_pages) {
2579                 /*
2580                  * shrink_slab() does not currently allow us to determine how
2581                  * many pages were freed in this zone. So we take the current
2582                  * number of slab pages and shake the slab until it is reduced
2583                  * by the same nr_pages that we used for reclaiming unmapped
2584                  * pages.
2585                  *
2586                  * Note that shrink_slab will free memory on all zones and may
2587                  * take a long time.
2588                  */
2589                 while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
2590                         zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
2591                                 slab_reclaimable - nr_pages)
2592                         ;
2593
2594                 /*
2595                  * Update nr_reclaimed by the number of slab pages we
2596                  * reclaimed from this zone.
2597                  */
2598                 sc.nr_reclaimed += slab_reclaimable -
2599                         zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2600         }
2601
2602         p->reclaim_state = NULL;
2603         current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
2604         lockdep_clear_current_reclaim_state();
2605         return sc.nr_reclaimed >= nr_pages;
2606 }
2607
2608 int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2609 {
2610         int node_id;
2611         int ret;
2612
2613         /*
2614          * Zone reclaim reclaims unmapped file backed pages and
2615          * slab pages if we are over the defined limits.
2616          *
2617          * A small portion of unmapped file backed pages is needed for
2618          * file I/O otherwise pages read by file I/O will be immediately
2619          * thrown out if the zone is overallocated. So we do not reclaim
2620          * if less than a specified percentage of the zone is used by
2621          * unmapped file backed pages.
2622          */
2623         if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
2624             zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
2625                 return ZONE_RECLAIM_FULL;
2626
2627         if (zone_is_all_unreclaimable(zone))
2628                 return ZONE_RECLAIM_FULL;
2629
2630         /*
2631          * Do not scan if the allocation should not be delayed.
2632          */
2633         if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
2634                 return ZONE_RECLAIM_NOSCAN;
2635
2636         /*
2637          * Only run zone reclaim on the local zone or on zones that do not
2638          * have associated processors. This will favor the local processor
2639          * over remote processors and spread off node memory allocations
2640          * as wide as possible.
2641          */
2642         node_id = zone_to_nid(zone);
2643         if (node_state(node_id, N_CPU) && node_id != numa_node_id())
2644                 return ZONE_RECLAIM_NOSCAN;
2645
2646         if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
2647                 return ZONE_RECLAIM_NOSCAN;
2648
2649         ret = __zone_reclaim(zone, gfp_mask, order);
2650         zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
2651
2652         if (!ret)
2653                 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
2654
2655         return ret;
2656 }
2657 #endif
2658
2659 /*
2660  * page_evictable - test whether a page is evictable
2661  * @page: the page to test
2662  * @vma: the VMA in which the page is or will be mapped, may be NULL
2663  *
2664  * Test whether page is evictable--i.e., should be placed on active/inactive
2665  * lists vs unevictable list.  The vma argument is !NULL when called from the
2666  * fault path to determine how to instantate a new page.
2667  *
2668  * Reasons page might not be evictable:
2669  * (1) page's mapping marked unevictable
2670  * (2) page is part of an mlocked VMA
2671  *
2672  */
2673 int page_evictable(struct page *page, struct vm_area_struct *vma)
2674 {
2675
2676         if (mapping_unevictable(page_mapping(page)))
2677                 return 0;
2678
2679         if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
2680                 return 0;
2681
2682         return 1;
2683 }
2684
2685 /**
2686  * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
2687  * @page: page to check evictability and move to appropriate lru list
2688  * @zone: zone page is in
2689  *
2690  * Checks a page for evictability and moves the page to the appropriate
2691  * zone lru list.
2692  *
2693  * Restrictions: zone->lru_lock must be held, page must be on LRU and must
2694  * have PageUnevictable set.
2695  */
2696 static void check_move_unevictable_page(struct page *page, struct zone *zone)
2697 {
2698         VM_BUG_ON(PageActive(page));
2699
2700 retry:
2701         ClearPageUnevictable(page);
2702         if (page_evictable(page, NULL)) {
2703                 enum lru_list l = page_lru_base_type(page);
2704
2705                 __dec_zone_state(zone, NR_UNEVICTABLE);
2706                 list_move(&page->lru, &zone->lru[l].list);
2707                 mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l);
2708                 __inc_zone_state(zone, NR_INACTIVE_ANON + l);
2709                 __count_vm_event(UNEVICTABLE_PGRESCUED);
2710         } else {
2711                 /*
2712                  * rotate unevictable list
2713                  */
2714                 SetPageUnevictable(page);
2715                 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
2716                 mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE);
2717                 if (page_evictable(page, NULL))
2718                         goto retry;
2719         }
2720 }
2721
2722 /**
2723  * scan_mapping_unevictable_pages - scan an address space for evictable pages
2724  * @mapping: struct address_space to scan for evictable pages
2725  *
2726  * Scan all pages in mapping.  Check unevictable pages for
2727  * evictability and move them to the appropriate zone lru list.
2728  */
2729 void scan_mapping_unevictable_pages(struct address_space *mapping)
2730 {
2731         pgoff_t next = 0;
2732         pgoff_t end   = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >>
2733                          PAGE_CACHE_SHIFT;
2734         struct zone *zone;
2735         struct pagevec pvec;
2736
2737         if (mapping->nrpages == 0)
2738                 return;
2739
2740         pagevec_init(&pvec, 0);
2741         while (next < end &&
2742                 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
2743                 int i;
2744                 int pg_scanned = 0;
2745
2746                 zone = NULL;
2747
2748                 for (i = 0; i < pagevec_count(&pvec); i++) {
2749                         struct page *page = pvec.pages[i];
2750                         pgoff_t page_index = page->index;
2751                         struct zone *pagezone = page_zone(page);
2752
2753                         pg_scanned++;
2754                         if (page_index > next)
2755                                 next = page_index;
2756                         next++;
2757
2758                         if (pagezone != zone) {
2759                                 if (zone)
2760                                         spin_unlock_irq(&zone->lru_lock);
2761                                 zone = pagezone;
2762                                 spin_lock_irq(&zone->lru_lock);
2763                         }
2764
2765                         if (PageLRU(page) && PageUnevictable(page))
2766                                 check_move_unevictable_page(page, zone);
2767                 }
2768                 if (zone)
2769                         spin_unlock_irq(&zone->lru_lock);
2770                 pagevec_release(&pvec);
2771
2772                 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
2773         }
2774
2775 }
2776
2777 /**
2778  * scan_zone_unevictable_pages - check unevictable list for evictable pages
2779  * @zone - zone of which to scan the unevictable list
2780  *
2781  * Scan @zone's unevictable LRU lists to check for pages that have become
2782  * evictable.  Move those that have to @zone's inactive list where they
2783  * become candidates for reclaim, unless shrink_inactive_zone() decides
2784  * to reactivate them.  Pages that are still unevictable are rotated
2785  * back onto @zone's unevictable list.
2786  */
2787 #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
2788 static void scan_zone_unevictable_pages(struct zone *zone)
2789 {
2790         struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list;
2791         unsigned long scan;
2792         unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE);
2793
2794         while (nr_to_scan > 0) {
2795                 unsigned long batch_size = min(nr_to_scan,
2796                                                 SCAN_UNEVICTABLE_BATCH_SIZE);
2797
2798                 spin_lock_irq(&zone->lru_lock);
2799                 for (scan = 0;  scan < batch_size; scan++) {
2800                         struct page *page = lru_to_page(l_unevictable);
2801
2802                         if (!trylock_page(page))
2803                                 continue;
2804
2805                         prefetchw_prev_lru_page(page, l_unevictable, flags);
2806
2807                         if (likely(PageLRU(page) && PageUnevictable(page)))
2808                                 check_move_unevictable_page(page, zone);
2809
2810                         unlock_page(page);
2811                 }
2812                 spin_unlock_irq(&zone->lru_lock);
2813
2814                 nr_to_scan -= batch_size;
2815         }
2816 }
2817
2818
2819 /**
2820  * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
2821  *
2822  * A really big hammer:  scan all zones' unevictable LRU lists to check for
2823  * pages that have become evictable.  Move those back to the zones'
2824  * inactive list where they become candidates for reclaim.
2825  * This occurs when, e.g., we have unswappable pages on the unevictable lists,
2826  * and we add swap to the system.  As such, it runs in the context of a task
2827  * that has possibly/probably made some previously unevictable pages
2828  * evictable.
2829  */
2830 static void scan_all_zones_unevictable_pages(void)
2831 {
2832         struct zone *zone;
2833
2834         for_each_zone(zone) {
2835                 scan_zone_unevictable_pages(zone);
2836         }
2837 }
2838
2839 /*
2840  * scan_unevictable_pages [vm] sysctl handler.  On demand re-scan of
2841  * all nodes' unevictable lists for evictable pages
2842  */
2843 unsigned long scan_unevictable_pages;
2844
2845 int scan_unevictable_handler(struct ctl_table *table, int write,
2846                            void __user *buffer,
2847                            size_t *length, loff_t *ppos)
2848 {
2849         proc_doulongvec_minmax(table, write, buffer, length, ppos);
2850
2851         if (write && *(unsigned long *)table->data)
2852                 scan_all_zones_unevictable_pages();
2853
2854         scan_unevictable_pages = 0;
2855         return 0;
2856 }
2857
2858 /*
2859  * per node 'scan_unevictable_pages' attribute.  On demand re-scan of
2860  * a specified node's per zone unevictable lists for evictable pages.
2861  */
2862
2863 static ssize_t read_scan_unevictable_node(struct sys_device *dev,
2864                                           struct sysdev_attribute *attr,
2865                                           char *buf)
2866 {
2867         return sprintf(buf, "0\n");     /* always zero; should fit... */
2868 }
2869
2870 static ssize_t write_scan_unevictable_node(struct sys_device *dev,
2871                                            struct sysdev_attribute *attr,
2872                                         const char *buf, size_t count)
2873 {
2874         struct zone *node_zones = NODE_DATA(dev->id)->node_zones;
2875         struct zone *zone;
2876         unsigned long res;
2877         unsigned long req = strict_strtoul(buf, 10, &res);
2878
2879         if (!req)
2880                 return 1;       /* zero is no-op */
2881
2882         for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
2883                 if (!populated_zone(zone))
2884                         continue;
2885                 scan_zone_unevictable_pages(zone);
2886         }
2887         return 1;
2888 }
2889
2890
2891 static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
2892                         read_scan_unevictable_node,
2893                         write_scan_unevictable_node);
2894
2895 int scan_unevictable_register_node(struct node *node)
2896 {
2897         return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages);
2898 }
2899
2900 void scan_unevictable_unregister_node(struct node *node)
2901 {
2902         sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages);
2903 }
2904