memcg: Revert "memcg: add memory.vmscan_stat"
[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/gfp.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/compaction.h>
36 #include <linux/notifier.h>
37 #include <linux/rwsem.h>
38 #include <linux/delay.h>
39 #include <linux/kthread.h>
40 #include <linux/freezer.h>
41 #include <linux/memcontrol.h>
42 #include <linux/delayacct.h>
43 #include <linux/sysctl.h>
44 #include <linux/oom.h>
45 #include <linux/prefetch.h>
46
47 #include <asm/tlbflush.h>
48 #include <asm/div64.h>
49
50 #include <linux/swapops.h>
51
52 #include "internal.h"
53
54 #define CREATE_TRACE_POINTS
55 #include <trace/events/vmscan.h>
56
57 /*
58  * reclaim_mode determines how the inactive list is shrunk
59  * RECLAIM_MODE_SINGLE: Reclaim only order-0 pages
60  * RECLAIM_MODE_ASYNC:  Do not block
61  * RECLAIM_MODE_SYNC:   Allow blocking e.g. call wait_on_page_writeback
62  * RECLAIM_MODE_LUMPYRECLAIM: For high-order allocations, take a reference
63  *                      page from the LRU and reclaim all pages within a
64  *                      naturally aligned range
65  * RECLAIM_MODE_COMPACTION: For high-order allocations, reclaim a number of
66  *                      order-0 pages and then compact the zone
67  */
68 typedef unsigned __bitwise__ reclaim_mode_t;
69 #define RECLAIM_MODE_SINGLE             ((__force reclaim_mode_t)0x01u)
70 #define RECLAIM_MODE_ASYNC              ((__force reclaim_mode_t)0x02u)
71 #define RECLAIM_MODE_SYNC               ((__force reclaim_mode_t)0x04u)
72 #define RECLAIM_MODE_LUMPYRECLAIM       ((__force reclaim_mode_t)0x08u)
73 #define RECLAIM_MODE_COMPACTION         ((__force reclaim_mode_t)0x10u)
74
75 struct scan_control {
76         /* Incremented by the number of inactive pages that were scanned */
77         unsigned long nr_scanned;
78
79         /* Number of pages freed so far during a call to shrink_zones() */
80         unsigned long nr_reclaimed;
81
82         /* How many pages shrink_list() should reclaim */
83         unsigned long nr_to_reclaim;
84
85         unsigned long hibernation_mode;
86
87         /* This context's GFP mask */
88         gfp_t gfp_mask;
89
90         int may_writepage;
91
92         /* Can mapped pages be reclaimed? */
93         int may_unmap;
94
95         /* Can pages be swapped as part of reclaim? */
96         int may_swap;
97
98         int order;
99
100         /*
101          * Intend to reclaim enough continuous memory rather than reclaim
102          * enough amount of memory. i.e, mode for high order allocation.
103          */
104         reclaim_mode_t reclaim_mode;
105
106         /* Which cgroup do we reclaim from */
107         struct mem_cgroup *mem_cgroup;
108
109         /*
110          * Nodemask of nodes allowed by the caller. If NULL, all nodes
111          * are scanned.
112          */
113         nodemask_t      *nodemask;
114 };
115
116 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
117
118 #ifdef ARCH_HAS_PREFETCH
119 #define prefetch_prev_lru_page(_page, _base, _field)                    \
120         do {                                                            \
121                 if ((_page)->lru.prev != _base) {                       \
122                         struct page *prev;                              \
123                                                                         \
124                         prev = lru_to_page(&(_page->lru));              \
125                         prefetch(&prev->_field);                        \
126                 }                                                       \
127         } while (0)
128 #else
129 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
130 #endif
131
132 #ifdef ARCH_HAS_PREFETCHW
133 #define prefetchw_prev_lru_page(_page, _base, _field)                   \
134         do {                                                            \
135                 if ((_page)->lru.prev != _base) {                       \
136                         struct page *prev;                              \
137                                                                         \
138                         prev = lru_to_page(&(_page->lru));              \
139                         prefetchw(&prev->_field);                       \
140                 }                                                       \
141         } while (0)
142 #else
143 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
144 #endif
145
146 /*
147  * From 0 .. 100.  Higher means more swappy.
148  */
149 int vm_swappiness = 60;
150 long vm_total_pages;    /* The total number of pages which the VM controls */
151
152 static LIST_HEAD(shrinker_list);
153 static DECLARE_RWSEM(shrinker_rwsem);
154
155 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
156 #define scanning_global_lru(sc) (!(sc)->mem_cgroup)
157 #else
158 #define scanning_global_lru(sc) (1)
159 #endif
160
161 static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone,
162                                                   struct scan_control *sc)
163 {
164         if (!scanning_global_lru(sc))
165                 return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone);
166
167         return &zone->reclaim_stat;
168 }
169
170 static unsigned long zone_nr_lru_pages(struct zone *zone,
171                                 struct scan_control *sc, enum lru_list lru)
172 {
173         if (!scanning_global_lru(sc))
174                 return mem_cgroup_zone_nr_lru_pages(sc->mem_cgroup,
175                                 zone_to_nid(zone), zone_idx(zone), BIT(lru));
176
177         return zone_page_state(zone, NR_LRU_BASE + lru);
178 }
179
180
181 /*
182  * Add a shrinker callback to be called from the vm
183  */
184 void register_shrinker(struct shrinker *shrinker)
185 {
186         shrinker->nr = 0;
187         down_write(&shrinker_rwsem);
188         list_add_tail(&shrinker->list, &shrinker_list);
189         up_write(&shrinker_rwsem);
190 }
191 EXPORT_SYMBOL(register_shrinker);
192
193 /*
194  * Remove one
195  */
196 void unregister_shrinker(struct shrinker *shrinker)
197 {
198         down_write(&shrinker_rwsem);
199         list_del(&shrinker->list);
200         up_write(&shrinker_rwsem);
201 }
202 EXPORT_SYMBOL(unregister_shrinker);
203
204 static inline int do_shrinker_shrink(struct shrinker *shrinker,
205                                      struct shrink_control *sc,
206                                      unsigned long nr_to_scan)
207 {
208         sc->nr_to_scan = nr_to_scan;
209         return (*shrinker->shrink)(shrinker, sc);
210 }
211
212 #define SHRINK_BATCH 128
213 /*
214  * Call the shrink functions to age shrinkable caches
215  *
216  * Here we assume it costs one seek to replace a lru page and that it also
217  * takes a seek to recreate a cache object.  With this in mind we age equal
218  * percentages of the lru and ageable caches.  This should balance the seeks
219  * generated by these structures.
220  *
221  * If the vm encountered mapped pages on the LRU it increase the pressure on
222  * slab to avoid swapping.
223  *
224  * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
225  *
226  * `lru_pages' represents the number of on-LRU pages in all the zones which
227  * are eligible for the caller's allocation attempt.  It is used for balancing
228  * slab reclaim versus page reclaim.
229  *
230  * Returns the number of slab objects which we shrunk.
231  */
232 unsigned long shrink_slab(struct shrink_control *shrink,
233                           unsigned long nr_pages_scanned,
234                           unsigned long lru_pages)
235 {
236         struct shrinker *shrinker;
237         unsigned long ret = 0;
238
239         if (nr_pages_scanned == 0)
240                 nr_pages_scanned = SWAP_CLUSTER_MAX;
241
242         if (!down_read_trylock(&shrinker_rwsem)) {
243                 /* Assume we'll be able to shrink next time */
244                 ret = 1;
245                 goto out;
246         }
247
248         list_for_each_entry(shrinker, &shrinker_list, list) {
249                 unsigned long long delta;
250                 unsigned long total_scan;
251                 unsigned long max_pass;
252                 int shrink_ret = 0;
253                 long nr;
254                 long new_nr;
255                 long batch_size = shrinker->batch ? shrinker->batch
256                                                   : SHRINK_BATCH;
257
258                 /*
259                  * copy the current shrinker scan count into a local variable
260                  * and zero it so that other concurrent shrinker invocations
261                  * don't also do this scanning work.
262                  */
263                 do {
264                         nr = shrinker->nr;
265                 } while (cmpxchg(&shrinker->nr, nr, 0) != nr);
266
267                 total_scan = nr;
268                 max_pass = do_shrinker_shrink(shrinker, shrink, 0);
269                 delta = (4 * nr_pages_scanned) / shrinker->seeks;
270                 delta *= max_pass;
271                 do_div(delta, lru_pages + 1);
272                 total_scan += delta;
273                 if (total_scan < 0) {
274                         printk(KERN_ERR "shrink_slab: %pF negative objects to "
275                                "delete nr=%ld\n",
276                                shrinker->shrink, total_scan);
277                         total_scan = max_pass;
278                 }
279
280                 /*
281                  * We need to avoid excessive windup on filesystem shrinkers
282                  * due to large numbers of GFP_NOFS allocations causing the
283                  * shrinkers to return -1 all the time. This results in a large
284                  * nr being built up so when a shrink that can do some work
285                  * comes along it empties the entire cache due to nr >>>
286                  * max_pass.  This is bad for sustaining a working set in
287                  * memory.
288                  *
289                  * Hence only allow the shrinker to scan the entire cache when
290                  * a large delta change is calculated directly.
291                  */
292                 if (delta < max_pass / 4)
293                         total_scan = min(total_scan, max_pass / 2);
294
295                 /*
296                  * Avoid risking looping forever due to too large nr value:
297                  * never try to free more than twice the estimate number of
298                  * freeable entries.
299                  */
300                 if (total_scan > max_pass * 2)
301                         total_scan = max_pass * 2;
302
303                 trace_mm_shrink_slab_start(shrinker, shrink, nr,
304                                         nr_pages_scanned, lru_pages,
305                                         max_pass, delta, total_scan);
306
307                 while (total_scan >= batch_size) {
308                         int nr_before;
309
310                         nr_before = do_shrinker_shrink(shrinker, shrink, 0);
311                         shrink_ret = do_shrinker_shrink(shrinker, shrink,
312                                                         batch_size);
313                         if (shrink_ret == -1)
314                                 break;
315                         if (shrink_ret < nr_before)
316                                 ret += nr_before - shrink_ret;
317                         count_vm_events(SLABS_SCANNED, batch_size);
318                         total_scan -= batch_size;
319
320                         cond_resched();
321                 }
322
323                 /*
324                  * move the unused scan count back into the shrinker in a
325                  * manner that handles concurrent updates. If we exhausted the
326                  * scan, there is no need to do an update.
327                  */
328                 do {
329                         nr = shrinker->nr;
330                         new_nr = total_scan + nr;
331                         if (total_scan <= 0)
332                                 break;
333                 } while (cmpxchg(&shrinker->nr, nr, new_nr) != nr);
334
335                 trace_mm_shrink_slab_end(shrinker, shrink_ret, nr, new_nr);
336         }
337         up_read(&shrinker_rwsem);
338 out:
339         cond_resched();
340         return ret;
341 }
342
343 static void set_reclaim_mode(int priority, struct scan_control *sc,
344                                    bool sync)
345 {
346         reclaim_mode_t syncmode = sync ? RECLAIM_MODE_SYNC : RECLAIM_MODE_ASYNC;
347
348         /*
349          * Initially assume we are entering either lumpy reclaim or
350          * reclaim/compaction.Depending on the order, we will either set the
351          * sync mode or just reclaim order-0 pages later.
352          */
353         if (COMPACTION_BUILD)
354                 sc->reclaim_mode = RECLAIM_MODE_COMPACTION;
355         else
356                 sc->reclaim_mode = RECLAIM_MODE_LUMPYRECLAIM;
357
358         /*
359          * Avoid using lumpy reclaim or reclaim/compaction if possible by
360          * restricting when its set to either costly allocations or when
361          * under memory pressure
362          */
363         if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
364                 sc->reclaim_mode |= syncmode;
365         else if (sc->order && priority < DEF_PRIORITY - 2)
366                 sc->reclaim_mode |= syncmode;
367         else
368                 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC;
369 }
370
371 static void reset_reclaim_mode(struct scan_control *sc)
372 {
373         sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC;
374 }
375
376 static inline int is_page_cache_freeable(struct page *page)
377 {
378         /*
379          * A freeable page cache page is referenced only by the caller
380          * that isolated the page, the page cache radix tree and
381          * optional buffer heads at page->private.
382          */
383         return page_count(page) - page_has_private(page) == 2;
384 }
385
386 static int may_write_to_queue(struct backing_dev_info *bdi,
387                               struct scan_control *sc)
388 {
389         if (current->flags & PF_SWAPWRITE)
390                 return 1;
391         if (!bdi_write_congested(bdi))
392                 return 1;
393         if (bdi == current->backing_dev_info)
394                 return 1;
395
396         /* lumpy reclaim for hugepage often need a lot of write */
397         if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
398                 return 1;
399         return 0;
400 }
401
402 /*
403  * We detected a synchronous write error writing a page out.  Probably
404  * -ENOSPC.  We need to propagate that into the address_space for a subsequent
405  * fsync(), msync() or close().
406  *
407  * The tricky part is that after writepage we cannot touch the mapping: nothing
408  * prevents it from being freed up.  But we have a ref on the page and once
409  * that page is locked, the mapping is pinned.
410  *
411  * We're allowed to run sleeping lock_page() here because we know the caller has
412  * __GFP_FS.
413  */
414 static void handle_write_error(struct address_space *mapping,
415                                 struct page *page, int error)
416 {
417         lock_page(page);
418         if (page_mapping(page) == mapping)
419                 mapping_set_error(mapping, error);
420         unlock_page(page);
421 }
422
423 /* possible outcome of pageout() */
424 typedef enum {
425         /* failed to write page out, page is locked */
426         PAGE_KEEP,
427         /* move page to the active list, page is locked */
428         PAGE_ACTIVATE,
429         /* page has been sent to the disk successfully, page is unlocked */
430         PAGE_SUCCESS,
431         /* page is clean and locked */
432         PAGE_CLEAN,
433 } pageout_t;
434
435 /*
436  * pageout is called by shrink_page_list() for each dirty page.
437  * Calls ->writepage().
438  */
439 static pageout_t pageout(struct page *page, struct address_space *mapping,
440                          struct scan_control *sc)
441 {
442         /*
443          * If the page is dirty, only perform writeback if that write
444          * will be non-blocking.  To prevent this allocation from being
445          * stalled by pagecache activity.  But note that there may be
446          * stalls if we need to run get_block().  We could test
447          * PagePrivate for that.
448          *
449          * If this process is currently in __generic_file_aio_write() against
450          * this page's queue, we can perform writeback even if that
451          * will block.
452          *
453          * If the page is swapcache, write it back even if that would
454          * block, for some throttling. This happens by accident, because
455          * swap_backing_dev_info is bust: it doesn't reflect the
456          * congestion state of the swapdevs.  Easy to fix, if needed.
457          */
458         if (!is_page_cache_freeable(page))
459                 return PAGE_KEEP;
460         if (!mapping) {
461                 /*
462                  * Some data journaling orphaned pages can have
463                  * page->mapping == NULL while being dirty with clean buffers.
464                  */
465                 if (page_has_private(page)) {
466                         if (try_to_free_buffers(page)) {
467                                 ClearPageDirty(page);
468                                 printk("%s: orphaned page\n", __func__);
469                                 return PAGE_CLEAN;
470                         }
471                 }
472                 return PAGE_KEEP;
473         }
474         if (mapping->a_ops->writepage == NULL)
475                 return PAGE_ACTIVATE;
476         if (!may_write_to_queue(mapping->backing_dev_info, sc))
477                 return PAGE_KEEP;
478
479         if (clear_page_dirty_for_io(page)) {
480                 int res;
481                 struct writeback_control wbc = {
482                         .sync_mode = WB_SYNC_NONE,
483                         .nr_to_write = SWAP_CLUSTER_MAX,
484                         .range_start = 0,
485                         .range_end = LLONG_MAX,
486                         .for_reclaim = 1,
487                 };
488
489                 SetPageReclaim(page);
490                 res = mapping->a_ops->writepage(page, &wbc);
491                 if (res < 0)
492                         handle_write_error(mapping, page, res);
493                 if (res == AOP_WRITEPAGE_ACTIVATE) {
494                         ClearPageReclaim(page);
495                         return PAGE_ACTIVATE;
496                 }
497
498                 /*
499                  * Wait on writeback if requested to. This happens when
500                  * direct reclaiming a large contiguous area and the
501                  * first attempt to free a range of pages fails.
502                  */
503                 if (PageWriteback(page) &&
504                     (sc->reclaim_mode & RECLAIM_MODE_SYNC))
505                         wait_on_page_writeback(page);
506
507                 if (!PageWriteback(page)) {
508                         /* synchronous write or broken a_ops? */
509                         ClearPageReclaim(page);
510                 }
511                 trace_mm_vmscan_writepage(page,
512                         trace_reclaim_flags(page, sc->reclaim_mode));
513                 inc_zone_page_state(page, NR_VMSCAN_WRITE);
514                 return PAGE_SUCCESS;
515         }
516
517         return PAGE_CLEAN;
518 }
519
520 /*
521  * Same as remove_mapping, but if the page is removed from the mapping, it
522  * gets returned with a refcount of 0.
523  */
524 static int __remove_mapping(struct address_space *mapping, struct page *page)
525 {
526         BUG_ON(!PageLocked(page));
527         BUG_ON(mapping != page_mapping(page));
528
529         spin_lock_irq(&mapping->tree_lock);
530         /*
531          * The non racy check for a busy page.
532          *
533          * Must be careful with the order of the tests. When someone has
534          * a ref to the page, it may be possible that they dirty it then
535          * drop the reference. So if PageDirty is tested before page_count
536          * here, then the following race may occur:
537          *
538          * get_user_pages(&page);
539          * [user mapping goes away]
540          * write_to(page);
541          *                              !PageDirty(page)    [good]
542          * SetPageDirty(page);
543          * put_page(page);
544          *                              !page_count(page)   [good, discard it]
545          *
546          * [oops, our write_to data is lost]
547          *
548          * Reversing the order of the tests ensures such a situation cannot
549          * escape unnoticed. The smp_rmb is needed to ensure the page->flags
550          * load is not satisfied before that of page->_count.
551          *
552          * Note that if SetPageDirty is always performed via set_page_dirty,
553          * and thus under tree_lock, then this ordering is not required.
554          */
555         if (!page_freeze_refs(page, 2))
556                 goto cannot_free;
557         /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
558         if (unlikely(PageDirty(page))) {
559                 page_unfreeze_refs(page, 2);
560                 goto cannot_free;
561         }
562
563         if (PageSwapCache(page)) {
564                 swp_entry_t swap = { .val = page_private(page) };
565                 __delete_from_swap_cache(page);
566                 spin_unlock_irq(&mapping->tree_lock);
567                 swapcache_free(swap, page);
568         } else {
569                 void (*freepage)(struct page *);
570
571                 freepage = mapping->a_ops->freepage;
572
573                 __delete_from_page_cache(page);
574                 spin_unlock_irq(&mapping->tree_lock);
575                 mem_cgroup_uncharge_cache_page(page);
576
577                 if (freepage != NULL)
578                         freepage(page);
579         }
580
581         return 1;
582
583 cannot_free:
584         spin_unlock_irq(&mapping->tree_lock);
585         return 0;
586 }
587
588 /*
589  * Attempt to detach a locked page from its ->mapping.  If it is dirty or if
590  * someone else has a ref on the page, abort and return 0.  If it was
591  * successfully detached, return 1.  Assumes the caller has a single ref on
592  * this page.
593  */
594 int remove_mapping(struct address_space *mapping, struct page *page)
595 {
596         if (__remove_mapping(mapping, page)) {
597                 /*
598                  * Unfreezing the refcount with 1 rather than 2 effectively
599                  * drops the pagecache ref for us without requiring another
600                  * atomic operation.
601                  */
602                 page_unfreeze_refs(page, 1);
603                 return 1;
604         }
605         return 0;
606 }
607
608 /**
609  * putback_lru_page - put previously isolated page onto appropriate LRU list
610  * @page: page to be put back to appropriate lru list
611  *
612  * Add previously isolated @page to appropriate LRU list.
613  * Page may still be unevictable for other reasons.
614  *
615  * lru_lock must not be held, interrupts must be enabled.
616  */
617 void putback_lru_page(struct page *page)
618 {
619         int lru;
620         int active = !!TestClearPageActive(page);
621         int was_unevictable = PageUnevictable(page);
622
623         VM_BUG_ON(PageLRU(page));
624
625 redo:
626         ClearPageUnevictable(page);
627
628         if (page_evictable(page, NULL)) {
629                 /*
630                  * For evictable pages, we can use the cache.
631                  * In event of a race, worst case is we end up with an
632                  * unevictable page on [in]active list.
633                  * We know how to handle that.
634                  */
635                 lru = active + page_lru_base_type(page);
636                 lru_cache_add_lru(page, lru);
637         } else {
638                 /*
639                  * Put unevictable pages directly on zone's unevictable
640                  * list.
641                  */
642                 lru = LRU_UNEVICTABLE;
643                 add_page_to_unevictable_list(page);
644                 /*
645                  * When racing with an mlock clearing (page is
646                  * unlocked), make sure that if the other thread does
647                  * not observe our setting of PG_lru and fails
648                  * isolation, we see PG_mlocked cleared below and move
649                  * the page back to the evictable list.
650                  *
651                  * The other side is TestClearPageMlocked().
652                  */
653                 smp_mb();
654         }
655
656         /*
657          * page's status can change while we move it among lru. If an evictable
658          * page is on unevictable list, it never be freed. To avoid that,
659          * check after we added it to the list, again.
660          */
661         if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
662                 if (!isolate_lru_page(page)) {
663                         put_page(page);
664                         goto redo;
665                 }
666                 /* This means someone else dropped this page from LRU
667                  * So, it will be freed or putback to LRU again. There is
668                  * nothing to do here.
669                  */
670         }
671
672         if (was_unevictable && lru != LRU_UNEVICTABLE)
673                 count_vm_event(UNEVICTABLE_PGRESCUED);
674         else if (!was_unevictable && lru == LRU_UNEVICTABLE)
675                 count_vm_event(UNEVICTABLE_PGCULLED);
676
677         put_page(page);         /* drop ref from isolate */
678 }
679
680 enum page_references {
681         PAGEREF_RECLAIM,
682         PAGEREF_RECLAIM_CLEAN,
683         PAGEREF_KEEP,
684         PAGEREF_ACTIVATE,
685 };
686
687 static enum page_references page_check_references(struct page *page,
688                                                   struct scan_control *sc)
689 {
690         int referenced_ptes, referenced_page;
691         unsigned long vm_flags;
692
693         referenced_ptes = page_referenced(page, 1, sc->mem_cgroup, &vm_flags);
694         referenced_page = TestClearPageReferenced(page);
695
696         /* Lumpy reclaim - ignore references */
697         if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM)
698                 return PAGEREF_RECLAIM;
699
700         /*
701          * Mlock lost the isolation race with us.  Let try_to_unmap()
702          * move the page to the unevictable list.
703          */
704         if (vm_flags & VM_LOCKED)
705                 return PAGEREF_RECLAIM;
706
707         if (referenced_ptes) {
708                 if (PageAnon(page))
709                         return PAGEREF_ACTIVATE;
710                 /*
711                  * All mapped pages start out with page table
712                  * references from the instantiating fault, so we need
713                  * to look twice if a mapped file page is used more
714                  * than once.
715                  *
716                  * Mark it and spare it for another trip around the
717                  * inactive list.  Another page table reference will
718                  * lead to its activation.
719                  *
720                  * Note: the mark is set for activated pages as well
721                  * so that recently deactivated but used pages are
722                  * quickly recovered.
723                  */
724                 SetPageReferenced(page);
725
726                 if (referenced_page)
727                         return PAGEREF_ACTIVATE;
728
729                 return PAGEREF_KEEP;
730         }
731
732         /* Reclaim if clean, defer dirty pages to writeback */
733         if (referenced_page && !PageSwapBacked(page))
734                 return PAGEREF_RECLAIM_CLEAN;
735
736         return PAGEREF_RECLAIM;
737 }
738
739 static noinline_for_stack void free_page_list(struct list_head *free_pages)
740 {
741         struct pagevec freed_pvec;
742         struct page *page, *tmp;
743
744         pagevec_init(&freed_pvec, 1);
745
746         list_for_each_entry_safe(page, tmp, free_pages, lru) {
747                 list_del(&page->lru);
748                 if (!pagevec_add(&freed_pvec, page)) {
749                         __pagevec_free(&freed_pvec);
750                         pagevec_reinit(&freed_pvec);
751                 }
752         }
753
754         pagevec_free(&freed_pvec);
755 }
756
757 /*
758  * shrink_page_list() returns the number of reclaimed pages
759  */
760 static unsigned long shrink_page_list(struct list_head *page_list,
761                                       struct zone *zone,
762                                       struct scan_control *sc)
763 {
764         LIST_HEAD(ret_pages);
765         LIST_HEAD(free_pages);
766         int pgactivate = 0;
767         unsigned long nr_dirty = 0;
768         unsigned long nr_congested = 0;
769         unsigned long nr_reclaimed = 0;
770
771         cond_resched();
772
773         while (!list_empty(page_list)) {
774                 enum page_references references;
775                 struct address_space *mapping;
776                 struct page *page;
777                 int may_enter_fs;
778
779                 cond_resched();
780
781                 page = lru_to_page(page_list);
782                 list_del(&page->lru);
783
784                 if (!trylock_page(page))
785                         goto keep;
786
787                 VM_BUG_ON(PageActive(page));
788                 VM_BUG_ON(page_zone(page) != zone);
789
790                 sc->nr_scanned++;
791
792                 if (unlikely(!page_evictable(page, NULL)))
793                         goto cull_mlocked;
794
795                 if (!sc->may_unmap && page_mapped(page))
796                         goto keep_locked;
797
798                 /* Double the slab pressure for mapped and swapcache pages */
799                 if (page_mapped(page) || PageSwapCache(page))
800                         sc->nr_scanned++;
801
802                 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
803                         (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
804
805                 if (PageWriteback(page)) {
806                         /*
807                          * Synchronous reclaim is performed in two passes,
808                          * first an asynchronous pass over the list to
809                          * start parallel writeback, and a second synchronous
810                          * pass to wait for the IO to complete.  Wait here
811                          * for any page for which writeback has already
812                          * started.
813                          */
814                         if ((sc->reclaim_mode & RECLAIM_MODE_SYNC) &&
815                             may_enter_fs)
816                                 wait_on_page_writeback(page);
817                         else {
818                                 unlock_page(page);
819                                 goto keep_lumpy;
820                         }
821                 }
822
823                 references = page_check_references(page, sc);
824                 switch (references) {
825                 case PAGEREF_ACTIVATE:
826                         goto activate_locked;
827                 case PAGEREF_KEEP:
828                         goto keep_locked;
829                 case PAGEREF_RECLAIM:
830                 case PAGEREF_RECLAIM_CLEAN:
831                         ; /* try to reclaim the page below */
832                 }
833
834                 /*
835                  * Anonymous process memory has backing store?
836                  * Try to allocate it some swap space here.
837                  */
838                 if (PageAnon(page) && !PageSwapCache(page)) {
839                         if (!(sc->gfp_mask & __GFP_IO))
840                                 goto keep_locked;
841                         if (!add_to_swap(page))
842                                 goto activate_locked;
843                         may_enter_fs = 1;
844                 }
845
846                 mapping = page_mapping(page);
847
848                 /*
849                  * The page is mapped into the page tables of one or more
850                  * processes. Try to unmap it here.
851                  */
852                 if (page_mapped(page) && mapping) {
853                         switch (try_to_unmap(page, TTU_UNMAP)) {
854                         case SWAP_FAIL:
855                                 goto activate_locked;
856                         case SWAP_AGAIN:
857                                 goto keep_locked;
858                         case SWAP_MLOCK:
859                                 goto cull_mlocked;
860                         case SWAP_SUCCESS:
861                                 ; /* try to free the page below */
862                         }
863                 }
864
865                 if (PageDirty(page)) {
866                         nr_dirty++;
867
868                         if (references == PAGEREF_RECLAIM_CLEAN)
869                                 goto keep_locked;
870                         if (!may_enter_fs)
871                                 goto keep_locked;
872                         if (!sc->may_writepage)
873                                 goto keep_locked;
874
875                         /* Page is dirty, try to write it out here */
876                         switch (pageout(page, mapping, sc)) {
877                         case PAGE_KEEP:
878                                 nr_congested++;
879                                 goto keep_locked;
880                         case PAGE_ACTIVATE:
881                                 goto activate_locked;
882                         case PAGE_SUCCESS:
883                                 if (PageWriteback(page))
884                                         goto keep_lumpy;
885                                 if (PageDirty(page))
886                                         goto keep;
887
888                                 /*
889                                  * A synchronous write - probably a ramdisk.  Go
890                                  * ahead and try to reclaim the page.
891                                  */
892                                 if (!trylock_page(page))
893                                         goto keep;
894                                 if (PageDirty(page) || PageWriteback(page))
895                                         goto keep_locked;
896                                 mapping = page_mapping(page);
897                         case PAGE_CLEAN:
898                                 ; /* try to free the page below */
899                         }
900                 }
901
902                 /*
903                  * If the page has buffers, try to free the buffer mappings
904                  * associated with this page. If we succeed we try to free
905                  * the page as well.
906                  *
907                  * We do this even if the page is PageDirty().
908                  * try_to_release_page() does not perform I/O, but it is
909                  * possible for a page to have PageDirty set, but it is actually
910                  * clean (all its buffers are clean).  This happens if the
911                  * buffers were written out directly, with submit_bh(). ext3
912                  * will do this, as well as the blockdev mapping.
913                  * try_to_release_page() will discover that cleanness and will
914                  * drop the buffers and mark the page clean - it can be freed.
915                  *
916                  * Rarely, pages can have buffers and no ->mapping.  These are
917                  * the pages which were not successfully invalidated in
918                  * truncate_complete_page().  We try to drop those buffers here
919                  * and if that worked, and the page is no longer mapped into
920                  * process address space (page_count == 1) it can be freed.
921                  * Otherwise, leave the page on the LRU so it is swappable.
922                  */
923                 if (page_has_private(page)) {
924                         if (!try_to_release_page(page, sc->gfp_mask))
925                                 goto activate_locked;
926                         if (!mapping && page_count(page) == 1) {
927                                 unlock_page(page);
928                                 if (put_page_testzero(page))
929                                         goto free_it;
930                                 else {
931                                         /*
932                                          * rare race with speculative reference.
933                                          * the speculative reference will free
934                                          * this page shortly, so we may
935                                          * increment nr_reclaimed here (and
936                                          * leave it off the LRU).
937                                          */
938                                         nr_reclaimed++;
939                                         continue;
940                                 }
941                         }
942                 }
943
944                 if (!mapping || !__remove_mapping(mapping, page))
945                         goto keep_locked;
946
947                 /*
948                  * At this point, we have no other references and there is
949                  * no way to pick any more up (removed from LRU, removed
950                  * from pagecache). Can use non-atomic bitops now (and
951                  * we obviously don't have to worry about waking up a process
952                  * waiting on the page lock, because there are no references.
953                  */
954                 __clear_page_locked(page);
955 free_it:
956                 nr_reclaimed++;
957
958                 /*
959                  * Is there need to periodically free_page_list? It would
960                  * appear not as the counts should be low
961                  */
962                 list_add(&page->lru, &free_pages);
963                 continue;
964
965 cull_mlocked:
966                 if (PageSwapCache(page))
967                         try_to_free_swap(page);
968                 unlock_page(page);
969                 putback_lru_page(page);
970                 reset_reclaim_mode(sc);
971                 continue;
972
973 activate_locked:
974                 /* Not a candidate for swapping, so reclaim swap space. */
975                 if (PageSwapCache(page) && vm_swap_full())
976                         try_to_free_swap(page);
977                 VM_BUG_ON(PageActive(page));
978                 SetPageActive(page);
979                 pgactivate++;
980 keep_locked:
981                 unlock_page(page);
982 keep:
983                 reset_reclaim_mode(sc);
984 keep_lumpy:
985                 list_add(&page->lru, &ret_pages);
986                 VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
987         }
988
989         /*
990          * Tag a zone as congested if all the dirty pages encountered were
991          * backed by a congested BDI. In this case, reclaimers should just
992          * back off and wait for congestion to clear because further reclaim
993          * will encounter the same problem
994          */
995         if (nr_dirty && nr_dirty == nr_congested && scanning_global_lru(sc))
996                 zone_set_flag(zone, ZONE_CONGESTED);
997
998         free_page_list(&free_pages);
999
1000         list_splice(&ret_pages, page_list);
1001         count_vm_events(PGACTIVATE, pgactivate);
1002         return nr_reclaimed;
1003 }
1004
1005 /*
1006  * Attempt to remove the specified page from its LRU.  Only take this page
1007  * if it is of the appropriate PageActive status.  Pages which are being
1008  * freed elsewhere are also ignored.
1009  *
1010  * page:        page to consider
1011  * mode:        one of the LRU isolation modes defined above
1012  *
1013  * returns 0 on success, -ve errno on failure.
1014  */
1015 int __isolate_lru_page(struct page *page, int mode, int file)
1016 {
1017         int ret = -EINVAL;
1018
1019         /* Only take pages on the LRU. */
1020         if (!PageLRU(page))
1021                 return ret;
1022
1023         /*
1024          * When checking the active state, we need to be sure we are
1025          * dealing with comparible boolean values.  Take the logical not
1026          * of each.
1027          */
1028         if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode))
1029                 return ret;
1030
1031         if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file)
1032                 return ret;
1033
1034         /*
1035          * When this function is being called for lumpy reclaim, we
1036          * initially look into all LRU pages, active, inactive and
1037          * unevictable; only give shrink_page_list evictable pages.
1038          */
1039         if (PageUnevictable(page))
1040                 return ret;
1041
1042         ret = -EBUSY;
1043
1044         if (likely(get_page_unless_zero(page))) {
1045                 /*
1046                  * Be careful not to clear PageLRU until after we're
1047                  * sure the page is not being freed elsewhere -- the
1048                  * page release code relies on it.
1049                  */
1050                 ClearPageLRU(page);
1051                 ret = 0;
1052         }
1053
1054         return ret;
1055 }
1056
1057 /*
1058  * zone->lru_lock is heavily contended.  Some of the functions that
1059  * shrink the lists perform better by taking out a batch of pages
1060  * and working on them outside the LRU lock.
1061  *
1062  * For pagecache intensive workloads, this function is the hottest
1063  * spot in the kernel (apart from copy_*_user functions).
1064  *
1065  * Appropriate locks must be held before calling this function.
1066  *
1067  * @nr_to_scan: The number of pages to look through on the list.
1068  * @src:        The LRU list to pull pages off.
1069  * @dst:        The temp list to put pages on to.
1070  * @scanned:    The number of pages that were scanned.
1071  * @order:      The caller's attempted allocation order
1072  * @mode:       One of the LRU isolation modes
1073  * @file:       True [1] if isolating file [!anon] pages
1074  *
1075  * returns how many pages were moved onto *@dst.
1076  */
1077 static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
1078                 struct list_head *src, struct list_head *dst,
1079                 unsigned long *scanned, int order, int mode, int file)
1080 {
1081         unsigned long nr_taken = 0;
1082         unsigned long nr_lumpy_taken = 0;
1083         unsigned long nr_lumpy_dirty = 0;
1084         unsigned long nr_lumpy_failed = 0;
1085         unsigned long scan;
1086
1087         for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
1088                 struct page *page;
1089                 unsigned long pfn;
1090                 unsigned long end_pfn;
1091                 unsigned long page_pfn;
1092                 int zone_id;
1093
1094                 page = lru_to_page(src);
1095                 prefetchw_prev_lru_page(page, src, flags);
1096
1097                 VM_BUG_ON(!PageLRU(page));
1098
1099                 switch (__isolate_lru_page(page, mode, file)) {
1100                 case 0:
1101                         list_move(&page->lru, dst);
1102                         mem_cgroup_del_lru(page);
1103                         nr_taken += hpage_nr_pages(page);
1104                         break;
1105
1106                 case -EBUSY:
1107                         /* else it is being freed elsewhere */
1108                         list_move(&page->lru, src);
1109                         mem_cgroup_rotate_lru_list(page, page_lru(page));
1110                         continue;
1111
1112                 default:
1113                         BUG();
1114                 }
1115
1116                 if (!order)
1117                         continue;
1118
1119                 /*
1120                  * Attempt to take all pages in the order aligned region
1121                  * surrounding the tag page.  Only take those pages of
1122                  * the same active state as that tag page.  We may safely
1123                  * round the target page pfn down to the requested order
1124                  * as the mem_map is guaranteed valid out to MAX_ORDER,
1125                  * where that page is in a different zone we will detect
1126                  * it from its zone id and abort this block scan.
1127                  */
1128                 zone_id = page_zone_id(page);
1129                 page_pfn = page_to_pfn(page);
1130                 pfn = page_pfn & ~((1 << order) - 1);
1131                 end_pfn = pfn + (1 << order);
1132                 for (; pfn < end_pfn; pfn++) {
1133                         struct page *cursor_page;
1134
1135                         /* The target page is in the block, ignore it. */
1136                         if (unlikely(pfn == page_pfn))
1137                                 continue;
1138
1139                         /* Avoid holes within the zone. */
1140                         if (unlikely(!pfn_valid_within(pfn)))
1141                                 break;
1142
1143                         cursor_page = pfn_to_page(pfn);
1144
1145                         /* Check that we have not crossed a zone boundary. */
1146                         if (unlikely(page_zone_id(cursor_page) != zone_id))
1147                                 break;
1148
1149                         /*
1150                          * If we don't have enough swap space, reclaiming of
1151                          * anon page which don't already have a swap slot is
1152                          * pointless.
1153                          */
1154                         if (nr_swap_pages <= 0 && PageAnon(cursor_page) &&
1155                             !PageSwapCache(cursor_page))
1156                                 break;
1157
1158                         if (__isolate_lru_page(cursor_page, mode, file) == 0) {
1159                                 list_move(&cursor_page->lru, dst);
1160                                 mem_cgroup_del_lru(cursor_page);
1161                                 nr_taken += hpage_nr_pages(page);
1162                                 nr_lumpy_taken++;
1163                                 if (PageDirty(cursor_page))
1164                                         nr_lumpy_dirty++;
1165                                 scan++;
1166                         } else {
1167                                 /*
1168                                  * Check if the page is freed already.
1169                                  *
1170                                  * We can't use page_count() as that
1171                                  * requires compound_head and we don't
1172                                  * have a pin on the page here. If a
1173                                  * page is tail, we may or may not
1174                                  * have isolated the head, so assume
1175                                  * it's not free, it'd be tricky to
1176                                  * track the head status without a
1177                                  * page pin.
1178                                  */
1179                                 if (!PageTail(cursor_page) &&
1180                                     !atomic_read(&cursor_page->_count))
1181                                         continue;
1182                                 break;
1183                         }
1184                 }
1185
1186                 /* If we break out of the loop above, lumpy reclaim failed */
1187                 if (pfn < end_pfn)
1188                         nr_lumpy_failed++;
1189         }
1190
1191         *scanned = scan;
1192
1193         trace_mm_vmscan_lru_isolate(order,
1194                         nr_to_scan, scan,
1195                         nr_taken,
1196                         nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed,
1197                         mode);
1198         return nr_taken;
1199 }
1200
1201 static unsigned long isolate_pages_global(unsigned long nr,
1202                                         struct list_head *dst,
1203                                         unsigned long *scanned, int order,
1204                                         int mode, struct zone *z,
1205                                         int active, int file)
1206 {
1207         int lru = LRU_BASE;
1208         if (active)
1209                 lru += LRU_ACTIVE;
1210         if (file)
1211                 lru += LRU_FILE;
1212         return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
1213                                                                 mode, file);
1214 }
1215
1216 /*
1217  * clear_active_flags() is a helper for shrink_active_list(), clearing
1218  * any active bits from the pages in the list.
1219  */
1220 static unsigned long clear_active_flags(struct list_head *page_list,
1221                                         unsigned int *count)
1222 {
1223         int nr_active = 0;
1224         int lru;
1225         struct page *page;
1226
1227         list_for_each_entry(page, page_list, lru) {
1228                 int numpages = hpage_nr_pages(page);
1229                 lru = page_lru_base_type(page);
1230                 if (PageActive(page)) {
1231                         lru += LRU_ACTIVE;
1232                         ClearPageActive(page);
1233                         nr_active += numpages;
1234                 }
1235                 if (count)
1236                         count[lru] += numpages;
1237         }
1238
1239         return nr_active;
1240 }
1241
1242 /**
1243  * isolate_lru_page - tries to isolate a page from its LRU list
1244  * @page: page to isolate from its LRU list
1245  *
1246  * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1247  * vmstat statistic corresponding to whatever LRU list the page was on.
1248  *
1249  * Returns 0 if the page was removed from an LRU list.
1250  * Returns -EBUSY if the page was not on an LRU list.
1251  *
1252  * The returned page will have PageLRU() cleared.  If it was found on
1253  * the active list, it will have PageActive set.  If it was found on
1254  * the unevictable list, it will have the PageUnevictable bit set. That flag
1255  * may need to be cleared by the caller before letting the page go.
1256  *
1257  * The vmstat statistic corresponding to the list on which the page was
1258  * found will be decremented.
1259  *
1260  * Restrictions:
1261  * (1) Must be called with an elevated refcount on the page. This is a
1262  *     fundamentnal difference from isolate_lru_pages (which is called
1263  *     without a stable reference).
1264  * (2) the lru_lock must not be held.
1265  * (3) interrupts must be enabled.
1266  */
1267 int isolate_lru_page(struct page *page)
1268 {
1269         int ret = -EBUSY;
1270
1271         VM_BUG_ON(!page_count(page));
1272
1273         if (PageLRU(page)) {
1274                 struct zone *zone = page_zone(page);
1275
1276                 spin_lock_irq(&zone->lru_lock);
1277                 if (PageLRU(page)) {
1278                         int lru = page_lru(page);
1279                         ret = 0;
1280                         get_page(page);
1281                         ClearPageLRU(page);
1282
1283                         del_page_from_lru_list(zone, page, lru);
1284                 }
1285                 spin_unlock_irq(&zone->lru_lock);
1286         }
1287         return ret;
1288 }
1289
1290 /*
1291  * Are there way too many processes in the direct reclaim path already?
1292  */
1293 static int too_many_isolated(struct zone *zone, int file,
1294                 struct scan_control *sc)
1295 {
1296         unsigned long inactive, isolated;
1297
1298         if (current_is_kswapd())
1299                 return 0;
1300
1301         if (!scanning_global_lru(sc))
1302                 return 0;
1303
1304         if (file) {
1305                 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1306                 isolated = zone_page_state(zone, NR_ISOLATED_FILE);
1307         } else {
1308                 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1309                 isolated = zone_page_state(zone, NR_ISOLATED_ANON);
1310         }
1311
1312         return isolated > inactive;
1313 }
1314
1315 /*
1316  * TODO: Try merging with migrations version of putback_lru_pages
1317  */
1318 static noinline_for_stack void
1319 putback_lru_pages(struct zone *zone, struct scan_control *sc,
1320                                 unsigned long nr_anon, unsigned long nr_file,
1321                                 struct list_head *page_list)
1322 {
1323         struct page *page;
1324         struct pagevec pvec;
1325         struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1326
1327         pagevec_init(&pvec, 1);
1328
1329         /*
1330          * Put back any unfreeable pages.
1331          */
1332         spin_lock(&zone->lru_lock);
1333         while (!list_empty(page_list)) {
1334                 int lru;
1335                 page = lru_to_page(page_list);
1336                 VM_BUG_ON(PageLRU(page));
1337                 list_del(&page->lru);
1338                 if (unlikely(!page_evictable(page, NULL))) {
1339                         spin_unlock_irq(&zone->lru_lock);
1340                         putback_lru_page(page);
1341                         spin_lock_irq(&zone->lru_lock);
1342                         continue;
1343                 }
1344                 SetPageLRU(page);
1345                 lru = page_lru(page);
1346                 add_page_to_lru_list(zone, page, lru);
1347                 if (is_active_lru(lru)) {
1348                         int file = is_file_lru(lru);
1349                         int numpages = hpage_nr_pages(page);
1350                         reclaim_stat->recent_rotated[file] += numpages;
1351                 }
1352                 if (!pagevec_add(&pvec, page)) {
1353                         spin_unlock_irq(&zone->lru_lock);
1354                         __pagevec_release(&pvec);
1355                         spin_lock_irq(&zone->lru_lock);
1356                 }
1357         }
1358         __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
1359         __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
1360
1361         spin_unlock_irq(&zone->lru_lock);
1362         pagevec_release(&pvec);
1363 }
1364
1365 static noinline_for_stack void update_isolated_counts(struct zone *zone,
1366                                         struct scan_control *sc,
1367                                         unsigned long *nr_anon,
1368                                         unsigned long *nr_file,
1369                                         struct list_head *isolated_list)
1370 {
1371         unsigned long nr_active;
1372         unsigned int count[NR_LRU_LISTS] = { 0, };
1373         struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1374
1375         nr_active = clear_active_flags(isolated_list, count);
1376         __count_vm_events(PGDEACTIVATE, nr_active);
1377
1378         __mod_zone_page_state(zone, NR_ACTIVE_FILE,
1379                               -count[LRU_ACTIVE_FILE]);
1380         __mod_zone_page_state(zone, NR_INACTIVE_FILE,
1381                               -count[LRU_INACTIVE_FILE]);
1382         __mod_zone_page_state(zone, NR_ACTIVE_ANON,
1383                               -count[LRU_ACTIVE_ANON]);
1384         __mod_zone_page_state(zone, NR_INACTIVE_ANON,
1385                               -count[LRU_INACTIVE_ANON]);
1386
1387         *nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
1388         *nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
1389         __mod_zone_page_state(zone, NR_ISOLATED_ANON, *nr_anon);
1390         __mod_zone_page_state(zone, NR_ISOLATED_FILE, *nr_file);
1391
1392         reclaim_stat->recent_scanned[0] += *nr_anon;
1393         reclaim_stat->recent_scanned[1] += *nr_file;
1394 }
1395
1396 /*
1397  * Returns true if the caller should wait to clean dirty/writeback pages.
1398  *
1399  * If we are direct reclaiming for contiguous pages and we do not reclaim
1400  * everything in the list, try again and wait for writeback IO to complete.
1401  * This will stall high-order allocations noticeably. Only do that when really
1402  * need to free the pages under high memory pressure.
1403  */
1404 static inline bool should_reclaim_stall(unsigned long nr_taken,
1405                                         unsigned long nr_freed,
1406                                         int priority,
1407                                         struct scan_control *sc)
1408 {
1409         int lumpy_stall_priority;
1410
1411         /* kswapd should not stall on sync IO */
1412         if (current_is_kswapd())
1413                 return false;
1414
1415         /* Only stall on lumpy reclaim */
1416         if (sc->reclaim_mode & RECLAIM_MODE_SINGLE)
1417                 return false;
1418
1419         /* If we have relaimed everything on the isolated list, no stall */
1420         if (nr_freed == nr_taken)
1421                 return false;
1422
1423         /*
1424          * For high-order allocations, there are two stall thresholds.
1425          * High-cost allocations stall immediately where as lower
1426          * order allocations such as stacks require the scanning
1427          * priority to be much higher before stalling.
1428          */
1429         if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
1430                 lumpy_stall_priority = DEF_PRIORITY;
1431         else
1432                 lumpy_stall_priority = DEF_PRIORITY / 3;
1433
1434         return priority <= lumpy_stall_priority;
1435 }
1436
1437 /*
1438  * shrink_inactive_list() is a helper for shrink_zone().  It returns the number
1439  * of reclaimed pages
1440  */
1441 static noinline_for_stack unsigned long
1442 shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
1443                         struct scan_control *sc, int priority, int file)
1444 {
1445         LIST_HEAD(page_list);
1446         unsigned long nr_scanned;
1447         unsigned long nr_reclaimed = 0;
1448         unsigned long nr_taken;
1449         unsigned long nr_anon;
1450         unsigned long nr_file;
1451
1452         while (unlikely(too_many_isolated(zone, file, sc))) {
1453                 congestion_wait(BLK_RW_ASYNC, HZ/10);
1454
1455                 /* We are about to die and free our memory. Return now. */
1456                 if (fatal_signal_pending(current))
1457                         return SWAP_CLUSTER_MAX;
1458         }
1459
1460         set_reclaim_mode(priority, sc, false);
1461         lru_add_drain();
1462         spin_lock_irq(&zone->lru_lock);
1463
1464         if (scanning_global_lru(sc)) {
1465                 nr_taken = isolate_pages_global(nr_to_scan,
1466                         &page_list, &nr_scanned, sc->order,
1467                         sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ?
1468                                         ISOLATE_BOTH : ISOLATE_INACTIVE,
1469                         zone, 0, file);
1470                 zone->pages_scanned += nr_scanned;
1471                 if (current_is_kswapd())
1472                         __count_zone_vm_events(PGSCAN_KSWAPD, zone,
1473                                                nr_scanned);
1474                 else
1475                         __count_zone_vm_events(PGSCAN_DIRECT, zone,
1476                                                nr_scanned);
1477         } else {
1478                 nr_taken = mem_cgroup_isolate_pages(nr_to_scan,
1479                         &page_list, &nr_scanned, sc->order,
1480                         sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ?
1481                                         ISOLATE_BOTH : ISOLATE_INACTIVE,
1482                         zone, sc->mem_cgroup,
1483                         0, file);
1484                 /*
1485                  * mem_cgroup_isolate_pages() keeps track of
1486                  * scanned pages on its own.
1487                  */
1488         }
1489
1490         if (nr_taken == 0) {
1491                 spin_unlock_irq(&zone->lru_lock);
1492                 return 0;
1493         }
1494
1495         update_isolated_counts(zone, sc, &nr_anon, &nr_file, &page_list);
1496
1497         spin_unlock_irq(&zone->lru_lock);
1498
1499         nr_reclaimed = shrink_page_list(&page_list, zone, sc);
1500
1501         /* Check if we should syncronously wait for writeback */
1502         if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) {
1503                 set_reclaim_mode(priority, sc, true);
1504                 nr_reclaimed += shrink_page_list(&page_list, zone, sc);
1505         }
1506
1507         local_irq_disable();
1508         if (current_is_kswapd())
1509                 __count_vm_events(KSWAPD_STEAL, nr_reclaimed);
1510         __count_zone_vm_events(PGSTEAL, zone, nr_reclaimed);
1511
1512         putback_lru_pages(zone, sc, nr_anon, nr_file, &page_list);
1513
1514         trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id,
1515                 zone_idx(zone),
1516                 nr_scanned, nr_reclaimed,
1517                 priority,
1518                 trace_shrink_flags(file, sc->reclaim_mode));
1519         return nr_reclaimed;
1520 }
1521
1522 /*
1523  * This moves pages from the active list to the inactive list.
1524  *
1525  * We move them the other way if the page is referenced by one or more
1526  * processes, from rmap.
1527  *
1528  * If the pages are mostly unmapped, the processing is fast and it is
1529  * appropriate to hold zone->lru_lock across the whole operation.  But if
1530  * the pages are mapped, the processing is slow (page_referenced()) so we
1531  * should drop zone->lru_lock around each page.  It's impossible to balance
1532  * this, so instead we remove the pages from the LRU while processing them.
1533  * It is safe to rely on PG_active against the non-LRU pages in here because
1534  * nobody will play with that bit on a non-LRU page.
1535  *
1536  * The downside is that we have to touch page->_count against each page.
1537  * But we had to alter page->flags anyway.
1538  */
1539
1540 static void move_active_pages_to_lru(struct zone *zone,
1541                                      struct list_head *list,
1542                                      enum lru_list lru)
1543 {
1544         unsigned long pgmoved = 0;
1545         struct pagevec pvec;
1546         struct page *page;
1547
1548         pagevec_init(&pvec, 1);
1549
1550         while (!list_empty(list)) {
1551                 page = lru_to_page(list);
1552
1553                 VM_BUG_ON(PageLRU(page));
1554                 SetPageLRU(page);
1555
1556                 list_move(&page->lru, &zone->lru[lru].list);
1557                 mem_cgroup_add_lru_list(page, lru);
1558                 pgmoved += hpage_nr_pages(page);
1559
1560                 if (!pagevec_add(&pvec, page) || list_empty(list)) {
1561                         spin_unlock_irq(&zone->lru_lock);
1562                         if (buffer_heads_over_limit)
1563                                 pagevec_strip(&pvec);
1564                         __pagevec_release(&pvec);
1565                         spin_lock_irq(&zone->lru_lock);
1566                 }
1567         }
1568         __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1569         if (!is_active_lru(lru))
1570                 __count_vm_events(PGDEACTIVATE, pgmoved);
1571 }
1572
1573 static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1574                         struct scan_control *sc, int priority, int file)
1575 {
1576         unsigned long nr_taken;
1577         unsigned long pgscanned;
1578         unsigned long vm_flags;
1579         LIST_HEAD(l_hold);      /* The pages which were snipped off */
1580         LIST_HEAD(l_active);
1581         LIST_HEAD(l_inactive);
1582         struct page *page;
1583         struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1584         unsigned long nr_rotated = 0;
1585
1586         lru_add_drain();
1587         spin_lock_irq(&zone->lru_lock);
1588         if (scanning_global_lru(sc)) {
1589                 nr_taken = isolate_pages_global(nr_pages, &l_hold,
1590                                                 &pgscanned, sc->order,
1591                                                 ISOLATE_ACTIVE, zone,
1592                                                 1, file);
1593                 zone->pages_scanned += pgscanned;
1594         } else {
1595                 nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold,
1596                                                 &pgscanned, sc->order,
1597                                                 ISOLATE_ACTIVE, zone,
1598                                                 sc->mem_cgroup, 1, file);
1599                 /*
1600                  * mem_cgroup_isolate_pages() keeps track of
1601                  * scanned pages on its own.
1602                  */
1603         }
1604
1605         reclaim_stat->recent_scanned[file] += nr_taken;
1606
1607         __count_zone_vm_events(PGREFILL, zone, pgscanned);
1608         if (file)
1609                 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken);
1610         else
1611                 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken);
1612         __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
1613         spin_unlock_irq(&zone->lru_lock);
1614
1615         while (!list_empty(&l_hold)) {
1616                 cond_resched();
1617                 page = lru_to_page(&l_hold);
1618                 list_del(&page->lru);
1619
1620                 if (unlikely(!page_evictable(page, NULL))) {
1621                         putback_lru_page(page);
1622                         continue;
1623                 }
1624
1625                 if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) {
1626                         nr_rotated += hpage_nr_pages(page);
1627                         /*
1628                          * Identify referenced, file-backed active pages and
1629                          * give them one more trip around the active list. So
1630                          * that executable code get better chances to stay in
1631                          * memory under moderate memory pressure.  Anon pages
1632                          * are not likely to be evicted by use-once streaming
1633                          * IO, plus JVM can create lots of anon VM_EXEC pages,
1634                          * so we ignore them here.
1635                          */
1636                         if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
1637                                 list_add(&page->lru, &l_active);
1638                                 continue;
1639                         }
1640                 }
1641
1642                 ClearPageActive(page);  /* we are de-activating */
1643                 list_add(&page->lru, &l_inactive);
1644         }
1645
1646         /*
1647          * Move pages back to the lru list.
1648          */
1649         spin_lock_irq(&zone->lru_lock);
1650         /*
1651          * Count referenced pages from currently used mappings as rotated,
1652          * even though only some of them are actually re-activated.  This
1653          * helps balance scan pressure between file and anonymous pages in
1654          * get_scan_ratio.
1655          */
1656         reclaim_stat->recent_rotated[file] += nr_rotated;
1657
1658         move_active_pages_to_lru(zone, &l_active,
1659                                                 LRU_ACTIVE + file * LRU_FILE);
1660         move_active_pages_to_lru(zone, &l_inactive,
1661                                                 LRU_BASE   + file * LRU_FILE);
1662         __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1663         spin_unlock_irq(&zone->lru_lock);
1664 }
1665
1666 #ifdef CONFIG_SWAP
1667 static int inactive_anon_is_low_global(struct zone *zone)
1668 {
1669         unsigned long active, inactive;
1670
1671         active = zone_page_state(zone, NR_ACTIVE_ANON);
1672         inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1673
1674         if (inactive * zone->inactive_ratio < active)
1675                 return 1;
1676
1677         return 0;
1678 }
1679
1680 /**
1681  * inactive_anon_is_low - check if anonymous pages need to be deactivated
1682  * @zone: zone to check
1683  * @sc:   scan control of this context
1684  *
1685  * Returns true if the zone does not have enough inactive anon pages,
1686  * meaning some active anon pages need to be deactivated.
1687  */
1688 static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc)
1689 {
1690         int low;
1691
1692         /*
1693          * If we don't have swap space, anonymous page deactivation
1694          * is pointless.
1695          */
1696         if (!total_swap_pages)
1697                 return 0;
1698
1699         if (scanning_global_lru(sc))
1700                 low = inactive_anon_is_low_global(zone);
1701         else
1702                 low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup);
1703         return low;
1704 }
1705 #else
1706 static inline int inactive_anon_is_low(struct zone *zone,
1707                                         struct scan_control *sc)
1708 {
1709         return 0;
1710 }
1711 #endif
1712
1713 static int inactive_file_is_low_global(struct zone *zone)
1714 {
1715         unsigned long active, inactive;
1716
1717         active = zone_page_state(zone, NR_ACTIVE_FILE);
1718         inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1719
1720         return (active > inactive);
1721 }
1722
1723 /**
1724  * inactive_file_is_low - check if file pages need to be deactivated
1725  * @zone: zone to check
1726  * @sc:   scan control of this context
1727  *
1728  * When the system is doing streaming IO, memory pressure here
1729  * ensures that active file pages get deactivated, until more
1730  * than half of the file pages are on the inactive list.
1731  *
1732  * Once we get to that situation, protect the system's working
1733  * set from being evicted by disabling active file page aging.
1734  *
1735  * This uses a different ratio than the anonymous pages, because
1736  * the page cache uses a use-once replacement algorithm.
1737  */
1738 static int inactive_file_is_low(struct zone *zone, struct scan_control *sc)
1739 {
1740         int low;
1741
1742         if (scanning_global_lru(sc))
1743                 low = inactive_file_is_low_global(zone);
1744         else
1745                 low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup);
1746         return low;
1747 }
1748
1749 static int inactive_list_is_low(struct zone *zone, struct scan_control *sc,
1750                                 int file)
1751 {
1752         if (file)
1753                 return inactive_file_is_low(zone, sc);
1754         else
1755                 return inactive_anon_is_low(zone, sc);
1756 }
1757
1758 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1759         struct zone *zone, struct scan_control *sc, int priority)
1760 {
1761         int file = is_file_lru(lru);
1762
1763         if (is_active_lru(lru)) {
1764                 if (inactive_list_is_low(zone, sc, file))
1765                     shrink_active_list(nr_to_scan, zone, sc, priority, file);
1766                 return 0;
1767         }
1768
1769         return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1770 }
1771
1772 static int vmscan_swappiness(struct scan_control *sc)
1773 {
1774         if (scanning_global_lru(sc))
1775                 return vm_swappiness;
1776         return mem_cgroup_swappiness(sc->mem_cgroup);
1777 }
1778
1779 /*
1780  * Determine how aggressively the anon and file LRU lists should be
1781  * scanned.  The relative value of each set of LRU lists is determined
1782  * by looking at the fraction of the pages scanned we did rotate back
1783  * onto the active list instead of evict.
1784  *
1785  * nr[0] = anon pages to scan; nr[1] = file pages to scan
1786  */
1787 static void get_scan_count(struct zone *zone, struct scan_control *sc,
1788                                         unsigned long *nr, int priority)
1789 {
1790         unsigned long anon, file, free;
1791         unsigned long anon_prio, file_prio;
1792         unsigned long ap, fp;
1793         struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1794         u64 fraction[2], denominator;
1795         enum lru_list l;
1796         int noswap = 0;
1797         bool force_scan = false;
1798         unsigned long nr_force_scan[2];
1799
1800         /* kswapd does zone balancing and needs to scan this zone */
1801         if (scanning_global_lru(sc) && current_is_kswapd())
1802                 force_scan = true;
1803         /* memcg may have small limit and need to avoid priority drop */
1804         if (!scanning_global_lru(sc))
1805                 force_scan = true;
1806
1807         /* If we have no swap space, do not bother scanning anon pages. */
1808         if (!sc->may_swap || (nr_swap_pages <= 0)) {
1809                 noswap = 1;
1810                 fraction[0] = 0;
1811                 fraction[1] = 1;
1812                 denominator = 1;
1813                 nr_force_scan[0] = 0;
1814                 nr_force_scan[1] = SWAP_CLUSTER_MAX;
1815                 goto out;
1816         }
1817
1818         anon  = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) +
1819                 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON);
1820         file  = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) +
1821                 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
1822
1823         if (scanning_global_lru(sc)) {
1824                 free  = zone_page_state(zone, NR_FREE_PAGES);
1825                 /* If we have very few page cache pages,
1826                    force-scan anon pages. */
1827                 if (unlikely(file + free <= high_wmark_pages(zone))) {
1828                         fraction[0] = 1;
1829                         fraction[1] = 0;
1830                         denominator = 1;
1831                         nr_force_scan[0] = SWAP_CLUSTER_MAX;
1832                         nr_force_scan[1] = 0;
1833                         goto out;
1834                 }
1835         }
1836
1837         /*
1838          * With swappiness at 100, anonymous and file have the same priority.
1839          * This scanning priority is essentially the inverse of IO cost.
1840          */
1841         anon_prio = vmscan_swappiness(sc);
1842         file_prio = 200 - vmscan_swappiness(sc);
1843
1844         /*
1845          * OK, so we have swap space and a fair amount of page cache
1846          * pages.  We use the recently rotated / recently scanned
1847          * ratios to determine how valuable each cache is.
1848          *
1849          * Because workloads change over time (and to avoid overflow)
1850          * we keep these statistics as a floating average, which ends
1851          * up weighing recent references more than old ones.
1852          *
1853          * anon in [0], file in [1]
1854          */
1855         spin_lock_irq(&zone->lru_lock);
1856         if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
1857                 reclaim_stat->recent_scanned[0] /= 2;
1858                 reclaim_stat->recent_rotated[0] /= 2;
1859         }
1860
1861         if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
1862                 reclaim_stat->recent_scanned[1] /= 2;
1863                 reclaim_stat->recent_rotated[1] /= 2;
1864         }
1865
1866         /*
1867          * The amount of pressure on anon vs file pages is inversely
1868          * proportional to the fraction of recently scanned pages on
1869          * each list that were recently referenced and in active use.
1870          */
1871         ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
1872         ap /= reclaim_stat->recent_rotated[0] + 1;
1873
1874         fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
1875         fp /= reclaim_stat->recent_rotated[1] + 1;
1876         spin_unlock_irq(&zone->lru_lock);
1877
1878         fraction[0] = ap;
1879         fraction[1] = fp;
1880         denominator = ap + fp + 1;
1881         if (force_scan) {
1882                 unsigned long scan = SWAP_CLUSTER_MAX;
1883                 nr_force_scan[0] = div64_u64(scan * ap, denominator);
1884                 nr_force_scan[1] = div64_u64(scan * fp, denominator);
1885         }
1886 out:
1887         for_each_evictable_lru(l) {
1888                 int file = is_file_lru(l);
1889                 unsigned long scan;
1890
1891                 scan = zone_nr_lru_pages(zone, sc, l);
1892                 if (priority || noswap) {
1893                         scan >>= priority;
1894                         scan = div64_u64(scan * fraction[file], denominator);
1895                 }
1896
1897                 /*
1898                  * If zone is small or memcg is small, nr[l] can be 0.
1899                  * This results no-scan on this priority and priority drop down.
1900                  * For global direct reclaim, it can visit next zone and tend
1901                  * not to have problems. For global kswapd, it's for zone
1902                  * balancing and it need to scan a small amounts. When using
1903                  * memcg, priority drop can cause big latency. So, it's better
1904                  * to scan small amount. See may_noscan above.
1905                  */
1906                 if (!scan && force_scan)
1907                         scan = nr_force_scan[file];
1908                 nr[l] = scan;
1909         }
1910 }
1911
1912 /*
1913  * Reclaim/compaction depends on a number of pages being freed. To avoid
1914  * disruption to the system, a small number of order-0 pages continue to be
1915  * rotated and reclaimed in the normal fashion. However, by the time we get
1916  * back to the allocator and call try_to_compact_zone(), we ensure that
1917  * there are enough free pages for it to be likely successful
1918  */
1919 static inline bool should_continue_reclaim(struct zone *zone,
1920                                         unsigned long nr_reclaimed,
1921                                         unsigned long nr_scanned,
1922                                         struct scan_control *sc)
1923 {
1924         unsigned long pages_for_compaction;
1925         unsigned long inactive_lru_pages;
1926
1927         /* If not in reclaim/compaction mode, stop */
1928         if (!(sc->reclaim_mode & RECLAIM_MODE_COMPACTION))
1929                 return false;
1930
1931         /* Consider stopping depending on scan and reclaim activity */
1932         if (sc->gfp_mask & __GFP_REPEAT) {
1933                 /*
1934                  * For __GFP_REPEAT allocations, stop reclaiming if the
1935                  * full LRU list has been scanned and we are still failing
1936                  * to reclaim pages. This full LRU scan is potentially
1937                  * expensive but a __GFP_REPEAT caller really wants to succeed
1938                  */
1939                 if (!nr_reclaimed && !nr_scanned)
1940                         return false;
1941         } else {
1942                 /*
1943                  * For non-__GFP_REPEAT allocations which can presumably
1944                  * fail without consequence, stop if we failed to reclaim
1945                  * any pages from the last SWAP_CLUSTER_MAX number of
1946                  * pages that were scanned. This will return to the
1947                  * caller faster at the risk reclaim/compaction and
1948                  * the resulting allocation attempt fails
1949                  */
1950                 if (!nr_reclaimed)
1951                         return false;
1952         }
1953
1954         /*
1955          * If we have not reclaimed enough pages for compaction and the
1956          * inactive lists are large enough, continue reclaiming
1957          */
1958         pages_for_compaction = (2UL << sc->order);
1959         inactive_lru_pages = zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON) +
1960                                 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
1961         if (sc->nr_reclaimed < pages_for_compaction &&
1962                         inactive_lru_pages > pages_for_compaction)
1963                 return true;
1964
1965         /* If compaction would go ahead or the allocation would succeed, stop */
1966         switch (compaction_suitable(zone, sc->order)) {
1967         case COMPACT_PARTIAL:
1968         case COMPACT_CONTINUE:
1969                 return false;
1970         default:
1971                 return true;
1972         }
1973 }
1974
1975 /*
1976  * This is a basic per-zone page freer.  Used by both kswapd and direct reclaim.
1977  */
1978 static void shrink_zone(int priority, struct zone *zone,
1979                                 struct scan_control *sc)
1980 {
1981         unsigned long nr[NR_LRU_LISTS];
1982         unsigned long nr_to_scan;
1983         enum lru_list l;
1984         unsigned long nr_reclaimed, nr_scanned;
1985         unsigned long nr_to_reclaim = sc->nr_to_reclaim;
1986
1987 restart:
1988         nr_reclaimed = 0;
1989         nr_scanned = sc->nr_scanned;
1990         get_scan_count(zone, sc, nr, priority);
1991
1992         while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
1993                                         nr[LRU_INACTIVE_FILE]) {
1994                 for_each_evictable_lru(l) {
1995                         if (nr[l]) {
1996                                 nr_to_scan = min_t(unsigned long,
1997                                                    nr[l], SWAP_CLUSTER_MAX);
1998                                 nr[l] -= nr_to_scan;
1999
2000                                 nr_reclaimed += shrink_list(l, nr_to_scan,
2001                                                             zone, sc, priority);
2002                         }
2003                 }
2004                 /*
2005                  * On large memory systems, scan >> priority can become
2006                  * really large. This is fine for the starting priority;
2007                  * we want to put equal scanning pressure on each zone.
2008                  * However, if the VM has a harder time of freeing pages,
2009                  * with multiple processes reclaiming pages, the total
2010                  * freeing target can get unreasonably large.
2011                  */
2012                 if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY)
2013                         break;
2014         }
2015         sc->nr_reclaimed += nr_reclaimed;
2016
2017         /*
2018          * Even if we did not try to evict anon pages at all, we want to
2019          * rebalance the anon lru active/inactive ratio.
2020          */
2021         if (inactive_anon_is_low(zone, sc))
2022                 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
2023
2024         /* reclaim/compaction might need reclaim to continue */
2025         if (should_continue_reclaim(zone, nr_reclaimed,
2026                                         sc->nr_scanned - nr_scanned, sc))
2027                 goto restart;
2028
2029         throttle_vm_writeout(sc->gfp_mask);
2030 }
2031
2032 /*
2033  * This is the direct reclaim path, for page-allocating processes.  We only
2034  * try to reclaim pages from zones which will satisfy the caller's allocation
2035  * request.
2036  *
2037  * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
2038  * Because:
2039  * a) The caller may be trying to free *extra* pages to satisfy a higher-order
2040  *    allocation or
2041  * b) The target zone may be at high_wmark_pages(zone) but the lower zones
2042  *    must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
2043  *    zone defense algorithm.
2044  *
2045  * If a zone is deemed to be full of pinned pages then just give it a light
2046  * scan then give up on it.
2047  */
2048 static void shrink_zones(int priority, struct zonelist *zonelist,
2049                                         struct scan_control *sc)
2050 {
2051         struct zoneref *z;
2052         struct zone *zone;
2053         unsigned long nr_soft_reclaimed;
2054         unsigned long nr_soft_scanned;
2055
2056         for_each_zone_zonelist_nodemask(zone, z, zonelist,
2057                                         gfp_zone(sc->gfp_mask), sc->nodemask) {
2058                 if (!populated_zone(zone))
2059                         continue;
2060                 /*
2061                  * Take care memory controller reclaiming has small influence
2062                  * to global LRU.
2063                  */
2064                 if (scanning_global_lru(sc)) {
2065                         if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2066                                 continue;
2067                         if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2068                                 continue;       /* Let kswapd poll it */
2069                         /*
2070                          * This steals pages from memory cgroups over softlimit
2071                          * and returns the number of reclaimed pages and
2072                          * scanned pages. This works for global memory pressure
2073                          * and balancing, not for a memcg's limit.
2074                          */
2075                         nr_soft_scanned = 0;
2076                         nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
2077                                                 sc->order, sc->gfp_mask,
2078                                                 &nr_soft_scanned);
2079                         sc->nr_reclaimed += nr_soft_reclaimed;
2080                         sc->nr_scanned += nr_soft_scanned;
2081                         /* need some check for avoid more shrink_zone() */
2082                 }
2083
2084                 shrink_zone(priority, zone, sc);
2085         }
2086 }
2087
2088 static bool zone_reclaimable(struct zone *zone)
2089 {
2090         return zone->pages_scanned < zone_reclaimable_pages(zone) * 6;
2091 }
2092
2093 /* All zones in zonelist are unreclaimable? */
2094 static bool all_unreclaimable(struct zonelist *zonelist,
2095                 struct scan_control *sc)
2096 {
2097         struct zoneref *z;
2098         struct zone *zone;
2099
2100         for_each_zone_zonelist_nodemask(zone, z, zonelist,
2101                         gfp_zone(sc->gfp_mask), sc->nodemask) {
2102                 if (!populated_zone(zone))
2103                         continue;
2104                 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2105                         continue;
2106                 if (!zone->all_unreclaimable)
2107                         return false;
2108         }
2109
2110         return true;
2111 }
2112
2113 /*
2114  * This is the main entry point to direct page reclaim.
2115  *
2116  * If a full scan of the inactive list fails to free enough memory then we
2117  * are "out of memory" and something needs to be killed.
2118  *
2119  * If the caller is !__GFP_FS then the probability of a failure is reasonably
2120  * high - the zone may be full of dirty or under-writeback pages, which this
2121  * caller can't do much about.  We kick the writeback threads and take explicit
2122  * naps in the hope that some of these pages can be written.  But if the
2123  * allocating task holds filesystem locks which prevent writeout this might not
2124  * work, and the allocation attempt will fail.
2125  *
2126  * returns:     0, if no pages reclaimed
2127  *              else, the number of pages reclaimed
2128  */
2129 static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
2130                                         struct scan_control *sc,
2131                                         struct shrink_control *shrink)
2132 {
2133         int priority;
2134         unsigned long total_scanned = 0;
2135         struct reclaim_state *reclaim_state = current->reclaim_state;
2136         struct zoneref *z;
2137         struct zone *zone;
2138         unsigned long writeback_threshold;
2139
2140         get_mems_allowed();
2141         delayacct_freepages_start();
2142
2143         if (scanning_global_lru(sc))
2144                 count_vm_event(ALLOCSTALL);
2145
2146         for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2147                 sc->nr_scanned = 0;
2148                 if (!priority)
2149                         disable_swap_token(sc->mem_cgroup);
2150                 shrink_zones(priority, zonelist, sc);
2151                 /*
2152                  * Don't shrink slabs when reclaiming memory from
2153                  * over limit cgroups
2154                  */
2155                 if (scanning_global_lru(sc)) {
2156                         unsigned long lru_pages = 0;
2157                         for_each_zone_zonelist(zone, z, zonelist,
2158                                         gfp_zone(sc->gfp_mask)) {
2159                                 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2160                                         continue;
2161
2162                                 lru_pages += zone_reclaimable_pages(zone);
2163                         }
2164
2165                         shrink_slab(shrink, sc->nr_scanned, lru_pages);
2166                         if (reclaim_state) {
2167                                 sc->nr_reclaimed += reclaim_state->reclaimed_slab;
2168                                 reclaim_state->reclaimed_slab = 0;
2169                         }
2170                 }
2171                 total_scanned += sc->nr_scanned;
2172                 if (sc->nr_reclaimed >= sc->nr_to_reclaim)
2173                         goto out;
2174
2175                 /*
2176                  * Try to write back as many pages as we just scanned.  This
2177                  * tends to cause slow streaming writers to write data to the
2178                  * disk smoothly, at the dirtying rate, which is nice.   But
2179                  * that's undesirable in laptop mode, where we *want* lumpy
2180                  * writeout.  So in laptop mode, write out the whole world.
2181                  */
2182                 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
2183                 if (total_scanned > writeback_threshold) {
2184                         wakeup_flusher_threads(laptop_mode ? 0 : total_scanned);
2185                         sc->may_writepage = 1;
2186                 }
2187
2188                 /* Take a nap, wait for some writeback to complete */
2189                 if (!sc->hibernation_mode && sc->nr_scanned &&
2190                     priority < DEF_PRIORITY - 2) {
2191                         struct zone *preferred_zone;
2192
2193                         first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask),
2194                                                 &cpuset_current_mems_allowed,
2195                                                 &preferred_zone);
2196                         wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10);
2197                 }
2198         }
2199
2200 out:
2201         delayacct_freepages_end();
2202         put_mems_allowed();
2203
2204         if (sc->nr_reclaimed)
2205                 return sc->nr_reclaimed;
2206
2207         /*
2208          * As hibernation is going on, kswapd is freezed so that it can't mark
2209          * the zone into all_unreclaimable. Thus bypassing all_unreclaimable
2210          * check.
2211          */
2212         if (oom_killer_disabled)
2213                 return 0;
2214
2215         /* top priority shrink_zones still had more to do? don't OOM, then */
2216         if (scanning_global_lru(sc) && !all_unreclaimable(zonelist, sc))
2217                 return 1;
2218
2219         return 0;
2220 }
2221
2222 unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
2223                                 gfp_t gfp_mask, nodemask_t *nodemask)
2224 {
2225         unsigned long nr_reclaimed;
2226         struct scan_control sc = {
2227                 .gfp_mask = gfp_mask,
2228                 .may_writepage = !laptop_mode,
2229                 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2230                 .may_unmap = 1,
2231                 .may_swap = 1,
2232                 .order = order,
2233                 .mem_cgroup = NULL,
2234                 .nodemask = nodemask,
2235         };
2236         struct shrink_control shrink = {
2237                 .gfp_mask = sc.gfp_mask,
2238         };
2239
2240         trace_mm_vmscan_direct_reclaim_begin(order,
2241                                 sc.may_writepage,
2242                                 gfp_mask);
2243
2244         nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2245
2246         trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
2247
2248         return nr_reclaimed;
2249 }
2250
2251 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
2252
2253 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
2254                                                 gfp_t gfp_mask, bool noswap,
2255                                                 struct zone *zone,
2256                                                 unsigned long *nr_scanned)
2257 {
2258         struct scan_control sc = {
2259                 .nr_scanned = 0,
2260                 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2261                 .may_writepage = !laptop_mode,
2262                 .may_unmap = 1,
2263                 .may_swap = !noswap,
2264                 .order = 0,
2265                 .mem_cgroup = mem,
2266         };
2267
2268         sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2269                         (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
2270
2271         trace_mm_vmscan_memcg_softlimit_reclaim_begin(0,
2272                                                       sc.may_writepage,
2273                                                       sc.gfp_mask);
2274
2275         /*
2276          * NOTE: Although we can get the priority field, using it
2277          * here is not a good idea, since it limits the pages we can scan.
2278          * if we don't reclaim here, the shrink_zone from balance_pgdat
2279          * will pick up pages from other mem cgroup's as well. We hack
2280          * the priority and make it zero.
2281          */
2282         shrink_zone(0, zone, &sc);
2283
2284         trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
2285
2286         *nr_scanned = sc.nr_scanned;
2287         return sc.nr_reclaimed;
2288 }
2289
2290 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
2291                                            gfp_t gfp_mask,
2292                                            bool noswap)
2293 {
2294         struct zonelist *zonelist;
2295         unsigned long nr_reclaimed;
2296         int nid;
2297         struct scan_control sc = {
2298                 .may_writepage = !laptop_mode,
2299                 .may_unmap = 1,
2300                 .may_swap = !noswap,
2301                 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2302                 .order = 0,
2303                 .mem_cgroup = mem_cont,
2304                 .nodemask = NULL, /* we don't care the placement */
2305                 .gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2306                                 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
2307         };
2308         struct shrink_control shrink = {
2309                 .gfp_mask = sc.gfp_mask,
2310         };
2311
2312         /*
2313          * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
2314          * take care of from where we get pages. So the node where we start the
2315          * scan does not need to be the current node.
2316          */
2317         nid = mem_cgroup_select_victim_node(mem_cont);
2318
2319         zonelist = NODE_DATA(nid)->node_zonelists;
2320
2321         trace_mm_vmscan_memcg_reclaim_begin(0,
2322                                             sc.may_writepage,
2323                                             sc.gfp_mask);
2324
2325         nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2326
2327         trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
2328
2329         return nr_reclaimed;
2330 }
2331 #endif
2332
2333 /*
2334  * pgdat_balanced is used when checking if a node is balanced for high-order
2335  * allocations. Only zones that meet watermarks and are in a zone allowed
2336  * by the callers classzone_idx are added to balanced_pages. The total of
2337  * balanced pages must be at least 25% of the zones allowed by classzone_idx
2338  * for the node to be considered balanced. Forcing all zones to be balanced
2339  * for high orders can cause excessive reclaim when there are imbalanced zones.
2340  * The choice of 25% is due to
2341  *   o a 16M DMA zone that is balanced will not balance a zone on any
2342  *     reasonable sized machine
2343  *   o On all other machines, the top zone must be at least a reasonable
2344  *     percentage of the middle zones. For example, on 32-bit x86, highmem
2345  *     would need to be at least 256M for it to be balance a whole node.
2346  *     Similarly, on x86-64 the Normal zone would need to be at least 1G
2347  *     to balance a node on its own. These seemed like reasonable ratios.
2348  */
2349 static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages,
2350                                                 int classzone_idx)
2351 {
2352         unsigned long present_pages = 0;
2353         int i;
2354
2355         for (i = 0; i <= classzone_idx; i++)
2356                 present_pages += pgdat->node_zones[i].present_pages;
2357
2358         /* A special case here: if zone has no page, we think it's balanced */
2359         return balanced_pages >= (present_pages >> 2);
2360 }
2361
2362 /* is kswapd sleeping prematurely? */
2363 static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining,
2364                                         int classzone_idx)
2365 {
2366         int i;
2367         unsigned long balanced = 0;
2368         bool all_zones_ok = true;
2369
2370         /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
2371         if (remaining)
2372                 return true;
2373
2374         /* Check the watermark levels */
2375         for (i = 0; i <= classzone_idx; i++) {
2376                 struct zone *zone = pgdat->node_zones + i;
2377
2378                 if (!populated_zone(zone))
2379                         continue;
2380
2381                 /*
2382                  * balance_pgdat() skips over all_unreclaimable after
2383                  * DEF_PRIORITY. Effectively, it considers them balanced so
2384                  * they must be considered balanced here as well if kswapd
2385                  * is to sleep
2386                  */
2387                 if (zone->all_unreclaimable) {
2388                         balanced += zone->present_pages;
2389                         continue;
2390                 }
2391
2392                 if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone),
2393                                                         i, 0))
2394                         all_zones_ok = false;
2395                 else
2396                         balanced += zone->present_pages;
2397         }
2398
2399         /*
2400          * For high-order requests, the balanced zones must contain at least
2401          * 25% of the nodes pages for kswapd to sleep. For order-0, all zones
2402          * must be balanced
2403          */
2404         if (order)
2405                 return !pgdat_balanced(pgdat, balanced, classzone_idx);
2406         else
2407                 return !all_zones_ok;
2408 }
2409
2410 /*
2411  * For kswapd, balance_pgdat() will work across all this node's zones until
2412  * they are all at high_wmark_pages(zone).
2413  *
2414  * Returns the final order kswapd was reclaiming at
2415  *
2416  * There is special handling here for zones which are full of pinned pages.
2417  * This can happen if the pages are all mlocked, or if they are all used by
2418  * device drivers (say, ZONE_DMA).  Or if they are all in use by hugetlb.
2419  * What we do is to detect the case where all pages in the zone have been
2420  * scanned twice and there has been zero successful reclaim.  Mark the zone as
2421  * dead and from now on, only perform a short scan.  Basically we're polling
2422  * the zone for when the problem goes away.
2423  *
2424  * kswapd scans the zones in the highmem->normal->dma direction.  It skips
2425  * zones which have free_pages > high_wmark_pages(zone), but once a zone is
2426  * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
2427  * lower zones regardless of the number of free pages in the lower zones. This
2428  * interoperates with the page allocator fallback scheme to ensure that aging
2429  * of pages is balanced across the zones.
2430  */
2431 static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
2432                                                         int *classzone_idx)
2433 {
2434         int all_zones_ok;
2435         unsigned long balanced;
2436         int priority;
2437         int i;
2438         int end_zone = 0;       /* Inclusive.  0 = ZONE_DMA */
2439         unsigned long total_scanned;
2440         struct reclaim_state *reclaim_state = current->reclaim_state;
2441         unsigned long nr_soft_reclaimed;
2442         unsigned long nr_soft_scanned;
2443         struct scan_control sc = {
2444                 .gfp_mask = GFP_KERNEL,
2445                 .may_unmap = 1,
2446                 .may_swap = 1,
2447                 /*
2448                  * kswapd doesn't want to be bailed out while reclaim. because
2449                  * we want to put equal scanning pressure on each zone.
2450                  */
2451                 .nr_to_reclaim = ULONG_MAX,
2452                 .order = order,
2453                 .mem_cgroup = NULL,
2454         };
2455         struct shrink_control shrink = {
2456                 .gfp_mask = sc.gfp_mask,
2457         };
2458 loop_again:
2459         total_scanned = 0;
2460         sc.nr_reclaimed = 0;
2461         sc.may_writepage = !laptop_mode;
2462         count_vm_event(PAGEOUTRUN);
2463
2464         for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2465                 unsigned long lru_pages = 0;
2466                 int has_under_min_watermark_zone = 0;
2467
2468                 /* The swap token gets in the way of swapout... */
2469                 if (!priority)
2470                         disable_swap_token(NULL);
2471
2472                 all_zones_ok = 1;
2473                 balanced = 0;
2474
2475                 /*
2476                  * Scan in the highmem->dma direction for the highest
2477                  * zone which needs scanning
2478                  */
2479                 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
2480                         struct zone *zone = pgdat->node_zones + i;
2481
2482                         if (!populated_zone(zone))
2483                                 continue;
2484
2485                         if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2486                                 continue;
2487
2488                         /*
2489                          * Do some background aging of the anon list, to give
2490                          * pages a chance to be referenced before reclaiming.
2491                          */
2492                         if (inactive_anon_is_low(zone, &sc))
2493                                 shrink_active_list(SWAP_CLUSTER_MAX, zone,
2494                                                         &sc, priority, 0);
2495
2496                         if (!zone_watermark_ok_safe(zone, order,
2497                                         high_wmark_pages(zone), 0, 0)) {
2498                                 end_zone = i;
2499                                 break;
2500                         } else {
2501                                 /* If balanced, clear the congested flag */
2502                                 zone_clear_flag(zone, ZONE_CONGESTED);
2503                         }
2504                 }
2505                 if (i < 0)
2506                         goto out;
2507
2508                 for (i = 0; i <= end_zone; i++) {
2509                         struct zone *zone = pgdat->node_zones + i;
2510
2511                         lru_pages += zone_reclaimable_pages(zone);
2512                 }
2513
2514                 /*
2515                  * Now scan the zone in the dma->highmem direction, stopping
2516                  * at the last zone which needs scanning.
2517                  *
2518                  * We do this because the page allocator works in the opposite
2519                  * direction.  This prevents the page allocator from allocating
2520                  * pages behind kswapd's direction of progress, which would
2521                  * cause too much scanning of the lower zones.
2522                  */
2523                 for (i = 0; i <= end_zone; i++) {
2524                         struct zone *zone = pgdat->node_zones + i;
2525                         int nr_slab;
2526                         unsigned long balance_gap;
2527
2528                         if (!populated_zone(zone))
2529                                 continue;
2530
2531                         if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2532                                 continue;
2533
2534                         sc.nr_scanned = 0;
2535
2536                         nr_soft_scanned = 0;
2537                         /*
2538                          * Call soft limit reclaim before calling shrink_zone.
2539                          */
2540                         nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
2541                                                         order, sc.gfp_mask,
2542                                                         &nr_soft_scanned);
2543                         sc.nr_reclaimed += nr_soft_reclaimed;
2544                         total_scanned += nr_soft_scanned;
2545
2546                         /*
2547                          * We put equal pressure on every zone, unless
2548                          * one zone has way too many pages free
2549                          * already. The "too many pages" is defined
2550                          * as the high wmark plus a "gap" where the
2551                          * gap is either the low watermark or 1%
2552                          * of the zone, whichever is smaller.
2553                          */
2554                         balance_gap = min(low_wmark_pages(zone),
2555                                 (zone->present_pages +
2556                                         KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
2557                                 KSWAPD_ZONE_BALANCE_GAP_RATIO);
2558                         if (!zone_watermark_ok_safe(zone, order,
2559                                         high_wmark_pages(zone) + balance_gap,
2560                                         end_zone, 0)) {
2561                                 shrink_zone(priority, zone, &sc);
2562
2563                                 reclaim_state->reclaimed_slab = 0;
2564                                 nr_slab = shrink_slab(&shrink, sc.nr_scanned, lru_pages);
2565                                 sc.nr_reclaimed += reclaim_state->reclaimed_slab;
2566                                 total_scanned += sc.nr_scanned;
2567
2568                                 if (nr_slab == 0 && !zone_reclaimable(zone))
2569                                         zone->all_unreclaimable = 1;
2570                         }
2571
2572                         /*
2573                          * If we've done a decent amount of scanning and
2574                          * the reclaim ratio is low, start doing writepage
2575                          * even in laptop mode
2576                          */
2577                         if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
2578                             total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
2579                                 sc.may_writepage = 1;
2580
2581                         if (zone->all_unreclaimable) {
2582                                 if (end_zone && end_zone == i)
2583                                         end_zone--;
2584                                 continue;
2585                         }
2586
2587                         if (!zone_watermark_ok_safe(zone, order,
2588                                         high_wmark_pages(zone), end_zone, 0)) {
2589                                 all_zones_ok = 0;
2590                                 /*
2591                                  * We are still under min water mark.  This
2592                                  * means that we have a GFP_ATOMIC allocation
2593                                  * failure risk. Hurry up!
2594                                  */
2595                                 if (!zone_watermark_ok_safe(zone, order,
2596                                             min_wmark_pages(zone), end_zone, 0))
2597                                         has_under_min_watermark_zone = 1;
2598                         } else {
2599                                 /*
2600                                  * If a zone reaches its high watermark,
2601                                  * consider it to be no longer congested. It's
2602                                  * possible there are dirty pages backed by
2603                                  * congested BDIs but as pressure is relieved,
2604                                  * spectulatively avoid congestion waits
2605                                  */
2606                                 zone_clear_flag(zone, ZONE_CONGESTED);
2607                                 if (i <= *classzone_idx)
2608                                         balanced += zone->present_pages;
2609                         }
2610
2611                 }
2612                 if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))
2613                         break;          /* kswapd: all done */
2614                 /*
2615                  * OK, kswapd is getting into trouble.  Take a nap, then take
2616                  * another pass across the zones.
2617                  */
2618                 if (total_scanned && (priority < DEF_PRIORITY - 2)) {
2619                         if (has_under_min_watermark_zone)
2620                                 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT);
2621                         else
2622                                 congestion_wait(BLK_RW_ASYNC, HZ/10);
2623                 }
2624
2625                 /*
2626                  * We do this so kswapd doesn't build up large priorities for
2627                  * example when it is freeing in parallel with allocators. It
2628                  * matches the direct reclaim path behaviour in terms of impact
2629                  * on zone->*_priority.
2630                  */
2631                 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
2632                         break;
2633         }
2634 out:
2635
2636         /*
2637          * order-0: All zones must meet high watermark for a balanced node
2638          * high-order: Balanced zones must make up at least 25% of the node
2639          *             for the node to be balanced
2640          */
2641         if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) {
2642                 cond_resched();
2643
2644                 try_to_freeze();
2645
2646                 /*
2647                  * Fragmentation may mean that the system cannot be
2648                  * rebalanced for high-order allocations in all zones.
2649                  * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
2650                  * it means the zones have been fully scanned and are still
2651                  * not balanced. For high-order allocations, there is
2652                  * little point trying all over again as kswapd may
2653                  * infinite loop.
2654                  *
2655                  * Instead, recheck all watermarks at order-0 as they
2656                  * are the most important. If watermarks are ok, kswapd will go
2657                  * back to sleep. High-order users can still perform direct
2658                  * reclaim if they wish.
2659                  */
2660                 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX)
2661                         order = sc.order = 0;
2662
2663                 goto loop_again;
2664         }
2665
2666         /*
2667          * If kswapd was reclaiming at a higher order, it has the option of
2668          * sleeping without all zones being balanced. Before it does, it must
2669          * ensure that the watermarks for order-0 on *all* zones are met and
2670          * that the congestion flags are cleared. The congestion flag must
2671          * be cleared as kswapd is the only mechanism that clears the flag
2672          * and it is potentially going to sleep here.
2673          */
2674         if (order) {
2675                 for (i = 0; i <= end_zone; i++) {
2676                         struct zone *zone = pgdat->node_zones + i;
2677
2678                         if (!populated_zone(zone))
2679                                 continue;
2680
2681                         if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2682                                 continue;
2683
2684                         /* Confirm the zone is balanced for order-0 */
2685                         if (!zone_watermark_ok(zone, 0,
2686                                         high_wmark_pages(zone), 0, 0)) {
2687                                 order = sc.order = 0;
2688                                 goto loop_again;
2689                         }
2690
2691                         /* If balanced, clear the congested flag */
2692                         zone_clear_flag(zone, ZONE_CONGESTED);
2693                 }
2694         }
2695
2696         /*
2697          * Return the order we were reclaiming at so sleeping_prematurely()
2698          * makes a decision on the order we were last reclaiming at. However,
2699          * if another caller entered the allocator slow path while kswapd
2700          * was awake, order will remain at the higher level
2701          */
2702         *classzone_idx = end_zone;
2703         return order;
2704 }
2705
2706 static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx)
2707 {
2708         long remaining = 0;
2709         DEFINE_WAIT(wait);
2710
2711         if (freezing(current) || kthread_should_stop())
2712                 return;
2713
2714         prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2715
2716         /* Try to sleep for a short interval */
2717         if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2718                 remaining = schedule_timeout(HZ/10);
2719                 finish_wait(&pgdat->kswapd_wait, &wait);
2720                 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2721         }
2722
2723         /*
2724          * After a short sleep, check if it was a premature sleep. If not, then
2725          * go fully to sleep until explicitly woken up.
2726          */
2727         if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2728                 trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
2729
2730                 /*
2731                  * vmstat counters are not perfectly accurate and the estimated
2732                  * value for counters such as NR_FREE_PAGES can deviate from the
2733                  * true value by nr_online_cpus * threshold. To avoid the zone
2734                  * watermarks being breached while under pressure, we reduce the
2735                  * per-cpu vmstat threshold while kswapd is awake and restore
2736                  * them before going back to sleep.
2737                  */
2738                 set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold);
2739                 schedule();
2740                 set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold);
2741         } else {
2742                 if (remaining)
2743                         count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
2744                 else
2745                         count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
2746         }
2747         finish_wait(&pgdat->kswapd_wait, &wait);
2748 }
2749
2750 /*
2751  * The background pageout daemon, started as a kernel thread
2752  * from the init process.
2753  *
2754  * This basically trickles out pages so that we have _some_
2755  * free memory available even if there is no other activity
2756  * that frees anything up. This is needed for things like routing
2757  * etc, where we otherwise might have all activity going on in
2758  * asynchronous contexts that cannot page things out.
2759  *
2760  * If there are applications that are active memory-allocators
2761  * (most normal use), this basically shouldn't matter.
2762  */
2763 static int kswapd(void *p)
2764 {
2765         unsigned long order, new_order;
2766         int classzone_idx, new_classzone_idx;
2767         pg_data_t *pgdat = (pg_data_t*)p;
2768         struct task_struct *tsk = current;
2769
2770         struct reclaim_state reclaim_state = {
2771                 .reclaimed_slab = 0,
2772         };
2773         const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
2774
2775         lockdep_set_current_reclaim_state(GFP_KERNEL);
2776
2777         if (!cpumask_empty(cpumask))
2778                 set_cpus_allowed_ptr(tsk, cpumask);
2779         current->reclaim_state = &reclaim_state;
2780
2781         /*
2782          * Tell the memory management that we're a "memory allocator",
2783          * and that if we need more memory we should get access to it
2784          * regardless (see "__alloc_pages()"). "kswapd" should
2785          * never get caught in the normal page freeing logic.
2786          *
2787          * (Kswapd normally doesn't need memory anyway, but sometimes
2788          * you need a small amount of memory in order to be able to
2789          * page out something else, and this flag essentially protects
2790          * us from recursively trying to free more memory as we're
2791          * trying to free the first piece of memory in the first place).
2792          */
2793         tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
2794         set_freezable();
2795
2796         order = new_order = 0;
2797         classzone_idx = new_classzone_idx = pgdat->nr_zones - 1;
2798         for ( ; ; ) {
2799                 int ret;
2800
2801                 /*
2802                  * If the last balance_pgdat was unsuccessful it's unlikely a
2803                  * new request of a similar or harder type will succeed soon
2804                  * so consider going to sleep on the basis we reclaimed at
2805                  */
2806                 if (classzone_idx >= new_classzone_idx && order == new_order) {
2807                         new_order = pgdat->kswapd_max_order;
2808                         new_classzone_idx = pgdat->classzone_idx;
2809                         pgdat->kswapd_max_order =  0;
2810                         pgdat->classzone_idx = pgdat->nr_zones - 1;
2811                 }
2812
2813                 if (order < new_order || classzone_idx > new_classzone_idx) {
2814                         /*
2815                          * Don't sleep if someone wants a larger 'order'
2816                          * allocation or has tigher zone constraints
2817                          */
2818                         order = new_order;
2819                         classzone_idx = new_classzone_idx;
2820                 } else {
2821                         kswapd_try_to_sleep(pgdat, order, classzone_idx);
2822                         order = pgdat->kswapd_max_order;
2823                         classzone_idx = pgdat->classzone_idx;
2824                         pgdat->kswapd_max_order = 0;
2825                         pgdat->classzone_idx = pgdat->nr_zones - 1;
2826                 }
2827
2828                 ret = try_to_freeze();
2829                 if (kthread_should_stop())
2830                         break;
2831
2832                 /*
2833                  * We can speed up thawing tasks if we don't call balance_pgdat
2834                  * after returning from the refrigerator
2835                  */
2836                 if (!ret) {
2837                         trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
2838                         order = balance_pgdat(pgdat, order, &classzone_idx);
2839                 }
2840         }
2841         return 0;
2842 }
2843
2844 /*
2845  * A zone is low on free memory, so wake its kswapd task to service it.
2846  */
2847 void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
2848 {
2849         pg_data_t *pgdat;
2850
2851         if (!populated_zone(zone))
2852                 return;
2853
2854         if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2855                 return;
2856         pgdat = zone->zone_pgdat;
2857         if (pgdat->kswapd_max_order < order) {
2858                 pgdat->kswapd_max_order = order;
2859                 pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx);
2860         }
2861         if (!waitqueue_active(&pgdat->kswapd_wait))
2862                 return;
2863         if (zone_watermark_ok_safe(zone, order, low_wmark_pages(zone), 0, 0))
2864                 return;
2865
2866         trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);
2867         wake_up_interruptible(&pgdat->kswapd_wait);
2868 }
2869
2870 /*
2871  * The reclaimable count would be mostly accurate.
2872  * The less reclaimable pages may be
2873  * - mlocked pages, which will be moved to unevictable list when encountered
2874  * - mapped pages, which may require several travels to be reclaimed
2875  * - dirty pages, which is not "instantly" reclaimable
2876  */
2877 unsigned long global_reclaimable_pages(void)
2878 {
2879         int nr;
2880
2881         nr = global_page_state(NR_ACTIVE_FILE) +
2882              global_page_state(NR_INACTIVE_FILE);
2883
2884         if (nr_swap_pages > 0)
2885                 nr += global_page_state(NR_ACTIVE_ANON) +
2886                       global_page_state(NR_INACTIVE_ANON);
2887
2888         return nr;
2889 }
2890
2891 unsigned long zone_reclaimable_pages(struct zone *zone)
2892 {
2893         int nr;
2894
2895         nr = zone_page_state(zone, NR_ACTIVE_FILE) +
2896              zone_page_state(zone, NR_INACTIVE_FILE);
2897
2898         if (nr_swap_pages > 0)
2899                 nr += zone_page_state(zone, NR_ACTIVE_ANON) +
2900                       zone_page_state(zone, NR_INACTIVE_ANON);
2901
2902         return nr;
2903 }
2904
2905 #ifdef CONFIG_HIBERNATION
2906 /*
2907  * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
2908  * freed pages.
2909  *
2910  * Rather than trying to age LRUs the aim is to preserve the overall
2911  * LRU order by reclaiming preferentially
2912  * inactive > active > active referenced > active mapped
2913  */
2914 unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
2915 {
2916         struct reclaim_state reclaim_state;
2917         struct scan_control sc = {
2918                 .gfp_mask = GFP_HIGHUSER_MOVABLE,
2919                 .may_swap = 1,
2920                 .may_unmap = 1,
2921                 .may_writepage = 1,
2922                 .nr_to_reclaim = nr_to_reclaim,
2923                 .hibernation_mode = 1,
2924                 .order = 0,
2925         };
2926         struct shrink_control shrink = {
2927                 .gfp_mask = sc.gfp_mask,
2928         };
2929         struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
2930         struct task_struct *p = current;
2931         unsigned long nr_reclaimed;
2932
2933         p->flags |= PF_MEMALLOC;
2934         lockdep_set_current_reclaim_state(sc.gfp_mask);
2935         reclaim_state.reclaimed_slab = 0;
2936         p->reclaim_state = &reclaim_state;
2937
2938         nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2939
2940         p->reclaim_state = NULL;
2941         lockdep_clear_current_reclaim_state();
2942         p->flags &= ~PF_MEMALLOC;
2943
2944         return nr_reclaimed;
2945 }
2946 #endif /* CONFIG_HIBERNATION */
2947
2948 /* It's optimal to keep kswapds on the same CPUs as their memory, but
2949    not required for correctness.  So if the last cpu in a node goes
2950    away, we get changed to run anywhere: as the first one comes back,
2951    restore their cpu bindings. */
2952 static int __devinit cpu_callback(struct notifier_block *nfb,
2953                                   unsigned long action, void *hcpu)
2954 {
2955         int nid;
2956
2957         if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2958                 for_each_node_state(nid, N_HIGH_MEMORY) {
2959                         pg_data_t *pgdat = NODE_DATA(nid);
2960                         const struct cpumask *mask;
2961
2962                         mask = cpumask_of_node(pgdat->node_id);
2963
2964                         if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
2965                                 /* One of our CPUs online: restore mask */
2966                                 set_cpus_allowed_ptr(pgdat->kswapd, mask);
2967                 }
2968         }
2969         return NOTIFY_OK;
2970 }
2971
2972 /*
2973  * This kswapd start function will be called by init and node-hot-add.
2974  * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2975  */
2976 int kswapd_run(int nid)
2977 {
2978         pg_data_t *pgdat = NODE_DATA(nid);
2979         int ret = 0;
2980
2981         if (pgdat->kswapd)
2982                 return 0;
2983
2984         pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
2985         if (IS_ERR(pgdat->kswapd)) {
2986                 /* failure at boot is fatal */
2987                 BUG_ON(system_state == SYSTEM_BOOTING);
2988                 printk("Failed to start kswapd on node %d\n",nid);
2989                 ret = -1;
2990         }
2991         return ret;
2992 }
2993
2994 /*
2995  * Called by memory hotplug when all memory in a node is offlined.
2996  */
2997 void kswapd_stop(int nid)
2998 {
2999         struct task_struct *kswapd = NODE_DATA(nid)->kswapd;
3000
3001         if (kswapd)
3002                 kthread_stop(kswapd);
3003 }
3004
3005 static int __init kswapd_init(void)
3006 {
3007         int nid;
3008
3009         swap_setup();
3010         for_each_node_state(nid, N_HIGH_MEMORY)
3011                 kswapd_run(nid);
3012         hotcpu_notifier(cpu_callback, 0);
3013         return 0;
3014 }
3015
3016 module_init(kswapd_init)
3017
3018 #ifdef CONFIG_NUMA
3019 /*
3020  * Zone reclaim mode
3021  *
3022  * If non-zero call zone_reclaim when the number of free pages falls below
3023  * the watermarks.
3024  */
3025 int zone_reclaim_mode __read_mostly;
3026
3027 #define RECLAIM_OFF 0
3028 #define RECLAIM_ZONE (1<<0)     /* Run shrink_inactive_list on the zone */
3029 #define RECLAIM_WRITE (1<<1)    /* Writeout pages during reclaim */
3030 #define RECLAIM_SWAP (1<<2)     /* Swap pages out during reclaim */
3031
3032 /*
3033  * Priority for ZONE_RECLAIM. This determines the fraction of pages
3034  * of a node considered for each zone_reclaim. 4 scans 1/16th of
3035  * a zone.
3036  */
3037 #define ZONE_RECLAIM_PRIORITY 4
3038
3039 /*
3040  * Percentage of pages in a zone that must be unmapped for zone_reclaim to
3041  * occur.
3042  */
3043 int sysctl_min_unmapped_ratio = 1;
3044
3045 /*
3046  * If the number of slab pages in a zone grows beyond this percentage then
3047  * slab reclaim needs to occur.
3048  */
3049 int sysctl_min_slab_ratio = 5;
3050
3051 static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
3052 {
3053         unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
3054         unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
3055                 zone_page_state(zone, NR_ACTIVE_FILE);
3056
3057         /*
3058          * It's possible for there to be more file mapped pages than
3059          * accounted for by the pages on the file LRU lists because
3060          * tmpfs pages accounted for as ANON can also be FILE_MAPPED
3061          */
3062         return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
3063 }
3064
3065 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
3066 static long zone_pagecache_reclaimable(struct zone *zone)
3067 {
3068         long nr_pagecache_reclaimable;
3069         long delta = 0;
3070
3071         /*
3072          * If RECLAIM_SWAP is set, then all file pages are considered
3073          * potentially reclaimable. Otherwise, we have to worry about
3074          * pages like swapcache and zone_unmapped_file_pages() provides
3075          * a better estimate
3076          */
3077         if (zone_reclaim_mode & RECLAIM_SWAP)
3078                 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
3079         else
3080                 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
3081
3082         /* If we can't clean pages, remove dirty pages from consideration */
3083         if (!(zone_reclaim_mode & RECLAIM_WRITE))
3084                 delta += zone_page_state(zone, NR_FILE_DIRTY);
3085
3086         /* Watch for any possible underflows due to delta */
3087         if (unlikely(delta > nr_pagecache_reclaimable))
3088                 delta = nr_pagecache_reclaimable;
3089
3090         return nr_pagecache_reclaimable - delta;
3091 }
3092
3093 /*
3094  * Try to free up some pages from this zone through reclaim.
3095  */
3096 static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
3097 {
3098         /* Minimum pages needed in order to stay on node */
3099         const unsigned long nr_pages = 1 << order;
3100         struct task_struct *p = current;
3101         struct reclaim_state reclaim_state;
3102         int priority;
3103         struct scan_control sc = {
3104                 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
3105                 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
3106                 .may_swap = 1,
3107                 .nr_to_reclaim = max_t(unsigned long, nr_pages,
3108                                        SWAP_CLUSTER_MAX),
3109                 .gfp_mask = gfp_mask,
3110                 .order = order,
3111         };
3112         struct shrink_control shrink = {
3113                 .gfp_mask = sc.gfp_mask,
3114         };
3115         unsigned long nr_slab_pages0, nr_slab_pages1;
3116
3117         cond_resched();
3118         /*
3119          * We need to be able to allocate from the reserves for RECLAIM_SWAP
3120          * and we also need to be able to write out pages for RECLAIM_WRITE
3121          * and RECLAIM_SWAP.
3122          */
3123         p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
3124         lockdep_set_current_reclaim_state(gfp_mask);
3125         reclaim_state.reclaimed_slab = 0;
3126         p->reclaim_state = &reclaim_state;
3127
3128         if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
3129                 /*
3130                  * Free memory by calling shrink zone with increasing
3131                  * priorities until we have enough memory freed.
3132                  */
3133                 priority = ZONE_RECLAIM_PRIORITY;
3134                 do {
3135                         shrink_zone(priority, zone, &sc);
3136                         priority--;
3137                 } while (priority >= 0 && sc.nr_reclaimed < nr_pages);
3138         }
3139
3140         nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
3141         if (nr_slab_pages0 > zone->min_slab_pages) {
3142                 /*
3143                  * shrink_slab() does not currently allow us to determine how
3144                  * many pages were freed in this zone. So we take the current
3145                  * number of slab pages and shake the slab until it is reduced
3146                  * by the same nr_pages that we used for reclaiming unmapped
3147                  * pages.
3148                  *
3149                  * Note that shrink_slab will free memory on all zones and may
3150                  * take a long time.
3151                  */
3152                 for (;;) {
3153                         unsigned long lru_pages = zone_reclaimable_pages(zone);
3154
3155                         /* No reclaimable slab or very low memory pressure */
3156                         if (!shrink_slab(&shrink, sc.nr_scanned, lru_pages))
3157                                 break;
3158
3159                         /* Freed enough memory */
3160                         nr_slab_pages1 = zone_page_state(zone,
3161                                                         NR_SLAB_RECLAIMABLE);
3162                         if (nr_slab_pages1 + nr_pages <= nr_slab_pages0)
3163                                 break;
3164                 }
3165
3166                 /*
3167                  * Update nr_reclaimed by the number of slab pages we
3168                  * reclaimed from this zone.
3169                  */
3170                 nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
3171                 if (nr_slab_pages1 < nr_slab_pages0)
3172                         sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1;
3173         }
3174
3175         p->reclaim_state = NULL;
3176         current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
3177         lockdep_clear_current_reclaim_state();
3178         return sc.nr_reclaimed >= nr_pages;
3179 }
3180
3181 int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
3182 {
3183         int node_id;
3184         int ret;
3185
3186         /*
3187          * Zone reclaim reclaims unmapped file backed pages and
3188          * slab pages if we are over the defined limits.
3189          *
3190          * A small portion of unmapped file backed pages is needed for
3191          * file I/O otherwise pages read by file I/O will be immediately
3192          * thrown out if the zone is overallocated. So we do not reclaim
3193          * if less than a specified percentage of the zone is used by
3194          * unmapped file backed pages.
3195          */
3196         if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
3197             zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
3198                 return ZONE_RECLAIM_FULL;
3199
3200         if (zone->all_unreclaimable)
3201                 return ZONE_RECLAIM_FULL;
3202
3203         /*
3204          * Do not scan if the allocation should not be delayed.
3205          */
3206         if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
3207                 return ZONE_RECLAIM_NOSCAN;
3208
3209         /*
3210          * Only run zone reclaim on the local zone or on zones that do not
3211          * have associated processors. This will favor the local processor
3212          * over remote processors and spread off node memory allocations
3213          * as wide as possible.
3214          */
3215         node_id = zone_to_nid(zone);
3216         if (node_state(node_id, N_CPU) && node_id != numa_node_id())
3217                 return ZONE_RECLAIM_NOSCAN;
3218
3219         if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
3220                 return ZONE_RECLAIM_NOSCAN;
3221
3222         ret = __zone_reclaim(zone, gfp_mask, order);
3223         zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
3224
3225         if (!ret)
3226                 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
3227
3228         return ret;
3229 }
3230 #endif
3231
3232 /*
3233  * page_evictable - test whether a page is evictable
3234  * @page: the page to test
3235  * @vma: the VMA in which the page is or will be mapped, may be NULL
3236  *
3237  * Test whether page is evictable--i.e., should be placed on active/inactive
3238  * lists vs unevictable list.  The vma argument is !NULL when called from the
3239  * fault path to determine how to instantate a new page.
3240  *
3241  * Reasons page might not be evictable:
3242  * (1) page's mapping marked unevictable
3243  * (2) page is part of an mlocked VMA
3244  *
3245  */
3246 int page_evictable(struct page *page, struct vm_area_struct *vma)
3247 {
3248
3249         if (mapping_unevictable(page_mapping(page)))
3250                 return 0;
3251
3252         if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
3253                 return 0;
3254
3255         return 1;
3256 }
3257
3258 /**
3259  * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
3260  * @page: page to check evictability and move to appropriate lru list
3261  * @zone: zone page is in
3262  *
3263  * Checks a page for evictability and moves the page to the appropriate
3264  * zone lru list.
3265  *
3266  * Restrictions: zone->lru_lock must be held, page must be on LRU and must
3267  * have PageUnevictable set.
3268  */
3269 static void check_move_unevictable_page(struct page *page, struct zone *zone)
3270 {
3271         VM_BUG_ON(PageActive(page));
3272
3273 retry:
3274         ClearPageUnevictable(page);
3275         if (page_evictable(page, NULL)) {
3276                 enum lru_list l = page_lru_base_type(page);
3277
3278                 __dec_zone_state(zone, NR_UNEVICTABLE);
3279                 list_move(&page->lru, &zone->lru[l].list);
3280                 mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l);
3281                 __inc_zone_state(zone, NR_INACTIVE_ANON + l);
3282                 __count_vm_event(UNEVICTABLE_PGRESCUED);
3283         } else {
3284                 /*
3285                  * rotate unevictable list
3286                  */
3287                 SetPageUnevictable(page);
3288                 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
3289                 mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE);
3290                 if (page_evictable(page, NULL))
3291                         goto retry;
3292         }
3293 }
3294
3295 /**
3296  * scan_mapping_unevictable_pages - scan an address space for evictable pages
3297  * @mapping: struct address_space to scan for evictable pages
3298  *
3299  * Scan all pages in mapping.  Check unevictable pages for
3300  * evictability and move them to the appropriate zone lru list.
3301  */
3302 void scan_mapping_unevictable_pages(struct address_space *mapping)
3303 {
3304         pgoff_t next = 0;
3305         pgoff_t end   = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >>
3306                          PAGE_CACHE_SHIFT;
3307         struct zone *zone;
3308         struct pagevec pvec;
3309
3310         if (mapping->nrpages == 0)
3311                 return;
3312
3313         pagevec_init(&pvec, 0);
3314         while (next < end &&
3315                 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
3316                 int i;
3317                 int pg_scanned = 0;
3318
3319                 zone = NULL;
3320
3321                 for (i = 0; i < pagevec_count(&pvec); i++) {
3322                         struct page *page = pvec.pages[i];
3323                         pgoff_t page_index = page->index;
3324                         struct zone *pagezone = page_zone(page);
3325
3326                         pg_scanned++;
3327                         if (page_index > next)
3328                                 next = page_index;
3329                         next++;
3330
3331                         if (pagezone != zone) {
3332                                 if (zone)
3333                                         spin_unlock_irq(&zone->lru_lock);
3334                                 zone = pagezone;
3335                                 spin_lock_irq(&zone->lru_lock);
3336                         }
3337
3338                         if (PageLRU(page) && PageUnevictable(page))
3339                                 check_move_unevictable_page(page, zone);
3340                 }
3341                 if (zone)
3342                         spin_unlock_irq(&zone->lru_lock);
3343                 pagevec_release(&pvec);
3344
3345                 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
3346         }
3347
3348 }
3349
3350 /**
3351  * scan_zone_unevictable_pages - check unevictable list for evictable pages
3352  * @zone - zone of which to scan the unevictable list
3353  *
3354  * Scan @zone's unevictable LRU lists to check for pages that have become
3355  * evictable.  Move those that have to @zone's inactive list where they
3356  * become candidates for reclaim, unless shrink_inactive_zone() decides
3357  * to reactivate them.  Pages that are still unevictable are rotated
3358  * back onto @zone's unevictable list.
3359  */
3360 #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
3361 static void scan_zone_unevictable_pages(struct zone *zone)
3362 {
3363         struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list;
3364         unsigned long scan;
3365         unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE);
3366
3367         while (nr_to_scan > 0) {
3368                 unsigned long batch_size = min(nr_to_scan,
3369                                                 SCAN_UNEVICTABLE_BATCH_SIZE);
3370
3371                 spin_lock_irq(&zone->lru_lock);
3372                 for (scan = 0;  scan < batch_size; scan++) {
3373                         struct page *page = lru_to_page(l_unevictable);
3374
3375                         if (!trylock_page(page))
3376                                 continue;
3377
3378                         prefetchw_prev_lru_page(page, l_unevictable, flags);
3379
3380                         if (likely(PageLRU(page) && PageUnevictable(page)))
3381                                 check_move_unevictable_page(page, zone);
3382
3383                         unlock_page(page);
3384                 }
3385                 spin_unlock_irq(&zone->lru_lock);
3386
3387                 nr_to_scan -= batch_size;
3388         }
3389 }
3390
3391
3392 /**
3393  * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
3394  *
3395  * A really big hammer:  scan all zones' unevictable LRU lists to check for
3396  * pages that have become evictable.  Move those back to the zones'
3397  * inactive list where they become candidates for reclaim.
3398  * This occurs when, e.g., we have unswappable pages on the unevictable lists,
3399  * and we add swap to the system.  As such, it runs in the context of a task
3400  * that has possibly/probably made some previously unevictable pages
3401  * evictable.
3402  */
3403 static void scan_all_zones_unevictable_pages(void)
3404 {
3405         struct zone *zone;
3406
3407         for_each_zone(zone) {
3408                 scan_zone_unevictable_pages(zone);
3409         }
3410 }
3411
3412 /*
3413  * scan_unevictable_pages [vm] sysctl handler.  On demand re-scan of
3414  * all nodes' unevictable lists for evictable pages
3415  */
3416 unsigned long scan_unevictable_pages;
3417
3418 int scan_unevictable_handler(struct ctl_table *table, int write,
3419                            void __user *buffer,
3420                            size_t *length, loff_t *ppos)
3421 {
3422         proc_doulongvec_minmax(table, write, buffer, length, ppos);
3423
3424         if (write && *(unsigned long *)table->data)
3425                 scan_all_zones_unevictable_pages();
3426
3427         scan_unevictable_pages = 0;
3428         return 0;
3429 }
3430
3431 #ifdef CONFIG_NUMA
3432 /*
3433  * per node 'scan_unevictable_pages' attribute.  On demand re-scan of
3434  * a specified node's per zone unevictable lists for evictable pages.
3435  */
3436
3437 static ssize_t read_scan_unevictable_node(struct sys_device *dev,
3438                                           struct sysdev_attribute *attr,
3439                                           char *buf)
3440 {
3441         return sprintf(buf, "0\n");     /* always zero; should fit... */
3442 }
3443
3444 static ssize_t write_scan_unevictable_node(struct sys_device *dev,
3445                                            struct sysdev_attribute *attr,
3446                                         const char *buf, size_t count)
3447 {
3448         struct zone *node_zones = NODE_DATA(dev->id)->node_zones;
3449         struct zone *zone;
3450         unsigned long res;
3451         unsigned long req = strict_strtoul(buf, 10, &res);
3452
3453         if (!req)
3454                 return 1;       /* zero is no-op */
3455
3456         for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
3457                 if (!populated_zone(zone))
3458                         continue;
3459                 scan_zone_unevictable_pages(zone);
3460         }
3461         return 1;
3462 }
3463
3464
3465 static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
3466                         read_scan_unevictable_node,
3467                         write_scan_unevictable_node);
3468
3469 int scan_unevictable_register_node(struct node *node)
3470 {
3471         return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages);
3472 }
3473
3474 void scan_unevictable_unregister_node(struct node *node)
3475 {
3476         sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages);
3477 }
3478 #endif