Merge tag 'stable/for-linus-3.13-rc2-tag' of git://git.kernel.org/pub/scm/linux/kerne...
[platform/adaptation/renesas_rcar/renesas_kernel.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/vmpressure.h>
23 #include <linux/vmstat.h>
24 #include <linux/file.h>
25 #include <linux/writeback.h>
26 #include <linux/blkdev.h>
27 #include <linux/buffer_head.h>  /* for try_to_release_page(),
28                                         buffer_heads_over_limit */
29 #include <linux/mm_inline.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 #include <linux/balloon_compaction.h>
52
53 #include "internal.h"
54
55 #define CREATE_TRACE_POINTS
56 #include <trace/events/vmscan.h>
57
58 struct scan_control {
59         /* Incremented by the number of inactive pages that were scanned */
60         unsigned long nr_scanned;
61
62         /* Number of pages freed so far during a call to shrink_zones() */
63         unsigned long nr_reclaimed;
64
65         /* How many pages shrink_list() should reclaim */
66         unsigned long nr_to_reclaim;
67
68         unsigned long hibernation_mode;
69
70         /* This context's GFP mask */
71         gfp_t gfp_mask;
72
73         int may_writepage;
74
75         /* Can mapped pages be reclaimed? */
76         int may_unmap;
77
78         /* Can pages be swapped as part of reclaim? */
79         int may_swap;
80
81         int order;
82
83         /* Scan (total_size >> priority) pages at once */
84         int priority;
85
86         /*
87          * The memory cgroup that hit its limit and as a result is the
88          * primary target of this reclaim invocation.
89          */
90         struct mem_cgroup *target_mem_cgroup;
91
92         /*
93          * Nodemask of nodes allowed by the caller. If NULL, all nodes
94          * are scanned.
95          */
96         nodemask_t      *nodemask;
97 };
98
99 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
100
101 #ifdef ARCH_HAS_PREFETCH
102 #define prefetch_prev_lru_page(_page, _base, _field)                    \
103         do {                                                            \
104                 if ((_page)->lru.prev != _base) {                       \
105                         struct page *prev;                              \
106                                                                         \
107                         prev = lru_to_page(&(_page->lru));              \
108                         prefetch(&prev->_field);                        \
109                 }                                                       \
110         } while (0)
111 #else
112 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
113 #endif
114
115 #ifdef ARCH_HAS_PREFETCHW
116 #define prefetchw_prev_lru_page(_page, _base, _field)                   \
117         do {                                                            \
118                 if ((_page)->lru.prev != _base) {                       \
119                         struct page *prev;                              \
120                                                                         \
121                         prev = lru_to_page(&(_page->lru));              \
122                         prefetchw(&prev->_field);                       \
123                 }                                                       \
124         } while (0)
125 #else
126 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
127 #endif
128
129 /*
130  * From 0 .. 100.  Higher means more swappy.
131  */
132 int vm_swappiness = 60;
133 unsigned long vm_total_pages;   /* The total number of pages which the VM controls */
134
135 static LIST_HEAD(shrinker_list);
136 static DECLARE_RWSEM(shrinker_rwsem);
137
138 #ifdef CONFIG_MEMCG
139 static bool global_reclaim(struct scan_control *sc)
140 {
141         return !sc->target_mem_cgroup;
142 }
143 #else
144 static bool global_reclaim(struct scan_control *sc)
145 {
146         return true;
147 }
148 #endif
149
150 unsigned long zone_reclaimable_pages(struct zone *zone)
151 {
152         int nr;
153
154         nr = zone_page_state(zone, NR_ACTIVE_FILE) +
155              zone_page_state(zone, NR_INACTIVE_FILE);
156
157         if (get_nr_swap_pages() > 0)
158                 nr += zone_page_state(zone, NR_ACTIVE_ANON) +
159                       zone_page_state(zone, NR_INACTIVE_ANON);
160
161         return nr;
162 }
163
164 bool zone_reclaimable(struct zone *zone)
165 {
166         return zone->pages_scanned < zone_reclaimable_pages(zone) * 6;
167 }
168
169 static unsigned long get_lru_size(struct lruvec *lruvec, enum lru_list lru)
170 {
171         if (!mem_cgroup_disabled())
172                 return mem_cgroup_get_lru_size(lruvec, lru);
173
174         return zone_page_state(lruvec_zone(lruvec), NR_LRU_BASE + lru);
175 }
176
177 /*
178  * Add a shrinker callback to be called from the vm.
179  */
180 int register_shrinker(struct shrinker *shrinker)
181 {
182         size_t size = sizeof(*shrinker->nr_deferred);
183
184         /*
185          * If we only have one possible node in the system anyway, save
186          * ourselves the trouble and disable NUMA aware behavior. This way we
187          * will save memory and some small loop time later.
188          */
189         if (nr_node_ids == 1)
190                 shrinker->flags &= ~SHRINKER_NUMA_AWARE;
191
192         if (shrinker->flags & SHRINKER_NUMA_AWARE)
193                 size *= nr_node_ids;
194
195         shrinker->nr_deferred = kzalloc(size, GFP_KERNEL);
196         if (!shrinker->nr_deferred)
197                 return -ENOMEM;
198
199         down_write(&shrinker_rwsem);
200         list_add_tail(&shrinker->list, &shrinker_list);
201         up_write(&shrinker_rwsem);
202         return 0;
203 }
204 EXPORT_SYMBOL(register_shrinker);
205
206 /*
207  * Remove one
208  */
209 void unregister_shrinker(struct shrinker *shrinker)
210 {
211         down_write(&shrinker_rwsem);
212         list_del(&shrinker->list);
213         up_write(&shrinker_rwsem);
214         kfree(shrinker->nr_deferred);
215 }
216 EXPORT_SYMBOL(unregister_shrinker);
217
218 #define SHRINK_BATCH 128
219
220 static unsigned long
221 shrink_slab_node(struct shrink_control *shrinkctl, struct shrinker *shrinker,
222                  unsigned long nr_pages_scanned, unsigned long lru_pages)
223 {
224         unsigned long freed = 0;
225         unsigned long long delta;
226         long total_scan;
227         long max_pass;
228         long nr;
229         long new_nr;
230         int nid = shrinkctl->nid;
231         long batch_size = shrinker->batch ? shrinker->batch
232                                           : SHRINK_BATCH;
233
234         max_pass = shrinker->count_objects(shrinker, shrinkctl);
235         if (max_pass == 0)
236                 return 0;
237
238         /*
239          * copy the current shrinker scan count into a local variable
240          * and zero it so that other concurrent shrinker invocations
241          * don't also do this scanning work.
242          */
243         nr = atomic_long_xchg(&shrinker->nr_deferred[nid], 0);
244
245         total_scan = nr;
246         delta = (4 * nr_pages_scanned) / shrinker->seeks;
247         delta *= max_pass;
248         do_div(delta, lru_pages + 1);
249         total_scan += delta;
250         if (total_scan < 0) {
251                 printk(KERN_ERR
252                 "shrink_slab: %pF negative objects to delete nr=%ld\n",
253                        shrinker->scan_objects, total_scan);
254                 total_scan = max_pass;
255         }
256
257         /*
258          * We need to avoid excessive windup on filesystem shrinkers
259          * due to large numbers of GFP_NOFS allocations causing the
260          * shrinkers to return -1 all the time. This results in a large
261          * nr being built up so when a shrink that can do some work
262          * comes along it empties the entire cache due to nr >>>
263          * max_pass.  This is bad for sustaining a working set in
264          * memory.
265          *
266          * Hence only allow the shrinker to scan the entire cache when
267          * a large delta change is calculated directly.
268          */
269         if (delta < max_pass / 4)
270                 total_scan = min(total_scan, max_pass / 2);
271
272         /*
273          * Avoid risking looping forever due to too large nr value:
274          * never try to free more than twice the estimate number of
275          * freeable entries.
276          */
277         if (total_scan > max_pass * 2)
278                 total_scan = max_pass * 2;
279
280         trace_mm_shrink_slab_start(shrinker, shrinkctl, nr,
281                                 nr_pages_scanned, lru_pages,
282                                 max_pass, delta, total_scan);
283
284         while (total_scan >= batch_size) {
285                 unsigned long ret;
286
287                 shrinkctl->nr_to_scan = batch_size;
288                 ret = shrinker->scan_objects(shrinker, shrinkctl);
289                 if (ret == SHRINK_STOP)
290                         break;
291                 freed += ret;
292
293                 count_vm_events(SLABS_SCANNED, batch_size);
294                 total_scan -= batch_size;
295
296                 cond_resched();
297         }
298
299         /*
300          * move the unused scan count back into the shrinker in a
301          * manner that handles concurrent updates. If we exhausted the
302          * scan, there is no need to do an update.
303          */
304         if (total_scan > 0)
305                 new_nr = atomic_long_add_return(total_scan,
306                                                 &shrinker->nr_deferred[nid]);
307         else
308                 new_nr = atomic_long_read(&shrinker->nr_deferred[nid]);
309
310         trace_mm_shrink_slab_end(shrinker, freed, nr, new_nr);
311         return freed;
312 }
313
314 /*
315  * Call the shrink functions to age shrinkable caches
316  *
317  * Here we assume it costs one seek to replace a lru page and that it also
318  * takes a seek to recreate a cache object.  With this in mind we age equal
319  * percentages of the lru and ageable caches.  This should balance the seeks
320  * generated by these structures.
321  *
322  * If the vm encountered mapped pages on the LRU it increase the pressure on
323  * slab to avoid swapping.
324  *
325  * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
326  *
327  * `lru_pages' represents the number of on-LRU pages in all the zones which
328  * are eligible for the caller's allocation attempt.  It is used for balancing
329  * slab reclaim versus page reclaim.
330  *
331  * Returns the number of slab objects which we shrunk.
332  */
333 unsigned long shrink_slab(struct shrink_control *shrinkctl,
334                           unsigned long nr_pages_scanned,
335                           unsigned long lru_pages)
336 {
337         struct shrinker *shrinker;
338         unsigned long freed = 0;
339
340         if (nr_pages_scanned == 0)
341                 nr_pages_scanned = SWAP_CLUSTER_MAX;
342
343         if (!down_read_trylock(&shrinker_rwsem)) {
344                 /*
345                  * If we would return 0, our callers would understand that we
346                  * have nothing else to shrink and give up trying. By returning
347                  * 1 we keep it going and assume we'll be able to shrink next
348                  * time.
349                  */
350                 freed = 1;
351                 goto out;
352         }
353
354         list_for_each_entry(shrinker, &shrinker_list, list) {
355                 for_each_node_mask(shrinkctl->nid, shrinkctl->nodes_to_scan) {
356                         if (!node_online(shrinkctl->nid))
357                                 continue;
358
359                         if (!(shrinker->flags & SHRINKER_NUMA_AWARE) &&
360                             (shrinkctl->nid != 0))
361                                 break;
362
363                         freed += shrink_slab_node(shrinkctl, shrinker,
364                                  nr_pages_scanned, lru_pages);
365
366                 }
367         }
368         up_read(&shrinker_rwsem);
369 out:
370         cond_resched();
371         return freed;
372 }
373
374 static inline int is_page_cache_freeable(struct page *page)
375 {
376         /*
377          * A freeable page cache page is referenced only by the caller
378          * that isolated the page, the page cache radix tree and
379          * optional buffer heads at page->private.
380          */
381         return page_count(page) - page_has_private(page) == 2;
382 }
383
384 static int may_write_to_queue(struct backing_dev_info *bdi,
385                               struct scan_control *sc)
386 {
387         if (current->flags & PF_SWAPWRITE)
388                 return 1;
389         if (!bdi_write_congested(bdi))
390                 return 1;
391         if (bdi == current->backing_dev_info)
392                 return 1;
393         return 0;
394 }
395
396 /*
397  * We detected a synchronous write error writing a page out.  Probably
398  * -ENOSPC.  We need to propagate that into the address_space for a subsequent
399  * fsync(), msync() or close().
400  *
401  * The tricky part is that after writepage we cannot touch the mapping: nothing
402  * prevents it from being freed up.  But we have a ref on the page and once
403  * that page is locked, the mapping is pinned.
404  *
405  * We're allowed to run sleeping lock_page() here because we know the caller has
406  * __GFP_FS.
407  */
408 static void handle_write_error(struct address_space *mapping,
409                                 struct page *page, int error)
410 {
411         lock_page(page);
412         if (page_mapping(page) == mapping)
413                 mapping_set_error(mapping, error);
414         unlock_page(page);
415 }
416
417 /* possible outcome of pageout() */
418 typedef enum {
419         /* failed to write page out, page is locked */
420         PAGE_KEEP,
421         /* move page to the active list, page is locked */
422         PAGE_ACTIVATE,
423         /* page has been sent to the disk successfully, page is unlocked */
424         PAGE_SUCCESS,
425         /* page is clean and locked */
426         PAGE_CLEAN,
427 } pageout_t;
428
429 /*
430  * pageout is called by shrink_page_list() for each dirty page.
431  * Calls ->writepage().
432  */
433 static pageout_t pageout(struct page *page, struct address_space *mapping,
434                          struct scan_control *sc)
435 {
436         /*
437          * If the page is dirty, only perform writeback if that write
438          * will be non-blocking.  To prevent this allocation from being
439          * stalled by pagecache activity.  But note that there may be
440          * stalls if we need to run get_block().  We could test
441          * PagePrivate for that.
442          *
443          * If this process is currently in __generic_file_aio_write() against
444          * this page's queue, we can perform writeback even if that
445          * will block.
446          *
447          * If the page is swapcache, write it back even if that would
448          * block, for some throttling. This happens by accident, because
449          * swap_backing_dev_info is bust: it doesn't reflect the
450          * congestion state of the swapdevs.  Easy to fix, if needed.
451          */
452         if (!is_page_cache_freeable(page))
453                 return PAGE_KEEP;
454         if (!mapping) {
455                 /*
456                  * Some data journaling orphaned pages can have
457                  * page->mapping == NULL while being dirty with clean buffers.
458                  */
459                 if (page_has_private(page)) {
460                         if (try_to_free_buffers(page)) {
461                                 ClearPageDirty(page);
462                                 printk("%s: orphaned page\n", __func__);
463                                 return PAGE_CLEAN;
464                         }
465                 }
466                 return PAGE_KEEP;
467         }
468         if (mapping->a_ops->writepage == NULL)
469                 return PAGE_ACTIVATE;
470         if (!may_write_to_queue(mapping->backing_dev_info, sc))
471                 return PAGE_KEEP;
472
473         if (clear_page_dirty_for_io(page)) {
474                 int res;
475                 struct writeback_control wbc = {
476                         .sync_mode = WB_SYNC_NONE,
477                         .nr_to_write = SWAP_CLUSTER_MAX,
478                         .range_start = 0,
479                         .range_end = LLONG_MAX,
480                         .for_reclaim = 1,
481                 };
482
483                 SetPageReclaim(page);
484                 res = mapping->a_ops->writepage(page, &wbc);
485                 if (res < 0)
486                         handle_write_error(mapping, page, res);
487                 if (res == AOP_WRITEPAGE_ACTIVATE) {
488                         ClearPageReclaim(page);
489                         return PAGE_ACTIVATE;
490                 }
491
492                 if (!PageWriteback(page)) {
493                         /* synchronous write or broken a_ops? */
494                         ClearPageReclaim(page);
495                 }
496                 trace_mm_vmscan_writepage(page, trace_reclaim_flags(page));
497                 inc_zone_page_state(page, NR_VMSCAN_WRITE);
498                 return PAGE_SUCCESS;
499         }
500
501         return PAGE_CLEAN;
502 }
503
504 /*
505  * Same as remove_mapping, but if the page is removed from the mapping, it
506  * gets returned with a refcount of 0.
507  */
508 static int __remove_mapping(struct address_space *mapping, struct page *page)
509 {
510         BUG_ON(!PageLocked(page));
511         BUG_ON(mapping != page_mapping(page));
512
513         spin_lock_irq(&mapping->tree_lock);
514         /*
515          * The non racy check for a busy page.
516          *
517          * Must be careful with the order of the tests. When someone has
518          * a ref to the page, it may be possible that they dirty it then
519          * drop the reference. So if PageDirty is tested before page_count
520          * here, then the following race may occur:
521          *
522          * get_user_pages(&page);
523          * [user mapping goes away]
524          * write_to(page);
525          *                              !PageDirty(page)    [good]
526          * SetPageDirty(page);
527          * put_page(page);
528          *                              !page_count(page)   [good, discard it]
529          *
530          * [oops, our write_to data is lost]
531          *
532          * Reversing the order of the tests ensures such a situation cannot
533          * escape unnoticed. The smp_rmb is needed to ensure the page->flags
534          * load is not satisfied before that of page->_count.
535          *
536          * Note that if SetPageDirty is always performed via set_page_dirty,
537          * and thus under tree_lock, then this ordering is not required.
538          */
539         if (!page_freeze_refs(page, 2))
540                 goto cannot_free;
541         /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
542         if (unlikely(PageDirty(page))) {
543                 page_unfreeze_refs(page, 2);
544                 goto cannot_free;
545         }
546
547         if (PageSwapCache(page)) {
548                 swp_entry_t swap = { .val = page_private(page) };
549                 __delete_from_swap_cache(page);
550                 spin_unlock_irq(&mapping->tree_lock);
551                 swapcache_free(swap, page);
552         } else {
553                 void (*freepage)(struct page *);
554
555                 freepage = mapping->a_ops->freepage;
556
557                 __delete_from_page_cache(page);
558                 spin_unlock_irq(&mapping->tree_lock);
559                 mem_cgroup_uncharge_cache_page(page);
560
561                 if (freepage != NULL)
562                         freepage(page);
563         }
564
565         return 1;
566
567 cannot_free:
568         spin_unlock_irq(&mapping->tree_lock);
569         return 0;
570 }
571
572 /*
573  * Attempt to detach a locked page from its ->mapping.  If it is dirty or if
574  * someone else has a ref on the page, abort and return 0.  If it was
575  * successfully detached, return 1.  Assumes the caller has a single ref on
576  * this page.
577  */
578 int remove_mapping(struct address_space *mapping, struct page *page)
579 {
580         if (__remove_mapping(mapping, page)) {
581                 /*
582                  * Unfreezing the refcount with 1 rather than 2 effectively
583                  * drops the pagecache ref for us without requiring another
584                  * atomic operation.
585                  */
586                 page_unfreeze_refs(page, 1);
587                 return 1;
588         }
589         return 0;
590 }
591
592 /**
593  * putback_lru_page - put previously isolated page onto appropriate LRU list
594  * @page: page to be put back to appropriate lru list
595  *
596  * Add previously isolated @page to appropriate LRU list.
597  * Page may still be unevictable for other reasons.
598  *
599  * lru_lock must not be held, interrupts must be enabled.
600  */
601 void putback_lru_page(struct page *page)
602 {
603         bool is_unevictable;
604         int was_unevictable = PageUnevictable(page);
605
606         VM_BUG_ON(PageLRU(page));
607
608 redo:
609         ClearPageUnevictable(page);
610
611         if (page_evictable(page)) {
612                 /*
613                  * For evictable pages, we can use the cache.
614                  * In event of a race, worst case is we end up with an
615                  * unevictable page on [in]active list.
616                  * We know how to handle that.
617                  */
618                 is_unevictable = false;
619                 lru_cache_add(page);
620         } else {
621                 /*
622                  * Put unevictable pages directly on zone's unevictable
623                  * list.
624                  */
625                 is_unevictable = true;
626                 add_page_to_unevictable_list(page);
627                 /*
628                  * When racing with an mlock or AS_UNEVICTABLE clearing
629                  * (page is unlocked) make sure that if the other thread
630                  * does not observe our setting of PG_lru and fails
631                  * isolation/check_move_unevictable_pages,
632                  * we see PG_mlocked/AS_UNEVICTABLE cleared below and move
633                  * the page back to the evictable list.
634                  *
635                  * The other side is TestClearPageMlocked() or shmem_lock().
636                  */
637                 smp_mb();
638         }
639
640         /*
641          * page's status can change while we move it among lru. If an evictable
642          * page is on unevictable list, it never be freed. To avoid that,
643          * check after we added it to the list, again.
644          */
645         if (is_unevictable && page_evictable(page)) {
646                 if (!isolate_lru_page(page)) {
647                         put_page(page);
648                         goto redo;
649                 }
650                 /* This means someone else dropped this page from LRU
651                  * So, it will be freed or putback to LRU again. There is
652                  * nothing to do here.
653                  */
654         }
655
656         if (was_unevictable && !is_unevictable)
657                 count_vm_event(UNEVICTABLE_PGRESCUED);
658         else if (!was_unevictable && is_unevictable)
659                 count_vm_event(UNEVICTABLE_PGCULLED);
660
661         put_page(page);         /* drop ref from isolate */
662 }
663
664 enum page_references {
665         PAGEREF_RECLAIM,
666         PAGEREF_RECLAIM_CLEAN,
667         PAGEREF_KEEP,
668         PAGEREF_ACTIVATE,
669 };
670
671 static enum page_references page_check_references(struct page *page,
672                                                   struct scan_control *sc)
673 {
674         int referenced_ptes, referenced_page;
675         unsigned long vm_flags;
676
677         referenced_ptes = page_referenced(page, 1, sc->target_mem_cgroup,
678                                           &vm_flags);
679         referenced_page = TestClearPageReferenced(page);
680
681         /*
682          * Mlock lost the isolation race with us.  Let try_to_unmap()
683          * move the page to the unevictable list.
684          */
685         if (vm_flags & VM_LOCKED)
686                 return PAGEREF_RECLAIM;
687
688         if (referenced_ptes) {
689                 if (PageSwapBacked(page))
690                         return PAGEREF_ACTIVATE;
691                 /*
692                  * All mapped pages start out with page table
693                  * references from the instantiating fault, so we need
694                  * to look twice if a mapped file page is used more
695                  * than once.
696                  *
697                  * Mark it and spare it for another trip around the
698                  * inactive list.  Another page table reference will
699                  * lead to its activation.
700                  *
701                  * Note: the mark is set for activated pages as well
702                  * so that recently deactivated but used pages are
703                  * quickly recovered.
704                  */
705                 SetPageReferenced(page);
706
707                 if (referenced_page || referenced_ptes > 1)
708                         return PAGEREF_ACTIVATE;
709
710                 /*
711                  * Activate file-backed executable pages after first usage.
712                  */
713                 if (vm_flags & VM_EXEC)
714                         return PAGEREF_ACTIVATE;
715
716                 return PAGEREF_KEEP;
717         }
718
719         /* Reclaim if clean, defer dirty pages to writeback */
720         if (referenced_page && !PageSwapBacked(page))
721                 return PAGEREF_RECLAIM_CLEAN;
722
723         return PAGEREF_RECLAIM;
724 }
725
726 /* Check if a page is dirty or under writeback */
727 static void page_check_dirty_writeback(struct page *page,
728                                        bool *dirty, bool *writeback)
729 {
730         struct address_space *mapping;
731
732         /*
733          * Anonymous pages are not handled by flushers and must be written
734          * from reclaim context. Do not stall reclaim based on them
735          */
736         if (!page_is_file_cache(page)) {
737                 *dirty = false;
738                 *writeback = false;
739                 return;
740         }
741
742         /* By default assume that the page flags are accurate */
743         *dirty = PageDirty(page);
744         *writeback = PageWriteback(page);
745
746         /* Verify dirty/writeback state if the filesystem supports it */
747         if (!page_has_private(page))
748                 return;
749
750         mapping = page_mapping(page);
751         if (mapping && mapping->a_ops->is_dirty_writeback)
752                 mapping->a_ops->is_dirty_writeback(page, dirty, writeback);
753 }
754
755 /*
756  * shrink_page_list() returns the number of reclaimed pages
757  */
758 static unsigned long shrink_page_list(struct list_head *page_list,
759                                       struct zone *zone,
760                                       struct scan_control *sc,
761                                       enum ttu_flags ttu_flags,
762                                       unsigned long *ret_nr_dirty,
763                                       unsigned long *ret_nr_unqueued_dirty,
764                                       unsigned long *ret_nr_congested,
765                                       unsigned long *ret_nr_writeback,
766                                       unsigned long *ret_nr_immediate,
767                                       bool force_reclaim)
768 {
769         LIST_HEAD(ret_pages);
770         LIST_HEAD(free_pages);
771         int pgactivate = 0;
772         unsigned long nr_unqueued_dirty = 0;
773         unsigned long nr_dirty = 0;
774         unsigned long nr_congested = 0;
775         unsigned long nr_reclaimed = 0;
776         unsigned long nr_writeback = 0;
777         unsigned long nr_immediate = 0;
778
779         cond_resched();
780
781         mem_cgroup_uncharge_start();
782         while (!list_empty(page_list)) {
783                 struct address_space *mapping;
784                 struct page *page;
785                 int may_enter_fs;
786                 enum page_references references = PAGEREF_RECLAIM_CLEAN;
787                 bool dirty, writeback;
788
789                 cond_resched();
790
791                 page = lru_to_page(page_list);
792                 list_del(&page->lru);
793
794                 if (!trylock_page(page))
795                         goto keep;
796
797                 VM_BUG_ON(PageActive(page));
798                 VM_BUG_ON(page_zone(page) != zone);
799
800                 sc->nr_scanned++;
801
802                 if (unlikely(!page_evictable(page)))
803                         goto cull_mlocked;
804
805                 if (!sc->may_unmap && page_mapped(page))
806                         goto keep_locked;
807
808                 /* Double the slab pressure for mapped and swapcache pages */
809                 if (page_mapped(page) || PageSwapCache(page))
810                         sc->nr_scanned++;
811
812                 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
813                         (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
814
815                 /*
816                  * The number of dirty pages determines if a zone is marked
817                  * reclaim_congested which affects wait_iff_congested. kswapd
818                  * will stall and start writing pages if the tail of the LRU
819                  * is all dirty unqueued pages.
820                  */
821                 page_check_dirty_writeback(page, &dirty, &writeback);
822                 if (dirty || writeback)
823                         nr_dirty++;
824
825                 if (dirty && !writeback)
826                         nr_unqueued_dirty++;
827
828                 /*
829                  * Treat this page as congested if the underlying BDI is or if
830                  * pages are cycling through the LRU so quickly that the
831                  * pages marked for immediate reclaim are making it to the
832                  * end of the LRU a second time.
833                  */
834                 mapping = page_mapping(page);
835                 if ((mapping && bdi_write_congested(mapping->backing_dev_info)) ||
836                     (writeback && PageReclaim(page)))
837                         nr_congested++;
838
839                 /*
840                  * If a page at the tail of the LRU is under writeback, there
841                  * are three cases to consider.
842                  *
843                  * 1) If reclaim is encountering an excessive number of pages
844                  *    under writeback and this page is both under writeback and
845                  *    PageReclaim then it indicates that pages are being queued
846                  *    for IO but are being recycled through the LRU before the
847                  *    IO can complete. Waiting on the page itself risks an
848                  *    indefinite stall if it is impossible to writeback the
849                  *    page due to IO error or disconnected storage so instead
850                  *    note that the LRU is being scanned too quickly and the
851                  *    caller can stall after page list has been processed.
852                  *
853                  * 2) Global reclaim encounters a page, memcg encounters a
854                  *    page that is not marked for immediate reclaim or
855                  *    the caller does not have __GFP_IO. In this case mark
856                  *    the page for immediate reclaim and continue scanning.
857                  *
858                  *    __GFP_IO is checked  because a loop driver thread might
859                  *    enter reclaim, and deadlock if it waits on a page for
860                  *    which it is needed to do the write (loop masks off
861                  *    __GFP_IO|__GFP_FS for this reason); but more thought
862                  *    would probably show more reasons.
863                  *
864                  *    Don't require __GFP_FS, since we're not going into the
865                  *    FS, just waiting on its writeback completion. Worryingly,
866                  *    ext4 gfs2 and xfs allocate pages with
867                  *    grab_cache_page_write_begin(,,AOP_FLAG_NOFS), so testing
868                  *    may_enter_fs here is liable to OOM on them.
869                  *
870                  * 3) memcg encounters a page that is not already marked
871                  *    PageReclaim. memcg does not have any dirty pages
872                  *    throttling so we could easily OOM just because too many
873                  *    pages are in writeback and there is nothing else to
874                  *    reclaim. Wait for the writeback to complete.
875                  */
876                 if (PageWriteback(page)) {
877                         /* Case 1 above */
878                         if (current_is_kswapd() &&
879                             PageReclaim(page) &&
880                             zone_is_reclaim_writeback(zone)) {
881                                 nr_immediate++;
882                                 goto keep_locked;
883
884                         /* Case 2 above */
885                         } else if (global_reclaim(sc) ||
886                             !PageReclaim(page) || !(sc->gfp_mask & __GFP_IO)) {
887                                 /*
888                                  * This is slightly racy - end_page_writeback()
889                                  * might have just cleared PageReclaim, then
890                                  * setting PageReclaim here end up interpreted
891                                  * as PageReadahead - but that does not matter
892                                  * enough to care.  What we do want is for this
893                                  * page to have PageReclaim set next time memcg
894                                  * reclaim reaches the tests above, so it will
895                                  * then wait_on_page_writeback() to avoid OOM;
896                                  * and it's also appropriate in global reclaim.
897                                  */
898                                 SetPageReclaim(page);
899                                 nr_writeback++;
900
901                                 goto keep_locked;
902
903                         /* Case 3 above */
904                         } else {
905                                 wait_on_page_writeback(page);
906                         }
907                 }
908
909                 if (!force_reclaim)
910                         references = page_check_references(page, sc);
911
912                 switch (references) {
913                 case PAGEREF_ACTIVATE:
914                         goto activate_locked;
915                 case PAGEREF_KEEP:
916                         goto keep_locked;
917                 case PAGEREF_RECLAIM:
918                 case PAGEREF_RECLAIM_CLEAN:
919                         ; /* try to reclaim the page below */
920                 }
921
922                 /*
923                  * Anonymous process memory has backing store?
924                  * Try to allocate it some swap space here.
925                  */
926                 if (PageAnon(page) && !PageSwapCache(page)) {
927                         if (!(sc->gfp_mask & __GFP_IO))
928                                 goto keep_locked;
929                         if (!add_to_swap(page, page_list))
930                                 goto activate_locked;
931                         may_enter_fs = 1;
932
933                         /* Adding to swap updated mapping */
934                         mapping = page_mapping(page);
935                 }
936
937                 /*
938                  * The page is mapped into the page tables of one or more
939                  * processes. Try to unmap it here.
940                  */
941                 if (page_mapped(page) && mapping) {
942                         switch (try_to_unmap(page, ttu_flags)) {
943                         case SWAP_FAIL:
944                                 goto activate_locked;
945                         case SWAP_AGAIN:
946                                 goto keep_locked;
947                         case SWAP_MLOCK:
948                                 goto cull_mlocked;
949                         case SWAP_SUCCESS:
950                                 ; /* try to free the page below */
951                         }
952                 }
953
954                 if (PageDirty(page)) {
955                         /*
956                          * Only kswapd can writeback filesystem pages to
957                          * avoid risk of stack overflow but only writeback
958                          * if many dirty pages have been encountered.
959                          */
960                         if (page_is_file_cache(page) &&
961                                         (!current_is_kswapd() ||
962                                          !zone_is_reclaim_dirty(zone))) {
963                                 /*
964                                  * Immediately reclaim when written back.
965                                  * Similar in principal to deactivate_page()
966                                  * except we already have the page isolated
967                                  * and know it's dirty
968                                  */
969                                 inc_zone_page_state(page, NR_VMSCAN_IMMEDIATE);
970                                 SetPageReclaim(page);
971
972                                 goto keep_locked;
973                         }
974
975                         if (references == PAGEREF_RECLAIM_CLEAN)
976                                 goto keep_locked;
977                         if (!may_enter_fs)
978                                 goto keep_locked;
979                         if (!sc->may_writepage)
980                                 goto keep_locked;
981
982                         /* Page is dirty, try to write it out here */
983                         switch (pageout(page, mapping, sc)) {
984                         case PAGE_KEEP:
985                                 goto keep_locked;
986                         case PAGE_ACTIVATE:
987                                 goto activate_locked;
988                         case PAGE_SUCCESS:
989                                 if (PageWriteback(page))
990                                         goto keep;
991                                 if (PageDirty(page))
992                                         goto keep;
993
994                                 /*
995                                  * A synchronous write - probably a ramdisk.  Go
996                                  * ahead and try to reclaim the page.
997                                  */
998                                 if (!trylock_page(page))
999                                         goto keep;
1000                                 if (PageDirty(page) || PageWriteback(page))
1001                                         goto keep_locked;
1002                                 mapping = page_mapping(page);
1003                         case PAGE_CLEAN:
1004                                 ; /* try to free the page below */
1005                         }
1006                 }
1007
1008                 /*
1009                  * If the page has buffers, try to free the buffer mappings
1010                  * associated with this page. If we succeed we try to free
1011                  * the page as well.
1012                  *
1013                  * We do this even if the page is PageDirty().
1014                  * try_to_release_page() does not perform I/O, but it is
1015                  * possible for a page to have PageDirty set, but it is actually
1016                  * clean (all its buffers are clean).  This happens if the
1017                  * buffers were written out directly, with submit_bh(). ext3
1018                  * will do this, as well as the blockdev mapping.
1019                  * try_to_release_page() will discover that cleanness and will
1020                  * drop the buffers and mark the page clean - it can be freed.
1021                  *
1022                  * Rarely, pages can have buffers and no ->mapping.  These are
1023                  * the pages which were not successfully invalidated in
1024                  * truncate_complete_page().  We try to drop those buffers here
1025                  * and if that worked, and the page is no longer mapped into
1026                  * process address space (page_count == 1) it can be freed.
1027                  * Otherwise, leave the page on the LRU so it is swappable.
1028                  */
1029                 if (page_has_private(page)) {
1030                         if (!try_to_release_page(page, sc->gfp_mask))
1031                                 goto activate_locked;
1032                         if (!mapping && page_count(page) == 1) {
1033                                 unlock_page(page);
1034                                 if (put_page_testzero(page))
1035                                         goto free_it;
1036                                 else {
1037                                         /*
1038                                          * rare race with speculative reference.
1039                                          * the speculative reference will free
1040                                          * this page shortly, so we may
1041                                          * increment nr_reclaimed here (and
1042                                          * leave it off the LRU).
1043                                          */
1044                                         nr_reclaimed++;
1045                                         continue;
1046                                 }
1047                         }
1048                 }
1049
1050                 if (!mapping || !__remove_mapping(mapping, page))
1051                         goto keep_locked;
1052
1053                 /*
1054                  * At this point, we have no other references and there is
1055                  * no way to pick any more up (removed from LRU, removed
1056                  * from pagecache). Can use non-atomic bitops now (and
1057                  * we obviously don't have to worry about waking up a process
1058                  * waiting on the page lock, because there are no references.
1059                  */
1060                 __clear_page_locked(page);
1061 free_it:
1062                 nr_reclaimed++;
1063
1064                 /*
1065                  * Is there need to periodically free_page_list? It would
1066                  * appear not as the counts should be low
1067                  */
1068                 list_add(&page->lru, &free_pages);
1069                 continue;
1070
1071 cull_mlocked:
1072                 if (PageSwapCache(page))
1073                         try_to_free_swap(page);
1074                 unlock_page(page);
1075                 putback_lru_page(page);
1076                 continue;
1077
1078 activate_locked:
1079                 /* Not a candidate for swapping, so reclaim swap space. */
1080                 if (PageSwapCache(page) && vm_swap_full())
1081                         try_to_free_swap(page);
1082                 VM_BUG_ON(PageActive(page));
1083                 SetPageActive(page);
1084                 pgactivate++;
1085 keep_locked:
1086                 unlock_page(page);
1087 keep:
1088                 list_add(&page->lru, &ret_pages);
1089                 VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
1090         }
1091
1092         free_hot_cold_page_list(&free_pages, 1);
1093
1094         list_splice(&ret_pages, page_list);
1095         count_vm_events(PGACTIVATE, pgactivate);
1096         mem_cgroup_uncharge_end();
1097         *ret_nr_dirty += nr_dirty;
1098         *ret_nr_congested += nr_congested;
1099         *ret_nr_unqueued_dirty += nr_unqueued_dirty;
1100         *ret_nr_writeback += nr_writeback;
1101         *ret_nr_immediate += nr_immediate;
1102         return nr_reclaimed;
1103 }
1104
1105 unsigned long reclaim_clean_pages_from_list(struct zone *zone,
1106                                             struct list_head *page_list)
1107 {
1108         struct scan_control sc = {
1109                 .gfp_mask = GFP_KERNEL,
1110                 .priority = DEF_PRIORITY,
1111                 .may_unmap = 1,
1112         };
1113         unsigned long ret, dummy1, dummy2, dummy3, dummy4, dummy5;
1114         struct page *page, *next;
1115         LIST_HEAD(clean_pages);
1116
1117         list_for_each_entry_safe(page, next, page_list, lru) {
1118                 if (page_is_file_cache(page) && !PageDirty(page) &&
1119                     !isolated_balloon_page(page)) {
1120                         ClearPageActive(page);
1121                         list_move(&page->lru, &clean_pages);
1122                 }
1123         }
1124
1125         ret = shrink_page_list(&clean_pages, zone, &sc,
1126                         TTU_UNMAP|TTU_IGNORE_ACCESS,
1127                         &dummy1, &dummy2, &dummy3, &dummy4, &dummy5, true);
1128         list_splice(&clean_pages, page_list);
1129         __mod_zone_page_state(zone, NR_ISOLATED_FILE, -ret);
1130         return ret;
1131 }
1132
1133 /*
1134  * Attempt to remove the specified page from its LRU.  Only take this page
1135  * if it is of the appropriate PageActive status.  Pages which are being
1136  * freed elsewhere are also ignored.
1137  *
1138  * page:        page to consider
1139  * mode:        one of the LRU isolation modes defined above
1140  *
1141  * returns 0 on success, -ve errno on failure.
1142  */
1143 int __isolate_lru_page(struct page *page, isolate_mode_t mode)
1144 {
1145         int ret = -EINVAL;
1146
1147         /* Only take pages on the LRU. */
1148         if (!PageLRU(page))
1149                 return ret;
1150
1151         /* Compaction should not handle unevictable pages but CMA can do so */
1152         if (PageUnevictable(page) && !(mode & ISOLATE_UNEVICTABLE))
1153                 return ret;
1154
1155         ret = -EBUSY;
1156
1157         /*
1158          * To minimise LRU disruption, the caller can indicate that it only
1159          * wants to isolate pages it will be able to operate on without
1160          * blocking - clean pages for the most part.
1161          *
1162          * ISOLATE_CLEAN means that only clean pages should be isolated. This
1163          * is used by reclaim when it is cannot write to backing storage
1164          *
1165          * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages
1166          * that it is possible to migrate without blocking
1167          */
1168         if (mode & (ISOLATE_CLEAN|ISOLATE_ASYNC_MIGRATE)) {
1169                 /* All the caller can do on PageWriteback is block */
1170                 if (PageWriteback(page))
1171                         return ret;
1172
1173                 if (PageDirty(page)) {
1174                         struct address_space *mapping;
1175
1176                         /* ISOLATE_CLEAN means only clean pages */
1177                         if (mode & ISOLATE_CLEAN)
1178                                 return ret;
1179
1180                         /*
1181                          * Only pages without mappings or that have a
1182                          * ->migratepage callback are possible to migrate
1183                          * without blocking
1184                          */
1185                         mapping = page_mapping(page);
1186                         if (mapping && !mapping->a_ops->migratepage)
1187                                 return ret;
1188                 }
1189         }
1190
1191         if ((mode & ISOLATE_UNMAPPED) && page_mapped(page))
1192                 return ret;
1193
1194         if (likely(get_page_unless_zero(page))) {
1195                 /*
1196                  * Be careful not to clear PageLRU until after we're
1197                  * sure the page is not being freed elsewhere -- the
1198                  * page release code relies on it.
1199                  */
1200                 ClearPageLRU(page);
1201                 ret = 0;
1202         }
1203
1204         return ret;
1205 }
1206
1207 /*
1208  * zone->lru_lock is heavily contended.  Some of the functions that
1209  * shrink the lists perform better by taking out a batch of pages
1210  * and working on them outside the LRU lock.
1211  *
1212  * For pagecache intensive workloads, this function is the hottest
1213  * spot in the kernel (apart from copy_*_user functions).
1214  *
1215  * Appropriate locks must be held before calling this function.
1216  *
1217  * @nr_to_scan: The number of pages to look through on the list.
1218  * @lruvec:     The LRU vector to pull pages from.
1219  * @dst:        The temp list to put pages on to.
1220  * @nr_scanned: The number of pages that were scanned.
1221  * @sc:         The scan_control struct for this reclaim session
1222  * @mode:       One of the LRU isolation modes
1223  * @lru:        LRU list id for isolating
1224  *
1225  * returns how many pages were moved onto *@dst.
1226  */
1227 static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
1228                 struct lruvec *lruvec, struct list_head *dst,
1229                 unsigned long *nr_scanned, struct scan_control *sc,
1230                 isolate_mode_t mode, enum lru_list lru)
1231 {
1232         struct list_head *src = &lruvec->lists[lru];
1233         unsigned long nr_taken = 0;
1234         unsigned long scan;
1235
1236         for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
1237                 struct page *page;
1238                 int nr_pages;
1239
1240                 page = lru_to_page(src);
1241                 prefetchw_prev_lru_page(page, src, flags);
1242
1243                 VM_BUG_ON(!PageLRU(page));
1244
1245                 switch (__isolate_lru_page(page, mode)) {
1246                 case 0:
1247                         nr_pages = hpage_nr_pages(page);
1248                         mem_cgroup_update_lru_size(lruvec, lru, -nr_pages);
1249                         list_move(&page->lru, dst);
1250                         nr_taken += nr_pages;
1251                         break;
1252
1253                 case -EBUSY:
1254                         /* else it is being freed elsewhere */
1255                         list_move(&page->lru, src);
1256                         continue;
1257
1258                 default:
1259                         BUG();
1260                 }
1261         }
1262
1263         *nr_scanned = scan;
1264         trace_mm_vmscan_lru_isolate(sc->order, nr_to_scan, scan,
1265                                     nr_taken, mode, is_file_lru(lru));
1266         return nr_taken;
1267 }
1268
1269 /**
1270  * isolate_lru_page - tries to isolate a page from its LRU list
1271  * @page: page to isolate from its LRU list
1272  *
1273  * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1274  * vmstat statistic corresponding to whatever LRU list the page was on.
1275  *
1276  * Returns 0 if the page was removed from an LRU list.
1277  * Returns -EBUSY if the page was not on an LRU list.
1278  *
1279  * The returned page will have PageLRU() cleared.  If it was found on
1280  * the active list, it will have PageActive set.  If it was found on
1281  * the unevictable list, it will have the PageUnevictable bit set. That flag
1282  * may need to be cleared by the caller before letting the page go.
1283  *
1284  * The vmstat statistic corresponding to the list on which the page was
1285  * found will be decremented.
1286  *
1287  * Restrictions:
1288  * (1) Must be called with an elevated refcount on the page. This is a
1289  *     fundamentnal difference from isolate_lru_pages (which is called
1290  *     without a stable reference).
1291  * (2) the lru_lock must not be held.
1292  * (3) interrupts must be enabled.
1293  */
1294 int isolate_lru_page(struct page *page)
1295 {
1296         int ret = -EBUSY;
1297
1298         VM_BUG_ON(!page_count(page));
1299
1300         if (PageLRU(page)) {
1301                 struct zone *zone = page_zone(page);
1302                 struct lruvec *lruvec;
1303
1304                 spin_lock_irq(&zone->lru_lock);
1305                 lruvec = mem_cgroup_page_lruvec(page, zone);
1306                 if (PageLRU(page)) {
1307                         int lru = page_lru(page);
1308                         get_page(page);
1309                         ClearPageLRU(page);
1310                         del_page_from_lru_list(page, lruvec, lru);
1311                         ret = 0;
1312                 }
1313                 spin_unlock_irq(&zone->lru_lock);
1314         }
1315         return ret;
1316 }
1317
1318 /*
1319  * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and
1320  * then get resheduled. When there are massive number of tasks doing page
1321  * allocation, such sleeping direct reclaimers may keep piling up on each CPU,
1322  * the LRU list will go small and be scanned faster than necessary, leading to
1323  * unnecessary swapping, thrashing and OOM.
1324  */
1325 static int too_many_isolated(struct zone *zone, int file,
1326                 struct scan_control *sc)
1327 {
1328         unsigned long inactive, isolated;
1329
1330         if (current_is_kswapd())
1331                 return 0;
1332
1333         if (!global_reclaim(sc))
1334                 return 0;
1335
1336         if (file) {
1337                 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1338                 isolated = zone_page_state(zone, NR_ISOLATED_FILE);
1339         } else {
1340                 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1341                 isolated = zone_page_state(zone, NR_ISOLATED_ANON);
1342         }
1343
1344         /*
1345          * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they
1346          * won't get blocked by normal direct-reclaimers, forming a circular
1347          * deadlock.
1348          */
1349         if ((sc->gfp_mask & GFP_IOFS) == GFP_IOFS)
1350                 inactive >>= 3;
1351
1352         return isolated > inactive;
1353 }
1354
1355 static noinline_for_stack void
1356 putback_inactive_pages(struct lruvec *lruvec, struct list_head *page_list)
1357 {
1358         struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
1359         struct zone *zone = lruvec_zone(lruvec);
1360         LIST_HEAD(pages_to_free);
1361
1362         /*
1363          * Put back any unfreeable pages.
1364          */
1365         while (!list_empty(page_list)) {
1366                 struct page *page = lru_to_page(page_list);
1367                 int lru;
1368
1369                 VM_BUG_ON(PageLRU(page));
1370                 list_del(&page->lru);
1371                 if (unlikely(!page_evictable(page))) {
1372                         spin_unlock_irq(&zone->lru_lock);
1373                         putback_lru_page(page);
1374                         spin_lock_irq(&zone->lru_lock);
1375                         continue;
1376                 }
1377
1378                 lruvec = mem_cgroup_page_lruvec(page, zone);
1379
1380                 SetPageLRU(page);
1381                 lru = page_lru(page);
1382                 add_page_to_lru_list(page, lruvec, lru);
1383
1384                 if (is_active_lru(lru)) {
1385                         int file = is_file_lru(lru);
1386                         int numpages = hpage_nr_pages(page);
1387                         reclaim_stat->recent_rotated[file] += numpages;
1388                 }
1389                 if (put_page_testzero(page)) {
1390                         __ClearPageLRU(page);
1391                         __ClearPageActive(page);
1392                         del_page_from_lru_list(page, lruvec, lru);
1393
1394                         if (unlikely(PageCompound(page))) {
1395                                 spin_unlock_irq(&zone->lru_lock);
1396                                 (*get_compound_page_dtor(page))(page);
1397                                 spin_lock_irq(&zone->lru_lock);
1398                         } else
1399                                 list_add(&page->lru, &pages_to_free);
1400                 }
1401         }
1402
1403         /*
1404          * To save our caller's stack, now use input list for pages to free.
1405          */
1406         list_splice(&pages_to_free, page_list);
1407 }
1408
1409 /*
1410  * shrink_inactive_list() is a helper for shrink_zone().  It returns the number
1411  * of reclaimed pages
1412  */
1413 static noinline_for_stack unsigned long
1414 shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
1415                      struct scan_control *sc, enum lru_list lru)
1416 {
1417         LIST_HEAD(page_list);
1418         unsigned long nr_scanned;
1419         unsigned long nr_reclaimed = 0;
1420         unsigned long nr_taken;
1421         unsigned long nr_dirty = 0;
1422         unsigned long nr_congested = 0;
1423         unsigned long nr_unqueued_dirty = 0;
1424         unsigned long nr_writeback = 0;
1425         unsigned long nr_immediate = 0;
1426         isolate_mode_t isolate_mode = 0;
1427         int file = is_file_lru(lru);
1428         struct zone *zone = lruvec_zone(lruvec);
1429         struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
1430
1431         while (unlikely(too_many_isolated(zone, file, sc))) {
1432                 congestion_wait(BLK_RW_ASYNC, HZ/10);
1433
1434                 /* We are about to die and free our memory. Return now. */
1435                 if (fatal_signal_pending(current))
1436                         return SWAP_CLUSTER_MAX;
1437         }
1438
1439         lru_add_drain();
1440
1441         if (!sc->may_unmap)
1442                 isolate_mode |= ISOLATE_UNMAPPED;
1443         if (!sc->may_writepage)
1444                 isolate_mode |= ISOLATE_CLEAN;
1445
1446         spin_lock_irq(&zone->lru_lock);
1447
1448         nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &page_list,
1449                                      &nr_scanned, sc, isolate_mode, lru);
1450
1451         __mod_zone_page_state(zone, NR_LRU_BASE + lru, -nr_taken);
1452         __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
1453
1454         if (global_reclaim(sc)) {
1455                 zone->pages_scanned += nr_scanned;
1456                 if (current_is_kswapd())
1457                         __count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scanned);
1458                 else
1459                         __count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scanned);
1460         }
1461         spin_unlock_irq(&zone->lru_lock);
1462
1463         if (nr_taken == 0)
1464                 return 0;
1465
1466         nr_reclaimed = shrink_page_list(&page_list, zone, sc, TTU_UNMAP,
1467                                 &nr_dirty, &nr_unqueued_dirty, &nr_congested,
1468                                 &nr_writeback, &nr_immediate,
1469                                 false);
1470
1471         spin_lock_irq(&zone->lru_lock);
1472
1473         reclaim_stat->recent_scanned[file] += nr_taken;
1474
1475         if (global_reclaim(sc)) {
1476                 if (current_is_kswapd())
1477                         __count_zone_vm_events(PGSTEAL_KSWAPD, zone,
1478                                                nr_reclaimed);
1479                 else
1480                         __count_zone_vm_events(PGSTEAL_DIRECT, zone,
1481                                                nr_reclaimed);
1482         }
1483
1484         putback_inactive_pages(lruvec, &page_list);
1485
1486         __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1487
1488         spin_unlock_irq(&zone->lru_lock);
1489
1490         free_hot_cold_page_list(&page_list, 1);
1491
1492         /*
1493          * If reclaim is isolating dirty pages under writeback, it implies
1494          * that the long-lived page allocation rate is exceeding the page
1495          * laundering rate. Either the global limits are not being effective
1496          * at throttling processes due to the page distribution throughout
1497          * zones or there is heavy usage of a slow backing device. The
1498          * only option is to throttle from reclaim context which is not ideal
1499          * as there is no guarantee the dirtying process is throttled in the
1500          * same way balance_dirty_pages() manages.
1501          *
1502          * Once a zone is flagged ZONE_WRITEBACK, kswapd will count the number
1503          * of pages under pages flagged for immediate reclaim and stall if any
1504          * are encountered in the nr_immediate check below.
1505          */
1506         if (nr_writeback && nr_writeback == nr_taken)
1507                 zone_set_flag(zone, ZONE_WRITEBACK);
1508
1509         /*
1510          * memcg will stall in page writeback so only consider forcibly
1511          * stalling for global reclaim
1512          */
1513         if (global_reclaim(sc)) {
1514                 /*
1515                  * Tag a zone as congested if all the dirty pages scanned were
1516                  * backed by a congested BDI and wait_iff_congested will stall.
1517                  */
1518                 if (nr_dirty && nr_dirty == nr_congested)
1519                         zone_set_flag(zone, ZONE_CONGESTED);
1520
1521                 /*
1522                  * If dirty pages are scanned that are not queued for IO, it
1523                  * implies that flushers are not keeping up. In this case, flag
1524                  * the zone ZONE_TAIL_LRU_DIRTY and kswapd will start writing
1525                  * pages from reclaim context. It will forcibly stall in the
1526                  * next check.
1527                  */
1528                 if (nr_unqueued_dirty == nr_taken)
1529                         zone_set_flag(zone, ZONE_TAIL_LRU_DIRTY);
1530
1531                 /*
1532                  * In addition, if kswapd scans pages marked marked for
1533                  * immediate reclaim and under writeback (nr_immediate), it
1534                  * implies that pages are cycling through the LRU faster than
1535                  * they are written so also forcibly stall.
1536                  */
1537                 if (nr_unqueued_dirty == nr_taken || nr_immediate)
1538                         congestion_wait(BLK_RW_ASYNC, HZ/10);
1539         }
1540
1541         /*
1542          * Stall direct reclaim for IO completions if underlying BDIs or zone
1543          * is congested. Allow kswapd to continue until it starts encountering
1544          * unqueued dirty pages or cycling through the LRU too quickly.
1545          */
1546         if (!sc->hibernation_mode && !current_is_kswapd())
1547                 wait_iff_congested(zone, BLK_RW_ASYNC, HZ/10);
1548
1549         trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id,
1550                 zone_idx(zone),
1551                 nr_scanned, nr_reclaimed,
1552                 sc->priority,
1553                 trace_shrink_flags(file));
1554         return nr_reclaimed;
1555 }
1556
1557 /*
1558  * This moves pages from the active list to the inactive list.
1559  *
1560  * We move them the other way if the page is referenced by one or more
1561  * processes, from rmap.
1562  *
1563  * If the pages are mostly unmapped, the processing is fast and it is
1564  * appropriate to hold zone->lru_lock across the whole operation.  But if
1565  * the pages are mapped, the processing is slow (page_referenced()) so we
1566  * should drop zone->lru_lock around each page.  It's impossible to balance
1567  * this, so instead we remove the pages from the LRU while processing them.
1568  * It is safe to rely on PG_active against the non-LRU pages in here because
1569  * nobody will play with that bit on a non-LRU page.
1570  *
1571  * The downside is that we have to touch page->_count against each page.
1572  * But we had to alter page->flags anyway.
1573  */
1574
1575 static void move_active_pages_to_lru(struct lruvec *lruvec,
1576                                      struct list_head *list,
1577                                      struct list_head *pages_to_free,
1578                                      enum lru_list lru)
1579 {
1580         struct zone *zone = lruvec_zone(lruvec);
1581         unsigned long pgmoved = 0;
1582         struct page *page;
1583         int nr_pages;
1584
1585         while (!list_empty(list)) {
1586                 page = lru_to_page(list);
1587                 lruvec = mem_cgroup_page_lruvec(page, zone);
1588
1589                 VM_BUG_ON(PageLRU(page));
1590                 SetPageLRU(page);
1591
1592                 nr_pages = hpage_nr_pages(page);
1593                 mem_cgroup_update_lru_size(lruvec, lru, nr_pages);
1594                 list_move(&page->lru, &lruvec->lists[lru]);
1595                 pgmoved += nr_pages;
1596
1597                 if (put_page_testzero(page)) {
1598                         __ClearPageLRU(page);
1599                         __ClearPageActive(page);
1600                         del_page_from_lru_list(page, lruvec, lru);
1601
1602                         if (unlikely(PageCompound(page))) {
1603                                 spin_unlock_irq(&zone->lru_lock);
1604                                 (*get_compound_page_dtor(page))(page);
1605                                 spin_lock_irq(&zone->lru_lock);
1606                         } else
1607                                 list_add(&page->lru, pages_to_free);
1608                 }
1609         }
1610         __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1611         if (!is_active_lru(lru))
1612                 __count_vm_events(PGDEACTIVATE, pgmoved);
1613 }
1614
1615 static void shrink_active_list(unsigned long nr_to_scan,
1616                                struct lruvec *lruvec,
1617                                struct scan_control *sc,
1618                                enum lru_list lru)
1619 {
1620         unsigned long nr_taken;
1621         unsigned long nr_scanned;
1622         unsigned long vm_flags;
1623         LIST_HEAD(l_hold);      /* The pages which were snipped off */
1624         LIST_HEAD(l_active);
1625         LIST_HEAD(l_inactive);
1626         struct page *page;
1627         struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
1628         unsigned long nr_rotated = 0;
1629         isolate_mode_t isolate_mode = 0;
1630         int file = is_file_lru(lru);
1631         struct zone *zone = lruvec_zone(lruvec);
1632
1633         lru_add_drain();
1634
1635         if (!sc->may_unmap)
1636                 isolate_mode |= ISOLATE_UNMAPPED;
1637         if (!sc->may_writepage)
1638                 isolate_mode |= ISOLATE_CLEAN;
1639
1640         spin_lock_irq(&zone->lru_lock);
1641
1642         nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &l_hold,
1643                                      &nr_scanned, sc, isolate_mode, lru);
1644         if (global_reclaim(sc))
1645                 zone->pages_scanned += nr_scanned;
1646
1647         reclaim_stat->recent_scanned[file] += nr_taken;
1648
1649         __count_zone_vm_events(PGREFILL, zone, nr_scanned);
1650         __mod_zone_page_state(zone, NR_LRU_BASE + lru, -nr_taken);
1651         __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
1652         spin_unlock_irq(&zone->lru_lock);
1653
1654         while (!list_empty(&l_hold)) {
1655                 cond_resched();
1656                 page = lru_to_page(&l_hold);
1657                 list_del(&page->lru);
1658
1659                 if (unlikely(!page_evictable(page))) {
1660                         putback_lru_page(page);
1661                         continue;
1662                 }
1663
1664                 if (unlikely(buffer_heads_over_limit)) {
1665                         if (page_has_private(page) && trylock_page(page)) {
1666                                 if (page_has_private(page))
1667                                         try_to_release_page(page, 0);
1668                                 unlock_page(page);
1669                         }
1670                 }
1671
1672                 if (page_referenced(page, 0, sc->target_mem_cgroup,
1673                                     &vm_flags)) {
1674                         nr_rotated += hpage_nr_pages(page);
1675                         /*
1676                          * Identify referenced, file-backed active pages and
1677                          * give them one more trip around the active list. So
1678                          * that executable code get better chances to stay in
1679                          * memory under moderate memory pressure.  Anon pages
1680                          * are not likely to be evicted by use-once streaming
1681                          * IO, plus JVM can create lots of anon VM_EXEC pages,
1682                          * so we ignore them here.
1683                          */
1684                         if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
1685                                 list_add(&page->lru, &l_active);
1686                                 continue;
1687                         }
1688                 }
1689
1690                 ClearPageActive(page);  /* we are de-activating */
1691                 list_add(&page->lru, &l_inactive);
1692         }
1693
1694         /*
1695          * Move pages back to the lru list.
1696          */
1697         spin_lock_irq(&zone->lru_lock);
1698         /*
1699          * Count referenced pages from currently used mappings as rotated,
1700          * even though only some of them are actually re-activated.  This
1701          * helps balance scan pressure between file and anonymous pages in
1702          * get_scan_ratio.
1703          */
1704         reclaim_stat->recent_rotated[file] += nr_rotated;
1705
1706         move_active_pages_to_lru(lruvec, &l_active, &l_hold, lru);
1707         move_active_pages_to_lru(lruvec, &l_inactive, &l_hold, lru - LRU_ACTIVE);
1708         __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1709         spin_unlock_irq(&zone->lru_lock);
1710
1711         free_hot_cold_page_list(&l_hold, 1);
1712 }
1713
1714 #ifdef CONFIG_SWAP
1715 static int inactive_anon_is_low_global(struct zone *zone)
1716 {
1717         unsigned long active, inactive;
1718
1719         active = zone_page_state(zone, NR_ACTIVE_ANON);
1720         inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1721
1722         if (inactive * zone->inactive_ratio < active)
1723                 return 1;
1724
1725         return 0;
1726 }
1727
1728 /**
1729  * inactive_anon_is_low - check if anonymous pages need to be deactivated
1730  * @lruvec: LRU vector to check
1731  *
1732  * Returns true if the zone does not have enough inactive anon pages,
1733  * meaning some active anon pages need to be deactivated.
1734  */
1735 static int inactive_anon_is_low(struct lruvec *lruvec)
1736 {
1737         /*
1738          * If we don't have swap space, anonymous page deactivation
1739          * is pointless.
1740          */
1741         if (!total_swap_pages)
1742                 return 0;
1743
1744         if (!mem_cgroup_disabled())
1745                 return mem_cgroup_inactive_anon_is_low(lruvec);
1746
1747         return inactive_anon_is_low_global(lruvec_zone(lruvec));
1748 }
1749 #else
1750 static inline int inactive_anon_is_low(struct lruvec *lruvec)
1751 {
1752         return 0;
1753 }
1754 #endif
1755
1756 /**
1757  * inactive_file_is_low - check if file pages need to be deactivated
1758  * @lruvec: LRU vector to check
1759  *
1760  * When the system is doing streaming IO, memory pressure here
1761  * ensures that active file pages get deactivated, until more
1762  * than half of the file pages are on the inactive list.
1763  *
1764  * Once we get to that situation, protect the system's working
1765  * set from being evicted by disabling active file page aging.
1766  *
1767  * This uses a different ratio than the anonymous pages, because
1768  * the page cache uses a use-once replacement algorithm.
1769  */
1770 static int inactive_file_is_low(struct lruvec *lruvec)
1771 {
1772         unsigned long inactive;
1773         unsigned long active;
1774
1775         inactive = get_lru_size(lruvec, LRU_INACTIVE_FILE);
1776         active = get_lru_size(lruvec, LRU_ACTIVE_FILE);
1777
1778         return active > inactive;
1779 }
1780
1781 static int inactive_list_is_low(struct lruvec *lruvec, enum lru_list lru)
1782 {
1783         if (is_file_lru(lru))
1784                 return inactive_file_is_low(lruvec);
1785         else
1786                 return inactive_anon_is_low(lruvec);
1787 }
1788
1789 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1790                                  struct lruvec *lruvec, struct scan_control *sc)
1791 {
1792         if (is_active_lru(lru)) {
1793                 if (inactive_list_is_low(lruvec, lru))
1794                         shrink_active_list(nr_to_scan, lruvec, sc, lru);
1795                 return 0;
1796         }
1797
1798         return shrink_inactive_list(nr_to_scan, lruvec, sc, lru);
1799 }
1800
1801 static int vmscan_swappiness(struct scan_control *sc)
1802 {
1803         if (global_reclaim(sc))
1804                 return vm_swappiness;
1805         return mem_cgroup_swappiness(sc->target_mem_cgroup);
1806 }
1807
1808 enum scan_balance {
1809         SCAN_EQUAL,
1810         SCAN_FRACT,
1811         SCAN_ANON,
1812         SCAN_FILE,
1813 };
1814
1815 /*
1816  * Determine how aggressively the anon and file LRU lists should be
1817  * scanned.  The relative value of each set of LRU lists is determined
1818  * by looking at the fraction of the pages scanned we did rotate back
1819  * onto the active list instead of evict.
1820  *
1821  * nr[0] = anon inactive pages to scan; nr[1] = anon active pages to scan
1822  * nr[2] = file inactive pages to scan; nr[3] = file active pages to scan
1823  */
1824 static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
1825                            unsigned long *nr)
1826 {
1827         struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
1828         u64 fraction[2];
1829         u64 denominator = 0;    /* gcc */
1830         struct zone *zone = lruvec_zone(lruvec);
1831         unsigned long anon_prio, file_prio;
1832         enum scan_balance scan_balance;
1833         unsigned long anon, file, free;
1834         bool force_scan = false;
1835         unsigned long ap, fp;
1836         enum lru_list lru;
1837
1838         /*
1839          * If the zone or memcg is small, nr[l] can be 0.  This
1840          * results in no scanning on this priority and a potential
1841          * priority drop.  Global direct reclaim can go to the next
1842          * zone and tends to have no problems. Global kswapd is for
1843          * zone balancing and it needs to scan a minimum amount. When
1844          * reclaiming for a memcg, a priority drop can cause high
1845          * latencies, so it's better to scan a minimum amount there as
1846          * well.
1847          */
1848         if (current_is_kswapd() && !zone_reclaimable(zone))
1849                 force_scan = true;
1850         if (!global_reclaim(sc))
1851                 force_scan = true;
1852
1853         /* If we have no swap space, do not bother scanning anon pages. */
1854         if (!sc->may_swap || (get_nr_swap_pages() <= 0)) {
1855                 scan_balance = SCAN_FILE;
1856                 goto out;
1857         }
1858
1859         /*
1860          * Global reclaim will swap to prevent OOM even with no
1861          * swappiness, but memcg users want to use this knob to
1862          * disable swapping for individual groups completely when
1863          * using the memory controller's swap limit feature would be
1864          * too expensive.
1865          */
1866         if (!global_reclaim(sc) && !vmscan_swappiness(sc)) {
1867                 scan_balance = SCAN_FILE;
1868                 goto out;
1869         }
1870
1871         /*
1872          * Do not apply any pressure balancing cleverness when the
1873          * system is close to OOM, scan both anon and file equally
1874          * (unless the swappiness setting disagrees with swapping).
1875          */
1876         if (!sc->priority && vmscan_swappiness(sc)) {
1877                 scan_balance = SCAN_EQUAL;
1878                 goto out;
1879         }
1880
1881         anon  = get_lru_size(lruvec, LRU_ACTIVE_ANON) +
1882                 get_lru_size(lruvec, LRU_INACTIVE_ANON);
1883         file  = get_lru_size(lruvec, LRU_ACTIVE_FILE) +
1884                 get_lru_size(lruvec, LRU_INACTIVE_FILE);
1885
1886         /*
1887          * If it's foreseeable that reclaiming the file cache won't be
1888          * enough to get the zone back into a desirable shape, we have
1889          * to swap.  Better start now and leave the - probably heavily
1890          * thrashing - remaining file pages alone.
1891          */
1892         if (global_reclaim(sc)) {
1893                 free = zone_page_state(zone, NR_FREE_PAGES);
1894                 if (unlikely(file + free <= high_wmark_pages(zone))) {
1895                         scan_balance = SCAN_ANON;
1896                         goto out;
1897                 }
1898         }
1899
1900         /*
1901          * There is enough inactive page cache, do not reclaim
1902          * anything from the anonymous working set right now.
1903          */
1904         if (!inactive_file_is_low(lruvec)) {
1905                 scan_balance = SCAN_FILE;
1906                 goto out;
1907         }
1908
1909         scan_balance = SCAN_FRACT;
1910
1911         /*
1912          * With swappiness at 100, anonymous and file have the same priority.
1913          * This scanning priority is essentially the inverse of IO cost.
1914          */
1915         anon_prio = vmscan_swappiness(sc);
1916         file_prio = 200 - anon_prio;
1917
1918         /*
1919          * OK, so we have swap space and a fair amount of page cache
1920          * pages.  We use the recently rotated / recently scanned
1921          * ratios to determine how valuable each cache is.
1922          *
1923          * Because workloads change over time (and to avoid overflow)
1924          * we keep these statistics as a floating average, which ends
1925          * up weighing recent references more than old ones.
1926          *
1927          * anon in [0], file in [1]
1928          */
1929         spin_lock_irq(&zone->lru_lock);
1930         if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
1931                 reclaim_stat->recent_scanned[0] /= 2;
1932                 reclaim_stat->recent_rotated[0] /= 2;
1933         }
1934
1935         if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
1936                 reclaim_stat->recent_scanned[1] /= 2;
1937                 reclaim_stat->recent_rotated[1] /= 2;
1938         }
1939
1940         /*
1941          * The amount of pressure on anon vs file pages is inversely
1942          * proportional to the fraction of recently scanned pages on
1943          * each list that were recently referenced and in active use.
1944          */
1945         ap = anon_prio * (reclaim_stat->recent_scanned[0] + 1);
1946         ap /= reclaim_stat->recent_rotated[0] + 1;
1947
1948         fp = file_prio * (reclaim_stat->recent_scanned[1] + 1);
1949         fp /= reclaim_stat->recent_rotated[1] + 1;
1950         spin_unlock_irq(&zone->lru_lock);
1951
1952         fraction[0] = ap;
1953         fraction[1] = fp;
1954         denominator = ap + fp + 1;
1955 out:
1956         for_each_evictable_lru(lru) {
1957                 int file = is_file_lru(lru);
1958                 unsigned long size;
1959                 unsigned long scan;
1960
1961                 size = get_lru_size(lruvec, lru);
1962                 scan = size >> sc->priority;
1963
1964                 if (!scan && force_scan)
1965                         scan = min(size, SWAP_CLUSTER_MAX);
1966
1967                 switch (scan_balance) {
1968                 case SCAN_EQUAL:
1969                         /* Scan lists relative to size */
1970                         break;
1971                 case SCAN_FRACT:
1972                         /*
1973                          * Scan types proportional to swappiness and
1974                          * their relative recent reclaim efficiency.
1975                          */
1976                         scan = div64_u64(scan * fraction[file], denominator);
1977                         break;
1978                 case SCAN_FILE:
1979                 case SCAN_ANON:
1980                         /* Scan one type exclusively */
1981                         if ((scan_balance == SCAN_FILE) != file)
1982                                 scan = 0;
1983                         break;
1984                 default:
1985                         /* Look ma, no brain */
1986                         BUG();
1987                 }
1988                 nr[lru] = scan;
1989         }
1990 }
1991
1992 /*
1993  * This is a basic per-zone page freer.  Used by both kswapd and direct reclaim.
1994  */
1995 static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
1996 {
1997         unsigned long nr[NR_LRU_LISTS];
1998         unsigned long targets[NR_LRU_LISTS];
1999         unsigned long nr_to_scan;
2000         enum lru_list lru;
2001         unsigned long nr_reclaimed = 0;
2002         unsigned long nr_to_reclaim = sc->nr_to_reclaim;
2003         struct blk_plug plug;
2004         bool scan_adjusted = false;
2005
2006         get_scan_count(lruvec, sc, nr);
2007
2008         /* Record the original scan target for proportional adjustments later */
2009         memcpy(targets, nr, sizeof(nr));
2010
2011         blk_start_plug(&plug);
2012         while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
2013                                         nr[LRU_INACTIVE_FILE]) {
2014                 unsigned long nr_anon, nr_file, percentage;
2015                 unsigned long nr_scanned;
2016
2017                 for_each_evictable_lru(lru) {
2018                         if (nr[lru]) {
2019                                 nr_to_scan = min(nr[lru], SWAP_CLUSTER_MAX);
2020                                 nr[lru] -= nr_to_scan;
2021
2022                                 nr_reclaimed += shrink_list(lru, nr_to_scan,
2023                                                             lruvec, sc);
2024                         }
2025                 }
2026
2027                 if (nr_reclaimed < nr_to_reclaim || scan_adjusted)
2028                         continue;
2029
2030                 /*
2031                  * For global direct reclaim, reclaim only the number of pages
2032                  * requested. Less care is taken to scan proportionally as it
2033                  * is more important to minimise direct reclaim stall latency
2034                  * than it is to properly age the LRU lists.
2035                  */
2036                 if (global_reclaim(sc) && !current_is_kswapd())
2037                         break;
2038
2039                 /*
2040                  * For kswapd and memcg, reclaim at least the number of pages
2041                  * requested. Ensure that the anon and file LRUs shrink
2042                  * proportionally what was requested by get_scan_count(). We
2043                  * stop reclaiming one LRU and reduce the amount scanning
2044                  * proportional to the original scan target.
2045                  */
2046                 nr_file = nr[LRU_INACTIVE_FILE] + nr[LRU_ACTIVE_FILE];
2047                 nr_anon = nr[LRU_INACTIVE_ANON] + nr[LRU_ACTIVE_ANON];
2048
2049                 if (nr_file > nr_anon) {
2050                         unsigned long scan_target = targets[LRU_INACTIVE_ANON] +
2051                                                 targets[LRU_ACTIVE_ANON] + 1;
2052                         lru = LRU_BASE;
2053                         percentage = nr_anon * 100 / scan_target;
2054                 } else {
2055                         unsigned long scan_target = targets[LRU_INACTIVE_FILE] +
2056                                                 targets[LRU_ACTIVE_FILE] + 1;
2057                         lru = LRU_FILE;
2058                         percentage = nr_file * 100 / scan_target;
2059                 }
2060
2061                 /* Stop scanning the smaller of the LRU */
2062                 nr[lru] = 0;
2063                 nr[lru + LRU_ACTIVE] = 0;
2064
2065                 /*
2066                  * Recalculate the other LRU scan count based on its original
2067                  * scan target and the percentage scanning already complete
2068                  */
2069                 lru = (lru == LRU_FILE) ? LRU_BASE : LRU_FILE;
2070                 nr_scanned = targets[lru] - nr[lru];
2071                 nr[lru] = targets[lru] * (100 - percentage) / 100;
2072                 nr[lru] -= min(nr[lru], nr_scanned);
2073
2074                 lru += LRU_ACTIVE;
2075                 nr_scanned = targets[lru] - nr[lru];
2076                 nr[lru] = targets[lru] * (100 - percentage) / 100;
2077                 nr[lru] -= min(nr[lru], nr_scanned);
2078
2079                 scan_adjusted = true;
2080         }
2081         blk_finish_plug(&plug);
2082         sc->nr_reclaimed += nr_reclaimed;
2083
2084         /*
2085          * Even if we did not try to evict anon pages at all, we want to
2086          * rebalance the anon lru active/inactive ratio.
2087          */
2088         if (inactive_anon_is_low(lruvec))
2089                 shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
2090                                    sc, LRU_ACTIVE_ANON);
2091
2092         throttle_vm_writeout(sc->gfp_mask);
2093 }
2094
2095 /* Use reclaim/compaction for costly allocs or under memory pressure */
2096 static bool in_reclaim_compaction(struct scan_control *sc)
2097 {
2098         if (IS_ENABLED(CONFIG_COMPACTION) && sc->order &&
2099                         (sc->order > PAGE_ALLOC_COSTLY_ORDER ||
2100                          sc->priority < DEF_PRIORITY - 2))
2101                 return true;
2102
2103         return false;
2104 }
2105
2106 /*
2107  * Reclaim/compaction is used for high-order allocation requests. It reclaims
2108  * order-0 pages before compacting the zone. should_continue_reclaim() returns
2109  * true if more pages should be reclaimed such that when the page allocator
2110  * calls try_to_compact_zone() that it will have enough free pages to succeed.
2111  * It will give up earlier than that if there is difficulty reclaiming pages.
2112  */
2113 static inline bool should_continue_reclaim(struct zone *zone,
2114                                         unsigned long nr_reclaimed,
2115                                         unsigned long nr_scanned,
2116                                         struct scan_control *sc)
2117 {
2118         unsigned long pages_for_compaction;
2119         unsigned long inactive_lru_pages;
2120
2121         /* If not in reclaim/compaction mode, stop */
2122         if (!in_reclaim_compaction(sc))
2123                 return false;
2124
2125         /* Consider stopping depending on scan and reclaim activity */
2126         if (sc->gfp_mask & __GFP_REPEAT) {
2127                 /*
2128                  * For __GFP_REPEAT allocations, stop reclaiming if the
2129                  * full LRU list has been scanned and we are still failing
2130                  * to reclaim pages. This full LRU scan is potentially
2131                  * expensive but a __GFP_REPEAT caller really wants to succeed
2132                  */
2133                 if (!nr_reclaimed && !nr_scanned)
2134                         return false;
2135         } else {
2136                 /*
2137                  * For non-__GFP_REPEAT allocations which can presumably
2138                  * fail without consequence, stop if we failed to reclaim
2139                  * any pages from the last SWAP_CLUSTER_MAX number of
2140                  * pages that were scanned. This will return to the
2141                  * caller faster at the risk reclaim/compaction and
2142                  * the resulting allocation attempt fails
2143                  */
2144                 if (!nr_reclaimed)
2145                         return false;
2146         }
2147
2148         /*
2149          * If we have not reclaimed enough pages for compaction and the
2150          * inactive lists are large enough, continue reclaiming
2151          */
2152         pages_for_compaction = (2UL << sc->order);
2153         inactive_lru_pages = zone_page_state(zone, NR_INACTIVE_FILE);
2154         if (get_nr_swap_pages() > 0)
2155                 inactive_lru_pages += zone_page_state(zone, NR_INACTIVE_ANON);
2156         if (sc->nr_reclaimed < pages_for_compaction &&
2157                         inactive_lru_pages > pages_for_compaction)
2158                 return true;
2159
2160         /* If compaction would go ahead or the allocation would succeed, stop */
2161         switch (compaction_suitable(zone, sc->order)) {
2162         case COMPACT_PARTIAL:
2163         case COMPACT_CONTINUE:
2164                 return false;
2165         default:
2166                 return true;
2167         }
2168 }
2169
2170 static void shrink_zone(struct zone *zone, struct scan_control *sc)
2171 {
2172         unsigned long nr_reclaimed, nr_scanned;
2173
2174         do {
2175                 struct mem_cgroup *root = sc->target_mem_cgroup;
2176                 struct mem_cgroup_reclaim_cookie reclaim = {
2177                         .zone = zone,
2178                         .priority = sc->priority,
2179                 };
2180                 struct mem_cgroup *memcg;
2181
2182                 nr_reclaimed = sc->nr_reclaimed;
2183                 nr_scanned = sc->nr_scanned;
2184
2185                 memcg = mem_cgroup_iter(root, NULL, &reclaim);
2186                 do {
2187                         struct lruvec *lruvec;
2188
2189                         lruvec = mem_cgroup_zone_lruvec(zone, memcg);
2190
2191                         shrink_lruvec(lruvec, sc);
2192
2193                         /*
2194                          * Direct reclaim and kswapd have to scan all memory
2195                          * cgroups to fulfill the overall scan target for the
2196                          * zone.
2197                          *
2198                          * Limit reclaim, on the other hand, only cares about
2199                          * nr_to_reclaim pages to be reclaimed and it will
2200                          * retry with decreasing priority if one round over the
2201                          * whole hierarchy is not sufficient.
2202                          */
2203                         if (!global_reclaim(sc) &&
2204                                         sc->nr_reclaimed >= sc->nr_to_reclaim) {
2205                                 mem_cgroup_iter_break(root, memcg);
2206                                 break;
2207                         }
2208                         memcg = mem_cgroup_iter(root, memcg, &reclaim);
2209                 } while (memcg);
2210
2211                 vmpressure(sc->gfp_mask, sc->target_mem_cgroup,
2212                            sc->nr_scanned - nr_scanned,
2213                            sc->nr_reclaimed - nr_reclaimed);
2214
2215         } while (should_continue_reclaim(zone, sc->nr_reclaimed - nr_reclaimed,
2216                                          sc->nr_scanned - nr_scanned, sc));
2217 }
2218
2219 /* Returns true if compaction should go ahead for a high-order request */
2220 static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
2221 {
2222         unsigned long balance_gap, watermark;
2223         bool watermark_ok;
2224
2225         /* Do not consider compaction for orders reclaim is meant to satisfy */
2226         if (sc->order <= PAGE_ALLOC_COSTLY_ORDER)
2227                 return false;
2228
2229         /*
2230          * Compaction takes time to run and there are potentially other
2231          * callers using the pages just freed. Continue reclaiming until
2232          * there is a buffer of free pages available to give compaction
2233          * a reasonable chance of completing and allocating the page
2234          */
2235         balance_gap = min(low_wmark_pages(zone),
2236                 (zone->managed_pages + KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
2237                         KSWAPD_ZONE_BALANCE_GAP_RATIO);
2238         watermark = high_wmark_pages(zone) + balance_gap + (2UL << sc->order);
2239         watermark_ok = zone_watermark_ok_safe(zone, 0, watermark, 0, 0);
2240
2241         /*
2242          * If compaction is deferred, reclaim up to a point where
2243          * compaction will have a chance of success when re-enabled
2244          */
2245         if (compaction_deferred(zone, sc->order))
2246                 return watermark_ok;
2247
2248         /* If compaction is not ready to start, keep reclaiming */
2249         if (!compaction_suitable(zone, sc->order))
2250                 return false;
2251
2252         return watermark_ok;
2253 }
2254
2255 /*
2256  * This is the direct reclaim path, for page-allocating processes.  We only
2257  * try to reclaim pages from zones which will satisfy the caller's allocation
2258  * request.
2259  *
2260  * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
2261  * Because:
2262  * a) The caller may be trying to free *extra* pages to satisfy a higher-order
2263  *    allocation or
2264  * b) The target zone may be at high_wmark_pages(zone) but the lower zones
2265  *    must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
2266  *    zone defense algorithm.
2267  *
2268  * If a zone is deemed to be full of pinned pages then just give it a light
2269  * scan then give up on it.
2270  *
2271  * This function returns true if a zone is being reclaimed for a costly
2272  * high-order allocation and compaction is ready to begin. This indicates to
2273  * the caller that it should consider retrying the allocation instead of
2274  * further reclaim.
2275  */
2276 static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
2277 {
2278         struct zoneref *z;
2279         struct zone *zone;
2280         unsigned long nr_soft_reclaimed;
2281         unsigned long nr_soft_scanned;
2282         bool aborted_reclaim = false;
2283
2284         /*
2285          * If the number of buffer_heads in the machine exceeds the maximum
2286          * allowed level, force direct reclaim to scan the highmem zone as
2287          * highmem pages could be pinning lowmem pages storing buffer_heads
2288          */
2289         if (buffer_heads_over_limit)
2290                 sc->gfp_mask |= __GFP_HIGHMEM;
2291
2292         for_each_zone_zonelist_nodemask(zone, z, zonelist,
2293                                         gfp_zone(sc->gfp_mask), sc->nodemask) {
2294                 if (!populated_zone(zone))
2295                         continue;
2296                 /*
2297                  * Take care memory controller reclaiming has small influence
2298                  * to global LRU.
2299                  */
2300                 if (global_reclaim(sc)) {
2301                         if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2302                                 continue;
2303                         if (sc->priority != DEF_PRIORITY &&
2304                             !zone_reclaimable(zone))
2305                                 continue;       /* Let kswapd poll it */
2306                         if (IS_ENABLED(CONFIG_COMPACTION)) {
2307                                 /*
2308                                  * If we already have plenty of memory free for
2309                                  * compaction in this zone, don't free any more.
2310                                  * Even though compaction is invoked for any
2311                                  * non-zero order, only frequent costly order
2312                                  * reclamation is disruptive enough to become a
2313                                  * noticeable problem, like transparent huge
2314                                  * page allocations.
2315                                  */
2316                                 if (compaction_ready(zone, sc)) {
2317                                         aborted_reclaim = true;
2318                                         continue;
2319                                 }
2320                         }
2321                         /*
2322                          * This steals pages from memory cgroups over softlimit
2323                          * and returns the number of reclaimed pages and
2324                          * scanned pages. This works for global memory pressure
2325                          * and balancing, not for a memcg's limit.
2326                          */
2327                         nr_soft_scanned = 0;
2328                         nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
2329                                                 sc->order, sc->gfp_mask,
2330                                                 &nr_soft_scanned);
2331                         sc->nr_reclaimed += nr_soft_reclaimed;
2332                         sc->nr_scanned += nr_soft_scanned;
2333                         /* need some check for avoid more shrink_zone() */
2334                 }
2335
2336                 shrink_zone(zone, sc);
2337         }
2338
2339         return aborted_reclaim;
2340 }
2341
2342 /* All zones in zonelist are unreclaimable? */
2343 static bool all_unreclaimable(struct zonelist *zonelist,
2344                 struct scan_control *sc)
2345 {
2346         struct zoneref *z;
2347         struct zone *zone;
2348
2349         for_each_zone_zonelist_nodemask(zone, z, zonelist,
2350                         gfp_zone(sc->gfp_mask), sc->nodemask) {
2351                 if (!populated_zone(zone))
2352                         continue;
2353                 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2354                         continue;
2355                 if (zone_reclaimable(zone))
2356                         return false;
2357         }
2358
2359         return true;
2360 }
2361
2362 /*
2363  * This is the main entry point to direct page reclaim.
2364  *
2365  * If a full scan of the inactive list fails to free enough memory then we
2366  * are "out of memory" and something needs to be killed.
2367  *
2368  * If the caller is !__GFP_FS then the probability of a failure is reasonably
2369  * high - the zone may be full of dirty or under-writeback pages, which this
2370  * caller can't do much about.  We kick the writeback threads and take explicit
2371  * naps in the hope that some of these pages can be written.  But if the
2372  * allocating task holds filesystem locks which prevent writeout this might not
2373  * work, and the allocation attempt will fail.
2374  *
2375  * returns:     0, if no pages reclaimed
2376  *              else, the number of pages reclaimed
2377  */
2378 static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
2379                                         struct scan_control *sc,
2380                                         struct shrink_control *shrink)
2381 {
2382         unsigned long total_scanned = 0;
2383         struct reclaim_state *reclaim_state = current->reclaim_state;
2384         struct zoneref *z;
2385         struct zone *zone;
2386         unsigned long writeback_threshold;
2387         bool aborted_reclaim;
2388
2389         delayacct_freepages_start();
2390
2391         if (global_reclaim(sc))
2392                 count_vm_event(ALLOCSTALL);
2393
2394         do {
2395                 vmpressure_prio(sc->gfp_mask, sc->target_mem_cgroup,
2396                                 sc->priority);
2397                 sc->nr_scanned = 0;
2398                 aborted_reclaim = shrink_zones(zonelist, sc);
2399
2400                 /*
2401                  * Don't shrink slabs when reclaiming memory from over limit
2402                  * cgroups but do shrink slab at least once when aborting
2403                  * reclaim for compaction to avoid unevenly scanning file/anon
2404                  * LRU pages over slab pages.
2405                  */
2406                 if (global_reclaim(sc)) {
2407                         unsigned long lru_pages = 0;
2408
2409                         nodes_clear(shrink->nodes_to_scan);
2410                         for_each_zone_zonelist(zone, z, zonelist,
2411                                         gfp_zone(sc->gfp_mask)) {
2412                                 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2413                                         continue;
2414
2415                                 lru_pages += zone_reclaimable_pages(zone);
2416                                 node_set(zone_to_nid(zone),
2417                                          shrink->nodes_to_scan);
2418                         }
2419
2420                         shrink_slab(shrink, sc->nr_scanned, lru_pages);
2421                         if (reclaim_state) {
2422                                 sc->nr_reclaimed += reclaim_state->reclaimed_slab;
2423                                 reclaim_state->reclaimed_slab = 0;
2424                         }
2425                 }
2426                 total_scanned += sc->nr_scanned;
2427                 if (sc->nr_reclaimed >= sc->nr_to_reclaim)
2428                         goto out;
2429
2430                 /*
2431                  * If we're getting trouble reclaiming, start doing
2432                  * writepage even in laptop mode.
2433                  */
2434                 if (sc->priority < DEF_PRIORITY - 2)
2435                         sc->may_writepage = 1;
2436
2437                 /*
2438                  * Try to write back as many pages as we just scanned.  This
2439                  * tends to cause slow streaming writers to write data to the
2440                  * disk smoothly, at the dirtying rate, which is nice.   But
2441                  * that's undesirable in laptop mode, where we *want* lumpy
2442                  * writeout.  So in laptop mode, write out the whole world.
2443                  */
2444                 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
2445                 if (total_scanned > writeback_threshold) {
2446                         wakeup_flusher_threads(laptop_mode ? 0 : total_scanned,
2447                                                 WB_REASON_TRY_TO_FREE_PAGES);
2448                         sc->may_writepage = 1;
2449                 }
2450         } while (--sc->priority >= 0 && !aborted_reclaim);
2451
2452 out:
2453         delayacct_freepages_end();
2454
2455         if (sc->nr_reclaimed)
2456                 return sc->nr_reclaimed;
2457
2458         /*
2459          * As hibernation is going on, kswapd is freezed so that it can't mark
2460          * the zone into all_unreclaimable. Thus bypassing all_unreclaimable
2461          * check.
2462          */
2463         if (oom_killer_disabled)
2464                 return 0;
2465
2466         /* Aborted reclaim to try compaction? don't OOM, then */
2467         if (aborted_reclaim)
2468                 return 1;
2469
2470         /* top priority shrink_zones still had more to do? don't OOM, then */
2471         if (global_reclaim(sc) && !all_unreclaimable(zonelist, sc))
2472                 return 1;
2473
2474         return 0;
2475 }
2476
2477 static bool pfmemalloc_watermark_ok(pg_data_t *pgdat)
2478 {
2479         struct zone *zone;
2480         unsigned long pfmemalloc_reserve = 0;
2481         unsigned long free_pages = 0;
2482         int i;
2483         bool wmark_ok;
2484
2485         for (i = 0; i <= ZONE_NORMAL; i++) {
2486                 zone = &pgdat->node_zones[i];
2487                 pfmemalloc_reserve += min_wmark_pages(zone);
2488                 free_pages += zone_page_state(zone, NR_FREE_PAGES);
2489         }
2490
2491         wmark_ok = free_pages > pfmemalloc_reserve / 2;
2492
2493         /* kswapd must be awake if processes are being throttled */
2494         if (!wmark_ok && waitqueue_active(&pgdat->kswapd_wait)) {
2495                 pgdat->classzone_idx = min(pgdat->classzone_idx,
2496                                                 (enum zone_type)ZONE_NORMAL);
2497                 wake_up_interruptible(&pgdat->kswapd_wait);
2498         }
2499
2500         return wmark_ok;
2501 }
2502
2503 /*
2504  * Throttle direct reclaimers if backing storage is backed by the network
2505  * and the PFMEMALLOC reserve for the preferred node is getting dangerously
2506  * depleted. kswapd will continue to make progress and wake the processes
2507  * when the low watermark is reached.
2508  *
2509  * Returns true if a fatal signal was delivered during throttling. If this
2510  * happens, the page allocator should not consider triggering the OOM killer.
2511  */
2512 static bool throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist *zonelist,
2513                                         nodemask_t *nodemask)
2514 {
2515         struct zone *zone;
2516         int high_zoneidx = gfp_zone(gfp_mask);
2517         pg_data_t *pgdat;
2518
2519         /*
2520          * Kernel threads should not be throttled as they may be indirectly
2521          * responsible for cleaning pages necessary for reclaim to make forward
2522          * progress. kjournald for example may enter direct reclaim while
2523          * committing a transaction where throttling it could forcing other
2524          * processes to block on log_wait_commit().
2525          */
2526         if (current->flags & PF_KTHREAD)
2527                 goto out;
2528
2529         /*
2530          * If a fatal signal is pending, this process should not throttle.
2531          * It should return quickly so it can exit and free its memory
2532          */
2533         if (fatal_signal_pending(current))
2534                 goto out;
2535
2536         /* Check if the pfmemalloc reserves are ok */
2537         first_zones_zonelist(zonelist, high_zoneidx, NULL, &zone);
2538         pgdat = zone->zone_pgdat;
2539         if (pfmemalloc_watermark_ok(pgdat))
2540                 goto out;
2541
2542         /* Account for the throttling */
2543         count_vm_event(PGSCAN_DIRECT_THROTTLE);
2544
2545         /*
2546          * If the caller cannot enter the filesystem, it's possible that it
2547          * is due to the caller holding an FS lock or performing a journal
2548          * transaction in the case of a filesystem like ext[3|4]. In this case,
2549          * it is not safe to block on pfmemalloc_wait as kswapd could be
2550          * blocked waiting on the same lock. Instead, throttle for up to a
2551          * second before continuing.
2552          */
2553         if (!(gfp_mask & __GFP_FS)) {
2554                 wait_event_interruptible_timeout(pgdat->pfmemalloc_wait,
2555                         pfmemalloc_watermark_ok(pgdat), HZ);
2556
2557                 goto check_pending;
2558         }
2559
2560         /* Throttle until kswapd wakes the process */
2561         wait_event_killable(zone->zone_pgdat->pfmemalloc_wait,
2562                 pfmemalloc_watermark_ok(pgdat));
2563
2564 check_pending:
2565         if (fatal_signal_pending(current))
2566                 return true;
2567
2568 out:
2569         return false;
2570 }
2571
2572 unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
2573                                 gfp_t gfp_mask, nodemask_t *nodemask)
2574 {
2575         unsigned long nr_reclaimed;
2576         struct scan_control sc = {
2577                 .gfp_mask = (gfp_mask = memalloc_noio_flags(gfp_mask)),
2578                 .may_writepage = !laptop_mode,
2579                 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2580                 .may_unmap = 1,
2581                 .may_swap = 1,
2582                 .order = order,
2583                 .priority = DEF_PRIORITY,
2584                 .target_mem_cgroup = NULL,
2585                 .nodemask = nodemask,
2586         };
2587         struct shrink_control shrink = {
2588                 .gfp_mask = sc.gfp_mask,
2589         };
2590
2591         /*
2592          * Do not enter reclaim if fatal signal was delivered while throttled.
2593          * 1 is returned so that the page allocator does not OOM kill at this
2594          * point.
2595          */
2596         if (throttle_direct_reclaim(gfp_mask, zonelist, nodemask))
2597                 return 1;
2598
2599         trace_mm_vmscan_direct_reclaim_begin(order,
2600                                 sc.may_writepage,
2601                                 gfp_mask);
2602
2603         nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2604
2605         trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
2606
2607         return nr_reclaimed;
2608 }
2609
2610 #ifdef CONFIG_MEMCG
2611
2612 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *memcg,
2613                                                 gfp_t gfp_mask, bool noswap,
2614                                                 struct zone *zone,
2615                                                 unsigned long *nr_scanned)
2616 {
2617         struct scan_control sc = {
2618                 .nr_scanned = 0,
2619                 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2620                 .may_writepage = !laptop_mode,
2621                 .may_unmap = 1,
2622                 .may_swap = !noswap,
2623                 .order = 0,
2624                 .priority = 0,
2625                 .target_mem_cgroup = memcg,
2626         };
2627         struct lruvec *lruvec = mem_cgroup_zone_lruvec(zone, memcg);
2628
2629         sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2630                         (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
2631
2632         trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc.order,
2633                                                       sc.may_writepage,
2634                                                       sc.gfp_mask);
2635
2636         /*
2637          * NOTE: Although we can get the priority field, using it
2638          * here is not a good idea, since it limits the pages we can scan.
2639          * if we don't reclaim here, the shrink_zone from balance_pgdat
2640          * will pick up pages from other mem cgroup's as well. We hack
2641          * the priority and make it zero.
2642          */
2643         shrink_lruvec(lruvec, &sc);
2644
2645         trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
2646
2647         *nr_scanned = sc.nr_scanned;
2648         return sc.nr_reclaimed;
2649 }
2650
2651 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
2652                                            gfp_t gfp_mask,
2653                                            bool noswap)
2654 {
2655         struct zonelist *zonelist;
2656         unsigned long nr_reclaimed;
2657         int nid;
2658         struct scan_control sc = {
2659                 .may_writepage = !laptop_mode,
2660                 .may_unmap = 1,
2661                 .may_swap = !noswap,
2662                 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2663                 .order = 0,
2664                 .priority = DEF_PRIORITY,
2665                 .target_mem_cgroup = memcg,
2666                 .nodemask = NULL, /* we don't care the placement */
2667                 .gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2668                                 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
2669         };
2670         struct shrink_control shrink = {
2671                 .gfp_mask = sc.gfp_mask,
2672         };
2673
2674         /*
2675          * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
2676          * take care of from where we get pages. So the node where we start the
2677          * scan does not need to be the current node.
2678          */
2679         nid = mem_cgroup_select_victim_node(memcg);
2680
2681         zonelist = NODE_DATA(nid)->node_zonelists;
2682
2683         trace_mm_vmscan_memcg_reclaim_begin(0,
2684                                             sc.may_writepage,
2685                                             sc.gfp_mask);
2686
2687         nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2688
2689         trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
2690
2691         return nr_reclaimed;
2692 }
2693 #endif
2694
2695 static void age_active_anon(struct zone *zone, struct scan_control *sc)
2696 {
2697         struct mem_cgroup *memcg;
2698
2699         if (!total_swap_pages)
2700                 return;
2701
2702         memcg = mem_cgroup_iter(NULL, NULL, NULL);
2703         do {
2704                 struct lruvec *lruvec = mem_cgroup_zone_lruvec(zone, memcg);
2705
2706                 if (inactive_anon_is_low(lruvec))
2707                         shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
2708                                            sc, LRU_ACTIVE_ANON);
2709
2710                 memcg = mem_cgroup_iter(NULL, memcg, NULL);
2711         } while (memcg);
2712 }
2713
2714 static bool zone_balanced(struct zone *zone, int order,
2715                           unsigned long balance_gap, int classzone_idx)
2716 {
2717         if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone) +
2718                                     balance_gap, classzone_idx, 0))
2719                 return false;
2720
2721         if (IS_ENABLED(CONFIG_COMPACTION) && order &&
2722             !compaction_suitable(zone, order))
2723                 return false;
2724
2725         return true;
2726 }
2727
2728 /*
2729  * pgdat_balanced() is used when checking if a node is balanced.
2730  *
2731  * For order-0, all zones must be balanced!
2732  *
2733  * For high-order allocations only zones that meet watermarks and are in a
2734  * zone allowed by the callers classzone_idx are added to balanced_pages. The
2735  * total of balanced pages must be at least 25% of the zones allowed by
2736  * classzone_idx for the node to be considered balanced. Forcing all zones to
2737  * be balanced for high orders can cause excessive reclaim when there are
2738  * imbalanced zones.
2739  * The choice of 25% is due to
2740  *   o a 16M DMA zone that is balanced will not balance a zone on any
2741  *     reasonable sized machine
2742  *   o On all other machines, the top zone must be at least a reasonable
2743  *     percentage of the middle zones. For example, on 32-bit x86, highmem
2744  *     would need to be at least 256M for it to be balance a whole node.
2745  *     Similarly, on x86-64 the Normal zone would need to be at least 1G
2746  *     to balance a node on its own. These seemed like reasonable ratios.
2747  */
2748 static bool pgdat_balanced(pg_data_t *pgdat, int order, int classzone_idx)
2749 {
2750         unsigned long managed_pages = 0;
2751         unsigned long balanced_pages = 0;
2752         int i;
2753
2754         /* Check the watermark levels */
2755         for (i = 0; i <= classzone_idx; i++) {
2756                 struct zone *zone = pgdat->node_zones + i;
2757
2758                 if (!populated_zone(zone))
2759                         continue;
2760
2761                 managed_pages += zone->managed_pages;
2762
2763                 /*
2764                  * A special case here:
2765                  *
2766                  * balance_pgdat() skips over all_unreclaimable after
2767                  * DEF_PRIORITY. Effectively, it considers them balanced so
2768                  * they must be considered balanced here as well!
2769                  */
2770                 if (!zone_reclaimable(zone)) {
2771                         balanced_pages += zone->managed_pages;
2772                         continue;
2773                 }
2774
2775                 if (zone_balanced(zone, order, 0, i))
2776                         balanced_pages += zone->managed_pages;
2777                 else if (!order)
2778                         return false;
2779         }
2780
2781         if (order)
2782                 return balanced_pages >= (managed_pages >> 2);
2783         else
2784                 return true;
2785 }
2786
2787 /*
2788  * Prepare kswapd for sleeping. This verifies that there are no processes
2789  * waiting in throttle_direct_reclaim() and that watermarks have been met.
2790  *
2791  * Returns true if kswapd is ready to sleep
2792  */
2793 static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, long remaining,
2794                                         int classzone_idx)
2795 {
2796         /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
2797         if (remaining)
2798                 return false;
2799
2800         /*
2801          * There is a potential race between when kswapd checks its watermarks
2802          * and a process gets throttled. There is also a potential race if
2803          * processes get throttled, kswapd wakes, a large process exits therby
2804          * balancing the zones that causes kswapd to miss a wakeup. If kswapd
2805          * is going to sleep, no process should be sleeping on pfmemalloc_wait
2806          * so wake them now if necessary. If necessary, processes will wake
2807          * kswapd and get throttled again
2808          */
2809         if (waitqueue_active(&pgdat->pfmemalloc_wait)) {
2810                 wake_up(&pgdat->pfmemalloc_wait);
2811                 return false;
2812         }
2813
2814         return pgdat_balanced(pgdat, order, classzone_idx);
2815 }
2816
2817 /*
2818  * kswapd shrinks the zone by the number of pages required to reach
2819  * the high watermark.
2820  *
2821  * Returns true if kswapd scanned at least the requested number of pages to
2822  * reclaim or if the lack of progress was due to pages under writeback.
2823  * This is used to determine if the scanning priority needs to be raised.
2824  */
2825 static bool kswapd_shrink_zone(struct zone *zone,
2826                                int classzone_idx,
2827                                struct scan_control *sc,
2828                                unsigned long lru_pages,
2829                                unsigned long *nr_attempted)
2830 {
2831         int testorder = sc->order;
2832         unsigned long balance_gap;
2833         struct reclaim_state *reclaim_state = current->reclaim_state;
2834         struct shrink_control shrink = {
2835                 .gfp_mask = sc->gfp_mask,
2836         };
2837         bool lowmem_pressure;
2838
2839         /* Reclaim above the high watermark. */
2840         sc->nr_to_reclaim = max(SWAP_CLUSTER_MAX, high_wmark_pages(zone));
2841
2842         /*
2843          * Kswapd reclaims only single pages with compaction enabled. Trying
2844          * too hard to reclaim until contiguous free pages have become
2845          * available can hurt performance by evicting too much useful data
2846          * from memory. Do not reclaim more than needed for compaction.
2847          */
2848         if (IS_ENABLED(CONFIG_COMPACTION) && sc->order &&
2849                         compaction_suitable(zone, sc->order) !=
2850                                 COMPACT_SKIPPED)
2851                 testorder = 0;
2852
2853         /*
2854          * We put equal pressure on every zone, unless one zone has way too
2855          * many pages free already. The "too many pages" is defined as the
2856          * high wmark plus a "gap" where the gap is either the low
2857          * watermark or 1% of the zone, whichever is smaller.
2858          */
2859         balance_gap = min(low_wmark_pages(zone),
2860                 (zone->managed_pages + KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
2861                 KSWAPD_ZONE_BALANCE_GAP_RATIO);
2862
2863         /*
2864          * If there is no low memory pressure or the zone is balanced then no
2865          * reclaim is necessary
2866          */
2867         lowmem_pressure = (buffer_heads_over_limit && is_highmem(zone));
2868         if (!lowmem_pressure && zone_balanced(zone, testorder,
2869                                                 balance_gap, classzone_idx))
2870                 return true;
2871
2872         shrink_zone(zone, sc);
2873         nodes_clear(shrink.nodes_to_scan);
2874         node_set(zone_to_nid(zone), shrink.nodes_to_scan);
2875
2876         reclaim_state->reclaimed_slab = 0;
2877         shrink_slab(&shrink, sc->nr_scanned, lru_pages);
2878         sc->nr_reclaimed += reclaim_state->reclaimed_slab;
2879
2880         /* Account for the number of pages attempted to reclaim */
2881         *nr_attempted += sc->nr_to_reclaim;
2882
2883         zone_clear_flag(zone, ZONE_WRITEBACK);
2884
2885         /*
2886          * If a zone reaches its high watermark, consider it to be no longer
2887          * congested. It's possible there are dirty pages backed by congested
2888          * BDIs but as pressure is relieved, speculatively avoid congestion
2889          * waits.
2890          */
2891         if (zone_reclaimable(zone) &&
2892             zone_balanced(zone, testorder, 0, classzone_idx)) {
2893                 zone_clear_flag(zone, ZONE_CONGESTED);
2894                 zone_clear_flag(zone, ZONE_TAIL_LRU_DIRTY);
2895         }
2896
2897         return sc->nr_scanned >= sc->nr_to_reclaim;
2898 }
2899
2900 /*
2901  * For kswapd, balance_pgdat() will work across all this node's zones until
2902  * they are all at high_wmark_pages(zone).
2903  *
2904  * Returns the final order kswapd was reclaiming at
2905  *
2906  * There is special handling here for zones which are full of pinned pages.
2907  * This can happen if the pages are all mlocked, or if they are all used by
2908  * device drivers (say, ZONE_DMA).  Or if they are all in use by hugetlb.
2909  * What we do is to detect the case where all pages in the zone have been
2910  * scanned twice and there has been zero successful reclaim.  Mark the zone as
2911  * dead and from now on, only perform a short scan.  Basically we're polling
2912  * the zone for when the problem goes away.
2913  *
2914  * kswapd scans the zones in the highmem->normal->dma direction.  It skips
2915  * zones which have free_pages > high_wmark_pages(zone), but once a zone is
2916  * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
2917  * lower zones regardless of the number of free pages in the lower zones. This
2918  * interoperates with the page allocator fallback scheme to ensure that aging
2919  * of pages is balanced across the zones.
2920  */
2921 static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
2922                                                         int *classzone_idx)
2923 {
2924         int i;
2925         int end_zone = 0;       /* Inclusive.  0 = ZONE_DMA */
2926         unsigned long nr_soft_reclaimed;
2927         unsigned long nr_soft_scanned;
2928         struct scan_control sc = {
2929                 .gfp_mask = GFP_KERNEL,
2930                 .priority = DEF_PRIORITY,
2931                 .may_unmap = 1,
2932                 .may_swap = 1,
2933                 .may_writepage = !laptop_mode,
2934                 .order = order,
2935                 .target_mem_cgroup = NULL,
2936         };
2937         count_vm_event(PAGEOUTRUN);
2938
2939         do {
2940                 unsigned long lru_pages = 0;
2941                 unsigned long nr_attempted = 0;
2942                 bool raise_priority = true;
2943                 bool pgdat_needs_compaction = (order > 0);
2944
2945                 sc.nr_reclaimed = 0;
2946
2947                 /*
2948                  * Scan in the highmem->dma direction for the highest
2949                  * zone which needs scanning
2950                  */
2951                 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
2952                         struct zone *zone = pgdat->node_zones + i;
2953
2954                         if (!populated_zone(zone))
2955                                 continue;
2956
2957                         if (sc.priority != DEF_PRIORITY &&
2958                             !zone_reclaimable(zone))
2959                                 continue;
2960
2961                         /*
2962                          * Do some background aging of the anon list, to give
2963                          * pages a chance to be referenced before reclaiming.
2964                          */
2965                         age_active_anon(zone, &sc);
2966
2967                         /*
2968                          * If the number of buffer_heads in the machine
2969                          * exceeds the maximum allowed level and this node
2970                          * has a highmem zone, force kswapd to reclaim from
2971                          * it to relieve lowmem pressure.
2972                          */
2973                         if (buffer_heads_over_limit && is_highmem_idx(i)) {
2974                                 end_zone = i;
2975                                 break;
2976                         }
2977
2978                         if (!zone_balanced(zone, order, 0, 0)) {
2979                                 end_zone = i;
2980                                 break;
2981                         } else {
2982                                 /*
2983                                  * If balanced, clear the dirty and congested
2984                                  * flags
2985                                  */
2986                                 zone_clear_flag(zone, ZONE_CONGESTED);
2987                                 zone_clear_flag(zone, ZONE_TAIL_LRU_DIRTY);
2988                         }
2989                 }
2990
2991                 if (i < 0)
2992                         goto out;
2993
2994                 for (i = 0; i <= end_zone; i++) {
2995                         struct zone *zone = pgdat->node_zones + i;
2996
2997                         if (!populated_zone(zone))
2998                                 continue;
2999
3000                         lru_pages += zone_reclaimable_pages(zone);
3001
3002                         /*
3003                          * If any zone is currently balanced then kswapd will
3004                          * not call compaction as it is expected that the
3005                          * necessary pages are already available.
3006                          */
3007                         if (pgdat_needs_compaction &&
3008                                         zone_watermark_ok(zone, order,
3009                                                 low_wmark_pages(zone),
3010                                                 *classzone_idx, 0))
3011                                 pgdat_needs_compaction = false;
3012                 }
3013
3014                 /*
3015                  * If we're getting trouble reclaiming, start doing writepage
3016                  * even in laptop mode.
3017                  */
3018                 if (sc.priority < DEF_PRIORITY - 2)
3019                         sc.may_writepage = 1;
3020
3021                 /*
3022                  * Now scan the zone in the dma->highmem direction, stopping
3023                  * at the last zone which needs scanning.
3024                  *
3025                  * We do this because the page allocator works in the opposite
3026                  * direction.  This prevents the page allocator from allocating
3027                  * pages behind kswapd's direction of progress, which would
3028                  * cause too much scanning of the lower zones.
3029                  */
3030                 for (i = 0; i <= end_zone; i++) {
3031                         struct zone *zone = pgdat->node_zones + i;
3032
3033                         if (!populated_zone(zone))
3034                                 continue;
3035
3036                         if (sc.priority != DEF_PRIORITY &&
3037                             !zone_reclaimable(zone))
3038                                 continue;
3039
3040                         sc.nr_scanned = 0;
3041
3042                         nr_soft_scanned = 0;
3043                         /*
3044                          * Call soft limit reclaim before calling shrink_zone.
3045                          */
3046                         nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
3047                                                         order, sc.gfp_mask,
3048                                                         &nr_soft_scanned);
3049                         sc.nr_reclaimed += nr_soft_reclaimed;
3050
3051                         /*
3052                          * There should be no need to raise the scanning
3053                          * priority if enough pages are already being scanned
3054                          * that that high watermark would be met at 100%
3055                          * efficiency.
3056                          */
3057                         if (kswapd_shrink_zone(zone, end_zone, &sc,
3058                                         lru_pages, &nr_attempted))
3059                                 raise_priority = false;
3060                 }
3061
3062                 /*
3063                  * If the low watermark is met there is no need for processes
3064                  * to be throttled on pfmemalloc_wait as they should not be
3065                  * able to safely make forward progress. Wake them
3066                  */
3067                 if (waitqueue_active(&pgdat->pfmemalloc_wait) &&
3068                                 pfmemalloc_watermark_ok(pgdat))
3069                         wake_up(&pgdat->pfmemalloc_wait);
3070
3071                 /*
3072                  * Fragmentation may mean that the system cannot be rebalanced
3073                  * for high-order allocations in all zones. If twice the
3074                  * allocation size has been reclaimed and the zones are still
3075                  * not balanced then recheck the watermarks at order-0 to
3076                  * prevent kswapd reclaiming excessively. Assume that a
3077                  * process requested a high-order can direct reclaim/compact.
3078                  */
3079                 if (order && sc.nr_reclaimed >= 2UL << order)
3080                         order = sc.order = 0;
3081
3082                 /* Check if kswapd should be suspending */
3083                 if (try_to_freeze() || kthread_should_stop())
3084                         break;
3085
3086                 /*
3087                  * Compact if necessary and kswapd is reclaiming at least the
3088                  * high watermark number of pages as requsted
3089                  */
3090                 if (pgdat_needs_compaction && sc.nr_reclaimed > nr_attempted)
3091                         compact_pgdat(pgdat, order);
3092
3093                 /*
3094                  * Raise priority if scanning rate is too low or there was no
3095                  * progress in reclaiming pages
3096                  */
3097                 if (raise_priority || !sc.nr_reclaimed)
3098                         sc.priority--;
3099         } while (sc.priority >= 1 &&
3100                  !pgdat_balanced(pgdat, order, *classzone_idx));
3101
3102 out:
3103         /*
3104          * Return the order we were reclaiming at so prepare_kswapd_sleep()
3105          * makes a decision on the order we were last reclaiming at. However,
3106          * if another caller entered the allocator slow path while kswapd
3107          * was awake, order will remain at the higher level
3108          */
3109         *classzone_idx = end_zone;
3110         return order;
3111 }
3112
3113 static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx)
3114 {
3115         long remaining = 0;
3116         DEFINE_WAIT(wait);
3117
3118         if (freezing(current) || kthread_should_stop())
3119                 return;
3120
3121         prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
3122
3123         /* Try to sleep for a short interval */
3124         if (prepare_kswapd_sleep(pgdat, order, remaining, classzone_idx)) {
3125                 remaining = schedule_timeout(HZ/10);
3126                 finish_wait(&pgdat->kswapd_wait, &wait);
3127                 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
3128         }
3129
3130         /*
3131          * After a short sleep, check if it was a premature sleep. If not, then
3132          * go fully to sleep until explicitly woken up.
3133          */
3134         if (prepare_kswapd_sleep(pgdat, order, remaining, classzone_idx)) {
3135                 trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
3136
3137                 /*
3138                  * vmstat counters are not perfectly accurate and the estimated
3139                  * value for counters such as NR_FREE_PAGES can deviate from the
3140                  * true value by nr_online_cpus * threshold. To avoid the zone
3141                  * watermarks being breached while under pressure, we reduce the
3142                  * per-cpu vmstat threshold while kswapd is awake and restore
3143                  * them before going back to sleep.
3144                  */
3145                 set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold);
3146
3147                 /*
3148                  * Compaction records what page blocks it recently failed to
3149                  * isolate pages from and skips them in the future scanning.
3150                  * When kswapd is going to sleep, it is reasonable to assume
3151                  * that pages and compaction may succeed so reset the cache.
3152                  */
3153                 reset_isolation_suitable(pgdat);
3154
3155                 if (!kthread_should_stop())
3156                         schedule();
3157
3158                 set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold);
3159         } else {
3160                 if (remaining)
3161                         count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
3162                 else
3163                         count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
3164         }
3165         finish_wait(&pgdat->kswapd_wait, &wait);
3166 }
3167
3168 /*
3169  * The background pageout daemon, started as a kernel thread
3170  * from the init process.
3171  *
3172  * This basically trickles out pages so that we have _some_
3173  * free memory available even if there is no other activity
3174  * that frees anything up. This is needed for things like routing
3175  * etc, where we otherwise might have all activity going on in
3176  * asynchronous contexts that cannot page things out.
3177  *
3178  * If there are applications that are active memory-allocators
3179  * (most normal use), this basically shouldn't matter.
3180  */
3181 static int kswapd(void *p)
3182 {
3183         unsigned long order, new_order;
3184         unsigned balanced_order;
3185         int classzone_idx, new_classzone_idx;
3186         int balanced_classzone_idx;
3187         pg_data_t *pgdat = (pg_data_t*)p;
3188         struct task_struct *tsk = current;
3189
3190         struct reclaim_state reclaim_state = {
3191                 .reclaimed_slab = 0,
3192         };
3193         const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
3194
3195         lockdep_set_current_reclaim_state(GFP_KERNEL);
3196
3197         if (!cpumask_empty(cpumask))
3198                 set_cpus_allowed_ptr(tsk, cpumask);
3199         current->reclaim_state = &reclaim_state;
3200
3201         /*
3202          * Tell the memory management that we're a "memory allocator",
3203          * and that if we need more memory we should get access to it
3204          * regardless (see "__alloc_pages()"). "kswapd" should
3205          * never get caught in the normal page freeing logic.
3206          *
3207          * (Kswapd normally doesn't need memory anyway, but sometimes
3208          * you need a small amount of memory in order to be able to
3209          * page out something else, and this flag essentially protects
3210          * us from recursively trying to free more memory as we're
3211          * trying to free the first piece of memory in the first place).
3212          */
3213         tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
3214         set_freezable();
3215
3216         order = new_order = 0;
3217         balanced_order = 0;
3218         classzone_idx = new_classzone_idx = pgdat->nr_zones - 1;
3219         balanced_classzone_idx = classzone_idx;
3220         for ( ; ; ) {
3221                 bool ret;
3222
3223                 /*
3224                  * If the last balance_pgdat was unsuccessful it's unlikely a
3225                  * new request of a similar or harder type will succeed soon
3226                  * so consider going to sleep on the basis we reclaimed at
3227                  */
3228                 if (balanced_classzone_idx >= new_classzone_idx &&
3229                                         balanced_order == new_order) {
3230                         new_order = pgdat->kswapd_max_order;
3231                         new_classzone_idx = pgdat->classzone_idx;
3232                         pgdat->kswapd_max_order =  0;
3233                         pgdat->classzone_idx = pgdat->nr_zones - 1;
3234                 }
3235
3236                 if (order < new_order || classzone_idx > new_classzone_idx) {
3237                         /*
3238                          * Don't sleep if someone wants a larger 'order'
3239                          * allocation or has tigher zone constraints
3240                          */
3241                         order = new_order;
3242                         classzone_idx = new_classzone_idx;
3243                 } else {
3244                         kswapd_try_to_sleep(pgdat, balanced_order,
3245                                                 balanced_classzone_idx);
3246                         order = pgdat->kswapd_max_order;
3247                         classzone_idx = pgdat->classzone_idx;
3248                         new_order = order;
3249                         new_classzone_idx = classzone_idx;
3250                         pgdat->kswapd_max_order = 0;
3251                         pgdat->classzone_idx = pgdat->nr_zones - 1;
3252                 }
3253
3254                 ret = try_to_freeze();
3255                 if (kthread_should_stop())
3256                         break;
3257
3258                 /*
3259                  * We can speed up thawing tasks if we don't call balance_pgdat
3260                  * after returning from the refrigerator
3261                  */
3262                 if (!ret) {
3263                         trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
3264                         balanced_classzone_idx = classzone_idx;
3265                         balanced_order = balance_pgdat(pgdat, order,
3266                                                 &balanced_classzone_idx);
3267                 }
3268         }
3269
3270         current->reclaim_state = NULL;
3271         return 0;
3272 }
3273
3274 /*
3275  * A zone is low on free memory, so wake its kswapd task to service it.
3276  */
3277 void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
3278 {
3279         pg_data_t *pgdat;
3280
3281         if (!populated_zone(zone))
3282                 return;
3283
3284         if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
3285                 return;
3286         pgdat = zone->zone_pgdat;
3287         if (pgdat->kswapd_max_order < order) {
3288                 pgdat->kswapd_max_order = order;
3289                 pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx);
3290         }
3291         if (!waitqueue_active(&pgdat->kswapd_wait))
3292                 return;
3293         if (zone_balanced(zone, order, 0, 0))
3294                 return;
3295
3296         trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);
3297         wake_up_interruptible(&pgdat->kswapd_wait);
3298 }
3299
3300 /*
3301  * The reclaimable count would be mostly accurate.
3302  * The less reclaimable pages may be
3303  * - mlocked pages, which will be moved to unevictable list when encountered
3304  * - mapped pages, which may require several travels to be reclaimed
3305  * - dirty pages, which is not "instantly" reclaimable
3306  */
3307 unsigned long global_reclaimable_pages(void)
3308 {
3309         int nr;
3310
3311         nr = global_page_state(NR_ACTIVE_FILE) +
3312              global_page_state(NR_INACTIVE_FILE);
3313
3314         if (get_nr_swap_pages() > 0)
3315                 nr += global_page_state(NR_ACTIVE_ANON) +
3316                       global_page_state(NR_INACTIVE_ANON);
3317
3318         return nr;
3319 }
3320
3321 #ifdef CONFIG_HIBERNATION
3322 /*
3323  * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
3324  * freed pages.
3325  *
3326  * Rather than trying to age LRUs the aim is to preserve the overall
3327  * LRU order by reclaiming preferentially
3328  * inactive > active > active referenced > active mapped
3329  */
3330 unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
3331 {
3332         struct reclaim_state reclaim_state;
3333         struct scan_control sc = {
3334                 .gfp_mask = GFP_HIGHUSER_MOVABLE,
3335                 .may_swap = 1,
3336                 .may_unmap = 1,
3337                 .may_writepage = 1,
3338                 .nr_to_reclaim = nr_to_reclaim,
3339                 .hibernation_mode = 1,
3340                 .order = 0,
3341                 .priority = DEF_PRIORITY,
3342         };
3343         struct shrink_control shrink = {
3344                 .gfp_mask = sc.gfp_mask,
3345         };
3346         struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
3347         struct task_struct *p = current;
3348         unsigned long nr_reclaimed;
3349
3350         p->flags |= PF_MEMALLOC;
3351         lockdep_set_current_reclaim_state(sc.gfp_mask);
3352         reclaim_state.reclaimed_slab = 0;
3353         p->reclaim_state = &reclaim_state;
3354
3355         nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
3356
3357         p->reclaim_state = NULL;
3358         lockdep_clear_current_reclaim_state();
3359         p->flags &= ~PF_MEMALLOC;
3360
3361         return nr_reclaimed;
3362 }
3363 #endif /* CONFIG_HIBERNATION */
3364
3365 /* It's optimal to keep kswapds on the same CPUs as their memory, but
3366    not required for correctness.  So if the last cpu in a node goes
3367    away, we get changed to run anywhere: as the first one comes back,
3368    restore their cpu bindings. */
3369 static int cpu_callback(struct notifier_block *nfb, unsigned long action,
3370                         void *hcpu)
3371 {
3372         int nid;
3373
3374         if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
3375                 for_each_node_state(nid, N_MEMORY) {
3376                         pg_data_t *pgdat = NODE_DATA(nid);
3377                         const struct cpumask *mask;
3378
3379                         mask = cpumask_of_node(pgdat->node_id);
3380
3381                         if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
3382                                 /* One of our CPUs online: restore mask */
3383                                 set_cpus_allowed_ptr(pgdat->kswapd, mask);
3384                 }
3385         }
3386         return NOTIFY_OK;
3387 }
3388
3389 /*
3390  * This kswapd start function will be called by init and node-hot-add.
3391  * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
3392  */
3393 int kswapd_run(int nid)
3394 {
3395         pg_data_t *pgdat = NODE_DATA(nid);
3396         int ret = 0;
3397
3398         if (pgdat->kswapd)
3399                 return 0;
3400
3401         pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
3402         if (IS_ERR(pgdat->kswapd)) {
3403                 /* failure at boot is fatal */
3404                 BUG_ON(system_state == SYSTEM_BOOTING);
3405                 pr_err("Failed to start kswapd on node %d\n", nid);
3406                 ret = PTR_ERR(pgdat->kswapd);
3407                 pgdat->kswapd = NULL;
3408         }
3409         return ret;
3410 }
3411
3412 /*
3413  * Called by memory hotplug when all memory in a node is offlined.  Caller must
3414  * hold lock_memory_hotplug().
3415  */
3416 void kswapd_stop(int nid)
3417 {
3418         struct task_struct *kswapd = NODE_DATA(nid)->kswapd;
3419
3420         if (kswapd) {
3421                 kthread_stop(kswapd);
3422                 NODE_DATA(nid)->kswapd = NULL;
3423         }
3424 }
3425
3426 static int __init kswapd_init(void)
3427 {
3428         int nid;
3429
3430         swap_setup();
3431         for_each_node_state(nid, N_MEMORY)
3432                 kswapd_run(nid);
3433         hotcpu_notifier(cpu_callback, 0);
3434         return 0;
3435 }
3436
3437 module_init(kswapd_init)
3438
3439 #ifdef CONFIG_NUMA
3440 /*
3441  * Zone reclaim mode
3442  *
3443  * If non-zero call zone_reclaim when the number of free pages falls below
3444  * the watermarks.
3445  */
3446 int zone_reclaim_mode __read_mostly;
3447
3448 #define RECLAIM_OFF 0
3449 #define RECLAIM_ZONE (1<<0)     /* Run shrink_inactive_list on the zone */
3450 #define RECLAIM_WRITE (1<<1)    /* Writeout pages during reclaim */
3451 #define RECLAIM_SWAP (1<<2)     /* Swap pages out during reclaim */
3452
3453 /*
3454  * Priority for ZONE_RECLAIM. This determines the fraction of pages
3455  * of a node considered for each zone_reclaim. 4 scans 1/16th of
3456  * a zone.
3457  */
3458 #define ZONE_RECLAIM_PRIORITY 4
3459
3460 /*
3461  * Percentage of pages in a zone that must be unmapped for zone_reclaim to
3462  * occur.
3463  */
3464 int sysctl_min_unmapped_ratio = 1;
3465
3466 /*
3467  * If the number of slab pages in a zone grows beyond this percentage then
3468  * slab reclaim needs to occur.
3469  */
3470 int sysctl_min_slab_ratio = 5;
3471
3472 static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
3473 {
3474         unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
3475         unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
3476                 zone_page_state(zone, NR_ACTIVE_FILE);
3477
3478         /*
3479          * It's possible for there to be more file mapped pages than
3480          * accounted for by the pages on the file LRU lists because
3481          * tmpfs pages accounted for as ANON can also be FILE_MAPPED
3482          */
3483         return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
3484 }
3485
3486 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
3487 static long zone_pagecache_reclaimable(struct zone *zone)
3488 {
3489         long nr_pagecache_reclaimable;
3490         long delta = 0;
3491
3492         /*
3493          * If RECLAIM_SWAP is set, then all file pages are considered
3494          * potentially reclaimable. Otherwise, we have to worry about
3495          * pages like swapcache and zone_unmapped_file_pages() provides
3496          * a better estimate
3497          */
3498         if (zone_reclaim_mode & RECLAIM_SWAP)
3499                 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
3500         else
3501                 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
3502
3503         /* If we can't clean pages, remove dirty pages from consideration */
3504         if (!(zone_reclaim_mode & RECLAIM_WRITE))
3505                 delta += zone_page_state(zone, NR_FILE_DIRTY);
3506
3507         /* Watch for any possible underflows due to delta */
3508         if (unlikely(delta > nr_pagecache_reclaimable))
3509                 delta = nr_pagecache_reclaimable;
3510
3511         return nr_pagecache_reclaimable - delta;
3512 }
3513
3514 /*
3515  * Try to free up some pages from this zone through reclaim.
3516  */
3517 static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
3518 {
3519         /* Minimum pages needed in order to stay on node */
3520         const unsigned long nr_pages = 1 << order;
3521         struct task_struct *p = current;
3522         struct reclaim_state reclaim_state;
3523         struct scan_control sc = {
3524                 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
3525                 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
3526                 .may_swap = 1,
3527                 .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
3528                 .gfp_mask = (gfp_mask = memalloc_noio_flags(gfp_mask)),
3529                 .order = order,
3530                 .priority = ZONE_RECLAIM_PRIORITY,
3531         };
3532         struct shrink_control shrink = {
3533                 .gfp_mask = sc.gfp_mask,
3534         };
3535         unsigned long nr_slab_pages0, nr_slab_pages1;
3536
3537         cond_resched();
3538         /*
3539          * We need to be able to allocate from the reserves for RECLAIM_SWAP
3540          * and we also need to be able to write out pages for RECLAIM_WRITE
3541          * and RECLAIM_SWAP.
3542          */
3543         p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
3544         lockdep_set_current_reclaim_state(gfp_mask);
3545         reclaim_state.reclaimed_slab = 0;
3546         p->reclaim_state = &reclaim_state;
3547
3548         if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
3549                 /*
3550                  * Free memory by calling shrink zone with increasing
3551                  * priorities until we have enough memory freed.
3552                  */
3553                 do {
3554                         shrink_zone(zone, &sc);
3555                 } while (sc.nr_reclaimed < nr_pages && --sc.priority >= 0);
3556         }
3557
3558         nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
3559         if (nr_slab_pages0 > zone->min_slab_pages) {
3560                 /*
3561                  * shrink_slab() does not currently allow us to determine how
3562                  * many pages were freed in this zone. So we take the current
3563                  * number of slab pages and shake the slab until it is reduced
3564                  * by the same nr_pages that we used for reclaiming unmapped
3565                  * pages.
3566                  */
3567                 nodes_clear(shrink.nodes_to_scan);
3568                 node_set(zone_to_nid(zone), shrink.nodes_to_scan);
3569                 for (;;) {
3570                         unsigned long lru_pages = zone_reclaimable_pages(zone);
3571
3572                         /* No reclaimable slab or very low memory pressure */
3573                         if (!shrink_slab(&shrink, sc.nr_scanned, lru_pages))
3574                                 break;
3575
3576                         /* Freed enough memory */
3577                         nr_slab_pages1 = zone_page_state(zone,
3578                                                         NR_SLAB_RECLAIMABLE);
3579                         if (nr_slab_pages1 + nr_pages <= nr_slab_pages0)
3580                                 break;
3581                 }
3582
3583                 /*
3584                  * Update nr_reclaimed by the number of slab pages we
3585                  * reclaimed from this zone.
3586                  */
3587                 nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
3588                 if (nr_slab_pages1 < nr_slab_pages0)
3589                         sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1;
3590         }
3591
3592         p->reclaim_state = NULL;
3593         current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
3594         lockdep_clear_current_reclaim_state();
3595         return sc.nr_reclaimed >= nr_pages;
3596 }
3597
3598 int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
3599 {
3600         int node_id;
3601         int ret;
3602
3603         /*
3604          * Zone reclaim reclaims unmapped file backed pages and
3605          * slab pages if we are over the defined limits.
3606          *
3607          * A small portion of unmapped file backed pages is needed for
3608          * file I/O otherwise pages read by file I/O will be immediately
3609          * thrown out if the zone is overallocated. So we do not reclaim
3610          * if less than a specified percentage of the zone is used by
3611          * unmapped file backed pages.
3612          */
3613         if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
3614             zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
3615                 return ZONE_RECLAIM_FULL;
3616
3617         if (!zone_reclaimable(zone))
3618                 return ZONE_RECLAIM_FULL;
3619
3620         /*
3621          * Do not scan if the allocation should not be delayed.
3622          */
3623         if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
3624                 return ZONE_RECLAIM_NOSCAN;
3625
3626         /*
3627          * Only run zone reclaim on the local zone or on zones that do not
3628          * have associated processors. This will favor the local processor
3629          * over remote processors and spread off node memory allocations
3630          * as wide as possible.
3631          */
3632         node_id = zone_to_nid(zone);
3633         if (node_state(node_id, N_CPU) && node_id != numa_node_id())
3634                 return ZONE_RECLAIM_NOSCAN;
3635
3636         if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
3637                 return ZONE_RECLAIM_NOSCAN;
3638
3639         ret = __zone_reclaim(zone, gfp_mask, order);
3640         zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
3641
3642         if (!ret)
3643                 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
3644
3645         return ret;
3646 }
3647 #endif
3648
3649 /*
3650  * page_evictable - test whether a page is evictable
3651  * @page: the page to test
3652  *
3653  * Test whether page is evictable--i.e., should be placed on active/inactive
3654  * lists vs unevictable list.
3655  *
3656  * Reasons page might not be evictable:
3657  * (1) page's mapping marked unevictable
3658  * (2) page is part of an mlocked VMA
3659  *
3660  */
3661 int page_evictable(struct page *page)
3662 {
3663         return !mapping_unevictable(page_mapping(page)) && !PageMlocked(page);
3664 }
3665
3666 #ifdef CONFIG_SHMEM
3667 /**
3668  * check_move_unevictable_pages - check pages for evictability and move to appropriate zone lru list
3669  * @pages:      array of pages to check
3670  * @nr_pages:   number of pages to check
3671  *
3672  * Checks pages for evictability and moves them to the appropriate lru list.
3673  *
3674  * This function is only used for SysV IPC SHM_UNLOCK.
3675  */
3676 void check_move_unevictable_pages(struct page **pages, int nr_pages)
3677 {
3678         struct lruvec *lruvec;
3679         struct zone *zone = NULL;
3680         int pgscanned = 0;
3681         int pgrescued = 0;
3682         int i;
3683
3684         for (i = 0; i < nr_pages; i++) {
3685                 struct page *page = pages[i];
3686                 struct zone *pagezone;
3687
3688                 pgscanned++;
3689                 pagezone = page_zone(page);
3690                 if (pagezone != zone) {
3691                         if (zone)
3692                                 spin_unlock_irq(&zone->lru_lock);
3693                         zone = pagezone;
3694                         spin_lock_irq(&zone->lru_lock);
3695                 }
3696                 lruvec = mem_cgroup_page_lruvec(page, zone);
3697
3698                 if (!PageLRU(page) || !PageUnevictable(page))
3699                         continue;
3700
3701                 if (page_evictable(page)) {
3702                         enum lru_list lru = page_lru_base_type(page);
3703
3704                         VM_BUG_ON(PageActive(page));
3705                         ClearPageUnevictable(page);
3706                         del_page_from_lru_list(page, lruvec, LRU_UNEVICTABLE);
3707                         add_page_to_lru_list(page, lruvec, lru);
3708                         pgrescued++;
3709                 }
3710         }
3711
3712         if (zone) {
3713                 __count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
3714                 __count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned);
3715                 spin_unlock_irq(&zone->lru_lock);
3716         }
3717 }
3718 #endif /* CONFIG_SHMEM */
3719
3720 static void warn_scan_unevictable_pages(void)
3721 {
3722         printk_once(KERN_WARNING
3723                     "%s: The scan_unevictable_pages sysctl/node-interface has been "
3724                     "disabled for lack of a legitimate use case.  If you have "
3725                     "one, please send an email to linux-mm@kvack.org.\n",
3726                     current->comm);
3727 }
3728
3729 /*
3730  * scan_unevictable_pages [vm] sysctl handler.  On demand re-scan of
3731  * all nodes' unevictable lists for evictable pages
3732  */
3733 unsigned long scan_unevictable_pages;
3734
3735 int scan_unevictable_handler(struct ctl_table *table, int write,
3736                            void __user *buffer,
3737                            size_t *length, loff_t *ppos)
3738 {
3739         warn_scan_unevictable_pages();
3740         proc_doulongvec_minmax(table, write, buffer, length, ppos);
3741         scan_unevictable_pages = 0;
3742         return 0;
3743 }
3744
3745 #ifdef CONFIG_NUMA
3746 /*
3747  * per node 'scan_unevictable_pages' attribute.  On demand re-scan of
3748  * a specified node's per zone unevictable lists for evictable pages.
3749  */
3750
3751 static ssize_t read_scan_unevictable_node(struct device *dev,
3752                                           struct device_attribute *attr,
3753                                           char *buf)
3754 {
3755         warn_scan_unevictable_pages();
3756         return sprintf(buf, "0\n");     /* always zero; should fit... */
3757 }
3758
3759 static ssize_t write_scan_unevictable_node(struct device *dev,
3760                                            struct device_attribute *attr,
3761                                         const char *buf, size_t count)
3762 {
3763         warn_scan_unevictable_pages();
3764         return 1;
3765 }
3766
3767
3768 static DEVICE_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
3769                         read_scan_unevictable_node,
3770                         write_scan_unevictable_node);
3771
3772 int scan_unevictable_register_node(struct node *node)
3773 {
3774         return device_create_file(&node->dev, &dev_attr_scan_unevictable_pages);
3775 }
3776
3777 void scan_unevictable_unregister_node(struct node *node)
3778 {
3779         device_remove_file(&node->dev, &dev_attr_scan_unevictable_pages);
3780 }
3781 #endif