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mm/vmscan.c: fix mapping use after free
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CommitLineData
1da177e4
LT
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>
5a0e3ad6 16#include <linux/gfp.h>
1da177e4
LT
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>
e129b5c2 22#include <linux/vmstat.h>
1da177e4
LT
23#include <linux/file.h>
24#include <linux/writeback.h>
25#include <linux/blkdev.h>
26#include <linux/buffer_head.h> /* for try_to_release_page(),
27 buffer_heads_over_limit */
28#include <linux/mm_inline.h>
29#include <linux/pagevec.h>
30#include <linux/backing-dev.h>
31#include <linux/rmap.h>
32#include <linux/topology.h>
33#include <linux/cpu.h>
34#include <linux/cpuset.h>
35#include <linux/notifier.h>
36#include <linux/rwsem.h>
248a0301 37#include <linux/delay.h>
3218ae14 38#include <linux/kthread.h>
7dfb7103 39#include <linux/freezer.h>
66e1707b 40#include <linux/memcontrol.h>
873b4771 41#include <linux/delayacct.h>
af936a16 42#include <linux/sysctl.h>
1da177e4
LT
43
44#include <asm/tlbflush.h>
45#include <asm/div64.h>
46
47#include <linux/swapops.h>
48
0f8053a5
NP
49#include "internal.h"
50
1da177e4 51struct scan_control {
1da177e4
LT
52 /* Incremented by the number of inactive pages that were scanned */
53 unsigned long nr_scanned;
54
a79311c1
RR
55 /* Number of pages freed so far during a call to shrink_zones() */
56 unsigned long nr_reclaimed;
57
22fba335
KM
58 /* How many pages shrink_list() should reclaim */
59 unsigned long nr_to_reclaim;
60
7b51755c
KM
61 unsigned long hibernation_mode;
62
1da177e4 63 /* This context's GFP mask */
6daa0e28 64 gfp_t gfp_mask;
1da177e4
LT
65
66 int may_writepage;
67
a6dc60f8
JW
68 /* Can mapped pages be reclaimed? */
69 int may_unmap;
f1fd1067 70
2e2e4259
KM
71 /* Can pages be swapped as part of reclaim? */
72 int may_swap;
73
d6277db4 74 int swappiness;
408d8544 75
5ad333eb 76 int order;
66e1707b 77
5f53e762
KM
78 /*
79 * Intend to reclaim enough contenious memory rather than to reclaim
80 * enough amount memory. I.e, it's the mode for high order allocation.
81 */
82 bool lumpy_reclaim_mode;
83
66e1707b
BS
84 /* Which cgroup do we reclaim from */
85 struct mem_cgroup *mem_cgroup;
86
327c0e96
KH
87 /*
88 * Nodemask of nodes allowed by the caller. If NULL, all nodes
89 * are scanned.
90 */
91 nodemask_t *nodemask;
1da177e4
LT
92};
93
1da177e4
LT
94#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
95
96#ifdef ARCH_HAS_PREFETCH
97#define prefetch_prev_lru_page(_page, _base, _field) \
98 do { \
99 if ((_page)->lru.prev != _base) { \
100 struct page *prev; \
101 \
102 prev = lru_to_page(&(_page->lru)); \
103 prefetch(&prev->_field); \
104 } \
105 } while (0)
106#else
107#define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
108#endif
109
110#ifdef ARCH_HAS_PREFETCHW
111#define prefetchw_prev_lru_page(_page, _base, _field) \
112 do { \
113 if ((_page)->lru.prev != _base) { \
114 struct page *prev; \
115 \
116 prev = lru_to_page(&(_page->lru)); \
117 prefetchw(&prev->_field); \
118 } \
119 } while (0)
120#else
121#define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
122#endif
123
124/*
125 * From 0 .. 100. Higher means more swappy.
126 */
127int vm_swappiness = 60;
bd1e22b8 128long vm_total_pages; /* The total number of pages which the VM controls */
1da177e4
LT
129
130static LIST_HEAD(shrinker_list);
131static DECLARE_RWSEM(shrinker_rwsem);
132
00f0b825 133#ifdef CONFIG_CGROUP_MEM_RES_CTLR
e72e2bd6 134#define scanning_global_lru(sc) (!(sc)->mem_cgroup)
91a45470 135#else
e72e2bd6 136#define scanning_global_lru(sc) (1)
91a45470
KH
137#endif
138
6e901571
KM
139static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone,
140 struct scan_control *sc)
141{
e72e2bd6 142 if (!scanning_global_lru(sc))
3e2f41f1
KM
143 return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone);
144
6e901571
KM
145 return &zone->reclaim_stat;
146}
147
0b217676
VL
148static unsigned long zone_nr_lru_pages(struct zone *zone,
149 struct scan_control *sc, enum lru_list lru)
c9f299d9 150{
e72e2bd6 151 if (!scanning_global_lru(sc))
a3d8e054
KM
152 return mem_cgroup_zone_nr_pages(sc->mem_cgroup, zone, lru);
153
c9f299d9
KM
154 return zone_page_state(zone, NR_LRU_BASE + lru);
155}
156
157
1da177e4
LT
158/*
159 * Add a shrinker callback to be called from the vm
160 */
8e1f936b 161void register_shrinker(struct shrinker *shrinker)
1da177e4 162{
8e1f936b
RR
163 shrinker->nr = 0;
164 down_write(&shrinker_rwsem);
165 list_add_tail(&shrinker->list, &shrinker_list);
166 up_write(&shrinker_rwsem);
1da177e4 167}
8e1f936b 168EXPORT_SYMBOL(register_shrinker);
1da177e4
LT
169
170/*
171 * Remove one
172 */
8e1f936b 173void unregister_shrinker(struct shrinker *shrinker)
1da177e4
LT
174{
175 down_write(&shrinker_rwsem);
176 list_del(&shrinker->list);
177 up_write(&shrinker_rwsem);
1da177e4 178}
8e1f936b 179EXPORT_SYMBOL(unregister_shrinker);
1da177e4
LT
180
181#define SHRINK_BATCH 128
182/*
183 * Call the shrink functions to age shrinkable caches
184 *
185 * Here we assume it costs one seek to replace a lru page and that it also
186 * takes a seek to recreate a cache object. With this in mind we age equal
187 * percentages of the lru and ageable caches. This should balance the seeks
188 * generated by these structures.
189 *
183ff22b 190 * If the vm encountered mapped pages on the LRU it increase the pressure on
1da177e4
LT
191 * slab to avoid swapping.
192 *
193 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
194 *
195 * `lru_pages' represents the number of on-LRU pages in all the zones which
196 * are eligible for the caller's allocation attempt. It is used for balancing
197 * slab reclaim versus page reclaim.
b15e0905
AM
198 *
199 * Returns the number of slab objects which we shrunk.
1da177e4 200 */
69e05944
AM
201unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
202 unsigned long lru_pages)
1da177e4
LT
203{
204 struct shrinker *shrinker;
69e05944 205 unsigned long ret = 0;
1da177e4
LT
206
207 if (scanned == 0)
208 scanned = SWAP_CLUSTER_MAX;
209
210 if (!down_read_trylock(&shrinker_rwsem))
b15e0905 211 return 1; /* Assume we'll be able to shrink next time */
1da177e4
LT
212
213 list_for_each_entry(shrinker, &shrinker_list, list) {
214 unsigned long long delta;
215 unsigned long total_scan;
7f8275d0 216 unsigned long max_pass;
1da177e4 217
7f8275d0 218 max_pass = (*shrinker->shrink)(shrinker, 0, gfp_mask);
1da177e4 219 delta = (4 * scanned) / shrinker->seeks;
ea164d73 220 delta *= max_pass;
1da177e4
LT
221 do_div(delta, lru_pages + 1);
222 shrinker->nr += delta;
ea164d73 223 if (shrinker->nr < 0) {
88c3bd70
DR
224 printk(KERN_ERR "shrink_slab: %pF negative objects to "
225 "delete nr=%ld\n",
226 shrinker->shrink, shrinker->nr);
ea164d73
AA
227 shrinker->nr = max_pass;
228 }
229
230 /*
231 * Avoid risking looping forever due to too large nr value:
232 * never try to free more than twice the estimate number of
233 * freeable entries.
234 */
235 if (shrinker->nr > max_pass * 2)
236 shrinker->nr = max_pass * 2;
1da177e4
LT
237
238 total_scan = shrinker->nr;
239 shrinker->nr = 0;
240
241 while (total_scan >= SHRINK_BATCH) {
242 long this_scan = SHRINK_BATCH;
243 int shrink_ret;
b15e0905 244 int nr_before;
1da177e4 245
7f8275d0
DC
246 nr_before = (*shrinker->shrink)(shrinker, 0, gfp_mask);
247 shrink_ret = (*shrinker->shrink)(shrinker, this_scan,
248 gfp_mask);
1da177e4
LT
249 if (shrink_ret == -1)
250 break;
b15e0905
AM
251 if (shrink_ret < nr_before)
252 ret += nr_before - shrink_ret;
f8891e5e 253 count_vm_events(SLABS_SCANNED, this_scan);
1da177e4
LT
254 total_scan -= this_scan;
255
256 cond_resched();
257 }
258
259 shrinker->nr += total_scan;
260 }
261 up_read(&shrinker_rwsem);
b15e0905 262 return ret;
1da177e4
LT
263}
264
1da177e4
LT
265static inline int is_page_cache_freeable(struct page *page)
266{
ceddc3a5
JW
267 /*
268 * A freeable page cache page is referenced only by the caller
269 * that isolated the page, the page cache radix tree and
270 * optional buffer heads at page->private.
271 */
edcf4748 272 return page_count(page) - page_has_private(page) == 2;
1da177e4
LT
273}
274
275static int may_write_to_queue(struct backing_dev_info *bdi)
276{
930d9152 277 if (current->flags & PF_SWAPWRITE)
1da177e4
LT
278 return 1;
279 if (!bdi_write_congested(bdi))
280 return 1;
281 if (bdi == current->backing_dev_info)
282 return 1;
283 return 0;
284}
285
286/*
287 * We detected a synchronous write error writing a page out. Probably
288 * -ENOSPC. We need to propagate that into the address_space for a subsequent
289 * fsync(), msync() or close().
290 *
291 * The tricky part is that after writepage we cannot touch the mapping: nothing
292 * prevents it from being freed up. But we have a ref on the page and once
293 * that page is locked, the mapping is pinned.
294 *
295 * We're allowed to run sleeping lock_page() here because we know the caller has
296 * __GFP_FS.
297 */
298static void handle_write_error(struct address_space *mapping,
299 struct page *page, int error)
300{
a6aa62a0 301 lock_page_nosync(page);
3e9f45bd
GC
302 if (page_mapping(page) == mapping)
303 mapping_set_error(mapping, error);
1da177e4
LT
304 unlock_page(page);
305}
306
c661b078
AW
307/* Request for sync pageout. */
308enum pageout_io {
309 PAGEOUT_IO_ASYNC,
310 PAGEOUT_IO_SYNC,
311};
312
04e62a29
CL
313/* possible outcome of pageout() */
314typedef enum {
315 /* failed to write page out, page is locked */
316 PAGE_KEEP,
317 /* move page to the active list, page is locked */
318 PAGE_ACTIVATE,
319 /* page has been sent to the disk successfully, page is unlocked */
320 PAGE_SUCCESS,
321 /* page is clean and locked */
322 PAGE_CLEAN,
323} pageout_t;
324
1da177e4 325/*
1742f19f
AM
326 * pageout is called by shrink_page_list() for each dirty page.
327 * Calls ->writepage().
1da177e4 328 */
c661b078
AW
329static pageout_t pageout(struct page *page, struct address_space *mapping,
330 enum pageout_io sync_writeback)
1da177e4
LT
331{
332 /*
333 * If the page is dirty, only perform writeback if that write
334 * will be non-blocking. To prevent this allocation from being
335 * stalled by pagecache activity. But note that there may be
336 * stalls if we need to run get_block(). We could test
337 * PagePrivate for that.
338 *
6aceb53b 339 * If this process is currently in __generic_file_aio_write() against
1da177e4
LT
340 * this page's queue, we can perform writeback even if that
341 * will block.
342 *
343 * If the page is swapcache, write it back even if that would
344 * block, for some throttling. This happens by accident, because
345 * swap_backing_dev_info is bust: it doesn't reflect the
346 * congestion state of the swapdevs. Easy to fix, if needed.
1da177e4
LT
347 */
348 if (!is_page_cache_freeable(page))
349 return PAGE_KEEP;
350 if (!mapping) {
351 /*
352 * Some data journaling orphaned pages can have
353 * page->mapping == NULL while being dirty with clean buffers.
354 */
266cf658 355 if (page_has_private(page)) {
1da177e4
LT
356 if (try_to_free_buffers(page)) {
357 ClearPageDirty(page);
d40cee24 358 printk("%s: orphaned page\n", __func__);
1da177e4
LT
359 return PAGE_CLEAN;
360 }
361 }
362 return PAGE_KEEP;
363 }
364 if (mapping->a_ops->writepage == NULL)
365 return PAGE_ACTIVATE;
366 if (!may_write_to_queue(mapping->backing_dev_info))
367 return PAGE_KEEP;
368
369 if (clear_page_dirty_for_io(page)) {
370 int res;
371 struct writeback_control wbc = {
372 .sync_mode = WB_SYNC_NONE,
373 .nr_to_write = SWAP_CLUSTER_MAX,
111ebb6e
OH
374 .range_start = 0,
375 .range_end = LLONG_MAX,
1da177e4
LT
376 .nonblocking = 1,
377 .for_reclaim = 1,
378 };
379
380 SetPageReclaim(page);
381 res = mapping->a_ops->writepage(page, &wbc);
382 if (res < 0)
383 handle_write_error(mapping, page, res);
994fc28c 384 if (res == AOP_WRITEPAGE_ACTIVATE) {
1da177e4
LT
385 ClearPageReclaim(page);
386 return PAGE_ACTIVATE;
387 }
c661b078
AW
388
389 /*
390 * Wait on writeback if requested to. This happens when
391 * direct reclaiming a large contiguous area and the
392 * first attempt to free a range of pages fails.
393 */
394 if (PageWriteback(page) && sync_writeback == PAGEOUT_IO_SYNC)
395 wait_on_page_writeback(page);
396
1da177e4
LT
397 if (!PageWriteback(page)) {
398 /* synchronous write or broken a_ops? */
399 ClearPageReclaim(page);
400 }
e129b5c2 401 inc_zone_page_state(page, NR_VMSCAN_WRITE);
1da177e4
LT
402 return PAGE_SUCCESS;
403 }
404
405 return PAGE_CLEAN;
406}
407
a649fd92 408/*
e286781d
NP
409 * Same as remove_mapping, but if the page is removed from the mapping, it
410 * gets returned with a refcount of 0.
a649fd92 411 */
e286781d 412static int __remove_mapping(struct address_space *mapping, struct page *page)
49d2e9cc 413{
28e4d965
NP
414 BUG_ON(!PageLocked(page));
415 BUG_ON(mapping != page_mapping(page));
49d2e9cc 416
19fd6231 417 spin_lock_irq(&mapping->tree_lock);
49d2e9cc 418 /*
0fd0e6b0
NP
419 * The non racy check for a busy page.
420 *
421 * Must be careful with the order of the tests. When someone has
422 * a ref to the page, it may be possible that they dirty it then
423 * drop the reference. So if PageDirty is tested before page_count
424 * here, then the following race may occur:
425 *
426 * get_user_pages(&page);
427 * [user mapping goes away]
428 * write_to(page);
429 * !PageDirty(page) [good]
430 * SetPageDirty(page);
431 * put_page(page);
432 * !page_count(page) [good, discard it]
433 *
434 * [oops, our write_to data is lost]
435 *
436 * Reversing the order of the tests ensures such a situation cannot
437 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
438 * load is not satisfied before that of page->_count.
439 *
440 * Note that if SetPageDirty is always performed via set_page_dirty,
441 * and thus under tree_lock, then this ordering is not required.
49d2e9cc 442 */
e286781d 443 if (!page_freeze_refs(page, 2))
49d2e9cc 444 goto cannot_free;
e286781d
NP
445 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
446 if (unlikely(PageDirty(page))) {
447 page_unfreeze_refs(page, 2);
49d2e9cc 448 goto cannot_free;
e286781d 449 }
49d2e9cc
CL
450
451 if (PageSwapCache(page)) {
452 swp_entry_t swap = { .val = page_private(page) };
453 __delete_from_swap_cache(page);
19fd6231 454 spin_unlock_irq(&mapping->tree_lock);
cb4b86ba 455 swapcache_free(swap, page);
e286781d
NP
456 } else {
457 __remove_from_page_cache(page);
19fd6231 458 spin_unlock_irq(&mapping->tree_lock);
e767e056 459 mem_cgroup_uncharge_cache_page(page);
49d2e9cc
CL
460 }
461
49d2e9cc
CL
462 return 1;
463
464cannot_free:
19fd6231 465 spin_unlock_irq(&mapping->tree_lock);
49d2e9cc
CL
466 return 0;
467}
468
e286781d
NP
469/*
470 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
471 * someone else has a ref on the page, abort and return 0. If it was
472 * successfully detached, return 1. Assumes the caller has a single ref on
473 * this page.
474 */
475int remove_mapping(struct address_space *mapping, struct page *page)
476{
477 if (__remove_mapping(mapping, page)) {
478 /*
479 * Unfreezing the refcount with 1 rather than 2 effectively
480 * drops the pagecache ref for us without requiring another
481 * atomic operation.
482 */
483 page_unfreeze_refs(page, 1);
484 return 1;
485 }
486 return 0;
487}
488
894bc310
LS
489/**
490 * putback_lru_page - put previously isolated page onto appropriate LRU list
491 * @page: page to be put back to appropriate lru list
492 *
493 * Add previously isolated @page to appropriate LRU list.
494 * Page may still be unevictable for other reasons.
495 *
496 * lru_lock must not be held, interrupts must be enabled.
497 */
894bc310
LS
498void putback_lru_page(struct page *page)
499{
500 int lru;
501 int active = !!TestClearPageActive(page);
bbfd28ee 502 int was_unevictable = PageUnevictable(page);
894bc310
LS
503
504 VM_BUG_ON(PageLRU(page));
505
506redo:
507 ClearPageUnevictable(page);
508
509 if (page_evictable(page, NULL)) {
510 /*
511 * For evictable pages, we can use the cache.
512 * In event of a race, worst case is we end up with an
513 * unevictable page on [in]active list.
514 * We know how to handle that.
515 */
401a8e1c 516 lru = active + page_lru_base_type(page);
894bc310
LS
517 lru_cache_add_lru(page, lru);
518 } else {
519 /*
520 * Put unevictable pages directly on zone's unevictable
521 * list.
522 */
523 lru = LRU_UNEVICTABLE;
524 add_page_to_unevictable_list(page);
6a7b9548
JW
525 /*
526 * When racing with an mlock clearing (page is
527 * unlocked), make sure that if the other thread does
528 * not observe our setting of PG_lru and fails
529 * isolation, we see PG_mlocked cleared below and move
530 * the page back to the evictable list.
531 *
532 * The other side is TestClearPageMlocked().
533 */
534 smp_mb();
894bc310 535 }
894bc310
LS
536
537 /*
538 * page's status can change while we move it among lru. If an evictable
539 * page is on unevictable list, it never be freed. To avoid that,
540 * check after we added it to the list, again.
541 */
542 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
543 if (!isolate_lru_page(page)) {
544 put_page(page);
545 goto redo;
546 }
547 /* This means someone else dropped this page from LRU
548 * So, it will be freed or putback to LRU again. There is
549 * nothing to do here.
550 */
551 }
552
bbfd28ee
LS
553 if (was_unevictable && lru != LRU_UNEVICTABLE)
554 count_vm_event(UNEVICTABLE_PGRESCUED);
555 else if (!was_unevictable && lru == LRU_UNEVICTABLE)
556 count_vm_event(UNEVICTABLE_PGCULLED);
557
894bc310
LS
558 put_page(page); /* drop ref from isolate */
559}
560
dfc8d636
JW
561enum page_references {
562 PAGEREF_RECLAIM,
563 PAGEREF_RECLAIM_CLEAN,
64574746 564 PAGEREF_KEEP,
dfc8d636
JW
565 PAGEREF_ACTIVATE,
566};
567
568static enum page_references page_check_references(struct page *page,
569 struct scan_control *sc)
570{
64574746 571 int referenced_ptes, referenced_page;
dfc8d636 572 unsigned long vm_flags;
dfc8d636 573
64574746
JW
574 referenced_ptes = page_referenced(page, 1, sc->mem_cgroup, &vm_flags);
575 referenced_page = TestClearPageReferenced(page);
dfc8d636
JW
576
577 /* Lumpy reclaim - ignore references */
5f53e762 578 if (sc->lumpy_reclaim_mode)
dfc8d636
JW
579 return PAGEREF_RECLAIM;
580
581 /*
582 * Mlock lost the isolation race with us. Let try_to_unmap()
583 * move the page to the unevictable list.
584 */
585 if (vm_flags & VM_LOCKED)
586 return PAGEREF_RECLAIM;
587
64574746
JW
588 if (referenced_ptes) {
589 if (PageAnon(page))
590 return PAGEREF_ACTIVATE;
591 /*
592 * All mapped pages start out with page table
593 * references from the instantiating fault, so we need
594 * to look twice if a mapped file page is used more
595 * than once.
596 *
597 * Mark it and spare it for another trip around the
598 * inactive list. Another page table reference will
599 * lead to its activation.
600 *
601 * Note: the mark is set for activated pages as well
602 * so that recently deactivated but used pages are
603 * quickly recovered.
604 */
605 SetPageReferenced(page);
606
607 if (referenced_page)
608 return PAGEREF_ACTIVATE;
609
610 return PAGEREF_KEEP;
611 }
dfc8d636
JW
612
613 /* Reclaim if clean, defer dirty pages to writeback */
64574746
JW
614 if (referenced_page)
615 return PAGEREF_RECLAIM_CLEAN;
616
617 return PAGEREF_RECLAIM;
dfc8d636
JW
618}
619
1da177e4 620/*
1742f19f 621 * shrink_page_list() returns the number of reclaimed pages
1da177e4 622 */
1742f19f 623static unsigned long shrink_page_list(struct list_head *page_list,
c661b078
AW
624 struct scan_control *sc,
625 enum pageout_io sync_writeback)
1da177e4
LT
626{
627 LIST_HEAD(ret_pages);
628 struct pagevec freed_pvec;
629 int pgactivate = 0;
05ff5137 630 unsigned long nr_reclaimed = 0;
1da177e4
LT
631
632 cond_resched();
633
634 pagevec_init(&freed_pvec, 1);
635 while (!list_empty(page_list)) {
dfc8d636 636 enum page_references references;
1da177e4
LT
637 struct address_space *mapping;
638 struct page *page;
639 int may_enter_fs;
1da177e4
LT
640
641 cond_resched();
642
643 page = lru_to_page(page_list);
644 list_del(&page->lru);
645
529ae9aa 646 if (!trylock_page(page))
1da177e4
LT
647 goto keep;
648
725d704e 649 VM_BUG_ON(PageActive(page));
1da177e4
LT
650
651 sc->nr_scanned++;
80e43426 652
b291f000
NP
653 if (unlikely(!page_evictable(page, NULL)))
654 goto cull_mlocked;
894bc310 655
a6dc60f8 656 if (!sc->may_unmap && page_mapped(page))
80e43426
CL
657 goto keep_locked;
658
1da177e4
LT
659 /* Double the slab pressure for mapped and swapcache pages */
660 if (page_mapped(page) || PageSwapCache(page))
661 sc->nr_scanned++;
662
c661b078
AW
663 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
664 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
665
666 if (PageWriteback(page)) {
667 /*
668 * Synchronous reclaim is performed in two passes,
669 * first an asynchronous pass over the list to
670 * start parallel writeback, and a second synchronous
671 * pass to wait for the IO to complete. Wait here
672 * for any page for which writeback has already
673 * started.
674 */
675 if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs)
676 wait_on_page_writeback(page);
4dd4b920 677 else
c661b078
AW
678 goto keep_locked;
679 }
1da177e4 680
dfc8d636
JW
681 references = page_check_references(page, sc);
682 switch (references) {
683 case PAGEREF_ACTIVATE:
1da177e4 684 goto activate_locked;
64574746
JW
685 case PAGEREF_KEEP:
686 goto keep_locked;
dfc8d636
JW
687 case PAGEREF_RECLAIM:
688 case PAGEREF_RECLAIM_CLEAN:
689 ; /* try to reclaim the page below */
690 }
1da177e4 691
1da177e4
LT
692 /*
693 * Anonymous process memory has backing store?
694 * Try to allocate it some swap space here.
695 */
b291f000 696 if (PageAnon(page) && !PageSwapCache(page)) {
63eb6b93
HD
697 if (!(sc->gfp_mask & __GFP_IO))
698 goto keep_locked;
ac47b003 699 if (!add_to_swap(page))
1da177e4 700 goto activate_locked;
63eb6b93 701 may_enter_fs = 1;
b291f000 702 }
1da177e4
LT
703
704 mapping = page_mapping(page);
1da177e4
LT
705
706 /*
707 * The page is mapped into the page tables of one or more
708 * processes. Try to unmap it here.
709 */
710 if (page_mapped(page) && mapping) {
14fa31b8 711 switch (try_to_unmap(page, TTU_UNMAP)) {
1da177e4
LT
712 case SWAP_FAIL:
713 goto activate_locked;
714 case SWAP_AGAIN:
715 goto keep_locked;
b291f000
NP
716 case SWAP_MLOCK:
717 goto cull_mlocked;
1da177e4
LT
718 case SWAP_SUCCESS:
719 ; /* try to free the page below */
720 }
721 }
722
723 if (PageDirty(page)) {
dfc8d636 724 if (references == PAGEREF_RECLAIM_CLEAN)
1da177e4 725 goto keep_locked;
4dd4b920 726 if (!may_enter_fs)
1da177e4 727 goto keep_locked;
52a8363e 728 if (!sc->may_writepage)
1da177e4
LT
729 goto keep_locked;
730
731 /* Page is dirty, try to write it out here */
c661b078 732 switch (pageout(page, mapping, sync_writeback)) {
1da177e4
LT
733 case PAGE_KEEP:
734 goto keep_locked;
735 case PAGE_ACTIVATE:
736 goto activate_locked;
737 case PAGE_SUCCESS:
4dd4b920 738 if (PageWriteback(page) || PageDirty(page))
1da177e4
LT
739 goto keep;
740 /*
741 * A synchronous write - probably a ramdisk. Go
742 * ahead and try to reclaim the page.
743 */
529ae9aa 744 if (!trylock_page(page))
1da177e4
LT
745 goto keep;
746 if (PageDirty(page) || PageWriteback(page))
747 goto keep_locked;
748 mapping = page_mapping(page);
749 case PAGE_CLEAN:
750 ; /* try to free the page below */
751 }
752 }
753
754 /*
755 * If the page has buffers, try to free the buffer mappings
756 * associated with this page. If we succeed we try to free
757 * the page as well.
758 *
759 * We do this even if the page is PageDirty().
760 * try_to_release_page() does not perform I/O, but it is
761 * possible for a page to have PageDirty set, but it is actually
762 * clean (all its buffers are clean). This happens if the
763 * buffers were written out directly, with submit_bh(). ext3
894bc310 764 * will do this, as well as the blockdev mapping.
1da177e4
LT
765 * try_to_release_page() will discover that cleanness and will
766 * drop the buffers and mark the page clean - it can be freed.
767 *
768 * Rarely, pages can have buffers and no ->mapping. These are
769 * the pages which were not successfully invalidated in
770 * truncate_complete_page(). We try to drop those buffers here
771 * and if that worked, and the page is no longer mapped into
772 * process address space (page_count == 1) it can be freed.
773 * Otherwise, leave the page on the LRU so it is swappable.
774 */
266cf658 775 if (page_has_private(page)) {
1da177e4
LT
776 if (!try_to_release_page(page, sc->gfp_mask))
777 goto activate_locked;
e286781d
NP
778 if (!mapping && page_count(page) == 1) {
779 unlock_page(page);
780 if (put_page_testzero(page))
781 goto free_it;
782 else {
783 /*
784 * rare race with speculative reference.
785 * the speculative reference will free
786 * this page shortly, so we may
787 * increment nr_reclaimed here (and
788 * leave it off the LRU).
789 */
790 nr_reclaimed++;
791 continue;
792 }
793 }
1da177e4
LT
794 }
795
e286781d 796 if (!mapping || !__remove_mapping(mapping, page))
49d2e9cc 797 goto keep_locked;
1da177e4 798
a978d6f5
NP
799 /*
800 * At this point, we have no other references and there is
801 * no way to pick any more up (removed from LRU, removed
802 * from pagecache). Can use non-atomic bitops now (and
803 * we obviously don't have to worry about waking up a process
804 * waiting on the page lock, because there are no references.
805 */
806 __clear_page_locked(page);
e286781d 807free_it:
05ff5137 808 nr_reclaimed++;
e286781d
NP
809 if (!pagevec_add(&freed_pvec, page)) {
810 __pagevec_free(&freed_pvec);
811 pagevec_reinit(&freed_pvec);
812 }
1da177e4
LT
813 continue;
814
b291f000 815cull_mlocked:
63d6c5ad
HD
816 if (PageSwapCache(page))
817 try_to_free_swap(page);
b291f000
NP
818 unlock_page(page);
819 putback_lru_page(page);
820 continue;
821
1da177e4 822activate_locked:
68a22394
RR
823 /* Not a candidate for swapping, so reclaim swap space. */
824 if (PageSwapCache(page) && vm_swap_full())
a2c43eed 825 try_to_free_swap(page);
894bc310 826 VM_BUG_ON(PageActive(page));
1da177e4
LT
827 SetPageActive(page);
828 pgactivate++;
829keep_locked:
830 unlock_page(page);
831keep:
832 list_add(&page->lru, &ret_pages);
b291f000 833 VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
1da177e4
LT
834 }
835 list_splice(&ret_pages, page_list);
836 if (pagevec_count(&freed_pvec))
e286781d 837 __pagevec_free(&freed_pvec);
f8891e5e 838 count_vm_events(PGACTIVATE, pgactivate);
05ff5137 839 return nr_reclaimed;
1da177e4
LT
840}
841
5ad333eb
AW
842/*
843 * Attempt to remove the specified page from its LRU. Only take this page
844 * if it is of the appropriate PageActive status. Pages which are being
845 * freed elsewhere are also ignored.
846 *
847 * page: page to consider
848 * mode: one of the LRU isolation modes defined above
849 *
850 * returns 0 on success, -ve errno on failure.
851 */
4f98a2fe 852int __isolate_lru_page(struct page *page, int mode, int file)
5ad333eb
AW
853{
854 int ret = -EINVAL;
855
856 /* Only take pages on the LRU. */
857 if (!PageLRU(page))
858 return ret;
859
860 /*
861 * When checking the active state, we need to be sure we are
862 * dealing with comparible boolean values. Take the logical not
863 * of each.
864 */
865 if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode))
866 return ret;
867
6c0b1351 868 if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file)
4f98a2fe
RR
869 return ret;
870
894bc310
LS
871 /*
872 * When this function is being called for lumpy reclaim, we
873 * initially look into all LRU pages, active, inactive and
874 * unevictable; only give shrink_page_list evictable pages.
875 */
876 if (PageUnevictable(page))
877 return ret;
878
5ad333eb 879 ret = -EBUSY;
08e552c6 880
5ad333eb
AW
881 if (likely(get_page_unless_zero(page))) {
882 /*
883 * Be careful not to clear PageLRU until after we're
884 * sure the page is not being freed elsewhere -- the
885 * page release code relies on it.
886 */
887 ClearPageLRU(page);
888 ret = 0;
889 }
890
891 return ret;
892}
893
1da177e4
LT
894/*
895 * zone->lru_lock is heavily contended. Some of the functions that
896 * shrink the lists perform better by taking out a batch of pages
897 * and working on them outside the LRU lock.
898 *
899 * For pagecache intensive workloads, this function is the hottest
900 * spot in the kernel (apart from copy_*_user functions).
901 *
902 * Appropriate locks must be held before calling this function.
903 *
904 * @nr_to_scan: The number of pages to look through on the list.
905 * @src: The LRU list to pull pages off.
906 * @dst: The temp list to put pages on to.
907 * @scanned: The number of pages that were scanned.
5ad333eb
AW
908 * @order: The caller's attempted allocation order
909 * @mode: One of the LRU isolation modes
4f98a2fe 910 * @file: True [1] if isolating file [!anon] pages
1da177e4
LT
911 *
912 * returns how many pages were moved onto *@dst.
913 */
69e05944
AM
914static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
915 struct list_head *src, struct list_head *dst,
4f98a2fe 916 unsigned long *scanned, int order, int mode, int file)
1da177e4 917{
69e05944 918 unsigned long nr_taken = 0;
c9b02d97 919 unsigned long scan;
1da177e4 920
c9b02d97 921 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
5ad333eb
AW
922 struct page *page;
923 unsigned long pfn;
924 unsigned long end_pfn;
925 unsigned long page_pfn;
926 int zone_id;
927
1da177e4
LT
928 page = lru_to_page(src);
929 prefetchw_prev_lru_page(page, src, flags);
930
725d704e 931 VM_BUG_ON(!PageLRU(page));
8d438f96 932
4f98a2fe 933 switch (__isolate_lru_page(page, mode, file)) {
5ad333eb
AW
934 case 0:
935 list_move(&page->lru, dst);
2ffebca6 936 mem_cgroup_del_lru(page);
7c8ee9a8 937 nr_taken++;
5ad333eb
AW
938 break;
939
940 case -EBUSY:
941 /* else it is being freed elsewhere */
942 list_move(&page->lru, src);
2ffebca6 943 mem_cgroup_rotate_lru_list(page, page_lru(page));
5ad333eb 944 continue;
46453a6e 945
5ad333eb
AW
946 default:
947 BUG();
948 }
949
950 if (!order)
951 continue;
952
953 /*
954 * Attempt to take all pages in the order aligned region
955 * surrounding the tag page. Only take those pages of
956 * the same active state as that tag page. We may safely
957 * round the target page pfn down to the requested order
958 * as the mem_map is guarenteed valid out to MAX_ORDER,
959 * where that page is in a different zone we will detect
960 * it from its zone id and abort this block scan.
961 */
962 zone_id = page_zone_id(page);
963 page_pfn = page_to_pfn(page);
964 pfn = page_pfn & ~((1 << order) - 1);
965 end_pfn = pfn + (1 << order);
966 for (; pfn < end_pfn; pfn++) {
967 struct page *cursor_page;
968
969 /* The target page is in the block, ignore it. */
970 if (unlikely(pfn == page_pfn))
971 continue;
972
973 /* Avoid holes within the zone. */
974 if (unlikely(!pfn_valid_within(pfn)))
975 break;
976
977 cursor_page = pfn_to_page(pfn);
4f98a2fe 978
5ad333eb
AW
979 /* Check that we have not crossed a zone boundary. */
980 if (unlikely(page_zone_id(cursor_page) != zone_id))
981 continue;
de2e7567
MK
982
983 /*
984 * If we don't have enough swap space, reclaiming of
985 * anon page which don't already have a swap slot is
986 * pointless.
987 */
988 if (nr_swap_pages <= 0 && PageAnon(cursor_page) &&
989 !PageSwapCache(cursor_page))
990 continue;
991
ee993b13 992 if (__isolate_lru_page(cursor_page, mode, file) == 0) {
5ad333eb 993 list_move(&cursor_page->lru, dst);
cb4cbcf6 994 mem_cgroup_del_lru(cursor_page);
5ad333eb
AW
995 nr_taken++;
996 scan++;
5ad333eb
AW
997 }
998 }
1da177e4
LT
999 }
1000
1001 *scanned = scan;
1002 return nr_taken;
1003}
1004
66e1707b
BS
1005static unsigned long isolate_pages_global(unsigned long nr,
1006 struct list_head *dst,
1007 unsigned long *scanned, int order,
1008 int mode, struct zone *z,
4f98a2fe 1009 int active, int file)
66e1707b 1010{
4f98a2fe 1011 int lru = LRU_BASE;
66e1707b 1012 if (active)
4f98a2fe
RR
1013 lru += LRU_ACTIVE;
1014 if (file)
1015 lru += LRU_FILE;
1016 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
b7c46d15 1017 mode, file);
66e1707b
BS
1018}
1019
5ad333eb
AW
1020/*
1021 * clear_active_flags() is a helper for shrink_active_list(), clearing
1022 * any active bits from the pages in the list.
1023 */
4f98a2fe
RR
1024static unsigned long clear_active_flags(struct list_head *page_list,
1025 unsigned int *count)
5ad333eb
AW
1026{
1027 int nr_active = 0;
4f98a2fe 1028 int lru;
5ad333eb
AW
1029 struct page *page;
1030
4f98a2fe 1031 list_for_each_entry(page, page_list, lru) {
401a8e1c 1032 lru = page_lru_base_type(page);
5ad333eb 1033 if (PageActive(page)) {
4f98a2fe 1034 lru += LRU_ACTIVE;
5ad333eb
AW
1035 ClearPageActive(page);
1036 nr_active++;
1037 }
4f98a2fe
RR
1038 count[lru]++;
1039 }
5ad333eb
AW
1040
1041 return nr_active;
1042}
1043
62695a84
NP
1044/**
1045 * isolate_lru_page - tries to isolate a page from its LRU list
1046 * @page: page to isolate from its LRU list
1047 *
1048 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1049 * vmstat statistic corresponding to whatever LRU list the page was on.
1050 *
1051 * Returns 0 if the page was removed from an LRU list.
1052 * Returns -EBUSY if the page was not on an LRU list.
1053 *
1054 * The returned page will have PageLRU() cleared. If it was found on
894bc310
LS
1055 * the active list, it will have PageActive set. If it was found on
1056 * the unevictable list, it will have the PageUnevictable bit set. That flag
1057 * may need to be cleared by the caller before letting the page go.
62695a84
NP
1058 *
1059 * The vmstat statistic corresponding to the list on which the page was
1060 * found will be decremented.
1061 *
1062 * Restrictions:
1063 * (1) Must be called with an elevated refcount on the page. This is a
1064 * fundamentnal difference from isolate_lru_pages (which is called
1065 * without a stable reference).
1066 * (2) the lru_lock must not be held.
1067 * (3) interrupts must be enabled.
1068 */
1069int isolate_lru_page(struct page *page)
1070{
1071 int ret = -EBUSY;
1072
1073 if (PageLRU(page)) {
1074 struct zone *zone = page_zone(page);
1075
1076 spin_lock_irq(&zone->lru_lock);
1077 if (PageLRU(page) && get_page_unless_zero(page)) {
894bc310 1078 int lru = page_lru(page);
62695a84
NP
1079 ret = 0;
1080 ClearPageLRU(page);
4f98a2fe 1081
4f98a2fe 1082 del_page_from_lru_list(zone, page, lru);
62695a84
NP
1083 }
1084 spin_unlock_irq(&zone->lru_lock);
1085 }
1086 return ret;
1087}
1088
35cd7815
RR
1089/*
1090 * Are there way too many processes in the direct reclaim path already?
1091 */
1092static int too_many_isolated(struct zone *zone, int file,
1093 struct scan_control *sc)
1094{
1095 unsigned long inactive, isolated;
1096
1097 if (current_is_kswapd())
1098 return 0;
1099
1100 if (!scanning_global_lru(sc))
1101 return 0;
1102
1103 if (file) {
1104 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1105 isolated = zone_page_state(zone, NR_ISOLATED_FILE);
1106 } else {
1107 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1108 isolated = zone_page_state(zone, NR_ISOLATED_ANON);
1109 }
1110
1111 return isolated > inactive;
1112}
1113
1da177e4 1114/*
1742f19f
AM
1115 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1116 * of reclaimed pages
1da177e4 1117 */
1742f19f 1118static unsigned long shrink_inactive_list(unsigned long max_scan,
33c120ed
RR
1119 struct zone *zone, struct scan_control *sc,
1120 int priority, int file)
1da177e4
LT
1121{
1122 LIST_HEAD(page_list);
1123 struct pagevec pvec;
69e05944 1124 unsigned long nr_scanned = 0;
05ff5137 1125 unsigned long nr_reclaimed = 0;
6e901571 1126 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
78dc583d 1127
35cd7815 1128 while (unlikely(too_many_isolated(zone, file, sc))) {
58355c78 1129 congestion_wait(BLK_RW_ASYNC, HZ/10);
35cd7815
RR
1130
1131 /* We are about to die and free our memory. Return now. */
1132 if (fatal_signal_pending(current))
1133 return SWAP_CLUSTER_MAX;
1134 }
1135
1da177e4
LT
1136
1137 pagevec_init(&pvec, 1);
1138
1139 lru_add_drain();
1140 spin_lock_irq(&zone->lru_lock);
69e05944 1141 do {
1da177e4 1142 struct page *page;
69e05944
AM
1143 unsigned long nr_taken;
1144 unsigned long nr_scan;
1145 unsigned long nr_freed;
5ad333eb 1146 unsigned long nr_active;
4f98a2fe 1147 unsigned int count[NR_LRU_LISTS] = { 0, };
5f53e762 1148 int mode = sc->lumpy_reclaim_mode ? ISOLATE_BOTH : ISOLATE_INACTIVE;
a731286d
KM
1149 unsigned long nr_anon;
1150 unsigned long nr_file;
1da177e4 1151
b35ea17b 1152 if (scanning_global_lru(sc)) {
8b25c6d2
JW
1153 nr_taken = isolate_pages_global(SWAP_CLUSTER_MAX,
1154 &page_list, &nr_scan,
1155 sc->order, mode,
1156 zone, 0, file);
b35ea17b
KM
1157 zone->pages_scanned += nr_scan;
1158 if (current_is_kswapd())
1159 __count_zone_vm_events(PGSCAN_KSWAPD, zone,
1160 nr_scan);
1161 else
1162 __count_zone_vm_events(PGSCAN_DIRECT, zone,
1163 nr_scan);
8b25c6d2
JW
1164 } else {
1165 nr_taken = mem_cgroup_isolate_pages(SWAP_CLUSTER_MAX,
1166 &page_list, &nr_scan,
1167 sc->order, mode,
1168 zone, sc->mem_cgroup,
1169 0, file);
1170 /*
1171 * mem_cgroup_isolate_pages() keeps track of
1172 * scanned pages on its own.
1173 */
b35ea17b
KM
1174 }
1175
1176 if (nr_taken == 0)
1177 goto done;
1178
4f98a2fe 1179 nr_active = clear_active_flags(&page_list, count);
e9187bdc 1180 __count_vm_events(PGDEACTIVATE, nr_active);
5ad333eb 1181
4f98a2fe
RR
1182 __mod_zone_page_state(zone, NR_ACTIVE_FILE,
1183 -count[LRU_ACTIVE_FILE]);
1184 __mod_zone_page_state(zone, NR_INACTIVE_FILE,
1185 -count[LRU_INACTIVE_FILE]);
1186 __mod_zone_page_state(zone, NR_ACTIVE_ANON,
1187 -count[LRU_ACTIVE_ANON]);
1188 __mod_zone_page_state(zone, NR_INACTIVE_ANON,
1189 -count[LRU_INACTIVE_ANON]);
1190
a731286d
KM
1191 nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
1192 nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
1193 __mod_zone_page_state(zone, NR_ISOLATED_ANON, nr_anon);
1194 __mod_zone_page_state(zone, NR_ISOLATED_FILE, nr_file);
3e2f41f1 1195
62c0c2f1
HS
1196 reclaim_stat->recent_scanned[0] += nr_anon;
1197 reclaim_stat->recent_scanned[1] += nr_file;
3e2f41f1 1198
1da177e4
LT
1199 spin_unlock_irq(&zone->lru_lock);
1200
69e05944 1201 nr_scanned += nr_scan;
c661b078
AW
1202 nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC);
1203
1204 /*
1205 * If we are direct reclaiming for contiguous pages and we do
1206 * not reclaim everything in the list, try again and wait
1207 * for IO to complete. This will stall high-order allocations
1208 * but that should be acceptable to the caller
1209 */
1210 if (nr_freed < nr_taken && !current_is_kswapd() &&
5f53e762 1211 sc->lumpy_reclaim_mode) {
8aa7e847 1212 congestion_wait(BLK_RW_ASYNC, HZ/10);
c661b078
AW
1213
1214 /*
1215 * The attempt at page out may have made some
1216 * of the pages active, mark them inactive again.
1217 */
4f98a2fe 1218 nr_active = clear_active_flags(&page_list, count);
c661b078
AW
1219 count_vm_events(PGDEACTIVATE, nr_active);
1220
1221 nr_freed += shrink_page_list(&page_list, sc,
1222 PAGEOUT_IO_SYNC);
1223 }
1224
05ff5137 1225 nr_reclaimed += nr_freed;
b35ea17b 1226
a74609fa 1227 local_irq_disable();
b35ea17b 1228 if (current_is_kswapd())
f8891e5e 1229 __count_vm_events(KSWAPD_STEAL, nr_freed);
918d3f90 1230 __count_zone_vm_events(PGSTEAL, zone, nr_freed);
a74609fa
NP
1231
1232 spin_lock(&zone->lru_lock);
1da177e4
LT
1233 /*
1234 * Put back any unfreeable pages.
1235 */
1236 while (!list_empty(&page_list)) {
894bc310 1237 int lru;
1da177e4 1238 page = lru_to_page(&page_list);
725d704e 1239 VM_BUG_ON(PageLRU(page));
1da177e4 1240 list_del(&page->lru);
894bc310
LS
1241 if (unlikely(!page_evictable(page, NULL))) {
1242 spin_unlock_irq(&zone->lru_lock);
1243 putback_lru_page(page);
1244 spin_lock_irq(&zone->lru_lock);
1245 continue;
1246 }
1247 SetPageLRU(page);
1248 lru = page_lru(page);
1249 add_page_to_lru_list(zone, page, lru);
74a1c48f 1250 if (is_active_lru(lru)) {
b7c46d15 1251 int file = is_file_lru(lru);
6e901571 1252 reclaim_stat->recent_rotated[file]++;
4f98a2fe 1253 }
1da177e4
LT
1254 if (!pagevec_add(&pvec, page)) {
1255 spin_unlock_irq(&zone->lru_lock);
1256 __pagevec_release(&pvec);
1257 spin_lock_irq(&zone->lru_lock);
1258 }
1259 }
a731286d
KM
1260 __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
1261 __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
1262
69e05944 1263 } while (nr_scanned < max_scan);
b35ea17b 1264
1da177e4 1265done:
b35ea17b 1266 spin_unlock_irq(&zone->lru_lock);
1da177e4 1267 pagevec_release(&pvec);
05ff5137 1268 return nr_reclaimed;
1da177e4
LT
1269}
1270
3bb1a852
MB
1271/*
1272 * We are about to scan this zone at a certain priority level. If that priority
1273 * level is smaller (ie: more urgent) than the previous priority, then note
1274 * that priority level within the zone. This is done so that when the next
1275 * process comes in to scan this zone, it will immediately start out at this
1276 * priority level rather than having to build up its own scanning priority.
1277 * Here, this priority affects only the reclaim-mapped threshold.
1278 */
1279static inline void note_zone_scanning_priority(struct zone *zone, int priority)
1280{
1281 if (priority < zone->prev_priority)
1282 zone->prev_priority = priority;
1283}
1284
1da177e4
LT
1285/*
1286 * This moves pages from the active list to the inactive list.
1287 *
1288 * We move them the other way if the page is referenced by one or more
1289 * processes, from rmap.
1290 *
1291 * If the pages are mostly unmapped, the processing is fast and it is
1292 * appropriate to hold zone->lru_lock across the whole operation. But if
1293 * the pages are mapped, the processing is slow (page_referenced()) so we
1294 * should drop zone->lru_lock around each page. It's impossible to balance
1295 * this, so instead we remove the pages from the LRU while processing them.
1296 * It is safe to rely on PG_active against the non-LRU pages in here because
1297 * nobody will play with that bit on a non-LRU page.
1298 *
1299 * The downside is that we have to touch page->_count against each page.
1300 * But we had to alter page->flags anyway.
1301 */
1cfb419b 1302
3eb4140f
WF
1303static void move_active_pages_to_lru(struct zone *zone,
1304 struct list_head *list,
1305 enum lru_list lru)
1306{
1307 unsigned long pgmoved = 0;
1308 struct pagevec pvec;
1309 struct page *page;
1310
1311 pagevec_init(&pvec, 1);
1312
1313 while (!list_empty(list)) {
1314 page = lru_to_page(list);
3eb4140f
WF
1315
1316 VM_BUG_ON(PageLRU(page));
1317 SetPageLRU(page);
1318
3eb4140f
WF
1319 list_move(&page->lru, &zone->lru[lru].list);
1320 mem_cgroup_add_lru_list(page, lru);
1321 pgmoved++;
1322
1323 if (!pagevec_add(&pvec, page) || list_empty(list)) {
1324 spin_unlock_irq(&zone->lru_lock);
1325 if (buffer_heads_over_limit)
1326 pagevec_strip(&pvec);
1327 __pagevec_release(&pvec);
1328 spin_lock_irq(&zone->lru_lock);
1329 }
1330 }
1331 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1332 if (!is_active_lru(lru))
1333 __count_vm_events(PGDEACTIVATE, pgmoved);
1334}
1cfb419b 1335
1742f19f 1336static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
4f98a2fe 1337 struct scan_control *sc, int priority, int file)
1da177e4 1338{
44c241f1 1339 unsigned long nr_taken;
69e05944 1340 unsigned long pgscanned;
6fe6b7e3 1341 unsigned long vm_flags;
1da177e4 1342 LIST_HEAD(l_hold); /* The pages which were snipped off */
8cab4754 1343 LIST_HEAD(l_active);
b69408e8 1344 LIST_HEAD(l_inactive);
1da177e4 1345 struct page *page;
6e901571 1346 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
44c241f1 1347 unsigned long nr_rotated = 0;
1da177e4
LT
1348
1349 lru_add_drain();
1350 spin_lock_irq(&zone->lru_lock);
e72e2bd6 1351 if (scanning_global_lru(sc)) {
8b25c6d2
JW
1352 nr_taken = isolate_pages_global(nr_pages, &l_hold,
1353 &pgscanned, sc->order,
1354 ISOLATE_ACTIVE, zone,
1355 1, file);
1cfb419b 1356 zone->pages_scanned += pgscanned;
8b25c6d2
JW
1357 } else {
1358 nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold,
1359 &pgscanned, sc->order,
1360 ISOLATE_ACTIVE, zone,
1361 sc->mem_cgroup, 1, file);
1362 /*
1363 * mem_cgroup_isolate_pages() keeps track of
1364 * scanned pages on its own.
1365 */
4f98a2fe 1366 }
8b25c6d2 1367
b7c46d15 1368 reclaim_stat->recent_scanned[file] += nr_taken;
1cfb419b 1369
3eb4140f 1370 __count_zone_vm_events(PGREFILL, zone, pgscanned);
4f98a2fe 1371 if (file)
44c241f1 1372 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken);
4f98a2fe 1373 else
44c241f1 1374 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken);
a731286d 1375 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
1da177e4
LT
1376 spin_unlock_irq(&zone->lru_lock);
1377
1da177e4
LT
1378 while (!list_empty(&l_hold)) {
1379 cond_resched();
1380 page = lru_to_page(&l_hold);
1381 list_del(&page->lru);
7e9cd484 1382
894bc310
LS
1383 if (unlikely(!page_evictable(page, NULL))) {
1384 putback_lru_page(page);
1385 continue;
1386 }
1387
64574746 1388 if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) {
44c241f1 1389 nr_rotated++;
8cab4754
WF
1390 /*
1391 * Identify referenced, file-backed active pages and
1392 * give them one more trip around the active list. So
1393 * that executable code get better chances to stay in
1394 * memory under moderate memory pressure. Anon pages
1395 * are not likely to be evicted by use-once streaming
1396 * IO, plus JVM can create lots of anon VM_EXEC pages,
1397 * so we ignore them here.
1398 */
41e20983 1399 if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
8cab4754
WF
1400 list_add(&page->lru, &l_active);
1401 continue;
1402 }
1403 }
7e9cd484 1404
5205e56e 1405 ClearPageActive(page); /* we are de-activating */
1da177e4
LT
1406 list_add(&page->lru, &l_inactive);
1407 }
1408
b555749a 1409 /*
8cab4754 1410 * Move pages back to the lru list.
b555749a 1411 */
2a1dc509 1412 spin_lock_irq(&zone->lru_lock);
556adecb 1413 /*
8cab4754
WF
1414 * Count referenced pages from currently used mappings as rotated,
1415 * even though only some of them are actually re-activated. This
1416 * helps balance scan pressure between file and anonymous pages in
1417 * get_scan_ratio.
7e9cd484 1418 */
b7c46d15 1419 reclaim_stat->recent_rotated[file] += nr_rotated;
556adecb 1420
3eb4140f
WF
1421 move_active_pages_to_lru(zone, &l_active,
1422 LRU_ACTIVE + file * LRU_FILE);
1423 move_active_pages_to_lru(zone, &l_inactive,
1424 LRU_BASE + file * LRU_FILE);
a731286d 1425 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
f8891e5e 1426 spin_unlock_irq(&zone->lru_lock);
1da177e4
LT
1427}
1428
14797e23 1429static int inactive_anon_is_low_global(struct zone *zone)
f89eb90e
KM
1430{
1431 unsigned long active, inactive;
1432
1433 active = zone_page_state(zone, NR_ACTIVE_ANON);
1434 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1435
1436 if (inactive * zone->inactive_ratio < active)
1437 return 1;
1438
1439 return 0;
1440}
1441
14797e23
KM
1442/**
1443 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1444 * @zone: zone to check
1445 * @sc: scan control of this context
1446 *
1447 * Returns true if the zone does not have enough inactive anon pages,
1448 * meaning some active anon pages need to be deactivated.
1449 */
1450static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc)
1451{
1452 int low;
1453
e72e2bd6 1454 if (scanning_global_lru(sc))
14797e23
KM
1455 low = inactive_anon_is_low_global(zone);
1456 else
c772be93 1457 low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup);
14797e23
KM
1458 return low;
1459}
1460
56e49d21
RR
1461static int inactive_file_is_low_global(struct zone *zone)
1462{
1463 unsigned long active, inactive;
1464
1465 active = zone_page_state(zone, NR_ACTIVE_FILE);
1466 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1467
1468 return (active > inactive);
1469}
1470
1471/**
1472 * inactive_file_is_low - check if file pages need to be deactivated
1473 * @zone: zone to check
1474 * @sc: scan control of this context
1475 *
1476 * When the system is doing streaming IO, memory pressure here
1477 * ensures that active file pages get deactivated, until more
1478 * than half of the file pages are on the inactive list.
1479 *
1480 * Once we get to that situation, protect the system's working
1481 * set from being evicted by disabling active file page aging.
1482 *
1483 * This uses a different ratio than the anonymous pages, because
1484 * the page cache uses a use-once replacement algorithm.
1485 */
1486static int inactive_file_is_low(struct zone *zone, struct scan_control *sc)
1487{
1488 int low;
1489
1490 if (scanning_global_lru(sc))
1491 low = inactive_file_is_low_global(zone);
1492 else
1493 low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup);
1494 return low;
1495}
1496
b39415b2
RR
1497static int inactive_list_is_low(struct zone *zone, struct scan_control *sc,
1498 int file)
1499{
1500 if (file)
1501 return inactive_file_is_low(zone, sc);
1502 else
1503 return inactive_anon_is_low(zone, sc);
1504}
1505
4f98a2fe 1506static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
b69408e8
CL
1507 struct zone *zone, struct scan_control *sc, int priority)
1508{
4f98a2fe
RR
1509 int file = is_file_lru(lru);
1510
b39415b2
RR
1511 if (is_active_lru(lru)) {
1512 if (inactive_list_is_low(zone, sc, file))
1513 shrink_active_list(nr_to_scan, zone, sc, priority, file);
556adecb
RR
1514 return 0;
1515 }
1516
33c120ed 1517 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
4f98a2fe
RR
1518}
1519
76a33fc3
SL
1520/*
1521 * Smallish @nr_to_scan's are deposited in @nr_saved_scan,
1522 * until we collected @swap_cluster_max pages to scan.
1523 */
1524static unsigned long nr_scan_try_batch(unsigned long nr_to_scan,
1525 unsigned long *nr_saved_scan)
1526{
1527 unsigned long nr;
1528
1529 *nr_saved_scan += nr_to_scan;
1530 nr = *nr_saved_scan;
1531
1532 if (nr >= SWAP_CLUSTER_MAX)
1533 *nr_saved_scan = 0;
1534 else
1535 nr = 0;
1536
1537 return nr;
1538}
1539
4f98a2fe
RR
1540/*
1541 * Determine how aggressively the anon and file LRU lists should be
1542 * scanned. The relative value of each set of LRU lists is determined
1543 * by looking at the fraction of the pages scanned we did rotate back
1544 * onto the active list instead of evict.
1545 *
76a33fc3 1546 * nr[0] = anon pages to scan; nr[1] = file pages to scan
4f98a2fe 1547 */
76a33fc3
SL
1548static void get_scan_count(struct zone *zone, struct scan_control *sc,
1549 unsigned long *nr, int priority)
4f98a2fe
RR
1550{
1551 unsigned long anon, file, free;
1552 unsigned long anon_prio, file_prio;
1553 unsigned long ap, fp;
6e901571 1554 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
76a33fc3
SL
1555 u64 fraction[2], denominator;
1556 enum lru_list l;
1557 int noswap = 0;
1558
1559 /* If we have no swap space, do not bother scanning anon pages. */
1560 if (!sc->may_swap || (nr_swap_pages <= 0)) {
1561 noswap = 1;
1562 fraction[0] = 0;
1563 fraction[1] = 1;
1564 denominator = 1;
1565 goto out;
1566 }
4f98a2fe 1567
0b217676
VL
1568 anon = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) +
1569 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON);
1570 file = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) +
1571 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
b962716b 1572
e72e2bd6 1573 if (scanning_global_lru(sc)) {
eeee9a8c
KM
1574 free = zone_page_state(zone, NR_FREE_PAGES);
1575 /* If we have very few page cache pages,
1576 force-scan anon pages. */
41858966 1577 if (unlikely(file + free <= high_wmark_pages(zone))) {
76a33fc3
SL
1578 fraction[0] = 1;
1579 fraction[1] = 0;
1580 denominator = 1;
1581 goto out;
eeee9a8c 1582 }
4f98a2fe
RR
1583 }
1584
1585 /*
1586 * OK, so we have swap space and a fair amount of page cache
1587 * pages. We use the recently rotated / recently scanned
1588 * ratios to determine how valuable each cache is.
1589 *
1590 * Because workloads change over time (and to avoid overflow)
1591 * we keep these statistics as a floating average, which ends
1592 * up weighing recent references more than old ones.
1593 *
1594 * anon in [0], file in [1]
1595 */
6e901571 1596 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
4f98a2fe 1597 spin_lock_irq(&zone->lru_lock);
6e901571
KM
1598 reclaim_stat->recent_scanned[0] /= 2;
1599 reclaim_stat->recent_rotated[0] /= 2;
4f98a2fe
RR
1600 spin_unlock_irq(&zone->lru_lock);
1601 }
1602
6e901571 1603 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
4f98a2fe 1604 spin_lock_irq(&zone->lru_lock);
6e901571
KM
1605 reclaim_stat->recent_scanned[1] /= 2;
1606 reclaim_stat->recent_rotated[1] /= 2;
4f98a2fe
RR
1607 spin_unlock_irq(&zone->lru_lock);
1608 }
1609
1610 /*
1611 * With swappiness at 100, anonymous and file have the same priority.
1612 * This scanning priority is essentially the inverse of IO cost.
1613 */
1614 anon_prio = sc->swappiness;
1615 file_prio = 200 - sc->swappiness;
1616
1617 /*
00d8089c
RR
1618 * The amount of pressure on anon vs file pages is inversely
1619 * proportional to the fraction of recently scanned pages on
1620 * each list that were recently referenced and in active use.
4f98a2fe 1621 */
6e901571
KM
1622 ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
1623 ap /= reclaim_stat->recent_rotated[0] + 1;
4f98a2fe 1624
6e901571
KM
1625 fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
1626 fp /= reclaim_stat->recent_rotated[1] + 1;
4f98a2fe 1627
76a33fc3
SL
1628 fraction[0] = ap;
1629 fraction[1] = fp;
1630 denominator = ap + fp + 1;
1631out:
1632 for_each_evictable_lru(l) {
1633 int file = is_file_lru(l);
1634 unsigned long scan;
6e08a369 1635
76a33fc3
SL
1636 scan = zone_nr_lru_pages(zone, sc, l);
1637 if (priority || noswap) {
1638 scan >>= priority;
1639 scan = div64_u64(scan * fraction[file], denominator);
1640 }
1641 nr[l] = nr_scan_try_batch(scan,
1642 &reclaim_stat->nr_saved_scan[l]);
1643 }
6e08a369 1644}
4f98a2fe 1645
5f53e762
KM
1646static void set_lumpy_reclaim_mode(int priority, struct scan_control *sc)
1647{
1648 /*
1649 * If we need a large contiguous chunk of memory, or have
1650 * trouble getting a small set of contiguous pages, we
1651 * will reclaim both active and inactive pages.
1652 */
1653 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
1654 sc->lumpy_reclaim_mode = 1;
1655 else if (sc->order && priority < DEF_PRIORITY - 2)
1656 sc->lumpy_reclaim_mode = 1;
1657 else
1658 sc->lumpy_reclaim_mode = 0;
1659}
1660
1da177e4
LT
1661/*
1662 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1663 */
a79311c1 1664static void shrink_zone(int priority, struct zone *zone,
05ff5137 1665 struct scan_control *sc)
1da177e4 1666{
b69408e8 1667 unsigned long nr[NR_LRU_LISTS];
8695949a 1668 unsigned long nr_to_scan;
b69408e8 1669 enum lru_list l;
01dbe5c9 1670 unsigned long nr_reclaimed = sc->nr_reclaimed;
22fba335 1671 unsigned long nr_to_reclaim = sc->nr_to_reclaim;
e0f79b8f 1672
76a33fc3 1673 get_scan_count(zone, sc, nr, priority);
1da177e4 1674
5f53e762
KM
1675 set_lumpy_reclaim_mode(priority, sc);
1676
556adecb
RR
1677 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
1678 nr[LRU_INACTIVE_FILE]) {
894bc310 1679 for_each_evictable_lru(l) {
b69408e8 1680 if (nr[l]) {
ece74b2e
KM
1681 nr_to_scan = min_t(unsigned long,
1682 nr[l], SWAP_CLUSTER_MAX);
b69408e8 1683 nr[l] -= nr_to_scan;
1da177e4 1684
01dbe5c9
KM
1685 nr_reclaimed += shrink_list(l, nr_to_scan,
1686 zone, sc, priority);
b69408e8 1687 }
1da177e4 1688 }
a79311c1
RR
1689 /*
1690 * On large memory systems, scan >> priority can become
1691 * really large. This is fine for the starting priority;
1692 * we want to put equal scanning pressure on each zone.
1693 * However, if the VM has a harder time of freeing pages,
1694 * with multiple processes reclaiming pages, the total
1695 * freeing target can get unreasonably large.
1696 */
338fde90 1697 if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY)
a79311c1 1698 break;
1da177e4
LT
1699 }
1700
01dbe5c9
KM
1701 sc->nr_reclaimed = nr_reclaimed;
1702
556adecb
RR
1703 /*
1704 * Even if we did not try to evict anon pages at all, we want to
1705 * rebalance the anon lru active/inactive ratio.
1706 */
69c85481 1707 if (inactive_anon_is_low(zone, sc) && nr_swap_pages > 0)
556adecb
RR
1708 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
1709
232ea4d6 1710 throttle_vm_writeout(sc->gfp_mask);
1da177e4
LT
1711}
1712
1713/*
1714 * This is the direct reclaim path, for page-allocating processes. We only
1715 * try to reclaim pages from zones which will satisfy the caller's allocation
1716 * request.
1717 *
41858966
MG
1718 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
1719 * Because:
1da177e4
LT
1720 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1721 * allocation or
41858966
MG
1722 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
1723 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
1724 * zone defense algorithm.
1da177e4 1725 *
1da177e4
LT
1726 * If a zone is deemed to be full of pinned pages then just give it a light
1727 * scan then give up on it.
1728 */
bb21c7ce 1729static bool shrink_zones(int priority, struct zonelist *zonelist,
05ff5137 1730 struct scan_control *sc)
1da177e4 1731{
54a6eb5c 1732 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
dd1a239f 1733 struct zoneref *z;
54a6eb5c 1734 struct zone *zone;
bb21c7ce 1735 bool all_unreclaimable = true;
1cfb419b 1736
327c0e96
KH
1737 for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx,
1738 sc->nodemask) {
f3fe6512 1739 if (!populated_zone(zone))
1da177e4 1740 continue;
1cfb419b
KH
1741 /*
1742 * Take care memory controller reclaiming has small influence
1743 * to global LRU.
1744 */
e72e2bd6 1745 if (scanning_global_lru(sc)) {
1cfb419b
KH
1746 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1747 continue;
1748 note_zone_scanning_priority(zone, priority);
1da177e4 1749
93e4a89a 1750 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
1cfb419b 1751 continue; /* Let kswapd poll it */
1cfb419b
KH
1752 } else {
1753 /*
1754 * Ignore cpuset limitation here. We just want to reduce
1755 * # of used pages by us regardless of memory shortage.
1756 */
1cfb419b
KH
1757 mem_cgroup_note_reclaim_priority(sc->mem_cgroup,
1758 priority);
1759 }
408d8544 1760
a79311c1 1761 shrink_zone(priority, zone, sc);
bb21c7ce 1762 all_unreclaimable = false;
1da177e4 1763 }
bb21c7ce 1764 return all_unreclaimable;
1da177e4 1765}
4f98a2fe 1766
1da177e4
LT
1767/*
1768 * This is the main entry point to direct page reclaim.
1769 *
1770 * If a full scan of the inactive list fails to free enough memory then we
1771 * are "out of memory" and something needs to be killed.
1772 *
1773 * If the caller is !__GFP_FS then the probability of a failure is reasonably
1774 * high - the zone may be full of dirty or under-writeback pages, which this
5b0830cb
JA
1775 * caller can't do much about. We kick the writeback threads and take explicit
1776 * naps in the hope that some of these pages can be written. But if the
1777 * allocating task holds filesystem locks which prevent writeout this might not
1778 * work, and the allocation attempt will fail.
a41f24ea
NA
1779 *
1780 * returns: 0, if no pages reclaimed
1781 * else, the number of pages reclaimed
1da177e4 1782 */
dac1d27b 1783static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
dd1a239f 1784 struct scan_control *sc)
1da177e4
LT
1785{
1786 int priority;
bb21c7ce 1787 bool all_unreclaimable;
69e05944 1788 unsigned long total_scanned = 0;
1da177e4 1789 struct reclaim_state *reclaim_state = current->reclaim_state;
1da177e4 1790 unsigned long lru_pages = 0;
dd1a239f 1791 struct zoneref *z;
54a6eb5c 1792 struct zone *zone;
dd1a239f 1793 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
22fba335 1794 unsigned long writeback_threshold;
1da177e4 1795
c0ff7453 1796 get_mems_allowed();
873b4771
KK
1797 delayacct_freepages_start();
1798
e72e2bd6 1799 if (scanning_global_lru(sc))
1cfb419b
KH
1800 count_vm_event(ALLOCSTALL);
1801 /*
1802 * mem_cgroup will not do shrink_slab.
1803 */
e72e2bd6 1804 if (scanning_global_lru(sc)) {
54a6eb5c 1805 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1da177e4 1806
1cfb419b
KH
1807 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1808 continue;
1da177e4 1809
adea02a1 1810 lru_pages += zone_reclaimable_pages(zone);
1cfb419b 1811 }
1da177e4
LT
1812 }
1813
1814 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
66e1707b 1815 sc->nr_scanned = 0;
f7b7fd8f
RR
1816 if (!priority)
1817 disable_swap_token();
bb21c7ce 1818 all_unreclaimable = shrink_zones(priority, zonelist, sc);
66e1707b
BS
1819 /*
1820 * Don't shrink slabs when reclaiming memory from
1821 * over limit cgroups
1822 */
e72e2bd6 1823 if (scanning_global_lru(sc)) {
dd1a239f 1824 shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages);
91a45470 1825 if (reclaim_state) {
a79311c1 1826 sc->nr_reclaimed += reclaim_state->reclaimed_slab;
91a45470
KH
1827 reclaim_state->reclaimed_slab = 0;
1828 }
1da177e4 1829 }
66e1707b 1830 total_scanned += sc->nr_scanned;
bb21c7ce 1831 if (sc->nr_reclaimed >= sc->nr_to_reclaim)
1da177e4 1832 goto out;
1da177e4
LT
1833
1834 /*
1835 * Try to write back as many pages as we just scanned. This
1836 * tends to cause slow streaming writers to write data to the
1837 * disk smoothly, at the dirtying rate, which is nice. But
1838 * that's undesirable in laptop mode, where we *want* lumpy
1839 * writeout. So in laptop mode, write out the whole world.
1840 */
22fba335
KM
1841 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
1842 if (total_scanned > writeback_threshold) {
03ba3782 1843 wakeup_flusher_threads(laptop_mode ? 0 : total_scanned);
66e1707b 1844 sc->may_writepage = 1;
1da177e4
LT
1845 }
1846
1847 /* Take a nap, wait for some writeback to complete */
7b51755c
KM
1848 if (!sc->hibernation_mode && sc->nr_scanned &&
1849 priority < DEF_PRIORITY - 2)
8aa7e847 1850 congestion_wait(BLK_RW_ASYNC, HZ/10);
1da177e4 1851 }
bb21c7ce 1852
1da177e4 1853out:
3bb1a852
MB
1854 /*
1855 * Now that we've scanned all the zones at this priority level, note
1856 * that level within the zone so that the next thread which performs
1857 * scanning of this zone will immediately start out at this priority
1858 * level. This affects only the decision whether or not to bring
1859 * mapped pages onto the inactive list.
1860 */
1861 if (priority < 0)
1862 priority = 0;
1da177e4 1863
e72e2bd6 1864 if (scanning_global_lru(sc)) {
54a6eb5c 1865 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1cfb419b
KH
1866
1867 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1868 continue;
1869
1870 zone->prev_priority = priority;
1871 }
1872 } else
1873 mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority);
1da177e4 1874
873b4771 1875 delayacct_freepages_end();
c0ff7453 1876 put_mems_allowed();
873b4771 1877
bb21c7ce
KM
1878 if (sc->nr_reclaimed)
1879 return sc->nr_reclaimed;
1880
1881 /* top priority shrink_zones still had more to do? don't OOM, then */
1882 if (scanning_global_lru(sc) && !all_unreclaimable)
1883 return 1;
1884
1885 return 0;
1da177e4
LT
1886}
1887
dac1d27b 1888unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
327c0e96 1889 gfp_t gfp_mask, nodemask_t *nodemask)
66e1707b
BS
1890{
1891 struct scan_control sc = {
1892 .gfp_mask = gfp_mask,
1893 .may_writepage = !laptop_mode,
22fba335 1894 .nr_to_reclaim = SWAP_CLUSTER_MAX,
a6dc60f8 1895 .may_unmap = 1,
2e2e4259 1896 .may_swap = 1,
66e1707b
BS
1897 .swappiness = vm_swappiness,
1898 .order = order,
1899 .mem_cgroup = NULL,
327c0e96 1900 .nodemask = nodemask,
66e1707b
BS
1901 };
1902
dd1a239f 1903 return do_try_to_free_pages(zonelist, &sc);
66e1707b
BS
1904}
1905
00f0b825 1906#ifdef CONFIG_CGROUP_MEM_RES_CTLR
66e1707b 1907
4e416953
BS
1908unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
1909 gfp_t gfp_mask, bool noswap,
1910 unsigned int swappiness,
1911 struct zone *zone, int nid)
1912{
1913 struct scan_control sc = {
1914 .may_writepage = !laptop_mode,
1915 .may_unmap = 1,
1916 .may_swap = !noswap,
4e416953
BS
1917 .swappiness = swappiness,
1918 .order = 0,
1919 .mem_cgroup = mem,
4e416953
BS
1920 };
1921 nodemask_t nm = nodemask_of_node(nid);
1922
1923 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
1924 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
1925 sc.nodemask = &nm;
1926 sc.nr_reclaimed = 0;
1927 sc.nr_scanned = 0;
1928 /*
1929 * NOTE: Although we can get the priority field, using it
1930 * here is not a good idea, since it limits the pages we can scan.
1931 * if we don't reclaim here, the shrink_zone from balance_pgdat
1932 * will pick up pages from other mem cgroup's as well. We hack
1933 * the priority and make it zero.
1934 */
1935 shrink_zone(0, zone, &sc);
1936 return sc.nr_reclaimed;
1937}
1938
e1a1cd59 1939unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
a7885eb8
KM
1940 gfp_t gfp_mask,
1941 bool noswap,
1942 unsigned int swappiness)
66e1707b 1943{
4e416953 1944 struct zonelist *zonelist;
66e1707b 1945 struct scan_control sc = {
66e1707b 1946 .may_writepage = !laptop_mode,
a6dc60f8 1947 .may_unmap = 1,
2e2e4259 1948 .may_swap = !noswap,
22fba335 1949 .nr_to_reclaim = SWAP_CLUSTER_MAX,
a7885eb8 1950 .swappiness = swappiness,
66e1707b
BS
1951 .order = 0,
1952 .mem_cgroup = mem_cont,
327c0e96 1953 .nodemask = NULL, /* we don't care the placement */
66e1707b 1954 };
66e1707b 1955
dd1a239f
MG
1956 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
1957 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
1958 zonelist = NODE_DATA(numa_node_id())->node_zonelists;
1959 return do_try_to_free_pages(zonelist, &sc);
66e1707b
BS
1960}
1961#endif
1962
f50de2d3 1963/* is kswapd sleeping prematurely? */
bb3ab596 1964static int sleeping_prematurely(pg_data_t *pgdat, int order, long remaining)
f50de2d3 1965{
bb3ab596 1966 int i;
f50de2d3
MG
1967
1968 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
1969 if (remaining)
1970 return 1;
1971
1972 /* If after HZ/10, a zone is below the high mark, it's premature */
bb3ab596
KM
1973 for (i = 0; i < pgdat->nr_zones; i++) {
1974 struct zone *zone = pgdat->node_zones + i;
1975
1976 if (!populated_zone(zone))
1977 continue;
1978
93e4a89a 1979 if (zone->all_unreclaimable)
de3fab39
KM
1980 continue;
1981
f50de2d3
MG
1982 if (!zone_watermark_ok(zone, order, high_wmark_pages(zone),
1983 0, 0))
1984 return 1;
bb3ab596 1985 }
f50de2d3
MG
1986
1987 return 0;
1988}
1989
1da177e4
LT
1990/*
1991 * For kswapd, balance_pgdat() will work across all this node's zones until
41858966 1992 * they are all at high_wmark_pages(zone).
1da177e4 1993 *
1da177e4
LT
1994 * Returns the number of pages which were actually freed.
1995 *
1996 * There is special handling here for zones which are full of pinned pages.
1997 * This can happen if the pages are all mlocked, or if they are all used by
1998 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
1999 * What we do is to detect the case where all pages in the zone have been
2000 * scanned twice and there has been zero successful reclaim. Mark the zone as
2001 * dead and from now on, only perform a short scan. Basically we're polling
2002 * the zone for when the problem goes away.
2003 *
2004 * kswapd scans the zones in the highmem->normal->dma direction. It skips
41858966
MG
2005 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
2006 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
2007 * lower zones regardless of the number of free pages in the lower zones. This
2008 * interoperates with the page allocator fallback scheme to ensure that aging
2009 * of pages is balanced across the zones.
1da177e4 2010 */
d6277db4 2011static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
1da177e4 2012{
1da177e4
LT
2013 int all_zones_ok;
2014 int priority;
2015 int i;
69e05944 2016 unsigned long total_scanned;
1da177e4 2017 struct reclaim_state *reclaim_state = current->reclaim_state;
179e9639
AM
2018 struct scan_control sc = {
2019 .gfp_mask = GFP_KERNEL,
a6dc60f8 2020 .may_unmap = 1,
2e2e4259 2021 .may_swap = 1,
22fba335
KM
2022 /*
2023 * kswapd doesn't want to be bailed out while reclaim. because
2024 * we want to put equal scanning pressure on each zone.
2025 */
2026 .nr_to_reclaim = ULONG_MAX,
d6277db4 2027 .swappiness = vm_swappiness,
5ad333eb 2028 .order = order,
66e1707b 2029 .mem_cgroup = NULL,
179e9639 2030 };
3bb1a852
MB
2031 /*
2032 * temp_priority is used to remember the scanning priority at which
41858966
MG
2033 * this zone was successfully refilled to
2034 * free_pages == high_wmark_pages(zone).
3bb1a852
MB
2035 */
2036 int temp_priority[MAX_NR_ZONES];
1da177e4
LT
2037
2038loop_again:
2039 total_scanned = 0;
a79311c1 2040 sc.nr_reclaimed = 0;
c0bbbc73 2041 sc.may_writepage = !laptop_mode;
f8891e5e 2042 count_vm_event(PAGEOUTRUN);
1da177e4 2043
3bb1a852
MB
2044 for (i = 0; i < pgdat->nr_zones; i++)
2045 temp_priority[i] = DEF_PRIORITY;
1da177e4
LT
2046
2047 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2048 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
2049 unsigned long lru_pages = 0;
bb3ab596 2050 int has_under_min_watermark_zone = 0;
1da177e4 2051
f7b7fd8f
RR
2052 /* The swap token gets in the way of swapout... */
2053 if (!priority)
2054 disable_swap_token();
2055
1da177e4
LT
2056 all_zones_ok = 1;
2057
d6277db4
RW
2058 /*
2059 * Scan in the highmem->dma direction for the highest
2060 * zone which needs scanning
2061 */
2062 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
2063 struct zone *zone = pgdat->node_zones + i;
1da177e4 2064
d6277db4
RW
2065 if (!populated_zone(zone))
2066 continue;
1da177e4 2067
93e4a89a 2068 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
d6277db4 2069 continue;
1da177e4 2070
556adecb
RR
2071 /*
2072 * Do some background aging of the anon list, to give
2073 * pages a chance to be referenced before reclaiming.
2074 */
14797e23 2075 if (inactive_anon_is_low(zone, &sc))
556adecb
RR
2076 shrink_active_list(SWAP_CLUSTER_MAX, zone,
2077 &sc, priority, 0);
2078
41858966
MG
2079 if (!zone_watermark_ok(zone, order,
2080 high_wmark_pages(zone), 0, 0)) {
d6277db4 2081 end_zone = i;
e1dbeda6 2082 break;
1da177e4 2083 }
1da177e4 2084 }
e1dbeda6
AM
2085 if (i < 0)
2086 goto out;
2087
1da177e4
LT
2088 for (i = 0; i <= end_zone; i++) {
2089 struct zone *zone = pgdat->node_zones + i;
2090
adea02a1 2091 lru_pages += zone_reclaimable_pages(zone);
1da177e4
LT
2092 }
2093
2094 /*
2095 * Now scan the zone in the dma->highmem direction, stopping
2096 * at the last zone which needs scanning.
2097 *
2098 * We do this because the page allocator works in the opposite
2099 * direction. This prevents the page allocator from allocating
2100 * pages behind kswapd's direction of progress, which would
2101 * cause too much scanning of the lower zones.
2102 */
2103 for (i = 0; i <= end_zone; i++) {
2104 struct zone *zone = pgdat->node_zones + i;
b15e0905 2105 int nr_slab;
4e416953 2106 int nid, zid;
1da177e4 2107
f3fe6512 2108 if (!populated_zone(zone))
1da177e4
LT
2109 continue;
2110
93e4a89a 2111 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
1da177e4
LT
2112 continue;
2113
3bb1a852 2114 temp_priority[i] = priority;
1da177e4 2115 sc.nr_scanned = 0;
3bb1a852 2116 note_zone_scanning_priority(zone, priority);
4e416953
BS
2117
2118 nid = pgdat->node_id;
2119 zid = zone_idx(zone);
2120 /*
2121 * Call soft limit reclaim before calling shrink_zone.
2122 * For now we ignore the return value
2123 */
2124 mem_cgroup_soft_limit_reclaim(zone, order, sc.gfp_mask,
2125 nid, zid);
32a4330d
RR
2126 /*
2127 * We put equal pressure on every zone, unless one
2128 * zone has way too many pages free already.
2129 */
41858966
MG
2130 if (!zone_watermark_ok(zone, order,
2131 8*high_wmark_pages(zone), end_zone, 0))
a79311c1 2132 shrink_zone(priority, zone, &sc);
1da177e4 2133 reclaim_state->reclaimed_slab = 0;
b15e0905
AM
2134 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
2135 lru_pages);
a79311c1 2136 sc.nr_reclaimed += reclaim_state->reclaimed_slab;
1da177e4 2137 total_scanned += sc.nr_scanned;
93e4a89a 2138 if (zone->all_unreclaimable)
1da177e4 2139 continue;
93e4a89a
KM
2140 if (nr_slab == 0 &&
2141 zone->pages_scanned >= (zone_reclaimable_pages(zone) * 6))
2142 zone->all_unreclaimable = 1;
1da177e4
LT
2143 /*
2144 * If we've done a decent amount of scanning and
2145 * the reclaim ratio is low, start doing writepage
2146 * even in laptop mode
2147 */
2148 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
a79311c1 2149 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
1da177e4 2150 sc.may_writepage = 1;
bb3ab596 2151
45973d74
MK
2152 if (!zone_watermark_ok(zone, order,
2153 high_wmark_pages(zone), end_zone, 0)) {
2154 all_zones_ok = 0;
2155 /*
2156 * We are still under min water mark. This
2157 * means that we have a GFP_ATOMIC allocation
2158 * failure risk. Hurry up!
2159 */
2160 if (!zone_watermark_ok(zone, order,
2161 min_wmark_pages(zone), end_zone, 0))
2162 has_under_min_watermark_zone = 1;
2163 }
bb3ab596 2164
1da177e4 2165 }
1da177e4
LT
2166 if (all_zones_ok)
2167 break; /* kswapd: all done */
2168 /*
2169 * OK, kswapd is getting into trouble. Take a nap, then take
2170 * another pass across the zones.
2171 */
bb3ab596
KM
2172 if (total_scanned && (priority < DEF_PRIORITY - 2)) {
2173 if (has_under_min_watermark_zone)
2174 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT);
2175 else
2176 congestion_wait(BLK_RW_ASYNC, HZ/10);
2177 }
1da177e4
LT
2178
2179 /*
2180 * We do this so kswapd doesn't build up large priorities for
2181 * example when it is freeing in parallel with allocators. It
2182 * matches the direct reclaim path behaviour in terms of impact
2183 * on zone->*_priority.
2184 */
a79311c1 2185 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
1da177e4
LT
2186 break;
2187 }
2188out:
3bb1a852
MB
2189 /*
2190 * Note within each zone the priority level at which this zone was
2191 * brought into a happy state. So that the next thread which scans this
2192 * zone will start out at that priority level.
2193 */
1da177e4
LT
2194 for (i = 0; i < pgdat->nr_zones; i++) {
2195 struct zone *zone = pgdat->node_zones + i;
2196
3bb1a852 2197 zone->prev_priority = temp_priority[i];
1da177e4
LT
2198 }
2199 if (!all_zones_ok) {
2200 cond_resched();
8357376d
RW
2201
2202 try_to_freeze();
2203
73ce02e9
KM
2204 /*
2205 * Fragmentation may mean that the system cannot be
2206 * rebalanced for high-order allocations in all zones.
2207 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
2208 * it means the zones have been fully scanned and are still
2209 * not balanced. For high-order allocations, there is
2210 * little point trying all over again as kswapd may
2211 * infinite loop.
2212 *
2213 * Instead, recheck all watermarks at order-0 as they
2214 * are the most important. If watermarks are ok, kswapd will go
2215 * back to sleep. High-order users can still perform direct
2216 * reclaim if they wish.
2217 */
2218 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX)
2219 order = sc.order = 0;
2220
1da177e4
LT
2221 goto loop_again;
2222 }
2223
a79311c1 2224 return sc.nr_reclaimed;
1da177e4
LT
2225}
2226
2227/*
2228 * The background pageout daemon, started as a kernel thread
4f98a2fe 2229 * from the init process.
1da177e4
LT
2230 *
2231 * This basically trickles out pages so that we have _some_
2232 * free memory available even if there is no other activity
2233 * that frees anything up. This is needed for things like routing
2234 * etc, where we otherwise might have all activity going on in
2235 * asynchronous contexts that cannot page things out.
2236 *
2237 * If there are applications that are active memory-allocators
2238 * (most normal use), this basically shouldn't matter.
2239 */
2240static int kswapd(void *p)
2241{
2242 unsigned long order;
2243 pg_data_t *pgdat = (pg_data_t*)p;
2244 struct task_struct *tsk = current;
2245 DEFINE_WAIT(wait);
2246 struct reclaim_state reclaim_state = {
2247 .reclaimed_slab = 0,
2248 };
a70f7302 2249 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
1da177e4 2250
cf40bd16
NP
2251 lockdep_set_current_reclaim_state(GFP_KERNEL);
2252
174596a0 2253 if (!cpumask_empty(cpumask))
c5f59f08 2254 set_cpus_allowed_ptr(tsk, cpumask);
1da177e4
LT
2255 current->reclaim_state = &reclaim_state;
2256
2257 /*
2258 * Tell the memory management that we're a "memory allocator",
2259 * and that if we need more memory we should get access to it
2260 * regardless (see "__alloc_pages()"). "kswapd" should
2261 * never get caught in the normal page freeing logic.
2262 *
2263 * (Kswapd normally doesn't need memory anyway, but sometimes
2264 * you need a small amount of memory in order to be able to
2265 * page out something else, and this flag essentially protects
2266 * us from recursively trying to free more memory as we're
2267 * trying to free the first piece of memory in the first place).
2268 */
930d9152 2269 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
83144186 2270 set_freezable();
1da177e4
LT
2271
2272 order = 0;
2273 for ( ; ; ) {
2274 unsigned long new_order;
8fe23e05 2275 int ret;
3e1d1d28 2276
1da177e4
LT
2277 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2278 new_order = pgdat->kswapd_max_order;
2279 pgdat->kswapd_max_order = 0;
2280 if (order < new_order) {
2281 /*
2282 * Don't sleep if someone wants a larger 'order'
2283 * allocation
2284 */
2285 order = new_order;
2286 } else {
f50de2d3
MG
2287 if (!freezing(current) && !kthread_should_stop()) {
2288 long remaining = 0;
2289
2290 /* Try to sleep for a short interval */
bb3ab596 2291 if (!sleeping_prematurely(pgdat, order, remaining)) {
f50de2d3
MG
2292 remaining = schedule_timeout(HZ/10);
2293 finish_wait(&pgdat->kswapd_wait, &wait);
2294 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2295 }
2296
2297 /*
2298 * After a short sleep, check if it was a
2299 * premature sleep. If not, then go fully
2300 * to sleep until explicitly woken up
2301 */
bb3ab596 2302 if (!sleeping_prematurely(pgdat, order, remaining))
f50de2d3
MG
2303 schedule();
2304 else {
2305 if (remaining)
bb3ab596 2306 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
f50de2d3 2307 else
bb3ab596 2308 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
f50de2d3
MG
2309 }
2310 }
b1296cc4 2311
1da177e4
LT
2312 order = pgdat->kswapd_max_order;
2313 }
2314 finish_wait(&pgdat->kswapd_wait, &wait);
2315
8fe23e05
DR
2316 ret = try_to_freeze();
2317 if (kthread_should_stop())
2318 break;
2319
2320 /*
2321 * We can speed up thawing tasks if we don't call balance_pgdat
2322 * after returning from the refrigerator
2323 */
2324 if (!ret)
b1296cc4 2325 balance_pgdat(pgdat, order);
1da177e4
LT
2326 }
2327 return 0;
2328}
2329
2330/*
2331 * A zone is low on free memory, so wake its kswapd task to service it.
2332 */
2333void wakeup_kswapd(struct zone *zone, int order)
2334{
2335 pg_data_t *pgdat;
2336
f3fe6512 2337 if (!populated_zone(zone))
1da177e4
LT
2338 return;
2339
2340 pgdat = zone->zone_pgdat;
41858966 2341 if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0, 0))
1da177e4
LT
2342 return;
2343 if (pgdat->kswapd_max_order < order)
2344 pgdat->kswapd_max_order = order;
02a0e53d 2345 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1da177e4 2346 return;
8d0986e2 2347 if (!waitqueue_active(&pgdat->kswapd_wait))
1da177e4 2348 return;
8d0986e2 2349 wake_up_interruptible(&pgdat->kswapd_wait);
1da177e4
LT
2350}
2351
adea02a1
WF
2352/*
2353 * The reclaimable count would be mostly accurate.
2354 * The less reclaimable pages may be
2355 * - mlocked pages, which will be moved to unevictable list when encountered
2356 * - mapped pages, which may require several travels to be reclaimed
2357 * - dirty pages, which is not "instantly" reclaimable
2358 */
2359unsigned long global_reclaimable_pages(void)
4f98a2fe 2360{
adea02a1
WF
2361 int nr;
2362
2363 nr = global_page_state(NR_ACTIVE_FILE) +
2364 global_page_state(NR_INACTIVE_FILE);
2365
2366 if (nr_swap_pages > 0)
2367 nr += global_page_state(NR_ACTIVE_ANON) +
2368 global_page_state(NR_INACTIVE_ANON);
2369
2370 return nr;
2371}
2372
2373unsigned long zone_reclaimable_pages(struct zone *zone)
2374{
2375 int nr;
2376
2377 nr = zone_page_state(zone, NR_ACTIVE_FILE) +
2378 zone_page_state(zone, NR_INACTIVE_FILE);
2379
2380 if (nr_swap_pages > 0)
2381 nr += zone_page_state(zone, NR_ACTIVE_ANON) +
2382 zone_page_state(zone, NR_INACTIVE_ANON);
2383
2384 return nr;
4f98a2fe
RR
2385}
2386
c6f37f12 2387#ifdef CONFIG_HIBERNATION
1da177e4 2388/*
7b51755c 2389 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
d6277db4
RW
2390 * freed pages.
2391 *
2392 * Rather than trying to age LRUs the aim is to preserve the overall
2393 * LRU order by reclaiming preferentially
2394 * inactive > active > active referenced > active mapped
1da177e4 2395 */
7b51755c 2396unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
1da177e4 2397{
d6277db4 2398 struct reclaim_state reclaim_state;
d6277db4 2399 struct scan_control sc = {
7b51755c
KM
2400 .gfp_mask = GFP_HIGHUSER_MOVABLE,
2401 .may_swap = 1,
2402 .may_unmap = 1,
d6277db4 2403 .may_writepage = 1,
7b51755c
KM
2404 .nr_to_reclaim = nr_to_reclaim,
2405 .hibernation_mode = 1,
2406 .swappiness = vm_swappiness,
2407 .order = 0,
1da177e4 2408 };
7b51755c
KM
2409 struct zonelist * zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
2410 struct task_struct *p = current;
2411 unsigned long nr_reclaimed;
1da177e4 2412
7b51755c
KM
2413 p->flags |= PF_MEMALLOC;
2414 lockdep_set_current_reclaim_state(sc.gfp_mask);
2415 reclaim_state.reclaimed_slab = 0;
2416 p->reclaim_state = &reclaim_state;
d6277db4 2417
7b51755c 2418 nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
d979677c 2419
7b51755c
KM
2420 p->reclaim_state = NULL;
2421 lockdep_clear_current_reclaim_state();
2422 p->flags &= ~PF_MEMALLOC;
d6277db4 2423
7b51755c 2424 return nr_reclaimed;
1da177e4 2425}
c6f37f12 2426#endif /* CONFIG_HIBERNATION */
1da177e4 2427
1da177e4
LT
2428/* It's optimal to keep kswapds on the same CPUs as their memory, but
2429 not required for correctness. So if the last cpu in a node goes
2430 away, we get changed to run anywhere: as the first one comes back,
2431 restore their cpu bindings. */
9c7b216d 2432static int __devinit cpu_callback(struct notifier_block *nfb,
69e05944 2433 unsigned long action, void *hcpu)
1da177e4 2434{
58c0a4a7 2435 int nid;
1da177e4 2436
8bb78442 2437 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
58c0a4a7 2438 for_each_node_state(nid, N_HIGH_MEMORY) {
c5f59f08 2439 pg_data_t *pgdat = NODE_DATA(nid);
a70f7302
RR
2440 const struct cpumask *mask;
2441
2442 mask = cpumask_of_node(pgdat->node_id);
c5f59f08 2443
3e597945 2444 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
1da177e4 2445 /* One of our CPUs online: restore mask */
c5f59f08 2446 set_cpus_allowed_ptr(pgdat->kswapd, mask);
1da177e4
LT
2447 }
2448 }
2449 return NOTIFY_OK;
2450}
1da177e4 2451
3218ae14
YG
2452/*
2453 * This kswapd start function will be called by init and node-hot-add.
2454 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2455 */
2456int kswapd_run(int nid)
2457{
2458 pg_data_t *pgdat = NODE_DATA(nid);
2459 int ret = 0;
2460
2461 if (pgdat->kswapd)
2462 return 0;
2463
2464 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
2465 if (IS_ERR(pgdat->kswapd)) {
2466 /* failure at boot is fatal */
2467 BUG_ON(system_state == SYSTEM_BOOTING);
2468 printk("Failed to start kswapd on node %d\n",nid);
2469 ret = -1;
2470 }
2471 return ret;
2472}
2473
8fe23e05
DR
2474/*
2475 * Called by memory hotplug when all memory in a node is offlined.
2476 */
2477void kswapd_stop(int nid)
2478{
2479 struct task_struct *kswapd = NODE_DATA(nid)->kswapd;
2480
2481 if (kswapd)
2482 kthread_stop(kswapd);
2483}
2484
1da177e4
LT
2485static int __init kswapd_init(void)
2486{
3218ae14 2487 int nid;
69e05944 2488
1da177e4 2489 swap_setup();
9422ffba 2490 for_each_node_state(nid, N_HIGH_MEMORY)
3218ae14 2491 kswapd_run(nid);
1da177e4
LT
2492 hotcpu_notifier(cpu_callback, 0);
2493 return 0;
2494}
2495
2496module_init(kswapd_init)
9eeff239
CL
2497
2498#ifdef CONFIG_NUMA
2499/*
2500 * Zone reclaim mode
2501 *
2502 * If non-zero call zone_reclaim when the number of free pages falls below
2503 * the watermarks.
9eeff239
CL
2504 */
2505int zone_reclaim_mode __read_mostly;
2506
1b2ffb78 2507#define RECLAIM_OFF 0
7d03431c 2508#define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
1b2ffb78
CL
2509#define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
2510#define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
2511
a92f7126
CL
2512/*
2513 * Priority for ZONE_RECLAIM. This determines the fraction of pages
2514 * of a node considered for each zone_reclaim. 4 scans 1/16th of
2515 * a zone.
2516 */
2517#define ZONE_RECLAIM_PRIORITY 4
2518
9614634f
CL
2519/*
2520 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
2521 * occur.
2522 */
2523int sysctl_min_unmapped_ratio = 1;
2524
0ff38490
CL
2525/*
2526 * If the number of slab pages in a zone grows beyond this percentage then
2527 * slab reclaim needs to occur.
2528 */
2529int sysctl_min_slab_ratio = 5;
2530
90afa5de
MG
2531static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
2532{
2533 unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
2534 unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
2535 zone_page_state(zone, NR_ACTIVE_FILE);
2536
2537 /*
2538 * It's possible for there to be more file mapped pages than
2539 * accounted for by the pages on the file LRU lists because
2540 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
2541 */
2542 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
2543}
2544
2545/* Work out how many page cache pages we can reclaim in this reclaim_mode */
2546static long zone_pagecache_reclaimable(struct zone *zone)
2547{
2548 long nr_pagecache_reclaimable;
2549 long delta = 0;
2550
2551 /*
2552 * If RECLAIM_SWAP is set, then all file pages are considered
2553 * potentially reclaimable. Otherwise, we have to worry about
2554 * pages like swapcache and zone_unmapped_file_pages() provides
2555 * a better estimate
2556 */
2557 if (zone_reclaim_mode & RECLAIM_SWAP)
2558 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
2559 else
2560 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
2561
2562 /* If we can't clean pages, remove dirty pages from consideration */
2563 if (!(zone_reclaim_mode & RECLAIM_WRITE))
2564 delta += zone_page_state(zone, NR_FILE_DIRTY);
2565
2566 /* Watch for any possible underflows due to delta */
2567 if (unlikely(delta > nr_pagecache_reclaimable))
2568 delta = nr_pagecache_reclaimable;
2569
2570 return nr_pagecache_reclaimable - delta;
2571}
2572
9eeff239
CL
2573/*
2574 * Try to free up some pages from this zone through reclaim.
2575 */
179e9639 2576static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
9eeff239 2577{
7fb2d46d 2578 /* Minimum pages needed in order to stay on node */
69e05944 2579 const unsigned long nr_pages = 1 << order;
9eeff239
CL
2580 struct task_struct *p = current;
2581 struct reclaim_state reclaim_state;
8695949a 2582 int priority;
179e9639
AM
2583 struct scan_control sc = {
2584 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
a6dc60f8 2585 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
2e2e4259 2586 .may_swap = 1,
22fba335
KM
2587 .nr_to_reclaim = max_t(unsigned long, nr_pages,
2588 SWAP_CLUSTER_MAX),
179e9639 2589 .gfp_mask = gfp_mask,
d6277db4 2590 .swappiness = vm_swappiness,
bd2f6199 2591 .order = order,
179e9639 2592 };
83e33a47 2593 unsigned long slab_reclaimable;
9eeff239
CL
2594
2595 disable_swap_token();
9eeff239 2596 cond_resched();
d4f7796e
CL
2597 /*
2598 * We need to be able to allocate from the reserves for RECLAIM_SWAP
2599 * and we also need to be able to write out pages for RECLAIM_WRITE
2600 * and RECLAIM_SWAP.
2601 */
2602 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
76ca542d 2603 lockdep_set_current_reclaim_state(gfp_mask);
9eeff239
CL
2604 reclaim_state.reclaimed_slab = 0;
2605 p->reclaim_state = &reclaim_state;
c84db23c 2606
90afa5de 2607 if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
0ff38490
CL
2608 /*
2609 * Free memory by calling shrink zone with increasing
2610 * priorities until we have enough memory freed.
2611 */
2612 priority = ZONE_RECLAIM_PRIORITY;
2613 do {
3bb1a852 2614 note_zone_scanning_priority(zone, priority);
a79311c1 2615 shrink_zone(priority, zone, &sc);
0ff38490 2616 priority--;
a79311c1 2617 } while (priority >= 0 && sc.nr_reclaimed < nr_pages);
0ff38490 2618 }
c84db23c 2619
83e33a47
CL
2620 slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2621 if (slab_reclaimable > zone->min_slab_pages) {
2a16e3f4 2622 /*
7fb2d46d 2623 * shrink_slab() does not currently allow us to determine how
0ff38490
CL
2624 * many pages were freed in this zone. So we take the current
2625 * number of slab pages and shake the slab until it is reduced
2626 * by the same nr_pages that we used for reclaiming unmapped
2627 * pages.
2a16e3f4 2628 *
0ff38490
CL
2629 * Note that shrink_slab will free memory on all zones and may
2630 * take a long time.
2a16e3f4 2631 */
0ff38490 2632 while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
83e33a47
CL
2633 zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
2634 slab_reclaimable - nr_pages)
0ff38490 2635 ;
83e33a47
CL
2636
2637 /*
2638 * Update nr_reclaimed by the number of slab pages we
2639 * reclaimed from this zone.
2640 */
a79311c1 2641 sc.nr_reclaimed += slab_reclaimable -
83e33a47 2642 zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2a16e3f4
CL
2643 }
2644
9eeff239 2645 p->reclaim_state = NULL;
d4f7796e 2646 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
76ca542d 2647 lockdep_clear_current_reclaim_state();
a79311c1 2648 return sc.nr_reclaimed >= nr_pages;
9eeff239 2649}
179e9639
AM
2650
2651int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2652{
179e9639 2653 int node_id;
d773ed6b 2654 int ret;
179e9639
AM
2655
2656 /*
0ff38490
CL
2657 * Zone reclaim reclaims unmapped file backed pages and
2658 * slab pages if we are over the defined limits.
34aa1330 2659 *
9614634f
CL
2660 * A small portion of unmapped file backed pages is needed for
2661 * file I/O otherwise pages read by file I/O will be immediately
2662 * thrown out if the zone is overallocated. So we do not reclaim
2663 * if less than a specified percentage of the zone is used by
2664 * unmapped file backed pages.
179e9639 2665 */
90afa5de
MG
2666 if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
2667 zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
fa5e084e 2668 return ZONE_RECLAIM_FULL;
179e9639 2669
93e4a89a 2670 if (zone->all_unreclaimable)
fa5e084e 2671 return ZONE_RECLAIM_FULL;
d773ed6b 2672
179e9639 2673 /*
d773ed6b 2674 * Do not scan if the allocation should not be delayed.
179e9639 2675 */
d773ed6b 2676 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
fa5e084e 2677 return ZONE_RECLAIM_NOSCAN;
179e9639
AM
2678
2679 /*
2680 * Only run zone reclaim on the local zone or on zones that do not
2681 * have associated processors. This will favor the local processor
2682 * over remote processors and spread off node memory allocations
2683 * as wide as possible.
2684 */
89fa3024 2685 node_id = zone_to_nid(zone);
37c0708d 2686 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
fa5e084e 2687 return ZONE_RECLAIM_NOSCAN;
d773ed6b
DR
2688
2689 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
fa5e084e
MG
2690 return ZONE_RECLAIM_NOSCAN;
2691
d773ed6b
DR
2692 ret = __zone_reclaim(zone, gfp_mask, order);
2693 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
2694
24cf7251
MG
2695 if (!ret)
2696 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
2697
d773ed6b 2698 return ret;
179e9639 2699}
9eeff239 2700#endif
894bc310 2701
894bc310
LS
2702/*
2703 * page_evictable - test whether a page is evictable
2704 * @page: the page to test
2705 * @vma: the VMA in which the page is or will be mapped, may be NULL
2706 *
2707 * Test whether page is evictable--i.e., should be placed on active/inactive
b291f000
NP
2708 * lists vs unevictable list. The vma argument is !NULL when called from the
2709 * fault path to determine how to instantate a new page.
894bc310
LS
2710 *
2711 * Reasons page might not be evictable:
ba9ddf49 2712 * (1) page's mapping marked unevictable
b291f000 2713 * (2) page is part of an mlocked VMA
ba9ddf49 2714 *
894bc310
LS
2715 */
2716int page_evictable(struct page *page, struct vm_area_struct *vma)
2717{
2718
ba9ddf49
LS
2719 if (mapping_unevictable(page_mapping(page)))
2720 return 0;
2721
b291f000
NP
2722 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
2723 return 0;
894bc310
LS
2724
2725 return 1;
2726}
89e004ea
LS
2727
2728/**
2729 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
2730 * @page: page to check evictability and move to appropriate lru list
2731 * @zone: zone page is in
2732 *
2733 * Checks a page for evictability and moves the page to the appropriate
2734 * zone lru list.
2735 *
2736 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
2737 * have PageUnevictable set.
2738 */
2739static void check_move_unevictable_page(struct page *page, struct zone *zone)
2740{
2741 VM_BUG_ON(PageActive(page));
2742
2743retry:
2744 ClearPageUnevictable(page);
2745 if (page_evictable(page, NULL)) {
401a8e1c 2746 enum lru_list l = page_lru_base_type(page);
af936a16 2747
89e004ea
LS
2748 __dec_zone_state(zone, NR_UNEVICTABLE);
2749 list_move(&page->lru, &zone->lru[l].list);
08e552c6 2750 mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l);
89e004ea
LS
2751 __inc_zone_state(zone, NR_INACTIVE_ANON + l);
2752 __count_vm_event(UNEVICTABLE_PGRESCUED);
2753 } else {
2754 /*
2755 * rotate unevictable list
2756 */
2757 SetPageUnevictable(page);
2758 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
08e552c6 2759 mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE);
89e004ea
LS
2760 if (page_evictable(page, NULL))
2761 goto retry;
2762 }
2763}
2764
2765/**
2766 * scan_mapping_unevictable_pages - scan an address space for evictable pages
2767 * @mapping: struct address_space to scan for evictable pages
2768 *
2769 * Scan all pages in mapping. Check unevictable pages for
2770 * evictability and move them to the appropriate zone lru list.
2771 */
2772void scan_mapping_unevictable_pages(struct address_space *mapping)
2773{
2774 pgoff_t next = 0;
2775 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >>
2776 PAGE_CACHE_SHIFT;
2777 struct zone *zone;
2778 struct pagevec pvec;
2779
2780 if (mapping->nrpages == 0)
2781 return;
2782
2783 pagevec_init(&pvec, 0);
2784 while (next < end &&
2785 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
2786 int i;
2787 int pg_scanned = 0;
2788
2789 zone = NULL;
2790
2791 for (i = 0; i < pagevec_count(&pvec); i++) {
2792 struct page *page = pvec.pages[i];
2793 pgoff_t page_index = page->index;
2794 struct zone *pagezone = page_zone(page);
2795
2796 pg_scanned++;
2797 if (page_index > next)
2798 next = page_index;
2799 next++;
2800
2801 if (pagezone != zone) {
2802 if (zone)
2803 spin_unlock_irq(&zone->lru_lock);
2804 zone = pagezone;
2805 spin_lock_irq(&zone->lru_lock);
2806 }
2807
2808 if (PageLRU(page) && PageUnevictable(page))
2809 check_move_unevictable_page(page, zone);
2810 }
2811 if (zone)
2812 spin_unlock_irq(&zone->lru_lock);
2813 pagevec_release(&pvec);
2814
2815 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
2816 }
2817
2818}
af936a16
LS
2819
2820/**
2821 * scan_zone_unevictable_pages - check unevictable list for evictable pages
2822 * @zone - zone of which to scan the unevictable list
2823 *
2824 * Scan @zone's unevictable LRU lists to check for pages that have become
2825 * evictable. Move those that have to @zone's inactive list where they
2826 * become candidates for reclaim, unless shrink_inactive_zone() decides
2827 * to reactivate them. Pages that are still unevictable are rotated
2828 * back onto @zone's unevictable list.
2829 */
2830#define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
14b90b22 2831static void scan_zone_unevictable_pages(struct zone *zone)
af936a16
LS
2832{
2833 struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list;
2834 unsigned long scan;
2835 unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE);
2836
2837 while (nr_to_scan > 0) {
2838 unsigned long batch_size = min(nr_to_scan,
2839 SCAN_UNEVICTABLE_BATCH_SIZE);
2840
2841 spin_lock_irq(&zone->lru_lock);
2842 for (scan = 0; scan < batch_size; scan++) {
2843 struct page *page = lru_to_page(l_unevictable);
2844
2845 if (!trylock_page(page))
2846 continue;
2847
2848 prefetchw_prev_lru_page(page, l_unevictable, flags);
2849
2850 if (likely(PageLRU(page) && PageUnevictable(page)))
2851 check_move_unevictable_page(page, zone);
2852
2853 unlock_page(page);
2854 }
2855 spin_unlock_irq(&zone->lru_lock);
2856
2857 nr_to_scan -= batch_size;
2858 }
2859}
2860
2861
2862/**
2863 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
2864 *
2865 * A really big hammer: scan all zones' unevictable LRU lists to check for
2866 * pages that have become evictable. Move those back to the zones'
2867 * inactive list where they become candidates for reclaim.
2868 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
2869 * and we add swap to the system. As such, it runs in the context of a task
2870 * that has possibly/probably made some previously unevictable pages
2871 * evictable.
2872 */
ff30153b 2873static void scan_all_zones_unevictable_pages(void)
af936a16
LS
2874{
2875 struct zone *zone;
2876
2877 for_each_zone(zone) {
2878 scan_zone_unevictable_pages(zone);
2879 }
2880}
2881
2882/*
2883 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
2884 * all nodes' unevictable lists for evictable pages
2885 */
2886unsigned long scan_unevictable_pages;
2887
2888int scan_unevictable_handler(struct ctl_table *table, int write,
8d65af78 2889 void __user *buffer,
af936a16
LS
2890 size_t *length, loff_t *ppos)
2891{
8d65af78 2892 proc_doulongvec_minmax(table, write, buffer, length, ppos);
af936a16
LS
2893
2894 if (write && *(unsigned long *)table->data)
2895 scan_all_zones_unevictable_pages();
2896
2897 scan_unevictable_pages = 0;
2898 return 0;
2899}
2900
2901/*
2902 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
2903 * a specified node's per zone unevictable lists for evictable pages.
2904 */
2905
2906static ssize_t read_scan_unevictable_node(struct sys_device *dev,
2907 struct sysdev_attribute *attr,
2908 char *buf)
2909{
2910 return sprintf(buf, "0\n"); /* always zero; should fit... */
2911}
2912
2913static ssize_t write_scan_unevictable_node(struct sys_device *dev,
2914 struct sysdev_attribute *attr,
2915 const char *buf, size_t count)
2916{
2917 struct zone *node_zones = NODE_DATA(dev->id)->node_zones;
2918 struct zone *zone;
2919 unsigned long res;
2920 unsigned long req = strict_strtoul(buf, 10, &res);
2921
2922 if (!req)
2923 return 1; /* zero is no-op */
2924
2925 for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
2926 if (!populated_zone(zone))
2927 continue;
2928 scan_zone_unevictable_pages(zone);
2929 }
2930 return 1;
2931}
2932
2933
2934static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
2935 read_scan_unevictable_node,
2936 write_scan_unevictable_node);
2937
2938int scan_unevictable_register_node(struct node *node)
2939{
2940 return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages);
2941}
2942
2943void scan_unevictable_unregister_node(struct node *node)
2944{
2945 sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages);
2946}
2947