b0cd81c32de6ca0f601bb1be3c12764beb37a8af
[linux-3.10.git] / mm / vmscan.c
1 /*
2  *  linux/mm/vmscan.c
3  *
4  *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
5  *
6  *  Swap reorganised 29.12.95, Stephen Tweedie.
7  *  kswapd added: 7.1.96  sct
8  *  Removed kswapd_ctl limits, and swap out as many pages as needed
9  *  to bring the system back to freepages.high: 2.4.97, Rik van Riel.
10  *  Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
11  *  Multiqueue VM started 5.8.00, Rik van Riel.
12  */
13
14 #include <linux/mm.h>
15 #include <linux/module.h>
16 #include <linux/slab.h>
17 #include <linux/kernel_stat.h>
18 #include <linux/swap.h>
19 #include <linux/pagemap.h>
20 #include <linux/init.h>
21 #include <linux/highmem.h>
22 #include <linux/file.h>
23 #include <linux/writeback.h>
24 #include <linux/blkdev.h>
25 #include <linux/buffer_head.h>  /* for try_to_release_page(),
26                                         buffer_heads_over_limit */
27 #include <linux/mm_inline.h>
28 #include <linux/pagevec.h>
29 #include <linux/backing-dev.h>
30 #include <linux/rmap.h>
31 #include <linux/topology.h>
32 #include <linux/cpu.h>
33 #include <linux/cpuset.h>
34 #include <linux/notifier.h>
35 #include <linux/rwsem.h>
36
37 #include <asm/tlbflush.h>
38 #include <asm/div64.h>
39
40 #include <linux/swapops.h>
41
42 /* possible outcome of pageout() */
43 typedef enum {
44         /* failed to write page out, page is locked */
45         PAGE_KEEP,
46         /* move page to the active list, page is locked */
47         PAGE_ACTIVATE,
48         /* page has been sent to the disk successfully, page is unlocked */
49         PAGE_SUCCESS,
50         /* page is clean and locked */
51         PAGE_CLEAN,
52 } pageout_t;
53
54 struct scan_control {
55         /* Ask refill_inactive_zone, or shrink_cache to scan this many pages */
56         unsigned long nr_to_scan;
57
58         /* Incremented by the number of inactive pages that were scanned */
59         unsigned long nr_scanned;
60
61         /* Incremented by the number of pages reclaimed */
62         unsigned long nr_reclaimed;
63
64         unsigned long nr_mapped;        /* From page_state */
65
66         /* How many pages shrink_cache() should reclaim */
67         int nr_to_reclaim;
68
69         /* Ask shrink_caches, or shrink_zone to scan at this priority */
70         unsigned int priority;
71
72         /* This context's GFP mask */
73         gfp_t gfp_mask;
74
75         int may_writepage;
76
77         /* Can pages be swapped as part of reclaim? */
78         int may_swap;
79
80         /* This context's SWAP_CLUSTER_MAX. If freeing memory for
81          * suspend, we effectively ignore SWAP_CLUSTER_MAX.
82          * In this context, it doesn't matter that we scan the
83          * whole list at once. */
84         int swap_cluster_max;
85 };
86
87 /*
88  * The list of shrinker callbacks used by to apply pressure to
89  * ageable caches.
90  */
91 struct shrinker {
92         shrinker_t              shrinker;
93         struct list_head        list;
94         int                     seeks;  /* seeks to recreate an obj */
95         long                    nr;     /* objs pending delete */
96 };
97
98 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
99
100 #ifdef ARCH_HAS_PREFETCH
101 #define prefetch_prev_lru_page(_page, _base, _field)                    \
102         do {                                                            \
103                 if ((_page)->lru.prev != _base) {                       \
104                         struct page *prev;                              \
105                                                                         \
106                         prev = lru_to_page(&(_page->lru));              \
107                         prefetch(&prev->_field);                        \
108                 }                                                       \
109         } while (0)
110 #else
111 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
112 #endif
113
114 #ifdef ARCH_HAS_PREFETCHW
115 #define prefetchw_prev_lru_page(_page, _base, _field)                   \
116         do {                                                            \
117                 if ((_page)->lru.prev != _base) {                       \
118                         struct page *prev;                              \
119                                                                         \
120                         prev = lru_to_page(&(_page->lru));              \
121                         prefetchw(&prev->_field);                       \
122                 }                                                       \
123         } while (0)
124 #else
125 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
126 #endif
127
128 /*
129  * From 0 .. 100.  Higher means more swappy.
130  */
131 int vm_swappiness = 60;
132 static long total_memory;
133
134 static LIST_HEAD(shrinker_list);
135 static DECLARE_RWSEM(shrinker_rwsem);
136
137 /*
138  * Add a shrinker callback to be called from the vm
139  */
140 struct shrinker *set_shrinker(int seeks, shrinker_t theshrinker)
141 {
142         struct shrinker *shrinker;
143
144         shrinker = kmalloc(sizeof(*shrinker), GFP_KERNEL);
145         if (shrinker) {
146                 shrinker->shrinker = theshrinker;
147                 shrinker->seeks = seeks;
148                 shrinker->nr = 0;
149                 down_write(&shrinker_rwsem);
150                 list_add_tail(&shrinker->list, &shrinker_list);
151                 up_write(&shrinker_rwsem);
152         }
153         return shrinker;
154 }
155 EXPORT_SYMBOL(set_shrinker);
156
157 /*
158  * Remove one
159  */
160 void remove_shrinker(struct shrinker *shrinker)
161 {
162         down_write(&shrinker_rwsem);
163         list_del(&shrinker->list);
164         up_write(&shrinker_rwsem);
165         kfree(shrinker);
166 }
167 EXPORT_SYMBOL(remove_shrinker);
168
169 #define SHRINK_BATCH 128
170 /*
171  * Call the shrink functions to age shrinkable caches
172  *
173  * Here we assume it costs one seek to replace a lru page and that it also
174  * takes a seek to recreate a cache object.  With this in mind we age equal
175  * percentages of the lru and ageable caches.  This should balance the seeks
176  * generated by these structures.
177  *
178  * If the vm encounted mapped pages on the LRU it increase the pressure on
179  * slab to avoid swapping.
180  *
181  * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
182  *
183  * `lru_pages' represents the number of on-LRU pages in all the zones which
184  * are eligible for the caller's allocation attempt.  It is used for balancing
185  * slab reclaim versus page reclaim.
186  *
187  * Returns the number of slab objects which we shrunk.
188  */
189 static int shrink_slab(unsigned long scanned, gfp_t gfp_mask,
190                         unsigned long lru_pages)
191 {
192         struct shrinker *shrinker;
193         int ret = 0;
194
195         if (scanned == 0)
196                 scanned = SWAP_CLUSTER_MAX;
197
198         if (!down_read_trylock(&shrinker_rwsem))
199                 return 1;       /* Assume we'll be able to shrink next time */
200
201         list_for_each_entry(shrinker, &shrinker_list, list) {
202                 unsigned long long delta;
203                 unsigned long total_scan;
204                 unsigned long max_pass = (*shrinker->shrinker)(0, gfp_mask);
205
206                 delta = (4 * scanned) / shrinker->seeks;
207                 delta *= max_pass;
208                 do_div(delta, lru_pages + 1);
209                 shrinker->nr += delta;
210                 if (shrinker->nr < 0) {
211                         printk(KERN_ERR "%s: nr=%ld\n",
212                                         __FUNCTION__, shrinker->nr);
213                         shrinker->nr = max_pass;
214                 }
215
216                 /*
217                  * Avoid risking looping forever due to too large nr value:
218                  * never try to free more than twice the estimate number of
219                  * freeable entries.
220                  */
221                 if (shrinker->nr > max_pass * 2)
222                         shrinker->nr = max_pass * 2;
223
224                 total_scan = shrinker->nr;
225                 shrinker->nr = 0;
226
227                 while (total_scan >= SHRINK_BATCH) {
228                         long this_scan = SHRINK_BATCH;
229                         int shrink_ret;
230                         int nr_before;
231
232                         nr_before = (*shrinker->shrinker)(0, gfp_mask);
233                         shrink_ret = (*shrinker->shrinker)(this_scan, gfp_mask);
234                         if (shrink_ret == -1)
235                                 break;
236                         if (shrink_ret < nr_before)
237                                 ret += nr_before - shrink_ret;
238                         mod_page_state(slabs_scanned, this_scan);
239                         total_scan -= this_scan;
240
241                         cond_resched();
242                 }
243
244                 shrinker->nr += total_scan;
245         }
246         up_read(&shrinker_rwsem);
247         return ret;
248 }
249
250 /* Called without lock on whether page is mapped, so answer is unstable */
251 static inline int page_mapping_inuse(struct page *page)
252 {
253         struct address_space *mapping;
254
255         /* Page is in somebody's page tables. */
256         if (page_mapped(page))
257                 return 1;
258
259         /* Be more reluctant to reclaim swapcache than pagecache */
260         if (PageSwapCache(page))
261                 return 1;
262
263         mapping = page_mapping(page);
264         if (!mapping)
265                 return 0;
266
267         /* File is mmap'd by somebody? */
268         return mapping_mapped(mapping);
269 }
270
271 static inline int is_page_cache_freeable(struct page *page)
272 {
273         return page_count(page) - !!PagePrivate(page) == 2;
274 }
275
276 static int may_write_to_queue(struct backing_dev_info *bdi)
277 {
278         if (current_is_kswapd())
279                 return 1;
280         if (current_is_pdflush())       /* This is unlikely, but why not... */
281                 return 1;
282         if (!bdi_write_congested(bdi))
283                 return 1;
284         if (bdi == current->backing_dev_info)
285                 return 1;
286         return 0;
287 }
288
289 /*
290  * We detected a synchronous write error writing a page out.  Probably
291  * -ENOSPC.  We need to propagate that into the address_space for a subsequent
292  * fsync(), msync() or close().
293  *
294  * The tricky part is that after writepage we cannot touch the mapping: nothing
295  * prevents it from being freed up.  But we have a ref on the page and once
296  * that page is locked, the mapping is pinned.
297  *
298  * We're allowed to run sleeping lock_page() here because we know the caller has
299  * __GFP_FS.
300  */
301 static void handle_write_error(struct address_space *mapping,
302                                 struct page *page, int error)
303 {
304         lock_page(page);
305         if (page_mapping(page) == mapping) {
306                 if (error == -ENOSPC)
307                         set_bit(AS_ENOSPC, &mapping->flags);
308                 else
309                         set_bit(AS_EIO, &mapping->flags);
310         }
311         unlock_page(page);
312 }
313
314 /*
315  * pageout is called by shrink_list() for each dirty page. Calls ->writepage().
316  */
317 static pageout_t pageout(struct page *page, struct address_space *mapping)
318 {
319         /*
320          * If the page is dirty, only perform writeback if that write
321          * will be non-blocking.  To prevent this allocation from being
322          * stalled by pagecache activity.  But note that there may be
323          * stalls if we need to run get_block().  We could test
324          * PagePrivate for that.
325          *
326          * If this process is currently in generic_file_write() against
327          * this page's queue, we can perform writeback even if that
328          * will block.
329          *
330          * If the page is swapcache, write it back even if that would
331          * block, for some throttling. This happens by accident, because
332          * swap_backing_dev_info is bust: it doesn't reflect the
333          * congestion state of the swapdevs.  Easy to fix, if needed.
334          * See swapfile.c:page_queue_congested().
335          */
336         if (!is_page_cache_freeable(page))
337                 return PAGE_KEEP;
338         if (!mapping) {
339                 /*
340                  * Some data journaling orphaned pages can have
341                  * page->mapping == NULL while being dirty with clean buffers.
342                  */
343                 if (PagePrivate(page)) {
344                         if (try_to_free_buffers(page)) {
345                                 ClearPageDirty(page);
346                                 printk("%s: orphaned page\n", __FUNCTION__);
347                                 return PAGE_CLEAN;
348                         }
349                 }
350                 return PAGE_KEEP;
351         }
352         if (mapping->a_ops->writepage == NULL)
353                 return PAGE_ACTIVATE;
354         if (!may_write_to_queue(mapping->backing_dev_info))
355                 return PAGE_KEEP;
356
357         if (clear_page_dirty_for_io(page)) {
358                 int res;
359                 struct writeback_control wbc = {
360                         .sync_mode = WB_SYNC_NONE,
361                         .nr_to_write = SWAP_CLUSTER_MAX,
362                         .nonblocking = 1,
363                         .for_reclaim = 1,
364                 };
365
366                 SetPageReclaim(page);
367                 res = mapping->a_ops->writepage(page, &wbc);
368                 if (res < 0)
369                         handle_write_error(mapping, page, res);
370                 if (res == WRITEPAGE_ACTIVATE) {
371                         ClearPageReclaim(page);
372                         return PAGE_ACTIVATE;
373                 }
374                 if (!PageWriteback(page)) {
375                         /* synchronous write or broken a_ops? */
376                         ClearPageReclaim(page);
377                 }
378
379                 return PAGE_SUCCESS;
380         }
381
382         return PAGE_CLEAN;
383 }
384
385 /*
386  * shrink_list adds the number of reclaimed pages to sc->nr_reclaimed
387  */
388 static int shrink_list(struct list_head *page_list, struct scan_control *sc)
389 {
390         LIST_HEAD(ret_pages);
391         struct pagevec freed_pvec;
392         int pgactivate = 0;
393         int reclaimed = 0;
394
395         cond_resched();
396
397         pagevec_init(&freed_pvec, 1);
398         while (!list_empty(page_list)) {
399                 struct address_space *mapping;
400                 struct page *page;
401                 int may_enter_fs;
402                 int referenced;
403
404                 cond_resched();
405
406                 page = lru_to_page(page_list);
407                 list_del(&page->lru);
408
409                 if (TestSetPageLocked(page))
410                         goto keep;
411
412                 BUG_ON(PageActive(page));
413
414                 sc->nr_scanned++;
415                 /* Double the slab pressure for mapped and swapcache pages */
416                 if (page_mapped(page) || PageSwapCache(page))
417                         sc->nr_scanned++;
418
419                 if (PageWriteback(page))
420                         goto keep_locked;
421
422                 referenced = page_referenced(page, 1);
423                 /* In active use or really unfreeable?  Activate it. */
424                 if (referenced && page_mapping_inuse(page))
425                         goto activate_locked;
426
427 #ifdef CONFIG_SWAP
428                 /*
429                  * Anonymous process memory has backing store?
430                  * Try to allocate it some swap space here.
431                  */
432                 if (PageAnon(page) && !PageSwapCache(page)) {
433                         if (!sc->may_swap)
434                                 goto keep_locked;
435                         if (!add_to_swap(page))
436                                 goto activate_locked;
437                 }
438 #endif /* CONFIG_SWAP */
439
440                 mapping = page_mapping(page);
441                 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
442                         (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
443
444                 /*
445                  * The page is mapped into the page tables of one or more
446                  * processes. Try to unmap it here.
447                  */
448                 if (page_mapped(page) && mapping) {
449                         switch (try_to_unmap(page)) {
450                         case SWAP_FAIL:
451                                 goto activate_locked;
452                         case SWAP_AGAIN:
453                                 goto keep_locked;
454                         case SWAP_SUCCESS:
455                                 ; /* try to free the page below */
456                         }
457                 }
458
459                 if (PageDirty(page)) {
460                         if (referenced)
461                                 goto keep_locked;
462                         if (!may_enter_fs)
463                                 goto keep_locked;
464                         if (laptop_mode && !sc->may_writepage)
465                                 goto keep_locked;
466
467                         /* Page is dirty, try to write it out here */
468                         switch(pageout(page, mapping)) {
469                         case PAGE_KEEP:
470                                 goto keep_locked;
471                         case PAGE_ACTIVATE:
472                                 goto activate_locked;
473                         case PAGE_SUCCESS:
474                                 if (PageWriteback(page) || PageDirty(page))
475                                         goto keep;
476                                 /*
477                                  * A synchronous write - probably a ramdisk.  Go
478                                  * ahead and try to reclaim the page.
479                                  */
480                                 if (TestSetPageLocked(page))
481                                         goto keep;
482                                 if (PageDirty(page) || PageWriteback(page))
483                                         goto keep_locked;
484                                 mapping = page_mapping(page);
485                         case PAGE_CLEAN:
486                                 ; /* try to free the page below */
487                         }
488                 }
489
490                 /*
491                  * If the page has buffers, try to free the buffer mappings
492                  * associated with this page. If we succeed we try to free
493                  * the page as well.
494                  *
495                  * We do this even if the page is PageDirty().
496                  * try_to_release_page() does not perform I/O, but it is
497                  * possible for a page to have PageDirty set, but it is actually
498                  * clean (all its buffers are clean).  This happens if the
499                  * buffers were written out directly, with submit_bh(). ext3
500                  * will do this, as well as the blockdev mapping. 
501                  * try_to_release_page() will discover that cleanness and will
502                  * drop the buffers and mark the page clean - it can be freed.
503                  *
504                  * Rarely, pages can have buffers and no ->mapping.  These are
505                  * the pages which were not successfully invalidated in
506                  * truncate_complete_page().  We try to drop those buffers here
507                  * and if that worked, and the page is no longer mapped into
508                  * process address space (page_count == 1) it can be freed.
509                  * Otherwise, leave the page on the LRU so it is swappable.
510                  */
511                 if (PagePrivate(page)) {
512                         if (!try_to_release_page(page, sc->gfp_mask))
513                                 goto activate_locked;
514                         if (!mapping && page_count(page) == 1)
515                                 goto free_it;
516                 }
517
518                 if (!mapping)
519                         goto keep_locked;       /* truncate got there first */
520
521                 write_lock_irq(&mapping->tree_lock);
522
523                 /*
524                  * The non-racy check for busy page.  It is critical to check
525                  * PageDirty _after_ making sure that the page is freeable and
526                  * not in use by anybody.       (pagecache + us == 2)
527                  */
528                 if (unlikely(page_count(page) != 2))
529                         goto cannot_free;
530                 smp_rmb();
531                 if (unlikely(PageDirty(page)))
532                         goto cannot_free;
533
534 #ifdef CONFIG_SWAP
535                 if (PageSwapCache(page)) {
536                         swp_entry_t swap = { .val = page_private(page) };
537                         __delete_from_swap_cache(page);
538                         write_unlock_irq(&mapping->tree_lock);
539                         swap_free(swap);
540                         __put_page(page);       /* The pagecache ref */
541                         goto free_it;
542                 }
543 #endif /* CONFIG_SWAP */
544
545                 __remove_from_page_cache(page);
546                 write_unlock_irq(&mapping->tree_lock);
547                 __put_page(page);
548
549 free_it:
550                 unlock_page(page);
551                 reclaimed++;
552                 if (!pagevec_add(&freed_pvec, page))
553                         __pagevec_release_nonlru(&freed_pvec);
554                 continue;
555
556 cannot_free:
557                 write_unlock_irq(&mapping->tree_lock);
558                 goto keep_locked;
559
560 activate_locked:
561                 SetPageActive(page);
562                 pgactivate++;
563 keep_locked:
564                 unlock_page(page);
565 keep:
566                 list_add(&page->lru, &ret_pages);
567                 BUG_ON(PageLRU(page));
568         }
569         list_splice(&ret_pages, page_list);
570         if (pagevec_count(&freed_pvec))
571                 __pagevec_release_nonlru(&freed_pvec);
572         mod_page_state(pgactivate, pgactivate);
573         sc->nr_reclaimed += reclaimed;
574         return reclaimed;
575 }
576
577 /*
578  * zone->lru_lock is heavily contended.  Some of the functions that
579  * shrink the lists perform better by taking out a batch of pages
580  * and working on them outside the LRU lock.
581  *
582  * For pagecache intensive workloads, this function is the hottest
583  * spot in the kernel (apart from copy_*_user functions).
584  *
585  * Appropriate locks must be held before calling this function.
586  *
587  * @nr_to_scan: The number of pages to look through on the list.
588  * @src:        The LRU list to pull pages off.
589  * @dst:        The temp list to put pages on to.
590  * @scanned:    The number of pages that were scanned.
591  *
592  * returns how many pages were moved onto *@dst.
593  */
594 static int isolate_lru_pages(int nr_to_scan, struct list_head *src,
595                              struct list_head *dst, int *scanned)
596 {
597         int nr_taken = 0;
598         struct page *page;
599         int scan = 0;
600
601         while (scan++ < nr_to_scan && !list_empty(src)) {
602                 page = lru_to_page(src);
603                 prefetchw_prev_lru_page(page, src, flags);
604
605                 if (!TestClearPageLRU(page))
606                         BUG();
607                 list_del(&page->lru);
608                 if (get_page_testone(page)) {
609                         /*
610                          * It is being freed elsewhere
611                          */
612                         __put_page(page);
613                         SetPageLRU(page);
614                         list_add(&page->lru, src);
615                         continue;
616                 } else {
617                         list_add(&page->lru, dst);
618                         nr_taken++;
619                 }
620         }
621
622         *scanned = scan;
623         return nr_taken;
624 }
625
626 /*
627  * shrink_cache() adds the number of pages reclaimed to sc->nr_reclaimed
628  */
629 static void shrink_cache(struct zone *zone, struct scan_control *sc)
630 {
631         LIST_HEAD(page_list);
632         struct pagevec pvec;
633         int max_scan = sc->nr_to_scan;
634
635         pagevec_init(&pvec, 1);
636
637         lru_add_drain();
638         spin_lock_irq(&zone->lru_lock);
639         while (max_scan > 0) {
640                 struct page *page;
641                 int nr_taken;
642                 int nr_scan;
643                 int nr_freed;
644
645                 nr_taken = isolate_lru_pages(sc->swap_cluster_max,
646                                              &zone->inactive_list,
647                                              &page_list, &nr_scan);
648                 zone->nr_inactive -= nr_taken;
649                 zone->pages_scanned += nr_scan;
650                 spin_unlock_irq(&zone->lru_lock);
651
652                 if (nr_taken == 0)
653                         goto done;
654
655                 max_scan -= nr_scan;
656                 if (current_is_kswapd())
657                         mod_page_state_zone(zone, pgscan_kswapd, nr_scan);
658                 else
659                         mod_page_state_zone(zone, pgscan_direct, nr_scan);
660                 nr_freed = shrink_list(&page_list, sc);
661                 if (current_is_kswapd())
662                         mod_page_state(kswapd_steal, nr_freed);
663                 mod_page_state_zone(zone, pgsteal, nr_freed);
664                 sc->nr_to_reclaim -= nr_freed;
665
666                 spin_lock_irq(&zone->lru_lock);
667                 /*
668                  * Put back any unfreeable pages.
669                  */
670                 while (!list_empty(&page_list)) {
671                         page = lru_to_page(&page_list);
672                         if (TestSetPageLRU(page))
673                                 BUG();
674                         list_del(&page->lru);
675                         if (PageActive(page))
676                                 add_page_to_active_list(zone, page);
677                         else
678                                 add_page_to_inactive_list(zone, page);
679                         if (!pagevec_add(&pvec, page)) {
680                                 spin_unlock_irq(&zone->lru_lock);
681                                 __pagevec_release(&pvec);
682                                 spin_lock_irq(&zone->lru_lock);
683                         }
684                 }
685         }
686         spin_unlock_irq(&zone->lru_lock);
687 done:
688         pagevec_release(&pvec);
689 }
690
691 /*
692  * This moves pages from the active list to the inactive list.
693  *
694  * We move them the other way if the page is referenced by one or more
695  * processes, from rmap.
696  *
697  * If the pages are mostly unmapped, the processing is fast and it is
698  * appropriate to hold zone->lru_lock across the whole operation.  But if
699  * the pages are mapped, the processing is slow (page_referenced()) so we
700  * should drop zone->lru_lock around each page.  It's impossible to balance
701  * this, so instead we remove the pages from the LRU while processing them.
702  * It is safe to rely on PG_active against the non-LRU pages in here because
703  * nobody will play with that bit on a non-LRU page.
704  *
705  * The downside is that we have to touch page->_count against each page.
706  * But we had to alter page->flags anyway.
707  */
708 static void
709 refill_inactive_zone(struct zone *zone, struct scan_control *sc)
710 {
711         int pgmoved;
712         int pgdeactivate = 0;
713         int pgscanned;
714         int nr_pages = sc->nr_to_scan;
715         LIST_HEAD(l_hold);      /* The pages which were snipped off */
716         LIST_HEAD(l_inactive);  /* Pages to go onto the inactive_list */
717         LIST_HEAD(l_active);    /* Pages to go onto the active_list */
718         struct page *page;
719         struct pagevec pvec;
720         int reclaim_mapped = 0;
721         long mapped_ratio;
722         long distress;
723         long swap_tendency;
724
725         lru_add_drain();
726         spin_lock_irq(&zone->lru_lock);
727         pgmoved = isolate_lru_pages(nr_pages, &zone->active_list,
728                                     &l_hold, &pgscanned);
729         zone->pages_scanned += pgscanned;
730         zone->nr_active -= pgmoved;
731         spin_unlock_irq(&zone->lru_lock);
732
733         /*
734          * `distress' is a measure of how much trouble we're having reclaiming
735          * pages.  0 -> no problems.  100 -> great trouble.
736          */
737         distress = 100 >> zone->prev_priority;
738
739         /*
740          * The point of this algorithm is to decide when to start reclaiming
741          * mapped memory instead of just pagecache.  Work out how much memory
742          * is mapped.
743          */
744         mapped_ratio = (sc->nr_mapped * 100) / total_memory;
745
746         /*
747          * Now decide how much we really want to unmap some pages.  The mapped
748          * ratio is downgraded - just because there's a lot of mapped memory
749          * doesn't necessarily mean that page reclaim isn't succeeding.
750          *
751          * The distress ratio is important - we don't want to start going oom.
752          *
753          * A 100% value of vm_swappiness overrides this algorithm altogether.
754          */
755         swap_tendency = mapped_ratio / 2 + distress + vm_swappiness;
756
757         /*
758          * Now use this metric to decide whether to start moving mapped memory
759          * onto the inactive list.
760          */
761         if (swap_tendency >= 100)
762                 reclaim_mapped = 1;
763
764         while (!list_empty(&l_hold)) {
765                 cond_resched();
766                 page = lru_to_page(&l_hold);
767                 list_del(&page->lru);
768                 if (page_mapped(page)) {
769                         if (!reclaim_mapped ||
770                             (total_swap_pages == 0 && PageAnon(page)) ||
771                             page_referenced(page, 0)) {
772                                 list_add(&page->lru, &l_active);
773                                 continue;
774                         }
775                 }
776                 list_add(&page->lru, &l_inactive);
777         }
778
779         pagevec_init(&pvec, 1);
780         pgmoved = 0;
781         spin_lock_irq(&zone->lru_lock);
782         while (!list_empty(&l_inactive)) {
783                 page = lru_to_page(&l_inactive);
784                 prefetchw_prev_lru_page(page, &l_inactive, flags);
785                 if (TestSetPageLRU(page))
786                         BUG();
787                 if (!TestClearPageActive(page))
788                         BUG();
789                 list_move(&page->lru, &zone->inactive_list);
790                 pgmoved++;
791                 if (!pagevec_add(&pvec, page)) {
792                         zone->nr_inactive += pgmoved;
793                         spin_unlock_irq(&zone->lru_lock);
794                         pgdeactivate += pgmoved;
795                         pgmoved = 0;
796                         if (buffer_heads_over_limit)
797                                 pagevec_strip(&pvec);
798                         __pagevec_release(&pvec);
799                         spin_lock_irq(&zone->lru_lock);
800                 }
801         }
802         zone->nr_inactive += pgmoved;
803         pgdeactivate += pgmoved;
804         if (buffer_heads_over_limit) {
805                 spin_unlock_irq(&zone->lru_lock);
806                 pagevec_strip(&pvec);
807                 spin_lock_irq(&zone->lru_lock);
808         }
809
810         pgmoved = 0;
811         while (!list_empty(&l_active)) {
812                 page = lru_to_page(&l_active);
813                 prefetchw_prev_lru_page(page, &l_active, flags);
814                 if (TestSetPageLRU(page))
815                         BUG();
816                 BUG_ON(!PageActive(page));
817                 list_move(&page->lru, &zone->active_list);
818                 pgmoved++;
819                 if (!pagevec_add(&pvec, page)) {
820                         zone->nr_active += pgmoved;
821                         pgmoved = 0;
822                         spin_unlock_irq(&zone->lru_lock);
823                         __pagevec_release(&pvec);
824                         spin_lock_irq(&zone->lru_lock);
825                 }
826         }
827         zone->nr_active += pgmoved;
828         spin_unlock_irq(&zone->lru_lock);
829         pagevec_release(&pvec);
830
831         mod_page_state_zone(zone, pgrefill, pgscanned);
832         mod_page_state(pgdeactivate, pgdeactivate);
833 }
834
835 /*
836  * This is a basic per-zone page freer.  Used by both kswapd and direct reclaim.
837  */
838 static void
839 shrink_zone(struct zone *zone, struct scan_control *sc)
840 {
841         unsigned long nr_active;
842         unsigned long nr_inactive;
843
844         atomic_inc(&zone->reclaim_in_progress);
845
846         /*
847          * Add one to `nr_to_scan' just to make sure that the kernel will
848          * slowly sift through the active list.
849          */
850         zone->nr_scan_active += (zone->nr_active >> sc->priority) + 1;
851         nr_active = zone->nr_scan_active;
852         if (nr_active >= sc->swap_cluster_max)
853                 zone->nr_scan_active = 0;
854         else
855                 nr_active = 0;
856
857         zone->nr_scan_inactive += (zone->nr_inactive >> sc->priority) + 1;
858         nr_inactive = zone->nr_scan_inactive;
859         if (nr_inactive >= sc->swap_cluster_max)
860                 zone->nr_scan_inactive = 0;
861         else
862                 nr_inactive = 0;
863
864         sc->nr_to_reclaim = sc->swap_cluster_max;
865
866         while (nr_active || nr_inactive) {
867                 if (nr_active) {
868                         sc->nr_to_scan = min(nr_active,
869                                         (unsigned long)sc->swap_cluster_max);
870                         nr_active -= sc->nr_to_scan;
871                         refill_inactive_zone(zone, sc);
872                 }
873
874                 if (nr_inactive) {
875                         sc->nr_to_scan = min(nr_inactive,
876                                         (unsigned long)sc->swap_cluster_max);
877                         nr_inactive -= sc->nr_to_scan;
878                         shrink_cache(zone, sc);
879                         if (sc->nr_to_reclaim <= 0)
880                                 break;
881                 }
882         }
883
884         throttle_vm_writeout();
885
886         atomic_dec(&zone->reclaim_in_progress);
887 }
888
889 /*
890  * This is the direct reclaim path, for page-allocating processes.  We only
891  * try to reclaim pages from zones which will satisfy the caller's allocation
892  * request.
893  *
894  * We reclaim from a zone even if that zone is over pages_high.  Because:
895  * a) The caller may be trying to free *extra* pages to satisfy a higher-order
896  *    allocation or
897  * b) The zones may be over pages_high but they must go *over* pages_high to
898  *    satisfy the `incremental min' zone defense algorithm.
899  *
900  * Returns the number of reclaimed pages.
901  *
902  * If a zone is deemed to be full of pinned pages then just give it a light
903  * scan then give up on it.
904  */
905 static void
906 shrink_caches(struct zone **zones, struct scan_control *sc)
907 {
908         int i;
909
910         for (i = 0; zones[i] != NULL; i++) {
911                 struct zone *zone = zones[i];
912
913                 if (zone->present_pages == 0)
914                         continue;
915
916                 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
917                         continue;
918
919                 zone->temp_priority = sc->priority;
920                 if (zone->prev_priority > sc->priority)
921                         zone->prev_priority = sc->priority;
922
923                 if (zone->all_unreclaimable && sc->priority != DEF_PRIORITY)
924                         continue;       /* Let kswapd poll it */
925
926                 shrink_zone(zone, sc);
927         }
928 }
929  
930 /*
931  * This is the main entry point to direct page reclaim.
932  *
933  * If a full scan of the inactive list fails to free enough memory then we
934  * are "out of memory" and something needs to be killed.
935  *
936  * If the caller is !__GFP_FS then the probability of a failure is reasonably
937  * high - the zone may be full of dirty or under-writeback pages, which this
938  * caller can't do much about.  We kick pdflush and take explicit naps in the
939  * hope that some of these pages can be written.  But if the allocating task
940  * holds filesystem locks which prevent writeout this might not work, and the
941  * allocation attempt will fail.
942  */
943 int try_to_free_pages(struct zone **zones, gfp_t gfp_mask)
944 {
945         int priority;
946         int ret = 0;
947         int total_scanned = 0, total_reclaimed = 0;
948         struct reclaim_state *reclaim_state = current->reclaim_state;
949         struct scan_control sc;
950         unsigned long lru_pages = 0;
951         int i;
952
953         sc.gfp_mask = gfp_mask;
954         sc.may_writepage = 0;
955         sc.may_swap = 1;
956
957         inc_page_state(allocstall);
958
959         for (i = 0; zones[i] != NULL; i++) {
960                 struct zone *zone = zones[i];
961
962                 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
963                         continue;
964
965                 zone->temp_priority = DEF_PRIORITY;
966                 lru_pages += zone->nr_active + zone->nr_inactive;
967         }
968
969         for (priority = DEF_PRIORITY; priority >= 0; priority--) {
970                 sc.nr_mapped = read_page_state(nr_mapped);
971                 sc.nr_scanned = 0;
972                 sc.nr_reclaimed = 0;
973                 sc.priority = priority;
974                 sc.swap_cluster_max = SWAP_CLUSTER_MAX;
975                 if (!priority)
976                         disable_swap_token();
977                 shrink_caches(zones, &sc);
978                 shrink_slab(sc.nr_scanned, gfp_mask, lru_pages);
979                 if (reclaim_state) {
980                         sc.nr_reclaimed += reclaim_state->reclaimed_slab;
981                         reclaim_state->reclaimed_slab = 0;
982                 }
983                 total_scanned += sc.nr_scanned;
984                 total_reclaimed += sc.nr_reclaimed;
985                 if (total_reclaimed >= sc.swap_cluster_max) {
986                         ret = 1;
987                         goto out;
988                 }
989
990                 /*
991                  * Try to write back as many pages as we just scanned.  This
992                  * tends to cause slow streaming writers to write data to the
993                  * disk smoothly, at the dirtying rate, which is nice.   But
994                  * that's undesirable in laptop mode, where we *want* lumpy
995                  * writeout.  So in laptop mode, write out the whole world.
996                  */
997                 if (total_scanned > sc.swap_cluster_max + sc.swap_cluster_max/2) {
998                         wakeup_pdflush(laptop_mode ? 0 : total_scanned);
999                         sc.may_writepage = 1;
1000                 }
1001
1002                 /* Take a nap, wait for some writeback to complete */
1003                 if (sc.nr_scanned && priority < DEF_PRIORITY - 2)
1004                         blk_congestion_wait(WRITE, HZ/10);
1005         }
1006 out:
1007         for (i = 0; zones[i] != 0; i++) {
1008                 struct zone *zone = zones[i];
1009
1010                 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
1011                         continue;
1012
1013                 zone->prev_priority = zone->temp_priority;
1014         }
1015         return ret;
1016 }
1017
1018 /*
1019  * For kswapd, balance_pgdat() will work across all this node's zones until
1020  * they are all at pages_high.
1021  *
1022  * If `nr_pages' is non-zero then it is the number of pages which are to be
1023  * reclaimed, regardless of the zone occupancies.  This is a software suspend
1024  * special.
1025  *
1026  * Returns the number of pages which were actually freed.
1027  *
1028  * There is special handling here for zones which are full of pinned pages.
1029  * This can happen if the pages are all mlocked, or if they are all used by
1030  * device drivers (say, ZONE_DMA).  Or if they are all in use by hugetlb.
1031  * What we do is to detect the case where all pages in the zone have been
1032  * scanned twice and there has been zero successful reclaim.  Mark the zone as
1033  * dead and from now on, only perform a short scan.  Basically we're polling
1034  * the zone for when the problem goes away.
1035  *
1036  * kswapd scans the zones in the highmem->normal->dma direction.  It skips
1037  * zones which have free_pages > pages_high, but once a zone is found to have
1038  * free_pages <= pages_high, we scan that zone and the lower zones regardless
1039  * of the number of free pages in the lower zones.  This interoperates with
1040  * the page allocator fallback scheme to ensure that aging of pages is balanced
1041  * across the zones.
1042  */
1043 static int balance_pgdat(pg_data_t *pgdat, int nr_pages, int order)
1044 {
1045         int to_free = nr_pages;
1046         int all_zones_ok;
1047         int priority;
1048         int i;
1049         int total_scanned, total_reclaimed;
1050         struct reclaim_state *reclaim_state = current->reclaim_state;
1051         struct scan_control sc;
1052
1053 loop_again:
1054         total_scanned = 0;
1055         total_reclaimed = 0;
1056         sc.gfp_mask = GFP_KERNEL;
1057         sc.may_writepage = 0;
1058         sc.may_swap = 1;
1059         sc.nr_mapped = read_page_state(nr_mapped);
1060
1061         inc_page_state(pageoutrun);
1062
1063         for (i = 0; i < pgdat->nr_zones; i++) {
1064                 struct zone *zone = pgdat->node_zones + i;
1065
1066                 zone->temp_priority = DEF_PRIORITY;
1067         }
1068
1069         for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1070                 int end_zone = 0;       /* Inclusive.  0 = ZONE_DMA */
1071                 unsigned long lru_pages = 0;
1072
1073                 /* The swap token gets in the way of swapout... */
1074                 if (!priority)
1075                         disable_swap_token();
1076
1077                 all_zones_ok = 1;
1078
1079                 if (nr_pages == 0) {
1080                         /*
1081                          * Scan in the highmem->dma direction for the highest
1082                          * zone which needs scanning
1083                          */
1084                         for (i = pgdat->nr_zones - 1; i >= 0; i--) {
1085                                 struct zone *zone = pgdat->node_zones + i;
1086
1087                                 if (zone->present_pages == 0)
1088                                         continue;
1089
1090                                 if (zone->all_unreclaimable &&
1091                                                 priority != DEF_PRIORITY)
1092                                         continue;
1093
1094                                 if (!zone_watermark_ok(zone, order,
1095                                                 zone->pages_high, 0, 0)) {
1096                                         end_zone = i;
1097                                         goto scan;
1098                                 }
1099                         }
1100                         goto out;
1101                 } else {
1102                         end_zone = pgdat->nr_zones - 1;
1103                 }
1104 scan:
1105                 for (i = 0; i <= end_zone; i++) {
1106                         struct zone *zone = pgdat->node_zones + i;
1107
1108                         lru_pages += zone->nr_active + zone->nr_inactive;
1109                 }
1110
1111                 /*
1112                  * Now scan the zone in the dma->highmem direction, stopping
1113                  * at the last zone which needs scanning.
1114                  *
1115                  * We do this because the page allocator works in the opposite
1116                  * direction.  This prevents the page allocator from allocating
1117                  * pages behind kswapd's direction of progress, which would
1118                  * cause too much scanning of the lower zones.
1119                  */
1120                 for (i = 0; i <= end_zone; i++) {
1121                         struct zone *zone = pgdat->node_zones + i;
1122                         int nr_slab;
1123
1124                         if (zone->present_pages == 0)
1125                                 continue;
1126
1127                         if (zone->all_unreclaimable && priority != DEF_PRIORITY)
1128                                 continue;
1129
1130                         if (nr_pages == 0) {    /* Not software suspend */
1131                                 if (!zone_watermark_ok(zone, order,
1132                                                 zone->pages_high, end_zone, 0))
1133                                         all_zones_ok = 0;
1134                         }
1135                         zone->temp_priority = priority;
1136                         if (zone->prev_priority > priority)
1137                                 zone->prev_priority = priority;
1138                         sc.nr_scanned = 0;
1139                         sc.nr_reclaimed = 0;
1140                         sc.priority = priority;
1141                         sc.swap_cluster_max = nr_pages? nr_pages : SWAP_CLUSTER_MAX;
1142                         atomic_inc(&zone->reclaim_in_progress);
1143                         shrink_zone(zone, &sc);
1144                         atomic_dec(&zone->reclaim_in_progress);
1145                         reclaim_state->reclaimed_slab = 0;
1146                         nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
1147                                                 lru_pages);
1148                         sc.nr_reclaimed += reclaim_state->reclaimed_slab;
1149                         total_reclaimed += sc.nr_reclaimed;
1150                         total_scanned += sc.nr_scanned;
1151                         if (zone->all_unreclaimable)
1152                                 continue;
1153                         if (nr_slab == 0 && zone->pages_scanned >=
1154                                     (zone->nr_active + zone->nr_inactive) * 4)
1155                                 zone->all_unreclaimable = 1;
1156                         /*
1157                          * If we've done a decent amount of scanning and
1158                          * the reclaim ratio is low, start doing writepage
1159                          * even in laptop mode
1160                          */
1161                         if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
1162                             total_scanned > total_reclaimed+total_reclaimed/2)
1163                                 sc.may_writepage = 1;
1164                 }
1165                 if (nr_pages && to_free > total_reclaimed)
1166                         continue;       /* swsusp: need to do more work */
1167                 if (all_zones_ok)
1168                         break;          /* kswapd: all done */
1169                 /*
1170                  * OK, kswapd is getting into trouble.  Take a nap, then take
1171                  * another pass across the zones.
1172                  */
1173                 if (total_scanned && priority < DEF_PRIORITY - 2)
1174                         blk_congestion_wait(WRITE, HZ/10);
1175
1176                 /*
1177                  * We do this so kswapd doesn't build up large priorities for
1178                  * example when it is freeing in parallel with allocators. It
1179                  * matches the direct reclaim path behaviour in terms of impact
1180                  * on zone->*_priority.
1181                  */
1182                 if ((total_reclaimed >= SWAP_CLUSTER_MAX) && (!nr_pages))
1183                         break;
1184         }
1185 out:
1186         for (i = 0; i < pgdat->nr_zones; i++) {
1187                 struct zone *zone = pgdat->node_zones + i;
1188
1189                 zone->prev_priority = zone->temp_priority;
1190         }
1191         if (!all_zones_ok) {
1192                 cond_resched();
1193                 goto loop_again;
1194         }
1195
1196         return total_reclaimed;
1197 }
1198
1199 /*
1200  * The background pageout daemon, started as a kernel thread
1201  * from the init process. 
1202  *
1203  * This basically trickles out pages so that we have _some_
1204  * free memory available even if there is no other activity
1205  * that frees anything up. This is needed for things like routing
1206  * etc, where we otherwise might have all activity going on in
1207  * asynchronous contexts that cannot page things out.
1208  *
1209  * If there are applications that are active memory-allocators
1210  * (most normal use), this basically shouldn't matter.
1211  */
1212 static int kswapd(void *p)
1213 {
1214         unsigned long order;
1215         pg_data_t *pgdat = (pg_data_t*)p;
1216         struct task_struct *tsk = current;
1217         DEFINE_WAIT(wait);
1218         struct reclaim_state reclaim_state = {
1219                 .reclaimed_slab = 0,
1220         };
1221         cpumask_t cpumask;
1222
1223         daemonize("kswapd%d", pgdat->node_id);
1224         cpumask = node_to_cpumask(pgdat->node_id);
1225         if (!cpus_empty(cpumask))
1226                 set_cpus_allowed(tsk, cpumask);
1227         current->reclaim_state = &reclaim_state;
1228
1229         /*
1230          * Tell the memory management that we're a "memory allocator",
1231          * and that if we need more memory we should get access to it
1232          * regardless (see "__alloc_pages()"). "kswapd" should
1233          * never get caught in the normal page freeing logic.
1234          *
1235          * (Kswapd normally doesn't need memory anyway, but sometimes
1236          * you need a small amount of memory in order to be able to
1237          * page out something else, and this flag essentially protects
1238          * us from recursively trying to free more memory as we're
1239          * trying to free the first piece of memory in the first place).
1240          */
1241         tsk->flags |= PF_MEMALLOC|PF_KSWAPD;
1242
1243         order = 0;
1244         for ( ; ; ) {
1245                 unsigned long new_order;
1246
1247                 try_to_freeze();
1248
1249                 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
1250                 new_order = pgdat->kswapd_max_order;
1251                 pgdat->kswapd_max_order = 0;
1252                 if (order < new_order) {
1253                         /*
1254                          * Don't sleep if someone wants a larger 'order'
1255                          * allocation
1256                          */
1257                         order = new_order;
1258                 } else {
1259                         schedule();
1260                         order = pgdat->kswapd_max_order;
1261                 }
1262                 finish_wait(&pgdat->kswapd_wait, &wait);
1263
1264                 balance_pgdat(pgdat, 0, order);
1265         }
1266         return 0;
1267 }
1268
1269 /*
1270  * A zone is low on free memory, so wake its kswapd task to service it.
1271  */
1272 void wakeup_kswapd(struct zone *zone, int order)
1273 {
1274         pg_data_t *pgdat;
1275
1276         if (zone->present_pages == 0)
1277                 return;
1278
1279         pgdat = zone->zone_pgdat;
1280         if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0))
1281                 return;
1282         if (pgdat->kswapd_max_order < order)
1283                 pgdat->kswapd_max_order = order;
1284         if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
1285                 return;
1286         if (!waitqueue_active(&pgdat->kswapd_wait))
1287                 return;
1288         wake_up_interruptible(&pgdat->kswapd_wait);
1289 }
1290
1291 #ifdef CONFIG_PM
1292 /*
1293  * Try to free `nr_pages' of memory, system-wide.  Returns the number of freed
1294  * pages.
1295  */
1296 int shrink_all_memory(int nr_pages)
1297 {
1298         pg_data_t *pgdat;
1299         int nr_to_free = nr_pages;
1300         int ret = 0;
1301         struct reclaim_state reclaim_state = {
1302                 .reclaimed_slab = 0,
1303         };
1304
1305         current->reclaim_state = &reclaim_state;
1306         for_each_pgdat(pgdat) {
1307                 int freed;
1308                 freed = balance_pgdat(pgdat, nr_to_free, 0);
1309                 ret += freed;
1310                 nr_to_free -= freed;
1311                 if (nr_to_free <= 0)
1312                         break;
1313         }
1314         current->reclaim_state = NULL;
1315         return ret;
1316 }
1317 #endif
1318
1319 #ifdef CONFIG_HOTPLUG_CPU
1320 /* It's optimal to keep kswapds on the same CPUs as their memory, but
1321    not required for correctness.  So if the last cpu in a node goes
1322    away, we get changed to run anywhere: as the first one comes back,
1323    restore their cpu bindings. */
1324 static int __devinit cpu_callback(struct notifier_block *nfb,
1325                                   unsigned long action,
1326                                   void *hcpu)
1327 {
1328         pg_data_t *pgdat;
1329         cpumask_t mask;
1330
1331         if (action == CPU_ONLINE) {
1332                 for_each_pgdat(pgdat) {
1333                         mask = node_to_cpumask(pgdat->node_id);
1334                         if (any_online_cpu(mask) != NR_CPUS)
1335                                 /* One of our CPUs online: restore mask */
1336                                 set_cpus_allowed(pgdat->kswapd, mask);
1337                 }
1338         }
1339         return NOTIFY_OK;
1340 }
1341 #endif /* CONFIG_HOTPLUG_CPU */
1342
1343 static int __init kswapd_init(void)
1344 {
1345         pg_data_t *pgdat;
1346         swap_setup();
1347         for_each_pgdat(pgdat)
1348                 pgdat->kswapd
1349                 = find_task_by_pid(kernel_thread(kswapd, pgdat, CLONE_KERNEL));
1350         total_memory = nr_free_pagecache_pages();
1351         hotcpu_notifier(cpu_callback, 0);
1352         return 0;
1353 }
1354
1355 module_init(kswapd_init)
1356
1357
1358 /*
1359  * Try to free up some pages from this zone through reclaim.
1360  */
1361 int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
1362 {
1363         struct scan_control sc;
1364         int nr_pages = 1 << order;
1365         int total_reclaimed = 0;
1366
1367         /* The reclaim may sleep, so don't do it if sleep isn't allowed */
1368         if (!(gfp_mask & __GFP_WAIT))
1369                 return 0;
1370         if (zone->all_unreclaimable)
1371                 return 0;
1372
1373         sc.gfp_mask = gfp_mask;
1374         sc.may_writepage = 0;
1375         sc.may_swap = 0;
1376         sc.nr_mapped = read_page_state(nr_mapped);
1377         sc.nr_scanned = 0;
1378         sc.nr_reclaimed = 0;
1379         /* scan at the highest priority */
1380         sc.priority = 0;
1381         disable_swap_token();
1382
1383         if (nr_pages > SWAP_CLUSTER_MAX)
1384                 sc.swap_cluster_max = nr_pages;
1385         else
1386                 sc.swap_cluster_max = SWAP_CLUSTER_MAX;
1387
1388         /* Don't reclaim the zone if there are other reclaimers active */
1389         if (atomic_read(&zone->reclaim_in_progress) > 0)
1390                 goto out;
1391
1392         shrink_zone(zone, &sc);
1393         total_reclaimed = sc.nr_reclaimed;
1394
1395  out:
1396         return total_reclaimed;
1397 }
1398
1399 asmlinkage long sys_set_zone_reclaim(unsigned int node, unsigned int zone,
1400                                      unsigned int state)
1401 {
1402         struct zone *z;
1403         int i;
1404
1405         if (!capable(CAP_SYS_ADMIN))
1406                 return -EACCES;
1407
1408         if (node >= MAX_NUMNODES || !node_online(node))
1409                 return -EINVAL;
1410
1411         /* This will break if we ever add more zones */
1412         if (!(zone & (1<<ZONE_DMA|1<<ZONE_NORMAL|1<<ZONE_HIGHMEM)))
1413                 return -EINVAL;
1414
1415         for (i = 0; i < MAX_NR_ZONES; i++) {
1416                 if (!(zone & 1<<i))
1417                         continue;
1418
1419                 z = &NODE_DATA(node)->node_zones[i];
1420
1421                 if (state)
1422                         z->reclaim_pages = 1;
1423                 else
1424                         z->reclaim_pages = 0;
1425         }
1426
1427         return 0;
1428 }