4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
8 * This file contains the default values for the operation of the
9 * Linux VM subsystem. Fine-tuning documentation can be found in
10 * Documentation/sysctl/vm.txt.
12 * Swap aging added 23.2.95, Stephen Tweedie.
13 * Buffermem limits added 12.3.98, Rik van Riel.
17 #include <linux/sched.h>
18 #include <linux/kernel_stat.h>
19 #include <linux/swap.h>
20 #include <linux/mman.h>
21 #include <linux/pagemap.h>
22 #include <linux/pagevec.h>
23 #include <linux/init.h>
24 #include <linux/export.h>
25 #include <linux/mm_inline.h>
26 #include <linux/percpu_counter.h>
27 #include <linux/percpu.h>
28 #include <linux/cpu.h>
29 #include <linux/notifier.h>
30 #include <linux/backing-dev.h>
31 #include <linux/memcontrol.h>
32 #include <linux/gfp.h>
36 /* How many pages do we try to swap or page in/out together? */
39 static DEFINE_PER_CPU(struct pagevec
[NR_LRU_LISTS
], lru_add_pvecs
);
40 static DEFINE_PER_CPU(struct pagevec
, lru_rotate_pvecs
);
41 static DEFINE_PER_CPU(struct pagevec
, lru_deactivate_pvecs
);
44 * This path almost never happens for VM activity - pages are normally
45 * freed via pagevecs. But it gets used by networking.
47 static void __page_cache_release(struct page
*page
)
50 struct zone
*zone
= page_zone(page
);
51 struct lruvec
*lruvec
;
54 spin_lock_irqsave(&zone
->lru_lock
, flags
);
55 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
56 VM_BUG_ON(!PageLRU(page
));
58 del_page_from_lru_list(page
, lruvec
, page_off_lru(page
));
59 spin_unlock_irqrestore(&zone
->lru_lock
, flags
);
63 static void __put_single_page(struct page
*page
)
65 __page_cache_release(page
);
66 free_hot_cold_page(page
, 0);
69 static void __put_compound_page(struct page
*page
)
71 compound_page_dtor
*dtor
;
73 __page_cache_release(page
);
74 dtor
= get_compound_page_dtor(page
);
78 static void put_compound_page(struct page
*page
)
80 if (unlikely(PageTail(page
))) {
81 /* __split_huge_page_refcount can run under us */
82 struct page
*page_head
= compound_trans_head(page
);
84 if (likely(page
!= page_head
&&
85 get_page_unless_zero(page_head
))) {
89 * THP can not break up slab pages so avoid taking
90 * compound_lock(). Slab performs non-atomic bit ops
91 * on page->flags for better performance. In particular
92 * slab_unlock() in slub used to be a hot path. It is
93 * still hot on arches that do not support
94 * this_cpu_cmpxchg_double().
96 if (PageSlab(page_head
)) {
98 if (put_page_testzero(page_head
))
101 atomic_dec(&page
->_mapcount
);
107 * page_head wasn't a dangling pointer but it
108 * may not be a head page anymore by the time
109 * we obtain the lock. That is ok as long as it
110 * can't be freed from under us.
112 flags
= compound_lock_irqsave(page_head
);
113 if (unlikely(!PageTail(page
))) {
114 /* __split_huge_page_refcount run before us */
115 compound_unlock_irqrestore(page_head
, flags
);
117 if (put_page_testzero(page_head
))
118 __put_single_page(page_head
);
120 if (put_page_testzero(page
))
121 __put_single_page(page
);
124 VM_BUG_ON(page_head
!= page
->first_page
);
126 * We can release the refcount taken by
127 * get_page_unless_zero() now that
128 * __split_huge_page_refcount() is blocked on
131 if (put_page_testzero(page_head
))
133 /* __split_huge_page_refcount will wait now */
134 VM_BUG_ON(page_mapcount(page
) <= 0);
135 atomic_dec(&page
->_mapcount
);
136 VM_BUG_ON(atomic_read(&page_head
->_count
) <= 0);
137 VM_BUG_ON(atomic_read(&page
->_count
) != 0);
138 compound_unlock_irqrestore(page_head
, flags
);
141 if (put_page_testzero(page_head
)) {
142 if (PageHead(page_head
))
143 __put_compound_page(page_head
);
145 __put_single_page(page_head
);
148 /* page_head is a dangling pointer */
149 VM_BUG_ON(PageTail(page
));
152 } else if (put_page_testzero(page
)) {
154 __put_compound_page(page
);
156 __put_single_page(page
);
160 void put_page(struct page
*page
)
162 if (unlikely(PageCompound(page
)))
163 put_compound_page(page
);
164 else if (put_page_testzero(page
))
165 __put_single_page(page
);
167 EXPORT_SYMBOL(put_page
);
170 * This function is exported but must not be called by anything other
171 * than get_page(). It implements the slow path of get_page().
173 bool __get_page_tail(struct page
*page
)
176 * This takes care of get_page() if run on a tail page
177 * returned by one of the get_user_pages/follow_page variants.
178 * get_user_pages/follow_page itself doesn't need the compound
179 * lock because it runs __get_page_tail_foll() under the
180 * proper PT lock that already serializes against
185 struct page
*page_head
= compound_trans_head(page
);
187 if (likely(page
!= page_head
&& get_page_unless_zero(page_head
))) {
189 /* Ref to put_compound_page() comment. */
190 if (PageSlab(page_head
)) {
191 if (likely(PageTail(page
))) {
192 __get_page_tail_foll(page
, false);
201 * page_head wasn't a dangling pointer but it
202 * may not be a head page anymore by the time
203 * we obtain the lock. That is ok as long as it
204 * can't be freed from under us.
206 flags
= compound_lock_irqsave(page_head
);
207 /* here __split_huge_page_refcount won't run anymore */
208 if (likely(PageTail(page
))) {
209 __get_page_tail_foll(page
, false);
212 compound_unlock_irqrestore(page_head
, flags
);
218 EXPORT_SYMBOL(__get_page_tail
);
221 * put_pages_list() - release a list of pages
222 * @pages: list of pages threaded on page->lru
224 * Release a list of pages which are strung together on page.lru. Currently
225 * used by read_cache_pages() and related error recovery code.
227 void put_pages_list(struct list_head
*pages
)
229 while (!list_empty(pages
)) {
232 victim
= list_entry(pages
->prev
, struct page
, lru
);
233 list_del(&victim
->lru
);
234 page_cache_release(victim
);
237 EXPORT_SYMBOL(put_pages_list
);
240 * get_kernel_pages() - pin kernel pages in memory
241 * @kiov: An array of struct kvec structures
242 * @nr_segs: number of segments to pin
243 * @write: pinning for read/write, currently ignored
244 * @pages: array that receives pointers to the pages pinned.
245 * Should be at least nr_segs long.
247 * Returns number of pages pinned. This may be fewer than the number
248 * requested. If nr_pages is 0 or negative, returns 0. If no pages
249 * were pinned, returns -errno. Each page returned must be released
250 * with a put_page() call when it is finished with.
252 int get_kernel_pages(const struct kvec
*kiov
, int nr_segs
, int write
,
257 for (seg
= 0; seg
< nr_segs
; seg
++) {
258 if (WARN_ON(kiov
[seg
].iov_len
!= PAGE_SIZE
))
261 pages
[seg
] = kmap_to_page(kiov
[seg
].iov_base
);
262 page_cache_get(pages
[seg
]);
267 EXPORT_SYMBOL_GPL(get_kernel_pages
);
270 * get_kernel_page() - pin a kernel page in memory
271 * @start: starting kernel address
272 * @write: pinning for read/write, currently ignored
273 * @pages: array that receives pointer to the page pinned.
274 * Must be at least nr_segs long.
276 * Returns 1 if page is pinned. If the page was not pinned, returns
277 * -errno. The page returned must be released with a put_page() call
278 * when it is finished with.
280 int get_kernel_page(unsigned long start
, int write
, struct page
**pages
)
282 const struct kvec kiov
= {
283 .iov_base
= (void *)start
,
287 return get_kernel_pages(&kiov
, 1, write
, pages
);
289 EXPORT_SYMBOL_GPL(get_kernel_page
);
291 static void pagevec_lru_move_fn(struct pagevec
*pvec
,
292 void (*move_fn
)(struct page
*page
, struct lruvec
*lruvec
, void *arg
),
296 struct zone
*zone
= NULL
;
297 struct lruvec
*lruvec
;
298 unsigned long flags
= 0;
300 for (i
= 0; i
< pagevec_count(pvec
); i
++) {
301 struct page
*page
= pvec
->pages
[i
];
302 struct zone
*pagezone
= page_zone(page
);
304 if (pagezone
!= zone
) {
306 spin_unlock_irqrestore(&zone
->lru_lock
, flags
);
308 spin_lock_irqsave(&zone
->lru_lock
, flags
);
311 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
312 (*move_fn
)(page
, lruvec
, arg
);
315 spin_unlock_irqrestore(&zone
->lru_lock
, flags
);
316 release_pages(pvec
->pages
, pvec
->nr
, pvec
->cold
);
317 pagevec_reinit(pvec
);
320 static void pagevec_move_tail_fn(struct page
*page
, struct lruvec
*lruvec
,
325 if (PageLRU(page
) && !PageActive(page
) && !PageUnevictable(page
)) {
326 enum lru_list lru
= page_lru_base_type(page
);
327 list_move_tail(&page
->lru
, &lruvec
->lists
[lru
]);
333 * pagevec_move_tail() must be called with IRQ disabled.
334 * Otherwise this may cause nasty races.
336 static void pagevec_move_tail(struct pagevec
*pvec
)
340 pagevec_lru_move_fn(pvec
, pagevec_move_tail_fn
, &pgmoved
);
341 __count_vm_events(PGROTATED
, pgmoved
);
345 * Writeback is about to end against a page which has been marked for immediate
346 * reclaim. If it still appears to be reclaimable, move it to the tail of the
349 void rotate_reclaimable_page(struct page
*page
)
351 if (!PageLocked(page
) && !PageDirty(page
) && !PageActive(page
) &&
352 !PageUnevictable(page
) && PageLRU(page
)) {
353 struct pagevec
*pvec
;
356 page_cache_get(page
);
357 local_irq_save(flags
);
358 pvec
= &__get_cpu_var(lru_rotate_pvecs
);
359 if (!pagevec_add(pvec
, page
))
360 pagevec_move_tail(pvec
);
361 local_irq_restore(flags
);
365 static void update_page_reclaim_stat(struct lruvec
*lruvec
,
366 int file
, int rotated
)
368 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
370 reclaim_stat
->recent_scanned
[file
]++;
372 reclaim_stat
->recent_rotated
[file
]++;
375 static void __activate_page(struct page
*page
, struct lruvec
*lruvec
,
378 if (PageLRU(page
) && !PageActive(page
) && !PageUnevictable(page
)) {
379 int file
= page_is_file_cache(page
);
380 int lru
= page_lru_base_type(page
);
382 del_page_from_lru_list(page
, lruvec
, lru
);
385 add_page_to_lru_list(page
, lruvec
, lru
);
387 __count_vm_event(PGACTIVATE
);
388 update_page_reclaim_stat(lruvec
, file
, 1);
393 static DEFINE_PER_CPU(struct pagevec
, activate_page_pvecs
);
395 static void activate_page_drain(int cpu
)
397 struct pagevec
*pvec
= &per_cpu(activate_page_pvecs
, cpu
);
399 if (pagevec_count(pvec
))
400 pagevec_lru_move_fn(pvec
, __activate_page
, NULL
);
403 void activate_page(struct page
*page
)
405 if (PageLRU(page
) && !PageActive(page
) && !PageUnevictable(page
)) {
406 struct pagevec
*pvec
= &get_cpu_var(activate_page_pvecs
);
408 page_cache_get(page
);
409 if (!pagevec_add(pvec
, page
))
410 pagevec_lru_move_fn(pvec
, __activate_page
, NULL
);
411 put_cpu_var(activate_page_pvecs
);
416 static inline void activate_page_drain(int cpu
)
420 void activate_page(struct page
*page
)
422 struct zone
*zone
= page_zone(page
);
424 spin_lock_irq(&zone
->lru_lock
);
425 __activate_page(page
, mem_cgroup_page_lruvec(page
, zone
), NULL
);
426 spin_unlock_irq(&zone
->lru_lock
);
431 * Mark a page as having seen activity.
433 * inactive,unreferenced -> inactive,referenced
434 * inactive,referenced -> active,unreferenced
435 * active,unreferenced -> active,referenced
437 void mark_page_accessed(struct page
*page
)
439 if (!PageActive(page
) && !PageUnevictable(page
) &&
440 PageReferenced(page
) && PageLRU(page
)) {
442 ClearPageReferenced(page
);
443 } else if (!PageReferenced(page
)) {
444 SetPageReferenced(page
);
447 EXPORT_SYMBOL(mark_page_accessed
);
450 * Order of operations is important: flush the pagevec when it's already
451 * full, not when adding the last page, to make sure that last page is
452 * not added to the LRU directly when passed to this function. Because
453 * mark_page_accessed() (called after this when writing) only activates
454 * pages that are on the LRU, linear writes in subpage chunks would see
455 * every PAGEVEC_SIZE page activated, which is unexpected.
457 void __lru_cache_add(struct page
*page
, enum lru_list lru
)
459 struct pagevec
*pvec
= &get_cpu_var(lru_add_pvecs
)[lru
];
461 page_cache_get(page
);
462 if (!pagevec_space(pvec
))
463 __pagevec_lru_add(pvec
, lru
);
464 pagevec_add(pvec
, page
);
465 put_cpu_var(lru_add_pvecs
);
467 EXPORT_SYMBOL(__lru_cache_add
);
470 * lru_cache_add_lru - add a page to a page list
471 * @page: the page to be added to the LRU.
472 * @lru: the LRU list to which the page is added.
474 void lru_cache_add_lru(struct page
*page
, enum lru_list lru
)
476 if (PageActive(page
)) {
477 VM_BUG_ON(PageUnevictable(page
));
478 ClearPageActive(page
);
479 } else if (PageUnevictable(page
)) {
480 VM_BUG_ON(PageActive(page
));
481 ClearPageUnevictable(page
);
484 VM_BUG_ON(PageLRU(page
) || PageActive(page
) || PageUnevictable(page
));
485 __lru_cache_add(page
, lru
);
489 * add_page_to_unevictable_list - add a page to the unevictable list
490 * @page: the page to be added to the unevictable list
492 * Add page directly to its zone's unevictable list. To avoid races with
493 * tasks that might be making the page evictable, through eg. munlock,
494 * munmap or exit, while it's not on the lru, we want to add the page
495 * while it's locked or otherwise "invisible" to other tasks. This is
496 * difficult to do when using the pagevec cache, so bypass that.
498 void add_page_to_unevictable_list(struct page
*page
)
500 struct zone
*zone
= page_zone(page
);
501 struct lruvec
*lruvec
;
503 spin_lock_irq(&zone
->lru_lock
);
504 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
505 SetPageUnevictable(page
);
507 add_page_to_lru_list(page
, lruvec
, LRU_UNEVICTABLE
);
508 spin_unlock_irq(&zone
->lru_lock
);
512 * If the page can not be invalidated, it is moved to the
513 * inactive list to speed up its reclaim. It is moved to the
514 * head of the list, rather than the tail, to give the flusher
515 * threads some time to write it out, as this is much more
516 * effective than the single-page writeout from reclaim.
518 * If the page isn't page_mapped and dirty/writeback, the page
519 * could reclaim asap using PG_reclaim.
521 * 1. active, mapped page -> none
522 * 2. active, dirty/writeback page -> inactive, head, PG_reclaim
523 * 3. inactive, mapped page -> none
524 * 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim
525 * 5. inactive, clean -> inactive, tail
528 * In 4, why it moves inactive's head, the VM expects the page would
529 * be write it out by flusher threads as this is much more effective
530 * than the single-page writeout from reclaim.
532 static void lru_deactivate_fn(struct page
*page
, struct lruvec
*lruvec
,
541 if (PageUnevictable(page
))
544 /* Some processes are using the page */
545 if (page_mapped(page
))
548 active
= PageActive(page
);
549 file
= page_is_file_cache(page
);
550 lru
= page_lru_base_type(page
);
552 del_page_from_lru_list(page
, lruvec
, lru
+ active
);
553 ClearPageActive(page
);
554 ClearPageReferenced(page
);
555 add_page_to_lru_list(page
, lruvec
, lru
);
557 if (PageWriteback(page
) || PageDirty(page
)) {
559 * PG_reclaim could be raced with end_page_writeback
560 * It can make readahead confusing. But race window
561 * is _really_ small and it's non-critical problem.
563 SetPageReclaim(page
);
566 * The page's writeback ends up during pagevec
567 * We moves tha page into tail of inactive.
569 list_move_tail(&page
->lru
, &lruvec
->lists
[lru
]);
570 __count_vm_event(PGROTATED
);
574 __count_vm_event(PGDEACTIVATE
);
575 update_page_reclaim_stat(lruvec
, file
, 0);
579 * Drain pages out of the cpu's pagevecs.
580 * Either "cpu" is the current CPU, and preemption has already been
581 * disabled; or "cpu" is being hot-unplugged, and is already dead.
583 void lru_add_drain_cpu(int cpu
)
585 struct pagevec
*pvecs
= per_cpu(lru_add_pvecs
, cpu
);
586 struct pagevec
*pvec
;
590 pvec
= &pvecs
[lru
- LRU_BASE
];
591 if (pagevec_count(pvec
))
592 __pagevec_lru_add(pvec
, lru
);
595 pvec
= &per_cpu(lru_rotate_pvecs
, cpu
);
596 if (pagevec_count(pvec
)) {
599 /* No harm done if a racing interrupt already did this */
600 local_irq_save(flags
);
601 pagevec_move_tail(pvec
);
602 local_irq_restore(flags
);
605 pvec
= &per_cpu(lru_deactivate_pvecs
, cpu
);
606 if (pagevec_count(pvec
))
607 pagevec_lru_move_fn(pvec
, lru_deactivate_fn
, NULL
);
609 activate_page_drain(cpu
);
613 * deactivate_page - forcefully deactivate a page
614 * @page: page to deactivate
616 * This function hints the VM that @page is a good reclaim candidate,
617 * for example if its invalidation fails due to the page being dirty
618 * or under writeback.
620 void deactivate_page(struct page
*page
)
623 * In a workload with many unevictable page such as mprotect, unevictable
624 * page deactivation for accelerating reclaim is pointless.
626 if (PageUnevictable(page
))
629 if (likely(get_page_unless_zero(page
))) {
630 struct pagevec
*pvec
= &get_cpu_var(lru_deactivate_pvecs
);
632 if (!pagevec_add(pvec
, page
))
633 pagevec_lru_move_fn(pvec
, lru_deactivate_fn
, NULL
);
634 put_cpu_var(lru_deactivate_pvecs
);
638 void lru_add_drain(void)
640 lru_add_drain_cpu(get_cpu());
644 static void lru_add_drain_per_cpu(struct work_struct
*dummy
)
650 * Returns 0 for success
652 int lru_add_drain_all(void)
654 return schedule_on_each_cpu(lru_add_drain_per_cpu
);
658 * Batched page_cache_release(). Decrement the reference count on all the
659 * passed pages. If it fell to zero then remove the page from the LRU and
662 * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
663 * for the remainder of the operation.
665 * The locking in this function is against shrink_inactive_list(): we recheck
666 * the page count inside the lock to see whether shrink_inactive_list()
667 * grabbed the page via the LRU. If it did, give up: shrink_inactive_list()
670 void release_pages(struct page
**pages
, int nr
, int cold
)
673 LIST_HEAD(pages_to_free
);
674 struct zone
*zone
= NULL
;
675 struct lruvec
*lruvec
;
676 unsigned long uninitialized_var(flags
);
678 for (i
= 0; i
< nr
; i
++) {
679 struct page
*page
= pages
[i
];
681 if (unlikely(PageCompound(page
))) {
683 spin_unlock_irqrestore(&zone
->lru_lock
, flags
);
686 put_compound_page(page
);
690 if (!put_page_testzero(page
))
694 struct zone
*pagezone
= page_zone(page
);
696 if (pagezone
!= zone
) {
698 spin_unlock_irqrestore(&zone
->lru_lock
,
701 spin_lock_irqsave(&zone
->lru_lock
, flags
);
704 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
705 VM_BUG_ON(!PageLRU(page
));
706 __ClearPageLRU(page
);
707 del_page_from_lru_list(page
, lruvec
, page_off_lru(page
));
710 list_add(&page
->lru
, &pages_to_free
);
713 spin_unlock_irqrestore(&zone
->lru_lock
, flags
);
715 free_hot_cold_page_list(&pages_to_free
, cold
);
717 EXPORT_SYMBOL(release_pages
);
720 * The pages which we're about to release may be in the deferred lru-addition
721 * queues. That would prevent them from really being freed right now. That's
722 * OK from a correctness point of view but is inefficient - those pages may be
723 * cache-warm and we want to give them back to the page allocator ASAP.
725 * So __pagevec_release() will drain those queues here. __pagevec_lru_add()
726 * and __pagevec_lru_add_active() call release_pages() directly to avoid
729 void __pagevec_release(struct pagevec
*pvec
)
732 release_pages(pvec
->pages
, pagevec_count(pvec
), pvec
->cold
);
733 pagevec_reinit(pvec
);
735 EXPORT_SYMBOL(__pagevec_release
);
737 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
738 /* used by __split_huge_page_refcount() */
739 void lru_add_page_tail(struct page
*page
, struct page
*page_tail
,
740 struct lruvec
*lruvec
)
742 int uninitialized_var(active
);
746 VM_BUG_ON(!PageHead(page
));
747 VM_BUG_ON(PageCompound(page_tail
));
748 VM_BUG_ON(PageLRU(page_tail
));
749 VM_BUG_ON(NR_CPUS
!= 1 &&
750 !spin_is_locked(&lruvec_zone(lruvec
)->lru_lock
));
752 SetPageLRU(page_tail
);
754 if (page_evictable(page_tail
)) {
755 if (PageActive(page
)) {
756 SetPageActive(page_tail
);
758 lru
= LRU_ACTIVE_ANON
;
761 lru
= LRU_INACTIVE_ANON
;
764 SetPageUnevictable(page_tail
);
765 lru
= LRU_UNEVICTABLE
;
768 if (likely(PageLRU(page
)))
769 list_add_tail(&page_tail
->lru
, &page
->lru
);
771 struct list_head
*list_head
;
773 * Head page has not yet been counted, as an hpage,
774 * so we must account for each subpage individually.
776 * Use the standard add function to put page_tail on the list,
777 * but then correct its position so they all end up in order.
779 add_page_to_lru_list(page_tail
, lruvec
, lru
);
780 list_head
= page_tail
->lru
.prev
;
781 list_move_tail(&page_tail
->lru
, list_head
);
784 if (!PageUnevictable(page
))
785 update_page_reclaim_stat(lruvec
, file
, active
);
787 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
789 static void __pagevec_lru_add_fn(struct page
*page
, struct lruvec
*lruvec
,
792 enum lru_list lru
= (enum lru_list
)arg
;
793 int file
= is_file_lru(lru
);
794 int active
= is_active_lru(lru
);
796 VM_BUG_ON(PageActive(page
));
797 VM_BUG_ON(PageUnevictable(page
));
798 VM_BUG_ON(PageLRU(page
));
803 add_page_to_lru_list(page
, lruvec
, lru
);
804 update_page_reclaim_stat(lruvec
, file
, active
);
808 * Add the passed pages to the LRU, then drop the caller's refcount
809 * on them. Reinitialises the caller's pagevec.
811 void __pagevec_lru_add(struct pagevec
*pvec
, enum lru_list lru
)
813 VM_BUG_ON(is_unevictable_lru(lru
));
815 pagevec_lru_move_fn(pvec
, __pagevec_lru_add_fn
, (void *)lru
);
817 EXPORT_SYMBOL(__pagevec_lru_add
);
820 * pagevec_lookup - gang pagecache lookup
821 * @pvec: Where the resulting pages are placed
822 * @mapping: The address_space to search
823 * @start: The starting page index
824 * @nr_pages: The maximum number of pages
826 * pagevec_lookup() will search for and return a group of up to @nr_pages pages
827 * in the mapping. The pages are placed in @pvec. pagevec_lookup() takes a
828 * reference against the pages in @pvec.
830 * The search returns a group of mapping-contiguous pages with ascending
831 * indexes. There may be holes in the indices due to not-present pages.
833 * pagevec_lookup() returns the number of pages which were found.
835 unsigned pagevec_lookup(struct pagevec
*pvec
, struct address_space
*mapping
,
836 pgoff_t start
, unsigned nr_pages
)
838 pvec
->nr
= find_get_pages(mapping
, start
, nr_pages
, pvec
->pages
);
839 return pagevec_count(pvec
);
841 EXPORT_SYMBOL(pagevec_lookup
);
843 unsigned pagevec_lookup_tag(struct pagevec
*pvec
, struct address_space
*mapping
,
844 pgoff_t
*index
, int tag
, unsigned nr_pages
)
846 pvec
->nr
= find_get_pages_tag(mapping
, index
, tag
,
847 nr_pages
, pvec
->pages
);
848 return pagevec_count(pvec
);
850 EXPORT_SYMBOL(pagevec_lookup_tag
);
853 * Perform any setup for the swap system
855 void __init
swap_setup(void)
857 unsigned long megs
= totalram_pages
>> (20 - PAGE_SHIFT
);
860 bdi_init(swapper_space
.backing_dev_info
);
863 /* Use a smaller cluster for small-memory machines */
869 * Right now other parts of the system means that we
870 * _really_ don't want to cluster much more
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