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>
33 #include <linux/uio.h>
37 /* How many pages do we try to swap or page in/out together? */
40 static DEFINE_PER_CPU(struct pagevec
[NR_LRU_LISTS
], lru_add_pvecs
);
41 static DEFINE_PER_CPU(struct pagevec
, lru_rotate_pvecs
);
42 static DEFINE_PER_CPU(struct pagevec
, lru_deactivate_pvecs
);
45 * This path almost never happens for VM activity - pages are normally
46 * freed via pagevecs. But it gets used by networking.
48 static void __page_cache_release(struct page
*page
)
51 struct zone
*zone
= page_zone(page
);
52 struct lruvec
*lruvec
;
55 spin_lock_irqsave(&zone
->lru_lock
, flags
);
56 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
57 VM_BUG_ON(!PageLRU(page
));
59 del_page_from_lru_list(page
, lruvec
, page_off_lru(page
));
60 spin_unlock_irqrestore(&zone
->lru_lock
, flags
);
64 static void __put_single_page(struct page
*page
)
66 __page_cache_release(page
);
67 free_hot_cold_page(page
, 0);
70 static void __put_compound_page(struct page
*page
)
72 compound_page_dtor
*dtor
;
74 __page_cache_release(page
);
75 dtor
= get_compound_page_dtor(page
);
79 static void put_compound_page(struct page
*page
)
81 if (unlikely(PageTail(page
))) {
82 /* __split_huge_page_refcount can run under us */
83 struct page
*page_head
= compound_trans_head(page
);
85 if (likely(page
!= page_head
&&
86 get_page_unless_zero(page_head
))) {
90 * THP can not break up slab pages so avoid taking
91 * compound_lock(). Slab performs non-atomic bit ops
92 * on page->flags for better performance. In particular
93 * slab_unlock() in slub used to be a hot path. It is
94 * still hot on arches that do not support
95 * this_cpu_cmpxchg_double().
97 if (PageSlab(page_head
)) {
99 if (put_page_testzero(page_head
))
102 atomic_dec(&page
->_mapcount
);
108 * page_head wasn't a dangling pointer but it
109 * may not be a head page anymore by the time
110 * we obtain the lock. That is ok as long as it
111 * can't be freed from under us.
113 flags
= compound_lock_irqsave(page_head
);
114 if (unlikely(!PageTail(page
))) {
115 /* __split_huge_page_refcount run before us */
116 compound_unlock_irqrestore(page_head
, flags
);
118 if (put_page_testzero(page_head
))
119 __put_single_page(page_head
);
121 if (put_page_testzero(page
))
122 __put_single_page(page
);
125 VM_BUG_ON(page_head
!= page
->first_page
);
127 * We can release the refcount taken by
128 * get_page_unless_zero() now that
129 * __split_huge_page_refcount() is blocked on
132 if (put_page_testzero(page_head
))
134 /* __split_huge_page_refcount will wait now */
135 VM_BUG_ON(page_mapcount(page
) <= 0);
136 atomic_dec(&page
->_mapcount
);
137 VM_BUG_ON(atomic_read(&page_head
->_count
) <= 0);
138 VM_BUG_ON(atomic_read(&page
->_count
) != 0);
139 compound_unlock_irqrestore(page_head
, flags
);
142 if (put_page_testzero(page_head
)) {
143 if (PageHead(page_head
))
144 __put_compound_page(page_head
);
146 __put_single_page(page_head
);
149 /* page_head is a dangling pointer */
150 VM_BUG_ON(PageTail(page
));
153 } else if (put_page_testzero(page
)) {
155 __put_compound_page(page
);
157 __put_single_page(page
);
161 void put_page(struct page
*page
)
163 if (unlikely(PageCompound(page
)))
164 put_compound_page(page
);
165 else if (put_page_testzero(page
))
166 __put_single_page(page
);
168 EXPORT_SYMBOL(put_page
);
171 * This function is exported but must not be called by anything other
172 * than get_page(). It implements the slow path of get_page().
174 bool __get_page_tail(struct page
*page
)
177 * This takes care of get_page() if run on a tail page
178 * returned by one of the get_user_pages/follow_page variants.
179 * get_user_pages/follow_page itself doesn't need the compound
180 * lock because it runs __get_page_tail_foll() under the
181 * proper PT lock that already serializes against
186 struct page
*page_head
= compound_trans_head(page
);
188 if (likely(page
!= page_head
&& get_page_unless_zero(page_head
))) {
190 /* Ref to put_compound_page() comment. */
191 if (PageSlab(page_head
)) {
192 if (likely(PageTail(page
))) {
193 __get_page_tail_foll(page
, false);
202 * page_head wasn't a dangling pointer but it
203 * may not be a head page anymore by the time
204 * we obtain the lock. That is ok as long as it
205 * can't be freed from under us.
207 flags
= compound_lock_irqsave(page_head
);
208 /* here __split_huge_page_refcount won't run anymore */
209 if (likely(PageTail(page
))) {
210 __get_page_tail_foll(page
, false);
213 compound_unlock_irqrestore(page_head
, flags
);
219 EXPORT_SYMBOL(__get_page_tail
);
222 * put_pages_list() - release a list of pages
223 * @pages: list of pages threaded on page->lru
225 * Release a list of pages which are strung together on page.lru. Currently
226 * used by read_cache_pages() and related error recovery code.
228 void put_pages_list(struct list_head
*pages
)
230 while (!list_empty(pages
)) {
233 victim
= list_entry(pages
->prev
, struct page
, lru
);
234 list_del(&victim
->lru
);
235 page_cache_release(victim
);
238 EXPORT_SYMBOL(put_pages_list
);
241 * get_kernel_pages() - pin kernel pages in memory
242 * @kiov: An array of struct kvec structures
243 * @nr_segs: number of segments to pin
244 * @write: pinning for read/write, currently ignored
245 * @pages: array that receives pointers to the pages pinned.
246 * Should be at least nr_segs long.
248 * Returns number of pages pinned. This may be fewer than the number
249 * requested. If nr_pages is 0 or negative, returns 0. If no pages
250 * were pinned, returns -errno. Each page returned must be released
251 * with a put_page() call when it is finished with.
253 int get_kernel_pages(const struct kvec
*kiov
, int nr_segs
, int write
,
258 for (seg
= 0; seg
< nr_segs
; seg
++) {
259 if (WARN_ON(kiov
[seg
].iov_len
!= PAGE_SIZE
))
262 pages
[seg
] = kmap_to_page(kiov
[seg
].iov_base
);
263 page_cache_get(pages
[seg
]);
268 EXPORT_SYMBOL_GPL(get_kernel_pages
);
271 * get_kernel_page() - pin a kernel page in memory
272 * @start: starting kernel address
273 * @write: pinning for read/write, currently ignored
274 * @pages: array that receives pointer to the page pinned.
275 * Must be at least nr_segs long.
277 * Returns 1 if page is pinned. If the page was not pinned, returns
278 * -errno. The page returned must be released with a put_page() call
279 * when it is finished with.
281 int get_kernel_page(unsigned long start
, int write
, struct page
**pages
)
283 const struct kvec kiov
= {
284 .iov_base
= (void *)start
,
288 return get_kernel_pages(&kiov
, 1, write
, pages
);
290 EXPORT_SYMBOL_GPL(get_kernel_page
);
292 static void pagevec_lru_move_fn(struct pagevec
*pvec
,
293 void (*move_fn
)(struct page
*page
, struct lruvec
*lruvec
, void *arg
),
297 struct zone
*zone
= NULL
;
298 struct lruvec
*lruvec
;
299 unsigned long flags
= 0;
301 for (i
= 0; i
< pagevec_count(pvec
); i
++) {
302 struct page
*page
= pvec
->pages
[i
];
303 struct zone
*pagezone
= page_zone(page
);
305 if (pagezone
!= zone
) {
307 spin_unlock_irqrestore(&zone
->lru_lock
, flags
);
309 spin_lock_irqsave(&zone
->lru_lock
, flags
);
312 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
313 (*move_fn
)(page
, lruvec
, arg
);
316 spin_unlock_irqrestore(&zone
->lru_lock
, flags
);
317 release_pages(pvec
->pages
, pvec
->nr
, pvec
->cold
);
318 pagevec_reinit(pvec
);
321 static void pagevec_move_tail_fn(struct page
*page
, struct lruvec
*lruvec
,
326 if (PageLRU(page
) && !PageActive(page
) && !PageUnevictable(page
)) {
327 enum lru_list lru
= page_lru_base_type(page
);
328 list_move_tail(&page
->lru
, &lruvec
->lists
[lru
]);
334 * pagevec_move_tail() must be called with IRQ disabled.
335 * Otherwise this may cause nasty races.
337 static void pagevec_move_tail(struct pagevec
*pvec
)
341 pagevec_lru_move_fn(pvec
, pagevec_move_tail_fn
, &pgmoved
);
342 __count_vm_events(PGROTATED
, pgmoved
);
346 * Writeback is about to end against a page which has been marked for immediate
347 * reclaim. If it still appears to be reclaimable, move it to the tail of the
350 void rotate_reclaimable_page(struct page
*page
)
352 if (!PageLocked(page
) && !PageDirty(page
) && !PageActive(page
) &&
353 !PageUnevictable(page
) && PageLRU(page
)) {
354 struct pagevec
*pvec
;
357 page_cache_get(page
);
358 local_irq_save(flags
);
359 pvec
= &__get_cpu_var(lru_rotate_pvecs
);
360 if (!pagevec_add(pvec
, page
))
361 pagevec_move_tail(pvec
);
362 local_irq_restore(flags
);
366 static void update_page_reclaim_stat(struct lruvec
*lruvec
,
367 int file
, int rotated
)
369 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
371 reclaim_stat
->recent_scanned
[file
]++;
373 reclaim_stat
->recent_rotated
[file
]++;
376 static void __activate_page(struct page
*page
, struct lruvec
*lruvec
,
379 if (PageLRU(page
) && !PageActive(page
) && !PageUnevictable(page
)) {
380 int file
= page_is_file_cache(page
);
381 int lru
= page_lru_base_type(page
);
383 del_page_from_lru_list(page
, lruvec
, lru
);
386 add_page_to_lru_list(page
, lruvec
, lru
);
388 __count_vm_event(PGACTIVATE
);
389 update_page_reclaim_stat(lruvec
, file
, 1);
394 static DEFINE_PER_CPU(struct pagevec
, activate_page_pvecs
);
396 static void activate_page_drain(int cpu
)
398 struct pagevec
*pvec
= &per_cpu(activate_page_pvecs
, cpu
);
400 if (pagevec_count(pvec
))
401 pagevec_lru_move_fn(pvec
, __activate_page
, NULL
);
404 void activate_page(struct page
*page
)
406 if (PageLRU(page
) && !PageActive(page
) && !PageUnevictable(page
)) {
407 struct pagevec
*pvec
= &get_cpu_var(activate_page_pvecs
);
409 page_cache_get(page
);
410 if (!pagevec_add(pvec
, page
))
411 pagevec_lru_move_fn(pvec
, __activate_page
, NULL
);
412 put_cpu_var(activate_page_pvecs
);
417 static inline void activate_page_drain(int cpu
)
421 void activate_page(struct page
*page
)
423 struct zone
*zone
= page_zone(page
);
425 spin_lock_irq(&zone
->lru_lock
);
426 __activate_page(page
, mem_cgroup_page_lruvec(page
, zone
), NULL
);
427 spin_unlock_irq(&zone
->lru_lock
);
432 * Mark a page as having seen activity.
434 * inactive,unreferenced -> inactive,referenced
435 * inactive,referenced -> active,unreferenced
436 * active,unreferenced -> active,referenced
438 void mark_page_accessed(struct page
*page
)
440 if (!PageActive(page
) && !PageUnevictable(page
) &&
441 PageReferenced(page
) && PageLRU(page
)) {
443 ClearPageReferenced(page
);
444 } else if (!PageReferenced(page
)) {
445 SetPageReferenced(page
);
448 EXPORT_SYMBOL(mark_page_accessed
);
451 * Order of operations is important: flush the pagevec when it's already
452 * full, not when adding the last page, to make sure that last page is
453 * not added to the LRU directly when passed to this function. Because
454 * mark_page_accessed() (called after this when writing) only activates
455 * pages that are on the LRU, linear writes in subpage chunks would see
456 * every PAGEVEC_SIZE page activated, which is unexpected.
458 void __lru_cache_add(struct page
*page
, enum lru_list lru
)
460 struct pagevec
*pvec
= &get_cpu_var(lru_add_pvecs
)[lru
];
462 page_cache_get(page
);
463 if (!pagevec_space(pvec
))
464 __pagevec_lru_add(pvec
, lru
);
465 pagevec_add(pvec
, page
);
466 put_cpu_var(lru_add_pvecs
);
468 EXPORT_SYMBOL(__lru_cache_add
);
471 * lru_cache_add_lru - add a page to a page list
472 * @page: the page to be added to the LRU.
473 * @lru: the LRU list to which the page is added.
475 void lru_cache_add_lru(struct page
*page
, enum lru_list lru
)
477 if (PageActive(page
)) {
478 VM_BUG_ON(PageUnevictable(page
));
479 ClearPageActive(page
);
480 } else if (PageUnevictable(page
)) {
481 VM_BUG_ON(PageActive(page
));
482 ClearPageUnevictable(page
);
485 VM_BUG_ON(PageLRU(page
) || PageActive(page
) || PageUnevictable(page
));
486 __lru_cache_add(page
, lru
);
490 * add_page_to_unevictable_list - add a page to the unevictable list
491 * @page: the page to be added to the unevictable list
493 * Add page directly to its zone's unevictable list. To avoid races with
494 * tasks that might be making the page evictable, through eg. munlock,
495 * munmap or exit, while it's not on the lru, we want to add the page
496 * while it's locked or otherwise "invisible" to other tasks. This is
497 * difficult to do when using the pagevec cache, so bypass that.
499 void add_page_to_unevictable_list(struct page
*page
)
501 struct zone
*zone
= page_zone(page
);
502 struct lruvec
*lruvec
;
504 spin_lock_irq(&zone
->lru_lock
);
505 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
506 SetPageUnevictable(page
);
508 add_page_to_lru_list(page
, lruvec
, LRU_UNEVICTABLE
);
509 spin_unlock_irq(&zone
->lru_lock
);
513 * If the page can not be invalidated, it is moved to the
514 * inactive list to speed up its reclaim. It is moved to the
515 * head of the list, rather than the tail, to give the flusher
516 * threads some time to write it out, as this is much more
517 * effective than the single-page writeout from reclaim.
519 * If the page isn't page_mapped and dirty/writeback, the page
520 * could reclaim asap using PG_reclaim.
522 * 1. active, mapped page -> none
523 * 2. active, dirty/writeback page -> inactive, head, PG_reclaim
524 * 3. inactive, mapped page -> none
525 * 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim
526 * 5. inactive, clean -> inactive, tail
529 * In 4, why it moves inactive's head, the VM expects the page would
530 * be write it out by flusher threads as this is much more effective
531 * than the single-page writeout from reclaim.
533 static void lru_deactivate_fn(struct page
*page
, struct lruvec
*lruvec
,
542 if (PageUnevictable(page
))
545 /* Some processes are using the page */
546 if (page_mapped(page
))
549 active
= PageActive(page
);
550 file
= page_is_file_cache(page
);
551 lru
= page_lru_base_type(page
);
553 del_page_from_lru_list(page
, lruvec
, lru
+ active
);
554 ClearPageActive(page
);
555 ClearPageReferenced(page
);
556 add_page_to_lru_list(page
, lruvec
, lru
);
558 if (PageWriteback(page
) || PageDirty(page
)) {
560 * PG_reclaim could be raced with end_page_writeback
561 * It can make readahead confusing. But race window
562 * is _really_ small and it's non-critical problem.
564 SetPageReclaim(page
);
567 * The page's writeback ends up during pagevec
568 * We moves tha page into tail of inactive.
570 list_move_tail(&page
->lru
, &lruvec
->lists
[lru
]);
571 __count_vm_event(PGROTATED
);
575 __count_vm_event(PGDEACTIVATE
);
576 update_page_reclaim_stat(lruvec
, file
, 0);
580 * Drain pages out of the cpu's pagevecs.
581 * Either "cpu" is the current CPU, and preemption has already been
582 * disabled; or "cpu" is being hot-unplugged, and is already dead.
584 void lru_add_drain_cpu(int cpu
)
586 struct pagevec
*pvecs
= per_cpu(lru_add_pvecs
, cpu
);
587 struct pagevec
*pvec
;
591 pvec
= &pvecs
[lru
- LRU_BASE
];
592 if (pagevec_count(pvec
))
593 __pagevec_lru_add(pvec
, lru
);
596 pvec
= &per_cpu(lru_rotate_pvecs
, cpu
);
597 if (pagevec_count(pvec
)) {
600 /* No harm done if a racing interrupt already did this */
601 local_irq_save(flags
);
602 pagevec_move_tail(pvec
);
603 local_irq_restore(flags
);
606 pvec
= &per_cpu(lru_deactivate_pvecs
, cpu
);
607 if (pagevec_count(pvec
))
608 pagevec_lru_move_fn(pvec
, lru_deactivate_fn
, NULL
);
610 activate_page_drain(cpu
);
614 * deactivate_page - forcefully deactivate a page
615 * @page: page to deactivate
617 * This function hints the VM that @page is a good reclaim candidate,
618 * for example if its invalidation fails due to the page being dirty
619 * or under writeback.
621 void deactivate_page(struct page
*page
)
624 * In a workload with many unevictable page such as mprotect, unevictable
625 * page deactivation for accelerating reclaim is pointless.
627 if (PageUnevictable(page
))
630 if (likely(get_page_unless_zero(page
))) {
631 struct pagevec
*pvec
= &get_cpu_var(lru_deactivate_pvecs
);
633 if (!pagevec_add(pvec
, page
))
634 pagevec_lru_move_fn(pvec
, lru_deactivate_fn
, NULL
);
635 put_cpu_var(lru_deactivate_pvecs
);
639 void lru_add_drain(void)
641 lru_add_drain_cpu(get_cpu());
645 static void lru_add_drain_per_cpu(struct work_struct
*dummy
)
651 * Returns 0 for success
653 int lru_add_drain_all(void)
655 return schedule_on_each_cpu(lru_add_drain_per_cpu
);
659 * Batched page_cache_release(). Decrement the reference count on all the
660 * passed pages. If it fell to zero then remove the page from the LRU and
663 * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
664 * for the remainder of the operation.
666 * The locking in this function is against shrink_inactive_list(): we recheck
667 * the page count inside the lock to see whether shrink_inactive_list()
668 * grabbed the page via the LRU. If it did, give up: shrink_inactive_list()
671 void release_pages(struct page
**pages
, int nr
, int cold
)
674 LIST_HEAD(pages_to_free
);
675 struct zone
*zone
= NULL
;
676 struct lruvec
*lruvec
;
677 unsigned long uninitialized_var(flags
);
679 for (i
= 0; i
< nr
; i
++) {
680 struct page
*page
= pages
[i
];
682 if (unlikely(PageCompound(page
))) {
684 spin_unlock_irqrestore(&zone
->lru_lock
, flags
);
687 put_compound_page(page
);
691 if (!put_page_testzero(page
))
695 struct zone
*pagezone
= page_zone(page
);
697 if (pagezone
!= zone
) {
699 spin_unlock_irqrestore(&zone
->lru_lock
,
702 spin_lock_irqsave(&zone
->lru_lock
, flags
);
705 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
706 VM_BUG_ON(!PageLRU(page
));
707 __ClearPageLRU(page
);
708 del_page_from_lru_list(page
, lruvec
, page_off_lru(page
));
711 list_add(&page
->lru
, &pages_to_free
);
714 spin_unlock_irqrestore(&zone
->lru_lock
, flags
);
716 free_hot_cold_page_list(&pages_to_free
, cold
);
718 EXPORT_SYMBOL(release_pages
);
721 * The pages which we're about to release may be in the deferred lru-addition
722 * queues. That would prevent them from really being freed right now. That's
723 * OK from a correctness point of view but is inefficient - those pages may be
724 * cache-warm and we want to give them back to the page allocator ASAP.
726 * So __pagevec_release() will drain those queues here. __pagevec_lru_add()
727 * and __pagevec_lru_add_active() call release_pages() directly to avoid
730 void __pagevec_release(struct pagevec
*pvec
)
733 release_pages(pvec
->pages
, pagevec_count(pvec
), pvec
->cold
);
734 pagevec_reinit(pvec
);
736 EXPORT_SYMBOL(__pagevec_release
);
738 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
739 /* used by __split_huge_page_refcount() */
740 void lru_add_page_tail(struct page
*page
, struct page
*page_tail
,
741 struct lruvec
*lruvec
, struct list_head
*list
)
743 int uninitialized_var(active
);
747 VM_BUG_ON(!PageHead(page
));
748 VM_BUG_ON(PageCompound(page_tail
));
749 VM_BUG_ON(PageLRU(page_tail
));
750 VM_BUG_ON(NR_CPUS
!= 1 &&
751 !spin_is_locked(&lruvec_zone(lruvec
)->lru_lock
));
754 SetPageLRU(page_tail
);
756 if (page_evictable(page_tail
)) {
757 if (PageActive(page
)) {
758 SetPageActive(page_tail
);
760 lru
= LRU_ACTIVE_ANON
;
763 lru
= LRU_INACTIVE_ANON
;
766 SetPageUnevictable(page_tail
);
767 lru
= LRU_UNEVICTABLE
;
770 if (likely(PageLRU(page
)))
771 list_add_tail(&page_tail
->lru
, &page
->lru
);
773 /* page reclaim is reclaiming a huge page */
775 list_add_tail(&page_tail
->lru
, list
);
777 struct list_head
*list_head
;
779 * Head page has not yet been counted, as an hpage,
780 * so we must account for each subpage individually.
782 * Use the standard add function to put page_tail on the list,
783 * but then correct its position so they all end up in order.
785 add_page_to_lru_list(page_tail
, lruvec
, lru
);
786 list_head
= page_tail
->lru
.prev
;
787 list_move_tail(&page_tail
->lru
, list_head
);
790 if (!PageUnevictable(page
))
791 update_page_reclaim_stat(lruvec
, file
, active
);
793 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
795 static void __pagevec_lru_add_fn(struct page
*page
, struct lruvec
*lruvec
,
798 enum lru_list lru
= (enum lru_list
)arg
;
799 int file
= is_file_lru(lru
);
800 int active
= is_active_lru(lru
);
802 VM_BUG_ON(PageActive(page
));
803 VM_BUG_ON(PageUnevictable(page
));
804 VM_BUG_ON(PageLRU(page
));
809 add_page_to_lru_list(page
, lruvec
, lru
);
810 update_page_reclaim_stat(lruvec
, file
, active
);
814 * Add the passed pages to the LRU, then drop the caller's refcount
815 * on them. Reinitialises the caller's pagevec.
817 void __pagevec_lru_add(struct pagevec
*pvec
, enum lru_list lru
)
819 VM_BUG_ON(is_unevictable_lru(lru
));
821 pagevec_lru_move_fn(pvec
, __pagevec_lru_add_fn
, (void *)lru
);
823 EXPORT_SYMBOL(__pagevec_lru_add
);
826 * pagevec_lookup - gang pagecache lookup
827 * @pvec: Where the resulting pages are placed
828 * @mapping: The address_space to search
829 * @start: The starting page index
830 * @nr_pages: The maximum number of pages
832 * pagevec_lookup() will search for and return a group of up to @nr_pages pages
833 * in the mapping. The pages are placed in @pvec. pagevec_lookup() takes a
834 * reference against the pages in @pvec.
836 * The search returns a group of mapping-contiguous pages with ascending
837 * indexes. There may be holes in the indices due to not-present pages.
839 * pagevec_lookup() returns the number of pages which were found.
841 unsigned pagevec_lookup(struct pagevec
*pvec
, struct address_space
*mapping
,
842 pgoff_t start
, unsigned nr_pages
)
844 pvec
->nr
= find_get_pages(mapping
, start
, nr_pages
, pvec
->pages
);
845 return pagevec_count(pvec
);
847 EXPORT_SYMBOL(pagevec_lookup
);
849 unsigned pagevec_lookup_tag(struct pagevec
*pvec
, struct address_space
*mapping
,
850 pgoff_t
*index
, int tag
, unsigned nr_pages
)
852 pvec
->nr
= find_get_pages_tag(mapping
, index
, tag
,
853 nr_pages
, pvec
->pages
);
854 return pagevec_count(pvec
);
856 EXPORT_SYMBOL(pagevec_lookup_tag
);
859 * Perform any setup for the swap system
861 void __init
swap_setup(void)
863 unsigned long megs
= totalram_pages
>> (20 - PAGE_SHIFT
);
867 bdi_init(swapper_spaces
[0].backing_dev_info
);
868 for (i
= 0; i
< MAX_SWAPFILES
; i
++) {
869 spin_lock_init(&swapper_spaces
[i
].tree_lock
);
870 INIT_LIST_HEAD(&swapper_spaces
[i
].i_mmap_nonlinear
);
874 /* Use a smaller cluster for small-memory machines */
880 * Right now other parts of the system means that we
881 * _really_ don't want to cluster much more