Root/mm/swap.c

1/*
2 * linux/mm/swap.c
3 *
4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
5 */
6
7/*
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.
11 * Started 18.12.91
12 * Swap aging added 23.2.95, Stephen Tweedie.
13 * Buffermem limits added 12.3.98, Rik van Riel.
14 */
15
16#include <linux/mm.h>
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>
34
35#include "internal.h"
36
37#define CREATE_TRACE_POINTS
38#include <trace/events/pagemap.h>
39
40/* How many pages do we try to swap or page in/out together? */
41int page_cluster;
42
43static DEFINE_PER_CPU(struct pagevec, lru_add_pvec);
44static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs);
45static DEFINE_PER_CPU(struct pagevec, lru_deactivate_pvecs);
46
47/*
48 * This path almost never happens for VM activity - pages are normally
49 * freed via pagevecs. But it gets used by networking.
50 */
51static void __page_cache_release(struct page *page)
52{
53    if (PageLRU(page)) {
54        struct zone *zone = page_zone(page);
55        struct lruvec *lruvec;
56        unsigned long flags;
57
58        spin_lock_irqsave(&zone->lru_lock, flags);
59        lruvec = mem_cgroup_page_lruvec(page, zone);
60        VM_BUG_ON(!PageLRU(page));
61        __ClearPageLRU(page);
62        del_page_from_lru_list(page, lruvec, page_off_lru(page));
63        spin_unlock_irqrestore(&zone->lru_lock, flags);
64    }
65}
66
67static void __put_single_page(struct page *page)
68{
69    __page_cache_release(page);
70    free_hot_cold_page(page, 0);
71}
72
73static void __put_compound_page(struct page *page)
74{
75    compound_page_dtor *dtor;
76
77    __page_cache_release(page);
78    dtor = get_compound_page_dtor(page);
79    (*dtor)(page);
80}
81
82static void put_compound_page(struct page *page)
83{
84    if (unlikely(PageTail(page))) {
85        /* __split_huge_page_refcount can run under us */
86        struct page *page_head = compound_trans_head(page);
87
88        if (likely(page != page_head &&
89               get_page_unless_zero(page_head))) {
90            unsigned long flags;
91
92            /*
93             * THP can not break up slab pages so avoid taking
94             * compound_lock(). Slab performs non-atomic bit ops
95             * on page->flags for better performance. In particular
96             * slab_unlock() in slub used to be a hot path. It is
97             * still hot on arches that do not support
98             * this_cpu_cmpxchg_double().
99             */
100            if (PageSlab(page_head)) {
101                if (PageTail(page)) {
102                    if (put_page_testzero(page_head))
103                        VM_BUG_ON(1);
104
105                    atomic_dec(&page->_mapcount);
106                    goto skip_lock_tail;
107                } else
108                    goto skip_lock;
109            }
110            /*
111             * page_head wasn't a dangling pointer but it
112             * may not be a head page anymore by the time
113             * we obtain the lock. That is ok as long as it
114             * can't be freed from under us.
115             */
116            flags = compound_lock_irqsave(page_head);
117            if (unlikely(!PageTail(page))) {
118                /* __split_huge_page_refcount run before us */
119                compound_unlock_irqrestore(page_head, flags);
120skip_lock:
121                if (put_page_testzero(page_head))
122                    __put_single_page(page_head);
123out_put_single:
124                if (put_page_testzero(page))
125                    __put_single_page(page);
126                return;
127            }
128            VM_BUG_ON(page_head != page->first_page);
129            /*
130             * We can release the refcount taken by
131             * get_page_unless_zero() now that
132             * __split_huge_page_refcount() is blocked on
133             * the compound_lock.
134             */
135            if (put_page_testzero(page_head))
136                VM_BUG_ON(1);
137            /* __split_huge_page_refcount will wait now */
138            VM_BUG_ON(page_mapcount(page) <= 0);
139            atomic_dec(&page->_mapcount);
140            VM_BUG_ON(atomic_read(&page_head->_count) <= 0);
141            VM_BUG_ON(atomic_read(&page->_count) != 0);
142            compound_unlock_irqrestore(page_head, flags);
143
144skip_lock_tail:
145            if (put_page_testzero(page_head)) {
146                if (PageHead(page_head))
147                    __put_compound_page(page_head);
148                else
149                    __put_single_page(page_head);
150            }
151        } else {
152            /* page_head is a dangling pointer */
153            VM_BUG_ON(PageTail(page));
154            goto out_put_single;
155        }
156    } else if (put_page_testzero(page)) {
157        if (PageHead(page))
158            __put_compound_page(page);
159        else
160            __put_single_page(page);
161    }
162}
163
164void put_page(struct page *page)
165{
166    if (unlikely(PageCompound(page)))
167        put_compound_page(page);
168    else if (put_page_testzero(page))
169        __put_single_page(page);
170}
171EXPORT_SYMBOL(put_page);
172
173/*
174 * This function is exported but must not be called by anything other
175 * than get_page(). It implements the slow path of get_page().
176 */
177bool __get_page_tail(struct page *page)
178{
179    /*
180     * This takes care of get_page() if run on a tail page
181     * returned by one of the get_user_pages/follow_page variants.
182     * get_user_pages/follow_page itself doesn't need the compound
183     * lock because it runs __get_page_tail_foll() under the
184     * proper PT lock that already serializes against
185     * split_huge_page().
186     */
187    unsigned long flags;
188    bool got = false;
189    struct page *page_head = compound_trans_head(page);
190
191    if (likely(page != page_head && get_page_unless_zero(page_head))) {
192
193        /* Ref to put_compound_page() comment. */
194        if (PageSlab(page_head)) {
195            if (likely(PageTail(page))) {
196                __get_page_tail_foll(page, false);
197                return true;
198            } else {
199                put_page(page_head);
200                return false;
201            }
202        }
203
204        /*
205         * page_head wasn't a dangling pointer but it
206         * may not be a head page anymore by the time
207         * we obtain the lock. That is ok as long as it
208         * can't be freed from under us.
209         */
210        flags = compound_lock_irqsave(page_head);
211        /* here __split_huge_page_refcount won't run anymore */
212        if (likely(PageTail(page))) {
213            __get_page_tail_foll(page, false);
214            got = true;
215        }
216        compound_unlock_irqrestore(page_head, flags);
217        if (unlikely(!got))
218            put_page(page_head);
219    }
220    return got;
221}
222EXPORT_SYMBOL(__get_page_tail);
223
224/**
225 * put_pages_list() - release a list of pages
226 * @pages: list of pages threaded on page->lru
227 *
228 * Release a list of pages which are strung together on page.lru. Currently
229 * used by read_cache_pages() and related error recovery code.
230 */
231void put_pages_list(struct list_head *pages)
232{
233    while (!list_empty(pages)) {
234        struct page *victim;
235
236        victim = list_entry(pages->prev, struct page, lru);
237        list_del(&victim->lru);
238        page_cache_release(victim);
239    }
240}
241EXPORT_SYMBOL(put_pages_list);
242
243/*
244 * get_kernel_pages() - pin kernel pages in memory
245 * @kiov: An array of struct kvec structures
246 * @nr_segs: number of segments to pin
247 * @write: pinning for read/write, currently ignored
248 * @pages: array that receives pointers to the pages pinned.
249 * Should be at least nr_segs long.
250 *
251 * Returns number of pages pinned. This may be fewer than the number
252 * requested. If nr_pages is 0 or negative, returns 0. If no pages
253 * were pinned, returns -errno. Each page returned must be released
254 * with a put_page() call when it is finished with.
255 */
256int get_kernel_pages(const struct kvec *kiov, int nr_segs, int write,
257        struct page **pages)
258{
259    int seg;
260
261    for (seg = 0; seg < nr_segs; seg++) {
262        if (WARN_ON(kiov[seg].iov_len != PAGE_SIZE))
263            return seg;
264
265        pages[seg] = kmap_to_page(kiov[seg].iov_base);
266        page_cache_get(pages[seg]);
267    }
268
269    return seg;
270}
271EXPORT_SYMBOL_GPL(get_kernel_pages);
272
273/*
274 * get_kernel_page() - pin a kernel page in memory
275 * @start: starting kernel address
276 * @write: pinning for read/write, currently ignored
277 * @pages: array that receives pointer to the page pinned.
278 * Must be at least nr_segs long.
279 *
280 * Returns 1 if page is pinned. If the page was not pinned, returns
281 * -errno. The page returned must be released with a put_page() call
282 * when it is finished with.
283 */
284int get_kernel_page(unsigned long start, int write, struct page **pages)
285{
286    const struct kvec kiov = {
287        .iov_base = (void *)start,
288        .iov_len = PAGE_SIZE
289    };
290
291    return get_kernel_pages(&kiov, 1, write, pages);
292}
293EXPORT_SYMBOL_GPL(get_kernel_page);
294
295static void pagevec_lru_move_fn(struct pagevec *pvec,
296    void (*move_fn)(struct page *page, struct lruvec *lruvec, void *arg),
297    void *arg)
298{
299    int i;
300    struct zone *zone = NULL;
301    struct lruvec *lruvec;
302    unsigned long flags = 0;
303
304    for (i = 0; i < pagevec_count(pvec); i++) {
305        struct page *page = pvec->pages[i];
306        struct zone *pagezone = page_zone(page);
307
308        if (pagezone != zone) {
309            if (zone)
310                spin_unlock_irqrestore(&zone->lru_lock, flags);
311            zone = pagezone;
312            spin_lock_irqsave(&zone->lru_lock, flags);
313        }
314
315        lruvec = mem_cgroup_page_lruvec(page, zone);
316        (*move_fn)(page, lruvec, arg);
317    }
318    if (zone)
319        spin_unlock_irqrestore(&zone->lru_lock, flags);
320    release_pages(pvec->pages, pvec->nr, pvec->cold);
321    pagevec_reinit(pvec);
322}
323
324static void pagevec_move_tail_fn(struct page *page, struct lruvec *lruvec,
325                 void *arg)
326{
327    int *pgmoved = arg;
328
329    if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
330        enum lru_list lru = page_lru_base_type(page);
331        list_move_tail(&page->lru, &lruvec->lists[lru]);
332        (*pgmoved)++;
333    }
334}
335
336/*
337 * pagevec_move_tail() must be called with IRQ disabled.
338 * Otherwise this may cause nasty races.
339 */
340static void pagevec_move_tail(struct pagevec *pvec)
341{
342    int pgmoved = 0;
343
344    pagevec_lru_move_fn(pvec, pagevec_move_tail_fn, &pgmoved);
345    __count_vm_events(PGROTATED, pgmoved);
346}
347
348/*
349 * Writeback is about to end against a page which has been marked for immediate
350 * reclaim. If it still appears to be reclaimable, move it to the tail of the
351 * inactive list.
352 */
353void rotate_reclaimable_page(struct page *page)
354{
355    if (!PageLocked(page) && !PageDirty(page) && !PageActive(page) &&
356        !PageUnevictable(page) && PageLRU(page)) {
357        struct pagevec *pvec;
358        unsigned long flags;
359
360        page_cache_get(page);
361        local_irq_save(flags);
362        pvec = &__get_cpu_var(lru_rotate_pvecs);
363        if (!pagevec_add(pvec, page))
364            pagevec_move_tail(pvec);
365        local_irq_restore(flags);
366    }
367}
368
369static void update_page_reclaim_stat(struct lruvec *lruvec,
370                     int file, int rotated)
371{
372    struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
373
374    reclaim_stat->recent_scanned[file]++;
375    if (rotated)
376        reclaim_stat->recent_rotated[file]++;
377}
378
379static void __activate_page(struct page *page, struct lruvec *lruvec,
380                void *arg)
381{
382    if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
383        int file = page_is_file_cache(page);
384        int lru = page_lru_base_type(page);
385
386        del_page_from_lru_list(page, lruvec, lru);
387        SetPageActive(page);
388        lru += LRU_ACTIVE;
389        add_page_to_lru_list(page, lruvec, lru);
390        trace_mm_lru_activate(page, page_to_pfn(page));
391
392        __count_vm_event(PGACTIVATE);
393        update_page_reclaim_stat(lruvec, file, 1);
394    }
395}
396
397#ifdef CONFIG_SMP
398static DEFINE_PER_CPU(struct pagevec, activate_page_pvecs);
399
400static void activate_page_drain(int cpu)
401{
402    struct pagevec *pvec = &per_cpu(activate_page_pvecs, cpu);
403
404    if (pagevec_count(pvec))
405        pagevec_lru_move_fn(pvec, __activate_page, NULL);
406}
407
408void activate_page(struct page *page)
409{
410    if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
411        struct pagevec *pvec = &get_cpu_var(activate_page_pvecs);
412
413        page_cache_get(page);
414        if (!pagevec_add(pvec, page))
415            pagevec_lru_move_fn(pvec, __activate_page, NULL);
416        put_cpu_var(activate_page_pvecs);
417    }
418}
419
420#else
421static inline void activate_page_drain(int cpu)
422{
423}
424
425void activate_page(struct page *page)
426{
427    struct zone *zone = page_zone(page);
428
429    spin_lock_irq(&zone->lru_lock);
430    __activate_page(page, mem_cgroup_page_lruvec(page, zone), NULL);
431    spin_unlock_irq(&zone->lru_lock);
432}
433#endif
434
435static void __lru_cache_activate_page(struct page *page)
436{
437    struct pagevec *pvec = &get_cpu_var(lru_add_pvec);
438    int i;
439
440    /*
441     * Search backwards on the optimistic assumption that the page being
442     * activated has just been added to this pagevec. Note that only
443     * the local pagevec is examined as a !PageLRU page could be in the
444     * process of being released, reclaimed, migrated or on a remote
445     * pagevec that is currently being drained. Furthermore, marking
446     * a remote pagevec's page PageActive potentially hits a race where
447     * a page is marked PageActive just after it is added to the inactive
448     * list causing accounting errors and BUG_ON checks to trigger.
449     */
450    for (i = pagevec_count(pvec) - 1; i >= 0; i--) {
451        struct page *pagevec_page = pvec->pages[i];
452
453        if (pagevec_page == page) {
454            SetPageActive(page);
455            break;
456        }
457    }
458
459    put_cpu_var(lru_add_pvec);
460}
461
462/*
463 * Mark a page as having seen activity.
464 *
465 * inactive,unreferenced -> inactive,referenced
466 * inactive,referenced -> active,unreferenced
467 * active,unreferenced -> active,referenced
468 */
469void mark_page_accessed(struct page *page)
470{
471    if (!PageActive(page) && !PageUnevictable(page) &&
472            PageReferenced(page)) {
473
474        /*
475         * If the page is on the LRU, queue it for activation via
476         * activate_page_pvecs. Otherwise, assume the page is on a
477         * pagevec, mark it active and it'll be moved to the active
478         * LRU on the next drain.
479         */
480        if (PageLRU(page))
481            activate_page(page);
482        else
483            __lru_cache_activate_page(page);
484        ClearPageReferenced(page);
485    } else if (!PageReferenced(page)) {
486        SetPageReferenced(page);
487    }
488}
489EXPORT_SYMBOL(mark_page_accessed);
490
491/*
492 * Queue the page for addition to the LRU via pagevec. The decision on whether
493 * to add the page to the [in]active [file|anon] list is deferred until the
494 * pagevec is drained. This gives a chance for the caller of __lru_cache_add()
495 * have the page added to the active list using mark_page_accessed().
496 */
497void __lru_cache_add(struct page *page)
498{
499    struct pagevec *pvec = &get_cpu_var(lru_add_pvec);
500
501    page_cache_get(page);
502    if (!pagevec_space(pvec))
503        __pagevec_lru_add(pvec);
504    pagevec_add(pvec, page);
505    put_cpu_var(lru_add_pvec);
506}
507EXPORT_SYMBOL(__lru_cache_add);
508
509/**
510 * lru_cache_add - add a page to a page list
511 * @page: the page to be added to the LRU.
512 */
513void lru_cache_add(struct page *page)
514{
515    VM_BUG_ON(PageActive(page) && PageUnevictable(page));
516    VM_BUG_ON(PageLRU(page));
517    __lru_cache_add(page);
518}
519
520/**
521 * add_page_to_unevictable_list - add a page to the unevictable list
522 * @page: the page to be added to the unevictable list
523 *
524 * Add page directly to its zone's unevictable list. To avoid races with
525 * tasks that might be making the page evictable, through eg. munlock,
526 * munmap or exit, while it's not on the lru, we want to add the page
527 * while it's locked or otherwise "invisible" to other tasks. This is
528 * difficult to do when using the pagevec cache, so bypass that.
529 */
530void add_page_to_unevictable_list(struct page *page)
531{
532    struct zone *zone = page_zone(page);
533    struct lruvec *lruvec;
534
535    spin_lock_irq(&zone->lru_lock);
536    lruvec = mem_cgroup_page_lruvec(page, zone);
537    ClearPageActive(page);
538    SetPageUnevictable(page);
539    SetPageLRU(page);
540    add_page_to_lru_list(page, lruvec, LRU_UNEVICTABLE);
541    spin_unlock_irq(&zone->lru_lock);
542}
543
544/*
545 * If the page can not be invalidated, it is moved to the
546 * inactive list to speed up its reclaim. It is moved to the
547 * head of the list, rather than the tail, to give the flusher
548 * threads some time to write it out, as this is much more
549 * effective than the single-page writeout from reclaim.
550 *
551 * If the page isn't page_mapped and dirty/writeback, the page
552 * could reclaim asap using PG_reclaim.
553 *
554 * 1. active, mapped page -> none
555 * 2. active, dirty/writeback page -> inactive, head, PG_reclaim
556 * 3. inactive, mapped page -> none
557 * 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim
558 * 5. inactive, clean -> inactive, tail
559 * 6. Others -> none
560 *
561 * In 4, why it moves inactive's head, the VM expects the page would
562 * be write it out by flusher threads as this is much more effective
563 * than the single-page writeout from reclaim.
564 */
565static void lru_deactivate_fn(struct page *page, struct lruvec *lruvec,
566                  void *arg)
567{
568    int lru, file;
569    bool active;
570
571    if (!PageLRU(page))
572        return;
573
574    if (PageUnevictable(page))
575        return;
576
577    /* Some processes are using the page */
578    if (page_mapped(page))
579        return;
580
581    active = PageActive(page);
582    file = page_is_file_cache(page);
583    lru = page_lru_base_type(page);
584
585    del_page_from_lru_list(page, lruvec, lru + active);
586    ClearPageActive(page);
587    ClearPageReferenced(page);
588    add_page_to_lru_list(page, lruvec, lru);
589
590    if (PageWriteback(page) || PageDirty(page)) {
591        /*
592         * PG_reclaim could be raced with end_page_writeback
593         * It can make readahead confusing. But race window
594         * is _really_ small and it's non-critical problem.
595         */
596        SetPageReclaim(page);
597    } else {
598        /*
599         * The page's writeback ends up during pagevec
600         * We moves tha page into tail of inactive.
601         */
602        list_move_tail(&page->lru, &lruvec->lists[lru]);
603        __count_vm_event(PGROTATED);
604    }
605
606    if (active)
607        __count_vm_event(PGDEACTIVATE);
608    update_page_reclaim_stat(lruvec, file, 0);
609}
610
611/*
612 * Drain pages out of the cpu's pagevecs.
613 * Either "cpu" is the current CPU, and preemption has already been
614 * disabled; or "cpu" is being hot-unplugged, and is already dead.
615 */
616void lru_add_drain_cpu(int cpu)
617{
618    struct pagevec *pvec = &per_cpu(lru_add_pvec, cpu);
619
620    if (pagevec_count(pvec))
621        __pagevec_lru_add(pvec);
622
623    pvec = &per_cpu(lru_rotate_pvecs, cpu);
624    if (pagevec_count(pvec)) {
625        unsigned long flags;
626
627        /* No harm done if a racing interrupt already did this */
628        local_irq_save(flags);
629        pagevec_move_tail(pvec);
630        local_irq_restore(flags);
631    }
632
633    pvec = &per_cpu(lru_deactivate_pvecs, cpu);
634    if (pagevec_count(pvec))
635        pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
636
637    activate_page_drain(cpu);
638}
639
640/**
641 * deactivate_page - forcefully deactivate a page
642 * @page: page to deactivate
643 *
644 * This function hints the VM that @page is a good reclaim candidate,
645 * for example if its invalidation fails due to the page being dirty
646 * or under writeback.
647 */
648void deactivate_page(struct page *page)
649{
650    /*
651     * In a workload with many unevictable page such as mprotect, unevictable
652     * page deactivation for accelerating reclaim is pointless.
653     */
654    if (PageUnevictable(page))
655        return;
656
657    if (likely(get_page_unless_zero(page))) {
658        struct pagevec *pvec = &get_cpu_var(lru_deactivate_pvecs);
659
660        if (!pagevec_add(pvec, page))
661            pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
662        put_cpu_var(lru_deactivate_pvecs);
663    }
664}
665
666void lru_add_drain(void)
667{
668    lru_add_drain_cpu(get_cpu());
669    put_cpu();
670}
671
672static void lru_add_drain_per_cpu(struct work_struct *dummy)
673{
674    lru_add_drain();
675}
676
677/*
678 * Returns 0 for success
679 */
680int lru_add_drain_all(void)
681{
682    return schedule_on_each_cpu(lru_add_drain_per_cpu);
683}
684
685/*
686 * Batched page_cache_release(). Decrement the reference count on all the
687 * passed pages. If it fell to zero then remove the page from the LRU and
688 * free it.
689 *
690 * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
691 * for the remainder of the operation.
692 *
693 * The locking in this function is against shrink_inactive_list(): we recheck
694 * the page count inside the lock to see whether shrink_inactive_list()
695 * grabbed the page via the LRU. If it did, give up: shrink_inactive_list()
696 * will free it.
697 */
698void release_pages(struct page **pages, int nr, int cold)
699{
700    int i;
701    LIST_HEAD(pages_to_free);
702    struct zone *zone = NULL;
703    struct lruvec *lruvec;
704    unsigned long uninitialized_var(flags);
705
706    for (i = 0; i < nr; i++) {
707        struct page *page = pages[i];
708
709        if (unlikely(PageCompound(page))) {
710            if (zone) {
711                spin_unlock_irqrestore(&zone->lru_lock, flags);
712                zone = NULL;
713            }
714            put_compound_page(page);
715            continue;
716        }
717
718        if (!put_page_testzero(page))
719            continue;
720
721        if (PageLRU(page)) {
722            struct zone *pagezone = page_zone(page);
723
724            if (pagezone != zone) {
725                if (zone)
726                    spin_unlock_irqrestore(&zone->lru_lock,
727                                    flags);
728                zone = pagezone;
729                spin_lock_irqsave(&zone->lru_lock, flags);
730            }
731
732            lruvec = mem_cgroup_page_lruvec(page, zone);
733            VM_BUG_ON(!PageLRU(page));
734            __ClearPageLRU(page);
735            del_page_from_lru_list(page, lruvec, page_off_lru(page));
736        }
737
738        /* Clear Active bit in case of parallel mark_page_accessed */
739        ClearPageActive(page);
740
741        list_add(&page->lru, &pages_to_free);
742    }
743    if (zone)
744        spin_unlock_irqrestore(&zone->lru_lock, flags);
745
746    free_hot_cold_page_list(&pages_to_free, cold);
747}
748EXPORT_SYMBOL(release_pages);
749
750/*
751 * The pages which we're about to release may be in the deferred lru-addition
752 * queues. That would prevent them from really being freed right now. That's
753 * OK from a correctness point of view but is inefficient - those pages may be
754 * cache-warm and we want to give them back to the page allocator ASAP.
755 *
756 * So __pagevec_release() will drain those queues here. __pagevec_lru_add()
757 * and __pagevec_lru_add_active() call release_pages() directly to avoid
758 * mutual recursion.
759 */
760void __pagevec_release(struct pagevec *pvec)
761{
762    lru_add_drain();
763    release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
764    pagevec_reinit(pvec);
765}
766EXPORT_SYMBOL(__pagevec_release);
767
768#ifdef CONFIG_TRANSPARENT_HUGEPAGE
769/* used by __split_huge_page_refcount() */
770void lru_add_page_tail(struct page *page, struct page *page_tail,
771               struct lruvec *lruvec, struct list_head *list)
772{
773    const int file = 0;
774
775    VM_BUG_ON(!PageHead(page));
776    VM_BUG_ON(PageCompound(page_tail));
777    VM_BUG_ON(PageLRU(page_tail));
778    VM_BUG_ON(NR_CPUS != 1 &&
779          !spin_is_locked(&lruvec_zone(lruvec)->lru_lock));
780
781    if (!list)
782        SetPageLRU(page_tail);
783
784    if (likely(PageLRU(page)))
785        list_add_tail(&page_tail->lru, &page->lru);
786    else if (list) {
787        /* page reclaim is reclaiming a huge page */
788        get_page(page_tail);
789        list_add_tail(&page_tail->lru, list);
790    } else {
791        struct list_head *list_head;
792        /*
793         * Head page has not yet been counted, as an hpage,
794         * so we must account for each subpage individually.
795         *
796         * Use the standard add function to put page_tail on the list,
797         * but then correct its position so they all end up in order.
798         */
799        add_page_to_lru_list(page_tail, lruvec, page_lru(page_tail));
800        list_head = page_tail->lru.prev;
801        list_move_tail(&page_tail->lru, list_head);
802    }
803
804    if (!PageUnevictable(page))
805        update_page_reclaim_stat(lruvec, file, PageActive(page_tail));
806}
807#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
808
809static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec,
810                 void *arg)
811{
812    int file = page_is_file_cache(page);
813    int active = PageActive(page);
814    enum lru_list lru = page_lru(page);
815
816    VM_BUG_ON(PageLRU(page));
817
818    SetPageLRU(page);
819    add_page_to_lru_list(page, lruvec, lru);
820    update_page_reclaim_stat(lruvec, file, active);
821    trace_mm_lru_insertion(page, page_to_pfn(page), lru, trace_pagemap_flags(page));
822}
823
824/*
825 * Add the passed pages to the LRU, then drop the caller's refcount
826 * on them. Reinitialises the caller's pagevec.
827 */
828void __pagevec_lru_add(struct pagevec *pvec)
829{
830    pagevec_lru_move_fn(pvec, __pagevec_lru_add_fn, NULL);
831}
832EXPORT_SYMBOL(__pagevec_lru_add);
833
834/**
835 * pagevec_lookup - gang pagecache lookup
836 * @pvec: Where the resulting pages are placed
837 * @mapping: The address_space to search
838 * @start: The starting page index
839 * @nr_pages: The maximum number of pages
840 *
841 * pagevec_lookup() will search for and return a group of up to @nr_pages pages
842 * in the mapping. The pages are placed in @pvec. pagevec_lookup() takes a
843 * reference against the pages in @pvec.
844 *
845 * The search returns a group of mapping-contiguous pages with ascending
846 * indexes. There may be holes in the indices due to not-present pages.
847 *
848 * pagevec_lookup() returns the number of pages which were found.
849 */
850unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
851        pgoff_t start, unsigned nr_pages)
852{
853    pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
854    return pagevec_count(pvec);
855}
856EXPORT_SYMBOL(pagevec_lookup);
857
858unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping,
859        pgoff_t *index, int tag, unsigned nr_pages)
860{
861    pvec->nr = find_get_pages_tag(mapping, index, tag,
862                    nr_pages, pvec->pages);
863    return pagevec_count(pvec);
864}
865EXPORT_SYMBOL(pagevec_lookup_tag);
866
867/*
868 * Perform any setup for the swap system
869 */
870void __init swap_setup(void)
871{
872    unsigned long megs = totalram_pages >> (20 - PAGE_SHIFT);
873#ifdef CONFIG_SWAP
874    int i;
875
876    bdi_init(swapper_spaces[0].backing_dev_info);
877    for (i = 0; i < MAX_SWAPFILES; i++) {
878        spin_lock_init(&swapper_spaces[i].tree_lock);
879        INIT_LIST_HEAD(&swapper_spaces[i].i_mmap_nonlinear);
880    }
881#endif
882
883    /* Use a smaller cluster for small-memory machines */
884    if (megs < 16)
885        page_cluster = 2;
886    else
887        page_cluster = 3;
888    /*
889     * Right now other parts of the system means that we
890     * _really_ don't want to cluster much more
891     */
892}
893

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