Root/mm/migrate.c

1/*
2 * Memory Migration functionality - linux/mm/migration.c
3 *
4 * Copyright (C) 2006 Silicon Graphics, Inc., Christoph Lameter
5 *
6 * Page migration was first developed in the context of the memory hotplug
7 * project. The main authors of the migration code are:
8 *
9 * IWAMOTO Toshihiro <iwamoto@valinux.co.jp>
10 * Hirokazu Takahashi <taka@valinux.co.jp>
11 * Dave Hansen <haveblue@us.ibm.com>
12 * Christoph Lameter
13 */
14
15#include <linux/migrate.h>
16#include <linux/module.h>
17#include <linux/swap.h>
18#include <linux/swapops.h>
19#include <linux/pagemap.h>
20#include <linux/buffer_head.h>
21#include <linux/mm_inline.h>
22#include <linux/nsproxy.h>
23#include <linux/pagevec.h>
24#include <linux/ksm.h>
25#include <linux/rmap.h>
26#include <linux/topology.h>
27#include <linux/cpu.h>
28#include <linux/cpuset.h>
29#include <linux/writeback.h>
30#include <linux/mempolicy.h>
31#include <linux/vmalloc.h>
32#include <linux/security.h>
33#include <linux/memcontrol.h>
34#include <linux/syscalls.h>
35#include <linux/gfp.h>
36
37#include "internal.h"
38
39#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
40
41/*
42 * migrate_prep() needs to be called before we start compiling a list of pages
43 * to be migrated using isolate_lru_page(). If scheduling work on other CPUs is
44 * undesirable, use migrate_prep_local()
45 */
46int migrate_prep(void)
47{
48    /*
49     * Clear the LRU lists so pages can be isolated.
50     * Note that pages may be moved off the LRU after we have
51     * drained them. Those pages will fail to migrate like other
52     * pages that may be busy.
53     */
54    lru_add_drain_all();
55
56    return 0;
57}
58
59/* Do the necessary work of migrate_prep but not if it involves other CPUs */
60int migrate_prep_local(void)
61{
62    lru_add_drain();
63
64    return 0;
65}
66
67/*
68 * Add isolated pages on the list back to the LRU under page lock
69 * to avoid leaking evictable pages back onto unevictable list.
70 */
71void putback_lru_pages(struct list_head *l)
72{
73    struct page *page;
74    struct page *page2;
75
76    list_for_each_entry_safe(page, page2, l, lru) {
77        list_del(&page->lru);
78        dec_zone_page_state(page, NR_ISOLATED_ANON +
79                page_is_file_cache(page));
80        putback_lru_page(page);
81    }
82}
83
84/*
85 * Restore a potential migration pte to a working pte entry
86 */
87static int remove_migration_pte(struct page *new, struct vm_area_struct *vma,
88                 unsigned long addr, void *old)
89{
90    struct mm_struct *mm = vma->vm_mm;
91    swp_entry_t entry;
92     pgd_t *pgd;
93     pud_t *pud;
94     pmd_t *pmd;
95    pte_t *ptep, pte;
96     spinlock_t *ptl;
97
98     pgd = pgd_offset(mm, addr);
99    if (!pgd_present(*pgd))
100        goto out;
101
102    pud = pud_offset(pgd, addr);
103    if (!pud_present(*pud))
104        goto out;
105
106    pmd = pmd_offset(pud, addr);
107    if (!pmd_present(*pmd))
108        goto out;
109
110    ptep = pte_offset_map(pmd, addr);
111
112    if (!is_swap_pte(*ptep)) {
113        pte_unmap(ptep);
114        goto out;
115     }
116
117     ptl = pte_lockptr(mm, pmd);
118     spin_lock(ptl);
119    pte = *ptep;
120    if (!is_swap_pte(pte))
121        goto unlock;
122
123    entry = pte_to_swp_entry(pte);
124
125    if (!is_migration_entry(entry) ||
126        migration_entry_to_page(entry) != old)
127        goto unlock;
128
129    get_page(new);
130    pte = pte_mkold(mk_pte(new, vma->vm_page_prot));
131    if (is_write_migration_entry(entry))
132        pte = pte_mkwrite(pte);
133    flush_cache_page(vma, addr, pte_pfn(pte));
134    set_pte_at(mm, addr, ptep, pte);
135
136    if (PageAnon(new))
137        page_add_anon_rmap(new, vma, addr);
138    else
139        page_add_file_rmap(new);
140
141    /* No need to invalidate - it was non-present before */
142    update_mmu_cache(vma, addr, ptep);
143unlock:
144    pte_unmap_unlock(ptep, ptl);
145out:
146    return SWAP_AGAIN;
147}
148
149/*
150 * Get rid of all migration entries and replace them by
151 * references to the indicated page.
152 */
153static void remove_migration_ptes(struct page *old, struct page *new)
154{
155    rmap_walk(new, remove_migration_pte, old);
156}
157
158/*
159 * Something used the pte of a page under migration. We need to
160 * get to the page and wait until migration is finished.
161 * When we return from this function the fault will be retried.
162 *
163 * This function is called from do_swap_page().
164 */
165void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
166                unsigned long address)
167{
168    pte_t *ptep, pte;
169    spinlock_t *ptl;
170    swp_entry_t entry;
171    struct page *page;
172
173    ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
174    pte = *ptep;
175    if (!is_swap_pte(pte))
176        goto out;
177
178    entry = pte_to_swp_entry(pte);
179    if (!is_migration_entry(entry))
180        goto out;
181
182    page = migration_entry_to_page(entry);
183
184    /*
185     * Once radix-tree replacement of page migration started, page_count
186     * *must* be zero. And, we don't want to call wait_on_page_locked()
187     * against a page without get_page().
188     * So, we use get_page_unless_zero(), here. Even failed, page fault
189     * will occur again.
190     */
191    if (!get_page_unless_zero(page))
192        goto out;
193    pte_unmap_unlock(ptep, ptl);
194    wait_on_page_locked(page);
195    put_page(page);
196    return;
197out:
198    pte_unmap_unlock(ptep, ptl);
199}
200
201/*
202 * Replace the page in the mapping.
203 *
204 * The number of remaining references must be:
205 * 1 for anonymous pages without a mapping
206 * 2 for pages with a mapping
207 * 3 for pages with a mapping and PagePrivate/PagePrivate2 set.
208 */
209static int migrate_page_move_mapping(struct address_space *mapping,
210        struct page *newpage, struct page *page)
211{
212    int expected_count;
213    void **pslot;
214
215    if (!mapping) {
216        /* Anonymous page without mapping */
217        if (page_count(page) != 1)
218            return -EAGAIN;
219        return 0;
220    }
221
222    spin_lock_irq(&mapping->tree_lock);
223
224    pslot = radix_tree_lookup_slot(&mapping->page_tree,
225                     page_index(page));
226
227    expected_count = 2 + page_has_private(page);
228    if (page_count(page) != expected_count ||
229            (struct page *)radix_tree_deref_slot(pslot) != page) {
230        spin_unlock_irq(&mapping->tree_lock);
231        return -EAGAIN;
232    }
233
234    if (!page_freeze_refs(page, expected_count)) {
235        spin_unlock_irq(&mapping->tree_lock);
236        return -EAGAIN;
237    }
238
239    /*
240     * Now we know that no one else is looking at the page.
241     */
242    get_page(newpage); /* add cache reference */
243    if (PageSwapCache(page)) {
244        SetPageSwapCache(newpage);
245        set_page_private(newpage, page_private(page));
246    }
247
248    radix_tree_replace_slot(pslot, newpage);
249
250    page_unfreeze_refs(page, expected_count);
251    /*
252     * Drop cache reference from old page.
253     * We know this isn't the last reference.
254     */
255    __put_page(page);
256
257    /*
258     * If moved to a different zone then also account
259     * the page for that zone. Other VM counters will be
260     * taken care of when we establish references to the
261     * new page and drop references to the old page.
262     *
263     * Note that anonymous pages are accounted for
264     * via NR_FILE_PAGES and NR_ANON_PAGES if they
265     * are mapped to swap space.
266     */
267    __dec_zone_page_state(page, NR_FILE_PAGES);
268    __inc_zone_page_state(newpage, NR_FILE_PAGES);
269    if (PageSwapBacked(page)) {
270        __dec_zone_page_state(page, NR_SHMEM);
271        __inc_zone_page_state(newpage, NR_SHMEM);
272    }
273    spin_unlock_irq(&mapping->tree_lock);
274
275    return 0;
276}
277
278/*
279 * Copy the page to its new location
280 */
281static void migrate_page_copy(struct page *newpage, struct page *page)
282{
283    copy_highpage(newpage, page);
284
285    if (PageError(page))
286        SetPageError(newpage);
287    if (PageReferenced(page))
288        SetPageReferenced(newpage);
289    if (PageUptodate(page))
290        SetPageUptodate(newpage);
291    if (TestClearPageActive(page)) {
292        VM_BUG_ON(PageUnevictable(page));
293        SetPageActive(newpage);
294    } else if (TestClearPageUnevictable(page))
295        SetPageUnevictable(newpage);
296    if (PageChecked(page))
297        SetPageChecked(newpage);
298    if (PageMappedToDisk(page))
299        SetPageMappedToDisk(newpage);
300
301    if (PageDirty(page)) {
302        clear_page_dirty_for_io(page);
303        /*
304         * Want to mark the page and the radix tree as dirty, and
305         * redo the accounting that clear_page_dirty_for_io undid,
306         * but we can't use set_page_dirty because that function
307         * is actually a signal that all of the page has become dirty.
308         * Wheras only part of our page may be dirty.
309         */
310        __set_page_dirty_nobuffers(newpage);
311     }
312
313    mlock_migrate_page(newpage, page);
314    ksm_migrate_page(newpage, page);
315
316    ClearPageSwapCache(page);
317    ClearPagePrivate(page);
318    set_page_private(page, 0);
319    page->mapping = NULL;
320
321    /*
322     * If any waiters have accumulated on the new page then
323     * wake them up.
324     */
325    if (PageWriteback(newpage))
326        end_page_writeback(newpage);
327}
328
329/************************************************************
330 * Migration functions
331 ***********************************************************/
332
333/* Always fail migration. Used for mappings that are not movable */
334int fail_migrate_page(struct address_space *mapping,
335            struct page *newpage, struct page *page)
336{
337    return -EIO;
338}
339EXPORT_SYMBOL(fail_migrate_page);
340
341/*
342 * Common logic to directly migrate a single page suitable for
343 * pages that do not use PagePrivate/PagePrivate2.
344 *
345 * Pages are locked upon entry and exit.
346 */
347int migrate_page(struct address_space *mapping,
348        struct page *newpage, struct page *page)
349{
350    int rc;
351
352    BUG_ON(PageWriteback(page)); /* Writeback must be complete */
353
354    rc = migrate_page_move_mapping(mapping, newpage, page);
355
356    if (rc)
357        return rc;
358
359    migrate_page_copy(newpage, page);
360    return 0;
361}
362EXPORT_SYMBOL(migrate_page);
363
364#ifdef CONFIG_BLOCK
365/*
366 * Migration function for pages with buffers. This function can only be used
367 * if the underlying filesystem guarantees that no other references to "page"
368 * exist.
369 */
370int buffer_migrate_page(struct address_space *mapping,
371        struct page *newpage, struct page *page)
372{
373    struct buffer_head *bh, *head;
374    int rc;
375
376    if (!page_has_buffers(page))
377        return migrate_page(mapping, newpage, page);
378
379    head = page_buffers(page);
380
381    rc = migrate_page_move_mapping(mapping, newpage, page);
382
383    if (rc)
384        return rc;
385
386    bh = head;
387    do {
388        get_bh(bh);
389        lock_buffer(bh);
390        bh = bh->b_this_page;
391
392    } while (bh != head);
393
394    ClearPagePrivate(page);
395    set_page_private(newpage, page_private(page));
396    set_page_private(page, 0);
397    put_page(page);
398    get_page(newpage);
399
400    bh = head;
401    do {
402        set_bh_page(bh, newpage, bh_offset(bh));
403        bh = bh->b_this_page;
404
405    } while (bh != head);
406
407    SetPagePrivate(newpage);
408
409    migrate_page_copy(newpage, page);
410
411    bh = head;
412    do {
413        unlock_buffer(bh);
414         put_bh(bh);
415        bh = bh->b_this_page;
416
417    } while (bh != head);
418
419    return 0;
420}
421EXPORT_SYMBOL(buffer_migrate_page);
422#endif
423
424/*
425 * Writeback a page to clean the dirty state
426 */
427static int writeout(struct address_space *mapping, struct page *page)
428{
429    struct writeback_control wbc = {
430        .sync_mode = WB_SYNC_NONE,
431        .nr_to_write = 1,
432        .range_start = 0,
433        .range_end = LLONG_MAX,
434        .nonblocking = 1,
435        .for_reclaim = 1
436    };
437    int rc;
438
439    if (!mapping->a_ops->writepage)
440        /* No write method for the address space */
441        return -EINVAL;
442
443    if (!clear_page_dirty_for_io(page))
444        /* Someone else already triggered a write */
445        return -EAGAIN;
446
447    /*
448     * A dirty page may imply that the underlying filesystem has
449     * the page on some queue. So the page must be clean for
450     * migration. Writeout may mean we loose the lock and the
451     * page state is no longer what we checked for earlier.
452     * At this point we know that the migration attempt cannot
453     * be successful.
454     */
455    remove_migration_ptes(page, page);
456
457    rc = mapping->a_ops->writepage(page, &wbc);
458
459    if (rc != AOP_WRITEPAGE_ACTIVATE)
460        /* unlocked. Relock */
461        lock_page(page);
462
463    return (rc < 0) ? -EIO : -EAGAIN;
464}
465
466/*
467 * Default handling if a filesystem does not provide a migration function.
468 */
469static int fallback_migrate_page(struct address_space *mapping,
470    struct page *newpage, struct page *page)
471{
472    if (PageDirty(page))
473        return writeout(mapping, page);
474
475    /*
476     * Buffers may be managed in a filesystem specific way.
477     * We must have no buffers or drop them.
478     */
479    if (page_has_private(page) &&
480        !try_to_release_page(page, GFP_KERNEL))
481        return -EAGAIN;
482
483    return migrate_page(mapping, newpage, page);
484}
485
486/*
487 * Move a page to a newly allocated page
488 * The page is locked and all ptes have been successfully removed.
489 *
490 * The new page will have replaced the old page if this function
491 * is successful.
492 *
493 * Return value:
494 * < 0 - error code
495 * == 0 - success
496 */
497static int move_to_new_page(struct page *newpage, struct page *page,
498                        int remap_swapcache)
499{
500    struct address_space *mapping;
501    int rc;
502
503    /*
504     * Block others from accessing the page when we get around to
505     * establishing additional references. We are the only one
506     * holding a reference to the new page at this point.
507     */
508    if (!trylock_page(newpage))
509        BUG();
510
511    /* Prepare mapping for the new page.*/
512    newpage->index = page->index;
513    newpage->mapping = page->mapping;
514    if (PageSwapBacked(page))
515        SetPageSwapBacked(newpage);
516
517    mapping = page_mapping(page);
518    if (!mapping)
519        rc = migrate_page(mapping, newpage, page);
520    else if (mapping->a_ops->migratepage)
521        /*
522         * Most pages have a mapping and most filesystems
523         * should provide a migration function. Anonymous
524         * pages are part of swap space which also has its
525         * own migration function. This is the most common
526         * path for page migration.
527         */
528        rc = mapping->a_ops->migratepage(mapping,
529                        newpage, page);
530    else
531        rc = fallback_migrate_page(mapping, newpage, page);
532
533    if (rc) {
534        newpage->mapping = NULL;
535    } else {
536        if (remap_swapcache)
537            remove_migration_ptes(page, newpage);
538    }
539
540    unlock_page(newpage);
541
542    return rc;
543}
544
545/*
546 * Obtain the lock on page, remove all ptes and migrate the page
547 * to the newly allocated page in newpage.
548 */
549static int unmap_and_move(new_page_t get_new_page, unsigned long private,
550            struct page *page, int force, int offlining)
551{
552    int rc = 0;
553    int *result = NULL;
554    struct page *newpage = get_new_page(page, private, &result);
555    int remap_swapcache = 1;
556    int rcu_locked = 0;
557    int charge = 0;
558    struct mem_cgroup *mem = NULL;
559    struct anon_vma *anon_vma = NULL;
560
561    if (!newpage)
562        return -ENOMEM;
563
564    if (page_count(page) == 1) {
565        /* page was freed from under us. So we are done. */
566        goto move_newpage;
567    }
568
569    /* prepare cgroup just returns 0 or -ENOMEM */
570    rc = -EAGAIN;
571
572    if (!trylock_page(page)) {
573        if (!force)
574            goto move_newpage;
575        lock_page(page);
576    }
577
578    /*
579     * Only memory hotplug's offline_pages() caller has locked out KSM,
580     * and can safely migrate a KSM page. The other cases have skipped
581     * PageKsm along with PageReserved - but it is only now when we have
582     * the page lock that we can be certain it will not go KSM beneath us
583     * (KSM will not upgrade a page from PageAnon to PageKsm when it sees
584     * its pagecount raised, but only here do we take the page lock which
585     * serializes that).
586     */
587    if (PageKsm(page) && !offlining) {
588        rc = -EBUSY;
589        goto unlock;
590    }
591
592    /* charge against new page */
593    charge = mem_cgroup_prepare_migration(page, newpage, &mem);
594    if (charge == -ENOMEM) {
595        rc = -ENOMEM;
596        goto unlock;
597    }
598    BUG_ON(charge);
599
600    if (PageWriteback(page)) {
601        if (!force)
602            goto uncharge;
603        wait_on_page_writeback(page);
604    }
605    /*
606     * By try_to_unmap(), page->mapcount goes down to 0 here. In this case,
607     * we cannot notice that anon_vma is freed while we migrates a page.
608     * This rcu_read_lock() delays freeing anon_vma pointer until the end
609     * of migration. File cache pages are no problem because of page_lock()
610     * File Caches may use write_page() or lock_page() in migration, then,
611     * just care Anon page here.
612     */
613    if (PageAnon(page)) {
614        rcu_read_lock();
615        rcu_locked = 1;
616
617        /* Determine how to safely use anon_vma */
618        if (!page_mapped(page)) {
619            if (!PageSwapCache(page))
620                goto rcu_unlock;
621
622            /*
623             * We cannot be sure that the anon_vma of an unmapped
624             * swapcache page is safe to use because we don't
625             * know in advance if the VMA that this page belonged
626             * to still exists. If the VMA and others sharing the
627             * data have been freed, then the anon_vma could
628             * already be invalid.
629             *
630             * To avoid this possibility, swapcache pages get
631             * migrated but are not remapped when migration
632             * completes
633             */
634            remap_swapcache = 0;
635        } else {
636            /*
637             * Take a reference count on the anon_vma if the
638             * page is mapped so that it is guaranteed to
639             * exist when the page is remapped later
640             */
641            anon_vma = page_anon_vma(page);
642            get_anon_vma(anon_vma);
643        }
644    }
645
646    /*
647     * Corner case handling:
648     * 1. When a new swap-cache page is read into, it is added to the LRU
649     * and treated as swapcache but it has no rmap yet.
650     * Calling try_to_unmap() against a page->mapping==NULL page will
651     * trigger a BUG. So handle it here.
652     * 2. An orphaned page (see truncate_complete_page) might have
653     * fs-private metadata. The page can be picked up due to memory
654     * offlining. Everywhere else except page reclaim, the page is
655     * invisible to the vm, so the page can not be migrated. So try to
656     * free the metadata, so the page can be freed.
657     */
658    if (!page->mapping) {
659        if (!PageAnon(page) && page_has_private(page)) {
660            /*
661             * Go direct to try_to_free_buffers() here because
662             * a) that's what try_to_release_page() would do anyway
663             * b) we may be under rcu_read_lock() here, so we can't
664             * use GFP_KERNEL which is what try_to_release_page()
665             * needs to be effective.
666             */
667            try_to_free_buffers(page);
668            goto rcu_unlock;
669        }
670        goto skip_unmap;
671    }
672
673    /* Establish migration ptes or remove ptes */
674    try_to_unmap(page, TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
675
676skip_unmap:
677    if (!page_mapped(page))
678        rc = move_to_new_page(newpage, page, remap_swapcache);
679
680    if (rc && remap_swapcache)
681        remove_migration_ptes(page, page);
682rcu_unlock:
683
684    /* Drop an anon_vma reference if we took one */
685    if (anon_vma)
686        drop_anon_vma(anon_vma);
687
688    if (rcu_locked)
689        rcu_read_unlock();
690uncharge:
691    if (!charge)
692        mem_cgroup_end_migration(mem, page, newpage);
693unlock:
694    unlock_page(page);
695
696    if (rc != -EAGAIN) {
697         /*
698          * A page that has been migrated has all references
699          * removed and will be freed. A page that has not been
700          * migrated will have kepts its references and be
701          * restored.
702          */
703         list_del(&page->lru);
704        dec_zone_page_state(page, NR_ISOLATED_ANON +
705                page_is_file_cache(page));
706        putback_lru_page(page);
707    }
708
709move_newpage:
710
711    /*
712     * Move the new page to the LRU. If migration was not successful
713     * then this will free the page.
714     */
715    putback_lru_page(newpage);
716
717    if (result) {
718        if (rc)
719            *result = rc;
720        else
721            *result = page_to_nid(newpage);
722    }
723    return rc;
724}
725
726/*
727 * migrate_pages
728 *
729 * The function takes one list of pages to migrate and a function
730 * that determines from the page to be migrated and the private data
731 * the target of the move and allocates the page.
732 *
733 * The function returns after 10 attempts or if no pages
734 * are movable anymore because to has become empty
735 * or no retryable pages exist anymore. All pages will be
736 * returned to the LRU or freed.
737 *
738 * Return: Number of pages not migrated or error code.
739 */
740int migrate_pages(struct list_head *from,
741        new_page_t get_new_page, unsigned long private, int offlining)
742{
743    int retry = 1;
744    int nr_failed = 0;
745    int pass = 0;
746    struct page *page;
747    struct page *page2;
748    int swapwrite = current->flags & PF_SWAPWRITE;
749    int rc;
750
751    if (!swapwrite)
752        current->flags |= PF_SWAPWRITE;
753
754    for(pass = 0; pass < 10 && retry; pass++) {
755        retry = 0;
756
757        list_for_each_entry_safe(page, page2, from, lru) {
758            cond_resched();
759
760            rc = unmap_and_move(get_new_page, private,
761                        page, pass > 2, offlining);
762
763            switch(rc) {
764            case -ENOMEM:
765                goto out;
766            case -EAGAIN:
767                retry++;
768                break;
769            case 0:
770                break;
771            default:
772                /* Permanent failure */
773                nr_failed++;
774                break;
775            }
776        }
777    }
778    rc = 0;
779out:
780    if (!swapwrite)
781        current->flags &= ~PF_SWAPWRITE;
782
783    putback_lru_pages(from);
784
785    if (rc)
786        return rc;
787
788    return nr_failed + retry;
789}
790
791#ifdef CONFIG_NUMA
792/*
793 * Move a list of individual pages
794 */
795struct page_to_node {
796    unsigned long addr;
797    struct page *page;
798    int node;
799    int status;
800};
801
802static struct page *new_page_node(struct page *p, unsigned long private,
803        int **result)
804{
805    struct page_to_node *pm = (struct page_to_node *)private;
806
807    while (pm->node != MAX_NUMNODES && pm->page != p)
808        pm++;
809
810    if (pm->node == MAX_NUMNODES)
811        return NULL;
812
813    *result = &pm->status;
814
815    return alloc_pages_exact_node(pm->node,
816                GFP_HIGHUSER_MOVABLE | GFP_THISNODE, 0);
817}
818
819/*
820 * Move a set of pages as indicated in the pm array. The addr
821 * field must be set to the virtual address of the page to be moved
822 * and the node number must contain a valid target node.
823 * The pm array ends with node = MAX_NUMNODES.
824 */
825static int do_move_page_to_node_array(struct mm_struct *mm,
826                      struct page_to_node *pm,
827                      int migrate_all)
828{
829    int err;
830    struct page_to_node *pp;
831    LIST_HEAD(pagelist);
832
833    down_read(&mm->mmap_sem);
834
835    /*
836     * Build a list of pages to migrate
837     */
838    for (pp = pm; pp->node != MAX_NUMNODES; pp++) {
839        struct vm_area_struct *vma;
840        struct page *page;
841
842        err = -EFAULT;
843        vma = find_vma(mm, pp->addr);
844        if (!vma || !vma_migratable(vma))
845            goto set_status;
846
847        page = follow_page(vma, pp->addr, FOLL_GET);
848
849        err = PTR_ERR(page);
850        if (IS_ERR(page))
851            goto set_status;
852
853        err = -ENOENT;
854        if (!page)
855            goto set_status;
856
857        /* Use PageReserved to check for zero page */
858        if (PageReserved(page) || PageKsm(page))
859            goto put_and_set;
860
861        pp->page = page;
862        err = page_to_nid(page);
863
864        if (err == pp->node)
865            /*
866             * Node already in the right place
867             */
868            goto put_and_set;
869
870        err = -EACCES;
871        if (page_mapcount(page) > 1 &&
872                !migrate_all)
873            goto put_and_set;
874
875        err = isolate_lru_page(page);
876        if (!err) {
877            list_add_tail(&page->lru, &pagelist);
878            inc_zone_page_state(page, NR_ISOLATED_ANON +
879                        page_is_file_cache(page));
880        }
881put_and_set:
882        /*
883         * Either remove the duplicate refcount from
884         * isolate_lru_page() or drop the page ref if it was
885         * not isolated.
886         */
887        put_page(page);
888set_status:
889        pp->status = err;
890    }
891
892    err = 0;
893    if (!list_empty(&pagelist))
894        err = migrate_pages(&pagelist, new_page_node,
895                (unsigned long)pm, 0);
896
897    up_read(&mm->mmap_sem);
898    return err;
899}
900
901/*
902 * Migrate an array of page address onto an array of nodes and fill
903 * the corresponding array of status.
904 */
905static int do_pages_move(struct mm_struct *mm, struct task_struct *task,
906             unsigned long nr_pages,
907             const void __user * __user *pages,
908             const int __user *nodes,
909             int __user *status, int flags)
910{
911    struct page_to_node *pm;
912    nodemask_t task_nodes;
913    unsigned long chunk_nr_pages;
914    unsigned long chunk_start;
915    int err;
916
917    task_nodes = cpuset_mems_allowed(task);
918
919    err = -ENOMEM;
920    pm = (struct page_to_node *)__get_free_page(GFP_KERNEL);
921    if (!pm)
922        goto out;
923
924    migrate_prep();
925
926    /*
927     * Store a chunk of page_to_node array in a page,
928     * but keep the last one as a marker
929     */
930    chunk_nr_pages = (PAGE_SIZE / sizeof(struct page_to_node)) - 1;
931
932    for (chunk_start = 0;
933         chunk_start < nr_pages;
934         chunk_start += chunk_nr_pages) {
935        int j;
936
937        if (chunk_start + chunk_nr_pages > nr_pages)
938            chunk_nr_pages = nr_pages - chunk_start;
939
940        /* fill the chunk pm with addrs and nodes from user-space */
941        for (j = 0; j < chunk_nr_pages; j++) {
942            const void __user *p;
943            int node;
944
945            err = -EFAULT;
946            if (get_user(p, pages + j + chunk_start))
947                goto out_pm;
948            pm[j].addr = (unsigned long) p;
949
950            if (get_user(node, nodes + j + chunk_start))
951                goto out_pm;
952
953            err = -ENODEV;
954            if (node < 0 || node >= MAX_NUMNODES)
955                goto out_pm;
956
957            if (!node_state(node, N_HIGH_MEMORY))
958                goto out_pm;
959
960            err = -EACCES;
961            if (!node_isset(node, task_nodes))
962                goto out_pm;
963
964            pm[j].node = node;
965        }
966
967        /* End marker for this chunk */
968        pm[chunk_nr_pages].node = MAX_NUMNODES;
969
970        /* Migrate this chunk */
971        err = do_move_page_to_node_array(mm, pm,
972                         flags & MPOL_MF_MOVE_ALL);
973        if (err < 0)
974            goto out_pm;
975
976        /* Return status information */
977        for (j = 0; j < chunk_nr_pages; j++)
978            if (put_user(pm[j].status, status + j + chunk_start)) {
979                err = -EFAULT;
980                goto out_pm;
981            }
982    }
983    err = 0;
984
985out_pm:
986    free_page((unsigned long)pm);
987out:
988    return err;
989}
990
991/*
992 * Determine the nodes of an array of pages and store it in an array of status.
993 */
994static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
995                const void __user **pages, int *status)
996{
997    unsigned long i;
998
999    down_read(&mm->mmap_sem);
1000
1001    for (i = 0; i < nr_pages; i++) {
1002        unsigned long addr = (unsigned long)(*pages);
1003        struct vm_area_struct *vma;
1004        struct page *page;
1005        int err = -EFAULT;
1006
1007        vma = find_vma(mm, addr);
1008        if (!vma)
1009            goto set_status;
1010
1011        page = follow_page(vma, addr, 0);
1012
1013        err = PTR_ERR(page);
1014        if (IS_ERR(page))
1015            goto set_status;
1016
1017        err = -ENOENT;
1018        /* Use PageReserved to check for zero page */
1019        if (!page || PageReserved(page) || PageKsm(page))
1020            goto set_status;
1021
1022        err = page_to_nid(page);
1023set_status:
1024        *status = err;
1025
1026        pages++;
1027        status++;
1028    }
1029
1030    up_read(&mm->mmap_sem);
1031}
1032
1033/*
1034 * Determine the nodes of a user array of pages and store it in
1035 * a user array of status.
1036 */
1037static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
1038             const void __user * __user *pages,
1039             int __user *status)
1040{
1041#define DO_PAGES_STAT_CHUNK_NR 16
1042    const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR];
1043    int chunk_status[DO_PAGES_STAT_CHUNK_NR];
1044
1045    while (nr_pages) {
1046        unsigned long chunk_nr;
1047
1048        chunk_nr = nr_pages;
1049        if (chunk_nr > DO_PAGES_STAT_CHUNK_NR)
1050            chunk_nr = DO_PAGES_STAT_CHUNK_NR;
1051
1052        if (copy_from_user(chunk_pages, pages, chunk_nr * sizeof(*chunk_pages)))
1053            break;
1054
1055        do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status);
1056
1057        if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status)))
1058            break;
1059
1060        pages += chunk_nr;
1061        status += chunk_nr;
1062        nr_pages -= chunk_nr;
1063    }
1064    return nr_pages ? -EFAULT : 0;
1065}
1066
1067/*
1068 * Move a list of pages in the address space of the currently executing
1069 * process.
1070 */
1071SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages,
1072        const void __user * __user *, pages,
1073        const int __user *, nodes,
1074        int __user *, status, int, flags)
1075{
1076    const struct cred *cred = current_cred(), *tcred;
1077    struct task_struct *task;
1078    struct mm_struct *mm;
1079    int err;
1080
1081    /* Check flags */
1082    if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL))
1083        return -EINVAL;
1084
1085    if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
1086        return -EPERM;
1087
1088    /* Find the mm_struct */
1089    read_lock(&tasklist_lock);
1090    task = pid ? find_task_by_vpid(pid) : current;
1091    if (!task) {
1092        read_unlock(&tasklist_lock);
1093        return -ESRCH;
1094    }
1095    mm = get_task_mm(task);
1096    read_unlock(&tasklist_lock);
1097
1098    if (!mm)
1099        return -EINVAL;
1100
1101    /*
1102     * Check if this process has the right to modify the specified
1103     * process. The right exists if the process has administrative
1104     * capabilities, superuser privileges or the same
1105     * userid as the target process.
1106     */
1107    rcu_read_lock();
1108    tcred = __task_cred(task);
1109    if (cred->euid != tcred->suid && cred->euid != tcred->uid &&
1110        cred->uid != tcred->suid && cred->uid != tcred->uid &&
1111        !capable(CAP_SYS_NICE)) {
1112        rcu_read_unlock();
1113        err = -EPERM;
1114        goto out;
1115    }
1116    rcu_read_unlock();
1117
1118     err = security_task_movememory(task);
1119     if (err)
1120        goto out;
1121
1122    if (nodes) {
1123        err = do_pages_move(mm, task, nr_pages, pages, nodes, status,
1124                    flags);
1125    } else {
1126        err = do_pages_stat(mm, nr_pages, pages, status);
1127    }
1128
1129out:
1130    mmput(mm);
1131    return err;
1132}
1133
1134/*
1135 * Call migration functions in the vma_ops that may prepare
1136 * memory in a vm for migration. migration functions may perform
1137 * the migration for vmas that do not have an underlying page struct.
1138 */
1139int migrate_vmas(struct mm_struct *mm, const nodemask_t *to,
1140    const nodemask_t *from, unsigned long flags)
1141{
1142     struct vm_area_struct *vma;
1143     int err = 0;
1144
1145    for (vma = mm->mmap; vma && !err; vma = vma->vm_next) {
1146         if (vma->vm_ops && vma->vm_ops->migrate) {
1147             err = vma->vm_ops->migrate(vma, to, from, flags);
1148             if (err)
1149                 break;
1150         }
1151     }
1152     return err;
1153}
1154#endif
1155

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