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            atomic_inc(&anon_vma->external_refcount);
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 && atomic_dec_and_lock(&anon_vma->external_refcount, &anon_vma->lock)) {
686        int empty = list_empty(&anon_vma->head);
687        spin_unlock(&anon_vma->lock);
688        if (empty)
689            anon_vma_free(anon_vma);
690    }
691
692    if (rcu_locked)
693        rcu_read_unlock();
694uncharge:
695    if (!charge)
696        mem_cgroup_end_migration(mem, page, newpage);
697unlock:
698    unlock_page(page);
699
700    if (rc != -EAGAIN) {
701         /*
702          * A page that has been migrated has all references
703          * removed and will be freed. A page that has not been
704          * migrated will have kepts its references and be
705          * restored.
706          */
707         list_del(&page->lru);
708        dec_zone_page_state(page, NR_ISOLATED_ANON +
709                page_is_file_cache(page));
710        putback_lru_page(page);
711    }
712
713move_newpage:
714
715    /*
716     * Move the new page to the LRU. If migration was not successful
717     * then this will free the page.
718     */
719    putback_lru_page(newpage);
720
721    if (result) {
722        if (rc)
723            *result = rc;
724        else
725            *result = page_to_nid(newpage);
726    }
727    return rc;
728}
729
730/*
731 * migrate_pages
732 *
733 * The function takes one list of pages to migrate and a function
734 * that determines from the page to be migrated and the private data
735 * the target of the move and allocates the page.
736 *
737 * The function returns after 10 attempts or if no pages
738 * are movable anymore because to has become empty
739 * or no retryable pages exist anymore. All pages will be
740 * returned to the LRU or freed.
741 *
742 * Return: Number of pages not migrated or error code.
743 */
744int migrate_pages(struct list_head *from,
745        new_page_t get_new_page, unsigned long private, int offlining)
746{
747    int retry = 1;
748    int nr_failed = 0;
749    int pass = 0;
750    struct page *page;
751    struct page *page2;
752    int swapwrite = current->flags & PF_SWAPWRITE;
753    int rc;
754
755    if (!swapwrite)
756        current->flags |= PF_SWAPWRITE;
757
758    for(pass = 0; pass < 10 && retry; pass++) {
759        retry = 0;
760
761        list_for_each_entry_safe(page, page2, from, lru) {
762            cond_resched();
763
764            rc = unmap_and_move(get_new_page, private,
765                        page, pass > 2, offlining);
766
767            switch(rc) {
768            case -ENOMEM:
769                goto out;
770            case -EAGAIN:
771                retry++;
772                break;
773            case 0:
774                break;
775            default:
776                /* Permanent failure */
777                nr_failed++;
778                break;
779            }
780        }
781    }
782    rc = 0;
783out:
784    if (!swapwrite)
785        current->flags &= ~PF_SWAPWRITE;
786
787    putback_lru_pages(from);
788
789    if (rc)
790        return rc;
791
792    return nr_failed + retry;
793}
794
795#ifdef CONFIG_NUMA
796/*
797 * Move a list of individual pages
798 */
799struct page_to_node {
800    unsigned long addr;
801    struct page *page;
802    int node;
803    int status;
804};
805
806static struct page *new_page_node(struct page *p, unsigned long private,
807        int **result)
808{
809    struct page_to_node *pm = (struct page_to_node *)private;
810
811    while (pm->node != MAX_NUMNODES && pm->page != p)
812        pm++;
813
814    if (pm->node == MAX_NUMNODES)
815        return NULL;
816
817    *result = &pm->status;
818
819    return alloc_pages_exact_node(pm->node,
820                GFP_HIGHUSER_MOVABLE | GFP_THISNODE, 0);
821}
822
823/*
824 * Move a set of pages as indicated in the pm array. The addr
825 * field must be set to the virtual address of the page to be moved
826 * and the node number must contain a valid target node.
827 * The pm array ends with node = MAX_NUMNODES.
828 */
829static int do_move_page_to_node_array(struct mm_struct *mm,
830                      struct page_to_node *pm,
831                      int migrate_all)
832{
833    int err;
834    struct page_to_node *pp;
835    LIST_HEAD(pagelist);
836
837    down_read(&mm->mmap_sem);
838
839    /*
840     * Build a list of pages to migrate
841     */
842    for (pp = pm; pp->node != MAX_NUMNODES; pp++) {
843        struct vm_area_struct *vma;
844        struct page *page;
845
846        err = -EFAULT;
847        vma = find_vma(mm, pp->addr);
848        if (!vma || !vma_migratable(vma))
849            goto set_status;
850
851        page = follow_page(vma, pp->addr, FOLL_GET);
852
853        err = PTR_ERR(page);
854        if (IS_ERR(page))
855            goto set_status;
856
857        err = -ENOENT;
858        if (!page)
859            goto set_status;
860
861        /* Use PageReserved to check for zero page */
862        if (PageReserved(page) || PageKsm(page))
863            goto put_and_set;
864
865        pp->page = page;
866        err = page_to_nid(page);
867
868        if (err == pp->node)
869            /*
870             * Node already in the right place
871             */
872            goto put_and_set;
873
874        err = -EACCES;
875        if (page_mapcount(page) > 1 &&
876                !migrate_all)
877            goto put_and_set;
878
879        err = isolate_lru_page(page);
880        if (!err) {
881            list_add_tail(&page->lru, &pagelist);
882            inc_zone_page_state(page, NR_ISOLATED_ANON +
883                        page_is_file_cache(page));
884        }
885put_and_set:
886        /*
887         * Either remove the duplicate refcount from
888         * isolate_lru_page() or drop the page ref if it was
889         * not isolated.
890         */
891        put_page(page);
892set_status:
893        pp->status = err;
894    }
895
896    err = 0;
897    if (!list_empty(&pagelist))
898        err = migrate_pages(&pagelist, new_page_node,
899                (unsigned long)pm, 0);
900
901    up_read(&mm->mmap_sem);
902    return err;
903}
904
905/*
906 * Migrate an array of page address onto an array of nodes and fill
907 * the corresponding array of status.
908 */
909static int do_pages_move(struct mm_struct *mm, struct task_struct *task,
910             unsigned long nr_pages,
911             const void __user * __user *pages,
912             const int __user *nodes,
913             int __user *status, int flags)
914{
915    struct page_to_node *pm;
916    nodemask_t task_nodes;
917    unsigned long chunk_nr_pages;
918    unsigned long chunk_start;
919    int err;
920
921    task_nodes = cpuset_mems_allowed(task);
922
923    err = -ENOMEM;
924    pm = (struct page_to_node *)__get_free_page(GFP_KERNEL);
925    if (!pm)
926        goto out;
927
928    migrate_prep();
929
930    /*
931     * Store a chunk of page_to_node array in a page,
932     * but keep the last one as a marker
933     */
934    chunk_nr_pages = (PAGE_SIZE / sizeof(struct page_to_node)) - 1;
935
936    for (chunk_start = 0;
937         chunk_start < nr_pages;
938         chunk_start += chunk_nr_pages) {
939        int j;
940
941        if (chunk_start + chunk_nr_pages > nr_pages)
942            chunk_nr_pages = nr_pages - chunk_start;
943
944        /* fill the chunk pm with addrs and nodes from user-space */
945        for (j = 0; j < chunk_nr_pages; j++) {
946            const void __user *p;
947            int node;
948
949            err = -EFAULT;
950            if (get_user(p, pages + j + chunk_start))
951                goto out_pm;
952            pm[j].addr = (unsigned long) p;
953
954            if (get_user(node, nodes + j + chunk_start))
955                goto out_pm;
956
957            err = -ENODEV;
958            if (node < 0 || node >= MAX_NUMNODES)
959                goto out_pm;
960
961            if (!node_state(node, N_HIGH_MEMORY))
962                goto out_pm;
963
964            err = -EACCES;
965            if (!node_isset(node, task_nodes))
966                goto out_pm;
967
968            pm[j].node = node;
969        }
970
971        /* End marker for this chunk */
972        pm[chunk_nr_pages].node = MAX_NUMNODES;
973
974        /* Migrate this chunk */
975        err = do_move_page_to_node_array(mm, pm,
976                         flags & MPOL_MF_MOVE_ALL);
977        if (err < 0)
978            goto out_pm;
979
980        /* Return status information */
981        for (j = 0; j < chunk_nr_pages; j++)
982            if (put_user(pm[j].status, status + j + chunk_start)) {
983                err = -EFAULT;
984                goto out_pm;
985            }
986    }
987    err = 0;
988
989out_pm:
990    free_page((unsigned long)pm);
991out:
992    return err;
993}
994
995/*
996 * Determine the nodes of an array of pages and store it in an array of status.
997 */
998static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
999                const void __user **pages, int *status)
1000{
1001    unsigned long i;
1002
1003    down_read(&mm->mmap_sem);
1004
1005    for (i = 0; i < nr_pages; i++) {
1006        unsigned long addr = (unsigned long)(*pages);
1007        struct vm_area_struct *vma;
1008        struct page *page;
1009        int err = -EFAULT;
1010
1011        vma = find_vma(mm, addr);
1012        if (!vma)
1013            goto set_status;
1014
1015        page = follow_page(vma, addr, 0);
1016
1017        err = PTR_ERR(page);
1018        if (IS_ERR(page))
1019            goto set_status;
1020
1021        err = -ENOENT;
1022        /* Use PageReserved to check for zero page */
1023        if (!page || PageReserved(page) || PageKsm(page))
1024            goto set_status;
1025
1026        err = page_to_nid(page);
1027set_status:
1028        *status = err;
1029
1030        pages++;
1031        status++;
1032    }
1033
1034    up_read(&mm->mmap_sem);
1035}
1036
1037/*
1038 * Determine the nodes of a user array of pages and store it in
1039 * a user array of status.
1040 */
1041static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
1042             const void __user * __user *pages,
1043             int __user *status)
1044{
1045#define DO_PAGES_STAT_CHUNK_NR 16
1046    const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR];
1047    int chunk_status[DO_PAGES_STAT_CHUNK_NR];
1048
1049    while (nr_pages) {
1050        unsigned long chunk_nr;
1051
1052        chunk_nr = nr_pages;
1053        if (chunk_nr > DO_PAGES_STAT_CHUNK_NR)
1054            chunk_nr = DO_PAGES_STAT_CHUNK_NR;
1055
1056        if (copy_from_user(chunk_pages, pages, chunk_nr * sizeof(*chunk_pages)))
1057            break;
1058
1059        do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status);
1060
1061        if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status)))
1062            break;
1063
1064        pages += chunk_nr;
1065        status += chunk_nr;
1066        nr_pages -= chunk_nr;
1067    }
1068    return nr_pages ? -EFAULT : 0;
1069}
1070
1071/*
1072 * Move a list of pages in the address space of the currently executing
1073 * process.
1074 */
1075SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages,
1076        const void __user * __user *, pages,
1077        const int __user *, nodes,
1078        int __user *, status, int, flags)
1079{
1080    const struct cred *cred = current_cred(), *tcred;
1081    struct task_struct *task;
1082    struct mm_struct *mm;
1083    int err;
1084
1085    /* Check flags */
1086    if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL))
1087        return -EINVAL;
1088
1089    if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
1090        return -EPERM;
1091
1092    /* Find the mm_struct */
1093    read_lock(&tasklist_lock);
1094    task = pid ? find_task_by_vpid(pid) : current;
1095    if (!task) {
1096        read_unlock(&tasklist_lock);
1097        return -ESRCH;
1098    }
1099    mm = get_task_mm(task);
1100    read_unlock(&tasklist_lock);
1101
1102    if (!mm)
1103        return -EINVAL;
1104
1105    /*
1106     * Check if this process has the right to modify the specified
1107     * process. The right exists if the process has administrative
1108     * capabilities, superuser privileges or the same
1109     * userid as the target process.
1110     */
1111    rcu_read_lock();
1112    tcred = __task_cred(task);
1113    if (cred->euid != tcred->suid && cred->euid != tcred->uid &&
1114        cred->uid != tcred->suid && cred->uid != tcred->uid &&
1115        !capable(CAP_SYS_NICE)) {
1116        rcu_read_unlock();
1117        err = -EPERM;
1118        goto out;
1119    }
1120    rcu_read_unlock();
1121
1122     err = security_task_movememory(task);
1123     if (err)
1124        goto out;
1125
1126    if (nodes) {
1127        err = do_pages_move(mm, task, nr_pages, pages, nodes, status,
1128                    flags);
1129    } else {
1130        err = do_pages_stat(mm, nr_pages, pages, status);
1131    }
1132
1133out:
1134    mmput(mm);
1135    return err;
1136}
1137
1138/*
1139 * Call migration functions in the vma_ops that may prepare
1140 * memory in a vm for migration. migration functions may perform
1141 * the migration for vmas that do not have an underlying page struct.
1142 */
1143int migrate_vmas(struct mm_struct *mm, const nodemask_t *to,
1144    const nodemask_t *from, unsigned long flags)
1145{
1146     struct vm_area_struct *vma;
1147     int err = 0;
1148
1149    for (vma = mm->mmap; vma && !err; vma = vma->vm_next) {
1150         if (vma->vm_ops && vma->vm_ops->migrate) {
1151             err = vma->vm_ops->migrate(vma, to, from, flags);
1152             if (err)
1153                 break;
1154         }
1155     }
1156     return err;
1157}
1158#endif
1159

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