2 * Memory Migration functionality - linux/mm/migration.c
4 * Copyright (C) 2006 Silicon Graphics, Inc., Christoph Lameter
6 * Page migration was first developed in the context of the memory hotplug
7 * project. The main authors of the migration code are:
9 * IWAMOTO Toshihiro <iwamoto@valinux.co.jp>
10 * Hirokazu Takahashi <taka@valinux.co.jp>
11 * Dave Hansen <haveblue@us.ibm.com>
15 #include <linux/migrate.h>
16 #include <linux/export.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/hugetlb.h>
36 #include <linux/hugetlb_cgroup.h>
37 #include <linux/gfp.h>
39 #include <asm/tlbflush.h>
41 #define CREATE_TRACE_POINTS
42 #include <trace/events/migrate.h>
47 * migrate_prep() needs to be called before we start compiling a list of pages
48 * to be migrated using isolate_lru_page(). If scheduling work on other CPUs is
49 * undesirable, use migrate_prep_local()
51 int migrate_prep(void)
54 * Clear the LRU lists so pages can be isolated.
55 * Note that pages may be moved off the LRU after we have
56 * drained them. Those pages will fail to migrate like other
57 * pages that may be busy.
64 /* Do the necessary work of migrate_prep but not if it involves other CPUs */
65 int migrate_prep_local(void)
73 * Add isolated pages on the list back to the LRU under page lock
74 * to avoid leaking evictable pages back onto unevictable list.
76 void putback_lru_pages(struct list_head
*l
)
81 list_for_each_entry_safe(page
, page2
, l
, lru
) {
83 dec_zone_page_state(page
, NR_ISOLATED_ANON
+
84 page_is_file_cache(page
));
85 putback_lru_page(page
);
90 * Restore a potential migration pte to a working pte entry
92 static int remove_migration_pte(struct page
*new, struct vm_area_struct
*vma
,
93 unsigned long addr
, void *old
)
95 struct mm_struct
*mm
= vma
->vm_mm
;
103 if (unlikely(PageHuge(new))) {
104 ptep
= huge_pte_offset(mm
, addr
);
107 ptl
= &mm
->page_table_lock
;
109 pgd
= pgd_offset(mm
, addr
);
110 if (!pgd_present(*pgd
))
113 pud
= pud_offset(pgd
, addr
);
114 if (!pud_present(*pud
))
117 pmd
= pmd_offset(pud
, addr
);
118 if (pmd_trans_huge(*pmd
))
120 if (!pmd_present(*pmd
))
123 ptep
= pte_offset_map(pmd
, addr
);
126 * Peek to check is_swap_pte() before taking ptlock? No, we
127 * can race mremap's move_ptes(), which skips anon_vma lock.
130 ptl
= pte_lockptr(mm
, pmd
);
135 if (!is_swap_pte(pte
))
138 entry
= pte_to_swp_entry(pte
);
140 if (!is_migration_entry(entry
) ||
141 migration_entry_to_page(entry
) != old
)
145 pte
= pte_mkold(mk_pte(new, vma
->vm_page_prot
));
146 if (is_write_migration_entry(entry
))
147 pte
= pte_mkwrite(pte
);
148 #ifdef CONFIG_HUGETLB_PAGE
150 pte
= pte_mkhuge(pte
);
152 flush_cache_page(vma
, addr
, pte_pfn(pte
));
153 set_pte_at(mm
, addr
, ptep
, pte
);
157 hugepage_add_anon_rmap(new, vma
, addr
);
160 } else if (PageAnon(new))
161 page_add_anon_rmap(new, vma
, addr
);
163 page_add_file_rmap(new);
165 /* No need to invalidate - it was non-present before */
166 update_mmu_cache(vma
, addr
, ptep
);
168 pte_unmap_unlock(ptep
, ptl
);
174 * Get rid of all migration entries and replace them by
175 * references to the indicated page.
177 static void remove_migration_ptes(struct page
*old
, struct page
*new)
179 rmap_walk(new, remove_migration_pte
, old
);
183 * Something used the pte of a page under migration. We need to
184 * get to the page and wait until migration is finished.
185 * When we return from this function the fault will be retried.
187 void migration_entry_wait(struct mm_struct
*mm
, pmd_t
*pmd
,
188 unsigned long address
)
195 ptep
= pte_offset_map_lock(mm
, pmd
, address
, &ptl
);
197 if (!is_swap_pte(pte
))
200 entry
= pte_to_swp_entry(pte
);
201 if (!is_migration_entry(entry
))
204 page
= migration_entry_to_page(entry
);
207 * Once radix-tree replacement of page migration started, page_count
208 * *must* be zero. And, we don't want to call wait_on_page_locked()
209 * against a page without get_page().
210 * So, we use get_page_unless_zero(), here. Even failed, page fault
213 if (!get_page_unless_zero(page
))
215 pte_unmap_unlock(ptep
, ptl
);
216 wait_on_page_locked(page
);
220 pte_unmap_unlock(ptep
, ptl
);
224 /* Returns true if all buffers are successfully locked */
225 static bool buffer_migrate_lock_buffers(struct buffer_head
*head
,
226 enum migrate_mode mode
)
228 struct buffer_head
*bh
= head
;
230 /* Simple case, sync compaction */
231 if (mode
!= MIGRATE_ASYNC
) {
235 bh
= bh
->b_this_page
;
237 } while (bh
!= head
);
242 /* async case, we cannot block on lock_buffer so use trylock_buffer */
245 if (!trylock_buffer(bh
)) {
247 * We failed to lock the buffer and cannot stall in
248 * async migration. Release the taken locks
250 struct buffer_head
*failed_bh
= bh
;
253 while (bh
!= failed_bh
) {
256 bh
= bh
->b_this_page
;
261 bh
= bh
->b_this_page
;
262 } while (bh
!= head
);
266 static inline bool buffer_migrate_lock_buffers(struct buffer_head
*head
,
267 enum migrate_mode mode
)
271 #endif /* CONFIG_BLOCK */
274 * Replace the page in the mapping.
276 * The number of remaining references must be:
277 * 1 for anonymous pages without a mapping
278 * 2 for pages with a mapping
279 * 3 for pages with a mapping and PagePrivate/PagePrivate2 set.
281 static int migrate_page_move_mapping(struct address_space
*mapping
,
282 struct page
*newpage
, struct page
*page
,
283 struct buffer_head
*head
, enum migrate_mode mode
)
285 int expected_count
= 0;
289 /* Anonymous page without mapping */
290 if (page_count(page
) != 1)
295 spin_lock_irq(&mapping
->tree_lock
);
297 pslot
= radix_tree_lookup_slot(&mapping
->page_tree
,
300 expected_count
= 2 + page_has_private(page
);
301 if (page_count(page
) != expected_count
||
302 radix_tree_deref_slot_protected(pslot
, &mapping
->tree_lock
) != page
) {
303 spin_unlock_irq(&mapping
->tree_lock
);
307 if (!page_freeze_refs(page
, expected_count
)) {
308 spin_unlock_irq(&mapping
->tree_lock
);
313 * In the async migration case of moving a page with buffers, lock the
314 * buffers using trylock before the mapping is moved. If the mapping
315 * was moved, we later failed to lock the buffers and could not move
316 * the mapping back due to an elevated page count, we would have to
317 * block waiting on other references to be dropped.
319 if (mode
== MIGRATE_ASYNC
&& head
&&
320 !buffer_migrate_lock_buffers(head
, mode
)) {
321 page_unfreeze_refs(page
, expected_count
);
322 spin_unlock_irq(&mapping
->tree_lock
);
327 * Now we know that no one else is looking at the page.
329 get_page(newpage
); /* add cache reference */
330 if (PageSwapCache(page
)) {
331 SetPageSwapCache(newpage
);
332 set_page_private(newpage
, page_private(page
));
335 radix_tree_replace_slot(pslot
, newpage
);
338 * Drop cache reference from old page by unfreezing
339 * to one less reference.
340 * We know this isn't the last reference.
342 page_unfreeze_refs(page
, expected_count
- 1);
345 * If moved to a different zone then also account
346 * the page for that zone. Other VM counters will be
347 * taken care of when we establish references to the
348 * new page and drop references to the old page.
350 * Note that anonymous pages are accounted for
351 * via NR_FILE_PAGES and NR_ANON_PAGES if they
352 * are mapped to swap space.
354 __dec_zone_page_state(page
, NR_FILE_PAGES
);
355 __inc_zone_page_state(newpage
, NR_FILE_PAGES
);
356 if (!PageSwapCache(page
) && PageSwapBacked(page
)) {
357 __dec_zone_page_state(page
, NR_SHMEM
);
358 __inc_zone_page_state(newpage
, NR_SHMEM
);
360 spin_unlock_irq(&mapping
->tree_lock
);
366 * The expected number of remaining references is the same as that
367 * of migrate_page_move_mapping().
369 int migrate_huge_page_move_mapping(struct address_space
*mapping
,
370 struct page
*newpage
, struct page
*page
)
376 if (page_count(page
) != 1)
381 spin_lock_irq(&mapping
->tree_lock
);
383 pslot
= radix_tree_lookup_slot(&mapping
->page_tree
,
386 expected_count
= 2 + page_has_private(page
);
387 if (page_count(page
) != expected_count
||
388 radix_tree_deref_slot_protected(pslot
, &mapping
->tree_lock
) != page
) {
389 spin_unlock_irq(&mapping
->tree_lock
);
393 if (!page_freeze_refs(page
, expected_count
)) {
394 spin_unlock_irq(&mapping
->tree_lock
);
400 radix_tree_replace_slot(pslot
, newpage
);
402 page_unfreeze_refs(page
, expected_count
- 1);
404 spin_unlock_irq(&mapping
->tree_lock
);
409 * Copy the page to its new location
411 void migrate_page_copy(struct page
*newpage
, struct page
*page
)
414 copy_huge_page(newpage
, page
);
416 copy_highpage(newpage
, page
);
419 SetPageError(newpage
);
420 if (PageReferenced(page
))
421 SetPageReferenced(newpage
);
422 if (PageUptodate(page
))
423 SetPageUptodate(newpage
);
424 if (TestClearPageActive(page
)) {
425 VM_BUG_ON(PageUnevictable(page
));
426 SetPageActive(newpage
);
427 } else if (TestClearPageUnevictable(page
))
428 SetPageUnevictable(newpage
);
429 if (PageChecked(page
))
430 SetPageChecked(newpage
);
431 if (PageMappedToDisk(page
))
432 SetPageMappedToDisk(newpage
);
434 if (PageDirty(page
)) {
435 clear_page_dirty_for_io(page
);
437 * Want to mark the page and the radix tree as dirty, and
438 * redo the accounting that clear_page_dirty_for_io undid,
439 * but we can't use set_page_dirty because that function
440 * is actually a signal that all of the page has become dirty.
441 * Whereas only part of our page may be dirty.
443 if (PageSwapBacked(page
))
444 SetPageDirty(newpage
);
446 __set_page_dirty_nobuffers(newpage
);
449 mlock_migrate_page(newpage
, page
);
450 ksm_migrate_page(newpage
, page
);
452 ClearPageSwapCache(page
);
453 ClearPagePrivate(page
);
454 set_page_private(page
, 0);
457 * If any waiters have accumulated on the new page then
460 if (PageWriteback(newpage
))
461 end_page_writeback(newpage
);
464 /************************************************************
465 * Migration functions
466 ***********************************************************/
468 /* Always fail migration. Used for mappings that are not movable */
469 int fail_migrate_page(struct address_space
*mapping
,
470 struct page
*newpage
, struct page
*page
)
474 EXPORT_SYMBOL(fail_migrate_page
);
477 * Common logic to directly migrate a single page suitable for
478 * pages that do not use PagePrivate/PagePrivate2.
480 * Pages are locked upon entry and exit.
482 int migrate_page(struct address_space
*mapping
,
483 struct page
*newpage
, struct page
*page
,
484 enum migrate_mode mode
)
488 BUG_ON(PageWriteback(page
)); /* Writeback must be complete */
490 rc
= migrate_page_move_mapping(mapping
, newpage
, page
, NULL
, mode
);
495 migrate_page_copy(newpage
, page
);
498 EXPORT_SYMBOL(migrate_page
);
502 * Migration function for pages with buffers. This function can only be used
503 * if the underlying filesystem guarantees that no other references to "page"
506 int buffer_migrate_page(struct address_space
*mapping
,
507 struct page
*newpage
, struct page
*page
, enum migrate_mode mode
)
509 struct buffer_head
*bh
, *head
;
512 if (!page_has_buffers(page
))
513 return migrate_page(mapping
, newpage
, page
, mode
);
515 head
= page_buffers(page
);
517 rc
= migrate_page_move_mapping(mapping
, newpage
, page
, head
, mode
);
523 * In the async case, migrate_page_move_mapping locked the buffers
524 * with an IRQ-safe spinlock held. In the sync case, the buffers
525 * need to be locked now
527 if (mode
!= MIGRATE_ASYNC
)
528 BUG_ON(!buffer_migrate_lock_buffers(head
, mode
));
530 ClearPagePrivate(page
);
531 set_page_private(newpage
, page_private(page
));
532 set_page_private(page
, 0);
538 set_bh_page(bh
, newpage
, bh_offset(bh
));
539 bh
= bh
->b_this_page
;
541 } while (bh
!= head
);
543 SetPagePrivate(newpage
);
545 migrate_page_copy(newpage
, page
);
551 bh
= bh
->b_this_page
;
553 } while (bh
!= head
);
557 EXPORT_SYMBOL(buffer_migrate_page
);
561 * Writeback a page to clean the dirty state
563 static int writeout(struct address_space
*mapping
, struct page
*page
)
565 struct writeback_control wbc
= {
566 .sync_mode
= WB_SYNC_NONE
,
569 .range_end
= LLONG_MAX
,
574 if (!mapping
->a_ops
->writepage
)
575 /* No write method for the address space */
578 if (!clear_page_dirty_for_io(page
))
579 /* Someone else already triggered a write */
583 * A dirty page may imply that the underlying filesystem has
584 * the page on some queue. So the page must be clean for
585 * migration. Writeout may mean we loose the lock and the
586 * page state is no longer what we checked for earlier.
587 * At this point we know that the migration attempt cannot
590 remove_migration_ptes(page
, page
);
592 rc
= mapping
->a_ops
->writepage(page
, &wbc
);
594 if (rc
!= AOP_WRITEPAGE_ACTIVATE
)
595 /* unlocked. Relock */
598 return (rc
< 0) ? -EIO
: -EAGAIN
;
602 * Default handling if a filesystem does not provide a migration function.
604 static int fallback_migrate_page(struct address_space
*mapping
,
605 struct page
*newpage
, struct page
*page
, enum migrate_mode mode
)
607 if (PageDirty(page
)) {
608 /* Only writeback pages in full synchronous migration */
609 if (mode
!= MIGRATE_SYNC
)
611 return writeout(mapping
, page
);
615 * Buffers may be managed in a filesystem specific way.
616 * We must have no buffers or drop them.
618 if (page_has_private(page
) &&
619 !try_to_release_page(page
, GFP_KERNEL
))
622 return migrate_page(mapping
, newpage
, page
, mode
);
626 * Move a page to a newly allocated page
627 * The page is locked and all ptes have been successfully removed.
629 * The new page will have replaced the old page if this function
636 static int move_to_new_page(struct page
*newpage
, struct page
*page
,
637 int remap_swapcache
, enum migrate_mode mode
)
639 struct address_space
*mapping
;
643 * Block others from accessing the page when we get around to
644 * establishing additional references. We are the only one
645 * holding a reference to the new page at this point.
647 if (!trylock_page(newpage
))
650 /* Prepare mapping for the new page.*/
651 newpage
->index
= page
->index
;
652 newpage
->mapping
= page
->mapping
;
653 if (PageSwapBacked(page
))
654 SetPageSwapBacked(newpage
);
656 mapping
= page_mapping(page
);
658 rc
= migrate_page(mapping
, newpage
, page
, mode
);
659 else if (mapping
->a_ops
->migratepage
)
661 * Most pages have a mapping and most filesystems provide a
662 * migratepage callback. Anonymous pages are part of swap
663 * space which also has its own migratepage callback. This
664 * is the most common path for page migration.
666 rc
= mapping
->a_ops
->migratepage(mapping
,
667 newpage
, page
, mode
);
669 rc
= fallback_migrate_page(mapping
, newpage
, page
, mode
);
672 newpage
->mapping
= NULL
;
675 remove_migration_ptes(page
, newpage
);
676 page
->mapping
= NULL
;
679 unlock_page(newpage
);
684 static int __unmap_and_move(struct page
*page
, struct page
*newpage
,
685 int force
, bool offlining
, enum migrate_mode mode
)
688 int remap_swapcache
= 1;
689 struct mem_cgroup
*mem
;
690 struct anon_vma
*anon_vma
= NULL
;
692 if (!trylock_page(page
)) {
693 if (!force
|| mode
== MIGRATE_ASYNC
)
697 * It's not safe for direct compaction to call lock_page.
698 * For example, during page readahead pages are added locked
699 * to the LRU. Later, when the IO completes the pages are
700 * marked uptodate and unlocked. However, the queueing
701 * could be merging multiple pages for one bio (e.g.
702 * mpage_readpages). If an allocation happens for the
703 * second or third page, the process can end up locking
704 * the same page twice and deadlocking. Rather than
705 * trying to be clever about what pages can be locked,
706 * avoid the use of lock_page for direct compaction
709 if (current
->flags
& PF_MEMALLOC
)
716 * Only memory hotplug's offline_pages() caller has locked out KSM,
717 * and can safely migrate a KSM page. The other cases have skipped
718 * PageKsm along with PageReserved - but it is only now when we have
719 * the page lock that we can be certain it will not go KSM beneath us
720 * (KSM will not upgrade a page from PageAnon to PageKsm when it sees
721 * its pagecount raised, but only here do we take the page lock which
724 if (PageKsm(page
) && !offlining
) {
729 /* charge against new page */
730 mem_cgroup_prepare_migration(page
, newpage
, &mem
);
732 if (PageWriteback(page
)) {
734 * Only in the case of a full syncronous migration is it
735 * necessary to wait for PageWriteback. In the async case,
736 * the retry loop is too short and in the sync-light case,
737 * the overhead of stalling is too much
739 if (mode
!= MIGRATE_SYNC
) {
745 wait_on_page_writeback(page
);
748 * By try_to_unmap(), page->mapcount goes down to 0 here. In this case,
749 * we cannot notice that anon_vma is freed while we migrates a page.
750 * This get_anon_vma() delays freeing anon_vma pointer until the end
751 * of migration. File cache pages are no problem because of page_lock()
752 * File Caches may use write_page() or lock_page() in migration, then,
753 * just care Anon page here.
755 if (PageAnon(page
)) {
757 * Only page_lock_anon_vma() understands the subtleties of
758 * getting a hold on an anon_vma from outside one of its mms.
760 anon_vma
= page_get_anon_vma(page
);
765 } else if (PageSwapCache(page
)) {
767 * We cannot be sure that the anon_vma of an unmapped
768 * swapcache page is safe to use because we don't
769 * know in advance if the VMA that this page belonged
770 * to still exists. If the VMA and others sharing the
771 * data have been freed, then the anon_vma could
772 * already be invalid.
774 * To avoid this possibility, swapcache pages get
775 * migrated but are not remapped when migration
785 * Corner case handling:
786 * 1. When a new swap-cache page is read into, it is added to the LRU
787 * and treated as swapcache but it has no rmap yet.
788 * Calling try_to_unmap() against a page->mapping==NULL page will
789 * trigger a BUG. So handle it here.
790 * 2. An orphaned page (see truncate_complete_page) might have
791 * fs-private metadata. The page can be picked up due to memory
792 * offlining. Everywhere else except page reclaim, the page is
793 * invisible to the vm, so the page can not be migrated. So try to
794 * free the metadata, so the page can be freed.
796 if (!page
->mapping
) {
797 VM_BUG_ON(PageAnon(page
));
798 if (page_has_private(page
)) {
799 try_to_free_buffers(page
);
805 /* Establish migration ptes or remove ptes */
806 try_to_unmap(page
, TTU_MIGRATION
|TTU_IGNORE_MLOCK
|TTU_IGNORE_ACCESS
);
809 if (!page_mapped(page
))
810 rc
= move_to_new_page(newpage
, page
, remap_swapcache
, mode
);
812 if (rc
&& remap_swapcache
)
813 remove_migration_ptes(page
, page
);
815 /* Drop an anon_vma reference if we took one */
817 put_anon_vma(anon_vma
);
820 mem_cgroup_end_migration(mem
, page
, newpage
, rc
== 0);
828 * Obtain the lock on page, remove all ptes and migrate the page
829 * to the newly allocated page in newpage.
831 static int unmap_and_move(new_page_t get_new_page
, unsigned long private,
832 struct page
*page
, int force
, bool offlining
,
833 enum migrate_mode mode
)
837 struct page
*newpage
= get_new_page(page
, private, &result
);
842 if (page_count(page
) == 1) {
843 /* page was freed from under us. So we are done. */
847 if (unlikely(PageTransHuge(page
)))
848 if (unlikely(split_huge_page(page
)))
851 rc
= __unmap_and_move(page
, newpage
, force
, offlining
, mode
);
855 * A page that has been migrated has all references
856 * removed and will be freed. A page that has not been
857 * migrated will have kepts its references and be
860 list_del(&page
->lru
);
861 dec_zone_page_state(page
, NR_ISOLATED_ANON
+
862 page_is_file_cache(page
));
863 putback_lru_page(page
);
866 * Move the new page to the LRU. If migration was not successful
867 * then this will free the page.
869 putback_lru_page(newpage
);
874 *result
= page_to_nid(newpage
);
880 * Counterpart of unmap_and_move_page() for hugepage migration.
882 * This function doesn't wait the completion of hugepage I/O
883 * because there is no race between I/O and migration for hugepage.
884 * Note that currently hugepage I/O occurs only in direct I/O
885 * where no lock is held and PG_writeback is irrelevant,
886 * and writeback status of all subpages are counted in the reference
887 * count of the head page (i.e. if all subpages of a 2MB hugepage are
888 * under direct I/O, the reference of the head page is 512 and a bit more.)
889 * This means that when we try to migrate hugepage whose subpages are
890 * doing direct I/O, some references remain after try_to_unmap() and
891 * hugepage migration fails without data corruption.
893 * There is also no race when direct I/O is issued on the page under migration,
894 * because then pte is replaced with migration swap entry and direct I/O code
895 * will wait in the page fault for migration to complete.
897 static int unmap_and_move_huge_page(new_page_t get_new_page
,
898 unsigned long private, struct page
*hpage
,
899 int force
, bool offlining
,
900 enum migrate_mode mode
)
904 struct page
*new_hpage
= get_new_page(hpage
, private, &result
);
905 struct anon_vma
*anon_vma
= NULL
;
912 if (!trylock_page(hpage
)) {
913 if (!force
|| mode
!= MIGRATE_SYNC
)
919 anon_vma
= page_get_anon_vma(hpage
);
921 try_to_unmap(hpage
, TTU_MIGRATION
|TTU_IGNORE_MLOCK
|TTU_IGNORE_ACCESS
);
923 if (!page_mapped(hpage
))
924 rc
= move_to_new_page(new_hpage
, hpage
, 1, mode
);
927 remove_migration_ptes(hpage
, hpage
);
930 put_anon_vma(anon_vma
);
933 hugetlb_cgroup_migrate(hpage
, new_hpage
);
942 *result
= page_to_nid(new_hpage
);
950 * The function takes one list of pages to migrate and a function
951 * that determines from the page to be migrated and the private data
952 * the target of the move and allocates the page.
954 * The function returns after 10 attempts or if no pages
955 * are movable anymore because to has become empty
956 * or no retryable pages exist anymore.
957 * Caller should call putback_lru_pages to return pages to the LRU
958 * or free list only if ret != 0.
960 * Return: Number of pages not migrated or error code.
962 int migrate_pages(struct list_head
*from
,
963 new_page_t get_new_page
, unsigned long private, bool offlining
,
964 enum migrate_mode mode
, int reason
)
968 int nr_succeeded
= 0;
972 int swapwrite
= current
->flags
& PF_SWAPWRITE
;
976 current
->flags
|= PF_SWAPWRITE
;
978 for(pass
= 0; pass
< 10 && retry
; pass
++) {
981 list_for_each_entry_safe(page
, page2
, from
, lru
) {
984 rc
= unmap_and_move(get_new_page
, private,
985 page
, pass
> 2, offlining
,
998 /* Permanent failure */
1007 count_vm_events(PGMIGRATE_SUCCESS
, nr_succeeded
);
1009 count_vm_events(PGMIGRATE_FAIL
, nr_failed
);
1010 trace_mm_migrate_pages(nr_succeeded
, nr_failed
, mode
, reason
);
1013 current
->flags
&= ~PF_SWAPWRITE
;
1018 return nr_failed
+ retry
;
1021 int migrate_huge_page(struct page
*hpage
, new_page_t get_new_page
,
1022 unsigned long private, bool offlining
,
1023 enum migrate_mode mode
)
1027 for (pass
= 0; pass
< 10; pass
++) {
1028 rc
= unmap_and_move_huge_page(get_new_page
,
1029 private, hpage
, pass
> 2, offlining
,
1051 * Move a list of individual pages
1053 struct page_to_node
{
1060 static struct page
*new_page_node(struct page
*p
, unsigned long private,
1063 struct page_to_node
*pm
= (struct page_to_node
*)private;
1065 while (pm
->node
!= MAX_NUMNODES
&& pm
->page
!= p
)
1068 if (pm
->node
== MAX_NUMNODES
)
1071 *result
= &pm
->status
;
1073 return alloc_pages_exact_node(pm
->node
,
1074 GFP_HIGHUSER_MOVABLE
| GFP_THISNODE
, 0);
1078 * Move a set of pages as indicated in the pm array. The addr
1079 * field must be set to the virtual address of the page to be moved
1080 * and the node number must contain a valid target node.
1081 * The pm array ends with node = MAX_NUMNODES.
1083 static int do_move_page_to_node_array(struct mm_struct
*mm
,
1084 struct page_to_node
*pm
,
1088 struct page_to_node
*pp
;
1089 LIST_HEAD(pagelist
);
1091 down_read(&mm
->mmap_sem
);
1094 * Build a list of pages to migrate
1096 for (pp
= pm
; pp
->node
!= MAX_NUMNODES
; pp
++) {
1097 struct vm_area_struct
*vma
;
1101 vma
= find_vma(mm
, pp
->addr
);
1102 if (!vma
|| pp
->addr
< vma
->vm_start
|| !vma_migratable(vma
))
1105 page
= follow_page(vma
, pp
->addr
, FOLL_GET
|FOLL_SPLIT
);
1107 err
= PTR_ERR(page
);
1115 /* Use PageReserved to check for zero page */
1116 if (PageReserved(page
) || PageKsm(page
))
1120 err
= page_to_nid(page
);
1122 if (err
== pp
->node
)
1124 * Node already in the right place
1129 if (page_mapcount(page
) > 1 &&
1133 err
= isolate_lru_page(page
);
1135 list_add_tail(&page
->lru
, &pagelist
);
1136 inc_zone_page_state(page
, NR_ISOLATED_ANON
+
1137 page_is_file_cache(page
));
1141 * Either remove the duplicate refcount from
1142 * isolate_lru_page() or drop the page ref if it was
1151 if (!list_empty(&pagelist
)) {
1152 err
= migrate_pages(&pagelist
, new_page_node
,
1153 (unsigned long)pm
, 0, MIGRATE_SYNC
,
1156 putback_lru_pages(&pagelist
);
1159 up_read(&mm
->mmap_sem
);
1164 * Migrate an array of page address onto an array of nodes and fill
1165 * the corresponding array of status.
1167 static int do_pages_move(struct mm_struct
*mm
, nodemask_t task_nodes
,
1168 unsigned long nr_pages
,
1169 const void __user
* __user
*pages
,
1170 const int __user
*nodes
,
1171 int __user
*status
, int flags
)
1173 struct page_to_node
*pm
;
1174 unsigned long chunk_nr_pages
;
1175 unsigned long chunk_start
;
1179 pm
= (struct page_to_node
*)__get_free_page(GFP_KERNEL
);
1186 * Store a chunk of page_to_node array in a page,
1187 * but keep the last one as a marker
1189 chunk_nr_pages
= (PAGE_SIZE
/ sizeof(struct page_to_node
)) - 1;
1191 for (chunk_start
= 0;
1192 chunk_start
< nr_pages
;
1193 chunk_start
+= chunk_nr_pages
) {
1196 if (chunk_start
+ chunk_nr_pages
> nr_pages
)
1197 chunk_nr_pages
= nr_pages
- chunk_start
;
1199 /* fill the chunk pm with addrs and nodes from user-space */
1200 for (j
= 0; j
< chunk_nr_pages
; j
++) {
1201 const void __user
*p
;
1205 if (get_user(p
, pages
+ j
+ chunk_start
))
1207 pm
[j
].addr
= (unsigned long) p
;
1209 if (get_user(node
, nodes
+ j
+ chunk_start
))
1213 if (node
< 0 || node
>= MAX_NUMNODES
)
1216 if (!node_state(node
, N_HIGH_MEMORY
))
1220 if (!node_isset(node
, task_nodes
))
1226 /* End marker for this chunk */
1227 pm
[chunk_nr_pages
].node
= MAX_NUMNODES
;
1229 /* Migrate this chunk */
1230 err
= do_move_page_to_node_array(mm
, pm
,
1231 flags
& MPOL_MF_MOVE_ALL
);
1235 /* Return status information */
1236 for (j
= 0; j
< chunk_nr_pages
; j
++)
1237 if (put_user(pm
[j
].status
, status
+ j
+ chunk_start
)) {
1245 free_page((unsigned long)pm
);
1251 * Determine the nodes of an array of pages and store it in an array of status.
1253 static void do_pages_stat_array(struct mm_struct
*mm
, unsigned long nr_pages
,
1254 const void __user
**pages
, int *status
)
1258 down_read(&mm
->mmap_sem
);
1260 for (i
= 0; i
< nr_pages
; i
++) {
1261 unsigned long addr
= (unsigned long)(*pages
);
1262 struct vm_area_struct
*vma
;
1266 vma
= find_vma(mm
, addr
);
1267 if (!vma
|| addr
< vma
->vm_start
)
1270 page
= follow_page(vma
, addr
, 0);
1272 err
= PTR_ERR(page
);
1277 /* Use PageReserved to check for zero page */
1278 if (!page
|| PageReserved(page
) || PageKsm(page
))
1281 err
= page_to_nid(page
);
1289 up_read(&mm
->mmap_sem
);
1293 * Determine the nodes of a user array of pages and store it in
1294 * a user array of status.
1296 static int do_pages_stat(struct mm_struct
*mm
, unsigned long nr_pages
,
1297 const void __user
* __user
*pages
,
1300 #define DO_PAGES_STAT_CHUNK_NR 16
1301 const void __user
*chunk_pages
[DO_PAGES_STAT_CHUNK_NR
];
1302 int chunk_status
[DO_PAGES_STAT_CHUNK_NR
];
1305 unsigned long chunk_nr
;
1307 chunk_nr
= nr_pages
;
1308 if (chunk_nr
> DO_PAGES_STAT_CHUNK_NR
)
1309 chunk_nr
= DO_PAGES_STAT_CHUNK_NR
;
1311 if (copy_from_user(chunk_pages
, pages
, chunk_nr
* sizeof(*chunk_pages
)))
1314 do_pages_stat_array(mm
, chunk_nr
, chunk_pages
, chunk_status
);
1316 if (copy_to_user(status
, chunk_status
, chunk_nr
* sizeof(*status
)))
1321 nr_pages
-= chunk_nr
;
1323 return nr_pages
? -EFAULT
: 0;
1327 * Move a list of pages in the address space of the currently executing
1330 SYSCALL_DEFINE6(move_pages
, pid_t
, pid
, unsigned long, nr_pages
,
1331 const void __user
* __user
*, pages
,
1332 const int __user
*, nodes
,
1333 int __user
*, status
, int, flags
)
1335 const struct cred
*cred
= current_cred(), *tcred
;
1336 struct task_struct
*task
;
1337 struct mm_struct
*mm
;
1339 nodemask_t task_nodes
;
1342 if (flags
& ~(MPOL_MF_MOVE
|MPOL_MF_MOVE_ALL
))
1345 if ((flags
& MPOL_MF_MOVE_ALL
) && !capable(CAP_SYS_NICE
))
1348 /* Find the mm_struct */
1350 task
= pid
? find_task_by_vpid(pid
) : current
;
1355 get_task_struct(task
);
1358 * Check if this process has the right to modify the specified
1359 * process. The right exists if the process has administrative
1360 * capabilities, superuser privileges or the same
1361 * userid as the target process.
1363 tcred
= __task_cred(task
);
1364 if (!uid_eq(cred
->euid
, tcred
->suid
) && !uid_eq(cred
->euid
, tcred
->uid
) &&
1365 !uid_eq(cred
->uid
, tcred
->suid
) && !uid_eq(cred
->uid
, tcred
->uid
) &&
1366 !capable(CAP_SYS_NICE
)) {
1373 err
= security_task_movememory(task
);
1377 task_nodes
= cpuset_mems_allowed(task
);
1378 mm
= get_task_mm(task
);
1379 put_task_struct(task
);
1385 err
= do_pages_move(mm
, task_nodes
, nr_pages
, pages
,
1386 nodes
, status
, flags
);
1388 err
= do_pages_stat(mm
, nr_pages
, pages
, status
);
1394 put_task_struct(task
);
1399 * Call migration functions in the vma_ops that may prepare
1400 * memory in a vm for migration. migration functions may perform
1401 * the migration for vmas that do not have an underlying page struct.
1403 int migrate_vmas(struct mm_struct
*mm
, const nodemask_t
*to
,
1404 const nodemask_t
*from
, unsigned long flags
)
1406 struct vm_area_struct
*vma
;
1409 for (vma
= mm
->mmap
; vma
&& !err
; vma
= vma
->vm_next
) {
1410 if (vma
->vm_ops
&& vma
->vm_ops
->migrate
) {
1411 err
= vma
->vm_ops
->migrate(vma
, to
, from
, flags
);
1419 #ifdef CONFIG_NUMA_BALANCING
1421 * Returns true if this is a safe migration target node for misplaced NUMA
1422 * pages. Currently it only checks the watermarks which crude
1424 static bool migrate_balanced_pgdat(struct pglist_data
*pgdat
,
1425 int nr_migrate_pages
)
1428 for (z
= pgdat
->nr_zones
- 1; z
>= 0; z
--) {
1429 struct zone
*zone
= pgdat
->node_zones
+ z
;
1431 if (!populated_zone(zone
))
1434 if (zone
->all_unreclaimable
)
1437 /* Avoid waking kswapd by allocating pages_to_migrate pages. */
1438 if (!zone_watermark_ok(zone
, 0,
1439 high_wmark_pages(zone
) +
1448 static struct page
*alloc_misplaced_dst_page(struct page
*page
,
1452 int nid
= (int) data
;
1453 struct page
*newpage
;
1455 newpage
= alloc_pages_exact_node(nid
,
1456 (GFP_HIGHUSER_MOVABLE
| GFP_THISNODE
|
1457 __GFP_NOMEMALLOC
| __GFP_NORETRY
|
1464 * Attempt to migrate a misplaced page to the specified destination
1465 * node. Caller is expected to have an elevated reference count on
1466 * the page that will be dropped by this function before returning.
1468 int migrate_misplaced_page(struct page
*page
, int node
)
1471 LIST_HEAD(migratepages
);
1474 * Don't migrate pages that are mapped in multiple processes.
1475 * TODO: Handle false sharing detection instead of this hammer
1477 if (page_mapcount(page
) != 1) {
1482 /* Avoid migrating to a node that is nearly full */
1483 if (migrate_balanced_pgdat(NODE_DATA(node
), 1)) {
1486 if (isolate_lru_page(page
)) {
1492 page_lru
= page_is_file_cache(page
);
1493 inc_zone_page_state(page
, NR_ISOLATED_ANON
+ page_lru
);
1494 list_add(&page
->lru
, &migratepages
);
1498 * Page is either isolated or there is not enough space on the target
1499 * node. If isolated, then it has taken a reference count and the
1500 * callers reference can be safely dropped without the page
1501 * disappearing underneath us during migration. Otherwise the page is
1502 * not to be migrated but the callers reference should still be
1503 * dropped so it does not leak.
1510 nr_remaining
= migrate_pages(&migratepages
,
1511 alloc_misplaced_dst_page
,
1512 node
, false, MIGRATE_ASYNC
,
1515 putback_lru_pages(&migratepages
);
1518 count_vm_numa_event(NUMA_PAGE_MIGRATE
);
1520 BUG_ON(!list_empty(&migratepages
));
1524 #endif /* CONFIG_NUMA_BALANCING */
1526 #endif /* CONFIG_NUMA */
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