2 * Memory Migration functionality - linux/mm/migrate.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/backing-dev.h>
34 #include <linux/compaction.h>
35 #include <linux/syscalls.h>
36 #include <linux/hugetlb.h>
37 #include <linux/hugetlb_cgroup.h>
38 #include <linux/gfp.h>
39 #include <linux/balloon_compaction.h>
40 #include <linux/mmu_notifier.h>
41 #include <linux/page_idle.h>
42 #include <linux/page_owner.h>
43 #include <linux/sched/mm.h>
45 #include <asm/tlbflush.h>
47 #define CREATE_TRACE_POINTS
48 #include <trace/events/migrate.h>
53 * migrate_prep() needs to be called before we start compiling a list of pages
54 * to be migrated using isolate_lru_page(). If scheduling work on other CPUs is
55 * undesirable, use migrate_prep_local()
57 int migrate_prep(void)
60 * Clear the LRU lists so pages can be isolated.
61 * Note that pages may be moved off the LRU after we have
62 * drained them. Those pages will fail to migrate like other
63 * pages that may be busy.
70 /* Do the necessary work of migrate_prep but not if it involves other CPUs */
71 int migrate_prep_local(void)
78 int isolate_movable_page(struct page
*page
, isolate_mode_t mode
)
80 struct address_space
*mapping
;
83 * Avoid burning cycles with pages that are yet under __free_pages(),
84 * or just got freed under us.
86 * In case we 'win' a race for a movable page being freed under us and
87 * raise its refcount preventing __free_pages() from doing its job
88 * the put_page() at the end of this block will take care of
89 * release this page, thus avoiding a nasty leakage.
91 if (unlikely(!get_page_unless_zero(page
)))
95 * Check PageMovable before holding a PG_lock because page's owner
96 * assumes anybody doesn't touch PG_lock of newly allocated page
97 * so unconditionally grapping the lock ruins page's owner side.
99 if (unlikely(!__PageMovable(page
)))
102 * As movable pages are not isolated from LRU lists, concurrent
103 * compaction threads can race against page migration functions
104 * as well as race against the releasing a page.
106 * In order to avoid having an already isolated movable page
107 * being (wrongly) re-isolated while it is under migration,
108 * or to avoid attempting to isolate pages being released,
109 * lets be sure we have the page lock
110 * before proceeding with the movable page isolation steps.
112 if (unlikely(!trylock_page(page
)))
115 if (!PageMovable(page
) || PageIsolated(page
))
116 goto out_no_isolated
;
118 mapping
= page_mapping(page
);
119 VM_BUG_ON_PAGE(!mapping
, page
);
121 if (!mapping
->a_ops
->isolate_page(page
, mode
))
122 goto out_no_isolated
;
124 /* Driver shouldn't use PG_isolated bit of page->flags */
125 WARN_ON_ONCE(PageIsolated(page
));
126 __SetPageIsolated(page
);
139 /* It should be called on page which is PG_movable */
140 void putback_movable_page(struct page
*page
)
142 struct address_space
*mapping
;
144 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
145 VM_BUG_ON_PAGE(!PageMovable(page
), page
);
146 VM_BUG_ON_PAGE(!PageIsolated(page
), page
);
148 mapping
= page_mapping(page
);
149 mapping
->a_ops
->putback_page(page
);
150 __ClearPageIsolated(page
);
154 * Put previously isolated pages back onto the appropriate lists
155 * from where they were once taken off for compaction/migration.
157 * This function shall be used whenever the isolated pageset has been
158 * built from lru, balloon, hugetlbfs page. See isolate_migratepages_range()
159 * and isolate_huge_page().
161 void putback_movable_pages(struct list_head
*l
)
166 list_for_each_entry_safe(page
, page2
, l
, lru
) {
167 if (unlikely(PageHuge(page
))) {
168 putback_active_hugepage(page
);
171 list_del(&page
->lru
);
173 * We isolated non-lru movable page so here we can use
174 * __PageMovable because LRU page's mapping cannot have
175 * PAGE_MAPPING_MOVABLE.
177 if (unlikely(__PageMovable(page
))) {
178 VM_BUG_ON_PAGE(!PageIsolated(page
), page
);
180 if (PageMovable(page
))
181 putback_movable_page(page
);
183 __ClearPageIsolated(page
);
187 dec_node_page_state(page
, NR_ISOLATED_ANON
+
188 page_is_file_cache(page
));
189 putback_lru_page(page
);
195 * Restore a potential migration pte to a working pte entry
197 static bool remove_migration_pte(struct page
*page
, struct vm_area_struct
*vma
,
198 unsigned long addr
, void *old
)
200 struct page_vma_mapped_walk pvmw
= {
204 .flags
= PVMW_SYNC
| PVMW_MIGRATION
,
210 VM_BUG_ON_PAGE(PageTail(page
), page
);
211 while (page_vma_mapped_walk(&pvmw
)) {
215 new = page
- pvmw
.page
->index
+
216 linear_page_index(vma
, pvmw
.address
);
219 pte
= pte_mkold(mk_pte(new, READ_ONCE(vma
->vm_page_prot
)));
220 if (pte_swp_soft_dirty(*pvmw
.pte
))
221 pte
= pte_mksoft_dirty(pte
);
224 * Recheck VMA as permissions can change since migration started
226 entry
= pte_to_swp_entry(*pvmw
.pte
);
227 if (is_write_migration_entry(entry
))
228 pte
= maybe_mkwrite(pte
, vma
);
230 flush_dcache_page(new);
231 #ifdef CONFIG_HUGETLB_PAGE
233 pte
= pte_mkhuge(pte
);
234 pte
= arch_make_huge_pte(pte
, vma
, new, 0);
235 set_huge_pte_at(vma
->vm_mm
, pvmw
.address
, pvmw
.pte
, pte
);
237 hugepage_add_anon_rmap(new, vma
, pvmw
.address
);
239 page_dup_rmap(new, true);
243 set_pte_at(vma
->vm_mm
, pvmw
.address
, pvmw
.pte
, pte
);
246 page_add_anon_rmap(new, vma
, pvmw
.address
, false);
248 page_add_file_rmap(new, false);
250 if (vma
->vm_flags
& VM_LOCKED
&& !PageTransCompound(new))
253 /* No need to invalidate - it was non-present before */
254 update_mmu_cache(vma
, pvmw
.address
, pvmw
.pte
);
261 * Get rid of all migration entries and replace them by
262 * references to the indicated page.
264 void remove_migration_ptes(struct page
*old
, struct page
*new, bool locked
)
266 struct rmap_walk_control rwc
= {
267 .rmap_one
= remove_migration_pte
,
272 rmap_walk_locked(new, &rwc
);
274 rmap_walk(new, &rwc
);
278 * Something used the pte of a page under migration. We need to
279 * get to the page and wait until migration is finished.
280 * When we return from this function the fault will be retried.
282 void __migration_entry_wait(struct mm_struct
*mm
, pte_t
*ptep
,
291 if (!is_swap_pte(pte
))
294 entry
= pte_to_swp_entry(pte
);
295 if (!is_migration_entry(entry
))
298 page
= migration_entry_to_page(entry
);
301 * Once radix-tree replacement of page migration started, page_count
302 * *must* be zero. And, we don't want to call wait_on_page_locked()
303 * against a page without get_page().
304 * So, we use get_page_unless_zero(), here. Even failed, page fault
307 if (!get_page_unless_zero(page
))
309 pte_unmap_unlock(ptep
, ptl
);
310 wait_on_page_locked(page
);
314 pte_unmap_unlock(ptep
, ptl
);
317 void migration_entry_wait(struct mm_struct
*mm
, pmd_t
*pmd
,
318 unsigned long address
)
320 spinlock_t
*ptl
= pte_lockptr(mm
, pmd
);
321 pte_t
*ptep
= pte_offset_map(pmd
, address
);
322 __migration_entry_wait(mm
, ptep
, ptl
);
325 void migration_entry_wait_huge(struct vm_area_struct
*vma
,
326 struct mm_struct
*mm
, pte_t
*pte
)
328 spinlock_t
*ptl
= huge_pte_lockptr(hstate_vma(vma
), mm
, pte
);
329 __migration_entry_wait(mm
, pte
, ptl
);
333 /* Returns true if all buffers are successfully locked */
334 static bool buffer_migrate_lock_buffers(struct buffer_head
*head
,
335 enum migrate_mode mode
)
337 struct buffer_head
*bh
= head
;
339 /* Simple case, sync compaction */
340 if (mode
!= MIGRATE_ASYNC
) {
344 bh
= bh
->b_this_page
;
346 } while (bh
!= head
);
351 /* async case, we cannot block on lock_buffer so use trylock_buffer */
354 if (!trylock_buffer(bh
)) {
356 * We failed to lock the buffer and cannot stall in
357 * async migration. Release the taken locks
359 struct buffer_head
*failed_bh
= bh
;
362 while (bh
!= failed_bh
) {
365 bh
= bh
->b_this_page
;
370 bh
= bh
->b_this_page
;
371 } while (bh
!= head
);
375 static inline bool buffer_migrate_lock_buffers(struct buffer_head
*head
,
376 enum migrate_mode mode
)
380 #endif /* CONFIG_BLOCK */
383 * Replace the page in the mapping.
385 * The number of remaining references must be:
386 * 1 for anonymous pages without a mapping
387 * 2 for pages with a mapping
388 * 3 for pages with a mapping and PagePrivate/PagePrivate2 set.
390 int migrate_page_move_mapping(struct address_space
*mapping
,
391 struct page
*newpage
, struct page
*page
,
392 struct buffer_head
*head
, enum migrate_mode mode
,
395 struct zone
*oldzone
, *newzone
;
397 int expected_count
= 1 + extra_count
;
401 /* Anonymous page without mapping */
402 if (page_count(page
) != expected_count
)
405 /* No turning back from here */
406 newpage
->index
= page
->index
;
407 newpage
->mapping
= page
->mapping
;
408 if (PageSwapBacked(page
))
409 __SetPageSwapBacked(newpage
);
411 return MIGRATEPAGE_SUCCESS
;
414 oldzone
= page_zone(page
);
415 newzone
= page_zone(newpage
);
417 spin_lock_irq(&mapping
->tree_lock
);
419 pslot
= radix_tree_lookup_slot(&mapping
->page_tree
,
422 expected_count
+= 1 + page_has_private(page
);
423 if (page_count(page
) != expected_count
||
424 radix_tree_deref_slot_protected(pslot
, &mapping
->tree_lock
) != page
) {
425 spin_unlock_irq(&mapping
->tree_lock
);
429 if (!page_ref_freeze(page
, expected_count
)) {
430 spin_unlock_irq(&mapping
->tree_lock
);
435 * In the async migration case of moving a page with buffers, lock the
436 * buffers using trylock before the mapping is moved. If the mapping
437 * was moved, we later failed to lock the buffers and could not move
438 * the mapping back due to an elevated page count, we would have to
439 * block waiting on other references to be dropped.
441 if (mode
== MIGRATE_ASYNC
&& head
&&
442 !buffer_migrate_lock_buffers(head
, mode
)) {
443 page_ref_unfreeze(page
, expected_count
);
444 spin_unlock_irq(&mapping
->tree_lock
);
449 * Now we know that no one else is looking at the page:
450 * no turning back from here.
452 newpage
->index
= page
->index
;
453 newpage
->mapping
= page
->mapping
;
454 get_page(newpage
); /* add cache reference */
455 if (PageSwapBacked(page
)) {
456 __SetPageSwapBacked(newpage
);
457 if (PageSwapCache(page
)) {
458 SetPageSwapCache(newpage
);
459 set_page_private(newpage
, page_private(page
));
462 VM_BUG_ON_PAGE(PageSwapCache(page
), page
);
465 /* Move dirty while page refs frozen and newpage not yet exposed */
466 dirty
= PageDirty(page
);
468 ClearPageDirty(page
);
469 SetPageDirty(newpage
);
472 radix_tree_replace_slot(&mapping
->page_tree
, pslot
, newpage
);
475 * Drop cache reference from old page by unfreezing
476 * to one less reference.
477 * We know this isn't the last reference.
479 page_ref_unfreeze(page
, expected_count
- 1);
481 spin_unlock(&mapping
->tree_lock
);
482 /* Leave irq disabled to prevent preemption while updating stats */
485 * If moved to a different zone then also account
486 * the page for that zone. Other VM counters will be
487 * taken care of when we establish references to the
488 * new page and drop references to the old page.
490 * Note that anonymous pages are accounted for
491 * via NR_FILE_PAGES and NR_ANON_MAPPED if they
492 * are mapped to swap space.
494 if (newzone
!= oldzone
) {
495 __dec_node_state(oldzone
->zone_pgdat
, NR_FILE_PAGES
);
496 __inc_node_state(newzone
->zone_pgdat
, NR_FILE_PAGES
);
497 if (PageSwapBacked(page
) && !PageSwapCache(page
)) {
498 __dec_node_state(oldzone
->zone_pgdat
, NR_SHMEM
);
499 __inc_node_state(newzone
->zone_pgdat
, NR_SHMEM
);
501 if (dirty
&& mapping_cap_account_dirty(mapping
)) {
502 __dec_node_state(oldzone
->zone_pgdat
, NR_FILE_DIRTY
);
503 __dec_zone_state(oldzone
, NR_ZONE_WRITE_PENDING
);
504 __inc_node_state(newzone
->zone_pgdat
, NR_FILE_DIRTY
);
505 __inc_zone_state(newzone
, NR_ZONE_WRITE_PENDING
);
510 return MIGRATEPAGE_SUCCESS
;
512 EXPORT_SYMBOL(migrate_page_move_mapping
);
515 * The expected number of remaining references is the same as that
516 * of migrate_page_move_mapping().
518 int migrate_huge_page_move_mapping(struct address_space
*mapping
,
519 struct page
*newpage
, struct page
*page
)
524 spin_lock_irq(&mapping
->tree_lock
);
526 pslot
= radix_tree_lookup_slot(&mapping
->page_tree
,
529 expected_count
= 2 + page_has_private(page
);
530 if (page_count(page
) != expected_count
||
531 radix_tree_deref_slot_protected(pslot
, &mapping
->tree_lock
) != page
) {
532 spin_unlock_irq(&mapping
->tree_lock
);
536 if (!page_ref_freeze(page
, expected_count
)) {
537 spin_unlock_irq(&mapping
->tree_lock
);
541 newpage
->index
= page
->index
;
542 newpage
->mapping
= page
->mapping
;
546 radix_tree_replace_slot(&mapping
->page_tree
, pslot
, newpage
);
548 page_ref_unfreeze(page
, expected_count
- 1);
550 spin_unlock_irq(&mapping
->tree_lock
);
552 return MIGRATEPAGE_SUCCESS
;
556 * Gigantic pages are so large that we do not guarantee that page++ pointer
557 * arithmetic will work across the entire page. We need something more
560 static void __copy_gigantic_page(struct page
*dst
, struct page
*src
,
564 struct page
*dst_base
= dst
;
565 struct page
*src_base
= src
;
567 for (i
= 0; i
< nr_pages
; ) {
569 copy_highpage(dst
, src
);
572 dst
= mem_map_next(dst
, dst_base
, i
);
573 src
= mem_map_next(src
, src_base
, i
);
577 static void copy_huge_page(struct page
*dst
, struct page
*src
)
584 struct hstate
*h
= page_hstate(src
);
585 nr_pages
= pages_per_huge_page(h
);
587 if (unlikely(nr_pages
> MAX_ORDER_NR_PAGES
)) {
588 __copy_gigantic_page(dst
, src
, nr_pages
);
593 BUG_ON(!PageTransHuge(src
));
594 nr_pages
= hpage_nr_pages(src
);
597 for (i
= 0; i
< nr_pages
; i
++) {
599 copy_highpage(dst
+ i
, src
+ i
);
604 * Copy the page to its new location
606 void migrate_page_copy(struct page
*newpage
, struct page
*page
)
610 if (PageHuge(page
) || PageTransHuge(page
))
611 copy_huge_page(newpage
, page
);
613 copy_highpage(newpage
, page
);
616 SetPageError(newpage
);
617 if (PageReferenced(page
))
618 SetPageReferenced(newpage
);
619 if (PageUptodate(page
))
620 SetPageUptodate(newpage
);
621 if (TestClearPageActive(page
)) {
622 VM_BUG_ON_PAGE(PageUnevictable(page
), page
);
623 SetPageActive(newpage
);
624 } else if (TestClearPageUnevictable(page
))
625 SetPageUnevictable(newpage
);
626 if (PageChecked(page
))
627 SetPageChecked(newpage
);
628 if (PageMappedToDisk(page
))
629 SetPageMappedToDisk(newpage
);
631 /* Move dirty on pages not done by migrate_page_move_mapping() */
633 SetPageDirty(newpage
);
635 if (page_is_young(page
))
636 set_page_young(newpage
);
637 if (page_is_idle(page
))
638 set_page_idle(newpage
);
641 * Copy NUMA information to the new page, to prevent over-eager
642 * future migrations of this same page.
644 cpupid
= page_cpupid_xchg_last(page
, -1);
645 page_cpupid_xchg_last(newpage
, cpupid
);
647 ksm_migrate_page(newpage
, page
);
649 * Please do not reorder this without considering how mm/ksm.c's
650 * get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache().
652 if (PageSwapCache(page
))
653 ClearPageSwapCache(page
);
654 ClearPagePrivate(page
);
655 set_page_private(page
, 0);
658 * If any waiters have accumulated on the new page then
661 if (PageWriteback(newpage
))
662 end_page_writeback(newpage
);
664 copy_page_owner(page
, newpage
);
666 mem_cgroup_migrate(page
, newpage
);
668 EXPORT_SYMBOL(migrate_page_copy
);
670 /************************************************************
671 * Migration functions
672 ***********************************************************/
675 * Common logic to directly migrate a single LRU page suitable for
676 * pages that do not use PagePrivate/PagePrivate2.
678 * Pages are locked upon entry and exit.
680 int migrate_page(struct address_space
*mapping
,
681 struct page
*newpage
, struct page
*page
,
682 enum migrate_mode mode
)
686 BUG_ON(PageWriteback(page
)); /* Writeback must be complete */
688 rc
= migrate_page_move_mapping(mapping
, newpage
, page
, NULL
, mode
, 0);
690 if (rc
!= MIGRATEPAGE_SUCCESS
)
693 migrate_page_copy(newpage
, page
);
694 return MIGRATEPAGE_SUCCESS
;
696 EXPORT_SYMBOL(migrate_page
);
700 * Migration function for pages with buffers. This function can only be used
701 * if the underlying filesystem guarantees that no other references to "page"
704 int buffer_migrate_page(struct address_space
*mapping
,
705 struct page
*newpage
, struct page
*page
, enum migrate_mode mode
)
707 struct buffer_head
*bh
, *head
;
710 if (!page_has_buffers(page
))
711 return migrate_page(mapping
, newpage
, page
, mode
);
713 head
= page_buffers(page
);
715 rc
= migrate_page_move_mapping(mapping
, newpage
, page
, head
, mode
, 0);
717 if (rc
!= MIGRATEPAGE_SUCCESS
)
721 * In the async case, migrate_page_move_mapping locked the buffers
722 * with an IRQ-safe spinlock held. In the sync case, the buffers
723 * need to be locked now
725 if (mode
!= MIGRATE_ASYNC
)
726 BUG_ON(!buffer_migrate_lock_buffers(head
, mode
));
728 ClearPagePrivate(page
);
729 set_page_private(newpage
, page_private(page
));
730 set_page_private(page
, 0);
736 set_bh_page(bh
, newpage
, bh_offset(bh
));
737 bh
= bh
->b_this_page
;
739 } while (bh
!= head
);
741 SetPagePrivate(newpage
);
743 migrate_page_copy(newpage
, page
);
749 bh
= bh
->b_this_page
;
751 } while (bh
!= head
);
753 return MIGRATEPAGE_SUCCESS
;
755 EXPORT_SYMBOL(buffer_migrate_page
);
759 * Writeback a page to clean the dirty state
761 static int writeout(struct address_space
*mapping
, struct page
*page
)
763 struct writeback_control wbc
= {
764 .sync_mode
= WB_SYNC_NONE
,
767 .range_end
= LLONG_MAX
,
772 if (!mapping
->a_ops
->writepage
)
773 /* No write method for the address space */
776 if (!clear_page_dirty_for_io(page
))
777 /* Someone else already triggered a write */
781 * A dirty page may imply that the underlying filesystem has
782 * the page on some queue. So the page must be clean for
783 * migration. Writeout may mean we loose the lock and the
784 * page state is no longer what we checked for earlier.
785 * At this point we know that the migration attempt cannot
788 remove_migration_ptes(page
, page
, false);
790 rc
= mapping
->a_ops
->writepage(page
, &wbc
);
792 if (rc
!= AOP_WRITEPAGE_ACTIVATE
)
793 /* unlocked. Relock */
796 return (rc
< 0) ? -EIO
: -EAGAIN
;
800 * Default handling if a filesystem does not provide a migration function.
802 static int fallback_migrate_page(struct address_space
*mapping
,
803 struct page
*newpage
, struct page
*page
, enum migrate_mode mode
)
805 if (PageDirty(page
)) {
806 /* Only writeback pages in full synchronous migration */
807 if (mode
!= MIGRATE_SYNC
)
809 return writeout(mapping
, page
);
813 * Buffers may be managed in a filesystem specific way.
814 * We must have no buffers or drop them.
816 if (page_has_private(page
) &&
817 !try_to_release_page(page
, GFP_KERNEL
))
820 return migrate_page(mapping
, newpage
, page
, mode
);
824 * Move a page to a newly allocated page
825 * The page is locked and all ptes have been successfully removed.
827 * The new page will have replaced the old page if this function
832 * MIGRATEPAGE_SUCCESS - success
834 static int move_to_new_page(struct page
*newpage
, struct page
*page
,
835 enum migrate_mode mode
)
837 struct address_space
*mapping
;
839 bool is_lru
= !__PageMovable(page
);
841 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
842 VM_BUG_ON_PAGE(!PageLocked(newpage
), newpage
);
844 mapping
= page_mapping(page
);
846 if (likely(is_lru
)) {
848 rc
= migrate_page(mapping
, newpage
, page
, mode
);
849 else if (mapping
->a_ops
->migratepage
)
851 * Most pages have a mapping and most filesystems
852 * provide a migratepage callback. Anonymous pages
853 * are part of swap space which also has its own
854 * migratepage callback. This is the most common path
855 * for page migration.
857 rc
= mapping
->a_ops
->migratepage(mapping
, newpage
,
860 rc
= fallback_migrate_page(mapping
, newpage
,
864 * In case of non-lru page, it could be released after
865 * isolation step. In that case, we shouldn't try migration.
867 VM_BUG_ON_PAGE(!PageIsolated(page
), page
);
868 if (!PageMovable(page
)) {
869 rc
= MIGRATEPAGE_SUCCESS
;
870 __ClearPageIsolated(page
);
874 rc
= mapping
->a_ops
->migratepage(mapping
, newpage
,
876 WARN_ON_ONCE(rc
== MIGRATEPAGE_SUCCESS
&&
877 !PageIsolated(page
));
881 * When successful, old pagecache page->mapping must be cleared before
882 * page is freed; but stats require that PageAnon be left as PageAnon.
884 if (rc
== MIGRATEPAGE_SUCCESS
) {
885 if (__PageMovable(page
)) {
886 VM_BUG_ON_PAGE(!PageIsolated(page
), page
);
889 * We clear PG_movable under page_lock so any compactor
890 * cannot try to migrate this page.
892 __ClearPageIsolated(page
);
896 * Anonymous and movable page->mapping will be cleard by
897 * free_pages_prepare so don't reset it here for keeping
898 * the type to work PageAnon, for example.
900 if (!PageMappingFlags(page
))
901 page
->mapping
= NULL
;
907 static int __unmap_and_move(struct page
*page
, struct page
*newpage
,
908 int force
, enum migrate_mode mode
)
911 int page_was_mapped
= 0;
912 struct anon_vma
*anon_vma
= NULL
;
913 bool is_lru
= !__PageMovable(page
);
915 if (!trylock_page(page
)) {
916 if (!force
|| mode
== MIGRATE_ASYNC
)
920 * It's not safe for direct compaction to call lock_page.
921 * For example, during page readahead pages are added locked
922 * to the LRU. Later, when the IO completes the pages are
923 * marked uptodate and unlocked. However, the queueing
924 * could be merging multiple pages for one bio (e.g.
925 * mpage_readpages). If an allocation happens for the
926 * second or third page, the process can end up locking
927 * the same page twice and deadlocking. Rather than
928 * trying to be clever about what pages can be locked,
929 * avoid the use of lock_page for direct compaction
932 if (current
->flags
& PF_MEMALLOC
)
938 if (PageWriteback(page
)) {
940 * Only in the case of a full synchronous migration is it
941 * necessary to wait for PageWriteback. In the async case,
942 * the retry loop is too short and in the sync-light case,
943 * the overhead of stalling is too much
945 if (mode
!= MIGRATE_SYNC
) {
951 wait_on_page_writeback(page
);
955 * By try_to_unmap(), page->mapcount goes down to 0 here. In this case,
956 * we cannot notice that anon_vma is freed while we migrates a page.
957 * This get_anon_vma() delays freeing anon_vma pointer until the end
958 * of migration. File cache pages are no problem because of page_lock()
959 * File Caches may use write_page() or lock_page() in migration, then,
960 * just care Anon page here.
962 * Only page_get_anon_vma() understands the subtleties of
963 * getting a hold on an anon_vma from outside one of its mms.
964 * But if we cannot get anon_vma, then we won't need it anyway,
965 * because that implies that the anon page is no longer mapped
966 * (and cannot be remapped so long as we hold the page lock).
968 if (PageAnon(page
) && !PageKsm(page
))
969 anon_vma
= page_get_anon_vma(page
);
972 * Block others from accessing the new page when we get around to
973 * establishing additional references. We are usually the only one
974 * holding a reference to newpage at this point. We used to have a BUG
975 * here if trylock_page(newpage) fails, but would like to allow for
976 * cases where there might be a race with the previous use of newpage.
977 * This is much like races on refcount of oldpage: just don't BUG().
979 if (unlikely(!trylock_page(newpage
)))
982 if (unlikely(!is_lru
)) {
983 rc
= move_to_new_page(newpage
, page
, mode
);
984 goto out_unlock_both
;
988 * Corner case handling:
989 * 1. When a new swap-cache page is read into, it is added to the LRU
990 * and treated as swapcache but it has no rmap yet.
991 * Calling try_to_unmap() against a page->mapping==NULL page will
992 * trigger a BUG. So handle it here.
993 * 2. An orphaned page (see truncate_complete_page) might have
994 * fs-private metadata. The page can be picked up due to memory
995 * offlining. Everywhere else except page reclaim, the page is
996 * invisible to the vm, so the page can not be migrated. So try to
997 * free the metadata, so the page can be freed.
999 if (!page
->mapping
) {
1000 VM_BUG_ON_PAGE(PageAnon(page
), page
);
1001 if (page_has_private(page
)) {
1002 try_to_free_buffers(page
);
1003 goto out_unlock_both
;
1005 } else if (page_mapped(page
)) {
1006 /* Establish migration ptes */
1007 VM_BUG_ON_PAGE(PageAnon(page
) && !PageKsm(page
) && !anon_vma
,
1010 TTU_MIGRATION
|TTU_IGNORE_MLOCK
|TTU_IGNORE_ACCESS
);
1011 page_was_mapped
= 1;
1014 if (!page_mapped(page
))
1015 rc
= move_to_new_page(newpage
, page
, mode
);
1017 if (page_was_mapped
)
1018 remove_migration_ptes(page
,
1019 rc
== MIGRATEPAGE_SUCCESS
? newpage
: page
, false);
1022 unlock_page(newpage
);
1024 /* Drop an anon_vma reference if we took one */
1026 put_anon_vma(anon_vma
);
1030 * If migration is successful, decrease refcount of the newpage
1031 * which will not free the page because new page owner increased
1032 * refcounter. As well, if it is LRU page, add the page to LRU
1035 if (rc
== MIGRATEPAGE_SUCCESS
) {
1036 if (unlikely(__PageMovable(newpage
)))
1039 putback_lru_page(newpage
);
1046 * gcc 4.7 and 4.8 on arm get an ICEs when inlining unmap_and_move(). Work
1049 #if (GCC_VERSION >= 40700 && GCC_VERSION < 40900) && defined(CONFIG_ARM)
1050 #define ICE_noinline noinline
1052 #define ICE_noinline
1056 * Obtain the lock on page, remove all ptes and migrate the page
1057 * to the newly allocated page in newpage.
1059 static ICE_noinline
int unmap_and_move(new_page_t get_new_page
,
1060 free_page_t put_new_page
,
1061 unsigned long private, struct page
*page
,
1062 int force
, enum migrate_mode mode
,
1063 enum migrate_reason reason
)
1065 int rc
= MIGRATEPAGE_SUCCESS
;
1067 struct page
*newpage
;
1069 newpage
= get_new_page(page
, private, &result
);
1073 if (page_count(page
) == 1) {
1074 /* page was freed from under us. So we are done. */
1075 ClearPageActive(page
);
1076 ClearPageUnevictable(page
);
1077 if (unlikely(__PageMovable(page
))) {
1079 if (!PageMovable(page
))
1080 __ClearPageIsolated(page
);
1084 put_new_page(newpage
, private);
1090 if (unlikely(PageTransHuge(page
))) {
1092 rc
= split_huge_page(page
);
1098 rc
= __unmap_and_move(page
, newpage
, force
, mode
);
1099 if (rc
== MIGRATEPAGE_SUCCESS
)
1100 set_page_owner_migrate_reason(newpage
, reason
);
1103 if (rc
!= -EAGAIN
) {
1105 * A page that has been migrated has all references
1106 * removed and will be freed. A page that has not been
1107 * migrated will have kepts its references and be
1110 list_del(&page
->lru
);
1113 * Compaction can migrate also non-LRU pages which are
1114 * not accounted to NR_ISOLATED_*. They can be recognized
1117 if (likely(!__PageMovable(page
)))
1118 dec_node_page_state(page
, NR_ISOLATED_ANON
+
1119 page_is_file_cache(page
));
1123 * If migration is successful, releases reference grabbed during
1124 * isolation. Otherwise, restore the page to right list unless
1127 if (rc
== MIGRATEPAGE_SUCCESS
) {
1129 if (reason
== MR_MEMORY_FAILURE
) {
1131 * Set PG_HWPoison on just freed page
1132 * intentionally. Although it's rather weird,
1133 * it's how HWPoison flag works at the moment.
1135 if (!test_set_page_hwpoison(page
))
1136 num_poisoned_pages_inc();
1139 if (rc
!= -EAGAIN
) {
1140 if (likely(!__PageMovable(page
))) {
1141 putback_lru_page(page
);
1146 if (PageMovable(page
))
1147 putback_movable_page(page
);
1149 __ClearPageIsolated(page
);
1155 put_new_page(newpage
, private);
1164 *result
= page_to_nid(newpage
);
1170 * Counterpart of unmap_and_move_page() for hugepage migration.
1172 * This function doesn't wait the completion of hugepage I/O
1173 * because there is no race between I/O and migration for hugepage.
1174 * Note that currently hugepage I/O occurs only in direct I/O
1175 * where no lock is held and PG_writeback is irrelevant,
1176 * and writeback status of all subpages are counted in the reference
1177 * count of the head page (i.e. if all subpages of a 2MB hugepage are
1178 * under direct I/O, the reference of the head page is 512 and a bit more.)
1179 * This means that when we try to migrate hugepage whose subpages are
1180 * doing direct I/O, some references remain after try_to_unmap() and
1181 * hugepage migration fails without data corruption.
1183 * There is also no race when direct I/O is issued on the page under migration,
1184 * because then pte is replaced with migration swap entry and direct I/O code
1185 * will wait in the page fault for migration to complete.
1187 static int unmap_and_move_huge_page(new_page_t get_new_page
,
1188 free_page_t put_new_page
, unsigned long private,
1189 struct page
*hpage
, int force
,
1190 enum migrate_mode mode
, int reason
)
1194 int page_was_mapped
= 0;
1195 struct page
*new_hpage
;
1196 struct anon_vma
*anon_vma
= NULL
;
1199 * Movability of hugepages depends on architectures and hugepage size.
1200 * This check is necessary because some callers of hugepage migration
1201 * like soft offline and memory hotremove don't walk through page
1202 * tables or check whether the hugepage is pmd-based or not before
1203 * kicking migration.
1205 if (!hugepage_migration_supported(page_hstate(hpage
))) {
1206 putback_active_hugepage(hpage
);
1210 new_hpage
= get_new_page(hpage
, private, &result
);
1214 if (!trylock_page(hpage
)) {
1215 if (!force
|| mode
!= MIGRATE_SYNC
)
1220 if (PageAnon(hpage
))
1221 anon_vma
= page_get_anon_vma(hpage
);
1223 if (unlikely(!trylock_page(new_hpage
)))
1226 if (page_mapped(hpage
)) {
1228 TTU_MIGRATION
|TTU_IGNORE_MLOCK
|TTU_IGNORE_ACCESS
);
1229 page_was_mapped
= 1;
1232 if (!page_mapped(hpage
))
1233 rc
= move_to_new_page(new_hpage
, hpage
, mode
);
1235 if (page_was_mapped
)
1236 remove_migration_ptes(hpage
,
1237 rc
== MIGRATEPAGE_SUCCESS
? new_hpage
: hpage
, false);
1239 unlock_page(new_hpage
);
1243 put_anon_vma(anon_vma
);
1245 if (rc
== MIGRATEPAGE_SUCCESS
) {
1246 hugetlb_cgroup_migrate(hpage
, new_hpage
);
1247 put_new_page
= NULL
;
1248 set_page_owner_migrate_reason(new_hpage
, reason
);
1254 putback_active_hugepage(hpage
);
1255 if (reason
== MR_MEMORY_FAILURE
&& !test_set_page_hwpoison(hpage
))
1256 num_poisoned_pages_inc();
1259 * If migration was not successful and there's a freeing callback, use
1260 * it. Otherwise, put_page() will drop the reference grabbed during
1264 put_new_page(new_hpage
, private);
1266 putback_active_hugepage(new_hpage
);
1272 *result
= page_to_nid(new_hpage
);
1278 * migrate_pages - migrate the pages specified in a list, to the free pages
1279 * supplied as the target for the page migration
1281 * @from: The list of pages to be migrated.
1282 * @get_new_page: The function used to allocate free pages to be used
1283 * as the target of the page migration.
1284 * @put_new_page: The function used to free target pages if migration
1285 * fails, or NULL if no special handling is necessary.
1286 * @private: Private data to be passed on to get_new_page()
1287 * @mode: The migration mode that specifies the constraints for
1288 * page migration, if any.
1289 * @reason: The reason for page migration.
1291 * The function returns after 10 attempts or if no pages are movable any more
1292 * because the list has become empty or no retryable pages exist any more.
1293 * The caller should call putback_movable_pages() to return pages to the LRU
1294 * or free list only if ret != 0.
1296 * Returns the number of pages that were not migrated, or an error code.
1298 int migrate_pages(struct list_head
*from
, new_page_t get_new_page
,
1299 free_page_t put_new_page
, unsigned long private,
1300 enum migrate_mode mode
, int reason
)
1304 int nr_succeeded
= 0;
1308 int swapwrite
= current
->flags
& PF_SWAPWRITE
;
1312 current
->flags
|= PF_SWAPWRITE
;
1314 for(pass
= 0; pass
< 10 && retry
; pass
++) {
1317 list_for_each_entry_safe(page
, page2
, from
, lru
) {
1321 rc
= unmap_and_move_huge_page(get_new_page
,
1322 put_new_page
, private, page
,
1323 pass
> 2, mode
, reason
);
1325 rc
= unmap_and_move(get_new_page
, put_new_page
,
1326 private, page
, pass
> 2, mode
,
1336 case MIGRATEPAGE_SUCCESS
:
1341 * Permanent failure (-EBUSY, -ENOSYS, etc.):
1342 * unlike -EAGAIN case, the failed page is
1343 * removed from migration page list and not
1344 * retried in the next outer loop.
1355 count_vm_events(PGMIGRATE_SUCCESS
, nr_succeeded
);
1357 count_vm_events(PGMIGRATE_FAIL
, nr_failed
);
1358 trace_mm_migrate_pages(nr_succeeded
, nr_failed
, mode
, reason
);
1361 current
->flags
&= ~PF_SWAPWRITE
;
1368 * Move a list of individual pages
1370 struct page_to_node
{
1377 static struct page
*new_page_node(struct page
*p
, unsigned long private,
1380 struct page_to_node
*pm
= (struct page_to_node
*)private;
1382 while (pm
->node
!= MAX_NUMNODES
&& pm
->page
!= p
)
1385 if (pm
->node
== MAX_NUMNODES
)
1388 *result
= &pm
->status
;
1391 return alloc_huge_page_node(page_hstate(compound_head(p
)),
1394 return __alloc_pages_node(pm
->node
,
1395 GFP_HIGHUSER_MOVABLE
| __GFP_THISNODE
, 0);
1399 * Move a set of pages as indicated in the pm array. The addr
1400 * field must be set to the virtual address of the page to be moved
1401 * and the node number must contain a valid target node.
1402 * The pm array ends with node = MAX_NUMNODES.
1404 static int do_move_page_to_node_array(struct mm_struct
*mm
,
1405 struct page_to_node
*pm
,
1409 struct page_to_node
*pp
;
1410 LIST_HEAD(pagelist
);
1412 down_read(&mm
->mmap_sem
);
1415 * Build a list of pages to migrate
1417 for (pp
= pm
; pp
->node
!= MAX_NUMNODES
; pp
++) {
1418 struct vm_area_struct
*vma
;
1422 vma
= find_vma(mm
, pp
->addr
);
1423 if (!vma
|| pp
->addr
< vma
->vm_start
|| !vma_migratable(vma
))
1426 /* FOLL_DUMP to ignore special (like zero) pages */
1427 page
= follow_page(vma
, pp
->addr
,
1428 FOLL_GET
| FOLL_SPLIT
| FOLL_DUMP
);
1430 err
= PTR_ERR(page
);
1439 err
= page_to_nid(page
);
1441 if (err
== pp
->node
)
1443 * Node already in the right place
1448 if (page_mapcount(page
) > 1 &&
1452 if (PageHuge(page
)) {
1454 isolate_huge_page(page
, &pagelist
);
1458 err
= isolate_lru_page(page
);
1460 list_add_tail(&page
->lru
, &pagelist
);
1461 inc_node_page_state(page
, NR_ISOLATED_ANON
+
1462 page_is_file_cache(page
));
1466 * Either remove the duplicate refcount from
1467 * isolate_lru_page() or drop the page ref if it was
1476 if (!list_empty(&pagelist
)) {
1477 err
= migrate_pages(&pagelist
, new_page_node
, NULL
,
1478 (unsigned long)pm
, MIGRATE_SYNC
, MR_SYSCALL
);
1480 putback_movable_pages(&pagelist
);
1483 up_read(&mm
->mmap_sem
);
1488 * Migrate an array of page address onto an array of nodes and fill
1489 * the corresponding array of status.
1491 static int do_pages_move(struct mm_struct
*mm
, nodemask_t task_nodes
,
1492 unsigned long nr_pages
,
1493 const void __user
* __user
*pages
,
1494 const int __user
*nodes
,
1495 int __user
*status
, int flags
)
1497 struct page_to_node
*pm
;
1498 unsigned long chunk_nr_pages
;
1499 unsigned long chunk_start
;
1503 pm
= (struct page_to_node
*)__get_free_page(GFP_KERNEL
);
1510 * Store a chunk of page_to_node array in a page,
1511 * but keep the last one as a marker
1513 chunk_nr_pages
= (PAGE_SIZE
/ sizeof(struct page_to_node
)) - 1;
1515 for (chunk_start
= 0;
1516 chunk_start
< nr_pages
;
1517 chunk_start
+= chunk_nr_pages
) {
1520 if (chunk_start
+ chunk_nr_pages
> nr_pages
)
1521 chunk_nr_pages
= nr_pages
- chunk_start
;
1523 /* fill the chunk pm with addrs and nodes from user-space */
1524 for (j
= 0; j
< chunk_nr_pages
; j
++) {
1525 const void __user
*p
;
1529 if (get_user(p
, pages
+ j
+ chunk_start
))
1531 pm
[j
].addr
= (unsigned long) p
;
1533 if (get_user(node
, nodes
+ j
+ chunk_start
))
1537 if (node
< 0 || node
>= MAX_NUMNODES
)
1540 if (!node_state(node
, N_MEMORY
))
1544 if (!node_isset(node
, task_nodes
))
1550 /* End marker for this chunk */
1551 pm
[chunk_nr_pages
].node
= MAX_NUMNODES
;
1553 /* Migrate this chunk */
1554 err
= do_move_page_to_node_array(mm
, pm
,
1555 flags
& MPOL_MF_MOVE_ALL
);
1559 /* Return status information */
1560 for (j
= 0; j
< chunk_nr_pages
; j
++)
1561 if (put_user(pm
[j
].status
, status
+ j
+ chunk_start
)) {
1569 free_page((unsigned long)pm
);
1575 * Determine the nodes of an array of pages and store it in an array of status.
1577 static void do_pages_stat_array(struct mm_struct
*mm
, unsigned long nr_pages
,
1578 const void __user
**pages
, int *status
)
1582 down_read(&mm
->mmap_sem
);
1584 for (i
= 0; i
< nr_pages
; i
++) {
1585 unsigned long addr
= (unsigned long)(*pages
);
1586 struct vm_area_struct
*vma
;
1590 vma
= find_vma(mm
, addr
);
1591 if (!vma
|| addr
< vma
->vm_start
)
1594 /* FOLL_DUMP to ignore special (like zero) pages */
1595 page
= follow_page(vma
, addr
, FOLL_DUMP
);
1597 err
= PTR_ERR(page
);
1601 err
= page
? page_to_nid(page
) : -ENOENT
;
1609 up_read(&mm
->mmap_sem
);
1613 * Determine the nodes of a user array of pages and store it in
1614 * a user array of status.
1616 static int do_pages_stat(struct mm_struct
*mm
, unsigned long nr_pages
,
1617 const void __user
* __user
*pages
,
1620 #define DO_PAGES_STAT_CHUNK_NR 16
1621 const void __user
*chunk_pages
[DO_PAGES_STAT_CHUNK_NR
];
1622 int chunk_status
[DO_PAGES_STAT_CHUNK_NR
];
1625 unsigned long chunk_nr
;
1627 chunk_nr
= nr_pages
;
1628 if (chunk_nr
> DO_PAGES_STAT_CHUNK_NR
)
1629 chunk_nr
= DO_PAGES_STAT_CHUNK_NR
;
1631 if (copy_from_user(chunk_pages
, pages
, chunk_nr
* sizeof(*chunk_pages
)))
1634 do_pages_stat_array(mm
, chunk_nr
, chunk_pages
, chunk_status
);
1636 if (copy_to_user(status
, chunk_status
, chunk_nr
* sizeof(*status
)))
1641 nr_pages
-= chunk_nr
;
1643 return nr_pages
? -EFAULT
: 0;
1647 * Move a list of pages in the address space of the currently executing
1650 SYSCALL_DEFINE6(move_pages
, pid_t
, pid
, unsigned long, nr_pages
,
1651 const void __user
* __user
*, pages
,
1652 const int __user
*, nodes
,
1653 int __user
*, status
, int, flags
)
1655 const struct cred
*cred
= current_cred(), *tcred
;
1656 struct task_struct
*task
;
1657 struct mm_struct
*mm
;
1659 nodemask_t task_nodes
;
1662 if (flags
& ~(MPOL_MF_MOVE
|MPOL_MF_MOVE_ALL
))
1665 if ((flags
& MPOL_MF_MOVE_ALL
) && !capable(CAP_SYS_NICE
))
1668 /* Find the mm_struct */
1670 task
= pid
? find_task_by_vpid(pid
) : current
;
1675 get_task_struct(task
);
1678 * Check if this process has the right to modify the specified
1679 * process. The right exists if the process has administrative
1680 * capabilities, superuser privileges or the same
1681 * userid as the target process.
1683 tcred
= __task_cred(task
);
1684 if (!uid_eq(cred
->euid
, tcred
->suid
) && !uid_eq(cred
->euid
, tcred
->uid
) &&
1685 !uid_eq(cred
->uid
, tcred
->suid
) && !uid_eq(cred
->uid
, tcred
->uid
) &&
1686 !capable(CAP_SYS_NICE
)) {
1693 err
= security_task_movememory(task
);
1697 task_nodes
= cpuset_mems_allowed(task
);
1698 mm
= get_task_mm(task
);
1699 put_task_struct(task
);
1705 err
= do_pages_move(mm
, task_nodes
, nr_pages
, pages
,
1706 nodes
, status
, flags
);
1708 err
= do_pages_stat(mm
, nr_pages
, pages
, status
);
1714 put_task_struct(task
);
1718 #ifdef CONFIG_NUMA_BALANCING
1720 * Returns true if this is a safe migration target node for misplaced NUMA
1721 * pages. Currently it only checks the watermarks which crude
1723 static bool migrate_balanced_pgdat(struct pglist_data
*pgdat
,
1724 unsigned long nr_migrate_pages
)
1728 for (z
= pgdat
->nr_zones
- 1; z
>= 0; z
--) {
1729 struct zone
*zone
= pgdat
->node_zones
+ z
;
1731 if (!populated_zone(zone
))
1734 /* Avoid waking kswapd by allocating pages_to_migrate pages. */
1735 if (!zone_watermark_ok(zone
, 0,
1736 high_wmark_pages(zone
) +
1745 static struct page
*alloc_misplaced_dst_page(struct page
*page
,
1749 int nid
= (int) data
;
1750 struct page
*newpage
;
1752 newpage
= __alloc_pages_node(nid
,
1753 (GFP_HIGHUSER_MOVABLE
|
1754 __GFP_THISNODE
| __GFP_NOMEMALLOC
|
1755 __GFP_NORETRY
| __GFP_NOWARN
) &
1762 * page migration rate limiting control.
1763 * Do not migrate more than @pages_to_migrate in a @migrate_interval_millisecs
1764 * window of time. Default here says do not migrate more than 1280M per second.
1766 static unsigned int migrate_interval_millisecs __read_mostly
= 100;
1767 static unsigned int ratelimit_pages __read_mostly
= 128 << (20 - PAGE_SHIFT
);
1769 /* Returns true if the node is migrate rate-limited after the update */
1770 static bool numamigrate_update_ratelimit(pg_data_t
*pgdat
,
1771 unsigned long nr_pages
)
1774 * Rate-limit the amount of data that is being migrated to a node.
1775 * Optimal placement is no good if the memory bus is saturated and
1776 * all the time is being spent migrating!
1778 if (time_after(jiffies
, pgdat
->numabalancing_migrate_next_window
)) {
1779 spin_lock(&pgdat
->numabalancing_migrate_lock
);
1780 pgdat
->numabalancing_migrate_nr_pages
= 0;
1781 pgdat
->numabalancing_migrate_next_window
= jiffies
+
1782 msecs_to_jiffies(migrate_interval_millisecs
);
1783 spin_unlock(&pgdat
->numabalancing_migrate_lock
);
1785 if (pgdat
->numabalancing_migrate_nr_pages
> ratelimit_pages
) {
1786 trace_mm_numa_migrate_ratelimit(current
, pgdat
->node_id
,
1792 * This is an unlocked non-atomic update so errors are possible.
1793 * The consequences are failing to migrate when we potentiall should
1794 * have which is not severe enough to warrant locking. If it is ever
1795 * a problem, it can be converted to a per-cpu counter.
1797 pgdat
->numabalancing_migrate_nr_pages
+= nr_pages
;
1801 static int numamigrate_isolate_page(pg_data_t
*pgdat
, struct page
*page
)
1805 VM_BUG_ON_PAGE(compound_order(page
) && !PageTransHuge(page
), page
);
1807 /* Avoid migrating to a node that is nearly full */
1808 if (!migrate_balanced_pgdat(pgdat
, 1UL << compound_order(page
)))
1811 if (isolate_lru_page(page
))
1815 * migrate_misplaced_transhuge_page() skips page migration's usual
1816 * check on page_count(), so we must do it here, now that the page
1817 * has been isolated: a GUP pin, or any other pin, prevents migration.
1818 * The expected page count is 3: 1 for page's mapcount and 1 for the
1819 * caller's pin and 1 for the reference taken by isolate_lru_page().
1821 if (PageTransHuge(page
) && page_count(page
) != 3) {
1822 putback_lru_page(page
);
1826 page_lru
= page_is_file_cache(page
);
1827 mod_node_page_state(page_pgdat(page
), NR_ISOLATED_ANON
+ page_lru
,
1828 hpage_nr_pages(page
));
1831 * Isolating the page has taken another reference, so the
1832 * caller's reference can be safely dropped without the page
1833 * disappearing underneath us during migration.
1839 bool pmd_trans_migrating(pmd_t pmd
)
1841 struct page
*page
= pmd_page(pmd
);
1842 return PageLocked(page
);
1846 * Attempt to migrate a misplaced page to the specified destination
1847 * node. Caller is expected to have an elevated reference count on
1848 * the page that will be dropped by this function before returning.
1850 int migrate_misplaced_page(struct page
*page
, struct vm_area_struct
*vma
,
1853 pg_data_t
*pgdat
= NODE_DATA(node
);
1856 LIST_HEAD(migratepages
);
1859 * Don't migrate file pages that are mapped in multiple processes
1860 * with execute permissions as they are probably shared libraries.
1862 if (page_mapcount(page
) != 1 && page_is_file_cache(page
) &&
1863 (vma
->vm_flags
& VM_EXEC
))
1867 * Rate-limit the amount of data that is being migrated to a node.
1868 * Optimal placement is no good if the memory bus is saturated and
1869 * all the time is being spent migrating!
1871 if (numamigrate_update_ratelimit(pgdat
, 1))
1874 isolated
= numamigrate_isolate_page(pgdat
, page
);
1878 list_add(&page
->lru
, &migratepages
);
1879 nr_remaining
= migrate_pages(&migratepages
, alloc_misplaced_dst_page
,
1880 NULL
, node
, MIGRATE_ASYNC
,
1883 if (!list_empty(&migratepages
)) {
1884 list_del(&page
->lru
);
1885 dec_node_page_state(page
, NR_ISOLATED_ANON
+
1886 page_is_file_cache(page
));
1887 putback_lru_page(page
);
1891 count_vm_numa_event(NUMA_PAGE_MIGRATE
);
1892 BUG_ON(!list_empty(&migratepages
));
1899 #endif /* CONFIG_NUMA_BALANCING */
1901 #if defined(CONFIG_NUMA_BALANCING) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
1903 * Migrates a THP to a given target node. page must be locked and is unlocked
1906 int migrate_misplaced_transhuge_page(struct mm_struct
*mm
,
1907 struct vm_area_struct
*vma
,
1908 pmd_t
*pmd
, pmd_t entry
,
1909 unsigned long address
,
1910 struct page
*page
, int node
)
1913 pg_data_t
*pgdat
= NODE_DATA(node
);
1915 struct page
*new_page
= NULL
;
1916 int page_lru
= page_is_file_cache(page
);
1917 unsigned long mmun_start
= address
& HPAGE_PMD_MASK
;
1918 unsigned long mmun_end
= mmun_start
+ HPAGE_PMD_SIZE
;
1921 * Rate-limit the amount of data that is being migrated to a node.
1922 * Optimal placement is no good if the memory bus is saturated and
1923 * all the time is being spent migrating!
1925 if (numamigrate_update_ratelimit(pgdat
, HPAGE_PMD_NR
))
1928 new_page
= alloc_pages_node(node
,
1929 (GFP_TRANSHUGE_LIGHT
| __GFP_THISNODE
),
1933 prep_transhuge_page(new_page
);
1935 isolated
= numamigrate_isolate_page(pgdat
, page
);
1941 * We are not sure a pending tlb flush here is for a huge page
1942 * mapping or not. Hence use the tlb range variant
1944 if (mm_tlb_flush_pending(mm
))
1945 flush_tlb_range(vma
, mmun_start
, mmun_end
);
1947 /* Prepare a page as a migration target */
1948 __SetPageLocked(new_page
);
1949 if (PageSwapBacked(page
))
1950 __SetPageSwapBacked(new_page
);
1952 /* anon mapping, we can simply copy page->mapping to the new page: */
1953 new_page
->mapping
= page
->mapping
;
1954 new_page
->index
= page
->index
;
1955 migrate_page_copy(new_page
, page
);
1956 WARN_ON(PageLRU(new_page
));
1958 /* Recheck the target PMD */
1959 mmu_notifier_invalidate_range_start(mm
, mmun_start
, mmun_end
);
1960 ptl
= pmd_lock(mm
, pmd
);
1961 if (unlikely(!pmd_same(*pmd
, entry
) || !page_ref_freeze(page
, 2))) {
1963 mmu_notifier_invalidate_range_end(mm
, mmun_start
, mmun_end
);
1965 /* Reverse changes made by migrate_page_copy() */
1966 if (TestClearPageActive(new_page
))
1967 SetPageActive(page
);
1968 if (TestClearPageUnevictable(new_page
))
1969 SetPageUnevictable(page
);
1971 unlock_page(new_page
);
1972 put_page(new_page
); /* Free it */
1974 /* Retake the callers reference and putback on LRU */
1976 putback_lru_page(page
);
1977 mod_node_page_state(page_pgdat(page
),
1978 NR_ISOLATED_ANON
+ page_lru
, -HPAGE_PMD_NR
);
1983 entry
= mk_huge_pmd(new_page
, vma
->vm_page_prot
);
1984 entry
= maybe_pmd_mkwrite(pmd_mkdirty(entry
), vma
);
1987 * Clear the old entry under pagetable lock and establish the new PTE.
1988 * Any parallel GUP will either observe the old page blocking on the
1989 * page lock, block on the page table lock or observe the new page.
1990 * The SetPageUptodate on the new page and page_add_new_anon_rmap
1991 * guarantee the copy is visible before the pagetable update.
1993 flush_cache_range(vma
, mmun_start
, mmun_end
);
1994 page_add_anon_rmap(new_page
, vma
, mmun_start
, true);
1995 pmdp_huge_clear_flush_notify(vma
, mmun_start
, pmd
);
1996 set_pmd_at(mm
, mmun_start
, pmd
, entry
);
1997 update_mmu_cache_pmd(vma
, address
, &entry
);
1999 page_ref_unfreeze(page
, 2);
2000 mlock_migrate_page(new_page
, page
);
2001 page_remove_rmap(page
, true);
2002 set_page_owner_migrate_reason(new_page
, MR_NUMA_MISPLACED
);
2005 mmu_notifier_invalidate_range_end(mm
, mmun_start
, mmun_end
);
2007 /* Take an "isolate" reference and put new page on the LRU. */
2009 putback_lru_page(new_page
);
2011 unlock_page(new_page
);
2013 put_page(page
); /* Drop the rmap reference */
2014 put_page(page
); /* Drop the LRU isolation reference */
2016 count_vm_events(PGMIGRATE_SUCCESS
, HPAGE_PMD_NR
);
2017 count_vm_numa_events(NUMA_PAGE_MIGRATE
, HPAGE_PMD_NR
);
2019 mod_node_page_state(page_pgdat(page
),
2020 NR_ISOLATED_ANON
+ page_lru
,
2025 count_vm_events(PGMIGRATE_FAIL
, HPAGE_PMD_NR
);
2027 ptl
= pmd_lock(mm
, pmd
);
2028 if (pmd_same(*pmd
, entry
)) {
2029 entry
= pmd_modify(entry
, vma
->vm_page_prot
);
2030 set_pmd_at(mm
, mmun_start
, pmd
, entry
);
2031 update_mmu_cache_pmd(vma
, address
, &entry
);
2040 #endif /* CONFIG_NUMA_BALANCING */
2042 #endif /* CONFIG_NUMA */