1 // SPDX-License-Identifier: GPL-2.0
3 * Memory Migration functionality - linux/mm/migrate.c
5 * Copyright (C) 2006 Silicon Graphics, Inc., Christoph Lameter
7 * Page migration was first developed in the context of the memory hotplug
8 * project. The main authors of the migration code are:
10 * IWAMOTO Toshihiro <iwamoto@valinux.co.jp>
11 * Hirokazu Takahashi <taka@valinux.co.jp>
12 * Dave Hansen <haveblue@us.ibm.com>
16 #include <linux/migrate.h>
17 #include <linux/export.h>
18 #include <linux/swap.h>
19 #include <linux/swapops.h>
20 #include <linux/pagemap.h>
21 #include <linux/buffer_head.h>
22 #include <linux/mm_inline.h>
23 #include <linux/nsproxy.h>
24 #include <linux/pagevec.h>
25 #include <linux/ksm.h>
26 #include <linux/rmap.h>
27 #include <linux/topology.h>
28 #include <linux/cpu.h>
29 #include <linux/cpuset.h>
30 #include <linux/writeback.h>
31 #include <linux/mempolicy.h>
32 #include <linux/vmalloc.h>
33 #include <linux/security.h>
34 #include <linux/backing-dev.h>
35 #include <linux/compaction.h>
36 #include <linux/syscalls.h>
37 #include <linux/compat.h>
38 #include <linux/hugetlb.h>
39 #include <linux/hugetlb_cgroup.h>
40 #include <linux/gfp.h>
41 #include <linux/pagewalk.h>
42 #include <linux/pfn_t.h>
43 #include <linux/memremap.h>
44 #include <linux/userfaultfd_k.h>
45 #include <linux/balloon_compaction.h>
46 #include <linux/mmu_notifier.h>
47 #include <linux/page_idle.h>
48 #include <linux/page_owner.h>
49 #include <linux/sched/mm.h>
50 #include <linux/ptrace.h>
51 #include <linux/oom.h>
53 #include <asm/tlbflush.h>
55 #define CREATE_TRACE_POINTS
56 #include <trace/events/migrate.h>
61 * migrate_prep() needs to be called before we start compiling a list of pages
62 * to be migrated using isolate_lru_page(). If scheduling work on other CPUs is
63 * undesirable, use migrate_prep_local()
65 int migrate_prep(void)
68 * Clear the LRU lists so pages can be isolated.
69 * Note that pages may be moved off the LRU after we have
70 * drained them. Those pages will fail to migrate like other
71 * pages that may be busy.
78 /* Do the necessary work of migrate_prep but not if it involves other CPUs */
79 int migrate_prep_local(void)
86 int isolate_movable_page(struct page
*page
, isolate_mode_t mode
)
88 struct address_space
*mapping
;
91 * Avoid burning cycles with pages that are yet under __free_pages(),
92 * or just got freed under us.
94 * In case we 'win' a race for a movable page being freed under us and
95 * raise its refcount preventing __free_pages() from doing its job
96 * the put_page() at the end of this block will take care of
97 * release this page, thus avoiding a nasty leakage.
99 if (unlikely(!get_page_unless_zero(page
)))
103 * Check PageMovable before holding a PG_lock because page's owner
104 * assumes anybody doesn't touch PG_lock of newly allocated page
105 * so unconditionally grabbing the lock ruins page's owner side.
107 if (unlikely(!__PageMovable(page
)))
110 * As movable pages are not isolated from LRU lists, concurrent
111 * compaction threads can race against page migration functions
112 * as well as race against the releasing a page.
114 * In order to avoid having an already isolated movable page
115 * being (wrongly) re-isolated while it is under migration,
116 * or to avoid attempting to isolate pages being released,
117 * lets be sure we have the page lock
118 * before proceeding with the movable page isolation steps.
120 if (unlikely(!trylock_page(page
)))
123 if (!PageMovable(page
) || PageIsolated(page
))
124 goto out_no_isolated
;
126 mapping
= page_mapping(page
);
127 VM_BUG_ON_PAGE(!mapping
, page
);
129 if (!mapping
->a_ops
->isolate_page(page
, mode
))
130 goto out_no_isolated
;
132 /* Driver shouldn't use PG_isolated bit of page->flags */
133 WARN_ON_ONCE(PageIsolated(page
));
134 __SetPageIsolated(page
);
147 /* It should be called on page which is PG_movable */
148 void putback_movable_page(struct page
*page
)
150 struct address_space
*mapping
;
152 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
153 VM_BUG_ON_PAGE(!PageMovable(page
), page
);
154 VM_BUG_ON_PAGE(!PageIsolated(page
), page
);
156 mapping
= page_mapping(page
);
157 mapping
->a_ops
->putback_page(page
);
158 __ClearPageIsolated(page
);
162 * Put previously isolated pages back onto the appropriate lists
163 * from where they were once taken off for compaction/migration.
165 * This function shall be used whenever the isolated pageset has been
166 * built from lru, balloon, hugetlbfs page. See isolate_migratepages_range()
167 * and isolate_huge_page().
169 void putback_movable_pages(struct list_head
*l
)
174 list_for_each_entry_safe(page
, page2
, l
, lru
) {
175 if (unlikely(PageHuge(page
))) {
176 putback_active_hugepage(page
);
179 list_del(&page
->lru
);
181 * We isolated non-lru movable page so here we can use
182 * __PageMovable because LRU page's mapping cannot have
183 * PAGE_MAPPING_MOVABLE.
185 if (unlikely(__PageMovable(page
))) {
186 VM_BUG_ON_PAGE(!PageIsolated(page
), page
);
188 if (PageMovable(page
))
189 putback_movable_page(page
);
191 __ClearPageIsolated(page
);
195 mod_node_page_state(page_pgdat(page
), NR_ISOLATED_ANON
+
196 page_is_file_lru(page
), -thp_nr_pages(page
));
197 putback_lru_page(page
);
203 * Restore a potential migration pte to a working pte entry
205 static bool remove_migration_pte(struct page
*page
, struct vm_area_struct
*vma
,
206 unsigned long addr
, void *old
)
208 struct page_vma_mapped_walk pvmw
= {
212 .flags
= PVMW_SYNC
| PVMW_MIGRATION
,
218 VM_BUG_ON_PAGE(PageTail(page
), page
);
219 while (page_vma_mapped_walk(&pvmw
)) {
223 new = page
- pvmw
.page
->index
+
224 linear_page_index(vma
, pvmw
.address
);
226 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
227 /* PMD-mapped THP migration entry */
229 VM_BUG_ON_PAGE(PageHuge(page
) || !PageTransCompound(page
), page
);
230 remove_migration_pmd(&pvmw
, new);
236 pte
= pte_mkold(mk_pte(new, READ_ONCE(vma
->vm_page_prot
)));
237 if (pte_swp_soft_dirty(*pvmw
.pte
))
238 pte
= pte_mksoft_dirty(pte
);
241 * Recheck VMA as permissions can change since migration started
243 entry
= pte_to_swp_entry(*pvmw
.pte
);
244 if (is_write_migration_entry(entry
))
245 pte
= maybe_mkwrite(pte
, vma
);
246 else if (pte_swp_uffd_wp(*pvmw
.pte
))
247 pte
= pte_mkuffd_wp(pte
);
249 if (unlikely(is_device_private_page(new))) {
250 entry
= make_device_private_entry(new, pte_write(pte
));
251 pte
= swp_entry_to_pte(entry
);
252 if (pte_swp_soft_dirty(*pvmw
.pte
))
253 pte
= pte_swp_mksoft_dirty(pte
);
254 if (pte_swp_uffd_wp(*pvmw
.pte
))
255 pte
= pte_swp_mkuffd_wp(pte
);
258 #ifdef CONFIG_HUGETLB_PAGE
260 pte
= pte_mkhuge(pte
);
261 pte
= arch_make_huge_pte(pte
, vma
, new, 0);
262 set_huge_pte_at(vma
->vm_mm
, pvmw
.address
, pvmw
.pte
, pte
);
264 hugepage_add_anon_rmap(new, vma
, pvmw
.address
);
266 page_dup_rmap(new, true);
270 set_pte_at(vma
->vm_mm
, pvmw
.address
, pvmw
.pte
, pte
);
273 page_add_anon_rmap(new, vma
, pvmw
.address
, false);
275 page_add_file_rmap(new, false);
277 if (vma
->vm_flags
& VM_LOCKED
&& !PageTransCompound(new))
280 if (PageTransHuge(page
) && PageMlocked(page
))
281 clear_page_mlock(page
);
283 /* No need to invalidate - it was non-present before */
284 update_mmu_cache(vma
, pvmw
.address
, pvmw
.pte
);
291 * Get rid of all migration entries and replace them by
292 * references to the indicated page.
294 void remove_migration_ptes(struct page
*old
, struct page
*new, bool locked
)
296 struct rmap_walk_control rwc
= {
297 .rmap_one
= remove_migration_pte
,
302 rmap_walk_locked(new, &rwc
);
304 rmap_walk(new, &rwc
);
308 * Something used the pte of a page under migration. We need to
309 * get to the page and wait until migration is finished.
310 * When we return from this function the fault will be retried.
312 void __migration_entry_wait(struct mm_struct
*mm
, pte_t
*ptep
,
321 if (!is_swap_pte(pte
))
324 entry
= pte_to_swp_entry(pte
);
325 if (!is_migration_entry(entry
))
328 page
= migration_entry_to_page(entry
);
331 * Once page cache replacement of page migration started, page_count
332 * is zero; but we must not call put_and_wait_on_page_locked() without
333 * a ref. Use get_page_unless_zero(), and just fault again if it fails.
335 if (!get_page_unless_zero(page
))
337 pte_unmap_unlock(ptep
, ptl
);
338 put_and_wait_on_page_locked(page
);
341 pte_unmap_unlock(ptep
, ptl
);
344 void migration_entry_wait(struct mm_struct
*mm
, pmd_t
*pmd
,
345 unsigned long address
)
347 spinlock_t
*ptl
= pte_lockptr(mm
, pmd
);
348 pte_t
*ptep
= pte_offset_map(pmd
, address
);
349 __migration_entry_wait(mm
, ptep
, ptl
);
352 void migration_entry_wait_huge(struct vm_area_struct
*vma
,
353 struct mm_struct
*mm
, pte_t
*pte
)
355 spinlock_t
*ptl
= huge_pte_lockptr(hstate_vma(vma
), mm
, pte
);
356 __migration_entry_wait(mm
, pte
, ptl
);
359 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
360 void pmd_migration_entry_wait(struct mm_struct
*mm
, pmd_t
*pmd
)
365 ptl
= pmd_lock(mm
, pmd
);
366 if (!is_pmd_migration_entry(*pmd
))
368 page
= migration_entry_to_page(pmd_to_swp_entry(*pmd
));
369 if (!get_page_unless_zero(page
))
372 put_and_wait_on_page_locked(page
);
379 static int expected_page_refs(struct address_space
*mapping
, struct page
*page
)
381 int expected_count
= 1;
384 * Device private pages have an extra refcount as they are
387 expected_count
+= is_device_private_page(page
);
389 expected_count
+= thp_nr_pages(page
) + page_has_private(page
);
391 return expected_count
;
395 * Replace the page in the mapping.
397 * The number of remaining references must be:
398 * 1 for anonymous pages without a mapping
399 * 2 for pages with a mapping
400 * 3 for pages with a mapping and PagePrivate/PagePrivate2 set.
402 int migrate_page_move_mapping(struct address_space
*mapping
,
403 struct page
*newpage
, struct page
*page
, int extra_count
)
405 XA_STATE(xas
, &mapping
->i_pages
, page_index(page
));
406 struct zone
*oldzone
, *newzone
;
408 int expected_count
= expected_page_refs(mapping
, page
) + extra_count
;
411 /* Anonymous page without mapping */
412 if (page_count(page
) != expected_count
)
415 /* No turning back from here */
416 newpage
->index
= page
->index
;
417 newpage
->mapping
= page
->mapping
;
418 if (PageSwapBacked(page
))
419 __SetPageSwapBacked(newpage
);
421 return MIGRATEPAGE_SUCCESS
;
424 oldzone
= page_zone(page
);
425 newzone
= page_zone(newpage
);
428 if (page_count(page
) != expected_count
|| xas_load(&xas
) != page
) {
429 xas_unlock_irq(&xas
);
433 if (!page_ref_freeze(page
, expected_count
)) {
434 xas_unlock_irq(&xas
);
439 * Now we know that no one else is looking at the page:
440 * no turning back from here.
442 newpage
->index
= page
->index
;
443 newpage
->mapping
= page
->mapping
;
444 page_ref_add(newpage
, thp_nr_pages(page
)); /* add cache reference */
445 if (PageSwapBacked(page
)) {
446 __SetPageSwapBacked(newpage
);
447 if (PageSwapCache(page
)) {
448 SetPageSwapCache(newpage
);
449 set_page_private(newpage
, page_private(page
));
452 VM_BUG_ON_PAGE(PageSwapCache(page
), page
);
455 /* Move dirty while page refs frozen and newpage not yet exposed */
456 dirty
= PageDirty(page
);
458 ClearPageDirty(page
);
459 SetPageDirty(newpage
);
462 xas_store(&xas
, newpage
);
463 if (PageTransHuge(page
)) {
466 for (i
= 1; i
< HPAGE_PMD_NR
; i
++) {
468 xas_store(&xas
, newpage
);
473 * Drop cache reference from old page by unfreezing
474 * to one less reference.
475 * We know this isn't the last reference.
477 page_ref_unfreeze(page
, expected_count
- thp_nr_pages(page
));
480 /* Leave irq disabled to prevent preemption while updating stats */
483 * If moved to a different zone then also account
484 * the page for that zone. Other VM counters will be
485 * taken care of when we establish references to the
486 * new page and drop references to the old page.
488 * Note that anonymous pages are accounted for
489 * via NR_FILE_PAGES and NR_ANON_MAPPED if they
490 * are mapped to swap space.
492 if (newzone
!= oldzone
) {
493 struct lruvec
*old_lruvec
, *new_lruvec
;
494 struct mem_cgroup
*memcg
;
496 memcg
= page_memcg(page
);
497 old_lruvec
= mem_cgroup_lruvec(memcg
, oldzone
->zone_pgdat
);
498 new_lruvec
= mem_cgroup_lruvec(memcg
, newzone
->zone_pgdat
);
500 __dec_lruvec_state(old_lruvec
, NR_FILE_PAGES
);
501 __inc_lruvec_state(new_lruvec
, NR_FILE_PAGES
);
502 if (PageSwapBacked(page
) && !PageSwapCache(page
)) {
503 __dec_lruvec_state(old_lruvec
, NR_SHMEM
);
504 __inc_lruvec_state(new_lruvec
, NR_SHMEM
);
506 if (dirty
&& mapping_can_writeback(mapping
)) {
507 __dec_node_state(oldzone
->zone_pgdat
, NR_FILE_DIRTY
);
508 __dec_zone_state(oldzone
, NR_ZONE_WRITE_PENDING
);
509 __inc_node_state(newzone
->zone_pgdat
, NR_FILE_DIRTY
);
510 __inc_zone_state(newzone
, NR_ZONE_WRITE_PENDING
);
515 return MIGRATEPAGE_SUCCESS
;
517 EXPORT_SYMBOL(migrate_page_move_mapping
);
520 * The expected number of remaining references is the same as that
521 * of migrate_page_move_mapping().
523 int migrate_huge_page_move_mapping(struct address_space
*mapping
,
524 struct page
*newpage
, struct page
*page
)
526 XA_STATE(xas
, &mapping
->i_pages
, page_index(page
));
530 expected_count
= 2 + page_has_private(page
);
531 if (page_count(page
) != expected_count
|| xas_load(&xas
) != page
) {
532 xas_unlock_irq(&xas
);
536 if (!page_ref_freeze(page
, expected_count
)) {
537 xas_unlock_irq(&xas
);
541 newpage
->index
= page
->index
;
542 newpage
->mapping
= page
->mapping
;
546 xas_store(&xas
, newpage
);
548 page_ref_unfreeze(page
, expected_count
- 1);
550 xas_unlock_irq(&xas
);
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
= thp_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_states(struct page
*newpage
, struct page
*page
)
611 SetPageError(newpage
);
612 if (PageReferenced(page
))
613 SetPageReferenced(newpage
);
614 if (PageUptodate(page
))
615 SetPageUptodate(newpage
);
616 if (TestClearPageActive(page
)) {
617 VM_BUG_ON_PAGE(PageUnevictable(page
), page
);
618 SetPageActive(newpage
);
619 } else if (TestClearPageUnevictable(page
))
620 SetPageUnevictable(newpage
);
621 if (PageWorkingset(page
))
622 SetPageWorkingset(newpage
);
623 if (PageChecked(page
))
624 SetPageChecked(newpage
);
625 if (PageMappedToDisk(page
))
626 SetPageMappedToDisk(newpage
);
628 /* Move dirty on pages not done by migrate_page_move_mapping() */
630 SetPageDirty(newpage
);
632 if (page_is_young(page
))
633 set_page_young(newpage
);
634 if (page_is_idle(page
))
635 set_page_idle(newpage
);
638 * Copy NUMA information to the new page, to prevent over-eager
639 * future migrations of this same page.
641 cpupid
= page_cpupid_xchg_last(page
, -1);
642 page_cpupid_xchg_last(newpage
, cpupid
);
644 ksm_migrate_page(newpage
, page
);
646 * Please do not reorder this without considering how mm/ksm.c's
647 * get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache().
649 if (PageSwapCache(page
))
650 ClearPageSwapCache(page
);
651 ClearPagePrivate(page
);
652 set_page_private(page
, 0);
655 * If any waiters have accumulated on the new page then
658 if (PageWriteback(newpage
))
659 end_page_writeback(newpage
);
662 * PG_readahead shares the same bit with PG_reclaim. The above
663 * end_page_writeback() may clear PG_readahead mistakenly, so set the
666 if (PageReadahead(page
))
667 SetPageReadahead(newpage
);
669 copy_page_owner(page
, newpage
);
672 mem_cgroup_migrate(page
, newpage
);
674 EXPORT_SYMBOL(migrate_page_states
);
676 void migrate_page_copy(struct page
*newpage
, struct page
*page
)
678 if (PageHuge(page
) || PageTransHuge(page
))
679 copy_huge_page(newpage
, page
);
681 copy_highpage(newpage
, page
);
683 migrate_page_states(newpage
, page
);
685 EXPORT_SYMBOL(migrate_page_copy
);
687 /************************************************************
688 * Migration functions
689 ***********************************************************/
692 * Common logic to directly migrate a single LRU page suitable for
693 * pages that do not use PagePrivate/PagePrivate2.
695 * Pages are locked upon entry and exit.
697 int migrate_page(struct address_space
*mapping
,
698 struct page
*newpage
, struct page
*page
,
699 enum migrate_mode mode
)
703 BUG_ON(PageWriteback(page
)); /* Writeback must be complete */
705 rc
= migrate_page_move_mapping(mapping
, newpage
, page
, 0);
707 if (rc
!= MIGRATEPAGE_SUCCESS
)
710 if (mode
!= MIGRATE_SYNC_NO_COPY
)
711 migrate_page_copy(newpage
, page
);
713 migrate_page_states(newpage
, page
);
714 return MIGRATEPAGE_SUCCESS
;
716 EXPORT_SYMBOL(migrate_page
);
719 /* Returns true if all buffers are successfully locked */
720 static bool buffer_migrate_lock_buffers(struct buffer_head
*head
,
721 enum migrate_mode mode
)
723 struct buffer_head
*bh
= head
;
725 /* Simple case, sync compaction */
726 if (mode
!= MIGRATE_ASYNC
) {
729 bh
= bh
->b_this_page
;
731 } while (bh
!= head
);
736 /* async case, we cannot block on lock_buffer so use trylock_buffer */
738 if (!trylock_buffer(bh
)) {
740 * We failed to lock the buffer and cannot stall in
741 * async migration. Release the taken locks
743 struct buffer_head
*failed_bh
= bh
;
745 while (bh
!= failed_bh
) {
747 bh
= bh
->b_this_page
;
752 bh
= bh
->b_this_page
;
753 } while (bh
!= head
);
757 static int __buffer_migrate_page(struct address_space
*mapping
,
758 struct page
*newpage
, struct page
*page
, enum migrate_mode mode
,
761 struct buffer_head
*bh
, *head
;
765 if (!page_has_buffers(page
))
766 return migrate_page(mapping
, newpage
, page
, mode
);
768 /* Check whether page does not have extra refs before we do more work */
769 expected_count
= expected_page_refs(mapping
, page
);
770 if (page_count(page
) != expected_count
)
773 head
= page_buffers(page
);
774 if (!buffer_migrate_lock_buffers(head
, mode
))
779 bool invalidated
= false;
783 spin_lock(&mapping
->private_lock
);
786 if (atomic_read(&bh
->b_count
)) {
790 bh
= bh
->b_this_page
;
791 } while (bh
!= head
);
797 spin_unlock(&mapping
->private_lock
);
798 invalidate_bh_lrus();
800 goto recheck_buffers
;
804 rc
= migrate_page_move_mapping(mapping
, newpage
, page
, 0);
805 if (rc
!= MIGRATEPAGE_SUCCESS
)
808 attach_page_private(newpage
, detach_page_private(page
));
812 set_bh_page(bh
, newpage
, bh_offset(bh
));
813 bh
= bh
->b_this_page
;
815 } while (bh
!= head
);
817 if (mode
!= MIGRATE_SYNC_NO_COPY
)
818 migrate_page_copy(newpage
, page
);
820 migrate_page_states(newpage
, page
);
822 rc
= MIGRATEPAGE_SUCCESS
;
825 spin_unlock(&mapping
->private_lock
);
829 bh
= bh
->b_this_page
;
831 } while (bh
!= head
);
837 * Migration function for pages with buffers. This function can only be used
838 * if the underlying filesystem guarantees that no other references to "page"
839 * exist. For example attached buffer heads are accessed only under page lock.
841 int buffer_migrate_page(struct address_space
*mapping
,
842 struct page
*newpage
, struct page
*page
, enum migrate_mode mode
)
844 return __buffer_migrate_page(mapping
, newpage
, page
, mode
, false);
846 EXPORT_SYMBOL(buffer_migrate_page
);
849 * Same as above except that this variant is more careful and checks that there
850 * are also no buffer head references. This function is the right one for
851 * mappings where buffer heads are directly looked up and referenced (such as
852 * block device mappings).
854 int buffer_migrate_page_norefs(struct address_space
*mapping
,
855 struct page
*newpage
, struct page
*page
, enum migrate_mode mode
)
857 return __buffer_migrate_page(mapping
, newpage
, page
, mode
, true);
862 * Writeback a page to clean the dirty state
864 static int writeout(struct address_space
*mapping
, struct page
*page
)
866 struct writeback_control wbc
= {
867 .sync_mode
= WB_SYNC_NONE
,
870 .range_end
= LLONG_MAX
,
875 if (!mapping
->a_ops
->writepage
)
876 /* No write method for the address space */
879 if (!clear_page_dirty_for_io(page
))
880 /* Someone else already triggered a write */
884 * A dirty page may imply that the underlying filesystem has
885 * the page on some queue. So the page must be clean for
886 * migration. Writeout may mean we loose the lock and the
887 * page state is no longer what we checked for earlier.
888 * At this point we know that the migration attempt cannot
891 remove_migration_ptes(page
, page
, false);
893 rc
= mapping
->a_ops
->writepage(page
, &wbc
);
895 if (rc
!= AOP_WRITEPAGE_ACTIVATE
)
896 /* unlocked. Relock */
899 return (rc
< 0) ? -EIO
: -EAGAIN
;
903 * Default handling if a filesystem does not provide a migration function.
905 static int fallback_migrate_page(struct address_space
*mapping
,
906 struct page
*newpage
, struct page
*page
, enum migrate_mode mode
)
908 if (PageDirty(page
)) {
909 /* Only writeback pages in full synchronous migration */
912 case MIGRATE_SYNC_NO_COPY
:
917 return writeout(mapping
, page
);
921 * Buffers may be managed in a filesystem specific way.
922 * We must have no buffers or drop them.
924 if (page_has_private(page
) &&
925 !try_to_release_page(page
, GFP_KERNEL
))
926 return mode
== MIGRATE_SYNC
? -EAGAIN
: -EBUSY
;
928 return migrate_page(mapping
, newpage
, page
, mode
);
932 * Move a page to a newly allocated page
933 * The page is locked and all ptes have been successfully removed.
935 * The new page will have replaced the old page if this function
940 * MIGRATEPAGE_SUCCESS - success
942 static int move_to_new_page(struct page
*newpage
, struct page
*page
,
943 enum migrate_mode mode
)
945 struct address_space
*mapping
;
947 bool is_lru
= !__PageMovable(page
);
949 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
950 VM_BUG_ON_PAGE(!PageLocked(newpage
), newpage
);
952 mapping
= page_mapping(page
);
954 if (likely(is_lru
)) {
956 rc
= migrate_page(mapping
, newpage
, page
, mode
);
957 else if (mapping
->a_ops
->migratepage
)
959 * Most pages have a mapping and most filesystems
960 * provide a migratepage callback. Anonymous pages
961 * are part of swap space which also has its own
962 * migratepage callback. This is the most common path
963 * for page migration.
965 rc
= mapping
->a_ops
->migratepage(mapping
, newpage
,
968 rc
= fallback_migrate_page(mapping
, newpage
,
972 * In case of non-lru page, it could be released after
973 * isolation step. In that case, we shouldn't try migration.
975 VM_BUG_ON_PAGE(!PageIsolated(page
), page
);
976 if (!PageMovable(page
)) {
977 rc
= MIGRATEPAGE_SUCCESS
;
978 __ClearPageIsolated(page
);
982 rc
= mapping
->a_ops
->migratepage(mapping
, newpage
,
984 WARN_ON_ONCE(rc
== MIGRATEPAGE_SUCCESS
&&
985 !PageIsolated(page
));
989 * When successful, old pagecache page->mapping must be cleared before
990 * page is freed; but stats require that PageAnon be left as PageAnon.
992 if (rc
== MIGRATEPAGE_SUCCESS
) {
993 if (__PageMovable(page
)) {
994 VM_BUG_ON_PAGE(!PageIsolated(page
), page
);
997 * We clear PG_movable under page_lock so any compactor
998 * cannot try to migrate this page.
1000 __ClearPageIsolated(page
);
1004 * Anonymous and movable page->mapping will be cleared by
1005 * free_pages_prepare so don't reset it here for keeping
1006 * the type to work PageAnon, for example.
1008 if (!PageMappingFlags(page
))
1009 page
->mapping
= NULL
;
1011 if (likely(!is_zone_device_page(newpage
)))
1012 flush_dcache_page(newpage
);
1019 static int __unmap_and_move(struct page
*page
, struct page
*newpage
,
1020 int force
, enum migrate_mode mode
)
1023 int page_was_mapped
= 0;
1024 struct anon_vma
*anon_vma
= NULL
;
1025 bool is_lru
= !__PageMovable(page
);
1027 if (!trylock_page(page
)) {
1028 if (!force
|| mode
== MIGRATE_ASYNC
)
1032 * It's not safe for direct compaction to call lock_page.
1033 * For example, during page readahead pages are added locked
1034 * to the LRU. Later, when the IO completes the pages are
1035 * marked uptodate and unlocked. However, the queueing
1036 * could be merging multiple pages for one bio (e.g.
1037 * mpage_readahead). If an allocation happens for the
1038 * second or third page, the process can end up locking
1039 * the same page twice and deadlocking. Rather than
1040 * trying to be clever about what pages can be locked,
1041 * avoid the use of lock_page for direct compaction
1044 if (current
->flags
& PF_MEMALLOC
)
1050 if (PageWriteback(page
)) {
1052 * Only in the case of a full synchronous migration is it
1053 * necessary to wait for PageWriteback. In the async case,
1054 * the retry loop is too short and in the sync-light case,
1055 * the overhead of stalling is too much
1059 case MIGRATE_SYNC_NO_COPY
:
1067 wait_on_page_writeback(page
);
1071 * By try_to_unmap(), page->mapcount goes down to 0 here. In this case,
1072 * we cannot notice that anon_vma is freed while we migrates a page.
1073 * This get_anon_vma() delays freeing anon_vma pointer until the end
1074 * of migration. File cache pages are no problem because of page_lock()
1075 * File Caches may use write_page() or lock_page() in migration, then,
1076 * just care Anon page here.
1078 * Only page_get_anon_vma() understands the subtleties of
1079 * getting a hold on an anon_vma from outside one of its mms.
1080 * But if we cannot get anon_vma, then we won't need it anyway,
1081 * because that implies that the anon page is no longer mapped
1082 * (and cannot be remapped so long as we hold the page lock).
1084 if (PageAnon(page
) && !PageKsm(page
))
1085 anon_vma
= page_get_anon_vma(page
);
1088 * Block others from accessing the new page when we get around to
1089 * establishing additional references. We are usually the only one
1090 * holding a reference to newpage at this point. We used to have a BUG
1091 * here if trylock_page(newpage) fails, but would like to allow for
1092 * cases where there might be a race with the previous use of newpage.
1093 * This is much like races on refcount of oldpage: just don't BUG().
1095 if (unlikely(!trylock_page(newpage
)))
1098 if (unlikely(!is_lru
)) {
1099 rc
= move_to_new_page(newpage
, page
, mode
);
1100 goto out_unlock_both
;
1104 * Corner case handling:
1105 * 1. When a new swap-cache page is read into, it is added to the LRU
1106 * and treated as swapcache but it has no rmap yet.
1107 * Calling try_to_unmap() against a page->mapping==NULL page will
1108 * trigger a BUG. So handle it here.
1109 * 2. An orphaned page (see truncate_cleanup_page) might have
1110 * fs-private metadata. The page can be picked up due to memory
1111 * offlining. Everywhere else except page reclaim, the page is
1112 * invisible to the vm, so the page can not be migrated. So try to
1113 * free the metadata, so the page can be freed.
1115 if (!page
->mapping
) {
1116 VM_BUG_ON_PAGE(PageAnon(page
), page
);
1117 if (page_has_private(page
)) {
1118 try_to_free_buffers(page
);
1119 goto out_unlock_both
;
1121 } else if (page_mapped(page
)) {
1122 /* Establish migration ptes */
1123 VM_BUG_ON_PAGE(PageAnon(page
) && !PageKsm(page
) && !anon_vma
,
1125 try_to_unmap(page
, TTU_MIGRATION
|TTU_IGNORE_MLOCK
);
1126 page_was_mapped
= 1;
1129 if (!page_mapped(page
))
1130 rc
= move_to_new_page(newpage
, page
, mode
);
1132 if (page_was_mapped
)
1133 remove_migration_ptes(page
,
1134 rc
== MIGRATEPAGE_SUCCESS
? newpage
: page
, false);
1137 unlock_page(newpage
);
1139 /* Drop an anon_vma reference if we took one */
1141 put_anon_vma(anon_vma
);
1145 * If migration is successful, decrease refcount of the newpage
1146 * which will not free the page because new page owner increased
1147 * refcounter. As well, if it is LRU page, add the page to LRU
1148 * list in here. Use the old state of the isolated source page to
1149 * determine if we migrated a LRU page. newpage was already unlocked
1150 * and possibly modified by its owner - don't rely on the page
1153 if (rc
== MIGRATEPAGE_SUCCESS
) {
1154 if (unlikely(!is_lru
))
1157 putback_lru_page(newpage
);
1164 * Obtain the lock on page, remove all ptes and migrate the page
1165 * to the newly allocated page in newpage.
1167 static int unmap_and_move(new_page_t get_new_page
,
1168 free_page_t put_new_page
,
1169 unsigned long private, struct page
*page
,
1170 int force
, enum migrate_mode mode
,
1171 enum migrate_reason reason
,
1172 struct list_head
*ret
)
1174 int rc
= MIGRATEPAGE_SUCCESS
;
1175 struct page
*newpage
= NULL
;
1177 if (!thp_migration_supported() && PageTransHuge(page
))
1180 if (page_count(page
) == 1) {
1181 /* page was freed from under us. So we are done. */
1182 ClearPageActive(page
);
1183 ClearPageUnevictable(page
);
1184 if (unlikely(__PageMovable(page
))) {
1186 if (!PageMovable(page
))
1187 __ClearPageIsolated(page
);
1193 newpage
= get_new_page(page
, private);
1197 rc
= __unmap_and_move(page
, newpage
, force
, mode
);
1198 if (rc
== MIGRATEPAGE_SUCCESS
)
1199 set_page_owner_migrate_reason(newpage
, reason
);
1202 if (rc
!= -EAGAIN
) {
1204 * A page that has been migrated has all references
1205 * removed and will be freed. A page that has not been
1206 * migrated will have kept its references and be restored.
1208 list_del(&page
->lru
);
1212 * If migration is successful, releases reference grabbed during
1213 * isolation. Otherwise, restore the page to right list unless
1216 if (rc
== MIGRATEPAGE_SUCCESS
) {
1218 * Compaction can migrate also non-LRU pages which are
1219 * not accounted to NR_ISOLATED_*. They can be recognized
1222 if (likely(!__PageMovable(page
)))
1223 mod_node_page_state(page_pgdat(page
), NR_ISOLATED_ANON
+
1224 page_is_file_lru(page
), -thp_nr_pages(page
));
1226 if (reason
!= MR_MEMORY_FAILURE
)
1228 * We release the page in page_handle_poison.
1233 list_add_tail(&page
->lru
, ret
);
1236 put_new_page(newpage
, private);
1245 * Counterpart of unmap_and_move_page() for hugepage migration.
1247 * This function doesn't wait the completion of hugepage I/O
1248 * because there is no race between I/O and migration for hugepage.
1249 * Note that currently hugepage I/O occurs only in direct I/O
1250 * where no lock is held and PG_writeback is irrelevant,
1251 * and writeback status of all subpages are counted in the reference
1252 * count of the head page (i.e. if all subpages of a 2MB hugepage are
1253 * under direct I/O, the reference of the head page is 512 and a bit more.)
1254 * This means that when we try to migrate hugepage whose subpages are
1255 * doing direct I/O, some references remain after try_to_unmap() and
1256 * hugepage migration fails without data corruption.
1258 * There is also no race when direct I/O is issued on the page under migration,
1259 * because then pte is replaced with migration swap entry and direct I/O code
1260 * will wait in the page fault for migration to complete.
1262 static int unmap_and_move_huge_page(new_page_t get_new_page
,
1263 free_page_t put_new_page
, unsigned long private,
1264 struct page
*hpage
, int force
,
1265 enum migrate_mode mode
, int reason
,
1266 struct list_head
*ret
)
1269 int page_was_mapped
= 0;
1270 struct page
*new_hpage
;
1271 struct anon_vma
*anon_vma
= NULL
;
1272 struct address_space
*mapping
= NULL
;
1275 * Migratability of hugepages depends on architectures and their size.
1276 * This check is necessary because some callers of hugepage migration
1277 * like soft offline and memory hotremove don't walk through page
1278 * tables or check whether the hugepage is pmd-based or not before
1279 * kicking migration.
1281 if (!hugepage_migration_supported(page_hstate(hpage
))) {
1282 list_move_tail(&hpage
->lru
, ret
);
1286 new_hpage
= get_new_page(hpage
, private);
1290 if (!trylock_page(hpage
)) {
1295 case MIGRATE_SYNC_NO_COPY
:
1304 * Check for pages which are in the process of being freed. Without
1305 * page_mapping() set, hugetlbfs specific move page routine will not
1306 * be called and we could leak usage counts for subpools.
1308 if (page_private(hpage
) && !page_mapping(hpage
)) {
1313 if (PageAnon(hpage
))
1314 anon_vma
= page_get_anon_vma(hpage
);
1316 if (unlikely(!trylock_page(new_hpage
)))
1319 if (page_mapped(hpage
)) {
1320 bool mapping_locked
= false;
1321 enum ttu_flags ttu
= TTU_MIGRATION
|TTU_IGNORE_MLOCK
;
1323 if (!PageAnon(hpage
)) {
1325 * In shared mappings, try_to_unmap could potentially
1326 * call huge_pmd_unshare. Because of this, take
1327 * semaphore in write mode here and set TTU_RMAP_LOCKED
1328 * to let lower levels know we have taken the lock.
1330 mapping
= hugetlb_page_mapping_lock_write(hpage
);
1331 if (unlikely(!mapping
))
1332 goto unlock_put_anon
;
1334 mapping_locked
= true;
1335 ttu
|= TTU_RMAP_LOCKED
;
1338 try_to_unmap(hpage
, ttu
);
1339 page_was_mapped
= 1;
1342 i_mmap_unlock_write(mapping
);
1345 if (!page_mapped(hpage
))
1346 rc
= move_to_new_page(new_hpage
, hpage
, mode
);
1348 if (page_was_mapped
)
1349 remove_migration_ptes(hpage
,
1350 rc
== MIGRATEPAGE_SUCCESS
? new_hpage
: hpage
, false);
1353 unlock_page(new_hpage
);
1357 put_anon_vma(anon_vma
);
1359 if (rc
== MIGRATEPAGE_SUCCESS
) {
1360 move_hugetlb_state(hpage
, new_hpage
, reason
);
1361 put_new_page
= NULL
;
1367 if (rc
== MIGRATEPAGE_SUCCESS
)
1368 putback_active_hugepage(hpage
);
1369 else if (rc
!= -EAGAIN
&& rc
!= MIGRATEPAGE_SUCCESS
)
1370 list_move_tail(&hpage
->lru
, ret
);
1373 * If migration was not successful and there's a freeing callback, use
1374 * it. Otherwise, put_page() will drop the reference grabbed during
1378 put_new_page(new_hpage
, private);
1380 putback_active_hugepage(new_hpage
);
1386 * migrate_pages - migrate the pages specified in a list, to the free pages
1387 * supplied as the target for the page migration
1389 * @from: The list of pages to be migrated.
1390 * @get_new_page: The function used to allocate free pages to be used
1391 * as the target of the page migration.
1392 * @put_new_page: The function used to free target pages if migration
1393 * fails, or NULL if no special handling is necessary.
1394 * @private: Private data to be passed on to get_new_page()
1395 * @mode: The migration mode that specifies the constraints for
1396 * page migration, if any.
1397 * @reason: The reason for page migration.
1399 * The function returns after 10 attempts or if no pages are movable any more
1400 * because the list has become empty or no retryable pages exist any more.
1401 * It is caller's responsibility to call putback_movable_pages() to return pages
1402 * to the LRU or free list only if ret != 0.
1404 * Returns the number of pages that were not migrated, or an error code.
1406 int migrate_pages(struct list_head
*from
, new_page_t get_new_page
,
1407 free_page_t put_new_page
, unsigned long private,
1408 enum migrate_mode mode
, int reason
)
1413 int nr_succeeded
= 0;
1414 int nr_thp_succeeded
= 0;
1415 int nr_thp_failed
= 0;
1416 int nr_thp_split
= 0;
1418 bool is_thp
= false;
1421 int swapwrite
= current
->flags
& PF_SWAPWRITE
;
1422 int rc
, nr_subpages
;
1423 LIST_HEAD(ret_pages
);
1426 current
->flags
|= PF_SWAPWRITE
;
1428 for (pass
= 0; pass
< 10 && (retry
|| thp_retry
); pass
++) {
1432 list_for_each_entry_safe(page
, page2
, from
, lru
) {
1435 * THP statistics is based on the source huge page.
1436 * Capture required information that might get lost
1439 is_thp
= PageTransHuge(page
) && !PageHuge(page
);
1440 nr_subpages
= thp_nr_pages(page
);
1444 rc
= unmap_and_move_huge_page(get_new_page
,
1445 put_new_page
, private, page
,
1446 pass
> 2, mode
, reason
,
1449 rc
= unmap_and_move(get_new_page
, put_new_page
,
1450 private, page
, pass
> 2, mode
,
1451 reason
, &ret_pages
);
1454 * Success: non hugetlb page will be freed, hugetlb
1455 * page will be put back
1456 * -EAGAIN: stay on the from list
1457 * -ENOMEM: stay on the from list
1458 * Other errno: put on ret_pages list then splice to
1464 * THP migration might be unsupported or the
1465 * allocation could've failed so we should
1466 * retry on the same page with the THP split
1469 * Head page is retried immediately and tail
1470 * pages are added to the tail of the list so
1471 * we encounter them after the rest of the list
1476 rc
= split_huge_page_to_list(page
, from
);
1479 list_safe_reset_next(page
, page2
, lru
);
1485 nr_failed
+= nr_subpages
;
1497 case MIGRATEPAGE_SUCCESS
:
1500 nr_succeeded
+= nr_subpages
;
1507 * Permanent failure (-EBUSY, -ENOSYS, etc.):
1508 * unlike -EAGAIN case, the failed page is
1509 * removed from migration page list and not
1510 * retried in the next outer loop.
1514 nr_failed
+= nr_subpages
;
1522 nr_failed
+= retry
+ thp_retry
;
1523 nr_thp_failed
+= thp_retry
;
1527 * Put the permanent failure page back to migration list, they
1528 * will be put back to the right list by the caller.
1530 list_splice(&ret_pages
, from
);
1532 count_vm_events(PGMIGRATE_SUCCESS
, nr_succeeded
);
1533 count_vm_events(PGMIGRATE_FAIL
, nr_failed
);
1534 count_vm_events(THP_MIGRATION_SUCCESS
, nr_thp_succeeded
);
1535 count_vm_events(THP_MIGRATION_FAIL
, nr_thp_failed
);
1536 count_vm_events(THP_MIGRATION_SPLIT
, nr_thp_split
);
1537 trace_mm_migrate_pages(nr_succeeded
, nr_failed
, nr_thp_succeeded
,
1538 nr_thp_failed
, nr_thp_split
, mode
, reason
);
1541 current
->flags
&= ~PF_SWAPWRITE
;
1546 struct page
*alloc_migration_target(struct page
*page
, unsigned long private)
1548 struct migration_target_control
*mtc
;
1550 unsigned int order
= 0;
1551 struct page
*new_page
= NULL
;
1555 mtc
= (struct migration_target_control
*)private;
1556 gfp_mask
= mtc
->gfp_mask
;
1558 if (nid
== NUMA_NO_NODE
)
1559 nid
= page_to_nid(page
);
1561 if (PageHuge(page
)) {
1562 struct hstate
*h
= page_hstate(compound_head(page
));
1564 gfp_mask
= htlb_modify_alloc_mask(h
, gfp_mask
);
1565 return alloc_huge_page_nodemask(h
, nid
, mtc
->nmask
, gfp_mask
);
1568 if (PageTransHuge(page
)) {
1570 * clear __GFP_RECLAIM to make the migration callback
1571 * consistent with regular THP allocations.
1573 gfp_mask
&= ~__GFP_RECLAIM
;
1574 gfp_mask
|= GFP_TRANSHUGE
;
1575 order
= HPAGE_PMD_ORDER
;
1577 zidx
= zone_idx(page_zone(page
));
1578 if (is_highmem_idx(zidx
) || zidx
== ZONE_MOVABLE
)
1579 gfp_mask
|= __GFP_HIGHMEM
;
1581 new_page
= __alloc_pages_nodemask(gfp_mask
, order
, nid
, mtc
->nmask
);
1583 if (new_page
&& PageTransHuge(new_page
))
1584 prep_transhuge_page(new_page
);
1591 static int store_status(int __user
*status
, int start
, int value
, int nr
)
1594 if (put_user(value
, status
+ start
))
1602 static int do_move_pages_to_node(struct mm_struct
*mm
,
1603 struct list_head
*pagelist
, int node
)
1606 struct migration_target_control mtc
= {
1608 .gfp_mask
= GFP_HIGHUSER_MOVABLE
| __GFP_THISNODE
,
1611 err
= migrate_pages(pagelist
, alloc_migration_target
, NULL
,
1612 (unsigned long)&mtc
, MIGRATE_SYNC
, MR_SYSCALL
);
1614 putback_movable_pages(pagelist
);
1619 * Resolves the given address to a struct page, isolates it from the LRU and
1620 * puts it to the given pagelist.
1622 * errno - if the page cannot be found/isolated
1623 * 0 - when it doesn't have to be migrated because it is already on the
1625 * 1 - when it has been queued
1627 static int add_page_for_migration(struct mm_struct
*mm
, unsigned long addr
,
1628 int node
, struct list_head
*pagelist
, bool migrate_all
)
1630 struct vm_area_struct
*vma
;
1632 unsigned int follflags
;
1637 vma
= find_vma(mm
, addr
);
1638 if (!vma
|| addr
< vma
->vm_start
|| !vma_migratable(vma
))
1641 /* FOLL_DUMP to ignore special (like zero) pages */
1642 follflags
= FOLL_GET
| FOLL_DUMP
;
1643 page
= follow_page(vma
, addr
, follflags
);
1645 err
= PTR_ERR(page
);
1654 if (page_to_nid(page
) == node
)
1658 if (page_mapcount(page
) > 1 && !migrate_all
)
1661 if (PageHuge(page
)) {
1662 if (PageHead(page
)) {
1663 isolate_huge_page(page
, pagelist
);
1669 head
= compound_head(page
);
1670 err
= isolate_lru_page(head
);
1675 list_add_tail(&head
->lru
, pagelist
);
1676 mod_node_page_state(page_pgdat(head
),
1677 NR_ISOLATED_ANON
+ page_is_file_lru(head
),
1678 thp_nr_pages(head
));
1682 * Either remove the duplicate refcount from
1683 * isolate_lru_page() or drop the page ref if it was
1688 mmap_read_unlock(mm
);
1692 static int move_pages_and_store_status(struct mm_struct
*mm
, int node
,
1693 struct list_head
*pagelist
, int __user
*status
,
1694 int start
, int i
, unsigned long nr_pages
)
1698 if (list_empty(pagelist
))
1701 err
= do_move_pages_to_node(mm
, pagelist
, node
);
1704 * Positive err means the number of failed
1705 * pages to migrate. Since we are going to
1706 * abort and return the number of non-migrated
1707 * pages, so need to include the rest of the
1708 * nr_pages that have not been attempted as
1712 err
+= nr_pages
- i
- 1;
1715 return store_status(status
, start
, node
, i
- start
);
1719 * Migrate an array of page address onto an array of nodes and fill
1720 * the corresponding array of status.
1722 static int do_pages_move(struct mm_struct
*mm
, nodemask_t task_nodes
,
1723 unsigned long nr_pages
,
1724 const void __user
* __user
*pages
,
1725 const int __user
*nodes
,
1726 int __user
*status
, int flags
)
1728 int current_node
= NUMA_NO_NODE
;
1729 LIST_HEAD(pagelist
);
1735 for (i
= start
= 0; i
< nr_pages
; i
++) {
1736 const void __user
*p
;
1741 if (get_user(p
, pages
+ i
))
1743 if (get_user(node
, nodes
+ i
))
1745 addr
= (unsigned long)untagged_addr(p
);
1748 if (node
< 0 || node
>= MAX_NUMNODES
)
1750 if (!node_state(node
, N_MEMORY
))
1754 if (!node_isset(node
, task_nodes
))
1757 if (current_node
== NUMA_NO_NODE
) {
1758 current_node
= node
;
1760 } else if (node
!= current_node
) {
1761 err
= move_pages_and_store_status(mm
, current_node
,
1762 &pagelist
, status
, start
, i
, nr_pages
);
1766 current_node
= node
;
1770 * Errors in the page lookup or isolation are not fatal and we simply
1771 * report them via status
1773 err
= add_page_for_migration(mm
, addr
, current_node
,
1774 &pagelist
, flags
& MPOL_MF_MOVE_ALL
);
1777 /* The page is successfully queued for migration */
1782 * If the page is already on the target node (!err), store the
1783 * node, otherwise, store the err.
1785 err
= store_status(status
, i
, err
? : current_node
, 1);
1789 err
= move_pages_and_store_status(mm
, current_node
, &pagelist
,
1790 status
, start
, i
, nr_pages
);
1793 current_node
= NUMA_NO_NODE
;
1796 /* Make sure we do not overwrite the existing error */
1797 err1
= move_pages_and_store_status(mm
, current_node
, &pagelist
,
1798 status
, start
, i
, nr_pages
);
1806 * Determine the nodes of an array of pages and store it in an array of status.
1808 static void do_pages_stat_array(struct mm_struct
*mm
, unsigned long nr_pages
,
1809 const void __user
**pages
, int *status
)
1815 for (i
= 0; i
< nr_pages
; i
++) {
1816 unsigned long addr
= (unsigned long)(*pages
);
1817 struct vm_area_struct
*vma
;
1821 vma
= find_vma(mm
, addr
);
1822 if (!vma
|| addr
< vma
->vm_start
)
1825 /* FOLL_DUMP to ignore special (like zero) pages */
1826 page
= follow_page(vma
, addr
, FOLL_DUMP
);
1828 err
= PTR_ERR(page
);
1832 err
= page
? page_to_nid(page
) : -ENOENT
;
1840 mmap_read_unlock(mm
);
1844 * Determine the nodes of a user array of pages and store it in
1845 * a user array of status.
1847 static int do_pages_stat(struct mm_struct
*mm
, unsigned long nr_pages
,
1848 const void __user
* __user
*pages
,
1851 #define DO_PAGES_STAT_CHUNK_NR 16
1852 const void __user
*chunk_pages
[DO_PAGES_STAT_CHUNK_NR
];
1853 int chunk_status
[DO_PAGES_STAT_CHUNK_NR
];
1856 unsigned long chunk_nr
;
1858 chunk_nr
= nr_pages
;
1859 if (chunk_nr
> DO_PAGES_STAT_CHUNK_NR
)
1860 chunk_nr
= DO_PAGES_STAT_CHUNK_NR
;
1862 if (copy_from_user(chunk_pages
, pages
, chunk_nr
* sizeof(*chunk_pages
)))
1865 do_pages_stat_array(mm
, chunk_nr
, chunk_pages
, chunk_status
);
1867 if (copy_to_user(status
, chunk_status
, chunk_nr
* sizeof(*status
)))
1872 nr_pages
-= chunk_nr
;
1874 return nr_pages
? -EFAULT
: 0;
1877 static struct mm_struct
*find_mm_struct(pid_t pid
, nodemask_t
*mem_nodes
)
1879 struct task_struct
*task
;
1880 struct mm_struct
*mm
;
1883 * There is no need to check if current process has the right to modify
1884 * the specified process when they are same.
1888 *mem_nodes
= cpuset_mems_allowed(current
);
1892 /* Find the mm_struct */
1894 task
= find_task_by_vpid(pid
);
1897 return ERR_PTR(-ESRCH
);
1899 get_task_struct(task
);
1902 * Check if this process has the right to modify the specified
1903 * process. Use the regular "ptrace_may_access()" checks.
1905 if (!ptrace_may_access(task
, PTRACE_MODE_READ_REALCREDS
)) {
1907 mm
= ERR_PTR(-EPERM
);
1912 mm
= ERR_PTR(security_task_movememory(task
));
1915 *mem_nodes
= cpuset_mems_allowed(task
);
1916 mm
= get_task_mm(task
);
1918 put_task_struct(task
);
1920 mm
= ERR_PTR(-EINVAL
);
1925 * Move a list of pages in the address space of the currently executing
1928 static int kernel_move_pages(pid_t pid
, unsigned long nr_pages
,
1929 const void __user
* __user
*pages
,
1930 const int __user
*nodes
,
1931 int __user
*status
, int flags
)
1933 struct mm_struct
*mm
;
1935 nodemask_t task_nodes
;
1938 if (flags
& ~(MPOL_MF_MOVE
|MPOL_MF_MOVE_ALL
))
1941 if ((flags
& MPOL_MF_MOVE_ALL
) && !capable(CAP_SYS_NICE
))
1944 mm
= find_mm_struct(pid
, &task_nodes
);
1949 err
= do_pages_move(mm
, task_nodes
, nr_pages
, pages
,
1950 nodes
, status
, flags
);
1952 err
= do_pages_stat(mm
, nr_pages
, pages
, status
);
1958 SYSCALL_DEFINE6(move_pages
, pid_t
, pid
, unsigned long, nr_pages
,
1959 const void __user
* __user
*, pages
,
1960 const int __user
*, nodes
,
1961 int __user
*, status
, int, flags
)
1963 return kernel_move_pages(pid
, nr_pages
, pages
, nodes
, status
, flags
);
1966 #ifdef CONFIG_COMPAT
1967 COMPAT_SYSCALL_DEFINE6(move_pages
, pid_t
, pid
, compat_ulong_t
, nr_pages
,
1968 compat_uptr_t __user
*, pages32
,
1969 const int __user
*, nodes
,
1970 int __user
*, status
,
1973 const void __user
* __user
*pages
;
1976 pages
= compat_alloc_user_space(nr_pages
* sizeof(void *));
1977 for (i
= 0; i
< nr_pages
; i
++) {
1980 if (get_user(p
, pages32
+ i
) ||
1981 put_user(compat_ptr(p
), pages
+ i
))
1984 return kernel_move_pages(pid
, nr_pages
, pages
, nodes
, status
, flags
);
1986 #endif /* CONFIG_COMPAT */
1988 #ifdef CONFIG_NUMA_BALANCING
1990 * Returns true if this is a safe migration target node for misplaced NUMA
1991 * pages. Currently it only checks the watermarks which crude
1993 static bool migrate_balanced_pgdat(struct pglist_data
*pgdat
,
1994 unsigned long nr_migrate_pages
)
1998 for (z
= pgdat
->nr_zones
- 1; z
>= 0; z
--) {
1999 struct zone
*zone
= pgdat
->node_zones
+ z
;
2001 if (!populated_zone(zone
))
2004 /* Avoid waking kswapd by allocating pages_to_migrate pages. */
2005 if (!zone_watermark_ok(zone
, 0,
2006 high_wmark_pages(zone
) +
2015 static struct page
*alloc_misplaced_dst_page(struct page
*page
,
2018 int nid
= (int) data
;
2019 struct page
*newpage
;
2021 newpage
= __alloc_pages_node(nid
,
2022 (GFP_HIGHUSER_MOVABLE
|
2023 __GFP_THISNODE
| __GFP_NOMEMALLOC
|
2024 __GFP_NORETRY
| __GFP_NOWARN
) &
2030 static int numamigrate_isolate_page(pg_data_t
*pgdat
, struct page
*page
)
2034 VM_BUG_ON_PAGE(compound_order(page
) && !PageTransHuge(page
), page
);
2036 /* Avoid migrating to a node that is nearly full */
2037 if (!migrate_balanced_pgdat(pgdat
, compound_nr(page
)))
2040 if (isolate_lru_page(page
))
2044 * migrate_misplaced_transhuge_page() skips page migration's usual
2045 * check on page_count(), so we must do it here, now that the page
2046 * has been isolated: a GUP pin, or any other pin, prevents migration.
2047 * The expected page count is 3: 1 for page's mapcount and 1 for the
2048 * caller's pin and 1 for the reference taken by isolate_lru_page().
2050 if (PageTransHuge(page
) && page_count(page
) != 3) {
2051 putback_lru_page(page
);
2055 page_lru
= page_is_file_lru(page
);
2056 mod_node_page_state(page_pgdat(page
), NR_ISOLATED_ANON
+ page_lru
,
2057 thp_nr_pages(page
));
2060 * Isolating the page has taken another reference, so the
2061 * caller's reference can be safely dropped without the page
2062 * disappearing underneath us during migration.
2068 bool pmd_trans_migrating(pmd_t pmd
)
2070 struct page
*page
= pmd_page(pmd
);
2071 return PageLocked(page
);
2074 static inline bool is_shared_exec_page(struct vm_area_struct
*vma
,
2077 if (page_mapcount(page
) != 1 &&
2078 (page_is_file_lru(page
) || vma_is_shmem(vma
)) &&
2079 (vma
->vm_flags
& VM_EXEC
))
2086 * Attempt to migrate a misplaced page to the specified destination
2087 * node. Caller is expected to have an elevated reference count on
2088 * the page that will be dropped by this function before returning.
2090 int migrate_misplaced_page(struct page
*page
, struct vm_area_struct
*vma
,
2093 pg_data_t
*pgdat
= NODE_DATA(node
);
2096 LIST_HEAD(migratepages
);
2099 * Don't migrate file pages that are mapped in multiple processes
2100 * with execute permissions as they are probably shared libraries.
2102 if (is_shared_exec_page(vma
, page
))
2106 * Also do not migrate dirty pages as not all filesystems can move
2107 * dirty pages in MIGRATE_ASYNC mode which is a waste of cycles.
2109 if (page_is_file_lru(page
) && PageDirty(page
))
2112 isolated
= numamigrate_isolate_page(pgdat
, page
);
2116 list_add(&page
->lru
, &migratepages
);
2117 nr_remaining
= migrate_pages(&migratepages
, alloc_misplaced_dst_page
,
2118 NULL
, node
, MIGRATE_ASYNC
,
2121 if (!list_empty(&migratepages
)) {
2122 list_del(&page
->lru
);
2123 dec_node_page_state(page
, NR_ISOLATED_ANON
+
2124 page_is_file_lru(page
));
2125 putback_lru_page(page
);
2129 count_vm_numa_event(NUMA_PAGE_MIGRATE
);
2130 BUG_ON(!list_empty(&migratepages
));
2137 #endif /* CONFIG_NUMA_BALANCING */
2139 #if defined(CONFIG_NUMA_BALANCING) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
2141 * Migrates a THP to a given target node. page must be locked and is unlocked
2144 int migrate_misplaced_transhuge_page(struct mm_struct
*mm
,
2145 struct vm_area_struct
*vma
,
2146 pmd_t
*pmd
, pmd_t entry
,
2147 unsigned long address
,
2148 struct page
*page
, int node
)
2151 pg_data_t
*pgdat
= NODE_DATA(node
);
2153 struct page
*new_page
= NULL
;
2154 int page_lru
= page_is_file_lru(page
);
2155 unsigned long start
= address
& HPAGE_PMD_MASK
;
2157 if (is_shared_exec_page(vma
, page
))
2160 new_page
= alloc_pages_node(node
,
2161 (GFP_TRANSHUGE_LIGHT
| __GFP_THISNODE
),
2165 prep_transhuge_page(new_page
);
2167 isolated
= numamigrate_isolate_page(pgdat
, page
);
2173 /* Prepare a page as a migration target */
2174 __SetPageLocked(new_page
);
2175 if (PageSwapBacked(page
))
2176 __SetPageSwapBacked(new_page
);
2178 /* anon mapping, we can simply copy page->mapping to the new page: */
2179 new_page
->mapping
= page
->mapping
;
2180 new_page
->index
= page
->index
;
2181 /* flush the cache before copying using the kernel virtual address */
2182 flush_cache_range(vma
, start
, start
+ HPAGE_PMD_SIZE
);
2183 migrate_page_copy(new_page
, page
);
2184 WARN_ON(PageLRU(new_page
));
2186 /* Recheck the target PMD */
2187 ptl
= pmd_lock(mm
, pmd
);
2188 if (unlikely(!pmd_same(*pmd
, entry
) || !page_ref_freeze(page
, 2))) {
2191 /* Reverse changes made by migrate_page_copy() */
2192 if (TestClearPageActive(new_page
))
2193 SetPageActive(page
);
2194 if (TestClearPageUnevictable(new_page
))
2195 SetPageUnevictable(page
);
2197 unlock_page(new_page
);
2198 put_page(new_page
); /* Free it */
2200 /* Retake the callers reference and putback on LRU */
2202 putback_lru_page(page
);
2203 mod_node_page_state(page_pgdat(page
),
2204 NR_ISOLATED_ANON
+ page_lru
, -HPAGE_PMD_NR
);
2209 entry
= mk_huge_pmd(new_page
, vma
->vm_page_prot
);
2210 entry
= maybe_pmd_mkwrite(pmd_mkdirty(entry
), vma
);
2213 * Overwrite the old entry under pagetable lock and establish
2214 * the new PTE. Any parallel GUP will either observe the old
2215 * page blocking on the page lock, block on the page table
2216 * lock or observe the new page. The SetPageUptodate on the
2217 * new page and page_add_new_anon_rmap guarantee the copy is
2218 * visible before the pagetable update.
2220 page_add_anon_rmap(new_page
, vma
, start
, true);
2222 * At this point the pmd is numa/protnone (i.e. non present) and the TLB
2223 * has already been flushed globally. So no TLB can be currently
2224 * caching this non present pmd mapping. There's no need to clear the
2225 * pmd before doing set_pmd_at(), nor to flush the TLB after
2226 * set_pmd_at(). Clearing the pmd here would introduce a race
2227 * condition against MADV_DONTNEED, because MADV_DONTNEED only holds the
2228 * mmap_lock for reading. If the pmd is set to NULL at any given time,
2229 * MADV_DONTNEED won't wait on the pmd lock and it'll skip clearing this
2232 set_pmd_at(mm
, start
, pmd
, entry
);
2233 update_mmu_cache_pmd(vma
, address
, &entry
);
2235 page_ref_unfreeze(page
, 2);
2236 mlock_migrate_page(new_page
, page
);
2237 page_remove_rmap(page
, true);
2238 set_page_owner_migrate_reason(new_page
, MR_NUMA_MISPLACED
);
2242 /* Take an "isolate" reference and put new page on the LRU. */
2244 putback_lru_page(new_page
);
2246 unlock_page(new_page
);
2248 put_page(page
); /* Drop the rmap reference */
2249 put_page(page
); /* Drop the LRU isolation reference */
2251 count_vm_events(PGMIGRATE_SUCCESS
, HPAGE_PMD_NR
);
2252 count_vm_numa_events(NUMA_PAGE_MIGRATE
, HPAGE_PMD_NR
);
2254 mod_node_page_state(page_pgdat(page
),
2255 NR_ISOLATED_ANON
+ page_lru
,
2260 count_vm_events(PGMIGRATE_FAIL
, HPAGE_PMD_NR
);
2261 ptl
= pmd_lock(mm
, pmd
);
2262 if (pmd_same(*pmd
, entry
)) {
2263 entry
= pmd_modify(entry
, vma
->vm_page_prot
);
2264 set_pmd_at(mm
, start
, pmd
, entry
);
2265 update_mmu_cache_pmd(vma
, address
, &entry
);
2275 #endif /* CONFIG_NUMA_BALANCING */
2277 #endif /* CONFIG_NUMA */
2279 #ifdef CONFIG_DEVICE_PRIVATE
2280 static int migrate_vma_collect_hole(unsigned long start
,
2282 __always_unused
int depth
,
2283 struct mm_walk
*walk
)
2285 struct migrate_vma
*migrate
= walk
->private;
2288 /* Only allow populating anonymous memory. */
2289 if (!vma_is_anonymous(walk
->vma
)) {
2290 for (addr
= start
; addr
< end
; addr
+= PAGE_SIZE
) {
2291 migrate
->src
[migrate
->npages
] = 0;
2292 migrate
->dst
[migrate
->npages
] = 0;
2298 for (addr
= start
; addr
< end
; addr
+= PAGE_SIZE
) {
2299 migrate
->src
[migrate
->npages
] = MIGRATE_PFN_MIGRATE
;
2300 migrate
->dst
[migrate
->npages
] = 0;
2308 static int migrate_vma_collect_skip(unsigned long start
,
2310 struct mm_walk
*walk
)
2312 struct migrate_vma
*migrate
= walk
->private;
2315 for (addr
= start
; addr
< end
; addr
+= PAGE_SIZE
) {
2316 migrate
->dst
[migrate
->npages
] = 0;
2317 migrate
->src
[migrate
->npages
++] = 0;
2323 static int migrate_vma_collect_pmd(pmd_t
*pmdp
,
2324 unsigned long start
,
2326 struct mm_walk
*walk
)
2328 struct migrate_vma
*migrate
= walk
->private;
2329 struct vm_area_struct
*vma
= walk
->vma
;
2330 struct mm_struct
*mm
= vma
->vm_mm
;
2331 unsigned long addr
= start
, unmapped
= 0;
2336 if (pmd_none(*pmdp
))
2337 return migrate_vma_collect_hole(start
, end
, -1, walk
);
2339 if (pmd_trans_huge(*pmdp
)) {
2342 ptl
= pmd_lock(mm
, pmdp
);
2343 if (unlikely(!pmd_trans_huge(*pmdp
))) {
2348 page
= pmd_page(*pmdp
);
2349 if (is_huge_zero_page(page
)) {
2351 split_huge_pmd(vma
, pmdp
, addr
);
2352 if (pmd_trans_unstable(pmdp
))
2353 return migrate_vma_collect_skip(start
, end
,
2360 if (unlikely(!trylock_page(page
)))
2361 return migrate_vma_collect_skip(start
, end
,
2363 ret
= split_huge_page(page
);
2367 return migrate_vma_collect_skip(start
, end
,
2369 if (pmd_none(*pmdp
))
2370 return migrate_vma_collect_hole(start
, end
, -1,
2375 if (unlikely(pmd_bad(*pmdp
)))
2376 return migrate_vma_collect_skip(start
, end
, walk
);
2378 ptep
= pte_offset_map_lock(mm
, pmdp
, addr
, &ptl
);
2379 arch_enter_lazy_mmu_mode();
2381 for (; addr
< end
; addr
+= PAGE_SIZE
, ptep
++) {
2382 unsigned long mpfn
= 0, pfn
;
2389 if (pte_none(pte
)) {
2390 if (vma_is_anonymous(vma
)) {
2391 mpfn
= MIGRATE_PFN_MIGRATE
;
2397 if (!pte_present(pte
)) {
2399 * Only care about unaddressable device page special
2400 * page table entry. Other special swap entries are not
2401 * migratable, and we ignore regular swapped page.
2403 entry
= pte_to_swp_entry(pte
);
2404 if (!is_device_private_entry(entry
))
2407 page
= device_private_entry_to_page(entry
);
2408 if (!(migrate
->flags
&
2409 MIGRATE_VMA_SELECT_DEVICE_PRIVATE
) ||
2410 page
->pgmap
->owner
!= migrate
->pgmap_owner
)
2413 mpfn
= migrate_pfn(page_to_pfn(page
)) |
2414 MIGRATE_PFN_MIGRATE
;
2415 if (is_write_device_private_entry(entry
))
2416 mpfn
|= MIGRATE_PFN_WRITE
;
2418 if (!(migrate
->flags
& MIGRATE_VMA_SELECT_SYSTEM
))
2421 if (is_zero_pfn(pfn
)) {
2422 mpfn
= MIGRATE_PFN_MIGRATE
;
2426 page
= vm_normal_page(migrate
->vma
, addr
, pte
);
2427 mpfn
= migrate_pfn(pfn
) | MIGRATE_PFN_MIGRATE
;
2428 mpfn
|= pte_write(pte
) ? MIGRATE_PFN_WRITE
: 0;
2431 /* FIXME support THP */
2432 if (!page
|| !page
->mapping
|| PageTransCompound(page
)) {
2438 * By getting a reference on the page we pin it and that blocks
2439 * any kind of migration. Side effect is that it "freezes" the
2442 * We drop this reference after isolating the page from the lru
2443 * for non device page (device page are not on the lru and thus
2444 * can't be dropped from it).
2450 * Optimize for the common case where page is only mapped once
2451 * in one process. If we can lock the page, then we can safely
2452 * set up a special migration page table entry now.
2454 if (trylock_page(page
)) {
2457 mpfn
|= MIGRATE_PFN_LOCKED
;
2458 ptep_get_and_clear(mm
, addr
, ptep
);
2460 /* Setup special migration page table entry */
2461 entry
= make_migration_entry(page
, mpfn
&
2463 swp_pte
= swp_entry_to_pte(entry
);
2464 if (pte_present(pte
)) {
2465 if (pte_soft_dirty(pte
))
2466 swp_pte
= pte_swp_mksoft_dirty(swp_pte
);
2467 if (pte_uffd_wp(pte
))
2468 swp_pte
= pte_swp_mkuffd_wp(swp_pte
);
2470 if (pte_swp_soft_dirty(pte
))
2471 swp_pte
= pte_swp_mksoft_dirty(swp_pte
);
2472 if (pte_swp_uffd_wp(pte
))
2473 swp_pte
= pte_swp_mkuffd_wp(swp_pte
);
2475 set_pte_at(mm
, addr
, ptep
, swp_pte
);
2478 * This is like regular unmap: we remove the rmap and
2479 * drop page refcount. Page won't be freed, as we took
2480 * a reference just above.
2482 page_remove_rmap(page
, false);
2485 if (pte_present(pte
))
2490 migrate
->dst
[migrate
->npages
] = 0;
2491 migrate
->src
[migrate
->npages
++] = mpfn
;
2493 arch_leave_lazy_mmu_mode();
2494 pte_unmap_unlock(ptep
- 1, ptl
);
2496 /* Only flush the TLB if we actually modified any entries */
2498 flush_tlb_range(walk
->vma
, start
, end
);
2503 static const struct mm_walk_ops migrate_vma_walk_ops
= {
2504 .pmd_entry
= migrate_vma_collect_pmd
,
2505 .pte_hole
= migrate_vma_collect_hole
,
2509 * migrate_vma_collect() - collect pages over a range of virtual addresses
2510 * @migrate: migrate struct containing all migration information
2512 * This will walk the CPU page table. For each virtual address backed by a
2513 * valid page, it updates the src array and takes a reference on the page, in
2514 * order to pin the page until we lock it and unmap it.
2516 static void migrate_vma_collect(struct migrate_vma
*migrate
)
2518 struct mmu_notifier_range range
;
2521 * Note that the pgmap_owner is passed to the mmu notifier callback so
2522 * that the registered device driver can skip invalidating device
2523 * private page mappings that won't be migrated.
2525 mmu_notifier_range_init_migrate(&range
, 0, migrate
->vma
,
2526 migrate
->vma
->vm_mm
, migrate
->start
, migrate
->end
,
2527 migrate
->pgmap_owner
);
2528 mmu_notifier_invalidate_range_start(&range
);
2530 walk_page_range(migrate
->vma
->vm_mm
, migrate
->start
, migrate
->end
,
2531 &migrate_vma_walk_ops
, migrate
);
2533 mmu_notifier_invalidate_range_end(&range
);
2534 migrate
->end
= migrate
->start
+ (migrate
->npages
<< PAGE_SHIFT
);
2538 * migrate_vma_check_page() - check if page is pinned or not
2539 * @page: struct page to check
2541 * Pinned pages cannot be migrated. This is the same test as in
2542 * migrate_page_move_mapping(), except that here we allow migration of a
2545 static bool migrate_vma_check_page(struct page
*page
)
2548 * One extra ref because caller holds an extra reference, either from
2549 * isolate_lru_page() for a regular page, or migrate_vma_collect() for
2555 * FIXME support THP (transparent huge page), it is bit more complex to
2556 * check them than regular pages, because they can be mapped with a pmd
2557 * or with a pte (split pte mapping).
2559 if (PageCompound(page
))
2562 /* Page from ZONE_DEVICE have one extra reference */
2563 if (is_zone_device_page(page
)) {
2565 * Private page can never be pin as they have no valid pte and
2566 * GUP will fail for those. Yet if there is a pending migration
2567 * a thread might try to wait on the pte migration entry and
2568 * will bump the page reference count. Sadly there is no way to
2569 * differentiate a regular pin from migration wait. Hence to
2570 * avoid 2 racing thread trying to migrate back to CPU to enter
2571 * infinite loop (one stoping migration because the other is
2572 * waiting on pte migration entry). We always return true here.
2574 * FIXME proper solution is to rework migration_entry_wait() so
2575 * it does not need to take a reference on page.
2577 return is_device_private_page(page
);
2580 /* For file back page */
2581 if (page_mapping(page
))
2582 extra
+= 1 + page_has_private(page
);
2584 if ((page_count(page
) - extra
) > page_mapcount(page
))
2591 * migrate_vma_prepare() - lock pages and isolate them from the lru
2592 * @migrate: migrate struct containing all migration information
2594 * This locks pages that have been collected by migrate_vma_collect(). Once each
2595 * page is locked it is isolated from the lru (for non-device pages). Finally,
2596 * the ref taken by migrate_vma_collect() is dropped, as locked pages cannot be
2597 * migrated by concurrent kernel threads.
2599 static void migrate_vma_prepare(struct migrate_vma
*migrate
)
2601 const unsigned long npages
= migrate
->npages
;
2602 const unsigned long start
= migrate
->start
;
2603 unsigned long addr
, i
, restore
= 0;
2604 bool allow_drain
= true;
2608 for (i
= 0; (i
< npages
) && migrate
->cpages
; i
++) {
2609 struct page
*page
= migrate_pfn_to_page(migrate
->src
[i
]);
2615 if (!(migrate
->src
[i
] & MIGRATE_PFN_LOCKED
)) {
2617 * Because we are migrating several pages there can be
2618 * a deadlock between 2 concurrent migration where each
2619 * are waiting on each other page lock.
2621 * Make migrate_vma() a best effort thing and backoff
2622 * for any page we can not lock right away.
2624 if (!trylock_page(page
)) {
2625 migrate
->src
[i
] = 0;
2631 migrate
->src
[i
] |= MIGRATE_PFN_LOCKED
;
2634 /* ZONE_DEVICE pages are not on LRU */
2635 if (!is_zone_device_page(page
)) {
2636 if (!PageLRU(page
) && allow_drain
) {
2637 /* Drain CPU's pagevec */
2638 lru_add_drain_all();
2639 allow_drain
= false;
2642 if (isolate_lru_page(page
)) {
2644 migrate
->src
[i
] &= ~MIGRATE_PFN_MIGRATE
;
2648 migrate
->src
[i
] = 0;
2656 /* Drop the reference we took in collect */
2660 if (!migrate_vma_check_page(page
)) {
2662 migrate
->src
[i
] &= ~MIGRATE_PFN_MIGRATE
;
2666 if (!is_zone_device_page(page
)) {
2668 putback_lru_page(page
);
2671 migrate
->src
[i
] = 0;
2675 if (!is_zone_device_page(page
))
2676 putback_lru_page(page
);
2683 for (i
= 0, addr
= start
; i
< npages
&& restore
; i
++, addr
+= PAGE_SIZE
) {
2684 struct page
*page
= migrate_pfn_to_page(migrate
->src
[i
]);
2686 if (!page
|| (migrate
->src
[i
] & MIGRATE_PFN_MIGRATE
))
2689 remove_migration_pte(page
, migrate
->vma
, addr
, page
);
2691 migrate
->src
[i
] = 0;
2699 * migrate_vma_unmap() - replace page mapping with special migration pte entry
2700 * @migrate: migrate struct containing all migration information
2702 * Replace page mapping (CPU page table pte) with a special migration pte entry
2703 * and check again if it has been pinned. Pinned pages are restored because we
2704 * cannot migrate them.
2706 * This is the last step before we call the device driver callback to allocate
2707 * destination memory and copy contents of original page over to new page.
2709 static void migrate_vma_unmap(struct migrate_vma
*migrate
)
2711 int flags
= TTU_MIGRATION
| TTU_IGNORE_MLOCK
;
2712 const unsigned long npages
= migrate
->npages
;
2713 const unsigned long start
= migrate
->start
;
2714 unsigned long addr
, i
, restore
= 0;
2716 for (i
= 0; i
< npages
; i
++) {
2717 struct page
*page
= migrate_pfn_to_page(migrate
->src
[i
]);
2719 if (!page
|| !(migrate
->src
[i
] & MIGRATE_PFN_MIGRATE
))
2722 if (page_mapped(page
)) {
2723 try_to_unmap(page
, flags
);
2724 if (page_mapped(page
))
2728 if (migrate_vma_check_page(page
))
2732 migrate
->src
[i
] &= ~MIGRATE_PFN_MIGRATE
;
2737 for (addr
= start
, i
= 0; i
< npages
&& restore
; addr
+= PAGE_SIZE
, i
++) {
2738 struct page
*page
= migrate_pfn_to_page(migrate
->src
[i
]);
2740 if (!page
|| (migrate
->src
[i
] & MIGRATE_PFN_MIGRATE
))
2743 remove_migration_ptes(page
, page
, false);
2745 migrate
->src
[i
] = 0;
2749 if (is_zone_device_page(page
))
2752 putback_lru_page(page
);
2757 * migrate_vma_setup() - prepare to migrate a range of memory
2758 * @args: contains the vma, start, and pfns arrays for the migration
2760 * Returns: negative errno on failures, 0 when 0 or more pages were migrated
2763 * Prepare to migrate a range of memory virtual address range by collecting all
2764 * the pages backing each virtual address in the range, saving them inside the
2765 * src array. Then lock those pages and unmap them. Once the pages are locked
2766 * and unmapped, check whether each page is pinned or not. Pages that aren't
2767 * pinned have the MIGRATE_PFN_MIGRATE flag set (by this function) in the
2768 * corresponding src array entry. Then restores any pages that are pinned, by
2769 * remapping and unlocking those pages.
2771 * The caller should then allocate destination memory and copy source memory to
2772 * it for all those entries (ie with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE
2773 * flag set). Once these are allocated and copied, the caller must update each
2774 * corresponding entry in the dst array with the pfn value of the destination
2775 * page and with the MIGRATE_PFN_VALID and MIGRATE_PFN_LOCKED flags set
2776 * (destination pages must have their struct pages locked, via lock_page()).
2778 * Note that the caller does not have to migrate all the pages that are marked
2779 * with MIGRATE_PFN_MIGRATE flag in src array unless this is a migration from
2780 * device memory to system memory. If the caller cannot migrate a device page
2781 * back to system memory, then it must return VM_FAULT_SIGBUS, which has severe
2782 * consequences for the userspace process, so it must be avoided if at all
2785 * For empty entries inside CPU page table (pte_none() or pmd_none() is true) we
2786 * do set MIGRATE_PFN_MIGRATE flag inside the corresponding source array thus
2787 * allowing the caller to allocate device memory for those unback virtual
2788 * address. For this the caller simply has to allocate device memory and
2789 * properly set the destination entry like for regular migration. Note that
2790 * this can still fails and thus inside the device driver must check if the
2791 * migration was successful for those entries after calling migrate_vma_pages()
2792 * just like for regular migration.
2794 * After that, the callers must call migrate_vma_pages() to go over each entry
2795 * in the src array that has the MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag
2796 * set. If the corresponding entry in dst array has MIGRATE_PFN_VALID flag set,
2797 * then migrate_vma_pages() to migrate struct page information from the source
2798 * struct page to the destination struct page. If it fails to migrate the
2799 * struct page information, then it clears the MIGRATE_PFN_MIGRATE flag in the
2802 * At this point all successfully migrated pages have an entry in the src
2803 * array with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag set and the dst
2804 * array entry with MIGRATE_PFN_VALID flag set.
2806 * Once migrate_vma_pages() returns the caller may inspect which pages were
2807 * successfully migrated, and which were not. Successfully migrated pages will
2808 * have the MIGRATE_PFN_MIGRATE flag set for their src array entry.
2810 * It is safe to update device page table after migrate_vma_pages() because
2811 * both destination and source page are still locked, and the mmap_lock is held
2812 * in read mode (hence no one can unmap the range being migrated).
2814 * Once the caller is done cleaning up things and updating its page table (if it
2815 * chose to do so, this is not an obligation) it finally calls
2816 * migrate_vma_finalize() to update the CPU page table to point to new pages
2817 * for successfully migrated pages or otherwise restore the CPU page table to
2818 * point to the original source pages.
2820 int migrate_vma_setup(struct migrate_vma
*args
)
2822 long nr_pages
= (args
->end
- args
->start
) >> PAGE_SHIFT
;
2824 args
->start
&= PAGE_MASK
;
2825 args
->end
&= PAGE_MASK
;
2826 if (!args
->vma
|| is_vm_hugetlb_page(args
->vma
) ||
2827 (args
->vma
->vm_flags
& VM_SPECIAL
) || vma_is_dax(args
->vma
))
2831 if (args
->start
< args
->vma
->vm_start
||
2832 args
->start
>= args
->vma
->vm_end
)
2834 if (args
->end
<= args
->vma
->vm_start
|| args
->end
> args
->vma
->vm_end
)
2836 if (!args
->src
|| !args
->dst
)
2839 memset(args
->src
, 0, sizeof(*args
->src
) * nr_pages
);
2843 migrate_vma_collect(args
);
2846 migrate_vma_prepare(args
);
2848 migrate_vma_unmap(args
);
2851 * At this point pages are locked and unmapped, and thus they have
2852 * stable content and can safely be copied to destination memory that
2853 * is allocated by the drivers.
2858 EXPORT_SYMBOL(migrate_vma_setup
);
2861 * This code closely matches the code in:
2862 * __handle_mm_fault()
2863 * handle_pte_fault()
2864 * do_anonymous_page()
2865 * to map in an anonymous zero page but the struct page will be a ZONE_DEVICE
2868 static void migrate_vma_insert_page(struct migrate_vma
*migrate
,
2874 struct vm_area_struct
*vma
= migrate
->vma
;
2875 struct mm_struct
*mm
= vma
->vm_mm
;
2885 /* Only allow populating anonymous memory */
2886 if (!vma_is_anonymous(vma
))
2889 pgdp
= pgd_offset(mm
, addr
);
2890 p4dp
= p4d_alloc(mm
, pgdp
, addr
);
2893 pudp
= pud_alloc(mm
, p4dp
, addr
);
2896 pmdp
= pmd_alloc(mm
, pudp
, addr
);
2900 if (pmd_trans_huge(*pmdp
) || pmd_devmap(*pmdp
))
2904 * Use pte_alloc() instead of pte_alloc_map(). We can't run
2905 * pte_offset_map() on pmds where a huge pmd might be created
2906 * from a different thread.
2908 * pte_alloc_map() is safe to use under mmap_write_lock(mm) or when
2909 * parallel threads are excluded by other means.
2911 * Here we only have mmap_read_lock(mm).
2913 if (pte_alloc(mm
, pmdp
))
2916 /* See the comment in pte_alloc_one_map() */
2917 if (unlikely(pmd_trans_unstable(pmdp
)))
2920 if (unlikely(anon_vma_prepare(vma
)))
2922 if (mem_cgroup_charge(page
, vma
->vm_mm
, GFP_KERNEL
))
2926 * The memory barrier inside __SetPageUptodate makes sure that
2927 * preceding stores to the page contents become visible before
2928 * the set_pte_at() write.
2930 __SetPageUptodate(page
);
2932 if (is_zone_device_page(page
)) {
2933 if (is_device_private_page(page
)) {
2934 swp_entry_t swp_entry
;
2936 swp_entry
= make_device_private_entry(page
, vma
->vm_flags
& VM_WRITE
);
2937 entry
= swp_entry_to_pte(swp_entry
);
2940 entry
= mk_pte(page
, vma
->vm_page_prot
);
2941 if (vma
->vm_flags
& VM_WRITE
)
2942 entry
= pte_mkwrite(pte_mkdirty(entry
));
2945 ptep
= pte_offset_map_lock(mm
, pmdp
, addr
, &ptl
);
2947 if (check_stable_address_space(mm
))
2950 if (pte_present(*ptep
)) {
2951 unsigned long pfn
= pte_pfn(*ptep
);
2953 if (!is_zero_pfn(pfn
))
2956 } else if (!pte_none(*ptep
))
2960 * Check for userfaultfd but do not deliver the fault. Instead,
2963 if (userfaultfd_missing(vma
))
2966 inc_mm_counter(mm
, MM_ANONPAGES
);
2967 page_add_new_anon_rmap(page
, vma
, addr
, false);
2968 if (!is_zone_device_page(page
))
2969 lru_cache_add_inactive_or_unevictable(page
, vma
);
2973 flush_cache_page(vma
, addr
, pte_pfn(*ptep
));
2974 ptep_clear_flush_notify(vma
, addr
, ptep
);
2975 set_pte_at_notify(mm
, addr
, ptep
, entry
);
2976 update_mmu_cache(vma
, addr
, ptep
);
2978 /* No need to invalidate - it was non-present before */
2979 set_pte_at(mm
, addr
, ptep
, entry
);
2980 update_mmu_cache(vma
, addr
, ptep
);
2983 pte_unmap_unlock(ptep
, ptl
);
2984 *src
= MIGRATE_PFN_MIGRATE
;
2988 pte_unmap_unlock(ptep
, ptl
);
2990 *src
&= ~MIGRATE_PFN_MIGRATE
;
2994 * migrate_vma_pages() - migrate meta-data from src page to dst page
2995 * @migrate: migrate struct containing all migration information
2997 * This migrates struct page meta-data from source struct page to destination
2998 * struct page. This effectively finishes the migration from source page to the
3001 void migrate_vma_pages(struct migrate_vma
*migrate
)
3003 const unsigned long npages
= migrate
->npages
;
3004 const unsigned long start
= migrate
->start
;
3005 struct mmu_notifier_range range
;
3006 unsigned long addr
, i
;
3007 bool notified
= false;
3009 for (i
= 0, addr
= start
; i
< npages
; addr
+= PAGE_SIZE
, i
++) {
3010 struct page
*newpage
= migrate_pfn_to_page(migrate
->dst
[i
]);
3011 struct page
*page
= migrate_pfn_to_page(migrate
->src
[i
]);
3012 struct address_space
*mapping
;
3016 migrate
->src
[i
] &= ~MIGRATE_PFN_MIGRATE
;
3021 if (!(migrate
->src
[i
] & MIGRATE_PFN_MIGRATE
))
3026 mmu_notifier_range_init_migrate(&range
, 0,
3027 migrate
->vma
, migrate
->vma
->vm_mm
,
3029 migrate
->pgmap_owner
);
3030 mmu_notifier_invalidate_range_start(&range
);
3032 migrate_vma_insert_page(migrate
, addr
, newpage
,
3038 mapping
= page_mapping(page
);
3040 if (is_zone_device_page(newpage
)) {
3041 if (is_device_private_page(newpage
)) {
3043 * For now only support private anonymous when
3044 * migrating to un-addressable device memory.
3047 migrate
->src
[i
] &= ~MIGRATE_PFN_MIGRATE
;
3052 * Other types of ZONE_DEVICE page are not
3055 migrate
->src
[i
] &= ~MIGRATE_PFN_MIGRATE
;
3060 r
= migrate_page(mapping
, newpage
, page
, MIGRATE_SYNC_NO_COPY
);
3061 if (r
!= MIGRATEPAGE_SUCCESS
)
3062 migrate
->src
[i
] &= ~MIGRATE_PFN_MIGRATE
;
3066 * No need to double call mmu_notifier->invalidate_range() callback as
3067 * the above ptep_clear_flush_notify() inside migrate_vma_insert_page()
3068 * did already call it.
3071 mmu_notifier_invalidate_range_only_end(&range
);
3073 EXPORT_SYMBOL(migrate_vma_pages
);
3076 * migrate_vma_finalize() - restore CPU page table entry
3077 * @migrate: migrate struct containing all migration information
3079 * This replaces the special migration pte entry with either a mapping to the
3080 * new page if migration was successful for that page, or to the original page
3083 * This also unlocks the pages and puts them back on the lru, or drops the extra
3084 * refcount, for device pages.
3086 void migrate_vma_finalize(struct migrate_vma
*migrate
)
3088 const unsigned long npages
= migrate
->npages
;
3091 for (i
= 0; i
< npages
; i
++) {
3092 struct page
*newpage
= migrate_pfn_to_page(migrate
->dst
[i
]);
3093 struct page
*page
= migrate_pfn_to_page(migrate
->src
[i
]);
3097 unlock_page(newpage
);
3103 if (!(migrate
->src
[i
] & MIGRATE_PFN_MIGRATE
) || !newpage
) {
3105 unlock_page(newpage
);
3111 remove_migration_ptes(page
, newpage
, false);
3114 if (is_zone_device_page(page
))
3117 putback_lru_page(page
);
3119 if (newpage
!= page
) {
3120 unlock_page(newpage
);
3121 if (is_zone_device_page(newpage
))
3124 putback_lru_page(newpage
);
3128 EXPORT_SYMBOL(migrate_vma_finalize
);
3129 #endif /* CONFIG_DEVICE_PRIVATE */