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>
52 #include <asm/tlbflush.h>
54 #define CREATE_TRACE_POINTS
55 #include <trace/events/migrate.h>
60 * migrate_prep() needs to be called before we start compiling a list of pages
61 * to be migrated using isolate_lru_page(). If scheduling work on other CPUs is
62 * undesirable, use migrate_prep_local()
64 int migrate_prep(void)
67 * Clear the LRU lists so pages can be isolated.
68 * Note that pages may be moved off the LRU after we have
69 * drained them. Those pages will fail to migrate like other
70 * pages that may be busy.
77 /* Do the necessary work of migrate_prep but not if it involves other CPUs */
78 int migrate_prep_local(void)
85 int isolate_movable_page(struct page *page, isolate_mode_t mode)
87 struct address_space *mapping;
90 * Avoid burning cycles with pages that are yet under __free_pages(),
91 * or just got freed under us.
93 * In case we 'win' a race for a movable page being freed under us and
94 * raise its refcount preventing __free_pages() from doing its job
95 * the put_page() at the end of this block will take care of
96 * release this page, thus avoiding a nasty leakage.
98 if (unlikely(!get_page_unless_zero(page)))
102 * Check PageMovable before holding a PG_lock because page's owner
103 * assumes anybody doesn't touch PG_lock of newly allocated page
104 * so unconditionally grabbing the lock ruins page's owner side.
106 if (unlikely(!__PageMovable(page)))
109 * As movable pages are not isolated from LRU lists, concurrent
110 * compaction threads can race against page migration functions
111 * as well as race against the releasing a page.
113 * In order to avoid having an already isolated movable page
114 * being (wrongly) re-isolated while it is under migration,
115 * or to avoid attempting to isolate pages being released,
116 * lets be sure we have the page lock
117 * before proceeding with the movable page isolation steps.
119 if (unlikely(!trylock_page(page)))
122 if (!PageMovable(page) || PageIsolated(page))
123 goto out_no_isolated;
125 mapping = page_mapping(page);
126 VM_BUG_ON_PAGE(!mapping, page);
128 if (!mapping->a_ops->isolate_page(page, mode))
129 goto out_no_isolated;
131 /* Driver shouldn't use PG_isolated bit of page->flags */
132 WARN_ON_ONCE(PageIsolated(page));
133 __SetPageIsolated(page);
146 /* It should be called on page which is PG_movable */
147 void putback_movable_page(struct page *page)
149 struct address_space *mapping;
151 VM_BUG_ON_PAGE(!PageLocked(page), page);
152 VM_BUG_ON_PAGE(!PageMovable(page), page);
153 VM_BUG_ON_PAGE(!PageIsolated(page), page);
155 mapping = page_mapping(page);
156 mapping->a_ops->putback_page(page);
157 __ClearPageIsolated(page);
161 * Put previously isolated pages back onto the appropriate lists
162 * from where they were once taken off for compaction/migration.
164 * This function shall be used whenever the isolated pageset has been
165 * built from lru, balloon, hugetlbfs page. See isolate_migratepages_range()
166 * and isolate_huge_page().
168 void putback_movable_pages(struct list_head *l)
173 list_for_each_entry_safe(page, page2, l, lru) {
174 if (unlikely(PageHuge(page))) {
175 putback_active_hugepage(page);
178 list_del(&page->lru);
180 * We isolated non-lru movable page so here we can use
181 * __PageMovable because LRU page's mapping cannot have
182 * PAGE_MAPPING_MOVABLE.
184 if (unlikely(__PageMovable(page))) {
185 VM_BUG_ON_PAGE(!PageIsolated(page), page);
187 if (PageMovable(page))
188 putback_movable_page(page);
190 __ClearPageIsolated(page);
194 mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON +
195 page_is_file_cache(page), -hpage_nr_pages(page));
196 putback_lru_page(page);
202 * Restore a potential migration pte to a working pte entry
204 static bool remove_migration_pte(struct page *page, struct vm_area_struct *vma,
205 unsigned long addr, void *old)
207 struct page_vma_mapped_walk pvmw = {
211 .flags = PVMW_SYNC | PVMW_MIGRATION,
217 VM_BUG_ON_PAGE(PageTail(page), page);
218 while (page_vma_mapped_walk(&pvmw)) {
222 new = page - pvmw.page->index +
223 linear_page_index(vma, pvmw.address);
225 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
226 /* PMD-mapped THP migration entry */
228 VM_BUG_ON_PAGE(PageHuge(page) || !PageTransCompound(page), page);
229 remove_migration_pmd(&pvmw, new);
235 pte = pte_mkold(mk_pte(new, READ_ONCE(vma->vm_page_prot)));
236 if (pte_swp_soft_dirty(*pvmw.pte))
237 pte = pte_mksoft_dirty(pte);
240 * Recheck VMA as permissions can change since migration started
242 entry = pte_to_swp_entry(*pvmw.pte);
243 if (is_write_migration_entry(entry))
244 pte = maybe_mkwrite(pte, vma);
246 if (unlikely(is_zone_device_page(new))) {
247 if (is_device_private_page(new)) {
248 entry = make_device_private_entry(new, pte_write(pte));
249 pte = swp_entry_to_pte(entry);
253 #ifdef CONFIG_HUGETLB_PAGE
255 pte = pte_mkhuge(pte);
256 pte = arch_make_huge_pte(pte, vma, new, 0);
257 set_huge_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte);
259 hugepage_add_anon_rmap(new, vma, pvmw.address);
261 page_dup_rmap(new, true);
265 set_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte);
268 page_add_anon_rmap(new, vma, pvmw.address, false);
270 page_add_file_rmap(new, false);
272 if (vma->vm_flags & VM_LOCKED && !PageTransCompound(new))
275 if (PageTransHuge(page) && PageMlocked(page))
276 clear_page_mlock(page);
278 /* No need to invalidate - it was non-present before */
279 update_mmu_cache(vma, pvmw.address, pvmw.pte);
286 * Get rid of all migration entries and replace them by
287 * references to the indicated page.
289 void remove_migration_ptes(struct page *old, struct page *new, bool locked)
291 struct rmap_walk_control rwc = {
292 .rmap_one = remove_migration_pte,
297 rmap_walk_locked(new, &rwc);
299 rmap_walk(new, &rwc);
303 * Something used the pte of a page under migration. We need to
304 * get to the page and wait until migration is finished.
305 * When we return from this function the fault will be retried.
307 void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
316 if (!is_swap_pte(pte))
319 entry = pte_to_swp_entry(pte);
320 if (!is_migration_entry(entry))
323 page = migration_entry_to_page(entry);
324 page = compound_head(page);
327 * Once page cache replacement of page migration started, page_count
328 * is zero; but we must not call put_and_wait_on_page_locked() without
329 * a ref. Use get_page_unless_zero(), and just fault again if it fails.
331 if (!get_page_unless_zero(page))
333 pte_unmap_unlock(ptep, ptl);
334 put_and_wait_on_page_locked(page);
337 pte_unmap_unlock(ptep, ptl);
340 void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
341 unsigned long address)
343 spinlock_t *ptl = pte_lockptr(mm, pmd);
344 pte_t *ptep = pte_offset_map(pmd, address);
345 __migration_entry_wait(mm, ptep, ptl);
348 void migration_entry_wait_huge(struct vm_area_struct *vma,
349 struct mm_struct *mm, pte_t *pte)
351 spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), mm, pte);
352 __migration_entry_wait(mm, pte, ptl);
355 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
356 void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd)
361 ptl = pmd_lock(mm, pmd);
362 if (!is_pmd_migration_entry(*pmd))
364 page = migration_entry_to_page(pmd_to_swp_entry(*pmd));
365 if (!get_page_unless_zero(page))
368 put_and_wait_on_page_locked(page);
375 static int expected_page_refs(struct address_space *mapping, struct page *page)
377 int expected_count = 1;
380 * Device public or private pages have an extra refcount as they are
383 expected_count += is_device_private_page(page);
385 expected_count += hpage_nr_pages(page) + page_has_private(page);
387 return expected_count;
391 * Replace the page in the mapping.
393 * The number of remaining references must be:
394 * 1 for anonymous pages without a mapping
395 * 2 for pages with a mapping
396 * 3 for pages with a mapping and PagePrivate/PagePrivate2 set.
398 int migrate_page_move_mapping(struct address_space *mapping,
399 struct page *newpage, struct page *page, int extra_count)
401 XA_STATE(xas, &mapping->i_pages, page_index(page));
402 struct zone *oldzone, *newzone;
404 int expected_count = expected_page_refs(mapping, page) + extra_count;
407 /* Anonymous page without mapping */
408 if (page_count(page) != expected_count)
411 /* No turning back from here */
412 newpage->index = page->index;
413 newpage->mapping = page->mapping;
414 if (PageSwapBacked(page))
415 __SetPageSwapBacked(newpage);
417 return MIGRATEPAGE_SUCCESS;
420 oldzone = page_zone(page);
421 newzone = page_zone(newpage);
424 if (page_count(page) != expected_count || xas_load(&xas) != page) {
425 xas_unlock_irq(&xas);
429 if (!page_ref_freeze(page, expected_count)) {
430 xas_unlock_irq(&xas);
435 * Now we know that no one else is looking at the page:
436 * no turning back from here.
438 newpage->index = page->index;
439 newpage->mapping = page->mapping;
440 page_ref_add(newpage, hpage_nr_pages(page)); /* add cache reference */
441 if (PageSwapBacked(page)) {
442 __SetPageSwapBacked(newpage);
443 if (PageSwapCache(page)) {
446 SetPageSwapCache(newpage);
447 for (i = 0; i < (1 << compound_order(page)); i++)
448 set_page_private(newpage + i,
449 page_private(page + i));
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 - hpage_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 __dec_node_state(oldzone->zone_pgdat, NR_FILE_PAGES);
494 __inc_node_state(newzone->zone_pgdat, NR_FILE_PAGES);
495 if (PageSwapBacked(page) && !PageSwapCache(page)) {
496 __dec_node_state(oldzone->zone_pgdat, NR_SHMEM);
497 __inc_node_state(newzone->zone_pgdat, NR_SHMEM);
499 if (dirty && mapping_cap_account_dirty(mapping)) {
500 __dec_node_state(oldzone->zone_pgdat, NR_FILE_DIRTY);
501 __dec_zone_state(oldzone, NR_ZONE_WRITE_PENDING);
502 __inc_node_state(newzone->zone_pgdat, NR_FILE_DIRTY);
503 __inc_zone_state(newzone, NR_ZONE_WRITE_PENDING);
508 return MIGRATEPAGE_SUCCESS;
510 EXPORT_SYMBOL(migrate_page_move_mapping);
513 * The expected number of remaining references is the same as that
514 * of migrate_page_move_mapping().
516 int migrate_huge_page_move_mapping(struct address_space *mapping,
517 struct page *newpage, struct page *page)
519 XA_STATE(xas, &mapping->i_pages, page_index(page));
523 expected_count = 2 + page_has_private(page);
524 if (page_count(page) != expected_count || xas_load(&xas) != page) {
525 xas_unlock_irq(&xas);
529 if (!page_ref_freeze(page, expected_count)) {
530 xas_unlock_irq(&xas);
534 newpage->index = page->index;
535 newpage->mapping = page->mapping;
539 xas_store(&xas, newpage);
541 page_ref_unfreeze(page, expected_count - 1);
543 xas_unlock_irq(&xas);
545 return MIGRATEPAGE_SUCCESS;
549 * Gigantic pages are so large that we do not guarantee that page++ pointer
550 * arithmetic will work across the entire page. We need something more
553 static void __copy_gigantic_page(struct page *dst, struct page *src,
557 struct page *dst_base = dst;
558 struct page *src_base = src;
560 for (i = 0; i < nr_pages; ) {
562 copy_highpage(dst, src);
565 dst = mem_map_next(dst, dst_base, i);
566 src = mem_map_next(src, src_base, i);
570 static void copy_huge_page(struct page *dst, struct page *src)
577 struct hstate *h = page_hstate(src);
578 nr_pages = pages_per_huge_page(h);
580 if (unlikely(nr_pages > MAX_ORDER_NR_PAGES)) {
581 __copy_gigantic_page(dst, src, nr_pages);
586 BUG_ON(!PageTransHuge(src));
587 nr_pages = hpage_nr_pages(src);
590 for (i = 0; i < nr_pages; i++) {
592 copy_highpage(dst + i, src + i);
597 * Copy the page to its new location
599 void migrate_page_states(struct page *newpage, struct page *page)
604 SetPageError(newpage);
605 if (PageReferenced(page))
606 SetPageReferenced(newpage);
607 if (PageUptodate(page))
608 SetPageUptodate(newpage);
609 if (TestClearPageActive(page)) {
610 VM_BUG_ON_PAGE(PageUnevictable(page), page);
611 SetPageActive(newpage);
612 } else if (TestClearPageUnevictable(page))
613 SetPageUnevictable(newpage);
614 if (PageWorkingset(page))
615 SetPageWorkingset(newpage);
616 if (PageChecked(page))
617 SetPageChecked(newpage);
618 if (PageMappedToDisk(page))
619 SetPageMappedToDisk(newpage);
621 /* Move dirty on pages not done by migrate_page_move_mapping() */
623 SetPageDirty(newpage);
625 if (page_is_young(page))
626 set_page_young(newpage);
627 if (page_is_idle(page))
628 set_page_idle(newpage);
631 * Copy NUMA information to the new page, to prevent over-eager
632 * future migrations of this same page.
634 cpupid = page_cpupid_xchg_last(page, -1);
635 page_cpupid_xchg_last(newpage, cpupid);
637 ksm_migrate_page(newpage, page);
639 * Please do not reorder this without considering how mm/ksm.c's
640 * get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache().
642 if (PageSwapCache(page))
643 ClearPageSwapCache(page);
644 ClearPagePrivate(page);
645 set_page_private(page, 0);
648 * If any waiters have accumulated on the new page then
651 if (PageWriteback(newpage))
652 end_page_writeback(newpage);
654 copy_page_owner(page, newpage);
656 mem_cgroup_migrate(page, newpage);
658 EXPORT_SYMBOL(migrate_page_states);
660 void migrate_page_copy(struct page *newpage, struct page *page)
662 if (PageHuge(page) || PageTransHuge(page))
663 copy_huge_page(newpage, page);
665 copy_highpage(newpage, page);
667 migrate_page_states(newpage, page);
669 EXPORT_SYMBOL(migrate_page_copy);
671 /************************************************************
672 * Migration functions
673 ***********************************************************/
676 * Common logic to directly migrate a single LRU page suitable for
677 * pages that do not use PagePrivate/PagePrivate2.
679 * Pages are locked upon entry and exit.
681 int migrate_page(struct address_space *mapping,
682 struct page *newpage, struct page *page,
683 enum migrate_mode mode)
687 BUG_ON(PageWriteback(page)); /* Writeback must be complete */
689 rc = migrate_page_move_mapping(mapping, newpage, page, 0);
691 if (rc != MIGRATEPAGE_SUCCESS)
694 if (mode != MIGRATE_SYNC_NO_COPY)
695 migrate_page_copy(newpage, page);
697 migrate_page_states(newpage, page);
698 return MIGRATEPAGE_SUCCESS;
700 EXPORT_SYMBOL(migrate_page);
703 /* Returns true if all buffers are successfully locked */
704 static bool buffer_migrate_lock_buffers(struct buffer_head *head,
705 enum migrate_mode mode)
707 struct buffer_head *bh = head;
709 /* Simple case, sync compaction */
710 if (mode != MIGRATE_ASYNC) {
713 bh = bh->b_this_page;
715 } while (bh != head);
720 /* async case, we cannot block on lock_buffer so use trylock_buffer */
722 if (!trylock_buffer(bh)) {
724 * We failed to lock the buffer and cannot stall in
725 * async migration. Release the taken locks
727 struct buffer_head *failed_bh = bh;
729 while (bh != failed_bh) {
731 bh = bh->b_this_page;
736 bh = bh->b_this_page;
737 } while (bh != head);
741 static int __buffer_migrate_page(struct address_space *mapping,
742 struct page *newpage, struct page *page, enum migrate_mode mode,
745 struct buffer_head *bh, *head;
749 if (!page_has_buffers(page))
750 return migrate_page(mapping, newpage, page, mode);
752 /* Check whether page does not have extra refs before we do more work */
753 expected_count = expected_page_refs(mapping, page);
754 if (page_count(page) != expected_count)
757 head = page_buffers(page);
758 if (!buffer_migrate_lock_buffers(head, mode))
763 bool invalidated = false;
767 spin_lock(&mapping->private_lock);
770 if (atomic_read(&bh->b_count)) {
774 bh = bh->b_this_page;
775 } while (bh != head);
781 spin_unlock(&mapping->private_lock);
782 invalidate_bh_lrus();
784 goto recheck_buffers;
788 rc = migrate_page_move_mapping(mapping, newpage, page, 0);
789 if (rc != MIGRATEPAGE_SUCCESS)
792 ClearPagePrivate(page);
793 set_page_private(newpage, page_private(page));
794 set_page_private(page, 0);
800 set_bh_page(bh, newpage, bh_offset(bh));
801 bh = bh->b_this_page;
803 } while (bh != head);
805 SetPagePrivate(newpage);
807 if (mode != MIGRATE_SYNC_NO_COPY)
808 migrate_page_copy(newpage, page);
810 migrate_page_states(newpage, page);
812 rc = MIGRATEPAGE_SUCCESS;
815 spin_unlock(&mapping->private_lock);
819 bh = bh->b_this_page;
821 } while (bh != head);
827 * Migration function for pages with buffers. This function can only be used
828 * if the underlying filesystem guarantees that no other references to "page"
829 * exist. For example attached buffer heads are accessed only under page lock.
831 int buffer_migrate_page(struct address_space *mapping,
832 struct page *newpage, struct page *page, enum migrate_mode mode)
834 return __buffer_migrate_page(mapping, newpage, page, mode, false);
836 EXPORT_SYMBOL(buffer_migrate_page);
839 * Same as above except that this variant is more careful and checks that there
840 * are also no buffer head references. This function is the right one for
841 * mappings where buffer heads are directly looked up and referenced (such as
842 * block device mappings).
844 int buffer_migrate_page_norefs(struct address_space *mapping,
845 struct page *newpage, struct page *page, enum migrate_mode mode)
847 return __buffer_migrate_page(mapping, newpage, page, mode, true);
852 * Writeback a page to clean the dirty state
854 static int writeout(struct address_space *mapping, struct page *page)
856 struct writeback_control wbc = {
857 .sync_mode = WB_SYNC_NONE,
860 .range_end = LLONG_MAX,
865 if (!mapping->a_ops->writepage)
866 /* No write method for the address space */
869 if (!clear_page_dirty_for_io(page))
870 /* Someone else already triggered a write */
874 * A dirty page may imply that the underlying filesystem has
875 * the page on some queue. So the page must be clean for
876 * migration. Writeout may mean we loose the lock and the
877 * page state is no longer what we checked for earlier.
878 * At this point we know that the migration attempt cannot
881 remove_migration_ptes(page, page, false);
883 rc = mapping->a_ops->writepage(page, &wbc);
885 if (rc != AOP_WRITEPAGE_ACTIVATE)
886 /* unlocked. Relock */
889 return (rc < 0) ? -EIO : -EAGAIN;
893 * Default handling if a filesystem does not provide a migration function.
895 static int fallback_migrate_page(struct address_space *mapping,
896 struct page *newpage, struct page *page, enum migrate_mode mode)
898 if (PageDirty(page)) {
899 /* Only writeback pages in full synchronous migration */
902 case MIGRATE_SYNC_NO_COPY:
907 return writeout(mapping, page);
911 * Buffers may be managed in a filesystem specific way.
912 * We must have no buffers or drop them.
914 if (page_has_private(page) &&
915 !try_to_release_page(page, GFP_KERNEL))
916 return mode == MIGRATE_SYNC ? -EAGAIN : -EBUSY;
918 return migrate_page(mapping, newpage, page, mode);
922 * Move a page to a newly allocated page
923 * The page is locked and all ptes have been successfully removed.
925 * The new page will have replaced the old page if this function
930 * MIGRATEPAGE_SUCCESS - success
932 static int move_to_new_page(struct page *newpage, struct page *page,
933 enum migrate_mode mode)
935 struct address_space *mapping;
937 bool is_lru = !__PageMovable(page);
939 VM_BUG_ON_PAGE(!PageLocked(page), page);
940 VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
942 mapping = page_mapping(page);
944 if (likely(is_lru)) {
946 rc = migrate_page(mapping, newpage, page, mode);
947 else if (mapping->a_ops->migratepage)
949 * Most pages have a mapping and most filesystems
950 * provide a migratepage callback. Anonymous pages
951 * are part of swap space which also has its own
952 * migratepage callback. This is the most common path
953 * for page migration.
955 rc = mapping->a_ops->migratepage(mapping, newpage,
958 rc = fallback_migrate_page(mapping, newpage,
962 * In case of non-lru page, it could be released after
963 * isolation step. In that case, we shouldn't try migration.
965 VM_BUG_ON_PAGE(!PageIsolated(page), page);
966 if (!PageMovable(page)) {
967 rc = MIGRATEPAGE_SUCCESS;
968 __ClearPageIsolated(page);
972 rc = mapping->a_ops->migratepage(mapping, newpage,
974 WARN_ON_ONCE(rc == MIGRATEPAGE_SUCCESS &&
975 !PageIsolated(page));
979 * When successful, old pagecache page->mapping must be cleared before
980 * page is freed; but stats require that PageAnon be left as PageAnon.
982 if (rc == MIGRATEPAGE_SUCCESS) {
983 if (__PageMovable(page)) {
984 VM_BUG_ON_PAGE(!PageIsolated(page), page);
987 * We clear PG_movable under page_lock so any compactor
988 * cannot try to migrate this page.
990 __ClearPageIsolated(page);
994 * Anonymous and movable page->mapping will be cleard by
995 * free_pages_prepare so don't reset it here for keeping
996 * the type to work PageAnon, for example.
998 if (!PageMappingFlags(page))
999 page->mapping = NULL;
1001 if (likely(!is_zone_device_page(newpage))) {
1002 int i, nr = compound_nr(newpage);
1004 for (i = 0; i < nr; i++)
1005 flush_dcache_page(newpage + i);
1012 static int __unmap_and_move(struct page *page, struct page *newpage,
1013 int force, enum migrate_mode mode)
1016 int page_was_mapped = 0;
1017 struct anon_vma *anon_vma = NULL;
1018 bool is_lru = !__PageMovable(page);
1020 if (!trylock_page(page)) {
1021 if (!force || mode == MIGRATE_ASYNC)
1025 * It's not safe for direct compaction to call lock_page.
1026 * For example, during page readahead pages are added locked
1027 * to the LRU. Later, when the IO completes the pages are
1028 * marked uptodate and unlocked. However, the queueing
1029 * could be merging multiple pages for one bio (e.g.
1030 * mpage_readpages). If an allocation happens for the
1031 * second or third page, the process can end up locking
1032 * the same page twice and deadlocking. Rather than
1033 * trying to be clever about what pages can be locked,
1034 * avoid the use of lock_page for direct compaction
1037 if (current->flags & PF_MEMALLOC)
1043 if (PageWriteback(page)) {
1045 * Only in the case of a full synchronous migration is it
1046 * necessary to wait for PageWriteback. In the async case,
1047 * the retry loop is too short and in the sync-light case,
1048 * the overhead of stalling is too much
1052 case MIGRATE_SYNC_NO_COPY:
1060 wait_on_page_writeback(page);
1064 * By try_to_unmap(), page->mapcount goes down to 0 here. In this case,
1065 * we cannot notice that anon_vma is freed while we migrates a page.
1066 * This get_anon_vma() delays freeing anon_vma pointer until the end
1067 * of migration. File cache pages are no problem because of page_lock()
1068 * File Caches may use write_page() or lock_page() in migration, then,
1069 * just care Anon page here.
1071 * Only page_get_anon_vma() understands the subtleties of
1072 * getting a hold on an anon_vma from outside one of its mms.
1073 * But if we cannot get anon_vma, then we won't need it anyway,
1074 * because that implies that the anon page is no longer mapped
1075 * (and cannot be remapped so long as we hold the page lock).
1077 if (PageAnon(page) && !PageKsm(page))
1078 anon_vma = page_get_anon_vma(page);
1081 * Block others from accessing the new page when we get around to
1082 * establishing additional references. We are usually the only one
1083 * holding a reference to newpage at this point. We used to have a BUG
1084 * here if trylock_page(newpage) fails, but would like to allow for
1085 * cases where there might be a race with the previous use of newpage.
1086 * This is much like races on refcount of oldpage: just don't BUG().
1088 if (unlikely(!trylock_page(newpage)))
1091 if (unlikely(!is_lru)) {
1092 rc = move_to_new_page(newpage, page, mode);
1093 goto out_unlock_both;
1097 * Corner case handling:
1098 * 1. When a new swap-cache page is read into, it is added to the LRU
1099 * and treated as swapcache but it has no rmap yet.
1100 * Calling try_to_unmap() against a page->mapping==NULL page will
1101 * trigger a BUG. So handle it here.
1102 * 2. An orphaned page (see truncate_complete_page) might have
1103 * fs-private metadata. The page can be picked up due to memory
1104 * offlining. Everywhere else except page reclaim, the page is
1105 * invisible to the vm, so the page can not be migrated. So try to
1106 * free the metadata, so the page can be freed.
1108 if (!page->mapping) {
1109 VM_BUG_ON_PAGE(PageAnon(page), page);
1110 if (page_has_private(page)) {
1111 try_to_free_buffers(page);
1112 goto out_unlock_both;
1114 } else if (page_mapped(page)) {
1115 /* Establish migration ptes */
1116 VM_BUG_ON_PAGE(PageAnon(page) && !PageKsm(page) && !anon_vma,
1119 TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
1120 page_was_mapped = 1;
1123 if (!page_mapped(page))
1124 rc = move_to_new_page(newpage, page, mode);
1126 if (page_was_mapped)
1127 remove_migration_ptes(page,
1128 rc == MIGRATEPAGE_SUCCESS ? newpage : page, false);
1131 unlock_page(newpage);
1133 /* Drop an anon_vma reference if we took one */
1135 put_anon_vma(anon_vma);
1139 * If migration is successful, decrease refcount of the newpage
1140 * which will not free the page because new page owner increased
1141 * refcounter. As well, if it is LRU page, add the page to LRU
1142 * list in here. Use the old state of the isolated source page to
1143 * determine if we migrated a LRU page. newpage was already unlocked
1144 * and possibly modified by its owner - don't rely on the page
1147 if (rc == MIGRATEPAGE_SUCCESS) {
1148 if (unlikely(!is_lru))
1151 putback_lru_page(newpage);
1158 * gcc 4.7 and 4.8 on arm get an ICEs when inlining unmap_and_move(). Work
1161 #if defined(CONFIG_ARM) && \
1162 defined(GCC_VERSION) && GCC_VERSION < 40900 && GCC_VERSION >= 40700
1163 #define ICE_noinline noinline
1165 #define ICE_noinline
1169 * Obtain the lock on page, remove all ptes and migrate the page
1170 * to the newly allocated page in newpage.
1172 static ICE_noinline int unmap_and_move(new_page_t get_new_page,
1173 free_page_t put_new_page,
1174 unsigned long private, struct page *page,
1175 int force, enum migrate_mode mode,
1176 enum migrate_reason reason)
1178 int rc = MIGRATEPAGE_SUCCESS;
1179 struct page *newpage;
1181 if (!thp_migration_supported() && PageTransHuge(page))
1184 newpage = get_new_page(page, private);
1188 if (page_count(page) == 1) {
1189 /* page was freed from under us. So we are done. */
1190 ClearPageActive(page);
1191 ClearPageUnevictable(page);
1192 if (unlikely(__PageMovable(page))) {
1194 if (!PageMovable(page))
1195 __ClearPageIsolated(page);
1199 put_new_page(newpage, private);
1205 rc = __unmap_and_move(page, newpage, force, mode);
1206 if (rc == MIGRATEPAGE_SUCCESS)
1207 set_page_owner_migrate_reason(newpage, reason);
1210 if (rc != -EAGAIN) {
1212 * A page that has been migrated has all references
1213 * removed and will be freed. A page that has not been
1214 * migrated will have kepts its references and be
1217 list_del(&page->lru);
1220 * Compaction can migrate also non-LRU pages which are
1221 * not accounted to NR_ISOLATED_*. They can be recognized
1224 if (likely(!__PageMovable(page)))
1225 mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON +
1226 page_is_file_cache(page), -hpage_nr_pages(page));
1230 * If migration is successful, releases reference grabbed during
1231 * isolation. Otherwise, restore the page to right list unless
1234 if (rc == MIGRATEPAGE_SUCCESS) {
1236 if (reason == MR_MEMORY_FAILURE) {
1238 * Set PG_HWPoison on just freed page
1239 * intentionally. Although it's rather weird,
1240 * it's how HWPoison flag works at the moment.
1242 if (set_hwpoison_free_buddy_page(page))
1243 num_poisoned_pages_inc();
1246 if (rc != -EAGAIN) {
1247 if (likely(!__PageMovable(page))) {
1248 putback_lru_page(page);
1253 if (PageMovable(page))
1254 putback_movable_page(page);
1256 __ClearPageIsolated(page);
1262 put_new_page(newpage, private);
1271 * Counterpart of unmap_and_move_page() for hugepage migration.
1273 * This function doesn't wait the completion of hugepage I/O
1274 * because there is no race between I/O and migration for hugepage.
1275 * Note that currently hugepage I/O occurs only in direct I/O
1276 * where no lock is held and PG_writeback is irrelevant,
1277 * and writeback status of all subpages are counted in the reference
1278 * count of the head page (i.e. if all subpages of a 2MB hugepage are
1279 * under direct I/O, the reference of the head page is 512 and a bit more.)
1280 * This means that when we try to migrate hugepage whose subpages are
1281 * doing direct I/O, some references remain after try_to_unmap() and
1282 * hugepage migration fails without data corruption.
1284 * There is also no race when direct I/O is issued on the page under migration,
1285 * because then pte is replaced with migration swap entry and direct I/O code
1286 * will wait in the page fault for migration to complete.
1288 static int unmap_and_move_huge_page(new_page_t get_new_page,
1289 free_page_t put_new_page, unsigned long private,
1290 struct page *hpage, int force,
1291 enum migrate_mode mode, int reason)
1294 int page_was_mapped = 0;
1295 struct page *new_hpage;
1296 struct anon_vma *anon_vma = NULL;
1299 * Migratability of hugepages depends on architectures and their size.
1300 * This check is necessary because some callers of hugepage migration
1301 * like soft offline and memory hotremove don't walk through page
1302 * tables or check whether the hugepage is pmd-based or not before
1303 * kicking migration.
1305 if (!hugepage_migration_supported(page_hstate(hpage))) {
1306 putback_active_hugepage(hpage);
1310 new_hpage = get_new_page(hpage, private);
1314 if (!trylock_page(hpage)) {
1319 case MIGRATE_SYNC_NO_COPY:
1328 * Check for pages which are in the process of being freed. Without
1329 * page_mapping() set, hugetlbfs specific move page routine will not
1330 * be called and we could leak usage counts for subpools.
1332 if (page_private(hpage) && !page_mapping(hpage)) {
1337 if (PageAnon(hpage))
1338 anon_vma = page_get_anon_vma(hpage);
1340 if (unlikely(!trylock_page(new_hpage)))
1343 if (page_mapped(hpage)) {
1345 TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
1346 page_was_mapped = 1;
1349 if (!page_mapped(hpage))
1350 rc = move_to_new_page(new_hpage, hpage, mode);
1352 if (page_was_mapped)
1353 remove_migration_ptes(hpage,
1354 rc == MIGRATEPAGE_SUCCESS ? new_hpage : hpage, false);
1356 unlock_page(new_hpage);
1360 put_anon_vma(anon_vma);
1362 if (rc == MIGRATEPAGE_SUCCESS) {
1363 move_hugetlb_state(hpage, new_hpage, reason);
1364 put_new_page = NULL;
1371 putback_active_hugepage(hpage);
1374 * If migration was not successful and there's a freeing callback, use
1375 * it. Otherwise, put_page() will drop the reference grabbed during
1379 put_new_page(new_hpage, private);
1381 putback_active_hugepage(new_hpage);
1387 * migrate_pages - migrate the pages specified in a list, to the free pages
1388 * supplied as the target for the page migration
1390 * @from: The list of pages to be migrated.
1391 * @get_new_page: The function used to allocate free pages to be used
1392 * as the target of the page migration.
1393 * @put_new_page: The function used to free target pages if migration
1394 * fails, or NULL if no special handling is necessary.
1395 * @private: Private data to be passed on to get_new_page()
1396 * @mode: The migration mode that specifies the constraints for
1397 * page migration, if any.
1398 * @reason: The reason for page migration.
1400 * The function returns after 10 attempts or if no pages are movable any more
1401 * because the list has become empty or no retryable pages exist any more.
1402 * The caller should call putback_movable_pages() to return pages to the LRU
1403 * or free list only if ret != 0.
1405 * Returns the number of pages that were not migrated, or an error code.
1407 int migrate_pages(struct list_head *from, new_page_t get_new_page,
1408 free_page_t put_new_page, unsigned long private,
1409 enum migrate_mode mode, int reason)
1413 int nr_succeeded = 0;
1417 int swapwrite = current->flags & PF_SWAPWRITE;
1421 current->flags |= PF_SWAPWRITE;
1423 for(pass = 0; pass < 10 && retry; pass++) {
1426 list_for_each_entry_safe(page, page2, from, lru) {
1431 rc = unmap_and_move_huge_page(get_new_page,
1432 put_new_page, private, page,
1433 pass > 2, mode, reason);
1435 rc = unmap_and_move(get_new_page, put_new_page,
1436 private, page, pass > 2, mode,
1442 * THP migration might be unsupported or the
1443 * allocation could've failed so we should
1444 * retry on the same page with the THP split
1447 * Head page is retried immediately and tail
1448 * pages are added to the tail of the list so
1449 * we encounter them after the rest of the list
1452 if (PageTransHuge(page) && !PageHuge(page)) {
1454 rc = split_huge_page_to_list(page, from);
1457 list_safe_reset_next(page, page2, lru);
1466 case MIGRATEPAGE_SUCCESS:
1471 * Permanent failure (-EBUSY, -ENOSYS, etc.):
1472 * unlike -EAGAIN case, the failed page is
1473 * removed from migration page list and not
1474 * retried in the next outer loop.
1485 count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded);
1487 count_vm_events(PGMIGRATE_FAIL, nr_failed);
1488 trace_mm_migrate_pages(nr_succeeded, nr_failed, mode, reason);
1491 current->flags &= ~PF_SWAPWRITE;
1498 static int store_status(int __user *status, int start, int value, int nr)
1501 if (put_user(value, status + start))
1509 static int do_move_pages_to_node(struct mm_struct *mm,
1510 struct list_head *pagelist, int node)
1514 if (list_empty(pagelist))
1517 err = migrate_pages(pagelist, alloc_new_node_page, NULL, node,
1518 MIGRATE_SYNC, MR_SYSCALL);
1520 putback_movable_pages(pagelist);
1525 * Resolves the given address to a struct page, isolates it from the LRU and
1526 * puts it to the given pagelist.
1528 * errno - if the page cannot be found/isolated
1529 * 0 - when it doesn't have to be migrated because it is already on the
1531 * 1 - when it has been queued
1533 static int add_page_for_migration(struct mm_struct *mm, unsigned long addr,
1534 int node, struct list_head *pagelist, bool migrate_all)
1536 struct vm_area_struct *vma;
1538 unsigned int follflags;
1541 down_read(&mm->mmap_sem);
1543 vma = find_vma(mm, addr);
1544 if (!vma || addr < vma->vm_start || !vma_migratable(vma))
1547 /* FOLL_DUMP to ignore special (like zero) pages */
1548 follflags = FOLL_GET | FOLL_DUMP;
1549 page = follow_page(vma, addr, follflags);
1551 err = PTR_ERR(page);
1560 if (page_to_nid(page) == node)
1564 if (page_mapcount(page) > 1 && !migrate_all)
1567 if (PageHuge(page)) {
1568 if (PageHead(page)) {
1569 isolate_huge_page(page, pagelist);
1575 head = compound_head(page);
1576 err = isolate_lru_page(head);
1581 list_add_tail(&head->lru, pagelist);
1582 mod_node_page_state(page_pgdat(head),
1583 NR_ISOLATED_ANON + page_is_file_cache(head),
1584 hpage_nr_pages(head));
1588 * Either remove the duplicate refcount from
1589 * isolate_lru_page() or drop the page ref if it was
1594 up_read(&mm->mmap_sem);
1599 * Migrate an array of page address onto an array of nodes and fill
1600 * the corresponding array of status.
1602 static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
1603 unsigned long nr_pages,
1604 const void __user * __user *pages,
1605 const int __user *nodes,
1606 int __user *status, int flags)
1608 int current_node = NUMA_NO_NODE;
1609 LIST_HEAD(pagelist);
1615 for (i = start = 0; i < nr_pages; i++) {
1616 const void __user *p;
1621 if (get_user(p, pages + i))
1623 if (get_user(node, nodes + i))
1625 addr = (unsigned long)untagged_addr(p);
1628 if (node < 0 || node >= MAX_NUMNODES)
1630 if (!node_state(node, N_MEMORY))
1634 if (!node_isset(node, task_nodes))
1637 if (current_node == NUMA_NO_NODE) {
1638 current_node = node;
1640 } else if (node != current_node) {
1641 err = do_move_pages_to_node(mm, &pagelist, current_node);
1644 * Positive err means the number of failed
1645 * pages to migrate. Since we are going to
1646 * abort and return the number of non-migrated
1647 * pages, so need to incude the rest of the
1648 * nr_pages that have not been attempted as
1652 err += nr_pages - i - 1;
1655 err = store_status(status, start, current_node, i - start);
1659 current_node = node;
1663 * Errors in the page lookup or isolation are not fatal and we simply
1664 * report them via status
1666 err = add_page_for_migration(mm, addr, current_node,
1667 &pagelist, flags & MPOL_MF_MOVE_ALL);
1670 /* The page is already on the target node */
1671 err = store_status(status, i, current_node, 1);
1675 } else if (err > 0) {
1676 /* The page is successfully queued for migration */
1680 err = store_status(status, i, err, 1);
1684 err = do_move_pages_to_node(mm, &pagelist, current_node);
1687 err += nr_pages - i - 1;
1691 err = store_status(status, start, current_node, i - start);
1695 current_node = NUMA_NO_NODE;
1698 if (list_empty(&pagelist))
1701 /* Make sure we do not overwrite the existing error */
1702 err1 = do_move_pages_to_node(mm, &pagelist, current_node);
1704 * Don't have to report non-attempted pages here since:
1705 * - If the above loop is done gracefully all pages have been
1707 * - If the above loop is aborted it means a fatal error
1708 * happened, should return ret.
1711 err1 = store_status(status, start, current_node, i - start);
1719 * Determine the nodes of an array of pages and store it in an array of status.
1721 static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
1722 const void __user **pages, int *status)
1726 down_read(&mm->mmap_sem);
1728 for (i = 0; i < nr_pages; i++) {
1729 unsigned long addr = (unsigned long)(*pages);
1730 struct vm_area_struct *vma;
1734 vma = find_vma(mm, addr);
1735 if (!vma || addr < vma->vm_start)
1738 /* FOLL_DUMP to ignore special (like zero) pages */
1739 page = follow_page(vma, addr, FOLL_DUMP);
1741 err = PTR_ERR(page);
1745 err = page ? page_to_nid(page) : -ENOENT;
1753 up_read(&mm->mmap_sem);
1757 * Determine the nodes of a user array of pages and store it in
1758 * a user array of status.
1760 static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
1761 const void __user * __user *pages,
1764 #define DO_PAGES_STAT_CHUNK_NR 16
1765 const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR];
1766 int chunk_status[DO_PAGES_STAT_CHUNK_NR];
1769 unsigned long chunk_nr;
1771 chunk_nr = nr_pages;
1772 if (chunk_nr > DO_PAGES_STAT_CHUNK_NR)
1773 chunk_nr = DO_PAGES_STAT_CHUNK_NR;
1775 if (copy_from_user(chunk_pages, pages, chunk_nr * sizeof(*chunk_pages)))
1778 do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status);
1780 if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status)))
1785 nr_pages -= chunk_nr;
1787 return nr_pages ? -EFAULT : 0;
1791 * Move a list of pages in the address space of the currently executing
1794 static int kernel_move_pages(pid_t pid, unsigned long nr_pages,
1795 const void __user * __user *pages,
1796 const int __user *nodes,
1797 int __user *status, int flags)
1799 struct task_struct *task;
1800 struct mm_struct *mm;
1802 nodemask_t task_nodes;
1805 if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL))
1808 if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
1811 /* Find the mm_struct */
1813 task = pid ? find_task_by_vpid(pid) : current;
1818 get_task_struct(task);
1821 * Check if this process has the right to modify the specified
1822 * process. Use the regular "ptrace_may_access()" checks.
1824 if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) {
1831 err = security_task_movememory(task);
1835 task_nodes = cpuset_mems_allowed(task);
1836 mm = get_task_mm(task);
1837 put_task_struct(task);
1843 err = do_pages_move(mm, task_nodes, nr_pages, pages,
1844 nodes, status, flags);
1846 err = do_pages_stat(mm, nr_pages, pages, status);
1852 put_task_struct(task);
1856 SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages,
1857 const void __user * __user *, pages,
1858 const int __user *, nodes,
1859 int __user *, status, int, flags)
1861 return kernel_move_pages(pid, nr_pages, pages, nodes, status, flags);
1864 #ifdef CONFIG_COMPAT
1865 COMPAT_SYSCALL_DEFINE6(move_pages, pid_t, pid, compat_ulong_t, nr_pages,
1866 compat_uptr_t __user *, pages32,
1867 const int __user *, nodes,
1868 int __user *, status,
1871 const void __user * __user *pages;
1874 pages = compat_alloc_user_space(nr_pages * sizeof(void *));
1875 for (i = 0; i < nr_pages; i++) {
1878 if (get_user(p, pages32 + i) ||
1879 put_user(compat_ptr(p), pages + i))
1882 return kernel_move_pages(pid, nr_pages, pages, nodes, status, flags);
1884 #endif /* CONFIG_COMPAT */
1886 #ifdef CONFIG_NUMA_BALANCING
1888 * Returns true if this is a safe migration target node for misplaced NUMA
1889 * pages. Currently it only checks the watermarks which crude
1891 static bool migrate_balanced_pgdat(struct pglist_data *pgdat,
1892 unsigned long nr_migrate_pages)
1896 for (z = pgdat->nr_zones - 1; z >= 0; z--) {
1897 struct zone *zone = pgdat->node_zones + z;
1899 if (!populated_zone(zone))
1902 /* Avoid waking kswapd by allocating pages_to_migrate pages. */
1903 if (!zone_watermark_ok(zone, 0,
1904 high_wmark_pages(zone) +
1913 static struct page *alloc_misplaced_dst_page(struct page *page,
1916 int nid = (int) data;
1917 struct page *newpage;
1919 newpage = __alloc_pages_node(nid,
1920 (GFP_HIGHUSER_MOVABLE |
1921 __GFP_THISNODE | __GFP_NOMEMALLOC |
1922 __GFP_NORETRY | __GFP_NOWARN) &
1928 static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
1932 VM_BUG_ON_PAGE(compound_order(page) && !PageTransHuge(page), page);
1934 /* Avoid migrating to a node that is nearly full */
1935 if (!migrate_balanced_pgdat(pgdat, compound_nr(page)))
1938 if (isolate_lru_page(page))
1942 * migrate_misplaced_transhuge_page() skips page migration's usual
1943 * check on page_count(), so we must do it here, now that the page
1944 * has been isolated: a GUP pin, or any other pin, prevents migration.
1945 * The expected page count is 3: 1 for page's mapcount and 1 for the
1946 * caller's pin and 1 for the reference taken by isolate_lru_page().
1948 if (PageTransHuge(page) && page_count(page) != 3) {
1949 putback_lru_page(page);
1953 page_lru = page_is_file_cache(page);
1954 mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + page_lru,
1955 hpage_nr_pages(page));
1958 * Isolating the page has taken another reference, so the
1959 * caller's reference can be safely dropped without the page
1960 * disappearing underneath us during migration.
1966 bool pmd_trans_migrating(pmd_t pmd)
1968 struct page *page = pmd_page(pmd);
1969 return PageLocked(page);
1973 * Attempt to migrate a misplaced page to the specified destination
1974 * node. Caller is expected to have an elevated reference count on
1975 * the page that will be dropped by this function before returning.
1977 int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
1980 pg_data_t *pgdat = NODE_DATA(node);
1983 LIST_HEAD(migratepages);
1986 * Don't migrate file pages that are mapped in multiple processes
1987 * with execute permissions as they are probably shared libraries.
1989 if (page_mapcount(page) != 1 && page_is_file_cache(page) &&
1990 (vma->vm_flags & VM_EXEC))
1994 * Also do not migrate dirty pages as not all filesystems can move
1995 * dirty pages in MIGRATE_ASYNC mode which is a waste of cycles.
1997 if (page_is_file_cache(page) && PageDirty(page))
2000 isolated = numamigrate_isolate_page(pgdat, page);
2004 list_add(&page->lru, &migratepages);
2005 nr_remaining = migrate_pages(&migratepages, alloc_misplaced_dst_page,
2006 NULL, node, MIGRATE_ASYNC,
2009 if (!list_empty(&migratepages)) {
2010 list_del(&page->lru);
2011 dec_node_page_state(page, NR_ISOLATED_ANON +
2012 page_is_file_cache(page));
2013 putback_lru_page(page);
2017 count_vm_numa_event(NUMA_PAGE_MIGRATE);
2018 BUG_ON(!list_empty(&migratepages));
2025 #endif /* CONFIG_NUMA_BALANCING */
2027 #if defined(CONFIG_NUMA_BALANCING) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
2029 * Migrates a THP to a given target node. page must be locked and is unlocked
2032 int migrate_misplaced_transhuge_page(struct mm_struct *mm,
2033 struct vm_area_struct *vma,
2034 pmd_t *pmd, pmd_t entry,
2035 unsigned long address,
2036 struct page *page, int node)
2039 pg_data_t *pgdat = NODE_DATA(node);
2041 struct page *new_page = NULL;
2042 int page_lru = page_is_file_cache(page);
2043 unsigned long start = address & HPAGE_PMD_MASK;
2045 new_page = alloc_pages_node(node,
2046 (GFP_TRANSHUGE_LIGHT | __GFP_THISNODE),
2050 prep_transhuge_page(new_page);
2052 isolated = numamigrate_isolate_page(pgdat, page);
2058 /* Prepare a page as a migration target */
2059 __SetPageLocked(new_page);
2060 if (PageSwapBacked(page))
2061 __SetPageSwapBacked(new_page);
2063 /* anon mapping, we can simply copy page->mapping to the new page: */
2064 new_page->mapping = page->mapping;
2065 new_page->index = page->index;
2066 /* flush the cache before copying using the kernel virtual address */
2067 flush_cache_range(vma, start, start + HPAGE_PMD_SIZE);
2068 migrate_page_copy(new_page, page);
2069 WARN_ON(PageLRU(new_page));
2071 /* Recheck the target PMD */
2072 ptl = pmd_lock(mm, pmd);
2073 if (unlikely(!pmd_same(*pmd, entry) || !page_ref_freeze(page, 2))) {
2076 /* Reverse changes made by migrate_page_copy() */
2077 if (TestClearPageActive(new_page))
2078 SetPageActive(page);
2079 if (TestClearPageUnevictable(new_page))
2080 SetPageUnevictable(page);
2082 unlock_page(new_page);
2083 put_page(new_page); /* Free it */
2085 /* Retake the callers reference and putback on LRU */
2087 putback_lru_page(page);
2088 mod_node_page_state(page_pgdat(page),
2089 NR_ISOLATED_ANON + page_lru, -HPAGE_PMD_NR);
2094 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
2095 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
2098 * Overwrite the old entry under pagetable lock and establish
2099 * the new PTE. Any parallel GUP will either observe the old
2100 * page blocking on the page lock, block on the page table
2101 * lock or observe the new page. The SetPageUptodate on the
2102 * new page and page_add_new_anon_rmap guarantee the copy is
2103 * visible before the pagetable update.
2105 page_add_anon_rmap(new_page, vma, start, true);
2107 * At this point the pmd is numa/protnone (i.e. non present) and the TLB
2108 * has already been flushed globally. So no TLB can be currently
2109 * caching this non present pmd mapping. There's no need to clear the
2110 * pmd before doing set_pmd_at(), nor to flush the TLB after
2111 * set_pmd_at(). Clearing the pmd here would introduce a race
2112 * condition against MADV_DONTNEED, because MADV_DONTNEED only holds the
2113 * mmap_sem for reading. If the pmd is set to NULL at any given time,
2114 * MADV_DONTNEED won't wait on the pmd lock and it'll skip clearing this
2117 set_pmd_at(mm, start, pmd, entry);
2118 update_mmu_cache_pmd(vma, address, &entry);
2120 page_ref_unfreeze(page, 2);
2121 mlock_migrate_page(new_page, page);
2122 page_remove_rmap(page, true);
2123 set_page_owner_migrate_reason(new_page, MR_NUMA_MISPLACED);
2127 /* Take an "isolate" reference and put new page on the LRU. */
2129 putback_lru_page(new_page);
2131 unlock_page(new_page);
2133 put_page(page); /* Drop the rmap reference */
2134 put_page(page); /* Drop the LRU isolation reference */
2136 count_vm_events(PGMIGRATE_SUCCESS, HPAGE_PMD_NR);
2137 count_vm_numa_events(NUMA_PAGE_MIGRATE, HPAGE_PMD_NR);
2139 mod_node_page_state(page_pgdat(page),
2140 NR_ISOLATED_ANON + page_lru,
2145 count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR);
2146 ptl = pmd_lock(mm, pmd);
2147 if (pmd_same(*pmd, entry)) {
2148 entry = pmd_modify(entry, vma->vm_page_prot);
2149 set_pmd_at(mm, start, pmd, entry);
2150 update_mmu_cache_pmd(vma, address, &entry);
2159 #endif /* CONFIG_NUMA_BALANCING */
2161 #endif /* CONFIG_NUMA */
2163 #ifdef CONFIG_DEVICE_PRIVATE
2164 static int migrate_vma_collect_hole(unsigned long start,
2166 struct mm_walk *walk)
2168 struct migrate_vma *migrate = walk->private;
2171 for (addr = start & PAGE_MASK; addr < end; addr += PAGE_SIZE) {
2172 migrate->src[migrate->npages] = MIGRATE_PFN_MIGRATE;
2173 migrate->dst[migrate->npages] = 0;
2181 static int migrate_vma_collect_skip(unsigned long start,
2183 struct mm_walk *walk)
2185 struct migrate_vma *migrate = walk->private;
2188 for (addr = start & PAGE_MASK; addr < end; addr += PAGE_SIZE) {
2189 migrate->dst[migrate->npages] = 0;
2190 migrate->src[migrate->npages++] = 0;
2196 static int migrate_vma_collect_pmd(pmd_t *pmdp,
2197 unsigned long start,
2199 struct mm_walk *walk)
2201 struct migrate_vma *migrate = walk->private;
2202 struct vm_area_struct *vma = walk->vma;
2203 struct mm_struct *mm = vma->vm_mm;
2204 unsigned long addr = start, unmapped = 0;
2209 if (pmd_none(*pmdp))
2210 return migrate_vma_collect_hole(start, end, walk);
2212 if (pmd_trans_huge(*pmdp)) {
2215 ptl = pmd_lock(mm, pmdp);
2216 if (unlikely(!pmd_trans_huge(*pmdp))) {
2221 page = pmd_page(*pmdp);
2222 if (is_huge_zero_page(page)) {
2224 split_huge_pmd(vma, pmdp, addr);
2225 if (pmd_trans_unstable(pmdp))
2226 return migrate_vma_collect_skip(start, end,
2233 if (unlikely(!trylock_page(page)))
2234 return migrate_vma_collect_skip(start, end,
2236 ret = split_huge_page(page);
2240 return migrate_vma_collect_skip(start, end,
2242 if (pmd_none(*pmdp))
2243 return migrate_vma_collect_hole(start, end,
2248 if (unlikely(pmd_bad(*pmdp)))
2249 return migrate_vma_collect_skip(start, end, walk);
2251 ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
2252 arch_enter_lazy_mmu_mode();
2254 for (; addr < end; addr += PAGE_SIZE, ptep++) {
2255 unsigned long mpfn, pfn;
2262 if (pte_none(pte)) {
2263 mpfn = MIGRATE_PFN_MIGRATE;
2268 if (!pte_present(pte)) {
2272 * Only care about unaddressable device page special
2273 * page table entry. Other special swap entries are not
2274 * migratable, and we ignore regular swapped page.
2276 entry = pte_to_swp_entry(pte);
2277 if (!is_device_private_entry(entry))
2280 page = device_private_entry_to_page(entry);
2281 mpfn = migrate_pfn(page_to_pfn(page)) |
2282 MIGRATE_PFN_MIGRATE;
2283 if (is_write_device_private_entry(entry))
2284 mpfn |= MIGRATE_PFN_WRITE;
2287 if (is_zero_pfn(pfn)) {
2288 mpfn = MIGRATE_PFN_MIGRATE;
2292 page = vm_normal_page(migrate->vma, addr, pte);
2293 mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
2294 mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0;
2297 /* FIXME support THP */
2298 if (!page || !page->mapping || PageTransCompound(page)) {
2304 * By getting a reference on the page we pin it and that blocks
2305 * any kind of migration. Side effect is that it "freezes" the
2308 * We drop this reference after isolating the page from the lru
2309 * for non device page (device page are not on the lru and thus
2310 * can't be dropped from it).
2316 * Optimize for the common case where page is only mapped once
2317 * in one process. If we can lock the page, then we can safely
2318 * set up a special migration page table entry now.
2320 if (trylock_page(page)) {
2323 mpfn |= MIGRATE_PFN_LOCKED;
2324 ptep_get_and_clear(mm, addr, ptep);
2326 /* Setup special migration page table entry */
2327 entry = make_migration_entry(page, mpfn &
2329 swp_pte = swp_entry_to_pte(entry);
2330 if (pte_soft_dirty(pte))
2331 swp_pte = pte_swp_mksoft_dirty(swp_pte);
2332 set_pte_at(mm, addr, ptep, swp_pte);
2335 * This is like regular unmap: we remove the rmap and
2336 * drop page refcount. Page won't be freed, as we took
2337 * a reference just above.
2339 page_remove_rmap(page, false);
2342 if (pte_present(pte))
2347 migrate->dst[migrate->npages] = 0;
2348 migrate->src[migrate->npages++] = mpfn;
2351 /* Only flush the TLB if we actually modified any entries */
2353 flush_tlb_range(walk->vma, start, end);
2355 arch_leave_lazy_mmu_mode();
2356 pte_unmap_unlock(ptep - 1, ptl);
2361 static const struct mm_walk_ops migrate_vma_walk_ops = {
2362 .pmd_entry = migrate_vma_collect_pmd,
2363 .pte_hole = migrate_vma_collect_hole,
2367 * migrate_vma_collect() - collect pages over a range of virtual addresses
2368 * @migrate: migrate struct containing all migration information
2370 * This will walk the CPU page table. For each virtual address backed by a
2371 * valid page, it updates the src array and takes a reference on the page, in
2372 * order to pin the page until we lock it and unmap it.
2374 static void migrate_vma_collect(struct migrate_vma *migrate)
2376 struct mmu_notifier_range range;
2378 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, NULL,
2379 migrate->vma->vm_mm, migrate->start, migrate->end);
2380 mmu_notifier_invalidate_range_start(&range);
2382 walk_page_range(migrate->vma->vm_mm, migrate->start, migrate->end,
2383 &migrate_vma_walk_ops, migrate);
2385 mmu_notifier_invalidate_range_end(&range);
2386 migrate->end = migrate->start + (migrate->npages << PAGE_SHIFT);
2390 * migrate_vma_check_page() - check if page is pinned or not
2391 * @page: struct page to check
2393 * Pinned pages cannot be migrated. This is the same test as in
2394 * migrate_page_move_mapping(), except that here we allow migration of a
2397 static bool migrate_vma_check_page(struct page *page)
2400 * One extra ref because caller holds an extra reference, either from
2401 * isolate_lru_page() for a regular page, or migrate_vma_collect() for
2407 * FIXME support THP (transparent huge page), it is bit more complex to
2408 * check them than regular pages, because they can be mapped with a pmd
2409 * or with a pte (split pte mapping).
2411 if (PageCompound(page))
2414 /* Page from ZONE_DEVICE have one extra reference */
2415 if (is_zone_device_page(page)) {
2417 * Private page can never be pin as they have no valid pte and
2418 * GUP will fail for those. Yet if there is a pending migration
2419 * a thread might try to wait on the pte migration entry and
2420 * will bump the page reference count. Sadly there is no way to
2421 * differentiate a regular pin from migration wait. Hence to
2422 * avoid 2 racing thread trying to migrate back to CPU to enter
2423 * infinite loop (one stoping migration because the other is
2424 * waiting on pte migration entry). We always return true here.
2426 * FIXME proper solution is to rework migration_entry_wait() so
2427 * it does not need to take a reference on page.
2429 return is_device_private_page(page);
2432 /* For file back page */
2433 if (page_mapping(page))
2434 extra += 1 + page_has_private(page);
2436 if ((page_count(page) - extra) > page_mapcount(page))
2443 * migrate_vma_prepare() - lock pages and isolate them from the lru
2444 * @migrate: migrate struct containing all migration information
2446 * This locks pages that have been collected by migrate_vma_collect(). Once each
2447 * page is locked it is isolated from the lru (for non-device pages). Finally,
2448 * the ref taken by migrate_vma_collect() is dropped, as locked pages cannot be
2449 * migrated by concurrent kernel threads.
2451 static void migrate_vma_prepare(struct migrate_vma *migrate)
2453 const unsigned long npages = migrate->npages;
2454 const unsigned long start = migrate->start;
2455 unsigned long addr, i, restore = 0;
2456 bool allow_drain = true;
2460 for (i = 0; (i < npages) && migrate->cpages; i++) {
2461 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2467 if (!(migrate->src[i] & MIGRATE_PFN_LOCKED)) {
2469 * Because we are migrating several pages there can be
2470 * a deadlock between 2 concurrent migration where each
2471 * are waiting on each other page lock.
2473 * Make migrate_vma() a best effort thing and backoff
2474 * for any page we can not lock right away.
2476 if (!trylock_page(page)) {
2477 migrate->src[i] = 0;
2483 migrate->src[i] |= MIGRATE_PFN_LOCKED;
2486 /* ZONE_DEVICE pages are not on LRU */
2487 if (!is_zone_device_page(page)) {
2488 if (!PageLRU(page) && allow_drain) {
2489 /* Drain CPU's pagevec */
2490 lru_add_drain_all();
2491 allow_drain = false;
2494 if (isolate_lru_page(page)) {
2496 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2500 migrate->src[i] = 0;
2508 /* Drop the reference we took in collect */
2512 if (!migrate_vma_check_page(page)) {
2514 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2518 if (!is_zone_device_page(page)) {
2520 putback_lru_page(page);
2523 migrate->src[i] = 0;
2527 if (!is_zone_device_page(page))
2528 putback_lru_page(page);
2535 for (i = 0, addr = start; i < npages && restore; i++, addr += PAGE_SIZE) {
2536 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2538 if (!page || (migrate->src[i] & MIGRATE_PFN_MIGRATE))
2541 remove_migration_pte(page, migrate->vma, addr, page);
2543 migrate->src[i] = 0;
2551 * migrate_vma_unmap() - replace page mapping with special migration pte entry
2552 * @migrate: migrate struct containing all migration information
2554 * Replace page mapping (CPU page table pte) with a special migration pte entry
2555 * and check again if it has been pinned. Pinned pages are restored because we
2556 * cannot migrate them.
2558 * This is the last step before we call the device driver callback to allocate
2559 * destination memory and copy contents of original page over to new page.
2561 static void migrate_vma_unmap(struct migrate_vma *migrate)
2563 int flags = TTU_MIGRATION | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
2564 const unsigned long npages = migrate->npages;
2565 const unsigned long start = migrate->start;
2566 unsigned long addr, i, restore = 0;
2568 for (i = 0; i < npages; i++) {
2569 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2571 if (!page || !(migrate->src[i] & MIGRATE_PFN_MIGRATE))
2574 if (page_mapped(page)) {
2575 try_to_unmap(page, flags);
2576 if (page_mapped(page))
2580 if (migrate_vma_check_page(page))
2584 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2589 for (addr = start, i = 0; i < npages && restore; addr += PAGE_SIZE, i++) {
2590 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2592 if (!page || (migrate->src[i] & MIGRATE_PFN_MIGRATE))
2595 remove_migration_ptes(page, page, false);
2597 migrate->src[i] = 0;
2601 if (is_zone_device_page(page))
2604 putback_lru_page(page);
2609 * migrate_vma_setup() - prepare to migrate a range of memory
2610 * @args: contains the vma, start, and and pfns arrays for the migration
2612 * Returns: negative errno on failures, 0 when 0 or more pages were migrated
2615 * Prepare to migrate a range of memory virtual address range by collecting all
2616 * the pages backing each virtual address in the range, saving them inside the
2617 * src array. Then lock those pages and unmap them. Once the pages are locked
2618 * and unmapped, check whether each page is pinned or not. Pages that aren't
2619 * pinned have the MIGRATE_PFN_MIGRATE flag set (by this function) in the
2620 * corresponding src array entry. Then restores any pages that are pinned, by
2621 * remapping and unlocking those pages.
2623 * The caller should then allocate destination memory and copy source memory to
2624 * it for all those entries (ie with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE
2625 * flag set). Once these are allocated and copied, the caller must update each
2626 * corresponding entry in the dst array with the pfn value of the destination
2627 * page and with the MIGRATE_PFN_VALID and MIGRATE_PFN_LOCKED flags set
2628 * (destination pages must have their struct pages locked, via lock_page()).
2630 * Note that the caller does not have to migrate all the pages that are marked
2631 * with MIGRATE_PFN_MIGRATE flag in src array unless this is a migration from
2632 * device memory to system memory. If the caller cannot migrate a device page
2633 * back to system memory, then it must return VM_FAULT_SIGBUS, which has severe
2634 * consequences for the userspace process, so it must be avoided if at all
2637 * For empty entries inside CPU page table (pte_none() or pmd_none() is true) we
2638 * do set MIGRATE_PFN_MIGRATE flag inside the corresponding source array thus
2639 * allowing the caller to allocate device memory for those unback virtual
2640 * address. For this the caller simply has to allocate device memory and
2641 * properly set the destination entry like for regular migration. Note that
2642 * this can still fails and thus inside the device driver must check if the
2643 * migration was successful for those entries after calling migrate_vma_pages()
2644 * just like for regular migration.
2646 * After that, the callers must call migrate_vma_pages() to go over each entry
2647 * in the src array that has the MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag
2648 * set. If the corresponding entry in dst array has MIGRATE_PFN_VALID flag set,
2649 * then migrate_vma_pages() to migrate struct page information from the source
2650 * struct page to the destination struct page. If it fails to migrate the
2651 * struct page information, then it clears the MIGRATE_PFN_MIGRATE flag in the
2654 * At this point all successfully migrated pages have an entry in the src
2655 * array with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag set and the dst
2656 * array entry with MIGRATE_PFN_VALID flag set.
2658 * Once migrate_vma_pages() returns the caller may inspect which pages were
2659 * successfully migrated, and which were not. Successfully migrated pages will
2660 * have the MIGRATE_PFN_MIGRATE flag set for their src array entry.
2662 * It is safe to update device page table after migrate_vma_pages() because
2663 * both destination and source page are still locked, and the mmap_sem is held
2664 * in read mode (hence no one can unmap the range being migrated).
2666 * Once the caller is done cleaning up things and updating its page table (if it
2667 * chose to do so, this is not an obligation) it finally calls
2668 * migrate_vma_finalize() to update the CPU page table to point to new pages
2669 * for successfully migrated pages or otherwise restore the CPU page table to
2670 * point to the original source pages.
2672 int migrate_vma_setup(struct migrate_vma *args)
2674 long nr_pages = (args->end - args->start) >> PAGE_SHIFT;
2676 args->start &= PAGE_MASK;
2677 args->end &= PAGE_MASK;
2678 if (!args->vma || is_vm_hugetlb_page(args->vma) ||
2679 (args->vma->vm_flags & VM_SPECIAL) || vma_is_dax(args->vma))
2683 if (args->start < args->vma->vm_start ||
2684 args->start >= args->vma->vm_end)
2686 if (args->end <= args->vma->vm_start || args->end > args->vma->vm_end)
2688 if (!args->src || !args->dst)
2691 memset(args->src, 0, sizeof(*args->src) * nr_pages);
2695 migrate_vma_collect(args);
2698 migrate_vma_prepare(args);
2700 migrate_vma_unmap(args);
2703 * At this point pages are locked and unmapped, and thus they have
2704 * stable content and can safely be copied to destination memory that
2705 * is allocated by the drivers.
2710 EXPORT_SYMBOL(migrate_vma_setup);
2712 static void migrate_vma_insert_page(struct migrate_vma *migrate,
2718 struct vm_area_struct *vma = migrate->vma;
2719 struct mm_struct *mm = vma->vm_mm;
2720 struct mem_cgroup *memcg;
2730 /* Only allow populating anonymous memory */
2731 if (!vma_is_anonymous(vma))
2734 pgdp = pgd_offset(mm, addr);
2735 p4dp = p4d_alloc(mm, pgdp, addr);
2738 pudp = pud_alloc(mm, p4dp, addr);
2741 pmdp = pmd_alloc(mm, pudp, addr);
2745 if (pmd_trans_huge(*pmdp) || pmd_devmap(*pmdp))
2749 * Use pte_alloc() instead of pte_alloc_map(). We can't run
2750 * pte_offset_map() on pmds where a huge pmd might be created
2751 * from a different thread.
2753 * pte_alloc_map() is safe to use under down_write(mmap_sem) or when
2754 * parallel threads are excluded by other means.
2756 * Here we only have down_read(mmap_sem).
2758 if (pte_alloc(mm, pmdp))
2761 /* See the comment in pte_alloc_one_map() */
2762 if (unlikely(pmd_trans_unstable(pmdp)))
2765 if (unlikely(anon_vma_prepare(vma)))
2767 if (mem_cgroup_try_charge(page, vma->vm_mm, GFP_KERNEL, &memcg, false))
2771 * The memory barrier inside __SetPageUptodate makes sure that
2772 * preceding stores to the page contents become visible before
2773 * the set_pte_at() write.
2775 __SetPageUptodate(page);
2777 if (is_zone_device_page(page)) {
2778 if (is_device_private_page(page)) {
2779 swp_entry_t swp_entry;
2781 swp_entry = make_device_private_entry(page, vma->vm_flags & VM_WRITE);
2782 entry = swp_entry_to_pte(swp_entry);
2785 * For now we only support migrating to un-addressable
2788 pr_warn_once("Unsupported ZONE_DEVICE page type.\n");
2792 entry = mk_pte(page, vma->vm_page_prot);
2793 if (vma->vm_flags & VM_WRITE)
2794 entry = pte_mkwrite(pte_mkdirty(entry));
2797 ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
2799 if (pte_present(*ptep)) {
2800 unsigned long pfn = pte_pfn(*ptep);
2802 if (!is_zero_pfn(pfn)) {
2803 pte_unmap_unlock(ptep, ptl);
2804 mem_cgroup_cancel_charge(page, memcg, false);
2808 } else if (!pte_none(*ptep)) {
2809 pte_unmap_unlock(ptep, ptl);
2810 mem_cgroup_cancel_charge(page, memcg, false);
2815 * Check for usefaultfd but do not deliver the fault. Instead,
2818 if (userfaultfd_missing(vma)) {
2819 pte_unmap_unlock(ptep, ptl);
2820 mem_cgroup_cancel_charge(page, memcg, false);
2824 inc_mm_counter(mm, MM_ANONPAGES);
2825 page_add_new_anon_rmap(page, vma, addr, false);
2826 mem_cgroup_commit_charge(page, memcg, false, false);
2827 if (!is_zone_device_page(page))
2828 lru_cache_add_active_or_unevictable(page, vma);
2832 flush_cache_page(vma, addr, pte_pfn(*ptep));
2833 ptep_clear_flush_notify(vma, addr, ptep);
2834 set_pte_at_notify(mm, addr, ptep, entry);
2835 update_mmu_cache(vma, addr, ptep);
2837 /* No need to invalidate - it was non-present before */
2838 set_pte_at(mm, addr, ptep, entry);
2839 update_mmu_cache(vma, addr, ptep);
2842 pte_unmap_unlock(ptep, ptl);
2843 *src = MIGRATE_PFN_MIGRATE;
2847 *src &= ~MIGRATE_PFN_MIGRATE;
2851 * migrate_vma_pages() - migrate meta-data from src page to dst page
2852 * @migrate: migrate struct containing all migration information
2854 * This migrates struct page meta-data from source struct page to destination
2855 * struct page. This effectively finishes the migration from source page to the
2858 void migrate_vma_pages(struct migrate_vma *migrate)
2860 const unsigned long npages = migrate->npages;
2861 const unsigned long start = migrate->start;
2862 struct mmu_notifier_range range;
2863 unsigned long addr, i;
2864 bool notified = false;
2866 for (i = 0, addr = start; i < npages; addr += PAGE_SIZE, i++) {
2867 struct page *newpage = migrate_pfn_to_page(migrate->dst[i]);
2868 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2869 struct address_space *mapping;
2873 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2878 if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE)) {
2884 mmu_notifier_range_init(&range,
2885 MMU_NOTIFY_CLEAR, 0,
2887 migrate->vma->vm_mm,
2888 addr, migrate->end);
2889 mmu_notifier_invalidate_range_start(&range);
2891 migrate_vma_insert_page(migrate, addr, newpage,
2897 mapping = page_mapping(page);
2899 if (is_zone_device_page(newpage)) {
2900 if (is_device_private_page(newpage)) {
2902 * For now only support private anonymous when
2903 * migrating to un-addressable device memory.
2906 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2911 * Other types of ZONE_DEVICE page are not
2914 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2919 r = migrate_page(mapping, newpage, page, MIGRATE_SYNC_NO_COPY);
2920 if (r != MIGRATEPAGE_SUCCESS)
2921 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2925 * No need to double call mmu_notifier->invalidate_range() callback as
2926 * the above ptep_clear_flush_notify() inside migrate_vma_insert_page()
2927 * did already call it.
2930 mmu_notifier_invalidate_range_only_end(&range);
2932 EXPORT_SYMBOL(migrate_vma_pages);
2935 * migrate_vma_finalize() - restore CPU page table entry
2936 * @migrate: migrate struct containing all migration information
2938 * This replaces the special migration pte entry with either a mapping to the
2939 * new page if migration was successful for that page, or to the original page
2942 * This also unlocks the pages and puts them back on the lru, or drops the extra
2943 * refcount, for device pages.
2945 void migrate_vma_finalize(struct migrate_vma *migrate)
2947 const unsigned long npages = migrate->npages;
2950 for (i = 0; i < npages; i++) {
2951 struct page *newpage = migrate_pfn_to_page(migrate->dst[i]);
2952 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2956 unlock_page(newpage);
2962 if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE) || !newpage) {
2964 unlock_page(newpage);
2970 remove_migration_ptes(page, newpage, false);
2974 if (is_zone_device_page(page))
2977 putback_lru_page(page);
2979 if (newpage != page) {
2980 unlock_page(newpage);
2981 if (is_zone_device_page(newpage))
2984 putback_lru_page(newpage);
2988 EXPORT_SYMBOL(migrate_vma_finalize);
2989 #endif /* CONFIG_DEVICE_PRIVATE */