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/pfn_t.h>
42 #include <linux/memremap.h>
43 #include <linux/userfaultfd_k.h>
44 #include <linux/balloon_compaction.h>
45 #include <linux/mmu_notifier.h>
46 #include <linux/page_idle.h>
47 #include <linux/page_owner.h>
48 #include <linux/sched/mm.h>
49 #include <linux/ptrace.h>
51 #include <asm/tlbflush.h>
53 #define CREATE_TRACE_POINTS
54 #include <trace/events/migrate.h>
59 * migrate_prep() needs to be called before we start compiling a list of pages
60 * to be migrated using isolate_lru_page(). If scheduling work on other CPUs is
61 * undesirable, use migrate_prep_local()
63 int migrate_prep(void)
66 * Clear the LRU lists so pages can be isolated.
67 * Note that pages may be moved off the LRU after we have
68 * drained them. Those pages will fail to migrate like other
69 * pages that may be busy.
76 /* Do the necessary work of migrate_prep but not if it involves other CPUs */
77 int migrate_prep_local(void)
84 int isolate_movable_page(struct page *page, isolate_mode_t mode)
86 struct address_space *mapping;
89 * Avoid burning cycles with pages that are yet under __free_pages(),
90 * or just got freed under us.
92 * In case we 'win' a race for a movable page being freed under us and
93 * raise its refcount preventing __free_pages() from doing its job
94 * the put_page() at the end of this block will take care of
95 * release this page, thus avoiding a nasty leakage.
97 if (unlikely(!get_page_unless_zero(page)))
101 * Check PageMovable before holding a PG_lock because page's owner
102 * assumes anybody doesn't touch PG_lock of newly allocated page
103 * so unconditionally grapping the lock ruins page's owner side.
105 if (unlikely(!__PageMovable(page)))
108 * As movable pages are not isolated from LRU lists, concurrent
109 * compaction threads can race against page migration functions
110 * as well as race against the releasing a page.
112 * In order to avoid having an already isolated movable page
113 * being (wrongly) re-isolated while it is under migration,
114 * or to avoid attempting to isolate pages being released,
115 * lets be sure we have the page lock
116 * before proceeding with the movable page isolation steps.
118 if (unlikely(!trylock_page(page)))
121 if (!PageMovable(page) || PageIsolated(page))
122 goto out_no_isolated;
124 mapping = page_mapping(page);
125 VM_BUG_ON_PAGE(!mapping, page);
127 if (!mapping->a_ops->isolate_page(page, mode))
128 goto out_no_isolated;
130 /* Driver shouldn't use PG_isolated bit of page->flags */
131 WARN_ON_ONCE(PageIsolated(page));
132 __SetPageIsolated(page);
145 /* It should be called on page which is PG_movable */
146 void putback_movable_page(struct page *page)
148 struct address_space *mapping;
150 VM_BUG_ON_PAGE(!PageLocked(page), page);
151 VM_BUG_ON_PAGE(!PageMovable(page), page);
152 VM_BUG_ON_PAGE(!PageIsolated(page), page);
154 mapping = page_mapping(page);
155 mapping->a_ops->putback_page(page);
156 __ClearPageIsolated(page);
160 * Put previously isolated pages back onto the appropriate lists
161 * from where they were once taken off for compaction/migration.
163 * This function shall be used whenever the isolated pageset has been
164 * built from lru, balloon, hugetlbfs page. See isolate_migratepages_range()
165 * and isolate_huge_page().
167 void putback_movable_pages(struct list_head *l)
172 list_for_each_entry_safe(page, page2, l, lru) {
173 if (unlikely(PageHuge(page))) {
174 putback_active_hugepage(page);
177 list_del(&page->lru);
179 * We isolated non-lru movable page so here we can use
180 * __PageMovable because LRU page's mapping cannot have
181 * PAGE_MAPPING_MOVABLE.
183 if (unlikely(__PageMovable(page))) {
184 VM_BUG_ON_PAGE(!PageIsolated(page), page);
186 if (PageMovable(page))
187 putback_movable_page(page);
189 __ClearPageIsolated(page);
193 mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON +
194 page_is_file_cache(page), -hpage_nr_pages(page));
195 putback_lru_page(page);
201 * Restore a potential migration pte to a working pte entry
203 static bool remove_migration_pte(struct page *page, struct vm_area_struct *vma,
204 unsigned long addr, void *old)
206 struct page_vma_mapped_walk pvmw = {
210 .flags = PVMW_SYNC | PVMW_MIGRATION,
216 VM_BUG_ON_PAGE(PageTail(page), page);
217 while (page_vma_mapped_walk(&pvmw)) {
221 new = page - pvmw.page->index +
222 linear_page_index(vma, pvmw.address);
224 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
225 /* PMD-mapped THP migration entry */
227 VM_BUG_ON_PAGE(PageHuge(page) || !PageTransCompound(page), page);
228 remove_migration_pmd(&pvmw, new);
234 pte = pte_mkold(mk_pte(new, READ_ONCE(vma->vm_page_prot)));
235 if (pte_swp_soft_dirty(*pvmw.pte))
236 pte = pte_mksoft_dirty(pte);
239 * Recheck VMA as permissions can change since migration started
241 entry = pte_to_swp_entry(*pvmw.pte);
242 if (is_write_migration_entry(entry))
243 pte = maybe_mkwrite(pte, vma);
245 if (unlikely(is_zone_device_page(new))) {
246 if (is_device_private_page(new)) {
247 entry = make_device_private_entry(new, pte_write(pte));
248 pte = swp_entry_to_pte(entry);
249 } else if (is_device_public_page(new)) {
250 pte = pte_mkdevmap(pte);
251 flush_dcache_page(new);
254 flush_dcache_page(new);
256 #ifdef CONFIG_HUGETLB_PAGE
258 pte = pte_mkhuge(pte);
259 pte = arch_make_huge_pte(pte, vma, new, 0);
260 set_huge_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte);
262 hugepage_add_anon_rmap(new, vma, pvmw.address);
264 page_dup_rmap(new, true);
268 set_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte);
271 page_add_anon_rmap(new, vma, pvmw.address, false);
273 page_add_file_rmap(new, false);
275 if (vma->vm_flags & VM_LOCKED && !PageTransCompound(new))
278 if (PageTransHuge(page) && PageMlocked(page))
279 clear_page_mlock(page);
281 /* No need to invalidate - it was non-present before */
282 update_mmu_cache(vma, pvmw.address, pvmw.pte);
289 * Get rid of all migration entries and replace them by
290 * references to the indicated page.
292 void remove_migration_ptes(struct page *old, struct page *new, bool locked)
294 struct rmap_walk_control rwc = {
295 .rmap_one = remove_migration_pte,
300 rmap_walk_locked(new, &rwc);
302 rmap_walk(new, &rwc);
306 * Something used the pte of a page under migration. We need to
307 * get to the page and wait until migration is finished.
308 * When we return from this function the fault will be retried.
310 void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
319 if (!is_swap_pte(pte))
322 entry = pte_to_swp_entry(pte);
323 if (!is_migration_entry(entry))
326 page = migration_entry_to_page(entry);
329 * Once page cache replacement of page migration started, page_count
330 * is zero; but we must not call put_and_wait_on_page_locked() without
331 * a ref. Use get_page_unless_zero(), and just fault again if it fails.
333 if (!get_page_unless_zero(page))
335 pte_unmap_unlock(ptep, ptl);
336 put_and_wait_on_page_locked(page);
339 pte_unmap_unlock(ptep, ptl);
342 void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
343 unsigned long address)
345 spinlock_t *ptl = pte_lockptr(mm, pmd);
346 pte_t *ptep = pte_offset_map(pmd, address);
347 __migration_entry_wait(mm, ptep, ptl);
350 void migration_entry_wait_huge(struct vm_area_struct *vma,
351 struct mm_struct *mm, pte_t *pte)
353 spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), mm, pte);
354 __migration_entry_wait(mm, pte, ptl);
357 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
358 void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd)
363 ptl = pmd_lock(mm, pmd);
364 if (!is_pmd_migration_entry(*pmd))
366 page = migration_entry_to_page(pmd_to_swp_entry(*pmd));
367 if (!get_page_unless_zero(page))
370 put_and_wait_on_page_locked(page);
378 /* Returns true if all buffers are successfully locked */
379 static bool buffer_migrate_lock_buffers(struct buffer_head *head,
380 enum migrate_mode mode)
382 struct buffer_head *bh = head;
384 /* Simple case, sync compaction */
385 if (mode != MIGRATE_ASYNC) {
389 bh = bh->b_this_page;
391 } while (bh != head);
396 /* async case, we cannot block on lock_buffer so use trylock_buffer */
399 if (!trylock_buffer(bh)) {
401 * We failed to lock the buffer and cannot stall in
402 * async migration. Release the taken locks
404 struct buffer_head *failed_bh = bh;
407 while (bh != failed_bh) {
410 bh = bh->b_this_page;
415 bh = bh->b_this_page;
416 } while (bh != head);
420 static inline bool buffer_migrate_lock_buffers(struct buffer_head *head,
421 enum migrate_mode mode)
425 #endif /* CONFIG_BLOCK */
427 static int expected_page_refs(struct page *page)
429 int expected_count = 1;
432 * Device public or private pages have an extra refcount as they are
435 expected_count += is_device_private_page(page);
436 expected_count += is_device_public_page(page);
437 if (page_mapping(page))
438 expected_count += hpage_nr_pages(page) + page_has_private(page);
440 return expected_count;
444 * Replace the page in the mapping.
446 * The number of remaining references must be:
447 * 1 for anonymous pages without a mapping
448 * 2 for pages with a mapping
449 * 3 for pages with a mapping and PagePrivate/PagePrivate2 set.
451 int migrate_page_move_mapping(struct address_space *mapping,
452 struct page *newpage, struct page *page,
453 struct buffer_head *head, enum migrate_mode mode,
456 XA_STATE(xas, &mapping->i_pages, page_index(page));
457 struct zone *oldzone, *newzone;
459 int expected_count = expected_page_refs(page) + extra_count;
462 /* Anonymous page without mapping */
463 if (page_count(page) != expected_count)
466 /* No turning back from here */
467 newpage->index = page->index;
468 newpage->mapping = page->mapping;
469 if (PageSwapBacked(page))
470 __SetPageSwapBacked(newpage);
472 return MIGRATEPAGE_SUCCESS;
475 oldzone = page_zone(page);
476 newzone = page_zone(newpage);
479 if (page_count(page) != expected_count || xas_load(&xas) != page) {
480 xas_unlock_irq(&xas);
484 if (!page_ref_freeze(page, expected_count)) {
485 xas_unlock_irq(&xas);
490 * Now we know that no one else is looking at the page:
491 * no turning back from here.
493 newpage->index = page->index;
494 newpage->mapping = page->mapping;
495 page_ref_add(newpage, hpage_nr_pages(page)); /* add cache reference */
496 if (PageSwapBacked(page)) {
497 __SetPageSwapBacked(newpage);
498 if (PageSwapCache(page)) {
499 SetPageSwapCache(newpage);
500 set_page_private(newpage, page_private(page));
503 VM_BUG_ON_PAGE(PageSwapCache(page), page);
506 /* Move dirty while page refs frozen and newpage not yet exposed */
507 dirty = PageDirty(page);
509 ClearPageDirty(page);
510 SetPageDirty(newpage);
513 xas_store(&xas, newpage);
514 if (PageTransHuge(page)) {
517 for (i = 1; i < HPAGE_PMD_NR; i++) {
519 xas_store(&xas, newpage + i);
524 * Drop cache reference from old page by unfreezing
525 * to one less reference.
526 * We know this isn't the last reference.
528 page_ref_unfreeze(page, expected_count - hpage_nr_pages(page));
531 /* Leave irq disabled to prevent preemption while updating stats */
534 * If moved to a different zone then also account
535 * the page for that zone. Other VM counters will be
536 * taken care of when we establish references to the
537 * new page and drop references to the old page.
539 * Note that anonymous pages are accounted for
540 * via NR_FILE_PAGES and NR_ANON_MAPPED if they
541 * are mapped to swap space.
543 if (newzone != oldzone) {
544 __dec_node_state(oldzone->zone_pgdat, NR_FILE_PAGES);
545 __inc_node_state(newzone->zone_pgdat, NR_FILE_PAGES);
546 if (PageSwapBacked(page) && !PageSwapCache(page)) {
547 __dec_node_state(oldzone->zone_pgdat, NR_SHMEM);
548 __inc_node_state(newzone->zone_pgdat, NR_SHMEM);
550 if (dirty && mapping_cap_account_dirty(mapping)) {
551 __dec_node_state(oldzone->zone_pgdat, NR_FILE_DIRTY);
552 __dec_zone_state(oldzone, NR_ZONE_WRITE_PENDING);
553 __inc_node_state(newzone->zone_pgdat, NR_FILE_DIRTY);
554 __inc_zone_state(newzone, NR_ZONE_WRITE_PENDING);
559 return MIGRATEPAGE_SUCCESS;
561 EXPORT_SYMBOL(migrate_page_move_mapping);
564 * The expected number of remaining references is the same as that
565 * of migrate_page_move_mapping().
567 int migrate_huge_page_move_mapping(struct address_space *mapping,
568 struct page *newpage, struct page *page)
570 XA_STATE(xas, &mapping->i_pages, page_index(page));
574 expected_count = 2 + page_has_private(page);
575 if (page_count(page) != expected_count || xas_load(&xas) != page) {
576 xas_unlock_irq(&xas);
580 if (!page_ref_freeze(page, expected_count)) {
581 xas_unlock_irq(&xas);
585 newpage->index = page->index;
586 newpage->mapping = page->mapping;
590 xas_store(&xas, newpage);
592 page_ref_unfreeze(page, expected_count - 1);
594 xas_unlock_irq(&xas);
596 return MIGRATEPAGE_SUCCESS;
600 * Gigantic pages are so large that we do not guarantee that page++ pointer
601 * arithmetic will work across the entire page. We need something more
604 static void __copy_gigantic_page(struct page *dst, struct page *src,
608 struct page *dst_base = dst;
609 struct page *src_base = src;
611 for (i = 0; i < nr_pages; ) {
613 copy_highpage(dst, src);
616 dst = mem_map_next(dst, dst_base, i);
617 src = mem_map_next(src, src_base, i);
621 static void copy_huge_page(struct page *dst, struct page *src)
628 struct hstate *h = page_hstate(src);
629 nr_pages = pages_per_huge_page(h);
631 if (unlikely(nr_pages > MAX_ORDER_NR_PAGES)) {
632 __copy_gigantic_page(dst, src, nr_pages);
637 BUG_ON(!PageTransHuge(src));
638 nr_pages = hpage_nr_pages(src);
641 for (i = 0; i < nr_pages; i++) {
643 copy_highpage(dst + i, src + i);
648 * Copy the page to its new location
650 void migrate_page_states(struct page *newpage, struct page *page)
655 SetPageError(newpage);
656 if (PageReferenced(page))
657 SetPageReferenced(newpage);
658 if (PageUptodate(page))
659 SetPageUptodate(newpage);
660 if (TestClearPageActive(page)) {
661 VM_BUG_ON_PAGE(PageUnevictable(page), page);
662 SetPageActive(newpage);
663 } else if (TestClearPageUnevictable(page))
664 SetPageUnevictable(newpage);
665 if (PageWorkingset(page))
666 SetPageWorkingset(newpage);
667 if (PageChecked(page))
668 SetPageChecked(newpage);
669 if (PageMappedToDisk(page))
670 SetPageMappedToDisk(newpage);
672 /* Move dirty on pages not done by migrate_page_move_mapping() */
674 SetPageDirty(newpage);
676 if (page_is_young(page))
677 set_page_young(newpage);
678 if (page_is_idle(page))
679 set_page_idle(newpage);
682 * Copy NUMA information to the new page, to prevent over-eager
683 * future migrations of this same page.
685 cpupid = page_cpupid_xchg_last(page, -1);
686 page_cpupid_xchg_last(newpage, cpupid);
688 ksm_migrate_page(newpage, page);
690 * Please do not reorder this without considering how mm/ksm.c's
691 * get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache().
693 if (PageSwapCache(page))
694 ClearPageSwapCache(page);
695 ClearPagePrivate(page);
696 set_page_private(page, 0);
699 * If any waiters have accumulated on the new page then
702 if (PageWriteback(newpage))
703 end_page_writeback(newpage);
705 copy_page_owner(page, newpage);
707 mem_cgroup_migrate(page, newpage);
709 EXPORT_SYMBOL(migrate_page_states);
711 void migrate_page_copy(struct page *newpage, struct page *page)
713 if (PageHuge(page) || PageTransHuge(page))
714 copy_huge_page(newpage, page);
716 copy_highpage(newpage, page);
718 migrate_page_states(newpage, page);
720 EXPORT_SYMBOL(migrate_page_copy);
722 /************************************************************
723 * Migration functions
724 ***********************************************************/
727 * Common logic to directly migrate a single LRU page suitable for
728 * pages that do not use PagePrivate/PagePrivate2.
730 * Pages are locked upon entry and exit.
732 int migrate_page(struct address_space *mapping,
733 struct page *newpage, struct page *page,
734 enum migrate_mode mode)
738 BUG_ON(PageWriteback(page)); /* Writeback must be complete */
740 rc = migrate_page_move_mapping(mapping, newpage, page, NULL, mode, 0);
742 if (rc != MIGRATEPAGE_SUCCESS)
745 if (mode != MIGRATE_SYNC_NO_COPY)
746 migrate_page_copy(newpage, page);
748 migrate_page_states(newpage, page);
749 return MIGRATEPAGE_SUCCESS;
751 EXPORT_SYMBOL(migrate_page);
755 * Migration function for pages with buffers. This function can only be used
756 * if the underlying filesystem guarantees that no other references to "page"
759 int buffer_migrate_page(struct address_space *mapping,
760 struct page *newpage, struct page *page, enum migrate_mode mode)
762 struct buffer_head *bh, *head;
766 if (!page_has_buffers(page))
767 return migrate_page(mapping, newpage, page, mode);
769 /* Check whether page does not have extra refs before we do more work */
770 expected_count = expected_page_refs(page);
771 if (page_count(page) != expected_count)
774 head = page_buffers(page);
775 if (!buffer_migrate_lock_buffers(head, mode))
778 rc = migrate_page_move_mapping(mapping, newpage, page, NULL, mode, 0);
779 if (rc != MIGRATEPAGE_SUCCESS)
782 ClearPagePrivate(page);
783 set_page_private(newpage, page_private(page));
784 set_page_private(page, 0);
790 set_bh_page(bh, newpage, bh_offset(bh));
791 bh = bh->b_this_page;
793 } while (bh != head);
795 SetPagePrivate(newpage);
797 if (mode != MIGRATE_SYNC_NO_COPY)
798 migrate_page_copy(newpage, page);
800 migrate_page_states(newpage, page);
802 rc = MIGRATEPAGE_SUCCESS;
808 bh = bh->b_this_page;
810 } while (bh != head);
814 EXPORT_SYMBOL(buffer_migrate_page);
818 * Writeback a page to clean the dirty state
820 static int writeout(struct address_space *mapping, struct page *page)
822 struct writeback_control wbc = {
823 .sync_mode = WB_SYNC_NONE,
826 .range_end = LLONG_MAX,
831 if (!mapping->a_ops->writepage)
832 /* No write method for the address space */
835 if (!clear_page_dirty_for_io(page))
836 /* Someone else already triggered a write */
840 * A dirty page may imply that the underlying filesystem has
841 * the page on some queue. So the page must be clean for
842 * migration. Writeout may mean we loose the lock and the
843 * page state is no longer what we checked for earlier.
844 * At this point we know that the migration attempt cannot
847 remove_migration_ptes(page, page, false);
849 rc = mapping->a_ops->writepage(page, &wbc);
851 if (rc != AOP_WRITEPAGE_ACTIVATE)
852 /* unlocked. Relock */
855 return (rc < 0) ? -EIO : -EAGAIN;
859 * Default handling if a filesystem does not provide a migration function.
861 static int fallback_migrate_page(struct address_space *mapping,
862 struct page *newpage, struct page *page, enum migrate_mode mode)
864 if (PageDirty(page)) {
865 /* Only writeback pages in full synchronous migration */
868 case MIGRATE_SYNC_NO_COPY:
873 return writeout(mapping, page);
877 * Buffers may be managed in a filesystem specific way.
878 * We must have no buffers or drop them.
880 if (page_has_private(page) &&
881 !try_to_release_page(page, GFP_KERNEL))
884 return migrate_page(mapping, newpage, page, mode);
888 * Move a page to a newly allocated page
889 * The page is locked and all ptes have been successfully removed.
891 * The new page will have replaced the old page if this function
896 * MIGRATEPAGE_SUCCESS - success
898 static int move_to_new_page(struct page *newpage, struct page *page,
899 enum migrate_mode mode)
901 struct address_space *mapping;
903 bool is_lru = !__PageMovable(page);
905 VM_BUG_ON_PAGE(!PageLocked(page), page);
906 VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
908 mapping = page_mapping(page);
910 if (likely(is_lru)) {
912 rc = migrate_page(mapping, newpage, page, mode);
913 else if (mapping->a_ops->migratepage)
915 * Most pages have a mapping and most filesystems
916 * provide a migratepage callback. Anonymous pages
917 * are part of swap space which also has its own
918 * migratepage callback. This is the most common path
919 * for page migration.
921 rc = mapping->a_ops->migratepage(mapping, newpage,
924 rc = fallback_migrate_page(mapping, newpage,
928 * In case of non-lru page, it could be released after
929 * isolation step. In that case, we shouldn't try migration.
931 VM_BUG_ON_PAGE(!PageIsolated(page), page);
932 if (!PageMovable(page)) {
933 rc = MIGRATEPAGE_SUCCESS;
934 __ClearPageIsolated(page);
938 rc = mapping->a_ops->migratepage(mapping, newpage,
940 WARN_ON_ONCE(rc == MIGRATEPAGE_SUCCESS &&
941 !PageIsolated(page));
945 * When successful, old pagecache page->mapping must be cleared before
946 * page is freed; but stats require that PageAnon be left as PageAnon.
948 if (rc == MIGRATEPAGE_SUCCESS) {
949 if (__PageMovable(page)) {
950 VM_BUG_ON_PAGE(!PageIsolated(page), page);
953 * We clear PG_movable under page_lock so any compactor
954 * cannot try to migrate this page.
956 __ClearPageIsolated(page);
960 * Anonymous and movable page->mapping will be cleard by
961 * free_pages_prepare so don't reset it here for keeping
962 * the type to work PageAnon, for example.
964 if (!PageMappingFlags(page))
965 page->mapping = NULL;
971 static int __unmap_and_move(struct page *page, struct page *newpage,
972 int force, enum migrate_mode mode)
975 int page_was_mapped = 0;
976 struct anon_vma *anon_vma = NULL;
977 bool is_lru = !__PageMovable(page);
979 if (!trylock_page(page)) {
980 if (!force || mode == MIGRATE_ASYNC)
984 * It's not safe for direct compaction to call lock_page.
985 * For example, during page readahead pages are added locked
986 * to the LRU. Later, when the IO completes the pages are
987 * marked uptodate and unlocked. However, the queueing
988 * could be merging multiple pages for one bio (e.g.
989 * mpage_readpages). If an allocation happens for the
990 * second or third page, the process can end up locking
991 * the same page twice and deadlocking. Rather than
992 * trying to be clever about what pages can be locked,
993 * avoid the use of lock_page for direct compaction
996 if (current->flags & PF_MEMALLOC)
1002 if (PageWriteback(page)) {
1004 * Only in the case of a full synchronous migration is it
1005 * necessary to wait for PageWriteback. In the async case,
1006 * the retry loop is too short and in the sync-light case,
1007 * the overhead of stalling is too much
1011 case MIGRATE_SYNC_NO_COPY:
1019 wait_on_page_writeback(page);
1023 * By try_to_unmap(), page->mapcount goes down to 0 here. In this case,
1024 * we cannot notice that anon_vma is freed while we migrates a page.
1025 * This get_anon_vma() delays freeing anon_vma pointer until the end
1026 * of migration. File cache pages are no problem because of page_lock()
1027 * File Caches may use write_page() or lock_page() in migration, then,
1028 * just care Anon page here.
1030 * Only page_get_anon_vma() understands the subtleties of
1031 * getting a hold on an anon_vma from outside one of its mms.
1032 * But if we cannot get anon_vma, then we won't need it anyway,
1033 * because that implies that the anon page is no longer mapped
1034 * (and cannot be remapped so long as we hold the page lock).
1036 if (PageAnon(page) && !PageKsm(page))
1037 anon_vma = page_get_anon_vma(page);
1040 * Block others from accessing the new page when we get around to
1041 * establishing additional references. We are usually the only one
1042 * holding a reference to newpage at this point. We used to have a BUG
1043 * here if trylock_page(newpage) fails, but would like to allow for
1044 * cases where there might be a race with the previous use of newpage.
1045 * This is much like races on refcount of oldpage: just don't BUG().
1047 if (unlikely(!trylock_page(newpage)))
1050 if (unlikely(!is_lru)) {
1051 rc = move_to_new_page(newpage, page, mode);
1052 goto out_unlock_both;
1056 * Corner case handling:
1057 * 1. When a new swap-cache page is read into, it is added to the LRU
1058 * and treated as swapcache but it has no rmap yet.
1059 * Calling try_to_unmap() against a page->mapping==NULL page will
1060 * trigger a BUG. So handle it here.
1061 * 2. An orphaned page (see truncate_complete_page) might have
1062 * fs-private metadata. The page can be picked up due to memory
1063 * offlining. Everywhere else except page reclaim, the page is
1064 * invisible to the vm, so the page can not be migrated. So try to
1065 * free the metadata, so the page can be freed.
1067 if (!page->mapping) {
1068 VM_BUG_ON_PAGE(PageAnon(page), page);
1069 if (page_has_private(page)) {
1070 try_to_free_buffers(page);
1071 goto out_unlock_both;
1073 } else if (page_mapped(page)) {
1074 /* Establish migration ptes */
1075 VM_BUG_ON_PAGE(PageAnon(page) && !PageKsm(page) && !anon_vma,
1078 TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
1079 page_was_mapped = 1;
1082 if (!page_mapped(page))
1083 rc = move_to_new_page(newpage, page, mode);
1085 if (page_was_mapped)
1086 remove_migration_ptes(page,
1087 rc == MIGRATEPAGE_SUCCESS ? newpage : page, false);
1090 unlock_page(newpage);
1092 /* Drop an anon_vma reference if we took one */
1094 put_anon_vma(anon_vma);
1098 * If migration is successful, decrease refcount of the newpage
1099 * which will not free the page because new page owner increased
1100 * refcounter. As well, if it is LRU page, add the page to LRU
1103 if (rc == MIGRATEPAGE_SUCCESS) {
1104 if (unlikely(__PageMovable(newpage)))
1107 putback_lru_page(newpage);
1114 * gcc 4.7 and 4.8 on arm get an ICEs when inlining unmap_and_move(). Work
1117 #if defined(CONFIG_ARM) && \
1118 defined(GCC_VERSION) && GCC_VERSION < 40900 && GCC_VERSION >= 40700
1119 #define ICE_noinline noinline
1121 #define ICE_noinline
1125 * Obtain the lock on page, remove all ptes and migrate the page
1126 * to the newly allocated page in newpage.
1128 static ICE_noinline int unmap_and_move(new_page_t get_new_page,
1129 free_page_t put_new_page,
1130 unsigned long private, struct page *page,
1131 int force, enum migrate_mode mode,
1132 enum migrate_reason reason)
1134 int rc = MIGRATEPAGE_SUCCESS;
1135 struct page *newpage;
1137 if (!thp_migration_supported() && PageTransHuge(page))
1140 newpage = get_new_page(page, private);
1144 if (page_count(page) == 1) {
1145 /* page was freed from under us. So we are done. */
1146 ClearPageActive(page);
1147 ClearPageUnevictable(page);
1148 if (unlikely(__PageMovable(page))) {
1150 if (!PageMovable(page))
1151 __ClearPageIsolated(page);
1155 put_new_page(newpage, private);
1161 rc = __unmap_and_move(page, newpage, force, mode);
1162 if (rc == MIGRATEPAGE_SUCCESS)
1163 set_page_owner_migrate_reason(newpage, reason);
1166 if (rc != -EAGAIN) {
1168 * A page that has been migrated has all references
1169 * removed and will be freed. A page that has not been
1170 * migrated will have kepts its references and be
1173 list_del(&page->lru);
1176 * Compaction can migrate also non-LRU pages which are
1177 * not accounted to NR_ISOLATED_*. They can be recognized
1180 if (likely(!__PageMovable(page)))
1181 mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON +
1182 page_is_file_cache(page), -hpage_nr_pages(page));
1186 * If migration is successful, releases reference grabbed during
1187 * isolation. Otherwise, restore the page to right list unless
1190 if (rc == MIGRATEPAGE_SUCCESS) {
1192 if (reason == MR_MEMORY_FAILURE) {
1194 * Set PG_HWPoison on just freed page
1195 * intentionally. Although it's rather weird,
1196 * it's how HWPoison flag works at the moment.
1198 if (set_hwpoison_free_buddy_page(page))
1199 num_poisoned_pages_inc();
1202 if (rc != -EAGAIN) {
1203 if (likely(!__PageMovable(page))) {
1204 putback_lru_page(page);
1209 if (PageMovable(page))
1210 putback_movable_page(page);
1212 __ClearPageIsolated(page);
1218 put_new_page(newpage, private);
1227 * Counterpart of unmap_and_move_page() for hugepage migration.
1229 * This function doesn't wait the completion of hugepage I/O
1230 * because there is no race between I/O and migration for hugepage.
1231 * Note that currently hugepage I/O occurs only in direct I/O
1232 * where no lock is held and PG_writeback is irrelevant,
1233 * and writeback status of all subpages are counted in the reference
1234 * count of the head page (i.e. if all subpages of a 2MB hugepage are
1235 * under direct I/O, the reference of the head page is 512 and a bit more.)
1236 * This means that when we try to migrate hugepage whose subpages are
1237 * doing direct I/O, some references remain after try_to_unmap() and
1238 * hugepage migration fails without data corruption.
1240 * There is also no race when direct I/O is issued on the page under migration,
1241 * because then pte is replaced with migration swap entry and direct I/O code
1242 * will wait in the page fault for migration to complete.
1244 static int unmap_and_move_huge_page(new_page_t get_new_page,
1245 free_page_t put_new_page, unsigned long private,
1246 struct page *hpage, int force,
1247 enum migrate_mode mode, int reason)
1250 int page_was_mapped = 0;
1251 struct page *new_hpage;
1252 struct anon_vma *anon_vma = NULL;
1255 * Movability of hugepages depends on architectures and hugepage size.
1256 * This check is necessary because some callers of hugepage migration
1257 * like soft offline and memory hotremove don't walk through page
1258 * tables or check whether the hugepage is pmd-based or not before
1259 * kicking migration.
1261 if (!hugepage_migration_supported(page_hstate(hpage))) {
1262 putback_active_hugepage(hpage);
1266 new_hpage = get_new_page(hpage, private);
1270 if (!trylock_page(hpage)) {
1275 case MIGRATE_SYNC_NO_COPY:
1283 if (PageAnon(hpage))
1284 anon_vma = page_get_anon_vma(hpage);
1286 if (unlikely(!trylock_page(new_hpage)))
1289 if (page_mapped(hpage)) {
1291 TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
1292 page_was_mapped = 1;
1295 if (!page_mapped(hpage))
1296 rc = move_to_new_page(new_hpage, hpage, mode);
1298 if (page_was_mapped)
1299 remove_migration_ptes(hpage,
1300 rc == MIGRATEPAGE_SUCCESS ? new_hpage : hpage, false);
1302 unlock_page(new_hpage);
1306 put_anon_vma(anon_vma);
1308 if (rc == MIGRATEPAGE_SUCCESS) {
1309 move_hugetlb_state(hpage, new_hpage, reason);
1310 put_new_page = NULL;
1316 putback_active_hugepage(hpage);
1319 * If migration was not successful and there's a freeing callback, use
1320 * it. Otherwise, put_page() will drop the reference grabbed during
1324 put_new_page(new_hpage, private);
1326 putback_active_hugepage(new_hpage);
1332 * migrate_pages - migrate the pages specified in a list, to the free pages
1333 * supplied as the target for the page migration
1335 * @from: The list of pages to be migrated.
1336 * @get_new_page: The function used to allocate free pages to be used
1337 * as the target of the page migration.
1338 * @put_new_page: The function used to free target pages if migration
1339 * fails, or NULL if no special handling is necessary.
1340 * @private: Private data to be passed on to get_new_page()
1341 * @mode: The migration mode that specifies the constraints for
1342 * page migration, if any.
1343 * @reason: The reason for page migration.
1345 * The function returns after 10 attempts or if no pages are movable any more
1346 * because the list has become empty or no retryable pages exist any more.
1347 * The caller should call putback_movable_pages() to return pages to the LRU
1348 * or free list only if ret != 0.
1350 * Returns the number of pages that were not migrated, or an error code.
1352 int migrate_pages(struct list_head *from, new_page_t get_new_page,
1353 free_page_t put_new_page, unsigned long private,
1354 enum migrate_mode mode, int reason)
1358 int nr_succeeded = 0;
1362 int swapwrite = current->flags & PF_SWAPWRITE;
1366 current->flags |= PF_SWAPWRITE;
1368 for(pass = 0; pass < 10 && retry; pass++) {
1371 list_for_each_entry_safe(page, page2, from, lru) {
1376 rc = unmap_and_move_huge_page(get_new_page,
1377 put_new_page, private, page,
1378 pass > 2, mode, reason);
1380 rc = unmap_and_move(get_new_page, put_new_page,
1381 private, page, pass > 2, mode,
1387 * THP migration might be unsupported or the
1388 * allocation could've failed so we should
1389 * retry on the same page with the THP split
1392 * Head page is retried immediately and tail
1393 * pages are added to the tail of the list so
1394 * we encounter them after the rest of the list
1397 if (PageTransHuge(page) && !PageHuge(page)) {
1399 rc = split_huge_page_to_list(page, from);
1402 list_safe_reset_next(page, page2, lru);
1411 case MIGRATEPAGE_SUCCESS:
1416 * Permanent failure (-EBUSY, -ENOSYS, etc.):
1417 * unlike -EAGAIN case, the failed page is
1418 * removed from migration page list and not
1419 * retried in the next outer loop.
1430 count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded);
1432 count_vm_events(PGMIGRATE_FAIL, nr_failed);
1433 trace_mm_migrate_pages(nr_succeeded, nr_failed, mode, reason);
1436 current->flags &= ~PF_SWAPWRITE;
1443 static int store_status(int __user *status, int start, int value, int nr)
1446 if (put_user(value, status + start))
1454 static int do_move_pages_to_node(struct mm_struct *mm,
1455 struct list_head *pagelist, int node)
1459 if (list_empty(pagelist))
1462 err = migrate_pages(pagelist, alloc_new_node_page, NULL, node,
1463 MIGRATE_SYNC, MR_SYSCALL);
1465 putback_movable_pages(pagelist);
1470 * Resolves the given address to a struct page, isolates it from the LRU and
1471 * puts it to the given pagelist.
1472 * Returns -errno if the page cannot be found/isolated or 0 when it has been
1473 * queued or the page doesn't need to be migrated because it is already on
1476 static int add_page_for_migration(struct mm_struct *mm, unsigned long addr,
1477 int node, struct list_head *pagelist, bool migrate_all)
1479 struct vm_area_struct *vma;
1481 unsigned int follflags;
1484 down_read(&mm->mmap_sem);
1486 vma = find_vma(mm, addr);
1487 if (!vma || addr < vma->vm_start || !vma_migratable(vma))
1490 /* FOLL_DUMP to ignore special (like zero) pages */
1491 follflags = FOLL_GET | FOLL_DUMP;
1492 page = follow_page(vma, addr, follflags);
1494 err = PTR_ERR(page);
1503 if (page_to_nid(page) == node)
1507 if (page_mapcount(page) > 1 && !migrate_all)
1510 if (PageHuge(page)) {
1511 if (PageHead(page)) {
1512 isolate_huge_page(page, pagelist);
1518 head = compound_head(page);
1519 err = isolate_lru_page(head);
1524 list_add_tail(&head->lru, pagelist);
1525 mod_node_page_state(page_pgdat(head),
1526 NR_ISOLATED_ANON + page_is_file_cache(head),
1527 hpage_nr_pages(head));
1531 * Either remove the duplicate refcount from
1532 * isolate_lru_page() or drop the page ref if it was
1537 up_read(&mm->mmap_sem);
1542 * Migrate an array of page address onto an array of nodes and fill
1543 * the corresponding array of status.
1545 static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
1546 unsigned long nr_pages,
1547 const void __user * __user *pages,
1548 const int __user *nodes,
1549 int __user *status, int flags)
1551 int current_node = NUMA_NO_NODE;
1552 LIST_HEAD(pagelist);
1558 for (i = start = 0; i < nr_pages; i++) {
1559 const void __user *p;
1564 if (get_user(p, pages + i))
1566 if (get_user(node, nodes + i))
1568 addr = (unsigned long)p;
1571 if (node < 0 || node >= MAX_NUMNODES)
1573 if (!node_state(node, N_MEMORY))
1577 if (!node_isset(node, task_nodes))
1580 if (current_node == NUMA_NO_NODE) {
1581 current_node = node;
1583 } else if (node != current_node) {
1584 err = do_move_pages_to_node(mm, &pagelist, current_node);
1587 err = store_status(status, start, current_node, i - start);
1591 current_node = node;
1595 * Errors in the page lookup or isolation are not fatal and we simply
1596 * report them via status
1598 err = add_page_for_migration(mm, addr, current_node,
1599 &pagelist, flags & MPOL_MF_MOVE_ALL);
1603 err = store_status(status, i, err, 1);
1607 err = do_move_pages_to_node(mm, &pagelist, current_node);
1611 err = store_status(status, start, current_node, i - start);
1615 current_node = NUMA_NO_NODE;
1618 if (list_empty(&pagelist))
1621 /* Make sure we do not overwrite the existing error */
1622 err1 = do_move_pages_to_node(mm, &pagelist, current_node);
1624 err1 = store_status(status, start, current_node, i - start);
1632 * Determine the nodes of an array of pages and store it in an array of status.
1634 static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
1635 const void __user **pages, int *status)
1639 down_read(&mm->mmap_sem);
1641 for (i = 0; i < nr_pages; i++) {
1642 unsigned long addr = (unsigned long)(*pages);
1643 struct vm_area_struct *vma;
1647 vma = find_vma(mm, addr);
1648 if (!vma || addr < vma->vm_start)
1651 /* FOLL_DUMP to ignore special (like zero) pages */
1652 page = follow_page(vma, addr, FOLL_DUMP);
1654 err = PTR_ERR(page);
1658 err = page ? page_to_nid(page) : -ENOENT;
1666 up_read(&mm->mmap_sem);
1670 * Determine the nodes of a user array of pages and store it in
1671 * a user array of status.
1673 static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
1674 const void __user * __user *pages,
1677 #define DO_PAGES_STAT_CHUNK_NR 16
1678 const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR];
1679 int chunk_status[DO_PAGES_STAT_CHUNK_NR];
1682 unsigned long chunk_nr;
1684 chunk_nr = nr_pages;
1685 if (chunk_nr > DO_PAGES_STAT_CHUNK_NR)
1686 chunk_nr = DO_PAGES_STAT_CHUNK_NR;
1688 if (copy_from_user(chunk_pages, pages, chunk_nr * sizeof(*chunk_pages)))
1691 do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status);
1693 if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status)))
1698 nr_pages -= chunk_nr;
1700 return nr_pages ? -EFAULT : 0;
1704 * Move a list of pages in the address space of the currently executing
1707 static int kernel_move_pages(pid_t pid, unsigned long nr_pages,
1708 const void __user * __user *pages,
1709 const int __user *nodes,
1710 int __user *status, int flags)
1712 struct task_struct *task;
1713 struct mm_struct *mm;
1715 nodemask_t task_nodes;
1718 if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL))
1721 if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
1724 /* Find the mm_struct */
1726 task = pid ? find_task_by_vpid(pid) : current;
1731 get_task_struct(task);
1734 * Check if this process has the right to modify the specified
1735 * process. Use the regular "ptrace_may_access()" checks.
1737 if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) {
1744 err = security_task_movememory(task);
1748 task_nodes = cpuset_mems_allowed(task);
1749 mm = get_task_mm(task);
1750 put_task_struct(task);
1756 err = do_pages_move(mm, task_nodes, nr_pages, pages,
1757 nodes, status, flags);
1759 err = do_pages_stat(mm, nr_pages, pages, status);
1765 put_task_struct(task);
1769 SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages,
1770 const void __user * __user *, pages,
1771 const int __user *, nodes,
1772 int __user *, status, int, flags)
1774 return kernel_move_pages(pid, nr_pages, pages, nodes, status, flags);
1777 #ifdef CONFIG_COMPAT
1778 COMPAT_SYSCALL_DEFINE6(move_pages, pid_t, pid, compat_ulong_t, nr_pages,
1779 compat_uptr_t __user *, pages32,
1780 const int __user *, nodes,
1781 int __user *, status,
1784 const void __user * __user *pages;
1787 pages = compat_alloc_user_space(nr_pages * sizeof(void *));
1788 for (i = 0; i < nr_pages; i++) {
1791 if (get_user(p, pages32 + i) ||
1792 put_user(compat_ptr(p), pages + i))
1795 return kernel_move_pages(pid, nr_pages, pages, nodes, status, flags);
1797 #endif /* CONFIG_COMPAT */
1799 #ifdef CONFIG_NUMA_BALANCING
1801 * Returns true if this is a safe migration target node for misplaced NUMA
1802 * pages. Currently it only checks the watermarks which crude
1804 static bool migrate_balanced_pgdat(struct pglist_data *pgdat,
1805 unsigned long nr_migrate_pages)
1809 for (z = pgdat->nr_zones - 1; z >= 0; z--) {
1810 struct zone *zone = pgdat->node_zones + z;
1812 if (!populated_zone(zone))
1815 /* Avoid waking kswapd by allocating pages_to_migrate pages. */
1816 if (!zone_watermark_ok(zone, 0,
1817 high_wmark_pages(zone) +
1826 static struct page *alloc_misplaced_dst_page(struct page *page,
1829 int nid = (int) data;
1830 struct page *newpage;
1832 newpage = __alloc_pages_node(nid,
1833 (GFP_HIGHUSER_MOVABLE |
1834 __GFP_THISNODE | __GFP_NOMEMALLOC |
1835 __GFP_NORETRY | __GFP_NOWARN) &
1841 static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
1845 VM_BUG_ON_PAGE(compound_order(page) && !PageTransHuge(page), page);
1847 /* Avoid migrating to a node that is nearly full */
1848 if (!migrate_balanced_pgdat(pgdat, 1UL << compound_order(page)))
1851 if (isolate_lru_page(page))
1855 * migrate_misplaced_transhuge_page() skips page migration's usual
1856 * check on page_count(), so we must do it here, now that the page
1857 * has been isolated: a GUP pin, or any other pin, prevents migration.
1858 * The expected page count is 3: 1 for page's mapcount and 1 for the
1859 * caller's pin and 1 for the reference taken by isolate_lru_page().
1861 if (PageTransHuge(page) && page_count(page) != 3) {
1862 putback_lru_page(page);
1866 page_lru = page_is_file_cache(page);
1867 mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + page_lru,
1868 hpage_nr_pages(page));
1871 * Isolating the page has taken another reference, so the
1872 * caller's reference can be safely dropped without the page
1873 * disappearing underneath us during migration.
1879 bool pmd_trans_migrating(pmd_t pmd)
1881 struct page *page = pmd_page(pmd);
1882 return PageLocked(page);
1886 * Attempt to migrate a misplaced page to the specified destination
1887 * node. Caller is expected to have an elevated reference count on
1888 * the page that will be dropped by this function before returning.
1890 int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
1893 pg_data_t *pgdat = NODE_DATA(node);
1896 LIST_HEAD(migratepages);
1899 * Don't migrate file pages that are mapped in multiple processes
1900 * with execute permissions as they are probably shared libraries.
1902 if (page_mapcount(page) != 1 && page_is_file_cache(page) &&
1903 (vma->vm_flags & VM_EXEC))
1907 * Also do not migrate dirty pages as not all filesystems can move
1908 * dirty pages in MIGRATE_ASYNC mode which is a waste of cycles.
1910 if (page_is_file_cache(page) && PageDirty(page))
1913 isolated = numamigrate_isolate_page(pgdat, page);
1917 list_add(&page->lru, &migratepages);
1918 nr_remaining = migrate_pages(&migratepages, alloc_misplaced_dst_page,
1919 NULL, node, MIGRATE_ASYNC,
1922 if (!list_empty(&migratepages)) {
1923 list_del(&page->lru);
1924 dec_node_page_state(page, NR_ISOLATED_ANON +
1925 page_is_file_cache(page));
1926 putback_lru_page(page);
1930 count_vm_numa_event(NUMA_PAGE_MIGRATE);
1931 BUG_ON(!list_empty(&migratepages));
1938 #endif /* CONFIG_NUMA_BALANCING */
1940 #if defined(CONFIG_NUMA_BALANCING) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
1942 * Migrates a THP to a given target node. page must be locked and is unlocked
1945 int migrate_misplaced_transhuge_page(struct mm_struct *mm,
1946 struct vm_area_struct *vma,
1947 pmd_t *pmd, pmd_t entry,
1948 unsigned long address,
1949 struct page *page, int node)
1952 pg_data_t *pgdat = NODE_DATA(node);
1954 struct page *new_page = NULL;
1955 int page_lru = page_is_file_cache(page);
1956 unsigned long start = address & HPAGE_PMD_MASK;
1958 new_page = alloc_pages_node(node,
1959 (GFP_TRANSHUGE_LIGHT | __GFP_THISNODE),
1963 prep_transhuge_page(new_page);
1965 isolated = numamigrate_isolate_page(pgdat, page);
1971 /* Prepare a page as a migration target */
1972 __SetPageLocked(new_page);
1973 if (PageSwapBacked(page))
1974 __SetPageSwapBacked(new_page);
1976 /* anon mapping, we can simply copy page->mapping to the new page: */
1977 new_page->mapping = page->mapping;
1978 new_page->index = page->index;
1979 /* flush the cache before copying using the kernel virtual address */
1980 flush_cache_range(vma, start, start + HPAGE_PMD_SIZE);
1981 migrate_page_copy(new_page, page);
1982 WARN_ON(PageLRU(new_page));
1984 /* Recheck the target PMD */
1985 ptl = pmd_lock(mm, pmd);
1986 if (unlikely(!pmd_same(*pmd, entry) || !page_ref_freeze(page, 2))) {
1989 /* Reverse changes made by migrate_page_copy() */
1990 if (TestClearPageActive(new_page))
1991 SetPageActive(page);
1992 if (TestClearPageUnevictable(new_page))
1993 SetPageUnevictable(page);
1995 unlock_page(new_page);
1996 put_page(new_page); /* Free it */
1998 /* Retake the callers reference and putback on LRU */
2000 putback_lru_page(page);
2001 mod_node_page_state(page_pgdat(page),
2002 NR_ISOLATED_ANON + page_lru, -HPAGE_PMD_NR);
2007 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
2008 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
2011 * Overwrite the old entry under pagetable lock and establish
2012 * the new PTE. Any parallel GUP will either observe the old
2013 * page blocking on the page lock, block on the page table
2014 * lock or observe the new page. The SetPageUptodate on the
2015 * new page and page_add_new_anon_rmap guarantee the copy is
2016 * visible before the pagetable update.
2018 page_add_anon_rmap(new_page, vma, start, true);
2020 * At this point the pmd is numa/protnone (i.e. non present) and the TLB
2021 * has already been flushed globally. So no TLB can be currently
2022 * caching this non present pmd mapping. There's no need to clear the
2023 * pmd before doing set_pmd_at(), nor to flush the TLB after
2024 * set_pmd_at(). Clearing the pmd here would introduce a race
2025 * condition against MADV_DONTNEED, because MADV_DONTNEED only holds the
2026 * mmap_sem for reading. If the pmd is set to NULL at any given time,
2027 * MADV_DONTNEED won't wait on the pmd lock and it'll skip clearing this
2030 set_pmd_at(mm, start, pmd, entry);
2031 update_mmu_cache_pmd(vma, address, &entry);
2033 page_ref_unfreeze(page, 2);
2034 mlock_migrate_page(new_page, page);
2035 page_remove_rmap(page, true);
2036 set_page_owner_migrate_reason(new_page, MR_NUMA_MISPLACED);
2040 /* Take an "isolate" reference and put new page on the LRU. */
2042 putback_lru_page(new_page);
2044 unlock_page(new_page);
2046 put_page(page); /* Drop the rmap reference */
2047 put_page(page); /* Drop the LRU isolation reference */
2049 count_vm_events(PGMIGRATE_SUCCESS, HPAGE_PMD_NR);
2050 count_vm_numa_events(NUMA_PAGE_MIGRATE, HPAGE_PMD_NR);
2052 mod_node_page_state(page_pgdat(page),
2053 NR_ISOLATED_ANON + page_lru,
2058 count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR);
2059 ptl = pmd_lock(mm, pmd);
2060 if (pmd_same(*pmd, entry)) {
2061 entry = pmd_modify(entry, vma->vm_page_prot);
2062 set_pmd_at(mm, start, pmd, entry);
2063 update_mmu_cache_pmd(vma, address, &entry);
2072 #endif /* CONFIG_NUMA_BALANCING */
2074 #endif /* CONFIG_NUMA */
2076 #if defined(CONFIG_MIGRATE_VMA_HELPER)
2077 struct migrate_vma {
2078 struct vm_area_struct *vma;
2081 unsigned long cpages;
2082 unsigned long npages;
2083 unsigned long start;
2087 static int migrate_vma_collect_hole(unsigned long start,
2089 struct mm_walk *walk)
2091 struct migrate_vma *migrate = walk->private;
2094 for (addr = start & PAGE_MASK; addr < end; addr += PAGE_SIZE) {
2095 migrate->src[migrate->npages] = MIGRATE_PFN_MIGRATE;
2096 migrate->dst[migrate->npages] = 0;
2104 static int migrate_vma_collect_skip(unsigned long start,
2106 struct mm_walk *walk)
2108 struct migrate_vma *migrate = walk->private;
2111 for (addr = start & PAGE_MASK; addr < end; addr += PAGE_SIZE) {
2112 migrate->dst[migrate->npages] = 0;
2113 migrate->src[migrate->npages++] = 0;
2119 static int migrate_vma_collect_pmd(pmd_t *pmdp,
2120 unsigned long start,
2122 struct mm_walk *walk)
2124 struct migrate_vma *migrate = walk->private;
2125 struct vm_area_struct *vma = walk->vma;
2126 struct mm_struct *mm = vma->vm_mm;
2127 unsigned long addr = start, unmapped = 0;
2132 if (pmd_none(*pmdp))
2133 return migrate_vma_collect_hole(start, end, walk);
2135 if (pmd_trans_huge(*pmdp)) {
2138 ptl = pmd_lock(mm, pmdp);
2139 if (unlikely(!pmd_trans_huge(*pmdp))) {
2144 page = pmd_page(*pmdp);
2145 if (is_huge_zero_page(page)) {
2147 split_huge_pmd(vma, pmdp, addr);
2148 if (pmd_trans_unstable(pmdp))
2149 return migrate_vma_collect_skip(start, end,
2156 if (unlikely(!trylock_page(page)))
2157 return migrate_vma_collect_skip(start, end,
2159 ret = split_huge_page(page);
2163 return migrate_vma_collect_skip(start, end,
2165 if (pmd_none(*pmdp))
2166 return migrate_vma_collect_hole(start, end,
2171 if (unlikely(pmd_bad(*pmdp)))
2172 return migrate_vma_collect_skip(start, end, walk);
2174 ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
2175 arch_enter_lazy_mmu_mode();
2177 for (; addr < end; addr += PAGE_SIZE, ptep++) {
2178 unsigned long mpfn, pfn;
2186 if (pte_none(pte)) {
2187 mpfn = MIGRATE_PFN_MIGRATE;
2193 if (!pte_present(pte)) {
2197 * Only care about unaddressable device page special
2198 * page table entry. Other special swap entries are not
2199 * migratable, and we ignore regular swapped page.
2201 entry = pte_to_swp_entry(pte);
2202 if (!is_device_private_entry(entry))
2205 page = device_private_entry_to_page(entry);
2206 mpfn = migrate_pfn(page_to_pfn(page))|
2207 MIGRATE_PFN_DEVICE | MIGRATE_PFN_MIGRATE;
2208 if (is_write_device_private_entry(entry))
2209 mpfn |= MIGRATE_PFN_WRITE;
2211 if (is_zero_pfn(pfn)) {
2212 mpfn = MIGRATE_PFN_MIGRATE;
2217 page = _vm_normal_page(migrate->vma, addr, pte, true);
2218 mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
2219 mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0;
2222 /* FIXME support THP */
2223 if (!page || !page->mapping || PageTransCompound(page)) {
2227 pfn = page_to_pfn(page);
2230 * By getting a reference on the page we pin it and that blocks
2231 * any kind of migration. Side effect is that it "freezes" the
2234 * We drop this reference after isolating the page from the lru
2235 * for non device page (device page are not on the lru and thus
2236 * can't be dropped from it).
2242 * Optimize for the common case where page is only mapped once
2243 * in one process. If we can lock the page, then we can safely
2244 * set up a special migration page table entry now.
2246 if (trylock_page(page)) {
2249 mpfn |= MIGRATE_PFN_LOCKED;
2250 ptep_get_and_clear(mm, addr, ptep);
2252 /* Setup special migration page table entry */
2253 entry = make_migration_entry(page, mpfn &
2255 swp_pte = swp_entry_to_pte(entry);
2256 if (pte_soft_dirty(pte))
2257 swp_pte = pte_swp_mksoft_dirty(swp_pte);
2258 set_pte_at(mm, addr, ptep, swp_pte);
2261 * This is like regular unmap: we remove the rmap and
2262 * drop page refcount. Page won't be freed, as we took
2263 * a reference just above.
2265 page_remove_rmap(page, false);
2268 if (pte_present(pte))
2273 migrate->dst[migrate->npages] = 0;
2274 migrate->src[migrate->npages++] = mpfn;
2276 arch_leave_lazy_mmu_mode();
2277 pte_unmap_unlock(ptep - 1, ptl);
2279 /* Only flush the TLB if we actually modified any entries */
2281 flush_tlb_range(walk->vma, start, end);
2287 * migrate_vma_collect() - collect pages over a range of virtual addresses
2288 * @migrate: migrate struct containing all migration information
2290 * This will walk the CPU page table. For each virtual address backed by a
2291 * valid page, it updates the src array and takes a reference on the page, in
2292 * order to pin the page until we lock it and unmap it.
2294 static void migrate_vma_collect(struct migrate_vma *migrate)
2296 struct mmu_notifier_range range;
2297 struct mm_walk mm_walk;
2299 mm_walk.pmd_entry = migrate_vma_collect_pmd;
2300 mm_walk.pte_entry = NULL;
2301 mm_walk.pte_hole = migrate_vma_collect_hole;
2302 mm_walk.hugetlb_entry = NULL;
2303 mm_walk.test_walk = NULL;
2304 mm_walk.vma = migrate->vma;
2305 mm_walk.mm = migrate->vma->vm_mm;
2306 mm_walk.private = migrate;
2308 mmu_notifier_range_init(&range, mm_walk.mm, migrate->start,
2310 mmu_notifier_invalidate_range_start(&range);
2311 walk_page_range(migrate->start, migrate->end, &mm_walk);
2312 mmu_notifier_invalidate_range_end(&range);
2314 migrate->end = migrate->start + (migrate->npages << PAGE_SHIFT);
2318 * migrate_vma_check_page() - check if page is pinned or not
2319 * @page: struct page to check
2321 * Pinned pages cannot be migrated. This is the same test as in
2322 * migrate_page_move_mapping(), except that here we allow migration of a
2325 static bool migrate_vma_check_page(struct page *page)
2328 * One extra ref because caller holds an extra reference, either from
2329 * isolate_lru_page() for a regular page, or migrate_vma_collect() for
2335 * FIXME support THP (transparent huge page), it is bit more complex to
2336 * check them than regular pages, because they can be mapped with a pmd
2337 * or with a pte (split pte mapping).
2339 if (PageCompound(page))
2342 /* Page from ZONE_DEVICE have one extra reference */
2343 if (is_zone_device_page(page)) {
2345 * Private page can never be pin as they have no valid pte and
2346 * GUP will fail for those. Yet if there is a pending migration
2347 * a thread might try to wait on the pte migration entry and
2348 * will bump the page reference count. Sadly there is no way to
2349 * differentiate a regular pin from migration wait. Hence to
2350 * avoid 2 racing thread trying to migrate back to CPU to enter
2351 * infinite loop (one stoping migration because the other is
2352 * waiting on pte migration entry). We always return true here.
2354 * FIXME proper solution is to rework migration_entry_wait() so
2355 * it does not need to take a reference on page.
2357 if (is_device_private_page(page))
2361 * Only allow device public page to be migrated and account for
2362 * the extra reference count imply by ZONE_DEVICE pages.
2364 if (!is_device_public_page(page))
2369 /* For file back page */
2370 if (page_mapping(page))
2371 extra += 1 + page_has_private(page);
2373 if ((page_count(page) - extra) > page_mapcount(page))
2380 * migrate_vma_prepare() - lock pages and isolate them from the lru
2381 * @migrate: migrate struct containing all migration information
2383 * This locks pages that have been collected by migrate_vma_collect(). Once each
2384 * page is locked it is isolated from the lru (for non-device pages). Finally,
2385 * the ref taken by migrate_vma_collect() is dropped, as locked pages cannot be
2386 * migrated by concurrent kernel threads.
2388 static void migrate_vma_prepare(struct migrate_vma *migrate)
2390 const unsigned long npages = migrate->npages;
2391 const unsigned long start = migrate->start;
2392 unsigned long addr, i, restore = 0;
2393 bool allow_drain = true;
2397 for (i = 0; (i < npages) && migrate->cpages; i++) {
2398 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2404 if (!(migrate->src[i] & MIGRATE_PFN_LOCKED)) {
2406 * Because we are migrating several pages there can be
2407 * a deadlock between 2 concurrent migration where each
2408 * are waiting on each other page lock.
2410 * Make migrate_vma() a best effort thing and backoff
2411 * for any page we can not lock right away.
2413 if (!trylock_page(page)) {
2414 migrate->src[i] = 0;
2420 migrate->src[i] |= MIGRATE_PFN_LOCKED;
2423 /* ZONE_DEVICE pages are not on LRU */
2424 if (!is_zone_device_page(page)) {
2425 if (!PageLRU(page) && allow_drain) {
2426 /* Drain CPU's pagevec */
2427 lru_add_drain_all();
2428 allow_drain = false;
2431 if (isolate_lru_page(page)) {
2433 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2437 migrate->src[i] = 0;
2445 /* Drop the reference we took in collect */
2449 if (!migrate_vma_check_page(page)) {
2451 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2455 if (!is_zone_device_page(page)) {
2457 putback_lru_page(page);
2460 migrate->src[i] = 0;
2464 if (!is_zone_device_page(page))
2465 putback_lru_page(page);
2472 for (i = 0, addr = start; i < npages && restore; i++, addr += PAGE_SIZE) {
2473 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2475 if (!page || (migrate->src[i] & MIGRATE_PFN_MIGRATE))
2478 remove_migration_pte(page, migrate->vma, addr, page);
2480 migrate->src[i] = 0;
2488 * migrate_vma_unmap() - replace page mapping with special migration pte entry
2489 * @migrate: migrate struct containing all migration information
2491 * Replace page mapping (CPU page table pte) with a special migration pte entry
2492 * and check again if it has been pinned. Pinned pages are restored because we
2493 * cannot migrate them.
2495 * This is the last step before we call the device driver callback to allocate
2496 * destination memory and copy contents of original page over to new page.
2498 static void migrate_vma_unmap(struct migrate_vma *migrate)
2500 int flags = TTU_MIGRATION | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
2501 const unsigned long npages = migrate->npages;
2502 const unsigned long start = migrate->start;
2503 unsigned long addr, i, restore = 0;
2505 for (i = 0; i < npages; i++) {
2506 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2508 if (!page || !(migrate->src[i] & MIGRATE_PFN_MIGRATE))
2511 if (page_mapped(page)) {
2512 try_to_unmap(page, flags);
2513 if (page_mapped(page))
2517 if (migrate_vma_check_page(page))
2521 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2526 for (addr = start, i = 0; i < npages && restore; addr += PAGE_SIZE, i++) {
2527 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2529 if (!page || (migrate->src[i] & MIGRATE_PFN_MIGRATE))
2532 remove_migration_ptes(page, page, false);
2534 migrate->src[i] = 0;
2538 if (is_zone_device_page(page))
2541 putback_lru_page(page);
2545 static void migrate_vma_insert_page(struct migrate_vma *migrate,
2551 struct vm_area_struct *vma = migrate->vma;
2552 struct mm_struct *mm = vma->vm_mm;
2553 struct mem_cgroup *memcg;
2563 /* Only allow populating anonymous memory */
2564 if (!vma_is_anonymous(vma))
2567 pgdp = pgd_offset(mm, addr);
2568 p4dp = p4d_alloc(mm, pgdp, addr);
2571 pudp = pud_alloc(mm, p4dp, addr);
2574 pmdp = pmd_alloc(mm, pudp, addr);
2578 if (pmd_trans_huge(*pmdp) || pmd_devmap(*pmdp))
2582 * Use pte_alloc() instead of pte_alloc_map(). We can't run
2583 * pte_offset_map() on pmds where a huge pmd might be created
2584 * from a different thread.
2586 * pte_alloc_map() is safe to use under down_write(mmap_sem) or when
2587 * parallel threads are excluded by other means.
2589 * Here we only have down_read(mmap_sem).
2591 if (pte_alloc(mm, pmdp, addr))
2594 /* See the comment in pte_alloc_one_map() */
2595 if (unlikely(pmd_trans_unstable(pmdp)))
2598 if (unlikely(anon_vma_prepare(vma)))
2600 if (mem_cgroup_try_charge(page, vma->vm_mm, GFP_KERNEL, &memcg, false))
2604 * The memory barrier inside __SetPageUptodate makes sure that
2605 * preceding stores to the page contents become visible before
2606 * the set_pte_at() write.
2608 __SetPageUptodate(page);
2610 if (is_zone_device_page(page)) {
2611 if (is_device_private_page(page)) {
2612 swp_entry_t swp_entry;
2614 swp_entry = make_device_private_entry(page, vma->vm_flags & VM_WRITE);
2615 entry = swp_entry_to_pte(swp_entry);
2616 } else if (is_device_public_page(page)) {
2617 entry = pte_mkold(mk_pte(page, READ_ONCE(vma->vm_page_prot)));
2618 if (vma->vm_flags & VM_WRITE)
2619 entry = pte_mkwrite(pte_mkdirty(entry));
2620 entry = pte_mkdevmap(entry);
2623 entry = mk_pte(page, vma->vm_page_prot);
2624 if (vma->vm_flags & VM_WRITE)
2625 entry = pte_mkwrite(pte_mkdirty(entry));
2628 ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
2630 if (pte_present(*ptep)) {
2631 unsigned long pfn = pte_pfn(*ptep);
2633 if (!is_zero_pfn(pfn)) {
2634 pte_unmap_unlock(ptep, ptl);
2635 mem_cgroup_cancel_charge(page, memcg, false);
2639 } else if (!pte_none(*ptep)) {
2640 pte_unmap_unlock(ptep, ptl);
2641 mem_cgroup_cancel_charge(page, memcg, false);
2646 * Check for usefaultfd but do not deliver the fault. Instead,
2649 if (userfaultfd_missing(vma)) {
2650 pte_unmap_unlock(ptep, ptl);
2651 mem_cgroup_cancel_charge(page, memcg, false);
2655 inc_mm_counter(mm, MM_ANONPAGES);
2656 page_add_new_anon_rmap(page, vma, addr, false);
2657 mem_cgroup_commit_charge(page, memcg, false, false);
2658 if (!is_zone_device_page(page))
2659 lru_cache_add_active_or_unevictable(page, vma);
2663 flush_cache_page(vma, addr, pte_pfn(*ptep));
2664 ptep_clear_flush_notify(vma, addr, ptep);
2665 set_pte_at_notify(mm, addr, ptep, entry);
2666 update_mmu_cache(vma, addr, ptep);
2668 /* No need to invalidate - it was non-present before */
2669 set_pte_at(mm, addr, ptep, entry);
2670 update_mmu_cache(vma, addr, ptep);
2673 pte_unmap_unlock(ptep, ptl);
2674 *src = MIGRATE_PFN_MIGRATE;
2678 *src &= ~MIGRATE_PFN_MIGRATE;
2682 * migrate_vma_pages() - migrate meta-data from src page to dst page
2683 * @migrate: migrate struct containing all migration information
2685 * This migrates struct page meta-data from source struct page to destination
2686 * struct page. This effectively finishes the migration from source page to the
2689 static void migrate_vma_pages(struct migrate_vma *migrate)
2691 const unsigned long npages = migrate->npages;
2692 const unsigned long start = migrate->start;
2693 struct mmu_notifier_range range;
2694 unsigned long addr, i;
2695 bool notified = false;
2697 for (i = 0, addr = start; i < npages; addr += PAGE_SIZE, i++) {
2698 struct page *newpage = migrate_pfn_to_page(migrate->dst[i]);
2699 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2700 struct address_space *mapping;
2704 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2709 if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE)) {
2715 mmu_notifier_range_init(&range,
2716 migrate->vma->vm_mm,
2717 addr, migrate->end);
2718 mmu_notifier_invalidate_range_start(&range);
2720 migrate_vma_insert_page(migrate, addr, newpage,
2726 mapping = page_mapping(page);
2728 if (is_zone_device_page(newpage)) {
2729 if (is_device_private_page(newpage)) {
2731 * For now only support private anonymous when
2732 * migrating to un-addressable device memory.
2735 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2738 } else if (!is_device_public_page(newpage)) {
2740 * Other types of ZONE_DEVICE page are not
2743 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2748 r = migrate_page(mapping, newpage, page, MIGRATE_SYNC_NO_COPY);
2749 if (r != MIGRATEPAGE_SUCCESS)
2750 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2754 * No need to double call mmu_notifier->invalidate_range() callback as
2755 * the above ptep_clear_flush_notify() inside migrate_vma_insert_page()
2756 * did already call it.
2759 mmu_notifier_invalidate_range_only_end(&range);
2763 * migrate_vma_finalize() - restore CPU page table entry
2764 * @migrate: migrate struct containing all migration information
2766 * This replaces the special migration pte entry with either a mapping to the
2767 * new page if migration was successful for that page, or to the original page
2770 * This also unlocks the pages and puts them back on the lru, or drops the extra
2771 * refcount, for device pages.
2773 static void migrate_vma_finalize(struct migrate_vma *migrate)
2775 const unsigned long npages = migrate->npages;
2778 for (i = 0; i < npages; i++) {
2779 struct page *newpage = migrate_pfn_to_page(migrate->dst[i]);
2780 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2784 unlock_page(newpage);
2790 if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE) || !newpage) {
2792 unlock_page(newpage);
2798 remove_migration_ptes(page, newpage, false);
2802 if (is_zone_device_page(page))
2805 putback_lru_page(page);
2807 if (newpage != page) {
2808 unlock_page(newpage);
2809 if (is_zone_device_page(newpage))
2812 putback_lru_page(newpage);
2818 * migrate_vma() - migrate a range of memory inside vma
2820 * @ops: migration callback for allocating destination memory and copying
2821 * @vma: virtual memory area containing the range to be migrated
2822 * @start: start address of the range to migrate (inclusive)
2823 * @end: end address of the range to migrate (exclusive)
2824 * @src: array of hmm_pfn_t containing source pfns
2825 * @dst: array of hmm_pfn_t containing destination pfns
2826 * @private: pointer passed back to each of the callback
2827 * Returns: 0 on success, error code otherwise
2829 * This function tries to migrate a range of memory virtual address range, using
2830 * callbacks to allocate and copy memory from source to destination. First it
2831 * collects all the pages backing each virtual address in the range, saving this
2832 * inside the src array. Then it locks those pages and unmaps them. Once the pages
2833 * are locked and unmapped, it checks whether each page is pinned or not. Pages
2834 * that aren't pinned have the MIGRATE_PFN_MIGRATE flag set (by this function)
2835 * in the corresponding src array entry. It then restores any pages that are
2836 * pinned, by remapping and unlocking those pages.
2838 * At this point it calls the alloc_and_copy() callback. For documentation on
2839 * what is expected from that callback, see struct migrate_vma_ops comments in
2840 * include/linux/migrate.h
2842 * After the alloc_and_copy() callback, this function goes over each entry in
2843 * the src array that has the MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag
2844 * set. If the corresponding entry in dst array has MIGRATE_PFN_VALID flag set,
2845 * then the function tries to migrate struct page information from the source
2846 * struct page to the destination struct page. If it fails to migrate the struct
2847 * page information, then it clears the MIGRATE_PFN_MIGRATE flag in the src
2850 * At this point all successfully migrated pages have an entry in the src
2851 * array with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag set and the dst
2852 * array entry with MIGRATE_PFN_VALID flag set.
2854 * It then calls the finalize_and_map() callback. See comments for "struct
2855 * migrate_vma_ops", in include/linux/migrate.h for details about
2856 * finalize_and_map() behavior.
2858 * After the finalize_and_map() callback, for successfully migrated pages, this
2859 * function updates the CPU page table to point to new pages, otherwise it
2860 * restores the CPU page table to point to the original source pages.
2862 * Function returns 0 after the above steps, even if no pages were migrated
2863 * (The function only returns an error if any of the arguments are invalid.)
2865 * Both src and dst array must be big enough for (end - start) >> PAGE_SHIFT
2866 * unsigned long entries.
2868 int migrate_vma(const struct migrate_vma_ops *ops,
2869 struct vm_area_struct *vma,
2870 unsigned long start,
2876 struct migrate_vma migrate;
2878 /* Sanity check the arguments */
2881 if (!vma || is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL) ||
2884 if (start < vma->vm_start || start >= vma->vm_end)
2886 if (end <= vma->vm_start || end > vma->vm_end)
2888 if (!ops || !src || !dst || start >= end)
2891 memset(src, 0, sizeof(*src) * ((end - start) >> PAGE_SHIFT));
2894 migrate.start = start;
2900 /* Collect, and try to unmap source pages */
2901 migrate_vma_collect(&migrate);
2902 if (!migrate.cpages)
2905 /* Lock and isolate page */
2906 migrate_vma_prepare(&migrate);
2907 if (!migrate.cpages)
2911 migrate_vma_unmap(&migrate);
2912 if (!migrate.cpages)
2916 * At this point pages are locked and unmapped, and thus they have
2917 * stable content and can safely be copied to destination memory that
2918 * is allocated by the callback.
2920 * Note that migration can fail in migrate_vma_struct_page() for each
2923 ops->alloc_and_copy(vma, src, dst, start, end, private);
2925 /* This does the real migration of struct page */
2926 migrate_vma_pages(&migrate);
2928 ops->finalize_and_map(vma, src, dst, start, end, private);
2930 /* Unlock and remap pages */
2931 migrate_vma_finalize(&migrate);
2935 EXPORT_SYMBOL(migrate_vma);
2936 #endif /* defined(MIGRATE_VMA_HELPER) */