1 // SPDX-License-Identifier: GPL-2.0
3 * Memory Migration functionality - linux/mm/migrate.c
5 * Copyright (C) 2006 Silicon Graphics, Inc., Christoph Lameter
7 * Page migration was first developed in the context of the memory hotplug
8 * project. The main authors of the migration code are:
10 * IWAMOTO Toshihiro <iwamoto@valinux.co.jp>
11 * Hirokazu Takahashi <taka@valinux.co.jp>
12 * Dave Hansen <haveblue@us.ibm.com>
16 #include <linux/migrate.h>
17 #include <linux/export.h>
18 #include <linux/swap.h>
19 #include <linux/swapops.h>
20 #include <linux/pagemap.h>
21 #include <linux/buffer_head.h>
22 #include <linux/mm_inline.h>
23 #include <linux/nsproxy.h>
24 #include <linux/pagevec.h>
25 #include <linux/ksm.h>
26 #include <linux/rmap.h>
27 #include <linux/topology.h>
28 #include <linux/cpu.h>
29 #include <linux/cpuset.h>
30 #include <linux/writeback.h>
31 #include <linux/mempolicy.h>
32 #include <linux/vmalloc.h>
33 #include <linux/security.h>
34 #include <linux/backing-dev.h>
35 #include <linux/compaction.h>
36 #include <linux/syscalls.h>
37 #include <linux/compat.h>
38 #include <linux/hugetlb.h>
39 #include <linux/hugetlb_cgroup.h>
40 #include <linux/gfp.h>
41 #include <linux/pagewalk.h>
42 #include <linux/pfn_t.h>
43 #include <linux/memremap.h>
44 #include <linux/userfaultfd_k.h>
45 #include <linux/balloon_compaction.h>
46 #include <linux/mmu_notifier.h>
47 #include <linux/page_idle.h>
48 #include <linux/page_owner.h>
49 #include <linux/sched/mm.h>
50 #include <linux/ptrace.h>
51 #include <linux/oom.h>
53 #include <asm/tlbflush.h>
55 #define CREATE_TRACE_POINTS
56 #include <trace/events/migrate.h>
61 * migrate_prep() needs to be called before we start compiling a list of pages
62 * to be migrated using isolate_lru_page(). If scheduling work on other CPUs is
63 * undesirable, use migrate_prep_local()
65 int migrate_prep(void)
68 * Clear the LRU lists so pages can be isolated.
69 * Note that pages may be moved off the LRU after we have
70 * drained them. Those pages will fail to migrate like other
71 * pages that may be busy.
78 /* Do the necessary work of migrate_prep but not if it involves other CPUs */
79 int migrate_prep_local(void)
86 int isolate_movable_page(struct page *page, isolate_mode_t mode)
88 struct address_space *mapping;
91 * Avoid burning cycles with pages that are yet under __free_pages(),
92 * or just got freed under us.
94 * In case we 'win' a race for a movable page being freed under us and
95 * raise its refcount preventing __free_pages() from doing its job
96 * the put_page() at the end of this block will take care of
97 * release this page, thus avoiding a nasty leakage.
99 if (unlikely(!get_page_unless_zero(page)))
103 * Check PageMovable before holding a PG_lock because page's owner
104 * assumes anybody doesn't touch PG_lock of newly allocated page
105 * so unconditionally grabbing the lock ruins page's owner side.
107 if (unlikely(!__PageMovable(page)))
110 * As movable pages are not isolated from LRU lists, concurrent
111 * compaction threads can race against page migration functions
112 * as well as race against the releasing a page.
114 * In order to avoid having an already isolated movable page
115 * being (wrongly) re-isolated while it is under migration,
116 * or to avoid attempting to isolate pages being released,
117 * lets be sure we have the page lock
118 * before proceeding with the movable page isolation steps.
120 if (unlikely(!trylock_page(page)))
123 if (!PageMovable(page) || PageIsolated(page))
124 goto out_no_isolated;
126 mapping = page_mapping(page);
127 VM_BUG_ON_PAGE(!mapping, page);
129 if (!mapping->a_ops->isolate_page(page, mode))
130 goto out_no_isolated;
132 /* Driver shouldn't use PG_isolated bit of page->flags */
133 WARN_ON_ONCE(PageIsolated(page));
134 __SetPageIsolated(page);
147 /* It should be called on page which is PG_movable */
148 void putback_movable_page(struct page *page)
150 struct address_space *mapping;
152 VM_BUG_ON_PAGE(!PageLocked(page), page);
153 VM_BUG_ON_PAGE(!PageMovable(page), page);
154 VM_BUG_ON_PAGE(!PageIsolated(page), page);
156 mapping = page_mapping(page);
157 mapping->a_ops->putback_page(page);
158 __ClearPageIsolated(page);
162 * Put previously isolated pages back onto the appropriate lists
163 * from where they were once taken off for compaction/migration.
165 * This function shall be used whenever the isolated pageset has been
166 * built from lru, balloon, hugetlbfs page. See isolate_migratepages_range()
167 * and isolate_huge_page().
169 void putback_movable_pages(struct list_head *l)
174 list_for_each_entry_safe(page, page2, l, lru) {
175 if (unlikely(PageHuge(page))) {
176 putback_active_hugepage(page);
179 list_del(&page->lru);
181 * We isolated non-lru movable page so here we can use
182 * __PageMovable because LRU page's mapping cannot have
183 * PAGE_MAPPING_MOVABLE.
185 if (unlikely(__PageMovable(page))) {
186 VM_BUG_ON_PAGE(!PageIsolated(page), page);
188 if (PageMovable(page))
189 putback_movable_page(page);
191 __ClearPageIsolated(page);
195 mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON +
196 page_is_file_cache(page), -hpage_nr_pages(page));
197 putback_lru_page(page);
203 * Restore a potential migration pte to a working pte entry
205 static bool remove_migration_pte(struct page *page, struct vm_area_struct *vma,
206 unsigned long addr, void *old)
208 struct page_vma_mapped_walk pvmw = {
212 .flags = PVMW_SYNC | PVMW_MIGRATION,
218 VM_BUG_ON_PAGE(PageTail(page), page);
219 while (page_vma_mapped_walk(&pvmw)) {
223 new = page - pvmw.page->index +
224 linear_page_index(vma, pvmw.address);
226 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
227 /* PMD-mapped THP migration entry */
229 VM_BUG_ON_PAGE(PageHuge(page) || !PageTransCompound(page), page);
230 remove_migration_pmd(&pvmw, new);
236 pte = pte_mkold(mk_pte(new, READ_ONCE(vma->vm_page_prot)));
237 if (pte_swp_soft_dirty(*pvmw.pte))
238 pte = pte_mksoft_dirty(pte);
241 * Recheck VMA as permissions can change since migration started
243 entry = pte_to_swp_entry(*pvmw.pte);
244 if (is_write_migration_entry(entry))
245 pte = maybe_mkwrite(pte, vma);
247 if (unlikely(is_zone_device_page(new))) {
248 if (is_device_private_page(new)) {
249 entry = make_device_private_entry(new, pte_write(pte));
250 pte = swp_entry_to_pte(entry);
254 #ifdef CONFIG_HUGETLB_PAGE
256 pte = pte_mkhuge(pte);
257 pte = arch_make_huge_pte(pte, vma, new, 0);
258 set_huge_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte);
260 hugepage_add_anon_rmap(new, vma, pvmw.address);
262 page_dup_rmap(new, true);
266 set_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte);
269 page_add_anon_rmap(new, vma, pvmw.address, false);
271 page_add_file_rmap(new, false);
273 if (vma->vm_flags & VM_LOCKED && !PageTransCompound(new))
276 if (PageTransHuge(page) && PageMlocked(page))
277 clear_page_mlock(page);
279 /* No need to invalidate - it was non-present before */
280 update_mmu_cache(vma, pvmw.address, pvmw.pte);
287 * Get rid of all migration entries and replace them by
288 * references to the indicated page.
290 void remove_migration_ptes(struct page *old, struct page *new, bool locked)
292 struct rmap_walk_control rwc = {
293 .rmap_one = remove_migration_pte,
298 rmap_walk_locked(new, &rwc);
300 rmap_walk(new, &rwc);
304 * Something used the pte of a page under migration. We need to
305 * get to the page and wait until migration is finished.
306 * When we return from this function the fault will be retried.
308 void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
317 if (!is_swap_pte(pte))
320 entry = pte_to_swp_entry(pte);
321 if (!is_migration_entry(entry))
324 page = migration_entry_to_page(entry);
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)) {
444 SetPageSwapCache(newpage);
445 set_page_private(newpage, page_private(page));
448 VM_BUG_ON_PAGE(PageSwapCache(page), page);
451 /* Move dirty while page refs frozen and newpage not yet exposed */
452 dirty = PageDirty(page);
454 ClearPageDirty(page);
455 SetPageDirty(newpage);
458 xas_store(&xas, newpage);
459 if (PageTransHuge(page)) {
462 for (i = 1; i < HPAGE_PMD_NR; i++) {
464 xas_store(&xas, newpage);
469 * Drop cache reference from old page by unfreezing
470 * to one less reference.
471 * We know this isn't the last reference.
473 page_ref_unfreeze(page, expected_count - hpage_nr_pages(page));
476 /* Leave irq disabled to prevent preemption while updating stats */
479 * If moved to a different zone then also account
480 * the page for that zone. Other VM counters will be
481 * taken care of when we establish references to the
482 * new page and drop references to the old page.
484 * Note that anonymous pages are accounted for
485 * via NR_FILE_PAGES and NR_ANON_MAPPED if they
486 * are mapped to swap space.
488 if (newzone != oldzone) {
489 __dec_node_state(oldzone->zone_pgdat, NR_FILE_PAGES);
490 __inc_node_state(newzone->zone_pgdat, NR_FILE_PAGES);
491 if (PageSwapBacked(page) && !PageSwapCache(page)) {
492 __dec_node_state(oldzone->zone_pgdat, NR_SHMEM);
493 __inc_node_state(newzone->zone_pgdat, NR_SHMEM);
495 if (dirty && mapping_cap_account_dirty(mapping)) {
496 __dec_node_state(oldzone->zone_pgdat, NR_FILE_DIRTY);
497 __dec_zone_state(oldzone, NR_ZONE_WRITE_PENDING);
498 __inc_node_state(newzone->zone_pgdat, NR_FILE_DIRTY);
499 __inc_zone_state(newzone, NR_ZONE_WRITE_PENDING);
504 return MIGRATEPAGE_SUCCESS;
506 EXPORT_SYMBOL(migrate_page_move_mapping);
509 * The expected number of remaining references is the same as that
510 * of migrate_page_move_mapping().
512 int migrate_huge_page_move_mapping(struct address_space *mapping,
513 struct page *newpage, struct page *page)
515 XA_STATE(xas, &mapping->i_pages, page_index(page));
519 expected_count = 2 + page_has_private(page);
520 if (page_count(page) != expected_count || xas_load(&xas) != page) {
521 xas_unlock_irq(&xas);
525 if (!page_ref_freeze(page, expected_count)) {
526 xas_unlock_irq(&xas);
530 newpage->index = page->index;
531 newpage->mapping = page->mapping;
535 xas_store(&xas, newpage);
537 page_ref_unfreeze(page, expected_count - 1);
539 xas_unlock_irq(&xas);
541 return MIGRATEPAGE_SUCCESS;
545 * Gigantic pages are so large that we do not guarantee that page++ pointer
546 * arithmetic will work across the entire page. We need something more
549 static void __copy_gigantic_page(struct page *dst, struct page *src,
553 struct page *dst_base = dst;
554 struct page *src_base = src;
556 for (i = 0; i < nr_pages; ) {
558 copy_highpage(dst, src);
561 dst = mem_map_next(dst, dst_base, i);
562 src = mem_map_next(src, src_base, i);
566 static void copy_huge_page(struct page *dst, struct page *src)
573 struct hstate *h = page_hstate(src);
574 nr_pages = pages_per_huge_page(h);
576 if (unlikely(nr_pages > MAX_ORDER_NR_PAGES)) {
577 __copy_gigantic_page(dst, src, nr_pages);
582 BUG_ON(!PageTransHuge(src));
583 nr_pages = hpage_nr_pages(src);
586 for (i = 0; i < nr_pages; i++) {
588 copy_highpage(dst + i, src + i);
593 * Copy the page to its new location
595 void migrate_page_states(struct page *newpage, struct page *page)
600 SetPageError(newpage);
601 if (PageReferenced(page))
602 SetPageReferenced(newpage);
603 if (PageUptodate(page))
604 SetPageUptodate(newpage);
605 if (TestClearPageActive(page)) {
606 VM_BUG_ON_PAGE(PageUnevictable(page), page);
607 SetPageActive(newpage);
608 } else if (TestClearPageUnevictable(page))
609 SetPageUnevictable(newpage);
610 if (PageWorkingset(page))
611 SetPageWorkingset(newpage);
612 if (PageChecked(page))
613 SetPageChecked(newpage);
614 if (PageMappedToDisk(page))
615 SetPageMappedToDisk(newpage);
617 /* Move dirty on pages not done by migrate_page_move_mapping() */
619 SetPageDirty(newpage);
621 if (page_is_young(page))
622 set_page_young(newpage);
623 if (page_is_idle(page))
624 set_page_idle(newpage);
627 * Copy NUMA information to the new page, to prevent over-eager
628 * future migrations of this same page.
630 cpupid = page_cpupid_xchg_last(page, -1);
631 page_cpupid_xchg_last(newpage, cpupid);
633 ksm_migrate_page(newpage, page);
635 * Please do not reorder this without considering how mm/ksm.c's
636 * get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache().
638 if (PageSwapCache(page))
639 ClearPageSwapCache(page);
640 ClearPagePrivate(page);
641 set_page_private(page, 0);
644 * If any waiters have accumulated on the new page then
647 if (PageWriteback(newpage))
648 end_page_writeback(newpage);
650 copy_page_owner(page, newpage);
652 mem_cgroup_migrate(page, newpage);
654 EXPORT_SYMBOL(migrate_page_states);
656 void migrate_page_copy(struct page *newpage, struct page *page)
658 if (PageHuge(page) || PageTransHuge(page))
659 copy_huge_page(newpage, page);
661 copy_highpage(newpage, page);
663 migrate_page_states(newpage, page);
665 EXPORT_SYMBOL(migrate_page_copy);
667 /************************************************************
668 * Migration functions
669 ***********************************************************/
672 * Common logic to directly migrate a single LRU page suitable for
673 * pages that do not use PagePrivate/PagePrivate2.
675 * Pages are locked upon entry and exit.
677 int migrate_page(struct address_space *mapping,
678 struct page *newpage, struct page *page,
679 enum migrate_mode mode)
683 BUG_ON(PageWriteback(page)); /* Writeback must be complete */
685 rc = migrate_page_move_mapping(mapping, newpage, page, 0);
687 if (rc != MIGRATEPAGE_SUCCESS)
690 if (mode != MIGRATE_SYNC_NO_COPY)
691 migrate_page_copy(newpage, page);
693 migrate_page_states(newpage, page);
694 return MIGRATEPAGE_SUCCESS;
696 EXPORT_SYMBOL(migrate_page);
699 /* Returns true if all buffers are successfully locked */
700 static bool buffer_migrate_lock_buffers(struct buffer_head *head,
701 enum migrate_mode mode)
703 struct buffer_head *bh = head;
705 /* Simple case, sync compaction */
706 if (mode != MIGRATE_ASYNC) {
709 bh = bh->b_this_page;
711 } while (bh != head);
716 /* async case, we cannot block on lock_buffer so use trylock_buffer */
718 if (!trylock_buffer(bh)) {
720 * We failed to lock the buffer and cannot stall in
721 * async migration. Release the taken locks
723 struct buffer_head *failed_bh = bh;
725 while (bh != failed_bh) {
727 bh = bh->b_this_page;
732 bh = bh->b_this_page;
733 } while (bh != head);
737 static int __buffer_migrate_page(struct address_space *mapping,
738 struct page *newpage, struct page *page, enum migrate_mode mode,
741 struct buffer_head *bh, *head;
745 if (!page_has_buffers(page))
746 return migrate_page(mapping, newpage, page, mode);
748 /* Check whether page does not have extra refs before we do more work */
749 expected_count = expected_page_refs(mapping, page);
750 if (page_count(page) != expected_count)
753 head = page_buffers(page);
754 if (!buffer_migrate_lock_buffers(head, mode))
759 bool invalidated = false;
763 spin_lock(&mapping->private_lock);
766 if (atomic_read(&bh->b_count)) {
770 bh = bh->b_this_page;
771 } while (bh != head);
777 spin_unlock(&mapping->private_lock);
778 invalidate_bh_lrus();
780 goto recheck_buffers;
784 rc = migrate_page_move_mapping(mapping, newpage, page, 0);
785 if (rc != MIGRATEPAGE_SUCCESS)
788 ClearPagePrivate(page);
789 set_page_private(newpage, page_private(page));
790 set_page_private(page, 0);
796 set_bh_page(bh, newpage, bh_offset(bh));
797 bh = bh->b_this_page;
799 } while (bh != head);
801 SetPagePrivate(newpage);
803 if (mode != MIGRATE_SYNC_NO_COPY)
804 migrate_page_copy(newpage, page);
806 migrate_page_states(newpage, page);
808 rc = MIGRATEPAGE_SUCCESS;
811 spin_unlock(&mapping->private_lock);
815 bh = bh->b_this_page;
817 } while (bh != head);
823 * Migration function for pages with buffers. This function can only be used
824 * if the underlying filesystem guarantees that no other references to "page"
825 * exist. For example attached buffer heads are accessed only under page lock.
827 int buffer_migrate_page(struct address_space *mapping,
828 struct page *newpage, struct page *page, enum migrate_mode mode)
830 return __buffer_migrate_page(mapping, newpage, page, mode, false);
832 EXPORT_SYMBOL(buffer_migrate_page);
835 * Same as above except that this variant is more careful and checks that there
836 * are also no buffer head references. This function is the right one for
837 * mappings where buffer heads are directly looked up and referenced (such as
838 * block device mappings).
840 int buffer_migrate_page_norefs(struct address_space *mapping,
841 struct page *newpage, struct page *page, enum migrate_mode mode)
843 return __buffer_migrate_page(mapping, newpage, page, mode, true);
848 * Writeback a page to clean the dirty state
850 static int writeout(struct address_space *mapping, struct page *page)
852 struct writeback_control wbc = {
853 .sync_mode = WB_SYNC_NONE,
856 .range_end = LLONG_MAX,
861 if (!mapping->a_ops->writepage)
862 /* No write method for the address space */
865 if (!clear_page_dirty_for_io(page))
866 /* Someone else already triggered a write */
870 * A dirty page may imply that the underlying filesystem has
871 * the page on some queue. So the page must be clean for
872 * migration. Writeout may mean we loose the lock and the
873 * page state is no longer what we checked for earlier.
874 * At this point we know that the migration attempt cannot
877 remove_migration_ptes(page, page, false);
879 rc = mapping->a_ops->writepage(page, &wbc);
881 if (rc != AOP_WRITEPAGE_ACTIVATE)
882 /* unlocked. Relock */
885 return (rc < 0) ? -EIO : -EAGAIN;
889 * Default handling if a filesystem does not provide a migration function.
891 static int fallback_migrate_page(struct address_space *mapping,
892 struct page *newpage, struct page *page, enum migrate_mode mode)
894 if (PageDirty(page)) {
895 /* Only writeback pages in full synchronous migration */
898 case MIGRATE_SYNC_NO_COPY:
903 return writeout(mapping, page);
907 * Buffers may be managed in a filesystem specific way.
908 * We must have no buffers or drop them.
910 if (page_has_private(page) &&
911 !try_to_release_page(page, GFP_KERNEL))
912 return mode == MIGRATE_SYNC ? -EAGAIN : -EBUSY;
914 return migrate_page(mapping, newpage, page, mode);
918 * Move a page to a newly allocated page
919 * The page is locked and all ptes have been successfully removed.
921 * The new page will have replaced the old page if this function
926 * MIGRATEPAGE_SUCCESS - success
928 static int move_to_new_page(struct page *newpage, struct page *page,
929 enum migrate_mode mode)
931 struct address_space *mapping;
933 bool is_lru = !__PageMovable(page);
935 VM_BUG_ON_PAGE(!PageLocked(page), page);
936 VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
938 mapping = page_mapping(page);
940 if (likely(is_lru)) {
942 rc = migrate_page(mapping, newpage, page, mode);
943 else if (mapping->a_ops->migratepage)
945 * Most pages have a mapping and most filesystems
946 * provide a migratepage callback. Anonymous pages
947 * are part of swap space which also has its own
948 * migratepage callback. This is the most common path
949 * for page migration.
951 rc = mapping->a_ops->migratepage(mapping, newpage,
954 rc = fallback_migrate_page(mapping, newpage,
958 * In case of non-lru page, it could be released after
959 * isolation step. In that case, we shouldn't try migration.
961 VM_BUG_ON_PAGE(!PageIsolated(page), page);
962 if (!PageMovable(page)) {
963 rc = MIGRATEPAGE_SUCCESS;
964 __ClearPageIsolated(page);
968 rc = mapping->a_ops->migratepage(mapping, newpage,
970 WARN_ON_ONCE(rc == MIGRATEPAGE_SUCCESS &&
971 !PageIsolated(page));
975 * When successful, old pagecache page->mapping must be cleared before
976 * page is freed; but stats require that PageAnon be left as PageAnon.
978 if (rc == MIGRATEPAGE_SUCCESS) {
979 if (__PageMovable(page)) {
980 VM_BUG_ON_PAGE(!PageIsolated(page), page);
983 * We clear PG_movable under page_lock so any compactor
984 * cannot try to migrate this page.
986 __ClearPageIsolated(page);
990 * Anonymous and movable page->mapping will be cleared by
991 * free_pages_prepare so don't reset it here for keeping
992 * the type to work PageAnon, for example.
994 if (!PageMappingFlags(page))
995 page->mapping = NULL;
997 if (likely(!is_zone_device_page(newpage)))
998 flush_dcache_page(newpage);
1005 static int __unmap_and_move(struct page *page, struct page *newpage,
1006 int force, enum migrate_mode mode)
1009 int page_was_mapped = 0;
1010 struct anon_vma *anon_vma = NULL;
1011 bool is_lru = !__PageMovable(page);
1013 if (!trylock_page(page)) {
1014 if (!force || mode == MIGRATE_ASYNC)
1018 * It's not safe for direct compaction to call lock_page.
1019 * For example, during page readahead pages are added locked
1020 * to the LRU. Later, when the IO completes the pages are
1021 * marked uptodate and unlocked. However, the queueing
1022 * could be merging multiple pages for one bio (e.g.
1023 * mpage_readpages). If an allocation happens for the
1024 * second or third page, the process can end up locking
1025 * the same page twice and deadlocking. Rather than
1026 * trying to be clever about what pages can be locked,
1027 * avoid the use of lock_page for direct compaction
1030 if (current->flags & PF_MEMALLOC)
1036 if (PageWriteback(page)) {
1038 * Only in the case of a full synchronous migration is it
1039 * necessary to wait for PageWriteback. In the async case,
1040 * the retry loop is too short and in the sync-light case,
1041 * the overhead of stalling is too much
1045 case MIGRATE_SYNC_NO_COPY:
1053 wait_on_page_writeback(page);
1057 * By try_to_unmap(), page->mapcount goes down to 0 here. In this case,
1058 * we cannot notice that anon_vma is freed while we migrates a page.
1059 * This get_anon_vma() delays freeing anon_vma pointer until the end
1060 * of migration. File cache pages are no problem because of page_lock()
1061 * File Caches may use write_page() or lock_page() in migration, then,
1062 * just care Anon page here.
1064 * Only page_get_anon_vma() understands the subtleties of
1065 * getting a hold on an anon_vma from outside one of its mms.
1066 * But if we cannot get anon_vma, then we won't need it anyway,
1067 * because that implies that the anon page is no longer mapped
1068 * (and cannot be remapped so long as we hold the page lock).
1070 if (PageAnon(page) && !PageKsm(page))
1071 anon_vma = page_get_anon_vma(page);
1074 * Block others from accessing the new page when we get around to
1075 * establishing additional references. We are usually the only one
1076 * holding a reference to newpage at this point. We used to have a BUG
1077 * here if trylock_page(newpage) fails, but would like to allow for
1078 * cases where there might be a race with the previous use of newpage.
1079 * This is much like races on refcount of oldpage: just don't BUG().
1081 if (unlikely(!trylock_page(newpage)))
1084 if (unlikely(!is_lru)) {
1085 rc = move_to_new_page(newpage, page, mode);
1086 goto out_unlock_both;
1090 * Corner case handling:
1091 * 1. When a new swap-cache page is read into, it is added to the LRU
1092 * and treated as swapcache but it has no rmap yet.
1093 * Calling try_to_unmap() against a page->mapping==NULL page will
1094 * trigger a BUG. So handle it here.
1095 * 2. An orphaned page (see truncate_complete_page) might have
1096 * fs-private metadata. The page can be picked up due to memory
1097 * offlining. Everywhere else except page reclaim, the page is
1098 * invisible to the vm, so the page can not be migrated. So try to
1099 * free the metadata, so the page can be freed.
1101 if (!page->mapping) {
1102 VM_BUG_ON_PAGE(PageAnon(page), page);
1103 if (page_has_private(page)) {
1104 try_to_free_buffers(page);
1105 goto out_unlock_both;
1107 } else if (page_mapped(page)) {
1108 /* Establish migration ptes */
1109 VM_BUG_ON_PAGE(PageAnon(page) && !PageKsm(page) && !anon_vma,
1112 TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
1113 page_was_mapped = 1;
1116 if (!page_mapped(page))
1117 rc = move_to_new_page(newpage, page, mode);
1119 if (page_was_mapped)
1120 remove_migration_ptes(page,
1121 rc == MIGRATEPAGE_SUCCESS ? newpage : page, false);
1124 unlock_page(newpage);
1126 /* Drop an anon_vma reference if we took one */
1128 put_anon_vma(anon_vma);
1132 * If migration is successful, decrease refcount of the newpage
1133 * which will not free the page because new page owner increased
1134 * refcounter. As well, if it is LRU page, add the page to LRU
1135 * list in here. Use the old state of the isolated source page to
1136 * determine if we migrated a LRU page. newpage was already unlocked
1137 * and possibly modified by its owner - don't rely on the page
1140 if (rc == MIGRATEPAGE_SUCCESS) {
1141 if (unlikely(!is_lru))
1144 putback_lru_page(newpage);
1151 * gcc 4.7 and 4.8 on arm get an ICEs when inlining unmap_and_move(). Work
1154 #if defined(CONFIG_ARM) && \
1155 defined(GCC_VERSION) && GCC_VERSION < 40900 && GCC_VERSION >= 40700
1156 #define ICE_noinline noinline
1158 #define ICE_noinline
1162 * Obtain the lock on page, remove all ptes and migrate the page
1163 * to the newly allocated page in newpage.
1165 static ICE_noinline int unmap_and_move(new_page_t get_new_page,
1166 free_page_t put_new_page,
1167 unsigned long private, struct page *page,
1168 int force, enum migrate_mode mode,
1169 enum migrate_reason reason)
1171 int rc = MIGRATEPAGE_SUCCESS;
1172 struct page *newpage = NULL;
1174 if (!thp_migration_supported() && PageTransHuge(page))
1177 if (page_count(page) == 1) {
1178 /* page was freed from under us. So we are done. */
1179 ClearPageActive(page);
1180 ClearPageUnevictable(page);
1181 if (unlikely(__PageMovable(page))) {
1183 if (!PageMovable(page))
1184 __ClearPageIsolated(page);
1190 newpage = get_new_page(page, private);
1194 rc = __unmap_and_move(page, newpage, force, mode);
1195 if (rc == MIGRATEPAGE_SUCCESS)
1196 set_page_owner_migrate_reason(newpage, reason);
1199 if (rc != -EAGAIN) {
1201 * A page that has been migrated has all references
1202 * removed and will be freed. A page that has not been
1203 * migrated will have kept its references and be restored.
1205 list_del(&page->lru);
1208 * Compaction can migrate also non-LRU pages which are
1209 * not accounted to NR_ISOLATED_*. They can be recognized
1212 if (likely(!__PageMovable(page)))
1213 mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON +
1214 page_is_file_cache(page), -hpage_nr_pages(page));
1218 * If migration is successful, releases reference grabbed during
1219 * isolation. Otherwise, restore the page to right list unless
1222 if (rc == MIGRATEPAGE_SUCCESS) {
1224 if (reason == MR_MEMORY_FAILURE) {
1226 * Set PG_HWPoison on just freed page
1227 * intentionally. Although it's rather weird,
1228 * it's how HWPoison flag works at the moment.
1230 if (set_hwpoison_free_buddy_page(page))
1231 num_poisoned_pages_inc();
1234 if (rc != -EAGAIN) {
1235 if (likely(!__PageMovable(page))) {
1236 putback_lru_page(page);
1241 if (PageMovable(page))
1242 putback_movable_page(page);
1244 __ClearPageIsolated(page);
1250 put_new_page(newpage, private);
1259 * Counterpart of unmap_and_move_page() for hugepage migration.
1261 * This function doesn't wait the completion of hugepage I/O
1262 * because there is no race between I/O and migration for hugepage.
1263 * Note that currently hugepage I/O occurs only in direct I/O
1264 * where no lock is held and PG_writeback is irrelevant,
1265 * and writeback status of all subpages are counted in the reference
1266 * count of the head page (i.e. if all subpages of a 2MB hugepage are
1267 * under direct I/O, the reference of the head page is 512 and a bit more.)
1268 * This means that when we try to migrate hugepage whose subpages are
1269 * doing direct I/O, some references remain after try_to_unmap() and
1270 * hugepage migration fails without data corruption.
1272 * There is also no race when direct I/O is issued on the page under migration,
1273 * because then pte is replaced with migration swap entry and direct I/O code
1274 * will wait in the page fault for migration to complete.
1276 static int unmap_and_move_huge_page(new_page_t get_new_page,
1277 free_page_t put_new_page, unsigned long private,
1278 struct page *hpage, int force,
1279 enum migrate_mode mode, int reason)
1282 int page_was_mapped = 0;
1283 struct page *new_hpage;
1284 struct anon_vma *anon_vma = NULL;
1285 struct address_space *mapping = NULL;
1288 * Migratability of hugepages depends on architectures and their size.
1289 * This check is necessary because some callers of hugepage migration
1290 * like soft offline and memory hotremove don't walk through page
1291 * tables or check whether the hugepage is pmd-based or not before
1292 * kicking migration.
1294 if (!hugepage_migration_supported(page_hstate(hpage))) {
1295 putback_active_hugepage(hpage);
1299 new_hpage = get_new_page(hpage, private);
1303 if (!trylock_page(hpage)) {
1308 case MIGRATE_SYNC_NO_COPY:
1317 * Check for pages which are in the process of being freed. Without
1318 * page_mapping() set, hugetlbfs specific move page routine will not
1319 * be called and we could leak usage counts for subpools.
1321 if (page_private(hpage) && !page_mapping(hpage)) {
1326 if (PageAnon(hpage))
1327 anon_vma = page_get_anon_vma(hpage);
1329 if (unlikely(!trylock_page(new_hpage)))
1332 if (page_mapped(hpage)) {
1334 * try_to_unmap could potentially call huge_pmd_unshare.
1335 * Because of this, take semaphore in write mode here and
1336 * set TTU_RMAP_LOCKED to let lower levels know we have
1339 mapping = hugetlb_page_mapping_lock_write(hpage);
1340 if (unlikely(!mapping))
1341 goto unlock_put_anon;
1344 TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS|
1346 page_was_mapped = 1;
1348 * Leave mapping locked until after subsequent call to
1349 * remove_migration_ptes()
1353 if (!page_mapped(hpage))
1354 rc = move_to_new_page(new_hpage, hpage, mode);
1356 if (page_was_mapped) {
1357 remove_migration_ptes(hpage,
1358 rc == MIGRATEPAGE_SUCCESS ? new_hpage : hpage, true);
1359 i_mmap_unlock_write(mapping);
1363 unlock_page(new_hpage);
1367 put_anon_vma(anon_vma);
1369 if (rc == MIGRATEPAGE_SUCCESS) {
1370 move_hugetlb_state(hpage, new_hpage, reason);
1371 put_new_page = NULL;
1378 putback_active_hugepage(hpage);
1381 * If migration was not successful and there's a freeing callback, use
1382 * it. Otherwise, put_page() will drop the reference grabbed during
1386 put_new_page(new_hpage, private);
1388 putback_active_hugepage(new_hpage);
1394 * migrate_pages - migrate the pages specified in a list, to the free pages
1395 * supplied as the target for the page migration
1397 * @from: The list of pages to be migrated.
1398 * @get_new_page: The function used to allocate free pages to be used
1399 * as the target of the page migration.
1400 * @put_new_page: The function used to free target pages if migration
1401 * fails, or NULL if no special handling is necessary.
1402 * @private: Private data to be passed on to get_new_page()
1403 * @mode: The migration mode that specifies the constraints for
1404 * page migration, if any.
1405 * @reason: The reason for page migration.
1407 * The function returns after 10 attempts or if no pages are movable any more
1408 * because the list has become empty or no retryable pages exist any more.
1409 * The caller should call putback_movable_pages() to return pages to the LRU
1410 * or free list only if ret != 0.
1412 * Returns the number of pages that were not migrated, or an error code.
1414 int migrate_pages(struct list_head *from, new_page_t get_new_page,
1415 free_page_t put_new_page, unsigned long private,
1416 enum migrate_mode mode, int reason)
1420 int nr_succeeded = 0;
1424 int swapwrite = current->flags & PF_SWAPWRITE;
1428 current->flags |= PF_SWAPWRITE;
1430 for(pass = 0; pass < 10 && retry; pass++) {
1433 list_for_each_entry_safe(page, page2, from, lru) {
1438 rc = unmap_and_move_huge_page(get_new_page,
1439 put_new_page, private, page,
1440 pass > 2, mode, reason);
1442 rc = unmap_and_move(get_new_page, put_new_page,
1443 private, page, pass > 2, mode,
1449 * THP migration might be unsupported or the
1450 * allocation could've failed so we should
1451 * retry on the same page with the THP split
1454 * Head page is retried immediately and tail
1455 * pages are added to the tail of the list so
1456 * we encounter them after the rest of the list
1459 if (PageTransHuge(page) && !PageHuge(page)) {
1461 rc = split_huge_page_to_list(page, from);
1464 list_safe_reset_next(page, page2, lru);
1473 case MIGRATEPAGE_SUCCESS:
1478 * Permanent failure (-EBUSY, -ENOSYS, etc.):
1479 * unlike -EAGAIN case, the failed page is
1480 * removed from migration page list and not
1481 * retried in the next outer loop.
1492 count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded);
1494 count_vm_events(PGMIGRATE_FAIL, nr_failed);
1495 trace_mm_migrate_pages(nr_succeeded, nr_failed, mode, reason);
1498 current->flags &= ~PF_SWAPWRITE;
1505 static int store_status(int __user *status, int start, int value, int nr)
1508 if (put_user(value, status + start))
1516 static int do_move_pages_to_node(struct mm_struct *mm,
1517 struct list_head *pagelist, int node)
1521 if (list_empty(pagelist))
1524 err = migrate_pages(pagelist, alloc_new_node_page, NULL, node,
1525 MIGRATE_SYNC, MR_SYSCALL);
1527 putback_movable_pages(pagelist);
1532 * Resolves the given address to a struct page, isolates it from the LRU and
1533 * puts it to the given pagelist.
1535 * errno - if the page cannot be found/isolated
1536 * 0 - when it doesn't have to be migrated because it is already on the
1538 * 1 - when it has been queued
1540 static int add_page_for_migration(struct mm_struct *mm, unsigned long addr,
1541 int node, struct list_head *pagelist, bool migrate_all)
1543 struct vm_area_struct *vma;
1545 unsigned int follflags;
1548 down_read(&mm->mmap_sem);
1550 vma = find_vma(mm, addr);
1551 if (!vma || addr < vma->vm_start || !vma_migratable(vma))
1554 /* FOLL_DUMP to ignore special (like zero) pages */
1555 follflags = FOLL_GET | FOLL_DUMP;
1556 page = follow_page(vma, addr, follflags);
1558 err = PTR_ERR(page);
1567 if (page_to_nid(page) == node)
1571 if (page_mapcount(page) > 1 && !migrate_all)
1574 if (PageHuge(page)) {
1575 if (PageHead(page)) {
1576 isolate_huge_page(page, pagelist);
1582 head = compound_head(page);
1583 err = isolate_lru_page(head);
1588 list_add_tail(&head->lru, pagelist);
1589 mod_node_page_state(page_pgdat(head),
1590 NR_ISOLATED_ANON + page_is_file_cache(head),
1591 hpage_nr_pages(head));
1595 * Either remove the duplicate refcount from
1596 * isolate_lru_page() or drop the page ref if it was
1601 up_read(&mm->mmap_sem);
1605 static int move_pages_and_store_status(struct mm_struct *mm, int node,
1606 struct list_head *pagelist, int __user *status,
1607 int start, int i, unsigned long nr_pages)
1611 err = do_move_pages_to_node(mm, pagelist, node);
1614 * Positive err means the number of failed
1615 * pages to migrate. Since we are going to
1616 * abort and return the number of non-migrated
1617 * pages, so need to incude the rest of the
1618 * nr_pages that have not been attempted as
1622 err += nr_pages - i - 1;
1625 return store_status(status, start, node, i - start);
1629 * Migrate an array of page address onto an array of nodes and fill
1630 * the corresponding array of status.
1632 static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
1633 unsigned long nr_pages,
1634 const void __user * __user *pages,
1635 const int __user *nodes,
1636 int __user *status, int flags)
1638 int current_node = NUMA_NO_NODE;
1639 LIST_HEAD(pagelist);
1645 for (i = start = 0; i < nr_pages; i++) {
1646 const void __user *p;
1651 if (get_user(p, pages + i))
1653 if (get_user(node, nodes + i))
1655 addr = (unsigned long)untagged_addr(p);
1658 if (node < 0 || node >= MAX_NUMNODES)
1660 if (!node_state(node, N_MEMORY))
1664 if (!node_isset(node, task_nodes))
1667 if (current_node == NUMA_NO_NODE) {
1668 current_node = node;
1670 } else if (node != current_node) {
1671 err = move_pages_and_store_status(mm, current_node,
1672 &pagelist, status, start, i, nr_pages);
1676 current_node = node;
1680 * Errors in the page lookup or isolation are not fatal and we simply
1681 * report them via status
1683 err = add_page_for_migration(mm, addr, current_node,
1684 &pagelist, flags & MPOL_MF_MOVE_ALL);
1687 /* The page is already on the target node */
1688 err = store_status(status, i, current_node, 1);
1692 } else if (err > 0) {
1693 /* The page is successfully queued for migration */
1697 err = store_status(status, i, err, 1);
1701 err = move_pages_and_store_status(mm, current_node, &pagelist,
1702 status, start, i, nr_pages);
1705 current_node = NUMA_NO_NODE;
1708 if (list_empty(&pagelist))
1711 /* Make sure we do not overwrite the existing error */
1712 err1 = move_pages_and_store_status(mm, current_node, &pagelist,
1713 status, start, i, nr_pages);
1721 * Determine the nodes of an array of pages and store it in an array of status.
1723 static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
1724 const void __user **pages, int *status)
1728 down_read(&mm->mmap_sem);
1730 for (i = 0; i < nr_pages; i++) {
1731 unsigned long addr = (unsigned long)(*pages);
1732 struct vm_area_struct *vma;
1736 vma = find_vma(mm, addr);
1737 if (!vma || addr < vma->vm_start)
1740 /* FOLL_DUMP to ignore special (like zero) pages */
1741 page = follow_page(vma, addr, FOLL_DUMP);
1743 err = PTR_ERR(page);
1747 err = page ? page_to_nid(page) : -ENOENT;
1755 up_read(&mm->mmap_sem);
1759 * Determine the nodes of a user array of pages and store it in
1760 * a user array of status.
1762 static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
1763 const void __user * __user *pages,
1766 #define DO_PAGES_STAT_CHUNK_NR 16
1767 const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR];
1768 int chunk_status[DO_PAGES_STAT_CHUNK_NR];
1771 unsigned long chunk_nr;
1773 chunk_nr = nr_pages;
1774 if (chunk_nr > DO_PAGES_STAT_CHUNK_NR)
1775 chunk_nr = DO_PAGES_STAT_CHUNK_NR;
1777 if (copy_from_user(chunk_pages, pages, chunk_nr * sizeof(*chunk_pages)))
1780 do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status);
1782 if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status)))
1787 nr_pages -= chunk_nr;
1789 return nr_pages ? -EFAULT : 0;
1793 * Move a list of pages in the address space of the currently executing
1796 static int kernel_move_pages(pid_t pid, unsigned long nr_pages,
1797 const void __user * __user *pages,
1798 const int __user *nodes,
1799 int __user *status, int flags)
1801 struct task_struct *task;
1802 struct mm_struct *mm;
1804 nodemask_t task_nodes;
1807 if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL))
1810 if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
1813 /* Find the mm_struct */
1815 task = pid ? find_task_by_vpid(pid) : current;
1820 get_task_struct(task);
1823 * Check if this process has the right to modify the specified
1824 * process. Use the regular "ptrace_may_access()" checks.
1826 if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) {
1833 err = security_task_movememory(task);
1837 task_nodes = cpuset_mems_allowed(task);
1838 mm = get_task_mm(task);
1839 put_task_struct(task);
1845 err = do_pages_move(mm, task_nodes, nr_pages, pages,
1846 nodes, status, flags);
1848 err = do_pages_stat(mm, nr_pages, pages, status);
1854 put_task_struct(task);
1858 SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages,
1859 const void __user * __user *, pages,
1860 const int __user *, nodes,
1861 int __user *, status, int, flags)
1863 return kernel_move_pages(pid, nr_pages, pages, nodes, status, flags);
1866 #ifdef CONFIG_COMPAT
1867 COMPAT_SYSCALL_DEFINE6(move_pages, pid_t, pid, compat_ulong_t, nr_pages,
1868 compat_uptr_t __user *, pages32,
1869 const int __user *, nodes,
1870 int __user *, status,
1873 const void __user * __user *pages;
1876 pages = compat_alloc_user_space(nr_pages * sizeof(void *));
1877 for (i = 0; i < nr_pages; i++) {
1880 if (get_user(p, pages32 + i) ||
1881 put_user(compat_ptr(p), pages + i))
1884 return kernel_move_pages(pid, nr_pages, pages, nodes, status, flags);
1886 #endif /* CONFIG_COMPAT */
1888 #ifdef CONFIG_NUMA_BALANCING
1890 * Returns true if this is a safe migration target node for misplaced NUMA
1891 * pages. Currently it only checks the watermarks which crude
1893 static bool migrate_balanced_pgdat(struct pglist_data *pgdat,
1894 unsigned long nr_migrate_pages)
1898 for (z = pgdat->nr_zones - 1; z >= 0; z--) {
1899 struct zone *zone = pgdat->node_zones + z;
1901 if (!populated_zone(zone))
1904 /* Avoid waking kswapd by allocating pages_to_migrate pages. */
1905 if (!zone_watermark_ok(zone, 0,
1906 high_wmark_pages(zone) +
1915 static struct page *alloc_misplaced_dst_page(struct page *page,
1918 int nid = (int) data;
1919 struct page *newpage;
1921 newpage = __alloc_pages_node(nid,
1922 (GFP_HIGHUSER_MOVABLE |
1923 __GFP_THISNODE | __GFP_NOMEMALLOC |
1924 __GFP_NORETRY | __GFP_NOWARN) &
1930 static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
1934 VM_BUG_ON_PAGE(compound_order(page) && !PageTransHuge(page), page);
1936 /* Avoid migrating to a node that is nearly full */
1937 if (!migrate_balanced_pgdat(pgdat, compound_nr(page)))
1940 if (isolate_lru_page(page))
1944 * migrate_misplaced_transhuge_page() skips page migration's usual
1945 * check on page_count(), so we must do it here, now that the page
1946 * has been isolated: a GUP pin, or any other pin, prevents migration.
1947 * The expected page count is 3: 1 for page's mapcount and 1 for the
1948 * caller's pin and 1 for the reference taken by isolate_lru_page().
1950 if (PageTransHuge(page) && page_count(page) != 3) {
1951 putback_lru_page(page);
1955 page_lru = page_is_file_cache(page);
1956 mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + page_lru,
1957 hpage_nr_pages(page));
1960 * Isolating the page has taken another reference, so the
1961 * caller's reference can be safely dropped without the page
1962 * disappearing underneath us during migration.
1968 bool pmd_trans_migrating(pmd_t pmd)
1970 struct page *page = pmd_page(pmd);
1971 return PageLocked(page);
1975 * Attempt to migrate a misplaced page to the specified destination
1976 * node. Caller is expected to have an elevated reference count on
1977 * the page that will be dropped by this function before returning.
1979 int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
1982 pg_data_t *pgdat = NODE_DATA(node);
1985 LIST_HEAD(migratepages);
1988 * Don't migrate file pages that are mapped in multiple processes
1989 * with execute permissions as they are probably shared libraries.
1991 if (page_mapcount(page) != 1 && page_is_file_cache(page) &&
1992 (vma->vm_flags & VM_EXEC))
1996 * Also do not migrate dirty pages as not all filesystems can move
1997 * dirty pages in MIGRATE_ASYNC mode which is a waste of cycles.
1999 if (page_is_file_cache(page) && PageDirty(page))
2002 isolated = numamigrate_isolate_page(pgdat, page);
2006 list_add(&page->lru, &migratepages);
2007 nr_remaining = migrate_pages(&migratepages, alloc_misplaced_dst_page,
2008 NULL, node, MIGRATE_ASYNC,
2011 if (!list_empty(&migratepages)) {
2012 list_del(&page->lru);
2013 dec_node_page_state(page, NR_ISOLATED_ANON +
2014 page_is_file_cache(page));
2015 putback_lru_page(page);
2019 count_vm_numa_event(NUMA_PAGE_MIGRATE);
2020 BUG_ON(!list_empty(&migratepages));
2027 #endif /* CONFIG_NUMA_BALANCING */
2029 #if defined(CONFIG_NUMA_BALANCING) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
2031 * Migrates a THP to a given target node. page must be locked and is unlocked
2034 int migrate_misplaced_transhuge_page(struct mm_struct *mm,
2035 struct vm_area_struct *vma,
2036 pmd_t *pmd, pmd_t entry,
2037 unsigned long address,
2038 struct page *page, int node)
2041 pg_data_t *pgdat = NODE_DATA(node);
2043 struct page *new_page = NULL;
2044 int page_lru = page_is_file_cache(page);
2045 unsigned long start = address & HPAGE_PMD_MASK;
2047 new_page = alloc_pages_node(node,
2048 (GFP_TRANSHUGE_LIGHT | __GFP_THISNODE),
2052 prep_transhuge_page(new_page);
2054 isolated = numamigrate_isolate_page(pgdat, page);
2060 /* Prepare a page as a migration target */
2061 __SetPageLocked(new_page);
2062 if (PageSwapBacked(page))
2063 __SetPageSwapBacked(new_page);
2065 /* anon mapping, we can simply copy page->mapping to the new page: */
2066 new_page->mapping = page->mapping;
2067 new_page->index = page->index;
2068 /* flush the cache before copying using the kernel virtual address */
2069 flush_cache_range(vma, start, start + HPAGE_PMD_SIZE);
2070 migrate_page_copy(new_page, page);
2071 WARN_ON(PageLRU(new_page));
2073 /* Recheck the target PMD */
2074 ptl = pmd_lock(mm, pmd);
2075 if (unlikely(!pmd_same(*pmd, entry) || !page_ref_freeze(page, 2))) {
2078 /* Reverse changes made by migrate_page_copy() */
2079 if (TestClearPageActive(new_page))
2080 SetPageActive(page);
2081 if (TestClearPageUnevictable(new_page))
2082 SetPageUnevictable(page);
2084 unlock_page(new_page);
2085 put_page(new_page); /* Free it */
2087 /* Retake the callers reference and putback on LRU */
2089 putback_lru_page(page);
2090 mod_node_page_state(page_pgdat(page),
2091 NR_ISOLATED_ANON + page_lru, -HPAGE_PMD_NR);
2096 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
2097 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
2100 * Overwrite the old entry under pagetable lock and establish
2101 * the new PTE. Any parallel GUP will either observe the old
2102 * page blocking on the page lock, block on the page table
2103 * lock or observe the new page. The SetPageUptodate on the
2104 * new page and page_add_new_anon_rmap guarantee the copy is
2105 * visible before the pagetable update.
2107 page_add_anon_rmap(new_page, vma, start, true);
2109 * At this point the pmd is numa/protnone (i.e. non present) and the TLB
2110 * has already been flushed globally. So no TLB can be currently
2111 * caching this non present pmd mapping. There's no need to clear the
2112 * pmd before doing set_pmd_at(), nor to flush the TLB after
2113 * set_pmd_at(). Clearing the pmd here would introduce a race
2114 * condition against MADV_DONTNEED, because MADV_DONTNEED only holds the
2115 * mmap_sem for reading. If the pmd is set to NULL at any given time,
2116 * MADV_DONTNEED won't wait on the pmd lock and it'll skip clearing this
2119 set_pmd_at(mm, start, pmd, entry);
2120 update_mmu_cache_pmd(vma, address, &entry);
2122 page_ref_unfreeze(page, 2);
2123 mlock_migrate_page(new_page, page);
2124 page_remove_rmap(page, true);
2125 set_page_owner_migrate_reason(new_page, MR_NUMA_MISPLACED);
2129 /* Take an "isolate" reference and put new page on the LRU. */
2131 putback_lru_page(new_page);
2133 unlock_page(new_page);
2135 put_page(page); /* Drop the rmap reference */
2136 put_page(page); /* Drop the LRU isolation reference */
2138 count_vm_events(PGMIGRATE_SUCCESS, HPAGE_PMD_NR);
2139 count_vm_numa_events(NUMA_PAGE_MIGRATE, HPAGE_PMD_NR);
2141 mod_node_page_state(page_pgdat(page),
2142 NR_ISOLATED_ANON + page_lru,
2147 count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR);
2148 ptl = pmd_lock(mm, pmd);
2149 if (pmd_same(*pmd, entry)) {
2150 entry = pmd_modify(entry, vma->vm_page_prot);
2151 set_pmd_at(mm, start, pmd, entry);
2152 update_mmu_cache_pmd(vma, address, &entry);
2161 #endif /* CONFIG_NUMA_BALANCING */
2163 #endif /* CONFIG_NUMA */
2165 #ifdef CONFIG_DEVICE_PRIVATE
2166 static int migrate_vma_collect_hole(unsigned long start,
2168 __always_unused int depth,
2169 struct mm_walk *walk)
2171 struct migrate_vma *migrate = walk->private;
2174 for (addr = start; addr < end; addr += PAGE_SIZE) {
2175 migrate->src[migrate->npages] = MIGRATE_PFN_MIGRATE;
2176 migrate->dst[migrate->npages] = 0;
2184 static int migrate_vma_collect_skip(unsigned long start,
2186 struct mm_walk *walk)
2188 struct migrate_vma *migrate = walk->private;
2191 for (addr = start; addr < end; addr += PAGE_SIZE) {
2192 migrate->dst[migrate->npages] = 0;
2193 migrate->src[migrate->npages++] = 0;
2199 static int migrate_vma_collect_pmd(pmd_t *pmdp,
2200 unsigned long start,
2202 struct mm_walk *walk)
2204 struct migrate_vma *migrate = walk->private;
2205 struct vm_area_struct *vma = walk->vma;
2206 struct mm_struct *mm = vma->vm_mm;
2207 unsigned long addr = start, unmapped = 0;
2212 if (pmd_none(*pmdp))
2213 return migrate_vma_collect_hole(start, end, -1, walk);
2215 if (pmd_trans_huge(*pmdp)) {
2218 ptl = pmd_lock(mm, pmdp);
2219 if (unlikely(!pmd_trans_huge(*pmdp))) {
2224 page = pmd_page(*pmdp);
2225 if (is_huge_zero_page(page)) {
2227 split_huge_pmd(vma, pmdp, addr);
2228 if (pmd_trans_unstable(pmdp))
2229 return migrate_vma_collect_skip(start, end,
2236 if (unlikely(!trylock_page(page)))
2237 return migrate_vma_collect_skip(start, end,
2239 ret = split_huge_page(page);
2243 return migrate_vma_collect_skip(start, end,
2245 if (pmd_none(*pmdp))
2246 return migrate_vma_collect_hole(start, end, -1,
2251 if (unlikely(pmd_bad(*pmdp)))
2252 return migrate_vma_collect_skip(start, end, walk);
2254 ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
2255 arch_enter_lazy_mmu_mode();
2257 for (; addr < end; addr += PAGE_SIZE, ptep++) {
2258 unsigned long mpfn = 0, pfn;
2265 if (pte_none(pte)) {
2266 mpfn = MIGRATE_PFN_MIGRATE;
2271 if (!pte_present(pte)) {
2273 * Only care about unaddressable device page special
2274 * page table entry. Other special swap entries are not
2275 * migratable, and we ignore regular swapped page.
2277 entry = pte_to_swp_entry(pte);
2278 if (!is_device_private_entry(entry))
2281 page = device_private_entry_to_page(entry);
2282 if (page->pgmap->owner != migrate->src_owner)
2285 mpfn = migrate_pfn(page_to_pfn(page)) |
2286 MIGRATE_PFN_MIGRATE;
2287 if (is_write_device_private_entry(entry))
2288 mpfn |= MIGRATE_PFN_WRITE;
2290 if (migrate->src_owner)
2293 if (is_zero_pfn(pfn)) {
2294 mpfn = MIGRATE_PFN_MIGRATE;
2298 page = vm_normal_page(migrate->vma, addr, pte);
2299 mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
2300 mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0;
2303 /* FIXME support THP */
2304 if (!page || !page->mapping || PageTransCompound(page)) {
2310 * By getting a reference on the page we pin it and that blocks
2311 * any kind of migration. Side effect is that it "freezes" the
2314 * We drop this reference after isolating the page from the lru
2315 * for non device page (device page are not on the lru and thus
2316 * can't be dropped from it).
2322 * Optimize for the common case where page is only mapped once
2323 * in one process. If we can lock the page, then we can safely
2324 * set up a special migration page table entry now.
2326 if (trylock_page(page)) {
2329 mpfn |= MIGRATE_PFN_LOCKED;
2330 ptep_get_and_clear(mm, addr, ptep);
2332 /* Setup special migration page table entry */
2333 entry = make_migration_entry(page, mpfn &
2335 swp_pte = swp_entry_to_pte(entry);
2336 if (pte_soft_dirty(pte))
2337 swp_pte = pte_swp_mksoft_dirty(swp_pte);
2338 set_pte_at(mm, addr, ptep, swp_pte);
2341 * This is like regular unmap: we remove the rmap and
2342 * drop page refcount. Page won't be freed, as we took
2343 * a reference just above.
2345 page_remove_rmap(page, false);
2348 if (pte_present(pte))
2353 migrate->dst[migrate->npages] = 0;
2354 migrate->src[migrate->npages++] = mpfn;
2356 arch_leave_lazy_mmu_mode();
2357 pte_unmap_unlock(ptep - 1, ptl);
2359 /* Only flush the TLB if we actually modified any entries */
2361 flush_tlb_range(walk->vma, start, end);
2366 static const struct mm_walk_ops migrate_vma_walk_ops = {
2367 .pmd_entry = migrate_vma_collect_pmd,
2368 .pte_hole = migrate_vma_collect_hole,
2372 * migrate_vma_collect() - collect pages over a range of virtual addresses
2373 * @migrate: migrate struct containing all migration information
2375 * This will walk the CPU page table. For each virtual address backed by a
2376 * valid page, it updates the src array and takes a reference on the page, in
2377 * order to pin the page until we lock it and unmap it.
2379 static void migrate_vma_collect(struct migrate_vma *migrate)
2381 struct mmu_notifier_range range;
2383 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, NULL,
2384 migrate->vma->vm_mm, migrate->start, migrate->end);
2385 mmu_notifier_invalidate_range_start(&range);
2387 walk_page_range(migrate->vma->vm_mm, migrate->start, migrate->end,
2388 &migrate_vma_walk_ops, migrate);
2390 mmu_notifier_invalidate_range_end(&range);
2391 migrate->end = migrate->start + (migrate->npages << PAGE_SHIFT);
2395 * migrate_vma_check_page() - check if page is pinned or not
2396 * @page: struct page to check
2398 * Pinned pages cannot be migrated. This is the same test as in
2399 * migrate_page_move_mapping(), except that here we allow migration of a
2402 static bool migrate_vma_check_page(struct page *page)
2405 * One extra ref because caller holds an extra reference, either from
2406 * isolate_lru_page() for a regular page, or migrate_vma_collect() for
2412 * FIXME support THP (transparent huge page), it is bit more complex to
2413 * check them than regular pages, because they can be mapped with a pmd
2414 * or with a pte (split pte mapping).
2416 if (PageCompound(page))
2419 /* Page from ZONE_DEVICE have one extra reference */
2420 if (is_zone_device_page(page)) {
2422 * Private page can never be pin as they have no valid pte and
2423 * GUP will fail for those. Yet if there is a pending migration
2424 * a thread might try to wait on the pte migration entry and
2425 * will bump the page reference count. Sadly there is no way to
2426 * differentiate a regular pin from migration wait. Hence to
2427 * avoid 2 racing thread trying to migrate back to CPU to enter
2428 * infinite loop (one stoping migration because the other is
2429 * waiting on pte migration entry). We always return true here.
2431 * FIXME proper solution is to rework migration_entry_wait() so
2432 * it does not need to take a reference on page.
2434 return is_device_private_page(page);
2437 /* For file back page */
2438 if (page_mapping(page))
2439 extra += 1 + page_has_private(page);
2441 if ((page_count(page) - extra) > page_mapcount(page))
2448 * migrate_vma_prepare() - lock pages and isolate them from the lru
2449 * @migrate: migrate struct containing all migration information
2451 * This locks pages that have been collected by migrate_vma_collect(). Once each
2452 * page is locked it is isolated from the lru (for non-device pages). Finally,
2453 * the ref taken by migrate_vma_collect() is dropped, as locked pages cannot be
2454 * migrated by concurrent kernel threads.
2456 static void migrate_vma_prepare(struct migrate_vma *migrate)
2458 const unsigned long npages = migrate->npages;
2459 const unsigned long start = migrate->start;
2460 unsigned long addr, i, restore = 0;
2461 bool allow_drain = true;
2465 for (i = 0; (i < npages) && migrate->cpages; i++) {
2466 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2472 if (!(migrate->src[i] & MIGRATE_PFN_LOCKED)) {
2474 * Because we are migrating several pages there can be
2475 * a deadlock between 2 concurrent migration where each
2476 * are waiting on each other page lock.
2478 * Make migrate_vma() a best effort thing and backoff
2479 * for any page we can not lock right away.
2481 if (!trylock_page(page)) {
2482 migrate->src[i] = 0;
2488 migrate->src[i] |= MIGRATE_PFN_LOCKED;
2491 /* ZONE_DEVICE pages are not on LRU */
2492 if (!is_zone_device_page(page)) {
2493 if (!PageLRU(page) && allow_drain) {
2494 /* Drain CPU's pagevec */
2495 lru_add_drain_all();
2496 allow_drain = false;
2499 if (isolate_lru_page(page)) {
2501 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2505 migrate->src[i] = 0;
2513 /* Drop the reference we took in collect */
2517 if (!migrate_vma_check_page(page)) {
2519 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2523 if (!is_zone_device_page(page)) {
2525 putback_lru_page(page);
2528 migrate->src[i] = 0;
2532 if (!is_zone_device_page(page))
2533 putback_lru_page(page);
2540 for (i = 0, addr = start; i < npages && restore; i++, addr += PAGE_SIZE) {
2541 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2543 if (!page || (migrate->src[i] & MIGRATE_PFN_MIGRATE))
2546 remove_migration_pte(page, migrate->vma, addr, page);
2548 migrate->src[i] = 0;
2556 * migrate_vma_unmap() - replace page mapping with special migration pte entry
2557 * @migrate: migrate struct containing all migration information
2559 * Replace page mapping (CPU page table pte) with a special migration pte entry
2560 * and check again if it has been pinned. Pinned pages are restored because we
2561 * cannot migrate them.
2563 * This is the last step before we call the device driver callback to allocate
2564 * destination memory and copy contents of original page over to new page.
2566 static void migrate_vma_unmap(struct migrate_vma *migrate)
2568 int flags = TTU_MIGRATION | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
2569 const unsigned long npages = migrate->npages;
2570 const unsigned long start = migrate->start;
2571 unsigned long addr, i, restore = 0;
2573 for (i = 0; i < npages; i++) {
2574 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2576 if (!page || !(migrate->src[i] & MIGRATE_PFN_MIGRATE))
2579 if (page_mapped(page)) {
2580 try_to_unmap(page, flags);
2581 if (page_mapped(page))
2585 if (migrate_vma_check_page(page))
2589 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2594 for (addr = start, i = 0; i < npages && restore; addr += PAGE_SIZE, i++) {
2595 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2597 if (!page || (migrate->src[i] & MIGRATE_PFN_MIGRATE))
2600 remove_migration_ptes(page, page, false);
2602 migrate->src[i] = 0;
2606 if (is_zone_device_page(page))
2609 putback_lru_page(page);
2614 * migrate_vma_setup() - prepare to migrate a range of memory
2615 * @args: contains the vma, start, and and pfns arrays for the migration
2617 * Returns: negative errno on failures, 0 when 0 or more pages were migrated
2620 * Prepare to migrate a range of memory virtual address range by collecting all
2621 * the pages backing each virtual address in the range, saving them inside the
2622 * src array. Then lock those pages and unmap them. Once the pages are locked
2623 * and unmapped, check whether each page is pinned or not. Pages that aren't
2624 * pinned have the MIGRATE_PFN_MIGRATE flag set (by this function) in the
2625 * corresponding src array entry. Then restores any pages that are pinned, by
2626 * remapping and unlocking those pages.
2628 * The caller should then allocate destination memory and copy source memory to
2629 * it for all those entries (ie with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE
2630 * flag set). Once these are allocated and copied, the caller must update each
2631 * corresponding entry in the dst array with the pfn value of the destination
2632 * page and with the MIGRATE_PFN_VALID and MIGRATE_PFN_LOCKED flags set
2633 * (destination pages must have their struct pages locked, via lock_page()).
2635 * Note that the caller does not have to migrate all the pages that are marked
2636 * with MIGRATE_PFN_MIGRATE flag in src array unless this is a migration from
2637 * device memory to system memory. If the caller cannot migrate a device page
2638 * back to system memory, then it must return VM_FAULT_SIGBUS, which has severe
2639 * consequences for the userspace process, so it must be avoided if at all
2642 * For empty entries inside CPU page table (pte_none() or pmd_none() is true) we
2643 * do set MIGRATE_PFN_MIGRATE flag inside the corresponding source array thus
2644 * allowing the caller to allocate device memory for those unback virtual
2645 * address. For this the caller simply has to allocate device memory and
2646 * properly set the destination entry like for regular migration. Note that
2647 * this can still fails and thus inside the device driver must check if the
2648 * migration was successful for those entries after calling migrate_vma_pages()
2649 * just like for regular migration.
2651 * After that, the callers must call migrate_vma_pages() to go over each entry
2652 * in the src array that has the MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag
2653 * set. If the corresponding entry in dst array has MIGRATE_PFN_VALID flag set,
2654 * then migrate_vma_pages() to migrate struct page information from the source
2655 * struct page to the destination struct page. If it fails to migrate the
2656 * struct page information, then it clears the MIGRATE_PFN_MIGRATE flag in the
2659 * At this point all successfully migrated pages have an entry in the src
2660 * array with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag set and the dst
2661 * array entry with MIGRATE_PFN_VALID flag set.
2663 * Once migrate_vma_pages() returns the caller may inspect which pages were
2664 * successfully migrated, and which were not. Successfully migrated pages will
2665 * have the MIGRATE_PFN_MIGRATE flag set for their src array entry.
2667 * It is safe to update device page table after migrate_vma_pages() because
2668 * both destination and source page are still locked, and the mmap_sem is held
2669 * in read mode (hence no one can unmap the range being migrated).
2671 * Once the caller is done cleaning up things and updating its page table (if it
2672 * chose to do so, this is not an obligation) it finally calls
2673 * migrate_vma_finalize() to update the CPU page table to point to new pages
2674 * for successfully migrated pages or otherwise restore the CPU page table to
2675 * point to the original source pages.
2677 int migrate_vma_setup(struct migrate_vma *args)
2679 long nr_pages = (args->end - args->start) >> PAGE_SHIFT;
2681 args->start &= PAGE_MASK;
2682 args->end &= PAGE_MASK;
2683 if (!args->vma || is_vm_hugetlb_page(args->vma) ||
2684 (args->vma->vm_flags & VM_SPECIAL) || vma_is_dax(args->vma))
2688 if (args->start < args->vma->vm_start ||
2689 args->start >= args->vma->vm_end)
2691 if (args->end <= args->vma->vm_start || args->end > args->vma->vm_end)
2693 if (!args->src || !args->dst)
2696 memset(args->src, 0, sizeof(*args->src) * nr_pages);
2700 migrate_vma_collect(args);
2703 migrate_vma_prepare(args);
2705 migrate_vma_unmap(args);
2708 * At this point pages are locked and unmapped, and thus they have
2709 * stable content and can safely be copied to destination memory that
2710 * is allocated by the drivers.
2715 EXPORT_SYMBOL(migrate_vma_setup);
2718 * This code closely matches the code in:
2719 * __handle_mm_fault()
2720 * handle_pte_fault()
2721 * do_anonymous_page()
2722 * to map in an anonymous zero page but the struct page will be a ZONE_DEVICE
2725 static void migrate_vma_insert_page(struct migrate_vma *migrate,
2731 struct vm_area_struct *vma = migrate->vma;
2732 struct mm_struct *mm = vma->vm_mm;
2733 struct mem_cgroup *memcg;
2743 /* Only allow populating anonymous memory */
2744 if (!vma_is_anonymous(vma))
2747 pgdp = pgd_offset(mm, addr);
2748 p4dp = p4d_alloc(mm, pgdp, addr);
2751 pudp = pud_alloc(mm, p4dp, addr);
2754 pmdp = pmd_alloc(mm, pudp, addr);
2758 if (pmd_trans_huge(*pmdp) || pmd_devmap(*pmdp))
2762 * Use pte_alloc() instead of pte_alloc_map(). We can't run
2763 * pte_offset_map() on pmds where a huge pmd might be created
2764 * from a different thread.
2766 * pte_alloc_map() is safe to use under down_write(mmap_sem) or when
2767 * parallel threads are excluded by other means.
2769 * Here we only have down_read(mmap_sem).
2771 if (pte_alloc(mm, pmdp))
2774 /* See the comment in pte_alloc_one_map() */
2775 if (unlikely(pmd_trans_unstable(pmdp)))
2778 if (unlikely(anon_vma_prepare(vma)))
2780 if (mem_cgroup_try_charge(page, vma->vm_mm, GFP_KERNEL, &memcg, false))
2784 * The memory barrier inside __SetPageUptodate makes sure that
2785 * preceding stores to the page contents become visible before
2786 * the set_pte_at() write.
2788 __SetPageUptodate(page);
2790 if (is_zone_device_page(page)) {
2791 if (is_device_private_page(page)) {
2792 swp_entry_t swp_entry;
2794 swp_entry = make_device_private_entry(page, vma->vm_flags & VM_WRITE);
2795 entry = swp_entry_to_pte(swp_entry);
2798 entry = mk_pte(page, vma->vm_page_prot);
2799 if (vma->vm_flags & VM_WRITE)
2800 entry = pte_mkwrite(pte_mkdirty(entry));
2803 ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
2805 if (check_stable_address_space(mm))
2808 if (pte_present(*ptep)) {
2809 unsigned long pfn = pte_pfn(*ptep);
2811 if (!is_zero_pfn(pfn))
2814 } else if (!pte_none(*ptep))
2818 * Check for userfaultfd but do not deliver the fault. Instead,
2821 if (userfaultfd_missing(vma))
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 pte_unmap_unlock(ptep, ptl);
2848 mem_cgroup_cancel_charge(page, memcg, false);
2850 *src &= ~MIGRATE_PFN_MIGRATE;
2854 * migrate_vma_pages() - migrate meta-data from src page to dst page
2855 * @migrate: migrate struct containing all migration information
2857 * This migrates struct page meta-data from source struct page to destination
2858 * struct page. This effectively finishes the migration from source page to the
2861 void migrate_vma_pages(struct migrate_vma *migrate)
2863 const unsigned long npages = migrate->npages;
2864 const unsigned long start = migrate->start;
2865 struct mmu_notifier_range range;
2866 unsigned long addr, i;
2867 bool notified = false;
2869 for (i = 0, addr = start; i < npages; addr += PAGE_SIZE, i++) {
2870 struct page *newpage = migrate_pfn_to_page(migrate->dst[i]);
2871 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2872 struct address_space *mapping;
2876 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2881 if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE))
2886 mmu_notifier_range_init(&range,
2887 MMU_NOTIFY_CLEAR, 0,
2889 migrate->vma->vm_mm,
2890 addr, migrate->end);
2891 mmu_notifier_invalidate_range_start(&range);
2893 migrate_vma_insert_page(migrate, addr, newpage,
2899 mapping = page_mapping(page);
2901 if (is_zone_device_page(newpage)) {
2902 if (is_device_private_page(newpage)) {
2904 * For now only support private anonymous when
2905 * migrating to un-addressable device memory.
2908 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2913 * Other types of ZONE_DEVICE page are not
2916 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2921 r = migrate_page(mapping, newpage, page, MIGRATE_SYNC_NO_COPY);
2922 if (r != MIGRATEPAGE_SUCCESS)
2923 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2927 * No need to double call mmu_notifier->invalidate_range() callback as
2928 * the above ptep_clear_flush_notify() inside migrate_vma_insert_page()
2929 * did already call it.
2932 mmu_notifier_invalidate_range_only_end(&range);
2934 EXPORT_SYMBOL(migrate_vma_pages);
2937 * migrate_vma_finalize() - restore CPU page table entry
2938 * @migrate: migrate struct containing all migration information
2940 * This replaces the special migration pte entry with either a mapping to the
2941 * new page if migration was successful for that page, or to the original page
2944 * This also unlocks the pages and puts them back on the lru, or drops the extra
2945 * refcount, for device pages.
2947 void migrate_vma_finalize(struct migrate_vma *migrate)
2949 const unsigned long npages = migrate->npages;
2952 for (i = 0; i < npages; i++) {
2953 struct page *newpage = migrate_pfn_to_page(migrate->dst[i]);
2954 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2958 unlock_page(newpage);
2964 if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE) || !newpage) {
2966 unlock_page(newpage);
2972 remove_migration_ptes(page, newpage, false);
2976 if (is_zone_device_page(page))
2979 putback_lru_page(page);
2981 if (newpage != page) {
2982 unlock_page(newpage);
2983 if (is_zone_device_page(newpage))
2986 putback_lru_page(newpage);
2990 EXPORT_SYMBOL(migrate_vma_finalize);
2991 #endif /* CONFIG_DEVICE_PRIVATE */