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_hugetlb().
169 void putback_movable_pages(struct list_head *l)
174 list_for_each_entry_safe(page, page2, l, lru) {
175 if (unlikely(PageHuge(page))) {
176 putback_active_hugepage(page);
179 list_del(&page->lru);
181 * We isolated non-lru movable page so here we can use
182 * __PageMovable because LRU page's mapping cannot have
183 * PAGE_MAPPING_MOVABLE.
185 if (unlikely(__PageMovable(page))) {
186 VM_BUG_ON_PAGE(!PageIsolated(page), page);
188 if (PageMovable(page))
189 putback_movable_page(page);
191 __ClearPageIsolated(page);
195 mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON +
196 page_is_file_lru(page), -thp_nr_pages(page));
197 putback_lru_page(page);
203 * Restore a potential migration pte to a working pte entry
205 static bool remove_migration_pte(struct page *page, struct vm_area_struct *vma,
206 unsigned long addr, void *old)
208 struct page_vma_mapped_walk pvmw = {
212 .flags = PVMW_SYNC | PVMW_MIGRATION,
218 VM_BUG_ON_PAGE(PageTail(page), page);
219 while (page_vma_mapped_walk(&pvmw)) {
223 new = page - pvmw.page->index +
224 linear_page_index(vma, pvmw.address);
226 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
227 /* PMD-mapped THP migration entry */
229 VM_BUG_ON_PAGE(PageHuge(page) || !PageTransCompound(page), page);
230 remove_migration_pmd(&pvmw, new);
236 pte = pte_mkold(mk_pte(new, READ_ONCE(vma->vm_page_prot)));
237 if (pte_swp_soft_dirty(*pvmw.pte))
238 pte = pte_mksoft_dirty(pte);
241 * Recheck VMA as permissions can change since migration started
243 entry = pte_to_swp_entry(*pvmw.pte);
244 if (is_write_migration_entry(entry))
245 pte = maybe_mkwrite(pte, vma);
246 else if (pte_swp_uffd_wp(*pvmw.pte))
247 pte = pte_mkuffd_wp(pte);
249 if (unlikely(is_device_private_page(new))) {
250 entry = make_device_private_entry(new, pte_write(pte));
251 pte = swp_entry_to_pte(entry);
252 if (pte_swp_soft_dirty(*pvmw.pte))
253 pte = pte_swp_mksoft_dirty(pte);
254 if (pte_swp_uffd_wp(*pvmw.pte))
255 pte = pte_swp_mkuffd_wp(pte);
258 #ifdef CONFIG_HUGETLB_PAGE
260 pte = pte_mkhuge(pte);
261 pte = arch_make_huge_pte(pte, vma, new, 0);
262 set_huge_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte);
264 hugepage_add_anon_rmap(new, vma, pvmw.address);
266 page_dup_rmap(new, true);
270 set_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte);
273 page_add_anon_rmap(new, vma, pvmw.address, false);
275 page_add_file_rmap(new, false);
277 if (vma->vm_flags & VM_LOCKED && !PageTransCompound(new))
280 if (PageTransHuge(page) && PageMlocked(page))
281 clear_page_mlock(page);
283 /* No need to invalidate - it was non-present before */
284 update_mmu_cache(vma, pvmw.address, pvmw.pte);
291 * Get rid of all migration entries and replace them by
292 * references to the indicated page.
294 void remove_migration_ptes(struct page *old, struct page *new, bool locked)
296 struct rmap_walk_control rwc = {
297 .rmap_one = remove_migration_pte,
302 rmap_walk_locked(new, &rwc);
304 rmap_walk(new, &rwc);
308 * Something used the pte of a page under migration. We need to
309 * get to the page and wait until migration is finished.
310 * When we return from this function the fault will be retried.
312 void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
321 if (!is_swap_pte(pte))
324 entry = pte_to_swp_entry(pte);
325 if (!is_migration_entry(entry))
328 page = migration_entry_to_page(entry);
329 page = compound_head(page);
332 * Once page cache replacement of page migration started, page_count
333 * is zero; but we must not call put_and_wait_on_page_locked() without
334 * a ref. Use get_page_unless_zero(), and just fault again if it fails.
336 if (!get_page_unless_zero(page))
338 pte_unmap_unlock(ptep, ptl);
339 put_and_wait_on_page_locked(page);
342 pte_unmap_unlock(ptep, ptl);
345 void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
346 unsigned long address)
348 spinlock_t *ptl = pte_lockptr(mm, pmd);
349 pte_t *ptep = pte_offset_map(pmd, address);
350 __migration_entry_wait(mm, ptep, ptl);
353 void migration_entry_wait_huge(struct vm_area_struct *vma,
354 struct mm_struct *mm, pte_t *pte)
356 spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), mm, pte);
357 __migration_entry_wait(mm, pte, ptl);
360 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
361 void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd)
366 ptl = pmd_lock(mm, pmd);
367 if (!is_pmd_migration_entry(*pmd))
369 page = migration_entry_to_page(pmd_to_swp_entry(*pmd));
370 if (!get_page_unless_zero(page))
373 put_and_wait_on_page_locked(page);
380 static int expected_page_refs(struct address_space *mapping, struct page *page)
382 int expected_count = 1;
385 * Device private pages have an extra refcount as they are
388 expected_count += is_device_private_page(page);
390 expected_count += thp_nr_pages(page) + page_has_private(page);
392 return expected_count;
396 * Replace the page in the mapping.
398 * The number of remaining references must be:
399 * 1 for anonymous pages without a mapping
400 * 2 for pages with a mapping
401 * 3 for pages with a mapping and PagePrivate/PagePrivate2 set.
403 int migrate_page_move_mapping(struct address_space *mapping,
404 struct page *newpage, struct page *page, int extra_count)
406 XA_STATE(xas, &mapping->i_pages, page_index(page));
407 struct zone *oldzone, *newzone;
409 int expected_count = expected_page_refs(mapping, page) + extra_count;
410 int nr = thp_nr_pages(page);
413 /* Anonymous page without mapping */
414 if (page_count(page) != expected_count)
417 /* No turning back from here */
418 newpage->index = page->index;
419 newpage->mapping = page->mapping;
420 if (PageSwapBacked(page))
421 __SetPageSwapBacked(newpage);
423 return MIGRATEPAGE_SUCCESS;
426 oldzone = page_zone(page);
427 newzone = page_zone(newpage);
430 if (page_count(page) != expected_count || xas_load(&xas) != page) {
431 xas_unlock_irq(&xas);
435 if (!page_ref_freeze(page, expected_count)) {
436 xas_unlock_irq(&xas);
441 * Now we know that no one else is looking at the page:
442 * no turning back from here.
444 newpage->index = page->index;
445 newpage->mapping = page->mapping;
446 page_ref_add(newpage, nr); /* add cache reference */
447 if (PageSwapBacked(page)) {
448 __SetPageSwapBacked(newpage);
449 if (PageSwapCache(page)) {
452 SetPageSwapCache(newpage);
453 for (i = 0; i < (1 << compound_order(page)); i++)
454 set_page_private(newpage + i,
455 page_private(page + i));
458 VM_BUG_ON_PAGE(PageSwapCache(page), page);
461 /* Move dirty while page refs frozen and newpage not yet exposed */
462 dirty = PageDirty(page);
464 ClearPageDirty(page);
465 SetPageDirty(newpage);
468 xas_store(&xas, newpage);
469 if (PageTransHuge(page)) {
472 for (i = 1; i < nr; i++) {
474 xas_store(&xas, newpage);
479 * Drop cache reference from old page by unfreezing
480 * to one less reference.
481 * We know this isn't the last reference.
483 page_ref_unfreeze(page, expected_count - nr);
486 /* Leave irq disabled to prevent preemption while updating stats */
489 * If moved to a different zone then also account
490 * the page for that zone. Other VM counters will be
491 * taken care of when we establish references to the
492 * new page and drop references to the old page.
494 * Note that anonymous pages are accounted for
495 * via NR_FILE_PAGES and NR_ANON_MAPPED if they
496 * are mapped to swap space.
498 if (newzone != oldzone) {
499 struct lruvec *old_lruvec, *new_lruvec;
500 struct mem_cgroup *memcg;
502 memcg = page_memcg(page);
503 old_lruvec = mem_cgroup_lruvec(memcg, oldzone->zone_pgdat);
504 new_lruvec = mem_cgroup_lruvec(memcg, newzone->zone_pgdat);
506 __mod_lruvec_state(old_lruvec, NR_FILE_PAGES, -nr);
507 __mod_lruvec_state(new_lruvec, NR_FILE_PAGES, nr);
508 if (PageSwapBacked(page) && !PageSwapCache(page)) {
509 __mod_lruvec_state(old_lruvec, NR_SHMEM, -nr);
510 __mod_lruvec_state(new_lruvec, NR_SHMEM, nr);
512 if (dirty && mapping_can_writeback(mapping)) {
513 __mod_lruvec_state(old_lruvec, NR_FILE_DIRTY, -nr);
514 __mod_zone_page_state(oldzone, NR_ZONE_WRITE_PENDING, -nr);
515 __mod_lruvec_state(new_lruvec, NR_FILE_DIRTY, nr);
516 __mod_zone_page_state(newzone, NR_ZONE_WRITE_PENDING, nr);
521 return MIGRATEPAGE_SUCCESS;
523 EXPORT_SYMBOL(migrate_page_move_mapping);
526 * The expected number of remaining references is the same as that
527 * of migrate_page_move_mapping().
529 int migrate_huge_page_move_mapping(struct address_space *mapping,
530 struct page *newpage, struct page *page)
532 XA_STATE(xas, &mapping->i_pages, page_index(page));
536 expected_count = 2 + page_has_private(page);
537 if (page_count(page) != expected_count || xas_load(&xas) != page) {
538 xas_unlock_irq(&xas);
542 if (!page_ref_freeze(page, expected_count)) {
543 xas_unlock_irq(&xas);
547 newpage->index = page->index;
548 newpage->mapping = page->mapping;
552 xas_store(&xas, newpage);
554 page_ref_unfreeze(page, expected_count - 1);
556 xas_unlock_irq(&xas);
558 return MIGRATEPAGE_SUCCESS;
562 * Gigantic pages are so large that we do not guarantee that page++ pointer
563 * arithmetic will work across the entire page. We need something more
566 static void __copy_gigantic_page(struct page *dst, struct page *src,
570 struct page *dst_base = dst;
571 struct page *src_base = src;
573 for (i = 0; i < nr_pages; ) {
575 copy_highpage(dst, src);
578 dst = mem_map_next(dst, dst_base, i);
579 src = mem_map_next(src, src_base, i);
583 static void copy_huge_page(struct page *dst, struct page *src)
590 struct hstate *h = page_hstate(src);
591 nr_pages = pages_per_huge_page(h);
593 if (unlikely(nr_pages > MAX_ORDER_NR_PAGES)) {
594 __copy_gigantic_page(dst, src, nr_pages);
599 BUG_ON(!PageTransHuge(src));
600 nr_pages = thp_nr_pages(src);
603 for (i = 0; i < nr_pages; i++) {
605 copy_highpage(dst + i, src + i);
610 * Copy the page to its new location
612 void migrate_page_states(struct page *newpage, struct page *page)
617 SetPageError(newpage);
618 if (PageReferenced(page))
619 SetPageReferenced(newpage);
620 if (PageUptodate(page))
621 SetPageUptodate(newpage);
622 if (TestClearPageActive(page)) {
623 VM_BUG_ON_PAGE(PageUnevictable(page), page);
624 SetPageActive(newpage);
625 } else if (TestClearPageUnevictable(page))
626 SetPageUnevictable(newpage);
627 if (PageWorkingset(page))
628 SetPageWorkingset(newpage);
629 if (PageChecked(page))
630 SetPageChecked(newpage);
631 if (PageMappedToDisk(page))
632 SetPageMappedToDisk(newpage);
634 /* Move dirty on pages not done by migrate_page_move_mapping() */
636 SetPageDirty(newpage);
638 if (page_is_young(page))
639 set_page_young(newpage);
640 if (page_is_idle(page))
641 set_page_idle(newpage);
644 * Copy NUMA information to the new page, to prevent over-eager
645 * future migrations of this same page.
647 cpupid = page_cpupid_xchg_last(page, -1);
648 page_cpupid_xchg_last(newpage, cpupid);
650 ksm_migrate_page(newpage, page);
652 * Please do not reorder this without considering how mm/ksm.c's
653 * get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache().
655 if (PageSwapCache(page))
656 ClearPageSwapCache(page);
657 ClearPagePrivate(page);
658 set_page_private(page, 0);
661 * If any waiters have accumulated on the new page then
664 if (PageWriteback(newpage))
665 end_page_writeback(newpage);
668 * PG_readahead shares the same bit with PG_reclaim. The above
669 * end_page_writeback() may clear PG_readahead mistakenly, so set the
672 if (PageReadahead(page))
673 SetPageReadahead(newpage);
675 copy_page_owner(page, newpage);
678 mem_cgroup_migrate(page, newpage);
680 EXPORT_SYMBOL(migrate_page_states);
682 void migrate_page_copy(struct page *newpage, struct page *page)
684 if (PageHuge(page) || PageTransHuge(page))
685 copy_huge_page(newpage, page);
687 copy_highpage(newpage, page);
689 migrate_page_states(newpage, page);
691 EXPORT_SYMBOL(migrate_page_copy);
693 /************************************************************
694 * Migration functions
695 ***********************************************************/
698 * Common logic to directly migrate a single LRU page suitable for
699 * pages that do not use PagePrivate/PagePrivate2.
701 * Pages are locked upon entry and exit.
703 int migrate_page(struct address_space *mapping,
704 struct page *newpage, struct page *page,
705 enum migrate_mode mode)
709 BUG_ON(PageWriteback(page)); /* Writeback must be complete */
711 rc = migrate_page_move_mapping(mapping, newpage, page, 0);
713 if (rc != MIGRATEPAGE_SUCCESS)
716 if (mode != MIGRATE_SYNC_NO_COPY)
717 migrate_page_copy(newpage, page);
719 migrate_page_states(newpage, page);
720 return MIGRATEPAGE_SUCCESS;
722 EXPORT_SYMBOL(migrate_page);
725 /* Returns true if all buffers are successfully locked */
726 static bool buffer_migrate_lock_buffers(struct buffer_head *head,
727 enum migrate_mode mode)
729 struct buffer_head *bh = head;
731 /* Simple case, sync compaction */
732 if (mode != MIGRATE_ASYNC) {
735 bh = bh->b_this_page;
737 } while (bh != head);
742 /* async case, we cannot block on lock_buffer so use trylock_buffer */
744 if (!trylock_buffer(bh)) {
746 * We failed to lock the buffer and cannot stall in
747 * async migration. Release the taken locks
749 struct buffer_head *failed_bh = bh;
751 while (bh != failed_bh) {
753 bh = bh->b_this_page;
758 bh = bh->b_this_page;
759 } while (bh != head);
763 static int __buffer_migrate_page(struct address_space *mapping,
764 struct page *newpage, struct page *page, enum migrate_mode mode,
767 struct buffer_head *bh, *head;
771 if (!page_has_buffers(page))
772 return migrate_page(mapping, newpage, page, mode);
774 /* Check whether page does not have extra refs before we do more work */
775 expected_count = expected_page_refs(mapping, page);
776 if (page_count(page) != expected_count)
779 head = page_buffers(page);
780 if (!buffer_migrate_lock_buffers(head, mode))
785 bool invalidated = false;
789 spin_lock(&mapping->private_lock);
792 if (atomic_read(&bh->b_count)) {
796 bh = bh->b_this_page;
797 } while (bh != head);
803 spin_unlock(&mapping->private_lock);
804 invalidate_bh_lrus();
806 goto recheck_buffers;
810 rc = migrate_page_move_mapping(mapping, newpage, page, 0);
811 if (rc != MIGRATEPAGE_SUCCESS)
814 attach_page_private(newpage, detach_page_private(page));
818 set_bh_page(bh, newpage, bh_offset(bh));
819 bh = bh->b_this_page;
821 } while (bh != head);
823 if (mode != MIGRATE_SYNC_NO_COPY)
824 migrate_page_copy(newpage, page);
826 migrate_page_states(newpage, page);
828 rc = MIGRATEPAGE_SUCCESS;
831 spin_unlock(&mapping->private_lock);
835 bh = bh->b_this_page;
837 } while (bh != head);
843 * Migration function for pages with buffers. This function can only be used
844 * if the underlying filesystem guarantees that no other references to "page"
845 * exist. For example attached buffer heads are accessed only under page lock.
847 int buffer_migrate_page(struct address_space *mapping,
848 struct page *newpage, struct page *page, enum migrate_mode mode)
850 return __buffer_migrate_page(mapping, newpage, page, mode, false);
852 EXPORT_SYMBOL(buffer_migrate_page);
855 * Same as above except that this variant is more careful and checks that there
856 * are also no buffer head references. This function is the right one for
857 * mappings where buffer heads are directly looked up and referenced (such as
858 * block device mappings).
860 int buffer_migrate_page_norefs(struct address_space *mapping,
861 struct page *newpage, struct page *page, enum migrate_mode mode)
863 return __buffer_migrate_page(mapping, newpage, page, mode, true);
868 * Writeback a page to clean the dirty state
870 static int writeout(struct address_space *mapping, struct page *page)
872 struct writeback_control wbc = {
873 .sync_mode = WB_SYNC_NONE,
876 .range_end = LLONG_MAX,
881 if (!mapping->a_ops->writepage)
882 /* No write method for the address space */
885 if (!clear_page_dirty_for_io(page))
886 /* Someone else already triggered a write */
890 * A dirty page may imply that the underlying filesystem has
891 * the page on some queue. So the page must be clean for
892 * migration. Writeout may mean we loose the lock and the
893 * page state is no longer what we checked for earlier.
894 * At this point we know that the migration attempt cannot
897 remove_migration_ptes(page, page, false);
899 rc = mapping->a_ops->writepage(page, &wbc);
901 if (rc != AOP_WRITEPAGE_ACTIVATE)
902 /* unlocked. Relock */
905 return (rc < 0) ? -EIO : -EAGAIN;
909 * Default handling if a filesystem does not provide a migration function.
911 static int fallback_migrate_page(struct address_space *mapping,
912 struct page *newpage, struct page *page, enum migrate_mode mode)
914 if (PageDirty(page)) {
915 /* Only writeback pages in full synchronous migration */
918 case MIGRATE_SYNC_NO_COPY:
923 return writeout(mapping, page);
927 * Buffers may be managed in a filesystem specific way.
928 * We must have no buffers or drop them.
930 if (page_has_private(page) &&
931 !try_to_release_page(page, GFP_KERNEL))
932 return mode == MIGRATE_SYNC ? -EAGAIN : -EBUSY;
934 return migrate_page(mapping, newpage, page, mode);
938 * Move a page to a newly allocated page
939 * The page is locked and all ptes have been successfully removed.
941 * The new page will have replaced the old page if this function
946 * MIGRATEPAGE_SUCCESS - success
948 static int move_to_new_page(struct page *newpage, struct page *page,
949 enum migrate_mode mode)
951 struct address_space *mapping;
953 bool is_lru = !__PageMovable(page);
955 VM_BUG_ON_PAGE(!PageLocked(page), page);
956 VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
958 mapping = page_mapping(page);
960 if (likely(is_lru)) {
962 rc = migrate_page(mapping, newpage, page, mode);
963 else if (mapping->a_ops->migratepage)
965 * Most pages have a mapping and most filesystems
966 * provide a migratepage callback. Anonymous pages
967 * are part of swap space which also has its own
968 * migratepage callback. This is the most common path
969 * for page migration.
971 rc = mapping->a_ops->migratepage(mapping, newpage,
974 rc = fallback_migrate_page(mapping, newpage,
978 * In case of non-lru page, it could be released after
979 * isolation step. In that case, we shouldn't try migration.
981 VM_BUG_ON_PAGE(!PageIsolated(page), page);
982 if (!PageMovable(page)) {
983 rc = MIGRATEPAGE_SUCCESS;
984 __ClearPageIsolated(page);
988 rc = mapping->a_ops->migratepage(mapping, newpage,
990 WARN_ON_ONCE(rc == MIGRATEPAGE_SUCCESS &&
991 !PageIsolated(page));
995 * When successful, old pagecache page->mapping must be cleared before
996 * page is freed; but stats require that PageAnon be left as PageAnon.
998 if (rc == MIGRATEPAGE_SUCCESS) {
999 if (__PageMovable(page)) {
1000 VM_BUG_ON_PAGE(!PageIsolated(page), page);
1003 * We clear PG_movable under page_lock so any compactor
1004 * cannot try to migrate this page.
1006 __ClearPageIsolated(page);
1010 * Anonymous and movable page->mapping will be cleared by
1011 * free_pages_prepare so don't reset it here for keeping
1012 * the type to work PageAnon, for example.
1014 if (!PageMappingFlags(page))
1015 page->mapping = NULL;
1017 if (likely(!is_zone_device_page(newpage))) {
1018 int i, nr = compound_nr(newpage);
1020 for (i = 0; i < nr; i++)
1021 flush_dcache_page(newpage + i);
1028 static int __unmap_and_move(struct page *page, struct page *newpage,
1029 int force, enum migrate_mode mode)
1032 int page_was_mapped = 0;
1033 struct anon_vma *anon_vma = NULL;
1034 bool is_lru = !__PageMovable(page);
1036 if (!trylock_page(page)) {
1037 if (!force || mode == MIGRATE_ASYNC)
1041 * It's not safe for direct compaction to call lock_page.
1042 * For example, during page readahead pages are added locked
1043 * to the LRU. Later, when the IO completes the pages are
1044 * marked uptodate and unlocked. However, the queueing
1045 * could be merging multiple pages for one bio (e.g.
1046 * mpage_readahead). If an allocation happens for the
1047 * second or third page, the process can end up locking
1048 * the same page twice and deadlocking. Rather than
1049 * trying to be clever about what pages can be locked,
1050 * avoid the use of lock_page for direct compaction
1053 if (current->flags & PF_MEMALLOC)
1059 if (PageWriteback(page)) {
1061 * Only in the case of a full synchronous migration is it
1062 * necessary to wait for PageWriteback. In the async case,
1063 * the retry loop is too short and in the sync-light case,
1064 * the overhead of stalling is too much
1068 case MIGRATE_SYNC_NO_COPY:
1076 wait_on_page_writeback(page);
1080 * By try_to_unmap(), page->mapcount goes down to 0 here. In this case,
1081 * we cannot notice that anon_vma is freed while we migrates a page.
1082 * This get_anon_vma() delays freeing anon_vma pointer until the end
1083 * of migration. File cache pages are no problem because of page_lock()
1084 * File Caches may use write_page() or lock_page() in migration, then,
1085 * just care Anon page here.
1087 * Only page_get_anon_vma() understands the subtleties of
1088 * getting a hold on an anon_vma from outside one of its mms.
1089 * But if we cannot get anon_vma, then we won't need it anyway,
1090 * because that implies that the anon page is no longer mapped
1091 * (and cannot be remapped so long as we hold the page lock).
1093 if (PageAnon(page) && !PageKsm(page))
1094 anon_vma = page_get_anon_vma(page);
1097 * Block others from accessing the new page when we get around to
1098 * establishing additional references. We are usually the only one
1099 * holding a reference to newpage at this point. We used to have a BUG
1100 * here if trylock_page(newpage) fails, but would like to allow for
1101 * cases where there might be a race with the previous use of newpage.
1102 * This is much like races on refcount of oldpage: just don't BUG().
1104 if (unlikely(!trylock_page(newpage)))
1107 if (unlikely(!is_lru)) {
1108 rc = move_to_new_page(newpage, page, mode);
1109 goto out_unlock_both;
1113 * Corner case handling:
1114 * 1. When a new swap-cache page is read into, it is added to the LRU
1115 * and treated as swapcache but it has no rmap yet.
1116 * Calling try_to_unmap() against a page->mapping==NULL page will
1117 * trigger a BUG. So handle it here.
1118 * 2. An orphaned page (see truncate_complete_page) might have
1119 * fs-private metadata. The page can be picked up due to memory
1120 * offlining. Everywhere else except page reclaim, the page is
1121 * invisible to the vm, so the page can not be migrated. So try to
1122 * free the metadata, so the page can be freed.
1124 if (!page->mapping) {
1125 VM_BUG_ON_PAGE(PageAnon(page), page);
1126 if (page_has_private(page)) {
1127 try_to_free_buffers(page);
1128 goto out_unlock_both;
1130 } else if (page_mapped(page)) {
1131 /* Establish migration ptes */
1132 VM_BUG_ON_PAGE(PageAnon(page) && !PageKsm(page) && !anon_vma,
1134 try_to_unmap(page, TTU_MIGRATION|TTU_IGNORE_MLOCK);
1135 page_was_mapped = 1;
1138 if (!page_mapped(page))
1139 rc = move_to_new_page(newpage, page, mode);
1141 if (page_was_mapped)
1142 remove_migration_ptes(page,
1143 rc == MIGRATEPAGE_SUCCESS ? newpage : page, false);
1146 unlock_page(newpage);
1148 /* Drop an anon_vma reference if we took one */
1150 put_anon_vma(anon_vma);
1154 * If migration is successful, decrease refcount of the newpage
1155 * which will not free the page because new page owner increased
1156 * refcounter. As well, if it is LRU page, add the page to LRU
1157 * list in here. Use the old state of the isolated source page to
1158 * determine if we migrated a LRU page. newpage was already unlocked
1159 * and possibly modified by its owner - don't rely on the page
1162 if (rc == MIGRATEPAGE_SUCCESS) {
1163 if (unlikely(!is_lru))
1166 putback_lru_page(newpage);
1173 * Obtain the lock on page, remove all ptes and migrate the page
1174 * to the newly allocated page in newpage.
1176 static int unmap_and_move(new_page_t get_new_page,
1177 free_page_t put_new_page,
1178 unsigned long private, struct page *page,
1179 int force, enum migrate_mode mode,
1180 enum migrate_reason reason)
1182 int rc = MIGRATEPAGE_SUCCESS;
1183 struct page *newpage = NULL;
1185 if (!thp_migration_supported() && PageTransHuge(page))
1188 if (page_count(page) == 1) {
1189 /* page was freed from under us. So we are done. */
1190 ClearPageActive(page);
1191 ClearPageUnevictable(page);
1192 if (unlikely(__PageMovable(page))) {
1194 if (!PageMovable(page))
1195 __ClearPageIsolated(page);
1201 newpage = get_new_page(page, private);
1205 rc = __unmap_and_move(page, newpage, force, mode);
1206 if (rc == MIGRATEPAGE_SUCCESS)
1207 set_page_owner_migrate_reason(newpage, reason);
1210 if (rc != -EAGAIN) {
1212 * A page that has been migrated has all references
1213 * removed and will be freed. A page that has not been
1214 * migrated will have kept its references and be restored.
1216 list_del(&page->lru);
1219 * Compaction can migrate also non-LRU pages which are
1220 * not accounted to NR_ISOLATED_*. They can be recognized
1223 if (likely(!__PageMovable(page)))
1224 mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON +
1225 page_is_file_lru(page), -thp_nr_pages(page));
1229 * If migration is successful, releases reference grabbed during
1230 * isolation. Otherwise, restore the page to right list unless
1233 if (rc == MIGRATEPAGE_SUCCESS) {
1234 if (reason != MR_MEMORY_FAILURE)
1236 * We release the page in page_handle_poison.
1240 if (rc != -EAGAIN) {
1241 if (likely(!__PageMovable(page))) {
1242 putback_lru_page(page);
1247 if (PageMovable(page))
1248 putback_movable_page(page);
1250 __ClearPageIsolated(page);
1256 put_new_page(newpage, private);
1265 * Counterpart of unmap_and_move_page() for hugepage migration.
1267 * This function doesn't wait the completion of hugepage I/O
1268 * because there is no race between I/O and migration for hugepage.
1269 * Note that currently hugepage I/O occurs only in direct I/O
1270 * where no lock is held and PG_writeback is irrelevant,
1271 * and writeback status of all subpages are counted in the reference
1272 * count of the head page (i.e. if all subpages of a 2MB hugepage are
1273 * under direct I/O, the reference of the head page is 512 and a bit more.)
1274 * This means that when we try to migrate hugepage whose subpages are
1275 * doing direct I/O, some references remain after try_to_unmap() and
1276 * hugepage migration fails without data corruption.
1278 * There is also no race when direct I/O is issued on the page under migration,
1279 * because then pte is replaced with migration swap entry and direct I/O code
1280 * will wait in the page fault for migration to complete.
1282 static int unmap_and_move_huge_page(new_page_t get_new_page,
1283 free_page_t put_new_page, unsigned long private,
1284 struct page *hpage, int force,
1285 enum migrate_mode mode, int reason)
1288 int page_was_mapped = 0;
1289 struct page *new_hpage;
1290 struct anon_vma *anon_vma = NULL;
1291 struct address_space *mapping = NULL;
1294 * Migratability of hugepages depends on architectures and their size.
1295 * This check is necessary because some callers of hugepage migration
1296 * like soft offline and memory hotremove don't walk through page
1297 * tables or check whether the hugepage is pmd-based or not before
1298 * kicking migration.
1300 if (!hugepage_migration_supported(page_hstate(hpage))) {
1301 putback_active_hugepage(hpage);
1305 new_hpage = get_new_page(hpage, private);
1309 if (!trylock_page(hpage)) {
1314 case MIGRATE_SYNC_NO_COPY:
1323 * Check for pages which are in the process of being freed. Without
1324 * page_mapping() set, hugetlbfs specific move page routine will not
1325 * be called and we could leak usage counts for subpools.
1327 if (page_private(hpage) && !page_mapping(hpage)) {
1332 if (PageAnon(hpage))
1333 anon_vma = page_get_anon_vma(hpage);
1335 if (unlikely(!trylock_page(new_hpage)))
1338 if (page_mapped(hpage)) {
1339 bool mapping_locked = false;
1340 enum ttu_flags ttu = TTU_MIGRATION|TTU_IGNORE_MLOCK;
1342 if (!PageAnon(hpage)) {
1344 * In shared mappings, try_to_unmap could potentially
1345 * call huge_pmd_unshare. Because of this, take
1346 * semaphore in write mode here and set TTU_RMAP_LOCKED
1347 * to let lower levels know we have taken the lock.
1349 mapping = hugetlb_page_mapping_lock_write(hpage);
1350 if (unlikely(!mapping))
1351 goto unlock_put_anon;
1353 mapping_locked = true;
1354 ttu |= TTU_RMAP_LOCKED;
1357 try_to_unmap(hpage, ttu);
1358 page_was_mapped = 1;
1361 i_mmap_unlock_write(mapping);
1364 if (!page_mapped(hpage))
1365 rc = move_to_new_page(new_hpage, hpage, mode);
1367 if (page_was_mapped)
1368 remove_migration_ptes(hpage,
1369 rc == MIGRATEPAGE_SUCCESS ? new_hpage : hpage, false);
1372 unlock_page(new_hpage);
1376 put_anon_vma(anon_vma);
1378 if (rc == MIGRATEPAGE_SUCCESS) {
1379 move_hugetlb_state(hpage, new_hpage, reason);
1380 put_new_page = NULL;
1387 putback_active_hugepage(hpage);
1390 * If migration was not successful and there's a freeing callback, use
1391 * it. Otherwise, put_page() will drop the reference grabbed during
1395 put_new_page(new_hpage, private);
1397 putback_active_hugepage(new_hpage);
1403 * migrate_pages - migrate the pages specified in a list, to the free pages
1404 * supplied as the target for the page migration
1406 * @from: The list of pages to be migrated.
1407 * @get_new_page: The function used to allocate free pages to be used
1408 * as the target of the page migration.
1409 * @put_new_page: The function used to free target pages if migration
1410 * fails, or NULL if no special handling is necessary.
1411 * @private: Private data to be passed on to get_new_page()
1412 * @mode: The migration mode that specifies the constraints for
1413 * page migration, if any.
1414 * @reason: The reason for page migration.
1416 * The function returns after 10 attempts or if no pages are movable any more
1417 * because the list has become empty or no retryable pages exist any more.
1418 * The caller should call putback_movable_pages() to return pages to the LRU
1419 * or free list only if ret != 0.
1421 * Returns the number of pages that were not migrated, or an error code.
1423 int migrate_pages(struct list_head *from, new_page_t get_new_page,
1424 free_page_t put_new_page, unsigned long private,
1425 enum migrate_mode mode, int reason)
1430 int nr_succeeded = 0;
1431 int nr_thp_succeeded = 0;
1432 int nr_thp_failed = 0;
1433 int nr_thp_split = 0;
1435 bool is_thp = false;
1438 int swapwrite = current->flags & PF_SWAPWRITE;
1439 int rc, nr_subpages;
1442 current->flags |= PF_SWAPWRITE;
1444 for (pass = 0; pass < 10 && (retry || thp_retry); pass++) {
1448 list_for_each_entry_safe(page, page2, from, lru) {
1451 * THP statistics is based on the source huge page.
1452 * Capture required information that might get lost
1455 is_thp = PageTransHuge(page) && !PageHuge(page);
1456 nr_subpages = thp_nr_pages(page);
1460 rc = unmap_and_move_huge_page(get_new_page,
1461 put_new_page, private, page,
1462 pass > 2, mode, reason);
1464 rc = unmap_and_move(get_new_page, put_new_page,
1465 private, page, pass > 2, mode,
1471 * THP migration might be unsupported or the
1472 * allocation could've failed so we should
1473 * retry on the same page with the THP split
1476 * Head page is retried immediately and tail
1477 * pages are added to the tail of the list so
1478 * we encounter them after the rest of the list
1483 rc = split_huge_page_to_list(page, from);
1486 list_safe_reset_next(page, page2, lru);
1492 nr_failed += nr_subpages;
1504 case MIGRATEPAGE_SUCCESS:
1507 nr_succeeded += nr_subpages;
1514 * Permanent failure (-EBUSY, -ENOSYS, etc.):
1515 * unlike -EAGAIN case, the failed page is
1516 * removed from migration page list and not
1517 * retried in the next outer loop.
1521 nr_failed += nr_subpages;
1529 nr_failed += retry + thp_retry;
1530 nr_thp_failed += thp_retry;
1533 count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded);
1534 count_vm_events(PGMIGRATE_FAIL, nr_failed);
1535 count_vm_events(THP_MIGRATION_SUCCESS, nr_thp_succeeded);
1536 count_vm_events(THP_MIGRATION_FAIL, nr_thp_failed);
1537 count_vm_events(THP_MIGRATION_SPLIT, nr_thp_split);
1538 trace_mm_migrate_pages(nr_succeeded, nr_failed, nr_thp_succeeded,
1539 nr_thp_failed, nr_thp_split, mode, reason);
1542 current->flags &= ~PF_SWAPWRITE;
1547 struct page *alloc_migration_target(struct page *page, unsigned long private)
1549 struct migration_target_control *mtc;
1551 unsigned int order = 0;
1552 struct page *new_page = NULL;
1556 mtc = (struct migration_target_control *)private;
1557 gfp_mask = mtc->gfp_mask;
1559 if (nid == NUMA_NO_NODE)
1560 nid = page_to_nid(page);
1562 if (PageHuge(page)) {
1563 struct hstate *h = page_hstate(compound_head(page));
1565 gfp_mask = htlb_modify_alloc_mask(h, gfp_mask);
1566 return alloc_huge_page_nodemask(h, nid, mtc->nmask, gfp_mask);
1569 if (PageTransHuge(page)) {
1571 * clear __GFP_RECLAIM to make the migration callback
1572 * consistent with regular THP allocations.
1574 gfp_mask &= ~__GFP_RECLAIM;
1575 gfp_mask |= GFP_TRANSHUGE;
1576 order = HPAGE_PMD_ORDER;
1578 zidx = zone_idx(page_zone(page));
1579 if (is_highmem_idx(zidx) || zidx == ZONE_MOVABLE)
1580 gfp_mask |= __GFP_HIGHMEM;
1582 new_page = __alloc_pages_nodemask(gfp_mask, order, nid, mtc->nmask);
1584 if (new_page && PageTransHuge(new_page))
1585 prep_transhuge_page(new_page);
1592 static int store_status(int __user *status, int start, int value, int nr)
1595 if (put_user(value, status + start))
1603 static int do_move_pages_to_node(struct mm_struct *mm,
1604 struct list_head *pagelist, int node)
1607 struct migration_target_control mtc = {
1609 .gfp_mask = GFP_HIGHUSER_MOVABLE | __GFP_THISNODE,
1612 err = migrate_pages(pagelist, alloc_migration_target, NULL,
1613 (unsigned long)&mtc, MIGRATE_SYNC, MR_SYSCALL);
1615 putback_movable_pages(pagelist);
1620 * Resolves the given address to a struct page, isolates it from the LRU and
1621 * puts it to the given pagelist.
1623 * errno - if the page cannot be found/isolated
1624 * 0 - when it doesn't have to be migrated because it is already on the
1626 * 1 - when it has been queued
1628 static int add_page_for_migration(struct mm_struct *mm, unsigned long addr,
1629 int node, struct list_head *pagelist, bool migrate_all)
1631 struct vm_area_struct *vma;
1633 unsigned int follflags;
1638 vma = find_vma(mm, addr);
1639 if (!vma || addr < vma->vm_start || !vma_migratable(vma))
1642 /* FOLL_DUMP to ignore special (like zero) pages */
1643 follflags = FOLL_GET | FOLL_DUMP;
1644 page = follow_page(vma, addr, follflags);
1646 err = PTR_ERR(page);
1655 if (page_to_nid(page) == node)
1659 if (page_mapcount(page) > 1 && !migrate_all)
1662 if (PageHuge(page)) {
1663 if (PageHead(page)) {
1664 err = isolate_hugetlb(page, pagelist);
1671 head = compound_head(page);
1672 err = isolate_lru_page(head);
1677 list_add_tail(&head->lru, pagelist);
1678 mod_node_page_state(page_pgdat(head),
1679 NR_ISOLATED_ANON + page_is_file_lru(head),
1680 thp_nr_pages(head));
1684 * Either remove the duplicate refcount from
1685 * isolate_lru_page() or drop the page ref if it was
1690 mmap_read_unlock(mm);
1694 static int move_pages_and_store_status(struct mm_struct *mm, int node,
1695 struct list_head *pagelist, int __user *status,
1696 int start, int i, unsigned long nr_pages)
1700 if (list_empty(pagelist))
1703 err = do_move_pages_to_node(mm, pagelist, node);
1706 * Positive err means the number of failed
1707 * pages to migrate. Since we are going to
1708 * abort and return the number of non-migrated
1709 * pages, so need to incude the rest of the
1710 * nr_pages that have not been attempted as
1714 err += nr_pages - i - 1;
1717 return store_status(status, start, node, i - start);
1721 * Migrate an array of page address onto an array of nodes and fill
1722 * the corresponding array of status.
1724 static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
1725 unsigned long nr_pages,
1726 const void __user * __user *pages,
1727 const int __user *nodes,
1728 int __user *status, int flags)
1730 int current_node = NUMA_NO_NODE;
1731 LIST_HEAD(pagelist);
1737 for (i = start = 0; i < nr_pages; i++) {
1738 const void __user *p;
1743 if (get_user(p, pages + i))
1745 if (get_user(node, nodes + i))
1747 addr = (unsigned long)untagged_addr(p);
1750 if (node < 0 || node >= MAX_NUMNODES)
1752 if (!node_state(node, N_MEMORY))
1756 if (!node_isset(node, task_nodes))
1759 if (current_node == NUMA_NO_NODE) {
1760 current_node = node;
1762 } else if (node != current_node) {
1763 err = move_pages_and_store_status(mm, current_node,
1764 &pagelist, status, start, i, nr_pages);
1768 current_node = node;
1772 * Errors in the page lookup or isolation are not fatal and we simply
1773 * report them via status
1775 err = add_page_for_migration(mm, addr, current_node,
1776 &pagelist, flags & MPOL_MF_MOVE_ALL);
1779 /* The page is successfully queued for migration */
1784 * If the page is already on the target node (!err), store the
1785 * node, otherwise, store the err.
1787 err = store_status(status, i, err ? : current_node, 1);
1791 err = move_pages_and_store_status(mm, current_node, &pagelist,
1792 status, start, i, nr_pages);
1795 current_node = NUMA_NO_NODE;
1798 /* Make sure we do not overwrite the existing error */
1799 err1 = move_pages_and_store_status(mm, current_node, &pagelist,
1800 status, start, i, nr_pages);
1808 * Determine the nodes of an array of pages and store it in an array of status.
1810 static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
1811 const void __user **pages, int *status)
1817 for (i = 0; i < nr_pages; i++) {
1818 unsigned long addr = (unsigned long)(*pages);
1819 struct vm_area_struct *vma;
1823 vma = find_vma(mm, addr);
1824 if (!vma || addr < vma->vm_start)
1827 /* FOLL_DUMP to ignore special (like zero) pages */
1828 page = follow_page(vma, addr, FOLL_DUMP);
1830 err = PTR_ERR(page);
1834 err = page ? page_to_nid(page) : -ENOENT;
1842 mmap_read_unlock(mm);
1846 * Determine the nodes of a user array of pages and store it in
1847 * a user array of status.
1849 static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
1850 const void __user * __user *pages,
1853 #define DO_PAGES_STAT_CHUNK_NR 16
1854 const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR];
1855 int chunk_status[DO_PAGES_STAT_CHUNK_NR];
1858 unsigned long chunk_nr;
1860 chunk_nr = nr_pages;
1861 if (chunk_nr > DO_PAGES_STAT_CHUNK_NR)
1862 chunk_nr = DO_PAGES_STAT_CHUNK_NR;
1864 if (copy_from_user(chunk_pages, pages, chunk_nr * sizeof(*chunk_pages)))
1867 do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status);
1869 if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status)))
1874 nr_pages -= chunk_nr;
1876 return nr_pages ? -EFAULT : 0;
1879 static struct mm_struct *find_mm_struct(pid_t pid, nodemask_t *mem_nodes)
1881 struct task_struct *task;
1882 struct mm_struct *mm;
1885 * There is no need to check if current process has the right to modify
1886 * the specified process when they are same.
1890 *mem_nodes = cpuset_mems_allowed(current);
1894 /* Find the mm_struct */
1896 task = find_task_by_vpid(pid);
1899 return ERR_PTR(-ESRCH);
1901 get_task_struct(task);
1904 * Check if this process has the right to modify the specified
1905 * process. Use the regular "ptrace_may_access()" checks.
1907 if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) {
1909 mm = ERR_PTR(-EPERM);
1914 mm = ERR_PTR(security_task_movememory(task));
1917 *mem_nodes = cpuset_mems_allowed(task);
1918 mm = get_task_mm(task);
1920 put_task_struct(task);
1922 mm = ERR_PTR(-EINVAL);
1927 * Move a list of pages in the address space of the currently executing
1930 static int kernel_move_pages(pid_t pid, unsigned long nr_pages,
1931 const void __user * __user *pages,
1932 const int __user *nodes,
1933 int __user *status, int flags)
1935 struct mm_struct *mm;
1937 nodemask_t task_nodes;
1940 if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL))
1943 if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
1946 mm = find_mm_struct(pid, &task_nodes);
1951 err = do_pages_move(mm, task_nodes, nr_pages, pages,
1952 nodes, status, flags);
1954 err = do_pages_stat(mm, nr_pages, pages, status);
1960 SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages,
1961 const void __user * __user *, pages,
1962 const int __user *, nodes,
1963 int __user *, status, int, flags)
1965 return kernel_move_pages(pid, nr_pages, pages, nodes, status, flags);
1968 #ifdef CONFIG_COMPAT
1969 COMPAT_SYSCALL_DEFINE6(move_pages, pid_t, pid, compat_ulong_t, nr_pages,
1970 compat_uptr_t __user *, pages32,
1971 const int __user *, nodes,
1972 int __user *, status,
1975 const void __user * __user *pages;
1978 pages = compat_alloc_user_space(nr_pages * sizeof(void *));
1979 for (i = 0; i < nr_pages; i++) {
1982 if (get_user(p, pages32 + i) ||
1983 put_user(compat_ptr(p), pages + i))
1986 return kernel_move_pages(pid, nr_pages, pages, nodes, status, flags);
1988 #endif /* CONFIG_COMPAT */
1990 #ifdef CONFIG_NUMA_BALANCING
1992 * Returns true if this is a safe migration target node for misplaced NUMA
1993 * pages. Currently it only checks the watermarks which crude
1995 static bool migrate_balanced_pgdat(struct pglist_data *pgdat,
1996 unsigned long nr_migrate_pages)
2000 for (z = pgdat->nr_zones - 1; z >= 0; z--) {
2001 struct zone *zone = pgdat->node_zones + z;
2003 if (!populated_zone(zone))
2006 /* Avoid waking kswapd by allocating pages_to_migrate pages. */
2007 if (!zone_watermark_ok(zone, 0,
2008 high_wmark_pages(zone) +
2017 static struct page *alloc_misplaced_dst_page(struct page *page,
2020 int nid = (int) data;
2021 struct page *newpage;
2023 newpage = __alloc_pages_node(nid,
2024 (GFP_HIGHUSER_MOVABLE |
2025 __GFP_THISNODE | __GFP_NOMEMALLOC |
2026 __GFP_NORETRY | __GFP_NOWARN) &
2032 static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
2036 VM_BUG_ON_PAGE(compound_order(page) && !PageTransHuge(page), page);
2038 /* Avoid migrating to a node that is nearly full */
2039 if (!migrate_balanced_pgdat(pgdat, compound_nr(page)))
2042 if (isolate_lru_page(page))
2046 * migrate_misplaced_transhuge_page() skips page migration's usual
2047 * check on page_count(), so we must do it here, now that the page
2048 * has been isolated: a GUP pin, or any other pin, prevents migration.
2049 * The expected page count is 3: 1 for page's mapcount and 1 for the
2050 * caller's pin and 1 for the reference taken by isolate_lru_page().
2052 if (PageTransHuge(page) && page_count(page) != 3) {
2053 putback_lru_page(page);
2057 page_lru = page_is_file_lru(page);
2058 mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + page_lru,
2059 thp_nr_pages(page));
2062 * Isolating the page has taken another reference, so the
2063 * caller's reference can be safely dropped without the page
2064 * disappearing underneath us during migration.
2070 bool pmd_trans_migrating(pmd_t pmd)
2072 struct page *page = pmd_page(pmd);
2073 return PageLocked(page);
2077 * Attempt to migrate a misplaced page to the specified destination
2078 * node. Caller is expected to have an elevated reference count on
2079 * the page that will be dropped by this function before returning.
2081 int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
2084 pg_data_t *pgdat = NODE_DATA(node);
2087 LIST_HEAD(migratepages);
2090 * Don't migrate file pages that are mapped in multiple processes
2091 * with execute permissions as they are probably shared libraries.
2093 if (page_mapcount(page) != 1 && page_is_file_lru(page) &&
2094 (vma->vm_flags & VM_EXEC))
2098 * Also do not migrate dirty pages as not all filesystems can move
2099 * dirty pages in MIGRATE_ASYNC mode which is a waste of cycles.
2101 if (page_is_file_lru(page) && PageDirty(page))
2104 isolated = numamigrate_isolate_page(pgdat, page);
2108 list_add(&page->lru, &migratepages);
2109 nr_remaining = migrate_pages(&migratepages, alloc_misplaced_dst_page,
2110 NULL, node, MIGRATE_ASYNC,
2113 if (!list_empty(&migratepages)) {
2114 list_del(&page->lru);
2115 dec_node_page_state(page, NR_ISOLATED_ANON +
2116 page_is_file_lru(page));
2117 putback_lru_page(page);
2121 count_vm_numa_event(NUMA_PAGE_MIGRATE);
2122 BUG_ON(!list_empty(&migratepages));
2129 #endif /* CONFIG_NUMA_BALANCING */
2131 #if defined(CONFIG_NUMA_BALANCING) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
2133 * Migrates a THP to a given target node. page must be locked and is unlocked
2136 int migrate_misplaced_transhuge_page(struct mm_struct *mm,
2137 struct vm_area_struct *vma,
2138 pmd_t *pmd, pmd_t entry,
2139 unsigned long address,
2140 struct page *page, int node)
2143 pg_data_t *pgdat = NODE_DATA(node);
2145 struct page *new_page = NULL;
2146 int page_lru = page_is_file_lru(page);
2147 unsigned long start = address & HPAGE_PMD_MASK;
2149 new_page = alloc_pages_node(node,
2150 (GFP_TRANSHUGE_LIGHT | __GFP_THISNODE),
2154 prep_transhuge_page(new_page);
2156 isolated = numamigrate_isolate_page(pgdat, page);
2162 /* Prepare a page as a migration target */
2163 __SetPageLocked(new_page);
2164 if (PageSwapBacked(page))
2165 __SetPageSwapBacked(new_page);
2167 /* anon mapping, we can simply copy page->mapping to the new page: */
2168 new_page->mapping = page->mapping;
2169 new_page->index = page->index;
2170 /* flush the cache before copying using the kernel virtual address */
2171 flush_cache_range(vma, start, start + HPAGE_PMD_SIZE);
2172 migrate_page_copy(new_page, page);
2173 WARN_ON(PageLRU(new_page));
2175 /* Recheck the target PMD */
2176 ptl = pmd_lock(mm, pmd);
2177 if (unlikely(!pmd_same(*pmd, entry) || !page_ref_freeze(page, 2))) {
2180 /* Reverse changes made by migrate_page_copy() */
2181 if (TestClearPageActive(new_page))
2182 SetPageActive(page);
2183 if (TestClearPageUnevictable(new_page))
2184 SetPageUnevictable(page);
2186 unlock_page(new_page);
2187 put_page(new_page); /* Free it */
2189 /* Retake the callers reference and putback on LRU */
2191 putback_lru_page(page);
2192 mod_node_page_state(page_pgdat(page),
2193 NR_ISOLATED_ANON + page_lru, -HPAGE_PMD_NR);
2198 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
2199 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
2202 * Overwrite the old entry under pagetable lock and establish
2203 * the new PTE. Any parallel GUP will either observe the old
2204 * page blocking on the page lock, block on the page table
2205 * lock or observe the new page. The SetPageUptodate on the
2206 * new page and page_add_new_anon_rmap guarantee the copy is
2207 * visible before the pagetable update.
2209 page_add_anon_rmap(new_page, vma, start, true);
2211 * At this point the pmd is numa/protnone (i.e. non present) and the TLB
2212 * has already been flushed globally. So no TLB can be currently
2213 * caching this non present pmd mapping. There's no need to clear the
2214 * pmd before doing set_pmd_at(), nor to flush the TLB after
2215 * set_pmd_at(). Clearing the pmd here would introduce a race
2216 * condition against MADV_DONTNEED, because MADV_DONTNEED only holds the
2217 * mmap_lock for reading. If the pmd is set to NULL at any given time,
2218 * MADV_DONTNEED won't wait on the pmd lock and it'll skip clearing this
2221 set_pmd_at(mm, start, pmd, entry);
2222 update_mmu_cache_pmd(vma, address, &entry);
2224 page_ref_unfreeze(page, 2);
2225 mlock_migrate_page(new_page, page);
2226 page_remove_rmap(page, true);
2227 set_page_owner_migrate_reason(new_page, MR_NUMA_MISPLACED);
2231 /* Take an "isolate" reference and put new page on the LRU. */
2233 putback_lru_page(new_page);
2235 unlock_page(new_page);
2237 put_page(page); /* Drop the rmap reference */
2238 put_page(page); /* Drop the LRU isolation reference */
2240 count_vm_events(PGMIGRATE_SUCCESS, HPAGE_PMD_NR);
2241 count_vm_numa_events(NUMA_PAGE_MIGRATE, HPAGE_PMD_NR);
2243 mod_node_page_state(page_pgdat(page),
2244 NR_ISOLATED_ANON + page_lru,
2249 count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR);
2250 ptl = pmd_lock(mm, pmd);
2251 if (pmd_same(*pmd, entry)) {
2252 entry = pmd_modify(entry, vma->vm_page_prot);
2253 set_pmd_at(mm, start, pmd, entry);
2254 update_mmu_cache_pmd(vma, address, &entry);
2263 #endif /* CONFIG_NUMA_BALANCING */
2265 #endif /* CONFIG_NUMA */
2267 #ifdef CONFIG_DEVICE_PRIVATE
2268 static int migrate_vma_collect_hole(unsigned long start,
2270 __always_unused int depth,
2271 struct mm_walk *walk)
2273 struct migrate_vma *migrate = walk->private;
2276 /* Only allow populating anonymous memory. */
2277 if (!vma_is_anonymous(walk->vma)) {
2278 for (addr = start; addr < end; addr += PAGE_SIZE) {
2279 migrate->src[migrate->npages] = 0;
2280 migrate->dst[migrate->npages] = 0;
2286 for (addr = start; addr < end; addr += PAGE_SIZE) {
2287 migrate->src[migrate->npages] = MIGRATE_PFN_MIGRATE;
2288 migrate->dst[migrate->npages] = 0;
2296 static int migrate_vma_collect_skip(unsigned long start,
2298 struct mm_walk *walk)
2300 struct migrate_vma *migrate = walk->private;
2303 for (addr = start; addr < end; addr += PAGE_SIZE) {
2304 migrate->dst[migrate->npages] = 0;
2305 migrate->src[migrate->npages++] = 0;
2311 static int migrate_vma_collect_pmd(pmd_t *pmdp,
2312 unsigned long start,
2314 struct mm_walk *walk)
2316 struct migrate_vma *migrate = walk->private;
2317 struct vm_area_struct *vma = walk->vma;
2318 struct mm_struct *mm = vma->vm_mm;
2319 unsigned long addr = start, unmapped = 0;
2324 if (pmd_none(*pmdp))
2325 return migrate_vma_collect_hole(start, end, -1, walk);
2327 if (pmd_trans_huge(*pmdp)) {
2330 ptl = pmd_lock(mm, pmdp);
2331 if (unlikely(!pmd_trans_huge(*pmdp))) {
2336 page = pmd_page(*pmdp);
2337 if (is_huge_zero_page(page)) {
2339 split_huge_pmd(vma, pmdp, addr);
2340 if (pmd_trans_unstable(pmdp))
2341 return migrate_vma_collect_skip(start, end,
2348 if (unlikely(!trylock_page(page)))
2349 return migrate_vma_collect_skip(start, end,
2351 ret = split_huge_page(page);
2355 return migrate_vma_collect_skip(start, end,
2357 if (pmd_none(*pmdp))
2358 return migrate_vma_collect_hole(start, end, -1,
2363 if (unlikely(pmd_bad(*pmdp)))
2364 return migrate_vma_collect_skip(start, end, walk);
2366 ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
2367 arch_enter_lazy_mmu_mode();
2369 for (; addr < end; addr += PAGE_SIZE, ptep++) {
2370 unsigned long mpfn = 0, pfn;
2377 if (pte_none(pte)) {
2378 if (vma_is_anonymous(vma)) {
2379 mpfn = MIGRATE_PFN_MIGRATE;
2385 if (!pte_present(pte)) {
2387 * Only care about unaddressable device page special
2388 * page table entry. Other special swap entries are not
2389 * migratable, and we ignore regular swapped page.
2391 entry = pte_to_swp_entry(pte);
2392 if (!is_device_private_entry(entry))
2395 page = device_private_entry_to_page(entry);
2396 if (!(migrate->flags &
2397 MIGRATE_VMA_SELECT_DEVICE_PRIVATE) ||
2398 page->pgmap->owner != migrate->pgmap_owner)
2401 mpfn = migrate_pfn(page_to_pfn(page)) |
2402 MIGRATE_PFN_MIGRATE;
2403 if (is_write_device_private_entry(entry))
2404 mpfn |= MIGRATE_PFN_WRITE;
2406 if (!(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM))
2409 if (is_zero_pfn(pfn)) {
2410 mpfn = MIGRATE_PFN_MIGRATE;
2414 page = vm_normal_page(migrate->vma, addr, pte);
2415 mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
2416 mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0;
2419 /* FIXME support THP */
2420 if (!page || !page->mapping || PageTransCompound(page)) {
2426 * By getting a reference on the page we pin it and that blocks
2427 * any kind of migration. Side effect is that it "freezes" the
2430 * We drop this reference after isolating the page from the lru
2431 * for non device page (device page are not on the lru and thus
2432 * can't be dropped from it).
2438 * Optimize for the common case where page is only mapped once
2439 * in one process. If we can lock the page, then we can safely
2440 * set up a special migration page table entry now.
2442 if (trylock_page(page)) {
2445 mpfn |= MIGRATE_PFN_LOCKED;
2446 ptep_get_and_clear(mm, addr, ptep);
2448 /* Setup special migration page table entry */
2449 entry = make_migration_entry(page, mpfn &
2451 swp_pte = swp_entry_to_pte(entry);
2452 if (pte_present(pte)) {
2453 if (pte_soft_dirty(pte))
2454 swp_pte = pte_swp_mksoft_dirty(swp_pte);
2455 if (pte_uffd_wp(pte))
2456 swp_pte = pte_swp_mkuffd_wp(swp_pte);
2458 if (pte_swp_soft_dirty(pte))
2459 swp_pte = pte_swp_mksoft_dirty(swp_pte);
2460 if (pte_swp_uffd_wp(pte))
2461 swp_pte = pte_swp_mkuffd_wp(swp_pte);
2463 set_pte_at(mm, addr, ptep, swp_pte);
2466 * This is like regular unmap: we remove the rmap and
2467 * drop page refcount. Page won't be freed, as we took
2468 * a reference just above.
2470 page_remove_rmap(page, false);
2473 if (pte_present(pte))
2478 migrate->dst[migrate->npages] = 0;
2479 migrate->src[migrate->npages++] = mpfn;
2482 /* Only flush the TLB if we actually modified any entries */
2484 flush_tlb_range(walk->vma, start, end);
2486 arch_leave_lazy_mmu_mode();
2487 pte_unmap_unlock(ptep - 1, ptl);
2492 static const struct mm_walk_ops migrate_vma_walk_ops = {
2493 .pmd_entry = migrate_vma_collect_pmd,
2494 .pte_hole = migrate_vma_collect_hole,
2498 * migrate_vma_collect() - collect pages over a range of virtual addresses
2499 * @migrate: migrate struct containing all migration information
2501 * This will walk the CPU page table. For each virtual address backed by a
2502 * valid page, it updates the src array and takes a reference on the page, in
2503 * order to pin the page until we lock it and unmap it.
2505 static void migrate_vma_collect(struct migrate_vma *migrate)
2507 struct mmu_notifier_range range;
2510 * Note that the pgmap_owner is passed to the mmu notifier callback so
2511 * that the registered device driver can skip invalidating device
2512 * private page mappings that won't be migrated.
2514 mmu_notifier_range_init_migrate(&range, 0, migrate->vma,
2515 migrate->vma->vm_mm, migrate->start, migrate->end,
2516 migrate->pgmap_owner);
2517 mmu_notifier_invalidate_range_start(&range);
2519 walk_page_range(migrate->vma->vm_mm, migrate->start, migrate->end,
2520 &migrate_vma_walk_ops, migrate);
2522 mmu_notifier_invalidate_range_end(&range);
2523 migrate->end = migrate->start + (migrate->npages << PAGE_SHIFT);
2527 * migrate_vma_check_page() - check if page is pinned or not
2528 * @page: struct page to check
2530 * Pinned pages cannot be migrated. This is the same test as in
2531 * migrate_page_move_mapping(), except that here we allow migration of a
2534 static bool migrate_vma_check_page(struct page *page)
2537 * One extra ref because caller holds an extra reference, either from
2538 * isolate_lru_page() for a regular page, or migrate_vma_collect() for
2544 * FIXME support THP (transparent huge page), it is bit more complex to
2545 * check them than regular pages, because they can be mapped with a pmd
2546 * or with a pte (split pte mapping).
2548 if (PageCompound(page))
2551 /* Page from ZONE_DEVICE have one extra reference */
2552 if (is_zone_device_page(page)) {
2554 * Private page can never be pin as they have no valid pte and
2555 * GUP will fail for those. Yet if there is a pending migration
2556 * a thread might try to wait on the pte migration entry and
2557 * will bump the page reference count. Sadly there is no way to
2558 * differentiate a regular pin from migration wait. Hence to
2559 * avoid 2 racing thread trying to migrate back to CPU to enter
2560 * infinite loop (one stoping migration because the other is
2561 * waiting on pte migration entry). We always return true here.
2563 * FIXME proper solution is to rework migration_entry_wait() so
2564 * it does not need to take a reference on page.
2566 return is_device_private_page(page);
2569 /* For file back page */
2570 if (page_mapping(page))
2571 extra += 1 + page_has_private(page);
2573 if ((page_count(page) - extra) > page_mapcount(page))
2580 * migrate_vma_prepare() - lock pages and isolate them from the lru
2581 * @migrate: migrate struct containing all migration information
2583 * This locks pages that have been collected by migrate_vma_collect(). Once each
2584 * page is locked it is isolated from the lru (for non-device pages). Finally,
2585 * the ref taken by migrate_vma_collect() is dropped, as locked pages cannot be
2586 * migrated by concurrent kernel threads.
2588 static void migrate_vma_prepare(struct migrate_vma *migrate)
2590 const unsigned long npages = migrate->npages;
2591 const unsigned long start = migrate->start;
2592 unsigned long addr, i, restore = 0;
2593 bool allow_drain = true;
2597 for (i = 0; (i < npages) && migrate->cpages; i++) {
2598 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2604 if (!(migrate->src[i] & MIGRATE_PFN_LOCKED)) {
2606 * Because we are migrating several pages there can be
2607 * a deadlock between 2 concurrent migration where each
2608 * are waiting on each other page lock.
2610 * Make migrate_vma() a best effort thing and backoff
2611 * for any page we can not lock right away.
2613 if (!trylock_page(page)) {
2614 migrate->src[i] = 0;
2620 migrate->src[i] |= MIGRATE_PFN_LOCKED;
2623 /* ZONE_DEVICE pages are not on LRU */
2624 if (!is_zone_device_page(page)) {
2625 if (!PageLRU(page) && allow_drain) {
2626 /* Drain CPU's pagevec */
2627 lru_add_drain_all();
2628 allow_drain = false;
2631 if (isolate_lru_page(page)) {
2633 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2637 migrate->src[i] = 0;
2645 /* Drop the reference we took in collect */
2649 if (!migrate_vma_check_page(page)) {
2651 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2655 if (!is_zone_device_page(page)) {
2657 putback_lru_page(page);
2660 migrate->src[i] = 0;
2664 if (!is_zone_device_page(page))
2665 putback_lru_page(page);
2672 for (i = 0, addr = start; i < npages && restore; i++, addr += PAGE_SIZE) {
2673 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2675 if (!page || (migrate->src[i] & MIGRATE_PFN_MIGRATE))
2678 remove_migration_pte(page, migrate->vma, addr, page);
2680 migrate->src[i] = 0;
2688 * migrate_vma_unmap() - replace page mapping with special migration pte entry
2689 * @migrate: migrate struct containing all migration information
2691 * Replace page mapping (CPU page table pte) with a special migration pte entry
2692 * and check again if it has been pinned. Pinned pages are restored because we
2693 * cannot migrate them.
2695 * This is the last step before we call the device driver callback to allocate
2696 * destination memory and copy contents of original page over to new page.
2698 static void migrate_vma_unmap(struct migrate_vma *migrate)
2700 int flags = TTU_MIGRATION | TTU_IGNORE_MLOCK;
2701 const unsigned long npages = migrate->npages;
2702 const unsigned long start = migrate->start;
2703 unsigned long addr, i, restore = 0;
2705 for (i = 0; i < npages; i++) {
2706 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2708 if (!page || !(migrate->src[i] & MIGRATE_PFN_MIGRATE))
2711 if (page_mapped(page)) {
2712 try_to_unmap(page, flags);
2713 if (page_mapped(page))
2717 if (migrate_vma_check_page(page))
2721 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2726 for (addr = start, i = 0; i < npages && restore; addr += PAGE_SIZE, i++) {
2727 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2729 if (!page || (migrate->src[i] & MIGRATE_PFN_MIGRATE))
2732 remove_migration_ptes(page, page, false);
2734 migrate->src[i] = 0;
2738 if (is_zone_device_page(page))
2741 putback_lru_page(page);
2746 * migrate_vma_setup() - prepare to migrate a range of memory
2747 * @args: contains the vma, start, and pfns arrays for the migration
2749 * Returns: negative errno on failures, 0 when 0 or more pages were migrated
2752 * Prepare to migrate a range of memory virtual address range by collecting all
2753 * the pages backing each virtual address in the range, saving them inside the
2754 * src array. Then lock those pages and unmap them. Once the pages are locked
2755 * and unmapped, check whether each page is pinned or not. Pages that aren't
2756 * pinned have the MIGRATE_PFN_MIGRATE flag set (by this function) in the
2757 * corresponding src array entry. Then restores any pages that are pinned, by
2758 * remapping and unlocking those pages.
2760 * The caller should then allocate destination memory and copy source memory to
2761 * it for all those entries (ie with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE
2762 * flag set). Once these are allocated and copied, the caller must update each
2763 * corresponding entry in the dst array with the pfn value of the destination
2764 * page and with the MIGRATE_PFN_VALID and MIGRATE_PFN_LOCKED flags set
2765 * (destination pages must have their struct pages locked, via lock_page()).
2767 * Note that the caller does not have to migrate all the pages that are marked
2768 * with MIGRATE_PFN_MIGRATE flag in src array unless this is a migration from
2769 * device memory to system memory. If the caller cannot migrate a device page
2770 * back to system memory, then it must return VM_FAULT_SIGBUS, which has severe
2771 * consequences for the userspace process, so it must be avoided if at all
2774 * For empty entries inside CPU page table (pte_none() or pmd_none() is true) we
2775 * do set MIGRATE_PFN_MIGRATE flag inside the corresponding source array thus
2776 * allowing the caller to allocate device memory for those unback virtual
2777 * address. For this the caller simply has to allocate device memory and
2778 * properly set the destination entry like for regular migration. Note that
2779 * this can still fails and thus inside the device driver must check if the
2780 * migration was successful for those entries after calling migrate_vma_pages()
2781 * just like for regular migration.
2783 * After that, the callers must call migrate_vma_pages() to go over each entry
2784 * in the src array that has the MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag
2785 * set. If the corresponding entry in dst array has MIGRATE_PFN_VALID flag set,
2786 * then migrate_vma_pages() to migrate struct page information from the source
2787 * struct page to the destination struct page. If it fails to migrate the
2788 * struct page information, then it clears the MIGRATE_PFN_MIGRATE flag in the
2791 * At this point all successfully migrated pages have an entry in the src
2792 * array with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag set and the dst
2793 * array entry with MIGRATE_PFN_VALID flag set.
2795 * Once migrate_vma_pages() returns the caller may inspect which pages were
2796 * successfully migrated, and which were not. Successfully migrated pages will
2797 * have the MIGRATE_PFN_MIGRATE flag set for their src array entry.
2799 * It is safe to update device page table after migrate_vma_pages() because
2800 * both destination and source page are still locked, and the mmap_lock is held
2801 * in read mode (hence no one can unmap the range being migrated).
2803 * Once the caller is done cleaning up things and updating its page table (if it
2804 * chose to do so, this is not an obligation) it finally calls
2805 * migrate_vma_finalize() to update the CPU page table to point to new pages
2806 * for successfully migrated pages or otherwise restore the CPU page table to
2807 * point to the original source pages.
2809 int migrate_vma_setup(struct migrate_vma *args)
2811 long nr_pages = (args->end - args->start) >> PAGE_SHIFT;
2813 args->start &= PAGE_MASK;
2814 args->end &= PAGE_MASK;
2815 if (!args->vma || is_vm_hugetlb_page(args->vma) ||
2816 (args->vma->vm_flags & VM_SPECIAL) || vma_is_dax(args->vma))
2820 if (args->start < args->vma->vm_start ||
2821 args->start >= args->vma->vm_end)
2823 if (args->end <= args->vma->vm_start || args->end > args->vma->vm_end)
2825 if (!args->src || !args->dst)
2828 memset(args->src, 0, sizeof(*args->src) * nr_pages);
2832 migrate_vma_collect(args);
2835 migrate_vma_prepare(args);
2837 migrate_vma_unmap(args);
2840 * At this point pages are locked and unmapped, and thus they have
2841 * stable content and can safely be copied to destination memory that
2842 * is allocated by the drivers.
2847 EXPORT_SYMBOL(migrate_vma_setup);
2850 * This code closely matches the code in:
2851 * __handle_mm_fault()
2852 * handle_pte_fault()
2853 * do_anonymous_page()
2854 * to map in an anonymous zero page but the struct page will be a ZONE_DEVICE
2857 static void migrate_vma_insert_page(struct migrate_vma *migrate,
2863 struct vm_area_struct *vma = migrate->vma;
2864 struct mm_struct *mm = vma->vm_mm;
2874 /* Only allow populating anonymous memory */
2875 if (!vma_is_anonymous(vma))
2878 pgdp = pgd_offset(mm, addr);
2879 p4dp = p4d_alloc(mm, pgdp, addr);
2882 pudp = pud_alloc(mm, p4dp, addr);
2885 pmdp = pmd_alloc(mm, pudp, addr);
2889 if (pmd_trans_huge(*pmdp) || pmd_devmap(*pmdp))
2893 * Use pte_alloc() instead of pte_alloc_map(). We can't run
2894 * pte_offset_map() on pmds where a huge pmd might be created
2895 * from a different thread.
2897 * pte_alloc_map() is safe to use under mmap_write_lock(mm) or when
2898 * parallel threads are excluded by other means.
2900 * Here we only have mmap_read_lock(mm).
2902 if (pte_alloc(mm, pmdp))
2905 /* See the comment in pte_alloc_one_map() */
2906 if (unlikely(pmd_trans_unstable(pmdp)))
2909 if (unlikely(anon_vma_prepare(vma)))
2911 if (mem_cgroup_charge(page, vma->vm_mm, GFP_KERNEL))
2915 * The memory barrier inside __SetPageUptodate makes sure that
2916 * preceding stores to the page contents become visible before
2917 * the set_pte_at() write.
2919 __SetPageUptodate(page);
2921 if (is_zone_device_page(page)) {
2922 if (is_device_private_page(page)) {
2923 swp_entry_t swp_entry;
2925 swp_entry = make_device_private_entry(page, vma->vm_flags & VM_WRITE);
2926 entry = swp_entry_to_pte(swp_entry);
2929 * For now we only support migrating to un-addressable
2932 pr_warn_once("Unsupported ZONE_DEVICE page type.\n");
2936 entry = mk_pte(page, vma->vm_page_prot);
2937 if (vma->vm_flags & VM_WRITE)
2938 entry = pte_mkwrite(pte_mkdirty(entry));
2941 ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
2943 if (check_stable_address_space(mm))
2946 if (pte_present(*ptep)) {
2947 unsigned long pfn = pte_pfn(*ptep);
2949 if (!is_zero_pfn(pfn))
2952 } else if (!pte_none(*ptep))
2956 * Check for userfaultfd but do not deliver the fault. Instead,
2959 if (userfaultfd_missing(vma))
2962 inc_mm_counter(mm, MM_ANONPAGES);
2963 page_add_new_anon_rmap(page, vma, addr, false);
2964 if (!is_zone_device_page(page))
2965 lru_cache_add_inactive_or_unevictable(page, vma);
2969 flush_cache_page(vma, addr, pte_pfn(*ptep));
2970 ptep_clear_flush_notify(vma, addr, ptep);
2971 set_pte_at_notify(mm, addr, ptep, entry);
2972 update_mmu_cache(vma, addr, ptep);
2974 /* No need to invalidate - it was non-present before */
2975 set_pte_at(mm, addr, ptep, entry);
2976 update_mmu_cache(vma, addr, ptep);
2979 pte_unmap_unlock(ptep, ptl);
2980 *src = MIGRATE_PFN_MIGRATE;
2984 pte_unmap_unlock(ptep, ptl);
2986 *src &= ~MIGRATE_PFN_MIGRATE;
2990 * migrate_vma_pages() - migrate meta-data from src page to dst page
2991 * @migrate: migrate struct containing all migration information
2993 * This migrates struct page meta-data from source struct page to destination
2994 * struct page. This effectively finishes the migration from source page to the
2997 void migrate_vma_pages(struct migrate_vma *migrate)
2999 const unsigned long npages = migrate->npages;
3000 const unsigned long start = migrate->start;
3001 struct mmu_notifier_range range;
3002 unsigned long addr, i;
3003 bool notified = false;
3005 for (i = 0, addr = start; i < npages; addr += PAGE_SIZE, i++) {
3006 struct page *newpage = migrate_pfn_to_page(migrate->dst[i]);
3007 struct page *page = migrate_pfn_to_page(migrate->src[i]);
3008 struct address_space *mapping;
3012 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
3017 if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE))
3022 mmu_notifier_range_init(&range,
3023 MMU_NOTIFY_CLEAR, 0,
3025 migrate->vma->vm_mm,
3026 addr, migrate->end);
3027 mmu_notifier_invalidate_range_start(&range);
3029 migrate_vma_insert_page(migrate, addr, newpage,
3035 mapping = page_mapping(page);
3037 if (is_zone_device_page(newpage)) {
3038 if (is_device_private_page(newpage)) {
3040 * For now only support private anonymous when
3041 * migrating to un-addressable device memory.
3044 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
3049 * Other types of ZONE_DEVICE page are not
3052 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
3057 r = migrate_page(mapping, newpage, page, MIGRATE_SYNC_NO_COPY);
3058 if (r != MIGRATEPAGE_SUCCESS)
3059 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
3063 * No need to double call mmu_notifier->invalidate_range() callback as
3064 * the above ptep_clear_flush_notify() inside migrate_vma_insert_page()
3065 * did already call it.
3068 mmu_notifier_invalidate_range_only_end(&range);
3070 EXPORT_SYMBOL(migrate_vma_pages);
3073 * migrate_vma_finalize() - restore CPU page table entry
3074 * @migrate: migrate struct containing all migration information
3076 * This replaces the special migration pte entry with either a mapping to the
3077 * new page if migration was successful for that page, or to the original page
3080 * This also unlocks the pages and puts them back on the lru, or drops the extra
3081 * refcount, for device pages.
3083 void migrate_vma_finalize(struct migrate_vma *migrate)
3085 const unsigned long npages = migrate->npages;
3088 for (i = 0; i < npages; i++) {
3089 struct page *newpage = migrate_pfn_to_page(migrate->dst[i]);
3090 struct page *page = migrate_pfn_to_page(migrate->src[i]);
3094 unlock_page(newpage);
3100 if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE) || !newpage) {
3102 unlock_page(newpage);
3108 remove_migration_ptes(page, newpage, false);
3111 if (is_zone_device_page(page))
3114 putback_lru_page(page);
3116 if (newpage != page) {
3117 unlock_page(newpage);
3118 if (is_zone_device_page(newpage))
3121 putback_lru_page(newpage);
3125 EXPORT_SYMBOL(migrate_vma_finalize);
3126 #endif /* CONFIG_DEVICE_PRIVATE */