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>
52 #include <linux/memory.h>
54 #include <asm/tlbflush.h>
56 #define CREATE_TRACE_POINTS
57 #include <trace/events/migrate.h>
61 int isolate_movable_page(struct page
*page
, isolate_mode_t mode
)
63 struct address_space
*mapping
;
66 * Avoid burning cycles with pages that are yet under __free_pages(),
67 * or just got freed under us.
69 * In case we 'win' a race for a movable page being freed under us and
70 * raise its refcount preventing __free_pages() from doing its job
71 * the put_page() at the end of this block will take care of
72 * release this page, thus avoiding a nasty leakage.
74 if (unlikely(!get_page_unless_zero(page
)))
78 * Check PageMovable before holding a PG_lock because page's owner
79 * assumes anybody doesn't touch PG_lock of newly allocated page
80 * so unconditionally grabbing the lock ruins page's owner side.
82 if (unlikely(!__PageMovable(page
)))
85 * As movable pages are not isolated from LRU lists, concurrent
86 * compaction threads can race against page migration functions
87 * as well as race against the releasing a page.
89 * In order to avoid having an already isolated movable page
90 * being (wrongly) re-isolated while it is under migration,
91 * or to avoid attempting to isolate pages being released,
92 * lets be sure we have the page lock
93 * before proceeding with the movable page isolation steps.
95 if (unlikely(!trylock_page(page
)))
98 if (!PageMovable(page
) || PageIsolated(page
))
101 mapping
= page_mapping(page
);
102 VM_BUG_ON_PAGE(!mapping
, page
);
104 if (!mapping
->a_ops
->isolate_page(page
, mode
))
105 goto out_no_isolated
;
107 /* Driver shouldn't use PG_isolated bit of page->flags */
108 WARN_ON_ONCE(PageIsolated(page
));
109 __SetPageIsolated(page
);
122 static void putback_movable_page(struct page
*page
)
124 struct address_space
*mapping
;
126 mapping
= page_mapping(page
);
127 mapping
->a_ops
->putback_page(page
);
128 __ClearPageIsolated(page
);
132 * Put previously isolated pages back onto the appropriate lists
133 * from where they were once taken off for compaction/migration.
135 * This function shall be used whenever the isolated pageset has been
136 * built from lru, balloon, hugetlbfs page. See isolate_migratepages_range()
137 * and isolate_huge_page().
139 void putback_movable_pages(struct list_head
*l
)
144 list_for_each_entry_safe(page
, page2
, l
, lru
) {
145 if (unlikely(PageHuge(page
))) {
146 putback_active_hugepage(page
);
149 list_del(&page
->lru
);
151 * We isolated non-lru movable page so here we can use
152 * __PageMovable because LRU page's mapping cannot have
153 * PAGE_MAPPING_MOVABLE.
155 if (unlikely(__PageMovable(page
))) {
156 VM_BUG_ON_PAGE(!PageIsolated(page
), page
);
158 if (PageMovable(page
))
159 putback_movable_page(page
);
161 __ClearPageIsolated(page
);
165 mod_node_page_state(page_pgdat(page
), NR_ISOLATED_ANON
+
166 page_is_file_lru(page
), -thp_nr_pages(page
));
167 putback_lru_page(page
);
173 * Restore a potential migration pte to a working pte entry
175 static bool remove_migration_pte(struct page
*page
, struct vm_area_struct
*vma
,
176 unsigned long addr
, void *old
)
178 struct page_vma_mapped_walk pvmw
= {
182 .flags
= PVMW_SYNC
| PVMW_MIGRATION
,
188 VM_BUG_ON_PAGE(PageTail(page
), page
);
189 while (page_vma_mapped_walk(&pvmw
)) {
193 new = page
- pvmw
.page
->index
+
194 linear_page_index(vma
, pvmw
.address
);
196 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
197 /* PMD-mapped THP migration entry */
199 VM_BUG_ON_PAGE(PageHuge(page
) || !PageTransCompound(page
), page
);
200 remove_migration_pmd(&pvmw
, new);
206 pte
= pte_mkold(mk_pte(new, READ_ONCE(vma
->vm_page_prot
)));
207 if (pte_swp_soft_dirty(*pvmw
.pte
))
208 pte
= pte_mksoft_dirty(pte
);
211 * Recheck VMA as permissions can change since migration started
213 entry
= pte_to_swp_entry(*pvmw
.pte
);
214 if (is_writable_migration_entry(entry
))
215 pte
= maybe_mkwrite(pte
, vma
);
216 else if (pte_swp_uffd_wp(*pvmw
.pte
))
217 pte
= pte_mkuffd_wp(pte
);
219 if (unlikely(is_device_private_page(new))) {
221 entry
= make_writable_device_private_entry(
224 entry
= make_readable_device_private_entry(
226 pte
= swp_entry_to_pte(entry
);
227 if (pte_swp_soft_dirty(*pvmw
.pte
))
228 pte
= pte_swp_mksoft_dirty(pte
);
229 if (pte_swp_uffd_wp(*pvmw
.pte
))
230 pte
= pte_swp_mkuffd_wp(pte
);
233 #ifdef CONFIG_HUGETLB_PAGE
235 unsigned int shift
= huge_page_shift(hstate_vma(vma
));
237 pte
= pte_mkhuge(pte
);
238 pte
= arch_make_huge_pte(pte
, shift
, vma
->vm_flags
);
239 set_huge_pte_at(vma
->vm_mm
, pvmw
.address
, pvmw
.pte
, pte
);
241 hugepage_add_anon_rmap(new, vma
, pvmw
.address
);
243 page_dup_rmap(new, true);
247 set_pte_at(vma
->vm_mm
, pvmw
.address
, pvmw
.pte
, pte
);
250 page_add_anon_rmap(new, vma
, pvmw
.address
, false);
252 page_add_file_rmap(new, false);
254 if (vma
->vm_flags
& VM_LOCKED
&& !PageTransCompound(new))
257 if (PageTransHuge(page
) && PageMlocked(page
))
258 clear_page_mlock(page
);
260 /* No need to invalidate - it was non-present before */
261 update_mmu_cache(vma
, pvmw
.address
, pvmw
.pte
);
268 * Get rid of all migration entries and replace them by
269 * references to the indicated page.
271 void remove_migration_ptes(struct page
*old
, struct page
*new, bool locked
)
273 struct rmap_walk_control rwc
= {
274 .rmap_one
= remove_migration_pte
,
279 rmap_walk_locked(new, &rwc
);
281 rmap_walk(new, &rwc
);
285 * Something used the pte of a page under migration. We need to
286 * get to the page and wait until migration is finished.
287 * When we return from this function the fault will be retried.
289 void __migration_entry_wait(struct mm_struct
*mm
, pte_t
*ptep
,
298 if (!is_swap_pte(pte
))
301 entry
= pte_to_swp_entry(pte
);
302 if (!is_migration_entry(entry
))
305 page
= pfn_swap_entry_to_page(entry
);
306 page
= compound_head(page
);
309 * Once page cache replacement of page migration started, page_count
310 * is zero; but we must not call put_and_wait_on_page_locked() without
311 * a ref. Use get_page_unless_zero(), and just fault again if it fails.
313 if (!get_page_unless_zero(page
))
315 pte_unmap_unlock(ptep
, ptl
);
316 put_and_wait_on_page_locked(page
, TASK_UNINTERRUPTIBLE
);
319 pte_unmap_unlock(ptep
, ptl
);
322 void migration_entry_wait(struct mm_struct
*mm
, pmd_t
*pmd
,
323 unsigned long address
)
325 spinlock_t
*ptl
= pte_lockptr(mm
, pmd
);
326 pte_t
*ptep
= pte_offset_map(pmd
, address
);
327 __migration_entry_wait(mm
, ptep
, ptl
);
330 void migration_entry_wait_huge(struct vm_area_struct
*vma
,
331 struct mm_struct
*mm
, pte_t
*pte
)
333 spinlock_t
*ptl
= huge_pte_lockptr(hstate_vma(vma
), mm
, pte
);
334 __migration_entry_wait(mm
, pte
, ptl
);
337 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
338 void pmd_migration_entry_wait(struct mm_struct
*mm
, pmd_t
*pmd
)
343 ptl
= pmd_lock(mm
, pmd
);
344 if (!is_pmd_migration_entry(*pmd
))
346 page
= pfn_swap_entry_to_page(pmd_to_swp_entry(*pmd
));
347 if (!get_page_unless_zero(page
))
350 put_and_wait_on_page_locked(page
, TASK_UNINTERRUPTIBLE
);
357 static int expected_page_refs(struct address_space
*mapping
, struct page
*page
)
359 int expected_count
= 1;
362 * Device private pages have an extra refcount as they are
365 expected_count
+= is_device_private_page(page
);
367 expected_count
+= thp_nr_pages(page
) + page_has_private(page
);
369 return expected_count
;
373 * Replace the page in the mapping.
375 * The number of remaining references must be:
376 * 1 for anonymous pages without a mapping
377 * 2 for pages with a mapping
378 * 3 for pages with a mapping and PagePrivate/PagePrivate2 set.
380 int migrate_page_move_mapping(struct address_space
*mapping
,
381 struct page
*newpage
, struct page
*page
, int extra_count
)
383 XA_STATE(xas
, &mapping
->i_pages
, page_index(page
));
384 struct zone
*oldzone
, *newzone
;
386 int expected_count
= expected_page_refs(mapping
, page
) + extra_count
;
387 int nr
= thp_nr_pages(page
);
390 /* Anonymous page without mapping */
391 if (page_count(page
) != expected_count
)
394 /* No turning back from here */
395 newpage
->index
= page
->index
;
396 newpage
->mapping
= page
->mapping
;
397 if (PageSwapBacked(page
))
398 __SetPageSwapBacked(newpage
);
400 return MIGRATEPAGE_SUCCESS
;
403 oldzone
= page_zone(page
);
404 newzone
= page_zone(newpage
);
407 if (page_count(page
) != expected_count
|| xas_load(&xas
) != page
) {
408 xas_unlock_irq(&xas
);
412 if (!page_ref_freeze(page
, expected_count
)) {
413 xas_unlock_irq(&xas
);
418 * Now we know that no one else is looking at the page:
419 * no turning back from here.
421 newpage
->index
= page
->index
;
422 newpage
->mapping
= page
->mapping
;
423 page_ref_add(newpage
, nr
); /* add cache reference */
424 if (PageSwapBacked(page
)) {
425 __SetPageSwapBacked(newpage
);
426 if (PageSwapCache(page
)) {
427 SetPageSwapCache(newpage
);
428 set_page_private(newpage
, page_private(page
));
431 VM_BUG_ON_PAGE(PageSwapCache(page
), page
);
434 /* Move dirty while page refs frozen and newpage not yet exposed */
435 dirty
= PageDirty(page
);
437 ClearPageDirty(page
);
438 SetPageDirty(newpage
);
441 xas_store(&xas
, newpage
);
442 if (PageTransHuge(page
)) {
445 for (i
= 1; i
< nr
; i
++) {
447 xas_store(&xas
, newpage
);
452 * Drop cache reference from old page by unfreezing
453 * to one less reference.
454 * We know this isn't the last reference.
456 page_ref_unfreeze(page
, expected_count
- nr
);
459 /* Leave irq disabled to prevent preemption while updating stats */
462 * If moved to a different zone then also account
463 * the page for that zone. Other VM counters will be
464 * taken care of when we establish references to the
465 * new page and drop references to the old page.
467 * Note that anonymous pages are accounted for
468 * via NR_FILE_PAGES and NR_ANON_MAPPED if they
469 * are mapped to swap space.
471 if (newzone
!= oldzone
) {
472 struct lruvec
*old_lruvec
, *new_lruvec
;
473 struct mem_cgroup
*memcg
;
475 memcg
= page_memcg(page
);
476 old_lruvec
= mem_cgroup_lruvec(memcg
, oldzone
->zone_pgdat
);
477 new_lruvec
= mem_cgroup_lruvec(memcg
, newzone
->zone_pgdat
);
479 __mod_lruvec_state(old_lruvec
, NR_FILE_PAGES
, -nr
);
480 __mod_lruvec_state(new_lruvec
, NR_FILE_PAGES
, nr
);
481 if (PageSwapBacked(page
) && !PageSwapCache(page
)) {
482 __mod_lruvec_state(old_lruvec
, NR_SHMEM
, -nr
);
483 __mod_lruvec_state(new_lruvec
, NR_SHMEM
, nr
);
486 if (PageSwapCache(page
)) {
487 __mod_lruvec_state(old_lruvec
, NR_SWAPCACHE
, -nr
);
488 __mod_lruvec_state(new_lruvec
, NR_SWAPCACHE
, nr
);
491 if (dirty
&& mapping_can_writeback(mapping
)) {
492 __mod_lruvec_state(old_lruvec
, NR_FILE_DIRTY
, -nr
);
493 __mod_zone_page_state(oldzone
, NR_ZONE_WRITE_PENDING
, -nr
);
494 __mod_lruvec_state(new_lruvec
, NR_FILE_DIRTY
, nr
);
495 __mod_zone_page_state(newzone
, NR_ZONE_WRITE_PENDING
, nr
);
500 return MIGRATEPAGE_SUCCESS
;
502 EXPORT_SYMBOL(migrate_page_move_mapping
);
505 * The expected number of remaining references is the same as that
506 * of migrate_page_move_mapping().
508 int migrate_huge_page_move_mapping(struct address_space
*mapping
,
509 struct page
*newpage
, struct page
*page
)
511 XA_STATE(xas
, &mapping
->i_pages
, page_index(page
));
515 expected_count
= 2 + page_has_private(page
);
516 if (page_count(page
) != expected_count
|| xas_load(&xas
) != page
) {
517 xas_unlock_irq(&xas
);
521 if (!page_ref_freeze(page
, expected_count
)) {
522 xas_unlock_irq(&xas
);
526 newpage
->index
= page
->index
;
527 newpage
->mapping
= page
->mapping
;
531 xas_store(&xas
, newpage
);
533 page_ref_unfreeze(page
, expected_count
- 1);
535 xas_unlock_irq(&xas
);
537 return MIGRATEPAGE_SUCCESS
;
541 * Copy the page to its new location
543 void migrate_page_states(struct page
*newpage
, struct page
*page
)
548 SetPageError(newpage
);
549 if (PageReferenced(page
))
550 SetPageReferenced(newpage
);
551 if (PageUptodate(page
))
552 SetPageUptodate(newpage
);
553 if (TestClearPageActive(page
)) {
554 VM_BUG_ON_PAGE(PageUnevictable(page
), page
);
555 SetPageActive(newpage
);
556 } else if (TestClearPageUnevictable(page
))
557 SetPageUnevictable(newpage
);
558 if (PageWorkingset(page
))
559 SetPageWorkingset(newpage
);
560 if (PageChecked(page
))
561 SetPageChecked(newpage
);
562 if (PageMappedToDisk(page
))
563 SetPageMappedToDisk(newpage
);
565 /* Move dirty on pages not done by migrate_page_move_mapping() */
567 SetPageDirty(newpage
);
569 if (page_is_young(page
))
570 set_page_young(newpage
);
571 if (page_is_idle(page
))
572 set_page_idle(newpage
);
575 * Copy NUMA information to the new page, to prevent over-eager
576 * future migrations of this same page.
578 cpupid
= page_cpupid_xchg_last(page
, -1);
579 page_cpupid_xchg_last(newpage
, cpupid
);
581 ksm_migrate_page(newpage
, page
);
583 * Please do not reorder this without considering how mm/ksm.c's
584 * get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache().
586 if (PageSwapCache(page
))
587 ClearPageSwapCache(page
);
588 ClearPagePrivate(page
);
590 /* page->private contains hugetlb specific flags */
592 set_page_private(page
, 0);
595 * If any waiters have accumulated on the new page then
598 if (PageWriteback(newpage
))
599 end_page_writeback(newpage
);
602 * PG_readahead shares the same bit with PG_reclaim. The above
603 * end_page_writeback() may clear PG_readahead mistakenly, so set the
606 if (PageReadahead(page
))
607 SetPageReadahead(newpage
);
609 copy_page_owner(page
, newpage
);
612 mem_cgroup_migrate(page
, newpage
);
614 EXPORT_SYMBOL(migrate_page_states
);
616 void migrate_page_copy(struct page
*newpage
, struct page
*page
)
618 if (PageHuge(page
) || PageTransHuge(page
))
619 copy_huge_page(newpage
, page
);
621 copy_highpage(newpage
, page
);
623 migrate_page_states(newpage
, page
);
625 EXPORT_SYMBOL(migrate_page_copy
);
627 /************************************************************
628 * Migration functions
629 ***********************************************************/
632 * Common logic to directly migrate a single LRU page suitable for
633 * pages that do not use PagePrivate/PagePrivate2.
635 * Pages are locked upon entry and exit.
637 int migrate_page(struct address_space
*mapping
,
638 struct page
*newpage
, struct page
*page
,
639 enum migrate_mode mode
)
643 BUG_ON(PageWriteback(page
)); /* Writeback must be complete */
645 rc
= migrate_page_move_mapping(mapping
, newpage
, page
, 0);
647 if (rc
!= MIGRATEPAGE_SUCCESS
)
650 if (mode
!= MIGRATE_SYNC_NO_COPY
)
651 migrate_page_copy(newpage
, page
);
653 migrate_page_states(newpage
, page
);
654 return MIGRATEPAGE_SUCCESS
;
656 EXPORT_SYMBOL(migrate_page
);
659 /* Returns true if all buffers are successfully locked */
660 static bool buffer_migrate_lock_buffers(struct buffer_head
*head
,
661 enum migrate_mode mode
)
663 struct buffer_head
*bh
= head
;
665 /* Simple case, sync compaction */
666 if (mode
!= MIGRATE_ASYNC
) {
669 bh
= bh
->b_this_page
;
671 } while (bh
!= head
);
676 /* async case, we cannot block on lock_buffer so use trylock_buffer */
678 if (!trylock_buffer(bh
)) {
680 * We failed to lock the buffer and cannot stall in
681 * async migration. Release the taken locks
683 struct buffer_head
*failed_bh
= bh
;
685 while (bh
!= failed_bh
) {
687 bh
= bh
->b_this_page
;
692 bh
= bh
->b_this_page
;
693 } while (bh
!= head
);
697 static int __buffer_migrate_page(struct address_space
*mapping
,
698 struct page
*newpage
, struct page
*page
, enum migrate_mode mode
,
701 struct buffer_head
*bh
, *head
;
705 if (!page_has_buffers(page
))
706 return migrate_page(mapping
, newpage
, page
, mode
);
708 /* Check whether page does not have extra refs before we do more work */
709 expected_count
= expected_page_refs(mapping
, page
);
710 if (page_count(page
) != expected_count
)
713 head
= page_buffers(page
);
714 if (!buffer_migrate_lock_buffers(head
, mode
))
719 bool invalidated
= false;
723 spin_lock(&mapping
->private_lock
);
726 if (atomic_read(&bh
->b_count
)) {
730 bh
= bh
->b_this_page
;
731 } while (bh
!= head
);
737 spin_unlock(&mapping
->private_lock
);
738 invalidate_bh_lrus();
740 goto recheck_buffers
;
744 rc
= migrate_page_move_mapping(mapping
, newpage
, page
, 0);
745 if (rc
!= MIGRATEPAGE_SUCCESS
)
748 attach_page_private(newpage
, detach_page_private(page
));
752 set_bh_page(bh
, newpage
, bh_offset(bh
));
753 bh
= bh
->b_this_page
;
755 } while (bh
!= head
);
757 if (mode
!= MIGRATE_SYNC_NO_COPY
)
758 migrate_page_copy(newpage
, page
);
760 migrate_page_states(newpage
, page
);
762 rc
= MIGRATEPAGE_SUCCESS
;
765 spin_unlock(&mapping
->private_lock
);
769 bh
= bh
->b_this_page
;
771 } while (bh
!= head
);
777 * Migration function for pages with buffers. This function can only be used
778 * if the underlying filesystem guarantees that no other references to "page"
779 * exist. For example attached buffer heads are accessed only under page lock.
781 int buffer_migrate_page(struct address_space
*mapping
,
782 struct page
*newpage
, struct page
*page
, enum migrate_mode mode
)
784 return __buffer_migrate_page(mapping
, newpage
, page
, mode
, false);
786 EXPORT_SYMBOL(buffer_migrate_page
);
789 * Same as above except that this variant is more careful and checks that there
790 * are also no buffer head references. This function is the right one for
791 * mappings where buffer heads are directly looked up and referenced (such as
792 * block device mappings).
794 int buffer_migrate_page_norefs(struct address_space
*mapping
,
795 struct page
*newpage
, struct page
*page
, enum migrate_mode mode
)
797 return __buffer_migrate_page(mapping
, newpage
, page
, mode
, true);
802 * Writeback a page to clean the dirty state
804 static int writeout(struct address_space
*mapping
, struct page
*page
)
806 struct writeback_control wbc
= {
807 .sync_mode
= WB_SYNC_NONE
,
810 .range_end
= LLONG_MAX
,
815 if (!mapping
->a_ops
->writepage
)
816 /* No write method for the address space */
819 if (!clear_page_dirty_for_io(page
))
820 /* Someone else already triggered a write */
824 * A dirty page may imply that the underlying filesystem has
825 * the page on some queue. So the page must be clean for
826 * migration. Writeout may mean we loose the lock and the
827 * page state is no longer what we checked for earlier.
828 * At this point we know that the migration attempt cannot
831 remove_migration_ptes(page
, page
, false);
833 rc
= mapping
->a_ops
->writepage(page
, &wbc
);
835 if (rc
!= AOP_WRITEPAGE_ACTIVATE
)
836 /* unlocked. Relock */
839 return (rc
< 0) ? -EIO
: -EAGAIN
;
843 * Default handling if a filesystem does not provide a migration function.
845 static int fallback_migrate_page(struct address_space
*mapping
,
846 struct page
*newpage
, struct page
*page
, enum migrate_mode mode
)
848 if (PageDirty(page
)) {
849 /* Only writeback pages in full synchronous migration */
852 case MIGRATE_SYNC_NO_COPY
:
857 return writeout(mapping
, page
);
861 * Buffers may be managed in a filesystem specific way.
862 * We must have no buffers or drop them.
864 if (page_has_private(page
) &&
865 !try_to_release_page(page
, GFP_KERNEL
))
866 return mode
== MIGRATE_SYNC
? -EAGAIN
: -EBUSY
;
868 return migrate_page(mapping
, newpage
, page
, mode
);
872 * Move a page to a newly allocated page
873 * The page is locked and all ptes have been successfully removed.
875 * The new page will have replaced the old page if this function
880 * MIGRATEPAGE_SUCCESS - success
882 static int move_to_new_page(struct page
*newpage
, struct page
*page
,
883 enum migrate_mode mode
)
885 struct address_space
*mapping
;
887 bool is_lru
= !__PageMovable(page
);
889 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
890 VM_BUG_ON_PAGE(!PageLocked(newpage
), newpage
);
892 mapping
= page_mapping(page
);
894 if (likely(is_lru
)) {
896 rc
= migrate_page(mapping
, newpage
, page
, mode
);
897 else if (mapping
->a_ops
->migratepage
)
899 * Most pages have a mapping and most filesystems
900 * provide a migratepage callback. Anonymous pages
901 * are part of swap space which also has its own
902 * migratepage callback. This is the most common path
903 * for page migration.
905 rc
= mapping
->a_ops
->migratepage(mapping
, newpage
,
908 rc
= fallback_migrate_page(mapping
, newpage
,
912 * In case of non-lru page, it could be released after
913 * isolation step. In that case, we shouldn't try migration.
915 VM_BUG_ON_PAGE(!PageIsolated(page
), page
);
916 if (!PageMovable(page
)) {
917 rc
= MIGRATEPAGE_SUCCESS
;
918 __ClearPageIsolated(page
);
922 rc
= mapping
->a_ops
->migratepage(mapping
, newpage
,
924 WARN_ON_ONCE(rc
== MIGRATEPAGE_SUCCESS
&&
925 !PageIsolated(page
));
929 * When successful, old pagecache page->mapping must be cleared before
930 * page is freed; but stats require that PageAnon be left as PageAnon.
932 if (rc
== MIGRATEPAGE_SUCCESS
) {
933 if (__PageMovable(page
)) {
934 VM_BUG_ON_PAGE(!PageIsolated(page
), page
);
937 * We clear PG_movable under page_lock so any compactor
938 * cannot try to migrate this page.
940 __ClearPageIsolated(page
);
944 * Anonymous and movable page->mapping will be cleared by
945 * free_pages_prepare so don't reset it here for keeping
946 * the type to work PageAnon, for example.
948 if (!PageMappingFlags(page
))
949 page
->mapping
= NULL
;
951 if (likely(!is_zone_device_page(newpage
))) {
952 int i
, nr
= compound_nr(newpage
);
954 for (i
= 0; i
< nr
; i
++)
955 flush_dcache_page(newpage
+ i
);
962 static int __unmap_and_move(struct page
*page
, struct page
*newpage
,
963 int force
, enum migrate_mode mode
)
966 bool page_was_mapped
= false;
967 struct anon_vma
*anon_vma
= NULL
;
968 bool is_lru
= !__PageMovable(page
);
970 if (!trylock_page(page
)) {
971 if (!force
|| mode
== MIGRATE_ASYNC
)
975 * It's not safe for direct compaction to call lock_page.
976 * For example, during page readahead pages are added locked
977 * to the LRU. Later, when the IO completes the pages are
978 * marked uptodate and unlocked. However, the queueing
979 * could be merging multiple pages for one bio (e.g.
980 * mpage_readahead). If an allocation happens for the
981 * second or third page, the process can end up locking
982 * the same page twice and deadlocking. Rather than
983 * trying to be clever about what pages can be locked,
984 * avoid the use of lock_page for direct compaction
987 if (current
->flags
& PF_MEMALLOC
)
993 if (PageWriteback(page
)) {
995 * Only in the case of a full synchronous migration is it
996 * necessary to wait for PageWriteback. In the async case,
997 * the retry loop is too short and in the sync-light case,
998 * the overhead of stalling is too much
1002 case MIGRATE_SYNC_NO_COPY
:
1010 wait_on_page_writeback(page
);
1014 * By try_to_migrate(), page->mapcount goes down to 0 here. In this case,
1015 * we cannot notice that anon_vma is freed while we migrates a page.
1016 * This get_anon_vma() delays freeing anon_vma pointer until the end
1017 * of migration. File cache pages are no problem because of page_lock()
1018 * File Caches may use write_page() or lock_page() in migration, then,
1019 * just care Anon page here.
1021 * Only page_get_anon_vma() understands the subtleties of
1022 * getting a hold on an anon_vma from outside one of its mms.
1023 * But if we cannot get anon_vma, then we won't need it anyway,
1024 * because that implies that the anon page is no longer mapped
1025 * (and cannot be remapped so long as we hold the page lock).
1027 if (PageAnon(page
) && !PageKsm(page
))
1028 anon_vma
= page_get_anon_vma(page
);
1031 * Block others from accessing the new page when we get around to
1032 * establishing additional references. We are usually the only one
1033 * holding a reference to newpage at this point. We used to have a BUG
1034 * here if trylock_page(newpage) fails, but would like to allow for
1035 * cases where there might be a race with the previous use of newpage.
1036 * This is much like races on refcount of oldpage: just don't BUG().
1038 if (unlikely(!trylock_page(newpage
)))
1041 if (unlikely(!is_lru
)) {
1042 rc
= move_to_new_page(newpage
, page
, mode
);
1043 goto out_unlock_both
;
1047 * Corner case handling:
1048 * 1. When a new swap-cache page is read into, it is added to the LRU
1049 * and treated as swapcache but it has no rmap yet.
1050 * Calling try_to_unmap() against a page->mapping==NULL page will
1051 * trigger a BUG. So handle it here.
1052 * 2. An orphaned page (see truncate_cleanup_page) might have
1053 * fs-private metadata. The page can be picked up due to memory
1054 * offlining. Everywhere else except page reclaim, the page is
1055 * invisible to the vm, so the page can not be migrated. So try to
1056 * free the metadata, so the page can be freed.
1058 if (!page
->mapping
) {
1059 VM_BUG_ON_PAGE(PageAnon(page
), page
);
1060 if (page_has_private(page
)) {
1061 try_to_free_buffers(page
);
1062 goto out_unlock_both
;
1064 } else if (page_mapped(page
)) {
1065 /* Establish migration ptes */
1066 VM_BUG_ON_PAGE(PageAnon(page
) && !PageKsm(page
) && !anon_vma
,
1068 try_to_migrate(page
, 0);
1069 page_was_mapped
= true;
1072 if (!page_mapped(page
))
1073 rc
= move_to_new_page(newpage
, page
, mode
);
1075 if (page_was_mapped
)
1076 remove_migration_ptes(page
,
1077 rc
== MIGRATEPAGE_SUCCESS
? newpage
: page
, false);
1080 unlock_page(newpage
);
1082 /* Drop an anon_vma reference if we took one */
1084 put_anon_vma(anon_vma
);
1088 * If migration is successful, decrease refcount of the newpage
1089 * which will not free the page because new page owner increased
1090 * refcounter. As well, if it is LRU page, add the page to LRU
1091 * list in here. Use the old state of the isolated source page to
1092 * determine if we migrated a LRU page. newpage was already unlocked
1093 * and possibly modified by its owner - don't rely on the page
1096 if (rc
== MIGRATEPAGE_SUCCESS
) {
1097 if (unlikely(!is_lru
))
1100 putback_lru_page(newpage
);
1108 * node_demotion[] example:
1110 * Consider a system with two sockets. Each socket has
1111 * three classes of memory attached: fast, medium and slow.
1112 * Each memory class is placed in its own NUMA node. The
1113 * CPUs are placed in the node with the "fast" memory. The
1114 * 6 NUMA nodes (0-5) might be split among the sockets like
1120 * When Node 0 fills up, its memory should be migrated to
1121 * Node 1. When Node 1 fills up, it should be migrated to
1122 * Node 2. The migration path start on the nodes with the
1123 * processors (since allocations default to this node) and
1124 * fast memory, progress through medium and end with the
1127 * 0 -> 1 -> 2 -> stop
1128 * 3 -> 4 -> 5 -> stop
1130 * This is represented in the node_demotion[] like this:
1132 * { 1, // Node 0 migrates to 1
1133 * 2, // Node 1 migrates to 2
1134 * -1, // Node 2 does not migrate
1135 * 4, // Node 3 migrates to 4
1136 * 5, // Node 4 migrates to 5
1137 * -1} // Node 5 does not migrate
1141 * Writes to this array occur without locking. Cycles are
1142 * not allowed: Node X demotes to Y which demotes to X...
1144 * If multiple reads are performed, a single rcu_read_lock()
1145 * must be held over all reads to ensure that no cycles are
1148 static int node_demotion
[MAX_NUMNODES
] __read_mostly
=
1149 {[0 ... MAX_NUMNODES
- 1] = NUMA_NO_NODE
};
1152 * next_demotion_node() - Get the next node in the demotion path
1153 * @node: The starting node to lookup the next node
1155 * Return: node id for next memory node in the demotion path hierarchy
1156 * from @node; NUMA_NO_NODE if @node is terminal. This does not keep
1157 * @node online or guarantee that it *continues* to be the next demotion
1160 int next_demotion_node(int node
)
1165 * node_demotion[] is updated without excluding this
1166 * function from running. RCU doesn't provide any
1167 * compiler barriers, so the READ_ONCE() is required
1168 * to avoid compiler reordering or read merging.
1170 * Make sure to use RCU over entire code blocks if
1171 * node_demotion[] reads need to be consistent.
1174 target
= READ_ONCE(node_demotion
[node
]);
1181 * Obtain the lock on page, remove all ptes and migrate the page
1182 * to the newly allocated page in newpage.
1184 static int unmap_and_move(new_page_t get_new_page
,
1185 free_page_t put_new_page
,
1186 unsigned long private, struct page
*page
,
1187 int force
, enum migrate_mode mode
,
1188 enum migrate_reason reason
,
1189 struct list_head
*ret
)
1191 int rc
= MIGRATEPAGE_SUCCESS
;
1192 struct page
*newpage
= NULL
;
1194 if (!thp_migration_supported() && PageTransHuge(page
))
1197 if (page_count(page
) == 1) {
1198 /* page was freed from under us. So we are done. */
1199 ClearPageActive(page
);
1200 ClearPageUnevictable(page
);
1201 if (unlikely(__PageMovable(page
))) {
1203 if (!PageMovable(page
))
1204 __ClearPageIsolated(page
);
1210 newpage
= get_new_page(page
, private);
1214 rc
= __unmap_and_move(page
, newpage
, force
, mode
);
1215 if (rc
== MIGRATEPAGE_SUCCESS
)
1216 set_page_owner_migrate_reason(newpage
, reason
);
1219 if (rc
!= -EAGAIN
) {
1221 * A page that has been migrated has all references
1222 * removed and will be freed. A page that has not been
1223 * migrated will have kept its references and be restored.
1225 list_del(&page
->lru
);
1229 * If migration is successful, releases reference grabbed during
1230 * isolation. Otherwise, restore the page to right list unless
1233 if (rc
== MIGRATEPAGE_SUCCESS
) {
1235 * Compaction can migrate also non-LRU pages which are
1236 * not accounted to NR_ISOLATED_*. They can be recognized
1239 if (likely(!__PageMovable(page
)))
1240 mod_node_page_state(page_pgdat(page
), NR_ISOLATED_ANON
+
1241 page_is_file_lru(page
), -thp_nr_pages(page
));
1243 if (reason
!= MR_MEMORY_FAILURE
)
1245 * We release the page in page_handle_poison.
1250 list_add_tail(&page
->lru
, ret
);
1253 put_new_page(newpage
, private);
1262 * Counterpart of unmap_and_move_page() for hugepage migration.
1264 * This function doesn't wait the completion of hugepage I/O
1265 * because there is no race between I/O and migration for hugepage.
1266 * Note that currently hugepage I/O occurs only in direct I/O
1267 * where no lock is held and PG_writeback is irrelevant,
1268 * and writeback status of all subpages are counted in the reference
1269 * count of the head page (i.e. if all subpages of a 2MB hugepage are
1270 * under direct I/O, the reference of the head page is 512 and a bit more.)
1271 * This means that when we try to migrate hugepage whose subpages are
1272 * doing direct I/O, some references remain after try_to_unmap() and
1273 * hugepage migration fails without data corruption.
1275 * There is also no race when direct I/O is issued on the page under migration,
1276 * because then pte is replaced with migration swap entry and direct I/O code
1277 * will wait in the page fault for migration to complete.
1279 static int unmap_and_move_huge_page(new_page_t get_new_page
,
1280 free_page_t put_new_page
, unsigned long private,
1281 struct page
*hpage
, int force
,
1282 enum migrate_mode mode
, int reason
,
1283 struct list_head
*ret
)
1286 int page_was_mapped
= 0;
1287 struct page
*new_hpage
;
1288 struct anon_vma
*anon_vma
= NULL
;
1289 struct address_space
*mapping
= NULL
;
1292 * Migratability of hugepages depends on architectures and their size.
1293 * This check is necessary because some callers of hugepage migration
1294 * like soft offline and memory hotremove don't walk through page
1295 * tables or check whether the hugepage is pmd-based or not before
1296 * kicking migration.
1298 if (!hugepage_migration_supported(page_hstate(hpage
))) {
1299 list_move_tail(&hpage
->lru
, ret
);
1303 if (page_count(hpage
) == 1) {
1304 /* page was freed from under us. So we are done. */
1305 putback_active_hugepage(hpage
);
1306 return MIGRATEPAGE_SUCCESS
;
1309 new_hpage
= get_new_page(hpage
, private);
1313 if (!trylock_page(hpage
)) {
1318 case MIGRATE_SYNC_NO_COPY
:
1327 * Check for pages which are in the process of being freed. Without
1328 * page_mapping() set, hugetlbfs specific move page routine will not
1329 * be called and we could leak usage counts for subpools.
1331 if (hugetlb_page_subpool(hpage
) && !page_mapping(hpage
)) {
1336 if (PageAnon(hpage
))
1337 anon_vma
= page_get_anon_vma(hpage
);
1339 if (unlikely(!trylock_page(new_hpage
)))
1342 if (page_mapped(hpage
)) {
1343 bool mapping_locked
= false;
1344 enum ttu_flags ttu
= 0;
1346 if (!PageAnon(hpage
)) {
1348 * In shared mappings, try_to_unmap could potentially
1349 * call huge_pmd_unshare. Because of this, take
1350 * semaphore in write mode here and set TTU_RMAP_LOCKED
1351 * to let lower levels know we have taken the lock.
1353 mapping
= hugetlb_page_mapping_lock_write(hpage
);
1354 if (unlikely(!mapping
))
1355 goto unlock_put_anon
;
1357 mapping_locked
= true;
1358 ttu
|= TTU_RMAP_LOCKED
;
1361 try_to_migrate(hpage
, ttu
);
1362 page_was_mapped
= 1;
1365 i_mmap_unlock_write(mapping
);
1368 if (!page_mapped(hpage
))
1369 rc
= move_to_new_page(new_hpage
, hpage
, mode
);
1371 if (page_was_mapped
)
1372 remove_migration_ptes(hpage
,
1373 rc
== MIGRATEPAGE_SUCCESS
? new_hpage
: hpage
, false);
1376 unlock_page(new_hpage
);
1380 put_anon_vma(anon_vma
);
1382 if (rc
== MIGRATEPAGE_SUCCESS
) {
1383 move_hugetlb_state(hpage
, new_hpage
, reason
);
1384 put_new_page
= NULL
;
1390 if (rc
== MIGRATEPAGE_SUCCESS
)
1391 putback_active_hugepage(hpage
);
1392 else if (rc
!= -EAGAIN
)
1393 list_move_tail(&hpage
->lru
, ret
);
1396 * If migration was not successful and there's a freeing callback, use
1397 * it. Otherwise, put_page() will drop the reference grabbed during
1401 put_new_page(new_hpage
, private);
1403 putback_active_hugepage(new_hpage
);
1408 static inline int try_split_thp(struct page
*page
, struct page
**page2
,
1409 struct list_head
*from
)
1414 rc
= split_huge_page_to_list(page
, from
);
1417 list_safe_reset_next(page
, *page2
, lru
);
1423 * migrate_pages - migrate the pages specified in a list, to the free pages
1424 * supplied as the target for the page migration
1426 * @from: The list of pages to be migrated.
1427 * @get_new_page: The function used to allocate free pages to be used
1428 * as the target of the page migration.
1429 * @put_new_page: The function used to free target pages if migration
1430 * fails, or NULL if no special handling is necessary.
1431 * @private: Private data to be passed on to get_new_page()
1432 * @mode: The migration mode that specifies the constraints for
1433 * page migration, if any.
1434 * @reason: The reason for page migration.
1435 * @ret_succeeded: Set to the number of pages migrated successfully if
1436 * the caller passes a non-NULL pointer.
1438 * The function returns after 10 attempts or if no pages are movable any more
1439 * because the list has become empty or no retryable pages exist any more.
1440 * It is caller's responsibility to call putback_movable_pages() to return pages
1441 * to the LRU or free list only if ret != 0.
1443 * Returns the number of pages that were not migrated, or an error code.
1445 int migrate_pages(struct list_head
*from
, new_page_t get_new_page
,
1446 free_page_t put_new_page
, unsigned long private,
1447 enum migrate_mode mode
, int reason
, unsigned int *ret_succeeded
)
1452 int nr_succeeded
= 0;
1453 int nr_thp_succeeded
= 0;
1454 int nr_thp_failed
= 0;
1455 int nr_thp_split
= 0;
1457 bool is_thp
= false;
1460 int swapwrite
= current
->flags
& PF_SWAPWRITE
;
1461 int rc
, nr_subpages
;
1462 LIST_HEAD(ret_pages
);
1463 bool nosplit
= (reason
== MR_NUMA_MISPLACED
);
1465 trace_mm_migrate_pages_start(mode
, reason
);
1468 current
->flags
|= PF_SWAPWRITE
;
1470 for (pass
= 0; pass
< 10 && (retry
|| thp_retry
); pass
++) {
1474 list_for_each_entry_safe(page
, page2
, from
, lru
) {
1477 * THP statistics is based on the source huge page.
1478 * Capture required information that might get lost
1481 is_thp
= PageTransHuge(page
) && !PageHuge(page
);
1482 nr_subpages
= thp_nr_pages(page
);
1486 rc
= unmap_and_move_huge_page(get_new_page
,
1487 put_new_page
, private, page
,
1488 pass
> 2, mode
, reason
,
1491 rc
= unmap_and_move(get_new_page
, put_new_page
,
1492 private, page
, pass
> 2, mode
,
1493 reason
, &ret_pages
);
1496 * Success: non hugetlb page will be freed, hugetlb
1497 * page will be put back
1498 * -EAGAIN: stay on the from list
1499 * -ENOMEM: stay on the from list
1500 * Other errno: put on ret_pages list then splice to
1505 * THP migration might be unsupported or the
1506 * allocation could've failed so we should
1507 * retry on the same page with the THP split
1510 * Head page is retried immediately and tail
1511 * pages are added to the tail of the list so
1512 * we encounter them after the rest of the list
1516 /* THP migration is unsupported */
1518 if (!try_split_thp(page
, &page2
, from
)) {
1524 nr_failed
+= nr_subpages
;
1528 /* Hugetlb migration is unsupported */
1533 * When memory is low, don't bother to try to migrate
1534 * other pages, just exit.
1535 * THP NUMA faulting doesn't split THP to retry.
1537 if (is_thp
&& !nosplit
) {
1538 if (!try_split_thp(page
, &page2
, from
)) {
1544 nr_failed
+= nr_subpages
;
1556 case MIGRATEPAGE_SUCCESS
:
1559 nr_succeeded
+= nr_subpages
;
1566 * Permanent failure (-EBUSY, etc.):
1567 * unlike -EAGAIN case, the failed page is
1568 * removed from migration page list and not
1569 * retried in the next outer loop.
1573 nr_failed
+= nr_subpages
;
1581 nr_failed
+= retry
+ thp_retry
;
1582 nr_thp_failed
+= thp_retry
;
1586 * Put the permanent failure page back to migration list, they
1587 * will be put back to the right list by the caller.
1589 list_splice(&ret_pages
, from
);
1591 count_vm_events(PGMIGRATE_SUCCESS
, nr_succeeded
);
1592 count_vm_events(PGMIGRATE_FAIL
, nr_failed
);
1593 count_vm_events(THP_MIGRATION_SUCCESS
, nr_thp_succeeded
);
1594 count_vm_events(THP_MIGRATION_FAIL
, nr_thp_failed
);
1595 count_vm_events(THP_MIGRATION_SPLIT
, nr_thp_split
);
1596 trace_mm_migrate_pages(nr_succeeded
, nr_failed
, nr_thp_succeeded
,
1597 nr_thp_failed
, nr_thp_split
, mode
, reason
);
1600 current
->flags
&= ~PF_SWAPWRITE
;
1603 *ret_succeeded
= nr_succeeded
;
1608 struct page
*alloc_migration_target(struct page
*page
, unsigned long private)
1610 struct migration_target_control
*mtc
;
1612 unsigned int order
= 0;
1613 struct page
*new_page
= NULL
;
1617 mtc
= (struct migration_target_control
*)private;
1618 gfp_mask
= mtc
->gfp_mask
;
1620 if (nid
== NUMA_NO_NODE
)
1621 nid
= page_to_nid(page
);
1623 if (PageHuge(page
)) {
1624 struct hstate
*h
= page_hstate(compound_head(page
));
1626 gfp_mask
= htlb_modify_alloc_mask(h
, gfp_mask
);
1627 return alloc_huge_page_nodemask(h
, nid
, mtc
->nmask
, gfp_mask
);
1630 if (PageTransHuge(page
)) {
1632 * clear __GFP_RECLAIM to make the migration callback
1633 * consistent with regular THP allocations.
1635 gfp_mask
&= ~__GFP_RECLAIM
;
1636 gfp_mask
|= GFP_TRANSHUGE
;
1637 order
= HPAGE_PMD_ORDER
;
1639 zidx
= zone_idx(page_zone(page
));
1640 if (is_highmem_idx(zidx
) || zidx
== ZONE_MOVABLE
)
1641 gfp_mask
|= __GFP_HIGHMEM
;
1643 new_page
= __alloc_pages(gfp_mask
, order
, nid
, mtc
->nmask
);
1645 if (new_page
&& PageTransHuge(new_page
))
1646 prep_transhuge_page(new_page
);
1653 static int store_status(int __user
*status
, int start
, int value
, int nr
)
1656 if (put_user(value
, status
+ start
))
1664 static int do_move_pages_to_node(struct mm_struct
*mm
,
1665 struct list_head
*pagelist
, int node
)
1668 struct migration_target_control mtc
= {
1670 .gfp_mask
= GFP_HIGHUSER_MOVABLE
| __GFP_THISNODE
,
1673 err
= migrate_pages(pagelist
, alloc_migration_target
, NULL
,
1674 (unsigned long)&mtc
, MIGRATE_SYNC
, MR_SYSCALL
, NULL
);
1676 putback_movable_pages(pagelist
);
1681 * Resolves the given address to a struct page, isolates it from the LRU and
1682 * puts it to the given pagelist.
1684 * errno - if the page cannot be found/isolated
1685 * 0 - when it doesn't have to be migrated because it is already on the
1687 * 1 - when it has been queued
1689 static int add_page_for_migration(struct mm_struct
*mm
, unsigned long addr
,
1690 int node
, struct list_head
*pagelist
, bool migrate_all
)
1692 struct vm_area_struct
*vma
;
1694 unsigned int follflags
;
1699 vma
= find_vma(mm
, addr
);
1700 if (!vma
|| addr
< vma
->vm_start
|| !vma_migratable(vma
))
1703 /* FOLL_DUMP to ignore special (like zero) pages */
1704 follflags
= FOLL_GET
| FOLL_DUMP
;
1705 page
= follow_page(vma
, addr
, follflags
);
1707 err
= PTR_ERR(page
);
1716 if (page_to_nid(page
) == node
)
1720 if (page_mapcount(page
) > 1 && !migrate_all
)
1723 if (PageHuge(page
)) {
1724 if (PageHead(page
)) {
1725 isolate_huge_page(page
, pagelist
);
1731 head
= compound_head(page
);
1732 err
= isolate_lru_page(head
);
1737 list_add_tail(&head
->lru
, pagelist
);
1738 mod_node_page_state(page_pgdat(head
),
1739 NR_ISOLATED_ANON
+ page_is_file_lru(head
),
1740 thp_nr_pages(head
));
1744 * Either remove the duplicate refcount from
1745 * isolate_lru_page() or drop the page ref if it was
1750 mmap_read_unlock(mm
);
1754 static int move_pages_and_store_status(struct mm_struct
*mm
, int node
,
1755 struct list_head
*pagelist
, int __user
*status
,
1756 int start
, int i
, unsigned long nr_pages
)
1760 if (list_empty(pagelist
))
1763 err
= do_move_pages_to_node(mm
, pagelist
, node
);
1766 * Positive err means the number of failed
1767 * pages to migrate. Since we are going to
1768 * abort and return the number of non-migrated
1769 * pages, so need to include the rest of the
1770 * nr_pages that have not been attempted as
1774 err
+= nr_pages
- i
- 1;
1777 return store_status(status
, start
, node
, i
- start
);
1781 * Migrate an array of page address onto an array of nodes and fill
1782 * the corresponding array of status.
1784 static int do_pages_move(struct mm_struct
*mm
, nodemask_t task_nodes
,
1785 unsigned long nr_pages
,
1786 const void __user
* __user
*pages
,
1787 const int __user
*nodes
,
1788 int __user
*status
, int flags
)
1790 int current_node
= NUMA_NO_NODE
;
1791 LIST_HEAD(pagelist
);
1795 lru_cache_disable();
1797 for (i
= start
= 0; i
< nr_pages
; i
++) {
1798 const void __user
*p
;
1803 if (get_user(p
, pages
+ i
))
1805 if (get_user(node
, nodes
+ i
))
1807 addr
= (unsigned long)untagged_addr(p
);
1810 if (node
< 0 || node
>= MAX_NUMNODES
)
1812 if (!node_state(node
, N_MEMORY
))
1816 if (!node_isset(node
, task_nodes
))
1819 if (current_node
== NUMA_NO_NODE
) {
1820 current_node
= node
;
1822 } else if (node
!= current_node
) {
1823 err
= move_pages_and_store_status(mm
, current_node
,
1824 &pagelist
, status
, start
, i
, nr_pages
);
1828 current_node
= node
;
1832 * Errors in the page lookup or isolation are not fatal and we simply
1833 * report them via status
1835 err
= add_page_for_migration(mm
, addr
, current_node
,
1836 &pagelist
, flags
& MPOL_MF_MOVE_ALL
);
1839 /* The page is successfully queued for migration */
1844 * If the page is already on the target node (!err), store the
1845 * node, otherwise, store the err.
1847 err
= store_status(status
, i
, err
? : current_node
, 1);
1851 err
= move_pages_and_store_status(mm
, current_node
, &pagelist
,
1852 status
, start
, i
, nr_pages
);
1855 current_node
= NUMA_NO_NODE
;
1858 /* Make sure we do not overwrite the existing error */
1859 err1
= move_pages_and_store_status(mm
, current_node
, &pagelist
,
1860 status
, start
, i
, nr_pages
);
1869 * Determine the nodes of an array of pages and store it in an array of status.
1871 static void do_pages_stat_array(struct mm_struct
*mm
, unsigned long nr_pages
,
1872 const void __user
**pages
, int *status
)
1878 for (i
= 0; i
< nr_pages
; i
++) {
1879 unsigned long addr
= (unsigned long)(*pages
);
1880 struct vm_area_struct
*vma
;
1884 vma
= vma_lookup(mm
, addr
);
1888 /* FOLL_DUMP to ignore special (like zero) pages */
1889 page
= follow_page(vma
, addr
, FOLL_DUMP
);
1891 err
= PTR_ERR(page
);
1895 err
= page
? page_to_nid(page
) : -ENOENT
;
1903 mmap_read_unlock(mm
);
1906 static int get_compat_pages_array(const void __user
*chunk_pages
[],
1907 const void __user
* __user
*pages
,
1908 unsigned long chunk_nr
)
1910 compat_uptr_t __user
*pages32
= (compat_uptr_t __user
*)pages
;
1914 for (i
= 0; i
< chunk_nr
; i
++) {
1915 if (get_user(p
, pages32
+ i
))
1917 chunk_pages
[i
] = compat_ptr(p
);
1924 * Determine the nodes of a user array of pages and store it in
1925 * a user array of status.
1927 static int do_pages_stat(struct mm_struct
*mm
, unsigned long nr_pages
,
1928 const void __user
* __user
*pages
,
1931 #define DO_PAGES_STAT_CHUNK_NR 16
1932 const void __user
*chunk_pages
[DO_PAGES_STAT_CHUNK_NR
];
1933 int chunk_status
[DO_PAGES_STAT_CHUNK_NR
];
1936 unsigned long chunk_nr
;
1938 chunk_nr
= nr_pages
;
1939 if (chunk_nr
> DO_PAGES_STAT_CHUNK_NR
)
1940 chunk_nr
= DO_PAGES_STAT_CHUNK_NR
;
1942 if (in_compat_syscall()) {
1943 if (get_compat_pages_array(chunk_pages
, pages
,
1947 if (copy_from_user(chunk_pages
, pages
,
1948 chunk_nr
* sizeof(*chunk_pages
)))
1952 do_pages_stat_array(mm
, chunk_nr
, chunk_pages
, chunk_status
);
1954 if (copy_to_user(status
, chunk_status
, chunk_nr
* sizeof(*status
)))
1959 nr_pages
-= chunk_nr
;
1961 return nr_pages
? -EFAULT
: 0;
1964 static struct mm_struct
*find_mm_struct(pid_t pid
, nodemask_t
*mem_nodes
)
1966 struct task_struct
*task
;
1967 struct mm_struct
*mm
;
1970 * There is no need to check if current process has the right to modify
1971 * the specified process when they are same.
1975 *mem_nodes
= cpuset_mems_allowed(current
);
1979 /* Find the mm_struct */
1981 task
= find_task_by_vpid(pid
);
1984 return ERR_PTR(-ESRCH
);
1986 get_task_struct(task
);
1989 * Check if this process has the right to modify the specified
1990 * process. Use the regular "ptrace_may_access()" checks.
1992 if (!ptrace_may_access(task
, PTRACE_MODE_READ_REALCREDS
)) {
1994 mm
= ERR_PTR(-EPERM
);
1999 mm
= ERR_PTR(security_task_movememory(task
));
2002 *mem_nodes
= cpuset_mems_allowed(task
);
2003 mm
= get_task_mm(task
);
2005 put_task_struct(task
);
2007 mm
= ERR_PTR(-EINVAL
);
2012 * Move a list of pages in the address space of the currently executing
2015 static int kernel_move_pages(pid_t pid
, unsigned long nr_pages
,
2016 const void __user
* __user
*pages
,
2017 const int __user
*nodes
,
2018 int __user
*status
, int flags
)
2020 struct mm_struct
*mm
;
2022 nodemask_t task_nodes
;
2025 if (flags
& ~(MPOL_MF_MOVE
|MPOL_MF_MOVE_ALL
))
2028 if ((flags
& MPOL_MF_MOVE_ALL
) && !capable(CAP_SYS_NICE
))
2031 mm
= find_mm_struct(pid
, &task_nodes
);
2036 err
= do_pages_move(mm
, task_nodes
, nr_pages
, pages
,
2037 nodes
, status
, flags
);
2039 err
= do_pages_stat(mm
, nr_pages
, pages
, status
);
2045 SYSCALL_DEFINE6(move_pages
, pid_t
, pid
, unsigned long, nr_pages
,
2046 const void __user
* __user
*, pages
,
2047 const int __user
*, nodes
,
2048 int __user
*, status
, int, flags
)
2050 return kernel_move_pages(pid
, nr_pages
, pages
, nodes
, status
, flags
);
2053 #ifdef CONFIG_NUMA_BALANCING
2055 * Returns true if this is a safe migration target node for misplaced NUMA
2056 * pages. Currently it only checks the watermarks which crude
2058 static bool migrate_balanced_pgdat(struct pglist_data
*pgdat
,
2059 unsigned long nr_migrate_pages
)
2063 for (z
= pgdat
->nr_zones
- 1; z
>= 0; z
--) {
2064 struct zone
*zone
= pgdat
->node_zones
+ z
;
2066 if (!populated_zone(zone
))
2069 /* Avoid waking kswapd by allocating pages_to_migrate pages. */
2070 if (!zone_watermark_ok(zone
, 0,
2071 high_wmark_pages(zone
) +
2080 static struct page
*alloc_misplaced_dst_page(struct page
*page
,
2083 int nid
= (int) data
;
2084 struct page
*newpage
;
2086 newpage
= __alloc_pages_node(nid
,
2087 (GFP_HIGHUSER_MOVABLE
|
2088 __GFP_THISNODE
| __GFP_NOMEMALLOC
|
2089 __GFP_NORETRY
| __GFP_NOWARN
) &
2095 static struct page
*alloc_misplaced_dst_page_thp(struct page
*page
,
2098 int nid
= (int) data
;
2099 struct page
*newpage
;
2101 newpage
= alloc_pages_node(nid
, (GFP_TRANSHUGE_LIGHT
| __GFP_THISNODE
),
2106 prep_transhuge_page(newpage
);
2112 static int numamigrate_isolate_page(pg_data_t
*pgdat
, struct page
*page
)
2115 int nr_pages
= thp_nr_pages(page
);
2117 VM_BUG_ON_PAGE(compound_order(page
) && !PageTransHuge(page
), page
);
2119 /* Do not migrate THP mapped by multiple processes */
2120 if (PageTransHuge(page
) && total_mapcount(page
) > 1)
2123 /* Avoid migrating to a node that is nearly full */
2124 if (!migrate_balanced_pgdat(pgdat
, nr_pages
))
2127 if (isolate_lru_page(page
))
2130 page_lru
= page_is_file_lru(page
);
2131 mod_node_page_state(page_pgdat(page
), NR_ISOLATED_ANON
+ page_lru
,
2135 * Isolating the page has taken another reference, so the
2136 * caller's reference can be safely dropped without the page
2137 * disappearing underneath us during migration.
2144 * Attempt to migrate a misplaced page to the specified destination
2145 * node. Caller is expected to have an elevated reference count on
2146 * the page that will be dropped by this function before returning.
2148 int migrate_misplaced_page(struct page
*page
, struct vm_area_struct
*vma
,
2151 pg_data_t
*pgdat
= NODE_DATA(node
);
2154 LIST_HEAD(migratepages
);
2157 int nr_pages
= thp_nr_pages(page
);
2160 * PTE mapped THP or HugeTLB page can't reach here so the page could
2161 * be either base page or THP. And it must be head page if it is
2164 compound
= PageTransHuge(page
);
2167 new = alloc_misplaced_dst_page_thp
;
2169 new = alloc_misplaced_dst_page
;
2172 * Don't migrate file pages that are mapped in multiple processes
2173 * with execute permissions as they are probably shared libraries.
2175 if (page_mapcount(page
) != 1 && page_is_file_lru(page
) &&
2176 (vma
->vm_flags
& VM_EXEC
))
2180 * Also do not migrate dirty pages as not all filesystems can move
2181 * dirty pages in MIGRATE_ASYNC mode which is a waste of cycles.
2183 if (page_is_file_lru(page
) && PageDirty(page
))
2186 isolated
= numamigrate_isolate_page(pgdat
, page
);
2190 list_add(&page
->lru
, &migratepages
);
2191 nr_remaining
= migrate_pages(&migratepages
, *new, NULL
, node
,
2192 MIGRATE_ASYNC
, MR_NUMA_MISPLACED
, NULL
);
2194 if (!list_empty(&migratepages
)) {
2195 list_del(&page
->lru
);
2196 mod_node_page_state(page_pgdat(page
), NR_ISOLATED_ANON
+
2197 page_is_file_lru(page
), -nr_pages
);
2198 putback_lru_page(page
);
2202 count_vm_numa_events(NUMA_PAGE_MIGRATE
, nr_pages
);
2203 BUG_ON(!list_empty(&migratepages
));
2210 #endif /* CONFIG_NUMA_BALANCING */
2211 #endif /* CONFIG_NUMA */
2213 #ifdef CONFIG_DEVICE_PRIVATE
2214 static int migrate_vma_collect_skip(unsigned long start
,
2216 struct mm_walk
*walk
)
2218 struct migrate_vma
*migrate
= walk
->private;
2221 for (addr
= start
; addr
< end
; addr
+= PAGE_SIZE
) {
2222 migrate
->dst
[migrate
->npages
] = 0;
2223 migrate
->src
[migrate
->npages
++] = 0;
2229 static int migrate_vma_collect_hole(unsigned long start
,
2231 __always_unused
int depth
,
2232 struct mm_walk
*walk
)
2234 struct migrate_vma
*migrate
= walk
->private;
2237 /* Only allow populating anonymous memory. */
2238 if (!vma_is_anonymous(walk
->vma
))
2239 return migrate_vma_collect_skip(start
, end
, walk
);
2241 for (addr
= start
; addr
< end
; addr
+= PAGE_SIZE
) {
2242 migrate
->src
[migrate
->npages
] = MIGRATE_PFN_MIGRATE
;
2243 migrate
->dst
[migrate
->npages
] = 0;
2251 static int migrate_vma_collect_pmd(pmd_t
*pmdp
,
2252 unsigned long start
,
2254 struct mm_walk
*walk
)
2256 struct migrate_vma
*migrate
= walk
->private;
2257 struct vm_area_struct
*vma
= walk
->vma
;
2258 struct mm_struct
*mm
= vma
->vm_mm
;
2259 unsigned long addr
= start
, unmapped
= 0;
2264 if (pmd_none(*pmdp
))
2265 return migrate_vma_collect_hole(start
, end
, -1, walk
);
2267 if (pmd_trans_huge(*pmdp
)) {
2270 ptl
= pmd_lock(mm
, pmdp
);
2271 if (unlikely(!pmd_trans_huge(*pmdp
))) {
2276 page
= pmd_page(*pmdp
);
2277 if (is_huge_zero_page(page
)) {
2279 split_huge_pmd(vma
, pmdp
, addr
);
2280 if (pmd_trans_unstable(pmdp
))
2281 return migrate_vma_collect_skip(start
, end
,
2288 if (unlikely(!trylock_page(page
)))
2289 return migrate_vma_collect_skip(start
, end
,
2291 ret
= split_huge_page(page
);
2295 return migrate_vma_collect_skip(start
, end
,
2297 if (pmd_none(*pmdp
))
2298 return migrate_vma_collect_hole(start
, end
, -1,
2303 if (unlikely(pmd_bad(*pmdp
)))
2304 return migrate_vma_collect_skip(start
, end
, walk
);
2306 ptep
= pte_offset_map_lock(mm
, pmdp
, addr
, &ptl
);
2307 arch_enter_lazy_mmu_mode();
2309 for (; addr
< end
; addr
+= PAGE_SIZE
, ptep
++) {
2310 unsigned long mpfn
= 0, pfn
;
2317 if (pte_none(pte
)) {
2318 if (vma_is_anonymous(vma
)) {
2319 mpfn
= MIGRATE_PFN_MIGRATE
;
2325 if (!pte_present(pte
)) {
2327 * Only care about unaddressable device page special
2328 * page table entry. Other special swap entries are not
2329 * migratable, and we ignore regular swapped page.
2331 entry
= pte_to_swp_entry(pte
);
2332 if (!is_device_private_entry(entry
))
2335 page
= pfn_swap_entry_to_page(entry
);
2336 if (!(migrate
->flags
&
2337 MIGRATE_VMA_SELECT_DEVICE_PRIVATE
) ||
2338 page
->pgmap
->owner
!= migrate
->pgmap_owner
)
2341 mpfn
= migrate_pfn(page_to_pfn(page
)) |
2342 MIGRATE_PFN_MIGRATE
;
2343 if (is_writable_device_private_entry(entry
))
2344 mpfn
|= MIGRATE_PFN_WRITE
;
2346 if (!(migrate
->flags
& MIGRATE_VMA_SELECT_SYSTEM
))
2349 if (is_zero_pfn(pfn
)) {
2350 mpfn
= MIGRATE_PFN_MIGRATE
;
2354 page
= vm_normal_page(migrate
->vma
, addr
, pte
);
2355 mpfn
= migrate_pfn(pfn
) | MIGRATE_PFN_MIGRATE
;
2356 mpfn
|= pte_write(pte
) ? MIGRATE_PFN_WRITE
: 0;
2359 /* FIXME support THP */
2360 if (!page
|| !page
->mapping
|| PageTransCompound(page
)) {
2366 * By getting a reference on the page we pin it and that blocks
2367 * any kind of migration. Side effect is that it "freezes" the
2370 * We drop this reference after isolating the page from the lru
2371 * for non device page (device page are not on the lru and thus
2372 * can't be dropped from it).
2378 * Optimize for the common case where page is only mapped once
2379 * in one process. If we can lock the page, then we can safely
2380 * set up a special migration page table entry now.
2382 if (trylock_page(page
)) {
2385 mpfn
|= MIGRATE_PFN_LOCKED
;
2386 ptep_get_and_clear(mm
, addr
, ptep
);
2388 /* Setup special migration page table entry */
2389 if (mpfn
& MIGRATE_PFN_WRITE
)
2390 entry
= make_writable_migration_entry(
2393 entry
= make_readable_migration_entry(
2395 swp_pte
= swp_entry_to_pte(entry
);
2396 if (pte_present(pte
)) {
2397 if (pte_soft_dirty(pte
))
2398 swp_pte
= pte_swp_mksoft_dirty(swp_pte
);
2399 if (pte_uffd_wp(pte
))
2400 swp_pte
= pte_swp_mkuffd_wp(swp_pte
);
2402 if (pte_swp_soft_dirty(pte
))
2403 swp_pte
= pte_swp_mksoft_dirty(swp_pte
);
2404 if (pte_swp_uffd_wp(pte
))
2405 swp_pte
= pte_swp_mkuffd_wp(swp_pte
);
2407 set_pte_at(mm
, addr
, ptep
, swp_pte
);
2410 * This is like regular unmap: we remove the rmap and
2411 * drop page refcount. Page won't be freed, as we took
2412 * a reference just above.
2414 page_remove_rmap(page
, false);
2417 if (pte_present(pte
))
2422 migrate
->dst
[migrate
->npages
] = 0;
2423 migrate
->src
[migrate
->npages
++] = mpfn
;
2426 /* Only flush the TLB if we actually modified any entries */
2428 flush_tlb_range(walk
->vma
, start
, end
);
2430 arch_leave_lazy_mmu_mode();
2431 pte_unmap_unlock(ptep
- 1, ptl
);
2436 static const struct mm_walk_ops migrate_vma_walk_ops
= {
2437 .pmd_entry
= migrate_vma_collect_pmd
,
2438 .pte_hole
= migrate_vma_collect_hole
,
2442 * migrate_vma_collect() - collect pages over a range of virtual addresses
2443 * @migrate: migrate struct containing all migration information
2445 * This will walk the CPU page table. For each virtual address backed by a
2446 * valid page, it updates the src array and takes a reference on the page, in
2447 * order to pin the page until we lock it and unmap it.
2449 static void migrate_vma_collect(struct migrate_vma
*migrate
)
2451 struct mmu_notifier_range range
;
2454 * Note that the pgmap_owner is passed to the mmu notifier callback so
2455 * that the registered device driver can skip invalidating device
2456 * private page mappings that won't be migrated.
2458 mmu_notifier_range_init_owner(&range
, MMU_NOTIFY_MIGRATE
, 0,
2459 migrate
->vma
, migrate
->vma
->vm_mm
, migrate
->start
, migrate
->end
,
2460 migrate
->pgmap_owner
);
2461 mmu_notifier_invalidate_range_start(&range
);
2463 walk_page_range(migrate
->vma
->vm_mm
, migrate
->start
, migrate
->end
,
2464 &migrate_vma_walk_ops
, migrate
);
2466 mmu_notifier_invalidate_range_end(&range
);
2467 migrate
->end
= migrate
->start
+ (migrate
->npages
<< PAGE_SHIFT
);
2471 * migrate_vma_check_page() - check if page is pinned or not
2472 * @page: struct page to check
2474 * Pinned pages cannot be migrated. This is the same test as in
2475 * migrate_page_move_mapping(), except that here we allow migration of a
2478 static bool migrate_vma_check_page(struct page
*page
)
2481 * One extra ref because caller holds an extra reference, either from
2482 * isolate_lru_page() for a regular page, or migrate_vma_collect() for
2488 * FIXME support THP (transparent huge page), it is bit more complex to
2489 * check them than regular pages, because they can be mapped with a pmd
2490 * or with a pte (split pte mapping).
2492 if (PageCompound(page
))
2495 /* Page from ZONE_DEVICE have one extra reference */
2496 if (is_zone_device_page(page
)) {
2498 * Private page can never be pin as they have no valid pte and
2499 * GUP will fail for those. Yet if there is a pending migration
2500 * a thread might try to wait on the pte migration entry and
2501 * will bump the page reference count. Sadly there is no way to
2502 * differentiate a regular pin from migration wait. Hence to
2503 * avoid 2 racing thread trying to migrate back to CPU to enter
2504 * infinite loop (one stopping migration because the other is
2505 * waiting on pte migration entry). We always return true here.
2507 * FIXME proper solution is to rework migration_entry_wait() so
2508 * it does not need to take a reference on page.
2510 return is_device_private_page(page
);
2513 /* For file back page */
2514 if (page_mapping(page
))
2515 extra
+= 1 + page_has_private(page
);
2517 if ((page_count(page
) - extra
) > page_mapcount(page
))
2524 * migrate_vma_prepare() - lock pages and isolate them from the lru
2525 * @migrate: migrate struct containing all migration information
2527 * This locks pages that have been collected by migrate_vma_collect(). Once each
2528 * page is locked it is isolated from the lru (for non-device pages). Finally,
2529 * the ref taken by migrate_vma_collect() is dropped, as locked pages cannot be
2530 * migrated by concurrent kernel threads.
2532 static void migrate_vma_prepare(struct migrate_vma
*migrate
)
2534 const unsigned long npages
= migrate
->npages
;
2535 const unsigned long start
= migrate
->start
;
2536 unsigned long addr
, i
, restore
= 0;
2537 bool allow_drain
= true;
2541 for (i
= 0; (i
< npages
) && migrate
->cpages
; i
++) {
2542 struct page
*page
= migrate_pfn_to_page(migrate
->src
[i
]);
2548 if (!(migrate
->src
[i
] & MIGRATE_PFN_LOCKED
)) {
2550 * Because we are migrating several pages there can be
2551 * a deadlock between 2 concurrent migration where each
2552 * are waiting on each other page lock.
2554 * Make migrate_vma() a best effort thing and backoff
2555 * for any page we can not lock right away.
2557 if (!trylock_page(page
)) {
2558 migrate
->src
[i
] = 0;
2564 migrate
->src
[i
] |= MIGRATE_PFN_LOCKED
;
2567 /* ZONE_DEVICE pages are not on LRU */
2568 if (!is_zone_device_page(page
)) {
2569 if (!PageLRU(page
) && allow_drain
) {
2570 /* Drain CPU's pagevec */
2571 lru_add_drain_all();
2572 allow_drain
= false;
2575 if (isolate_lru_page(page
)) {
2577 migrate
->src
[i
] &= ~MIGRATE_PFN_MIGRATE
;
2581 migrate
->src
[i
] = 0;
2589 /* Drop the reference we took in collect */
2593 if (!migrate_vma_check_page(page
)) {
2595 migrate
->src
[i
] &= ~MIGRATE_PFN_MIGRATE
;
2599 if (!is_zone_device_page(page
)) {
2601 putback_lru_page(page
);
2604 migrate
->src
[i
] = 0;
2608 if (!is_zone_device_page(page
))
2609 putback_lru_page(page
);
2616 for (i
= 0, addr
= start
; i
< npages
&& restore
; i
++, addr
+= PAGE_SIZE
) {
2617 struct page
*page
= migrate_pfn_to_page(migrate
->src
[i
]);
2619 if (!page
|| (migrate
->src
[i
] & MIGRATE_PFN_MIGRATE
))
2622 remove_migration_pte(page
, migrate
->vma
, addr
, page
);
2624 migrate
->src
[i
] = 0;
2632 * migrate_vma_unmap() - replace page mapping with special migration pte entry
2633 * @migrate: migrate struct containing all migration information
2635 * Replace page mapping (CPU page table pte) with a special migration pte entry
2636 * and check again if it has been pinned. Pinned pages are restored because we
2637 * cannot migrate them.
2639 * This is the last step before we call the device driver callback to allocate
2640 * destination memory and copy contents of original page over to new page.
2642 static void migrate_vma_unmap(struct migrate_vma
*migrate
)
2644 const unsigned long npages
= migrate
->npages
;
2645 const unsigned long start
= migrate
->start
;
2646 unsigned long addr
, i
, restore
= 0;
2648 for (i
= 0; i
< npages
; i
++) {
2649 struct page
*page
= migrate_pfn_to_page(migrate
->src
[i
]);
2651 if (!page
|| !(migrate
->src
[i
] & MIGRATE_PFN_MIGRATE
))
2654 if (page_mapped(page
)) {
2655 try_to_migrate(page
, 0);
2656 if (page_mapped(page
))
2660 if (migrate_vma_check_page(page
))
2664 migrate
->src
[i
] &= ~MIGRATE_PFN_MIGRATE
;
2669 for (addr
= start
, i
= 0; i
< npages
&& restore
; addr
+= PAGE_SIZE
, i
++) {
2670 struct page
*page
= migrate_pfn_to_page(migrate
->src
[i
]);
2672 if (!page
|| (migrate
->src
[i
] & MIGRATE_PFN_MIGRATE
))
2675 remove_migration_ptes(page
, page
, false);
2677 migrate
->src
[i
] = 0;
2681 if (is_zone_device_page(page
))
2684 putback_lru_page(page
);
2689 * migrate_vma_setup() - prepare to migrate a range of memory
2690 * @args: contains the vma, start, and pfns arrays for the migration
2692 * Returns: negative errno on failures, 0 when 0 or more pages were migrated
2695 * Prepare to migrate a range of memory virtual address range by collecting all
2696 * the pages backing each virtual address in the range, saving them inside the
2697 * src array. Then lock those pages and unmap them. Once the pages are locked
2698 * and unmapped, check whether each page is pinned or not. Pages that aren't
2699 * pinned have the MIGRATE_PFN_MIGRATE flag set (by this function) in the
2700 * corresponding src array entry. Then restores any pages that are pinned, by
2701 * remapping and unlocking those pages.
2703 * The caller should then allocate destination memory and copy source memory to
2704 * it for all those entries (ie with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE
2705 * flag set). Once these are allocated and copied, the caller must update each
2706 * corresponding entry in the dst array with the pfn value of the destination
2707 * page and with the MIGRATE_PFN_VALID and MIGRATE_PFN_LOCKED flags set
2708 * (destination pages must have their struct pages locked, via lock_page()).
2710 * Note that the caller does not have to migrate all the pages that are marked
2711 * with MIGRATE_PFN_MIGRATE flag in src array unless this is a migration from
2712 * device memory to system memory. If the caller cannot migrate a device page
2713 * back to system memory, then it must return VM_FAULT_SIGBUS, which has severe
2714 * consequences for the userspace process, so it must be avoided if at all
2717 * For empty entries inside CPU page table (pte_none() or pmd_none() is true) we
2718 * do set MIGRATE_PFN_MIGRATE flag inside the corresponding source array thus
2719 * allowing the caller to allocate device memory for those unbacked virtual
2720 * addresses. For this the caller simply has to allocate device memory and
2721 * properly set the destination entry like for regular migration. Note that
2722 * this can still fail, and thus inside the device driver you must check if the
2723 * migration was successful for those entries after calling migrate_vma_pages(),
2724 * just like for regular migration.
2726 * After that, the callers must call migrate_vma_pages() to go over each entry
2727 * in the src array that has the MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag
2728 * set. If the corresponding entry in dst array has MIGRATE_PFN_VALID flag set,
2729 * then migrate_vma_pages() to migrate struct page information from the source
2730 * struct page to the destination struct page. If it fails to migrate the
2731 * struct page information, then it clears the MIGRATE_PFN_MIGRATE flag in the
2734 * At this point all successfully migrated pages have an entry in the src
2735 * array with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag set and the dst
2736 * array entry with MIGRATE_PFN_VALID flag set.
2738 * Once migrate_vma_pages() returns the caller may inspect which pages were
2739 * successfully migrated, and which were not. Successfully migrated pages will
2740 * have the MIGRATE_PFN_MIGRATE flag set for their src array entry.
2742 * It is safe to update device page table after migrate_vma_pages() because
2743 * both destination and source page are still locked, and the mmap_lock is held
2744 * in read mode (hence no one can unmap the range being migrated).
2746 * Once the caller is done cleaning up things and updating its page table (if it
2747 * chose to do so, this is not an obligation) it finally calls
2748 * migrate_vma_finalize() to update the CPU page table to point to new pages
2749 * for successfully migrated pages or otherwise restore the CPU page table to
2750 * point to the original source pages.
2752 int migrate_vma_setup(struct migrate_vma
*args
)
2754 long nr_pages
= (args
->end
- args
->start
) >> PAGE_SHIFT
;
2756 args
->start
&= PAGE_MASK
;
2757 args
->end
&= PAGE_MASK
;
2758 if (!args
->vma
|| is_vm_hugetlb_page(args
->vma
) ||
2759 (args
->vma
->vm_flags
& VM_SPECIAL
) || vma_is_dax(args
->vma
))
2763 if (args
->start
< args
->vma
->vm_start
||
2764 args
->start
>= args
->vma
->vm_end
)
2766 if (args
->end
<= args
->vma
->vm_start
|| args
->end
> args
->vma
->vm_end
)
2768 if (!args
->src
|| !args
->dst
)
2771 memset(args
->src
, 0, sizeof(*args
->src
) * nr_pages
);
2775 migrate_vma_collect(args
);
2778 migrate_vma_prepare(args
);
2780 migrate_vma_unmap(args
);
2783 * At this point pages are locked and unmapped, and thus they have
2784 * stable content and can safely be copied to destination memory that
2785 * is allocated by the drivers.
2790 EXPORT_SYMBOL(migrate_vma_setup
);
2793 * This code closely matches the code in:
2794 * __handle_mm_fault()
2795 * handle_pte_fault()
2796 * do_anonymous_page()
2797 * to map in an anonymous zero page but the struct page will be a ZONE_DEVICE
2800 static void migrate_vma_insert_page(struct migrate_vma
*migrate
,
2805 struct vm_area_struct
*vma
= migrate
->vma
;
2806 struct mm_struct
*mm
= vma
->vm_mm
;
2816 /* Only allow populating anonymous memory */
2817 if (!vma_is_anonymous(vma
))
2820 pgdp
= pgd_offset(mm
, addr
);
2821 p4dp
= p4d_alloc(mm
, pgdp
, addr
);
2824 pudp
= pud_alloc(mm
, p4dp
, addr
);
2827 pmdp
= pmd_alloc(mm
, pudp
, addr
);
2831 if (pmd_trans_huge(*pmdp
) || pmd_devmap(*pmdp
))
2835 * Use pte_alloc() instead of pte_alloc_map(). We can't run
2836 * pte_offset_map() on pmds where a huge pmd might be created
2837 * from a different thread.
2839 * pte_alloc_map() is safe to use under mmap_write_lock(mm) or when
2840 * parallel threads are excluded by other means.
2842 * Here we only have mmap_read_lock(mm).
2844 if (pte_alloc(mm
, pmdp
))
2847 /* See the comment in pte_alloc_one_map() */
2848 if (unlikely(pmd_trans_unstable(pmdp
)))
2851 if (unlikely(anon_vma_prepare(vma
)))
2853 if (mem_cgroup_charge(page
, vma
->vm_mm
, GFP_KERNEL
))
2857 * The memory barrier inside __SetPageUptodate makes sure that
2858 * preceding stores to the page contents become visible before
2859 * the set_pte_at() write.
2861 __SetPageUptodate(page
);
2863 if (is_zone_device_page(page
)) {
2864 if (is_device_private_page(page
)) {
2865 swp_entry_t swp_entry
;
2867 if (vma
->vm_flags
& VM_WRITE
)
2868 swp_entry
= make_writable_device_private_entry(
2871 swp_entry
= make_readable_device_private_entry(
2873 entry
= swp_entry_to_pte(swp_entry
);
2876 * For now we only support migrating to un-addressable
2879 pr_warn_once("Unsupported ZONE_DEVICE page type.\n");
2883 entry
= mk_pte(page
, vma
->vm_page_prot
);
2884 if (vma
->vm_flags
& VM_WRITE
)
2885 entry
= pte_mkwrite(pte_mkdirty(entry
));
2888 ptep
= pte_offset_map_lock(mm
, pmdp
, addr
, &ptl
);
2890 if (check_stable_address_space(mm
))
2893 if (pte_present(*ptep
)) {
2894 unsigned long pfn
= pte_pfn(*ptep
);
2896 if (!is_zero_pfn(pfn
))
2899 } else if (!pte_none(*ptep
))
2903 * Check for userfaultfd but do not deliver the fault. Instead,
2906 if (userfaultfd_missing(vma
))
2909 inc_mm_counter(mm
, MM_ANONPAGES
);
2910 page_add_new_anon_rmap(page
, vma
, addr
, false);
2911 if (!is_zone_device_page(page
))
2912 lru_cache_add_inactive_or_unevictable(page
, vma
);
2916 flush_cache_page(vma
, addr
, pte_pfn(*ptep
));
2917 ptep_clear_flush_notify(vma
, addr
, ptep
);
2918 set_pte_at_notify(mm
, addr
, ptep
, entry
);
2919 update_mmu_cache(vma
, addr
, ptep
);
2921 /* No need to invalidate - it was non-present before */
2922 set_pte_at(mm
, addr
, ptep
, entry
);
2923 update_mmu_cache(vma
, addr
, ptep
);
2926 pte_unmap_unlock(ptep
, ptl
);
2927 *src
= MIGRATE_PFN_MIGRATE
;
2931 pte_unmap_unlock(ptep
, ptl
);
2933 *src
&= ~MIGRATE_PFN_MIGRATE
;
2937 * migrate_vma_pages() - migrate meta-data from src page to dst page
2938 * @migrate: migrate struct containing all migration information
2940 * This migrates struct page meta-data from source struct page to destination
2941 * struct page. This effectively finishes the migration from source page to the
2944 void migrate_vma_pages(struct migrate_vma
*migrate
)
2946 const unsigned long npages
= migrate
->npages
;
2947 const unsigned long start
= migrate
->start
;
2948 struct mmu_notifier_range range
;
2949 unsigned long addr
, i
;
2950 bool notified
= false;
2952 for (i
= 0, addr
= start
; i
< npages
; addr
+= PAGE_SIZE
, i
++) {
2953 struct page
*newpage
= migrate_pfn_to_page(migrate
->dst
[i
]);
2954 struct page
*page
= migrate_pfn_to_page(migrate
->src
[i
]);
2955 struct address_space
*mapping
;
2959 migrate
->src
[i
] &= ~MIGRATE_PFN_MIGRATE
;
2964 if (!(migrate
->src
[i
] & MIGRATE_PFN_MIGRATE
))
2969 mmu_notifier_range_init_owner(&range
,
2970 MMU_NOTIFY_MIGRATE
, 0, migrate
->vma
,
2971 migrate
->vma
->vm_mm
, addr
, migrate
->end
,
2972 migrate
->pgmap_owner
);
2973 mmu_notifier_invalidate_range_start(&range
);
2975 migrate_vma_insert_page(migrate
, addr
, newpage
,
2980 mapping
= page_mapping(page
);
2982 if (is_zone_device_page(newpage
)) {
2983 if (is_device_private_page(newpage
)) {
2985 * For now only support private anonymous when
2986 * migrating to un-addressable device memory.
2989 migrate
->src
[i
] &= ~MIGRATE_PFN_MIGRATE
;
2994 * Other types of ZONE_DEVICE page are not
2997 migrate
->src
[i
] &= ~MIGRATE_PFN_MIGRATE
;
3002 r
= migrate_page(mapping
, newpage
, page
, MIGRATE_SYNC_NO_COPY
);
3003 if (r
!= MIGRATEPAGE_SUCCESS
)
3004 migrate
->src
[i
] &= ~MIGRATE_PFN_MIGRATE
;
3008 * No need to double call mmu_notifier->invalidate_range() callback as
3009 * the above ptep_clear_flush_notify() inside migrate_vma_insert_page()
3010 * did already call it.
3013 mmu_notifier_invalidate_range_only_end(&range
);
3015 EXPORT_SYMBOL(migrate_vma_pages
);
3018 * migrate_vma_finalize() - restore CPU page table entry
3019 * @migrate: migrate struct containing all migration information
3021 * This replaces the special migration pte entry with either a mapping to the
3022 * new page if migration was successful for that page, or to the original page
3025 * This also unlocks the pages and puts them back on the lru, or drops the extra
3026 * refcount, for device pages.
3028 void migrate_vma_finalize(struct migrate_vma
*migrate
)
3030 const unsigned long npages
= migrate
->npages
;
3033 for (i
= 0; i
< npages
; i
++) {
3034 struct page
*newpage
= migrate_pfn_to_page(migrate
->dst
[i
]);
3035 struct page
*page
= migrate_pfn_to_page(migrate
->src
[i
]);
3039 unlock_page(newpage
);
3045 if (!(migrate
->src
[i
] & MIGRATE_PFN_MIGRATE
) || !newpage
) {
3047 unlock_page(newpage
);
3053 remove_migration_ptes(page
, newpage
, false);
3056 if (is_zone_device_page(page
))
3059 putback_lru_page(page
);
3061 if (newpage
!= page
) {
3062 unlock_page(newpage
);
3063 if (is_zone_device_page(newpage
))
3066 putback_lru_page(newpage
);
3070 EXPORT_SYMBOL(migrate_vma_finalize
);
3071 #endif /* CONFIG_DEVICE_PRIVATE */
3073 #if defined(CONFIG_HOTPLUG_CPU)
3074 /* Disable reclaim-based migration. */
3075 static void __disable_all_migrate_targets(void)
3079 for_each_online_node(node
)
3080 node_demotion
[node
] = NUMA_NO_NODE
;
3083 static void disable_all_migrate_targets(void)
3085 __disable_all_migrate_targets();
3088 * Ensure that the "disable" is visible across the system.
3089 * Readers will see either a combination of before+disable
3090 * state or disable+after. They will never see before and
3091 * after state together.
3093 * The before+after state together might have cycles and
3094 * could cause readers to do things like loop until this
3095 * function finishes. This ensures they can only see a
3096 * single "bad" read and would, for instance, only loop
3103 * Find an automatic demotion target for 'node'.
3104 * Failing here is OK. It might just indicate
3105 * being at the end of a chain.
3107 static int establish_migrate_target(int node
, nodemask_t
*used
)
3109 int migration_target
;
3112 * Can not set a migration target on a
3113 * node with it already set.
3115 * No need for READ_ONCE() here since this
3116 * in the write path for node_demotion[].
3117 * This should be the only thread writing.
3119 if (node_demotion
[node
] != NUMA_NO_NODE
)
3120 return NUMA_NO_NODE
;
3122 migration_target
= find_next_best_node(node
, used
);
3123 if (migration_target
== NUMA_NO_NODE
)
3124 return NUMA_NO_NODE
;
3126 node_demotion
[node
] = migration_target
;
3128 return migration_target
;
3132 * When memory fills up on a node, memory contents can be
3133 * automatically migrated to another node instead of
3134 * discarded at reclaim.
3136 * Establish a "migration path" which will start at nodes
3137 * with CPUs and will follow the priorities used to build the
3138 * page allocator zonelists.
3140 * The difference here is that cycles must be avoided. If
3141 * node0 migrates to node1, then neither node1, nor anything
3142 * node1 migrates to can migrate to node0.
3144 * This function can run simultaneously with readers of
3145 * node_demotion[]. However, it can not run simultaneously
3146 * with itself. Exclusion is provided by memory hotplug events
3147 * being single-threaded.
3149 static void __set_migration_target_nodes(void)
3151 nodemask_t next_pass
= NODE_MASK_NONE
;
3152 nodemask_t this_pass
= NODE_MASK_NONE
;
3153 nodemask_t used_targets
= NODE_MASK_NONE
;
3157 * Avoid any oddities like cycles that could occur
3158 * from changes in the topology. This will leave
3159 * a momentary gap when migration is disabled.
3161 disable_all_migrate_targets();
3164 * Allocations go close to CPUs, first. Assume that
3165 * the migration path starts at the nodes with CPUs.
3167 next_pass
= node_states
[N_CPU
];
3169 this_pass
= next_pass
;
3170 next_pass
= NODE_MASK_NONE
;
3172 * To avoid cycles in the migration "graph", ensure
3173 * that migration sources are not future targets by
3174 * setting them in 'used_targets'. Do this only
3175 * once per pass so that multiple source nodes can
3176 * share a target node.
3178 * 'used_targets' will become unavailable in future
3179 * passes. This limits some opportunities for
3180 * multiple source nodes to share a destination.
3182 nodes_or(used_targets
, used_targets
, this_pass
);
3183 for_each_node_mask(node
, this_pass
) {
3184 int target_node
= establish_migrate_target(node
, &used_targets
);
3186 if (target_node
== NUMA_NO_NODE
)
3190 * Visit targets from this pass in the next pass.
3191 * Eventually, every node will have been part of
3192 * a pass, and will become set in 'used_targets'.
3194 node_set(target_node
, next_pass
);
3197 * 'next_pass' contains nodes which became migration
3198 * targets in this pass. Make additional passes until
3199 * no more migrations targets are available.
3201 if (!nodes_empty(next_pass
))
3206 * For callers that do not hold get_online_mems() already.
3208 static void set_migration_target_nodes(void)
3211 __set_migration_target_nodes();
3216 * This leaves migrate-on-reclaim transiently disabled between
3217 * the MEM_GOING_OFFLINE and MEM_OFFLINE events. This runs
3218 * whether reclaim-based migration is enabled or not, which
3219 * ensures that the user can turn reclaim-based migration at
3220 * any time without needing to recalculate migration targets.
3222 * These callbacks already hold get_online_mems(). That is why
3223 * __set_migration_target_nodes() can be used as opposed to
3224 * set_migration_target_nodes().
3226 static int __meminit
migrate_on_reclaim_callback(struct notifier_block
*self
,
3227 unsigned long action
, void *_arg
)
3229 struct memory_notify
*arg
= _arg
;
3232 * Only update the node migration order when a node is
3233 * changing status, like online->offline. This avoids
3234 * the overhead of synchronize_rcu() in most cases.
3236 if (arg
->status_change_nid
< 0)
3237 return notifier_from_errno(0);
3240 case MEM_GOING_OFFLINE
:
3242 * Make sure there are not transient states where
3243 * an offline node is a migration target. This
3244 * will leave migration disabled until the offline
3245 * completes and the MEM_OFFLINE case below runs.
3247 disable_all_migrate_targets();
3252 * Recalculate the target nodes once the node
3253 * reaches its final state (online or offline).
3255 __set_migration_target_nodes();
3257 case MEM_CANCEL_OFFLINE
:
3259 * MEM_GOING_OFFLINE disabled all the migration
3260 * targets. Reenable them.
3262 __set_migration_target_nodes();
3264 case MEM_GOING_ONLINE
:
3265 case MEM_CANCEL_ONLINE
:
3269 return notifier_from_errno(0);
3273 * React to hotplug events that might affect the migration targets
3274 * like events that online or offline NUMA nodes.
3276 * The ordering is also currently dependent on which nodes have
3277 * CPUs. That means we need CPU on/offline notification too.
3279 static int migration_online_cpu(unsigned int cpu
)
3281 set_migration_target_nodes();
3285 static int migration_offline_cpu(unsigned int cpu
)
3287 set_migration_target_nodes();
3291 static int __init
migrate_on_reclaim_init(void)
3295 ret
= cpuhp_setup_state_nocalls(CPUHP_MM_DEMOTION_DEAD
, "mm/demotion:offline",
3296 NULL
, migration_offline_cpu
);
3298 * In the unlikely case that this fails, the automatic
3299 * migration targets may become suboptimal for nodes
3300 * where N_CPU changes. With such a small impact in a
3301 * rare case, do not bother trying to do anything special.
3304 ret
= cpuhp_setup_state(CPUHP_AP_MM_DEMOTION_ONLINE
, "mm/demotion:online",
3305 migration_online_cpu
, NULL
);
3308 hotplug_memory_notifier(migrate_on_reclaim_callback
, 100);
3311 late_initcall(migrate_on_reclaim_init
);
3312 #endif /* CONFIG_HOTPLUG_CPU */