The patch titled
Subject: mm: page migration fix PageMlocked on migrated pages
has been added to the -mm tree. Its filename is
mm-page-migration-fix-pagemlocked-on-migrated-pages.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-page-migration-fix-pagemlocked-on-migrated-pages.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-page-migration-fix-pagemlocked-on-migrated-pages.patch
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From: Hugh Dickins <hughd@xxxxxxxxxx>
Subject: mm: page migration fix PageMlocked on migrated pages
Commit e6c509f85455 ("mm: use clear_page_mlock() in page_remove_rmap()")
in v3.7 inadvertently made mlock_migrate_page() impotent: page migration
unmaps the page from userspace before migrating, and that commit clears
PageMlocked on the final unmap, leaving mlock_migrate_page() with nothing
to do. Not a serious bug, the next attempt at reclaiming the page would
fix it up; but a betrayal of page migration's intent - the new page ought
to emerge as PageMlocked.
I don't see how to fix it for mlock_migrate_page() itself; but easily
fixed in remove_migration_pte(), by calling mlock_vma_page() when the vma
is VM_LOCKED - under pte lock as in try_to_unmap_one().
Delete mlock_migrate_page()? Not quite, it does still serve a purpose for
migrate_misplaced_transhuge_page(): where we could replace it by a test,
clear_page_mlock(), mlock_vma_page() sequence; but would that be an
improvement? mlock_migrate_page() is fairly lean, and let's make it
leaner by skipping the irq save/restore now clearly not needed.
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Sasha Levin <sasha.levin@xxxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/internal.h | 9 ++++-----
mm/migrate.c | 6 ++++--
2 files changed, 8 insertions(+), 7 deletions(-)
diff -puN mm/internal.h~mm-page-migration-fix-pagemlocked-on-migrated-pages mm/internal.h
--- a/mm/internal.h~mm-page-migration-fix-pagemlocked-on-migrated-pages
+++ a/mm/internal.h
@@ -295,20 +295,19 @@ extern unsigned int munlock_vma_page(str
extern void clear_page_mlock(struct page *page);
/*
- * mlock_migrate_page - called only from migrate_page_copy() to
- * migrate the Mlocked page flag; update statistics.
+ * mlock_migrate_page - called only from migrate_misplaced_transhuge_page()
+ * (because that does not go through the full procedure of migration ptes):
+ * to migrate the Mlocked page flag; update statistics.
*/
static inline void mlock_migrate_page(struct page *newpage, struct page *page)
{
if (TestClearPageMlocked(page)) {
- unsigned long flags;
int nr_pages = hpage_nr_pages(page);
- local_irq_save(flags);
+ /* Holding pmd lock, no change in irq context: __mod is safe */
__mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);
SetPageMlocked(newpage);
__mod_zone_page_state(page_zone(newpage), NR_MLOCK, nr_pages);
- local_irq_restore(flags);
}
}
diff -puN mm/migrate.c~mm-page-migration-fix-pagemlocked-on-migrated-pages mm/migrate.c
--- a/mm/migrate.c~mm-page-migration-fix-pagemlocked-on-migrated-pages
+++ a/mm/migrate.c
@@ -171,6 +171,9 @@ static int remove_migration_pte(struct p
else
page_add_file_rmap(new);
+ if (vma->vm_flags & VM_LOCKED)
+ mlock_vma_page(new);
+
/* No need to invalidate - it was non-present before */
update_mmu_cache(vma, addr, ptep);
unlock:
@@ -537,7 +540,6 @@ void migrate_page_copy(struct page *newp
cpupid = page_cpupid_xchg_last(page, -1);
page_cpupid_xchg_last(newpage, cpupid);
- mlock_migrate_page(newpage, page);
ksm_migrate_page(newpage, page);
/*
* Please do not reorder this without considering how mm/ksm.c's
@@ -1787,7 +1789,6 @@ fail_putback:
SetPageActive(page);
if (TestClearPageUnevictable(new_page))
SetPageUnevictable(page);
- mlock_migrate_page(page, new_page);
unlock_page(new_page);
put_page(new_page); /* Free it */
@@ -1829,6 +1830,7 @@ fail_putback:
goto fail_putback;
}
+ mlock_migrate_page(new_page, page);
mem_cgroup_migrate(page, new_page, false);
page_remove_rmap(page);
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
memcg-simplify-and-inline-__mem_cgroup_from_kmem-fix-2.patch
mm-documentation-undoc-non-linear-vmas.patch
mm-rmap-use-pte-lock-not-mmap_sem-to-set-pagemlocked.patch
mm-page-migration-fix-pagemlocked-on-migrated-pages.patch
mm-rename-mem_cgroup_migrate-to-mem_cgroup_replace_page.patch
mm-correct-a-couple-of-page-migration-comments.patch
mm-page-migration-use-the-put_new_page-whenever-necessary.patch
mm-page-migration-trylock-newpage-at-same-level-as-oldpage.patch
mm-page-migration-remove_migration_ptes-at-lockunlock-level.patch
mm-simplify-page-migrations-anon_vma-comment-and-flow.patch
mm-page-migration-use-migration-entry-for-swapcache-too.patch
mm-page-migration-avoid-touching-newpage-until-no-going-back.patch
mm-migrate-dirty-page-without-clear_page_dirty_for_io-etc.patch
mm-use-unsigned-int-for-page-order-fix-2.patch
mm-dont-split-thp-page-when-syscall-is-called-fix-4.patch
--
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