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authorHugh Dickins <hughd@google.com>2022-02-15 05:38:47 +0300
committerMatthew Wilcox (Oracle) <willy@infradead.org>2022-02-17 19:59:40 +0300
commitb74355078b6554271371532a5daa3b1a3db620f9 (patch)
tree2db40bdaeeb1d7842560e2d06b51236d7beb5f3a /mm/rmap.c
parent2fbb0c10d1e8222604132b3a3f81bfd8345a44b6 (diff)
downloadlinux-b74355078b6554271371532a5daa3b1a3db620f9.tar.xz
mm/munlock: page migration needs mlock pagevec drained
Page migration of a VM_LOCKED page tends to fail, because when the old page is unmapped, it is put on the mlock pagevec with raised refcount, which then fails the freeze. At first I thought this would be fixed by a local mlock_page_drain() at the upper rmap_walk() level - which would have nicely batched all the munlocks of that page; but tests show that the task can too easily move to another cpu, leaving pagevec residue behind which fails the migration. So try_to_migrate_one() drain the local pagevec after page_remove_rmap() from a VM_LOCKED vma; and do the same in try_to_unmap_one(), whose TTU_IGNORE_MLOCK users would want the same treatment; and do the same in remove_migration_pte() - not important when successfully inserting a new page, but necessary when hoping to retry after failure. Any new pagevec runs the risk of adding a new way of stranding, and we might discover other corners where mlock_page_drain() or lru_add_drain() would now help. Signed-off-by: Hugh Dickins <hughd@google.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Diffstat (limited to 'mm/rmap.c')
-rw-r--r--mm/rmap.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/mm/rmap.c b/mm/rmap.c
index 5442a5c97a85..714bfdc72c7b 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1656,6 +1656,8 @@ discard:
* See Documentation/vm/mmu_notifier.rst
*/
page_remove_rmap(subpage, vma, PageHuge(page));
+ if (vma->vm_flags & VM_LOCKED)
+ mlock_page_drain(smp_processor_id());
put_page(page);
}
@@ -1930,6 +1932,8 @@ static bool try_to_migrate_one(struct page *page, struct vm_area_struct *vma,
* See Documentation/vm/mmu_notifier.rst
*/
page_remove_rmap(subpage, vma, PageHuge(page));
+ if (vma->vm_flags & VM_LOCKED)
+ mlock_page_drain(smp_processor_id());
put_page(page);
}