1 files changed, 11 insertions, 0 deletions

diff --git a/mm/migrate.c b/mm/migrate.c
index 42a3d24d1107..b114635962dc 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -600,6 +600,17 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
         if (PageAnon(page)) {
                 rcu_read_lock();
                 rcu_locked = 1;
+
+                /*
+                 * If the page has no mappings any more, just bail. An
+                 * unmapped anon page is likely to be freed soon but worse,
+                 * it's possible its anon_vma disappeared between when
+                 * the page was isolated and when we reached here while
+                 * the RCU lock was not held
+                 */
+                if (!page_mapped(page))
+                        goto rcu_unlock;
+
                 anon_vma = page_anon_vma(page);
                 atomic_inc(&anon_vma->external_refcount);
         }