diff --git a/mm/filemap.c b/mm/filemap.c
index 61ba5e4..4ee2e99 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1029,6 +1029,9 @@
 				goto page_not_up_to_date;
 			if (!trylock_page(page))
 				goto page_not_up_to_date;
+			/* Did it get truncated before we got the lock? */
+			if (!page->mapping)
+				goto page_not_up_to_date_locked;
 			if (!mapping->a_ops->is_partially_uptodate(page,
 								desc, offset))
 				goto page_not_up_to_date_locked;