diff --git a/mm/vmscan.c b/mm/vmscan.c
index 41a3da3..1618058 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -377,8 +377,8 @@
 
 int remove_mapping(struct address_space *mapping, struct page *page)
 {
-	if (!mapping)
-		return 0;		/* truncate got there first */
+	BUG_ON(!PageLocked(page));
+	BUG_ON(mapping != page_mapping(page));
 
 	write_lock_irq(&mapping->tree_lock);
 
@@ -547,7 +547,7 @@
 				goto free_it;
 		}
 
-		if (!remove_mapping(mapping, page))
+		if (!mapping || !remove_mapping(mapping, page))
 			goto keep_locked;
 
 free_it: