1 files changed, 10 insertions, 1 deletions

diff --git a/mm/swapfile.c b/mm/swapfile.c
index f43601827607..9ce7f81c8abc 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -889,7 +889,16 @@ static int try_to_unuse(unsigned int type)
                         lock_page(page);
                         wait_on_page_writeback(page);
                 }
-                if (PageSwapCache(page))
+
+                /*
+                 * It is conceivable that a racing task removed this page from
+                 * swap cache just before we acquired the page lock at the top,
+                 * or while we dropped it in unuse_mm().  The page might even
+                 * be back in swap cache on another swap area: that we must not
+                 * delete, since it may not have been written out to swap yet.
+                 */
+                if (PageSwapCache(page) &&
+                    likely(page_private(page) == entry.val))
                         delete_from_swap_cache(page);
 
                 /*