1 files changed, 11 insertions, 0 deletions

diff --git a/mm/swap_state.c b/mm/swap_state.c
index 71ce2d1ccbf7..ed91091d1e68 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -242,6 +242,17 @@ int add_to_swap(struct page *page)
                  * clear SWAP_HAS_CACHE flag.
                  */
                 goto fail;
+        /*
+         * Normally the page will be dirtied in unmap because its pte should be
+         * dirty. A special case is MADV_FREE page. The page'e pte could have
+         * dirty bit cleared but the page's SwapBacked bit is still set because
+         * clearing the dirty bit and SwapBacked bit has no lock protected. For
+         * such page, unmap will not set dirty bit for it, so page reclaim will
+         * not write the page out. This can cause data corruption when the page
+         * is swap in later. Always setting the dirty bit for the page solves
+         * the problem.
+         */
+        set_page_dirty(page);
 
         return 1;