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-rw-r--r--mm/swap_state.c11
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;