mm: fix lazyfree BUG_ON check in try_to_unmap_one()

If a page is swapbacked, it means it should be in swapcache in try_to_unmap_one's path. If a page is !swapbacked, it mean it shouldn't be in swapcache in try_to_unmap_one's path. Check both two cases all at once and if it fails, warn and return SWAP_FAIL. Such bug never mean we should shut down the kernel. [[email protected]: do not use VM_WARN_ON_ONCE as if condition[ Link: http://lkml.kernel.org/r/20170309060226.GB854@bbox Link: http://lkml.kernel.org/r/20170307055551.GC29458@bbox Signed-off-by: Minchan Kim <[email protected]> Suggested-by: Johannes Weiner <[email protected]> Acked-by: Michal Hocko <[email protected]> Acked-by: Johannes Weiner <[email protected]> Cc: Shaohua Li <[email protected]> Cc: Hillf Danton <[email protected]> Cc: Hugh Dickins <[email protected]> Cc: Rik van Riel <[email protected]> Cc: Mel Gorman <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
mrcsosa · May 3, 2017 · eb94a87 · eb94a87
1 parent 802a3a9
commit eb94a87
Showing 1 changed file with 6 additions and 2 deletions.
diff --git a/mm/rmap.c b/mm/rmap.c
@@ -1418,8 +1418,12 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
 			 * Store the swap location in the pte.
 			 * See handle_pte_fault() ...
 			 */
-			VM_BUG_ON_PAGE(!PageSwapCache(page) && PageSwapBacked(page),
-				page);
+			if (unlikely(PageSwapBacked(page) != PageSwapCache(page))) {
+				WARN_ON_ONCE(1);
+				ret = SWAP_FAIL;
+				page_vma_mapped_walk_done(&pvmw);
+				break;
+			}
 
 			/* MADV_FREE page check */
 			if (!PageSwapBacked(page)) {