From: Minchan Kim <minchan@xxxxxxxxxx> Subject: 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. [minchan@xxxxxxxxxx: 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 <minchan@xxxxxxxxxx> Suggested-by: Johannes Weiner <hannes@xxxxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Shaohua Li <shli@xxxxxx> Cc: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Rik van Riel <riel@xxxxxxxxxx> Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/rmap.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff -puN mm/rmap.c~mm-fix-lazyfree-bug-on-check-in-try_to_unmap_one mm/rmap.c --- a/mm/rmap.c~mm-fix-lazyfree-bug-on-check-in-try_to_unmap_one +++ a/mm/rmap.c @@ -1418,8 +1418,12 @@ static int try_to_unmap_one(struct page * 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)) { _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
