From f6789593d5cea42a4ecb1cbeab6a23ade5ebbba7 Mon Sep 17 00:00:00 2001 From: Maxim Patlasov Date: Wed, 30 Jul 2014 16:08:21 -0700 Subject: mm/page-writeback.c: fix divide by zero in bdi_dirty_limits() Under memory pressure, it is possible for dirty_thresh, calculated by global_dirty_limits() in balance_dirty_pages(), to equal zero. Then, if strictlimit is true, bdi_dirty_limits() tries to resolve the proportion: bdi_bg_thresh : bdi_thresh = background_thresh : dirty_thresh by dividing by zero. Signed-off-by: Maxim Patlasov Acked-by: Rik van Riel Cc: Michal Hocko Cc: KOSAKI Motohiro Cc: Wu Fengguang Cc: Johannes Weiner Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/page-writeback.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 518e2c3f4c7..e0c943014eb 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -1306,9 +1306,9 @@ static inline void bdi_dirty_limits(struct backing_dev_info *bdi, *bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh); if (bdi_bg_thresh) - *bdi_bg_thresh = div_u64((u64)*bdi_thresh * - background_thresh, - dirty_thresh); + *bdi_bg_thresh = dirty_thresh ? div_u64((u64)*bdi_thresh * + background_thresh, + dirty_thresh) : 0; /* * In order to avoid the stacked BDI deadlock we need -- cgit v1.2.3-18-g5258