From: Maxim Patlasov <MPatlasov@xxxxxxxxxxxxx> 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 <mpatlasov@xxxxxxxxxxxxx> Acked-by: Rik van Riel <riel@xxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxx> Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> Cc: Wu Fengguang <fengguang.wu@xxxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/page-writeback.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff -puN mm/page-writeback.c~mm-page-writebackc-fix-divide-by-zero-in-bdi_dirty_limits mm/page-writeback.c --- a/mm/page-writeback.c~mm-page-writebackc-fix-divide-by-zero-in-bdi_dirty_limits +++ a/mm/page-writeback.c @@ -1306,9 +1306,9 @@ static inline void bdi_dirty_limits(stru *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 _ -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html