From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754611AbaHTMLj (ORCPT ); Wed, 20 Aug 2014 08:11:39 -0400 Received: from ip4-83-240-18-248.cust.nbox.cz ([83.240.18.248]:58886 "EHLO ip4-83-240-18-248.cust.nbox.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752483AbaHTLoJ (ORCPT ); Wed, 20 Aug 2014 07:44:09 -0400 From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Maxim Patlasov , Maxim Patlasov , Michal Hocko , KOSAKI Motohiro , Wu Fengguang , Johannes Weiner , Andrew Morton , Linus Torvalds , Jiri Slaby Subject: [PATCH 3.12 008/104] mm/page-writeback.c: fix divide by zero in bdi_dirty_limits() Date: Wed, 20 Aug 2014 13:42:31 +0200 Message-Id: X-Mailer: git-send-email 2.0.4 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Maxim Patlasov 3.12-stable review patch. If anyone has any objections, please let me know. =============== commit f6789593d5cea42a4ecb1cbeab6a23ade5ebbba7 upstream. 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 Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Jiri Slaby --- 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 d013dba21429..9f45f87a5859 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -1324,9 +1324,9 @@ 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 -- 2.0.4