From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lb0-f181.google.com (mail-lb0-f181.google.com [209.85.217.181]) by kanga.kvack.org (Postfix) with ESMTP id 06DF9900002 for ; Fri, 11 Jul 2014 04:18:35 -0400 (EDT) Received: by mail-lb0-f181.google.com with SMTP id p9so582839lbv.40 for ; Fri, 11 Jul 2014 01:18:35 -0700 (PDT) Received: from relay.parallels.com (relay.parallels.com. [195.214.232.42]) by mx.google.com with ESMTPS id ml6si3715380lbc.20.2014.07.11.01.18.34 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 11 Jul 2014 01:18:34 -0700 (PDT) Subject: [PATCH] mm/page-writeback.c: fix divide by zero in bdi_dirty_limits From: Maxim Patlasov Date: Fri, 11 Jul 2014 12:18:27 +0400 Message-ID: <20140711081656.15654.19946.stgit@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: akpm@linux-foundation.org Cc: riel@redhat.com, linux-kernel@vger.kernel.org, mhocko@suse.cz, linux-mm@kvack.org, kosaki.motohiro@jp.fujitsu.com, fengguang.wu@intel.com, jweiner@redhat.com 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 --- 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 518e2c3..e0c9430 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org