From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752861Ab1ARRHE (ORCPT ); Tue, 18 Jan 2011 12:07:04 -0500 Received: from zene.cmpxchg.org ([85.214.230.12]:46971 "EHLO zene.cmpxchg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752220Ab1ARRHD (ORCPT ); Tue, 18 Jan 2011 12:07:03 -0500 From: Johannes Weiner To: Andrew Morton Cc: Mel Gorman , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [patch] mm: compaction: prevent division-by-zero during user-requested compaction Date: Tue, 18 Jan 2011 18:06:52 +0100 Message-Id: <1295370412-2645-1-git-send-email-hannes@cmpxchg.org> X-Mailer: git-send-email 1.7.3.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Up until '3e7d344 mm: vmscan: reclaim order-0 and use compaction instead of lumpy reclaim', compaction skipped calculating the fragmentation index of a zone when compaction was explicitely requested through the procfs knob. However, when compaction_suitable was introduced, it did not come with an extra check for order == -1, set on explicit compaction requests, and passed this order on to the fragmentation index calculation, where it overshifts the number of requested pages, leading to a division by zero. This patch makes sure that order == -1 is recognized as the flag it is rather than passing it along as valid order parameter. Signed-off-by: Johannes Weiner --- mm/compaction.c | 3 +++ 1 files changed, 3 insertions(+), 0 deletions(-) diff --git a/mm/compaction.c b/mm/compaction.c index 6d592a0..114c145 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -453,6 +453,9 @@ unsigned long compaction_suitable(struct zone *zone, int order) if (!zone_watermark_ok(zone, 0, watermark, 0, 0)) return COMPACT_SKIPPED; + if (order == -1) + return COMPACT_CONTINUE; + /* * fragmentation index determines if allocation failures are due to * low memory or external fragmentation -- 1.7.3.4