From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail6.bemta12.messagelabs.com (mail6.bemta12.messagelabs.com [216.82.250.247]) by kanga.kvack.org (Postfix) with ESMTP id 719056B0012 for ; Mon, 30 May 2011 08:38:37 -0400 (EDT) Date: Mon, 30 May 2011 14:38:31 +0200 From: Michal Hocko Subject: [PATCH] mm: fix special case -1 order check in compact_finished Message-ID: <20110530123831.GG20166@tiehlicka.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Mel Gorman , linux-mm@kvack.org, LKML 56de7263 (mm: compaction: direct compact when a high-order allocation fails) introduced a check for cc->order == -1 in compact_finished. We should continue compacting in that case because the request came from userspace and there is no particular order to compact for. The check is, however, done after zone_watermark_ok which uses order as a right hand argument for shifts. Not only watermark check is pointless if we can break out without it but it also uses 1 << -1 which is not well defined (at least from C standard). Let's move the -1 check above zone_watermark_ok. Signed-off-by: Michal Hocko Cc: Mel Gorman --- compaction.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) Index: linus_tree/mm/compaction.c =================================================================== --- linus_tree.orig/mm/compaction.c 2011-05-30 14:19:58.000000000 +0200 +++ linus_tree/mm/compaction.c 2011-05-30 14:20:40.000000000 +0200 @@ -420,13 +420,6 @@ static int compact_finished(struct zone if (cc->free_pfn <= cc->migrate_pfn) return COMPACT_COMPLETE; - /* Compaction run is not finished if the watermark is not met */ - watermark = low_wmark_pages(zone); - watermark += (1 << cc->order); - - if (!zone_watermark_ok(zone, cc->order, watermark, 0, 0)) - return COMPACT_CONTINUE; - /* * order == -1 is expected when compacting via * /proc/sys/vm/compact_memory @@ -434,6 +427,13 @@ static int compact_finished(struct zone if (cc->order == -1) return COMPACT_CONTINUE; + /* Compaction run is not finished if the watermark is not met */ + watermark = low_wmark_pages(zone); + watermark += (1 << cc->order); + + if (!zone_watermark_ok(zone, cc->order, watermark, 0, 0)) + return COMPACT_CONTINUE; + /* Direct compactor: Is a suitable page free? */ for (order = cc->order; order < MAX_ORDER; order++) { /* Job done if page is free of the right migratetype */ -- Michal Hocko SUSE Labs SUSE LINUX s.r.o. Lihovarska 1060/12 190 00 Praha 9 Czech Republic -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org