mm: compaction: fix special case -1 order checks
authorMichal Hocko <mhocko@suse.cz>
Wed, 15 Jun 2011 22:08:25 +0000 (15:08 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Thu, 16 Jun 2011 03:04:00 +0000 (20:04 -0700)
commit3957c7768e5ea02fd3345176ddd340f820e5d285
treeb3cbefeea3ac3adea0ca9d49e140503c9e5754b6
parent5f1a19070b16c20cdc71ed0e981bfa19f8f6a4ee
mm: compaction: fix special case -1 order checks

Commit 56de7263fcf3 ("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.  Similar check has been added by 82478fb7 (mm: compaction:
prevent division-by-zero during user-requested compaction) for
compaction_suitable.

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.

[minchan.kim@gmail.com> - caught compaction_suitable]
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Cc: Mel Gorman <mgorman@suse.de>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hioryu@jp.fujitsu.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/compaction.c