From: Minchan Kim <minchan@kernel.org>
Date: Fri, 28 Sep 2012 00:19:45 +0000 (+1000)
Subject: mm-compaction-acquire-the-zone-lru_lock-as-late-as-possible-fix
X-Git-Tag: next-20121003~1^2~243
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=7fd99e01eff60c3b655d66eee2a2950f7a94ab28;p=karo-tx-linux.git

mm-compaction-acquire-the-zone-lru_lock-as-late-as-possible-fix

augment comment

Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/mm/compaction.c b/mm/compaction.c
index a0c1a08c4172..7d96f8b45aa8 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -415,7 +415,8 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc,
 		 * if PageLRU is set) but the lock is not necessarily taken
 		 * here and it is wasteful to take it just to check transhuge.
 		 * Check transhuge without lock and skip if it's either a
-		 * transhuge or hugetlbfs page.
+		 * transhuge or hugetlbfs page because calling compound_order()
+		 * requires lru_lock to exclude isolation and splitting.
 		 */
 		if (PageTransHuge(page)) {
 			if (!locked)