mm/compaction.c: avoid double mem_cgroup_del_lru()

del_page_from_lru_list() already called mem_cgroup_del_lru().  So we must
not call it again.  It adds unnecessary overhead.

It was not a runtime bug because the TestClearPageCgroupAcctLRU() early in
mem_cgroup_del_lru_list() will prevent any double-deletion, etc.
Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/compaction.c

@@ -279,7 +279,6 @@ static unsigned long isolate_migratepages(struct zone *zone,
 		/* Successfully isolated */
 		del_page_from_lru_list(zone, page, page_lru(page));
 		list_add(&page->lru, migratelist);
-		mem_cgroup_del_lru(page);
 		cc->nr_migratepages++;
 
 		/* Avoid isolating too much */