memory cgroup enhancements: fix zone handling in try_to_free_mem_cgroup_page

Because NODE_DATA(node)->node_zonelists[] is guaranteed to contain all
necessary zones, it is not necessary to use for_each_online_node.

And this for_each_online_node() makes reclaim routine start always
from node 0. This is not good. This patch makes reclaim start from
caller's node and just use usual (default) zonelist order.

[akpm@linux-foundation.org: fix warning]
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: Pavel Emelianov <xemul@openvz.org>
Cc: Paul Menage <menage@google.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Kirill Korotaev <dev@sw.ru>
Cc: Herbert Poetzl <herbert@13thfloor.at>
Cc: David Rientjes <rientjes@google.com>
Cc: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/vmscan.c

@@ -1365,15 +1365,12 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
 		.mem_cgroup = mem_cont,
 		.isolate_pages = mem_cgroup_isolate_pages,
 	};
-	int node;
 	struct zone **zones;
 	int target_zone = gfp_zone(GFP_HIGHUSER_MOVABLE);
 
-	for_each_online_node(node) {
-		zones = NODE_DATA(node)->node_zonelists[target_zone].zones;
-		if (do_try_to_free_pages(zones, sc.gfp_mask, &sc))
-			return 1;
-	}
+	zones = NODE_DATA(numa_node_id())->node_zonelists[target_zone].zones;
+	if (do_try_to_free_pages(zones, sc.gfp_mask, &sc))
+		return 1;
 	return 0;
 }
 #endif