[PATCH] mm: vmscan: ensure reclaiming pages on the lru lists of zone

[Hillf Danton]

It is possible that the memcg input into shrink_mem_cgroup_zone() in
each round is not NULL, and the loop terminates at NULL case. And there
is chance that pages on the lru lists of zone are not reclaimed.

Mem cgroup iteration is refactored a bit to ensure the NULL case is also
input into the function.

Signed-off-by: Hillf Danton <dhillf@xxxxxxxxx>
---

--- a/mm/vmscan.c	Sat Jan 14 14:02:20 2012
+++ b/mm/vmscan.c	Sun Jan 22 10:09:32 2012
@@ -2142,14 +2142,14 @@ static void shrink_zone(int priority, st
 		.zone = zone,
 		.priority = priority,
 	};
-	struct mem_cgroup *memcg;
+	struct mem_cgroup_zone mz = {
+		.zone = zone,
+	};
+	struct mem_cgroup *memcg = NULL;

-	memcg = mem_cgroup_iter(root, NULL, &reclaim);
 	do {
-		struct mem_cgroup_zone mz = {
-			.mem_cgroup = memcg,
-			.zone = zone,
-		};
+		memcg = mem_cgroup_iter(root, memcg, &reclaim);
+		mz.mem_cgroup = memcg,

 		shrink_mem_cgroup_zone(priority, &mz, sc);
 		/*
@@ -2166,7 +2166,6 @@ static void shrink_zone(int priority, st
 			mem_cgroup_iter_break(root, memcg);
 			break;
 		}
-		memcg = mem_cgroup_iter(root, memcg, &reclaim);
 	} while (memcg);
 }
--
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