[PATCH] mm: memcontrol: Pass NULL memcg for oom_badness() check.

[Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>]

Currently, mem_cgroup_out_of_memory() is calling
oom_scan_process_thread(&oc, task, totalpages) which includes
a call to oom_unkillable_task(task, NULL, NULL) and then is
calling oom_badness(task, memcg, NULL, totalpages) which includes
a call to oom_unkillable_task(task, memcg, NULL).

Since for_each_mem_cgroup_tree() iterates on only tasks from the given
memcg hierarchy, there is no point with passing non-NULL memcg argument
to oom_unkillable_task() via oom_badness().

Replace memcg argument with NULL in order to save a call to
task_in_mem_cgroup(task, memcg) in oom_unkillable_task()
which is always true.

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
---
 mm/memcontrol.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index ae8b81c..3c96dd3 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1290,7 +1290,7 @@ static void mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask,
 			case OOM_SCAN_OK:
 				break;
 			};
-			points = oom_badness(task, memcg, NULL, totalpages);
+			points = oom_badness(task, NULL, NULL, totalpages);
 			if (!points || points < chosen_points)
 				continue;
 			/* Prefer thread group leaders for display purposes */
-- 
1.8.3.1

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