From: Johannes Weiner <hannes@cmpxchg.org>
Date: Mon, 7 Apr 2014 22:37:42 +0000 (-0700)
Subject: memcg: remove unnecessary !mm check from try_get_mem_cgroup_from_mm()
X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=03583f1a631c;p=openwrt%2Fstaging%2Fblogic.git

memcg: remove unnecessary !mm check from try_get_mem_cgroup_from_mm()

Users pass either a mm that has been established under task lock, or use
a verified current->mm, which means the task can't be exiting.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 8d6cedd16f8d..c3b674f9774f 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1075,13 +1075,6 @@ struct mem_cgroup *try_get_mem_cgroup_from_mm(struct mm_struct *mm)
 {
 	struct mem_cgroup *memcg = NULL;
 
-	if (!mm)
-		return NULL;
-	/*
-	 * Because we have no locks, mm->owner's may be being moved to other
-	 * cgroup. We use css_tryget() here even if this looks
-	 * pessimistic (rather than adding locks here).
-	 */
 	rcu_read_lock();
 	do {
 		memcg = mem_cgroup_from_task(rcu_dereference(mm->owner));