From d8ad30559715ce97afb7d1a93a12fd90e8fff312 Mon Sep 17 00:00:00 2001
From: Hugh Dickins <hughd@google.com>
Date: Thu, 23 Jan 2014 15:53:32 -0800
Subject: [PATCH] mm/memcg: iteration skip memcgs not yet fully initialized
It is surprising that the mem_cgroup iterator can return memcgs which
have not yet been fully initialized. By accident (or trial and error?)
this appears not to present an actual problem; but it may be better to
prevent such surprises, by skipping memcgs not yet online.
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Tejun Heo <tj@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: <stable@vger.kernel.org> [3.12+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
mm/memcontrol.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index aa66cc4c9e79b..9537e1389ee6a 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1119,10 +1119,8 @@ static struct mem_cgroup *__mem_cgroup_iter_next(struct mem_cgroup *root,
* protected by css_get and the tree walk is rcu safe.
*/
if (next_css) {
- struct mem_cgroup *mem = mem_cgroup_from_css(next_css);
-
- if (css_tryget(&mem->css))
- return mem;
+ if ((next_css->flags & CSS_ONLINE) && css_tryget(next_css))
+ return mem_cgroup_from_css(next_css);
else {
prev_css = next_css;
goto skip_node;
--
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