3.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: Hugh Dickins <hughd@xxxxxxxxxx>
commit d8ad30559715ce97afb7d1a93a12fd90e8fff312 upstream.
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@xxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/memcontrol.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1081,10 +1081,8 @@ skip_node:
* 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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