Commit 3a981f48 authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds

memcg: fix use_hierarchy css_is_ancestor oops regression

If use_hierarchy is set, reclaim testing soon oopses in css_is_ancestor()
called from __mem_cgroup_same_or_subtree() called from page_referenced():
when processes are exiting, it's easy for mm_match_cgroup() to pass along
a NULL memcg coming from a NULL mm->owner.

Check for that in __mem_cgroup_same_or_subtree().  Return true or false?
False because we cannot know if it was in the hierarchy, but also false
because it's better not to count a reference from an exiting process.
Signed-off-by: default avatarHugh Dickins <hughd@google.com>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Acked-by: default avatarKonstantin Khlebnikov <khlebnikov@openvz.org>
Acked-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 61eafb00
...@@ -1148,7 +1148,7 @@ bool __mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg, ...@@ -1148,7 +1148,7 @@ bool __mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg,
{ {
if (root_memcg == memcg) if (root_memcg == memcg)
return true; return true;
if (!root_memcg->use_hierarchy) if (!root_memcg->use_hierarchy || !memcg)
return false; return false;
return css_is_ancestor(&memcg->css, &root_memcg->css); return css_is_ancestor(&memcg->css, &root_memcg->css);
} }
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment