memcg: fix kmem_account_flags check in memcg_can_account_kmem()
authorVladimir Davydov <vdavydov@parallels.com>
Tue, 21 Jan 2014 23:49:41 +0000 (15:49 -0800)
committerLinus Torvalds <torvalds@linux-foundation.org>
Wed, 22 Jan 2014 00:19:45 +0000 (16:19 -0800)
commit1c98dd905ddb7552f13a3f06aa0bd9ef6affeeb7
tree6c977f0566e6ef99ac45547a3c81017a575cd73c
parentb2f3eebe7a8ef6cd4e2ea088ac7f613793f6cad6
memcg: fix kmem_account_flags check in memcg_can_account_kmem()

We should start kmem accounting for a memory cgroup only after both its
kmem limit is set (KMEM_ACCOUNTED_ACTIVE) and related call sites are
patched (KMEM_ACCOUNTED_ACTIVATED).  Currently memcg_can_account_kmem()
allows kmem accounting even if only one of the conditions is true.  Fix
it.

This means that a page might get charged by memcg_kmem_newpage_charge
which would see its static key patched already but
memcg_kmem_commit_charge would still see it unpatched and so the charge
won't be committed.  The result would be charge inconsistency
(page_cgroup not marked as PageCgroupUsed) and the charge would leak
because __memcg_kmem_uncharge_pages would ignore it.

[mhocko@suse.cz: augment changelog]
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Glauber Costa <glommer@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/memcontrol.c