Re: [PATCH v2 1/3] mm: memcontrol: fix swap counter leak on swapout from offline cgroup

[Johannes Weiner]

On Tue, Aug 02, 2016 at 06:00:48PM +0300, Vladimir Davydov wrote:
> An offline memory cgroup might have anonymous memory or shmem left
> charged to it and no swap. Since only swap entries pin the id of an
> offline cgroup, such a cgroup will have no id and so an attempt to
> swapout its anon/shmem will not store memory cgroup info in the swap
> cgroup map. As a result, memcg->swap or memcg->memsw will never get
> uncharged from it and any of its ascendants.
> 
> Fix this by always charging swapout to the first ancestor cgroup that
> hasn't released its id yet.
> 
> Fixes: 73f576c04b941 ("mm: memcontrol: fix cgroup creation failure after many small jobs")
> Signed-off-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx>	[3.19+]

Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>