Re: [PATCH v3 6/6] memcg: avoid dangling reference count in creation failure.

[Michal Hocko <mhocko@suse.cz>]

On Mon 21-01-13 15:13:33, Glauber Costa wrote:
> When use_hierarchy is enabled, we acquire an extra reference count
> in our parent during cgroup creation. We don't release it, though,
> if any failure exist in the creation process.
> 
> Signed-off-by: Glauber Costa <glommer@parallels.com>
> Reported-by: Michal Hocko <mhocko@suse>

If you put this one to the head of the series we can backport it to
stable which is preferred, although nobody have seen this as a problem.

> ---
>  mm/memcontrol.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 5a247de..3949123 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -6167,6 +6167,8 @@ mem_cgroup_css_online(struct cgroup *cont)
>  		 * call __mem_cgroup_free, so return directly
>  		 */
>  		mem_cgroup_put(memcg);
> +		if (parent->use_hierarchy)
> +			mem_cgroup_put(parent);
>  	}
>  	return error;
>  }
> -- 
> 1.8.1
> 
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-- 
Michal Hocko
SUSE Labs

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