Re: [PATCH] memcg: lost css_put in memcg_expand_shrinker_maps()

[Roman Gushchin <guro@fb.com>]

On Tue, Feb 11, 2020 at 02:20:10PM +0300, Vasily Averin wrote:
> for_each_mem_cgroup() increases css reference counter for memory cgroup
> and requires to use mem_cgroup_iter_break() if the walk is cancelled.
> 
> Cc: stable@vger.kernel.org
> Fixes commit 0a4465d34028("mm, memcg: assign memcg-aware shrinkers bitmap to memcg")
> 
> Signed-off-by: Vasily Averin <vvs@virtuozzo.com>

Reviewed-by: Roman Gushchin <guro@fb.com>

Thank you!

> ---
>  mm/memcontrol.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 6c83cf4..e2da615 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -409,8 +409,10 @@ int memcg_expand_shrinker_maps(int new_id)
>  		if (mem_cgroup_is_root(memcg))
>  			continue;
>  		ret = memcg_expand_one_shrinker_map(memcg, size, old_size);
> -		if (ret)
> +		if (ret) {
> +			mem_cgroup_iter_break(NULL, memcg);
>  			goto unlock;
> +		}
>  	}
>  unlock:
>  	if (!ret)
> -- 
> 1.8.3.1
>