linux-kernel - Re: [PATCH 3/4] mm/memcg: retrieve parent memcg from css.parent

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Date:   Tue, 11 Jan 2022 09:43:07 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     Wei Yang <richard.weiyang@...il.com>
Cc:     hannes@...xchg.org, vdavydov.dev@...il.com,
        akpm@...ux-foundation.org, shakeelb@...gle.com, guro@...com,
        vbabka@...e.cz, willy@...radead.org, songmuchun@...edance.com,
        shy828301@...il.com, surenb@...gle.com,
        linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH 3/4] mm/memcg: retrieve parent memcg from css.parent

On Tue 11-01-22 01:03:01, Wei Yang wrote:
> The parent we get from page_counter is correct, while this is two
> different hierarchy.
> 
> Let's retrieve the parent memcg from css.parent just like parent_cs(),
> blkcg_parent(), etc.
> 
> Signed-off-by: Wei Yang <richard.weiyang@...il.com>

Acked-by: Michal Hocko <mhocko@...e.com>

> ---
>  include/linux/memcontrol.h | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 0c5c403f4be6..12bf443f7b14 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -886,9 +886,7 @@ static inline struct mem_cgroup *lruvec_memcg(struct lruvec *lruvec)
>   */
>  static inline struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *memcg)
>  {
> -	if (!memcg->memory.parent)
> -		return NULL;
> -	return mem_cgroup_from_counter(memcg->memory.parent, memory);
> +	return mem_cgroup_from_css(memcg->css.parent);
>  }
>  
>  static inline bool mem_cgroup_is_descendant(struct mem_cgroup *memcg,
> -- 
> 2.33.1

-- 
Michal Hocko
SUSE Labs