linux-kernel - Re: [PATCH 2/2] mm: vmpressure: use mem_cgroup_is

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Message-ID: <20200212082346.GB11353@dhcp22.suse.cz>
Date:   Wed, 12 Feb 2020 09:23:46 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Yang Shi <yang.shi@...ux.alibaba.com>
Cc:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] mm: vmpressure: use mem_cgroup_is_root API

On Tue 11-02-20 13:24:09, Yang Shi wrote:
> Use mem_cgroup_is_root() API to check if memcg is root memcg instead of
> open coding.

Yes, the direct use outside of memcontrol.c should be really an
exception. The only other similar case is cgwb_bdi_init and there is no
easy way to replace - except for adding a helper which is not worth it.

> Signed-off-by: Yang Shi <yang.shi@...ux.alibaba.com>

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

Thanks!

> ---
>  mm/vmpressure.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/vmpressure.c b/mm/vmpressure.c
> index 0590f00..d69019f 100644
> --- a/mm/vmpressure.c
> +++ b/mm/vmpressure.c
> @@ -280,7 +280,7 @@ void vmpressure(gfp_t gfp, struct mem_cgroup *memcg, bool tree,
>  		enum vmpressure_levels level;
>  
>  		/* For now, no users for root-level efficiency */
> -		if (!memcg || memcg == root_mem_cgroup)
> +		if (!memcg || mem_cgroup_is_root(memcg))
>  			return;
>  
>  		spin_lock(&vmpr->sr_lock);
> -- 
> 1.8.3.1
> 

-- 
Michal Hocko
SUSE Labs