linux-kernel - Re: [PATCH] memcg: cleanup root memcg checks

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Message-ID: <YDYc0WHOcCbwOS8h@dhcp22.suse.cz>
Date:   Wed, 24 Feb 2021 10:30:57 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     Shakeel Butt <shakeelb@...gle.com>
Cc:     Johannes Weiner <hannes@...xchg.org>, Roman Gushchin <guro@...com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        cgroups@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] memcg: cleanup root memcg checks

On Tue 23-02-21 12:56:25, Shakeel Butt wrote:
> Replace the implicit checking of root memcg with explicit root memcg
> checking i.e. !css->parent with mem_cgroup_is_root().
>
> Signed-off-by: Shakeel Butt <shakeelb@...gle.com>

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

Thanks!

> ---
>  mm/memcontrol.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index dcb5665aeb69..79046ad3eec0 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -4141,7 +4141,7 @@ static int mem_cgroup_swappiness_write(struct cgroup_subsys_state *css,
>  	if (val > 100)
>  		return -EINVAL;
>  
> -	if (css->parent)
> +	if (!mem_cgroup_is_root(memcg))
>  		memcg->swappiness = val;
>  	else
>  		vm_swappiness = val;
> @@ -4491,7 +4491,7 @@ static int mem_cgroup_oom_control_write(struct cgroup_subsys_state *css,
>  	struct mem_cgroup *memcg = mem_cgroup_from_css(css);
>  
>  	/* cannot set to root cgroup and only 0 and 1 are allowed */
> -	if (!css->parent || !((val == 0) || (val == 1)))
> +	if (mem_cgroup_is_root(memcg) || !((val == 0) || (val == 1)))
>  		return -EINVAL;
>  
>  	memcg->oom_kill_disable = val;
> -- 
> 2.30.0.617.g56c4b15f3c-goog

-- 
Michal Hocko
SUSE Labs