linux-kernel - Re: [PATCH] mm, memcg: Handle cgroup_disable=memory when getting memcg protection

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Message-ID: <20190201071203.GD11599@dhcp22.suse.cz>
Date:   Fri, 1 Feb 2019 08:12:03 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Chris Down <chris@...isdown.name>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Johannes Weiner <hannes@...xchg.org>,
        Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org,
        cgroups@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] mm, memcg: Handle cgroup_disable=memory when getting
 memcg protection

On Thu 31-01-19 23:57:11, Chris Down wrote:
> memcg is NULL if we have CONFIG_MEMCG set, but cgroup_disable=memory on
> the kernel command line.
> 
> Fixes: 8a907cdf0177ab40 ("mm, memcg: proportional memory.{low,min} reclaim")

JFYI this is not a valid sha1. It is from linux next and it will change
with the next linux-next release.

Btw. I still didn't get to look at your patch and I am unlikely to do so
today. I will be offline next week but I will try to get to it after I
get back.

> Reported-by: Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
> Signed-off-by: Chris Down <chris@...isdown.name>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Johannes Weiner <hannes@...xchg.org>
> Cc: Tejun Heo <tj@...nel.org>
> Cc: linux-kernel@...r.kernel.org
> Cc: cgroups@...r.kernel.org
> Cc: linux-mm@...ck.org
> ---
>  include/linux/memcontrol.h | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 290cfbfd60cd..49742489aa56 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -335,6 +335,9 @@ static inline bool mem_cgroup_disabled(void)
>  
>  static inline unsigned long mem_cgroup_protection(struct mem_cgroup *memcg)
>  {
> +	if (mem_cgroup_disabled())
> +		return 0;
> +
>  	return max(READ_ONCE(memcg->memory.emin), READ_ONCE(memcg->memory.elow));
>  }
>  
> -- 
> 2.20.1

-- 
Michal Hocko
SUSE Labs