linux-kernel - Re: [patch 5/8] memcg: remove unnecessary !mm check from try_get_mem_cgroup_from

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Message-ID: <20140210142911.GJ7117@dhcp22.suse.cz>
Date:	Mon, 10 Feb 2014 15:29:11 +0100
From:	Michal Hocko <mhocko@...e.cz>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [patch 5/8] memcg: remove unnecessary !mm check from
 try_get_mem_cgroup_from_mm()

On Fri 07-02-14 12:04:22, Johannes Weiner wrote:
> Users pass either a mm that has been established under task lock, or
> use a verified current->mm, which means the task can't be exiting.
> 
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>

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

> ---
>  mm/memcontrol.c | 7 -------
>  1 file changed, 7 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index e1d7f33227e4..689fffdee471 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1075,13 +1075,6 @@ struct mem_cgroup *try_get_mem_cgroup_from_mm(struct mm_struct *mm)
>  {
>  	struct mem_cgroup *memcg = NULL;
>  
> -	if (!mm)
> -		return NULL;
> -	/*
> -	 * Because we have no locks, mm->owner's may be being moved to other
> -	 * cgroup. We use css_tryget() here even if this looks
> -	 * pessimistic (rather than adding locks here).
> -	 */
>  	rcu_read_lock();
>  	do {
>  		memcg = mem_cgroup_from_task(rcu_dereference(mm->owner));
> -- 
> 1.8.5.3
> 

-- 
Michal Hocko
SUSE Labs
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