linux-kernel - Re: [PATCH] memcontrol: rcu_read_lock() to protect mm_match

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Date:	Fri, 21 Nov 2008 19:32:10 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Lai Jiangshan <laijs@...fujitsu.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Paul Menage <menage@...gle.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux Containers <containers@...ts.linux-foundation.org>
Subject: Re: [PATCH] memcontrol: rcu_read_lock() to protect
 mm_match_cgroup()

On Fri, 21 Nov 2008 16:49:43 +0800
Lai Jiangshan <laijs@...fujitsu.com> wrote:

> 
> mm_match_cgroup() calls cgroup_subsys_state().
> 
> we must use rcu_read_lock() to protect cgroup_subsys_state().
> 
Thanks,
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>

> Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>
> ---
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 1fbe14d..ce89ff0 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -47,8 +47,15 @@ int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem);
>  
>  extern struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p);
>  
> -#define mm_match_cgroup(mm, cgroup)	\
> -	((cgroup) == mem_cgroup_from_task((mm)->owner))
> +static inline
> +int mm_match_cgroup(const struct mm_struct *mm, const struct mem_cgroup *cgroup)
> +{
> +	struct mem_cgroup *mem;
> +	rcu_read_lock();
> +	mem = mem_cgroup_from_task((mm)->owner);
> +	rcu_read_unlock();
> +	return cgroup == mem;
> +}
>  
>  extern int
>  mem_cgroup_prepare_migration(struct page *page, struct page *newpage);
> 
> 

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