linux-kernel - Re: [RFC][PATCH 2/7] memcg: don't use mem_cgroup

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Date:	Wed, 3 Apr 2013 17:31:33 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Li Zefan <lizefan@...wei.com>
Cc:	linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>,
	Cgroups <cgroups@...r.kernel.org>, Tejun Heo <tj@...nel.org>,
	Glauber Costa <glommer@...allels.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Johannes Weiner <hannes@...xchg.org>
Subject: Re: [RFC][PATCH 2/7] memcg: don't use mem_cgroup_get() when creating
 a kmemcg cache

On Wed 03-04-13 17:12:21, Li Zefan wrote:
> Use css_get()/css_put() instead of mem_cgroup_get()/mem_cgroup_put().
> 
> Signed-off-by: Li Zefan <lizefan@...wei.com>
> ---
>  mm/memcontrol.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 43ca91d..dafacb8 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -3191,7 +3191,7 @@ void memcg_release_cache(struct kmem_cache *s)
>  	list_del(&s->memcg_params->list);
>  	mutex_unlock(&memcg->slab_caches_mutex);
>  
> -	mem_cgroup_put(memcg);
> +	css_put(&memcg->css);
>  out:
>  	kfree(s->memcg_params);
>  }
> @@ -3350,16 +3350,18 @@ static struct kmem_cache *memcg_create_kmem_cache(struct mem_cgroup *memcg,
>  
>  	mutex_lock(&memcg_cache_mutex);
>  	new_cachep = cachep->memcg_params->memcg_caches[idx];
> -	if (new_cachep)
> +	if (new_cachep) {
> +		css_put(&memcg->css);
>  		goto out;
> +	}
>  
>  	new_cachep = kmem_cache_dup(memcg, cachep);
>  	if (new_cachep == NULL) {
>  		new_cachep = cachep;
> +		css_put(&memcg->css);
>  		goto out;
>  	}
>  
> -	mem_cgroup_get(memcg);
>  	atomic_set(&new_cachep->memcg_params->nr_pages , 0);
>  
>  	cachep->memcg_params->memcg_caches[idx] = new_cachep;
> @@ -3449,8 +3451,6 @@ static void memcg_create_cache_work_func(struct work_struct *w)
>  
>  	cw = container_of(w, struct create_work, work);
>  	memcg_create_kmem_cache(cw->memcg, cw->cachep);
> -	/* Drop the reference gotten when we enqueued. */
> -	css_put(&cw->memcg->css);
>  	kfree(cw);
>  }

You are putting references but I do not see any single css_{try}get
here. /me puzzled.

-- 
Michal Hocko
SUSE Labs
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