Re: [PATCH 2/4] mm/memcontrol.c: use accessor to get id from css

[Michal Hocko]

On Tue 22-04-14 14:30:41, Jianyu Zhan wrote:
> This is a prepared patch for converting from per-cgroup id to
> per-subsystem id.
> 
> We should not access per-cgroup id directly, since this is implemetation
> detail. Use the accessor css_from_id() instead.
> 
> This patch has no functional change.
> 
> Signed-off-by: Jianyu Zhan <nasa4836@xxxxxxxxx>

Acked-by: Michal Hocko <mhocko@xxxxxxx>
Thanks!

> ---
>  mm/memcontrol.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 80d9e38..46333cb 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -528,10 +528,10 @@ static inline bool mem_cgroup_is_root(struct mem_cgroup *memcg)
>  static inline unsigned short mem_cgroup_id(struct mem_cgroup *memcg)
>  {
>  	/*
> -	 * The ID of the root cgroup is 0, but memcg treat 0 as an
> -	 * invalid ID, so we return (cgroup_id + 1).
> +	 * The ID of css for the root cgroup is 0, but memcg treat 0 as an
> +	 * invalid ID, so we return (id + 1).
>  	 */
> -	return memcg->css.cgroup->id + 1;
> +	return css_to_id(&memcg->css) + 1;
>  }
>  
>  static inline struct mem_cgroup *mem_cgroup_from_id(unsigned short id)
> @@ -6407,7 +6407,7 @@ mem_cgroup_css_online(struct cgroup_subsys_state *css)
>  	struct mem_cgroup *memcg = mem_cgroup_from_css(css);
>  	struct mem_cgroup *parent = mem_cgroup_from_css(css_parent(css));
>  
> -	if (css->cgroup->id > MEM_CGROUP_ID_MAX)
> +	if (css_to_id(css) > MEM_CGROUP_ID_MAX)
>  		return -ENOSPC;
>  
>  	if (!parent)
> -- 
> 2.0.0-rc0
> 

-- 
Michal Hocko
SUSE Labs
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