Re: [PATCH v2 5/6] memcg: introduce swap_cgroup_init()/swap_cgroup_free()

[Lord Glauber Costa of Sealand <glommer@parallels.com>]

On 01/28/2013 02:54 PM, Jeff Liu wrote:
> Introduce swap_cgroup_init()/swap_cgroup_free() to allocate buffers when creating the first
> non-root memcg and deallocate buffers on the last non-root memcg is gone.
> 
> Signed-off-by: Jie Liu <jeff.liu@oracle.com>
> CC: Glauber Costa <glommer@parallels.com>
> CC: Michal Hocko <mhocko@suse.cz>
> CC: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> CC: Johannes Weiner <hannes@cmpxchg.org>
> CC: Mel Gorman <mgorman@suse.de>
> CC: Andrew Morton <akpm@linux-foundation.org>
> CC: Sha Zhengju <handai.szj@taobao.com>
> 

Looks sane.

Reviewed-by: Glauber Costa <glommer@parallels.com>

Only:

>  #endif /* !__GENERATING_BOUNDS_H */
> diff --git a/mm/page_cgroup.c b/mm/page_cgroup.c
> index 189fbf5..0ebd127 100644
> --- a/mm/page_cgroup.c
> +++ b/mm/page_cgroup.c
> @@ -362,14 +362,28 @@ static int swap_cgroup_prepare(int type)
>  	unsigned long idx, max;
>  
>  	ctrl = &swap_cgroup_ctrl[type];
> +	if (!ctrl->length) {
> +		/*
> +		 * Bypass the buffer allocation if the corresponding swap
> +		 * partition/file was turned off.
> +		 */
> +		pr_debug("couldn't allocate swap_cgroup on a disabled swap "
> +			 "partition or file, index: %d\n", type);
> +		return 0;
> +	}
> +
>  	ctrl->map = vzalloc(ctrl->length * sizeof(void *));
> -	if (!ctrl->map)
> +	if (!ctrl->map) {
> +		ctrl->length = 0;

Considering moving this assignment somewhere in the exit path in the
labels region.


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