Re: [PATCH 7/8] blkcg: implement per-queue policy activation

[Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

On Thu, Apr 12, 2012 at 04:29:39PM -0700, Tejun Heo wrote:

[..]
> @@ -111,12 +122,11 @@ static struct blkio_group *blkg_alloc(struct blkio_cgroup *blkcg,
>  		struct blkio_policy_type *pol = blkio_policy[i];
>  		struct blkg_policy_data *pd;
>  
> -		if (!pol)
> +		if (!blkcg_policy_enabled(q, pol))
>  			continue;
>  
>  		/* alloc per-policy data and attach it to blkg */
> -		pd = kzalloc_node(sizeof(*pd) + pol->pdata_size, GFP_ATOMIC,
> -				  q->node);
> +		pd = kzalloc_node(blkg_pd_size(pol), GFP_ATOMIC, q->node);
>  		if (!pd) {
>  			blkg_free(blkg);
>  			return NULL;
> @@ -130,7 +140,7 @@ static struct blkio_group *blkg_alloc(struct blkio_cgroup *blkcg,
>  	for (i = 0; i < BLKCG_MAX_POLS; i++) {
>  		struct blkio_policy_type *pol = blkio_policy[i];
>  
> -		if (pol)
> +		if (blkcg_policy_enabled(blkg->q, pol))
>  			pol->ops.blkio_init_group_fn(blkg);
>  	}

May be pol->ops.blkio_init_group_fn() can be called in the loop above
where you are allocating the group. So you don't end up looping through
policies twice and don't have to call blkcg_policy_enabled() twice.

Thanks
Vivek