Re: [PATCH v5 1/3] blkcg: Introduce blkg_root_lookup()

[Tejun Heo <tj@kernel.org>]

Hello,

On Thu, Aug 09, 2018 at 07:53:36AM -0700, Bart Van Assche wrote:
> +/**
> + * blkg_lookup - look up blkg for the specified request queue
> + * @q: request_queue of interest
> + *
> + * Lookup blkg for @q at the root level. See also blkg_lookup().
> + */
> +static inline struct blkcg_gq *blkg_root_lookup(struct request_queue *q)
> +{
> +	struct blkcg_gq *blkg;
> +
> +	rcu_read_lock();
> +	blkg = blkg_lookup(&blkcg_root, q);
> +	rcu_read_unlock();
> +
> +	return blkg;
> +}

So, root blkg is always available as long as the request_queue is
alive.  Sth like the following would be simpler?

static inline struct blkcg_gq *blk_queue_root_blkg(struct request_queue *q)
{
	return q->root_blkg;
}

-- 
tejun