Re: [PATCH UPDATED block/for-linus] block: blk-throttle should be drained regardless of q->elevator

[Vivek Goyal <vgoyal@redhat.com>]

On Mon, Feb 13, 2012 at 05:14:27PM -0800, Tejun Heo wrote:

[..]
>  		/*
>  		 * This function might be called on a queue which failed
> -		 * driver init after queue creation.  Some drivers
> -		 * (e.g. fd) get unhappy in such cases.  Kick queue iff
> -		 * dispatch queue has something on it.
> +		 * driver init after queue creation or is not yet fully
> +		 * active yet.  Some drivers (e.g. fd and loop) get unhappy
> +		 * in such cases.  Kick queue iff dispatch queue has
> +		 * something on it and @q has request_fn set.
>  		 */
> -		if (!list_empty(&q->queue_head))
> +		if (!list_empty(&q->queue_head) && q->request_fn)
>  			__blk_run_queue(q);

Is it not a BUG() condition. We have a queue which has some requests
in it and we don't have q->request_fn?

Thanks
Vivek