Re: [dm-devel] [PATCH 3/2] dm: table load must always try dm_setup_md_queue

[Mike Snitzer <snitzer redhat com>]

On Wed, Jun 09 2010 at  1:38am -0400,
Kiyoshi Ueda <k-ueda ct jp nec com> wrote:

> Hi Mike,
> 
> On 06/05/2010 05:15 AM +0900, Mike Snitzer wrote:
> > @@ -2164,7 +2164,8 @@ static int dm_init_request_based_queue(s
> >  {
> >  	struct request_queue *q = NULL;
> >  
> > -	BUG_ON(md->queue->elevator);
> > +	if (unlikely(md->queue->elevator))
> > +		return 1;
> 
> I think the "unlikely" should be rather "likely", since
> dm_init_request_based_queue() is now called whenever request-based
> table is loaded even after the actual initialization has been done.

Yes, good point.  Though I'd expect reloading a request-based table is
actually fairly rare.  Is it really all that worthwhile to have any
branch prediction here?  Should we just remove the likely/unlikely
entirely?

Thanks,
Mike