Re: [PATCH 3/4] blk-mq: replace blk_mq_init_commands with a ->init_request method

[Christoph Hellwig <hch@infradead.org>]

On Wed, Mar 19, 2014 at 11:08:20AM +0800, Ming Lei wrote:
> > +               blk_rq_init(q, q->flush_rq);
> > +               if (reg->cmd_size)
> > +                       q->flush_rq->special =
> > +                               blk_mq_rq_to_pdu(q->flush_rq);
> > +
> > +               if (reg->ops->init_request(driver_data,
> > +                               NULL, q->flush_rq, -1))
> > +                       goto err_flush_rq;
> > +       }
> 
> The above looks a bit weird because q->flush_rq is invisible to
> driver and should always be initialized no matter if driver defines
> its .init_request callback or not.

You mean the blk_rq_init?  We already do a real initialization before
actually using it, it's just there to prevent passing a half-initialized
one to the driver.