On Fri, Jan 27, 2017 at 09:27:53PM +0000, Bart Van Assche wrote:

Have you considered to convert all block drivers to the new
approach and to get rid of request.special? If so, do you already
have plans to start working on this? I'm namely wondering wheter I
should start working on this myself.

Hi Bart,

I'd love to have all drivers move of using .special (and thus reducing
request size further).  I think the general way to do that is to convert
them to blk-mq and not using the legacy cmd_size field.