On 06/01/2017 12:17 PM, Bart Van Assche wrote:

On Thu, 2017-06-01 at 12:06 -0700, Jens Axboe wrote:

quoted

On 06/01/2017 06:11 AM, Bart Van Assche wrote:

quoted

On Thu, 2017-06-01 at 08:08 +0200, Christoph Hellwig wrote:

quoted

On Wed, May 31, 2017 at 03:52:46PM -0700, Bart Van Assche wrote:

quoted

Commit 6d247d7f71d1 ("block: allow specifying size for extra command
data") added support for .cmd_size to blk-sq. Due to that patch the
blk_mq_rq_{to,from}_pdu() functions are also useful for single-queue
block drivers. Hence remove "_mq" from the name of these functions.
This patch does not change any functionality. Most of this patch has
been generated by running the following shell command:

I don't really see the point of this as it's primarily a blk-mq API
and we still hope to get rid of the old code.  But I'm not necessarily
against it either.

I would like to introduce calls to these functions in several scsi-sq
functions. If I would do that without renaming these functions then anyone
who reads the code of these functions and sees calls to functions with a
blk_mq_ prefix could get really confused when trying to figure out whether
these functions are used by scsi-sq, scsi-mq or perhaps both.

But that should go away, eventually.

Hello Jens,

I agree that we should work towards removal of the single queue block layer.
But how long will it take before that code is removed?

Due to recent patches from Christoph the 'request' member in struct scsi_cmnd
is now superfluous. I'd like to replace accesses to that member by a call to
blk_mq_rq_from_pdu(). I'm afraid that doing that in scsi-sq code paths will
make that code look weird.

For the old path, I'd suggest that you just wrap the blk_mq_*_pdu() calls
with a non-mq named version, and stuff that in blkdev.h. That way we can
keep the blk-mq API more logical, and we can just kill those wrappers
when the last user goes away.

That's also a lot less churn than renaming all of the existing callers.

-- 
Jens Axboe