[dm-devel] [PATCH 15/18] scsi: allocate scsi_cmnd structures as part of struct request

[hch at lst.de]

On Fri, Jan 27, 2017 at 06:39:46PM +0000, Bart Van Assche wrote:
> Why have the scsi_release_buffers() and scsi_put_command(cmd) calls been
> moved up? I haven't found an explanation for this change in the patch
> description.

Because they reference the scsi_cmnd, which are now part of the request
and thus freed by blk_finish_request.  And yes, I should have mentioned
it in the changelog, sorry.

> Please also consider to remove the cmd->request->special = NULL assignments
> via this patch. Since this patch makes the lifetime of struct scsi_cmnd and
> struct request identical these assignments are no longer needed.

True.  If I had to resend again I would have fixed it up, but it's probably
not worth the churn now.

> This patch introduces the function scsi_exit_rq(). Having two functions
> for the single-queue path that release resources (scsi_release_buffers()
> and scsi_exit_rq()) is confusing. Since every scsi_release_buffers() call
> is followed by a blk_unprep_request() call, have you considered to move
> the scsi_release_buffers() call into scsi_unprep_fn() via an additional
> patch?

We could have done that.  But it's just more change for a code path
that I hope won't survive this calendar year.