Re: [PATCH-for-4.6 1/6] target: Add target_alloc_session() helper function

[Nicholas A. Bellinger]

On Wed, 2016-01-13 at 09:17 +0100, Christoph Hellwig wrote:
> On Wed, Jan 13, 2016 at 12:09:26AM -0800, Nicholas A. Bellinger wrote:
> > > I'd much rather have the fabrics drivers call transport_alloc_session_tags
> > > directly from the callback than growing even more arguments here.
> > > 
> > 
> > What's the point..?
> > 
> > Only vhost-scsi currently needs to allocate extra resources for
> > se_session percpu-ida tag pre-allocation.
> 
> The point is that allocating "tags" (or better command structures) isn't
> fundamentally related to allocating a session, and in fact not even
> used by many drivers.

Huh..?  It's used by iscsi-target, ib_isert, tcm_qla2xxx, vhost-scsi and
tcm_fc.

That's the majority of the drivers people care about.

>  A flow where drivers that need these "tags"
> explicitly allocate them is a lot more obvious than forcing more
> arguments to a function that already has a lot and isn't related to
> these "tags" otherwise.

The goal is to get to the point where all fabric drivers use tag
pre-allocation, and not vice-versa.

That said, I think it makes sense to leave it as is instead of adding
new callbacks for iscsi-target, ib_isert, and tcm_fc to just handle
se_session tag pre-allocation.