[RFC PATCH 8/8] nvmet: add configfs interface for target passthru

[hch@lst.de (Christoph Hellwig)]

On Fri, Mar 30, 2018@12:13:28PM -0600, Logan Gunthorpe wrote:
> I *really* dislike this interface. Not only is the "pt" directory
> confusing to the user, it's nearly identical to what a subsystem is. So
> as developers, if we want to add a config option to a subsystem we also
> have to add it to the equivalent pt. I've already seen one patch set
> that would be mutually exclusive to this only because of the
> configuration mess.
> 
> I'd much rather see either a couple new attributes in the existing
> subsystem

Maybe.  But how would you design it?  Have a passthrough filed under
the subsystem that you can echo a controller name to?  And then make
the exclusive vs creating namespaces?

> or some mechanism such that if you create a namespace that
> points to a controller (eg /dev/nvme1) it takes it as though you're
> trying to pass through the whole NVMe device. (The code would need to
> ensure that a passthrough subsystem configured this way could only have
> exactly one namespace.)

Ugg.  Hell no!  Way too much magic.