[PATCHv2 5/5] nvme: allow user passthrough commands to poll

[Keith Busch]

On Mon, May 17, 2021 at 10:25:21PM +0530, Kanchan Joshi wrote:
> On Mon, Apr 26, 2021 at 8:46 PM Keith Busch <kbusch at kernel.org> wrote:
> >
> > On Mon, Apr 26, 2021 at 04:43:16PM +0200, Christoph Hellwig wrote:
> > > On Fri, Apr 23, 2021 at 03:05:58PM -0700, Keith Busch wrote:
> > > > The block layer knows how to deal with polled requests. Let the NVMe
> > > > driver use the previously reserved user "flags" fields to define an
> > > > option to allocate the request from the polled hardware contexts. If
> > > > polling is not enabled, then the block layer will automatically fallback
> > > > to a non-polled request.
> > >
> > > So this only support synchronous polling for a single command.  What
> > > use case do we have for that?  I think io_uring based polling would
> > > be much more useful once we support NVMe passthrough through that.
> >
> > There is no significant use case here. I just needed a simple way to
> > test the polled exec from earlier in the series. It was simple enough so
> > I included the patch here, but it's really not important compared to the
> > preceeding patches.
> 
> It would be great to see this in at some point; helps in making
> passthrough more useful.
> I'll look into integrating this with async-passthrough.

Right, async ioctl would really provide better justification for
passthrough polling. I'll post a new version of this series this week to
address the previously submitted feedback, but without this patch for
now.