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

[Christoph Hellwig]

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.