[RFC 5/5] nvme: wire-up support for async-passthru on char-device.

[Kanchan Joshi]

> > Also I think we'll want admin command passthrough on /dev/nvmeX as
> > well, but I'm fine solving the other items first.

Sure, will add that in the second round. Should be fairly simple as we
can reuse io-command work anyway.

> > > > +static int nvme_ioctl_finish_metadata(struct bio *bio, int ret,
> > > > +               void __user *meta_ubuf)
> > > > +{
> > > > +       struct bio_integrity_payload *bip = bio_integrity(bio);
> > > > +
> > > > +       if (bip) {
> > > > +               void *meta = bvec_virt(bip->bip_vec);
> > > > +
> > > > +               if (!ret && bio_op(bio) == REQ_OP_DRV_IN &&
> > > > +                   copy_to_user(meta_ubuf, meta, bip->bip_vec->bv_len))
> > > > +                       ret = -EFAULT;
> > >
> > > Maybe it is better to move the check "bio_op(bio) != REQ_OP_DRV_IN" outside.
> > > Because this can be common, and for that we can avoid entering into
> > > the function call itself (i.e. nvme_ioctl_finish_metadata).
> >
> > Function calls are pretty cheap, but I'll see what we can do.  I'll try
> > to come up with a prep series to refactor the passthrough support for
> > easier adding of the io_uring in the next days.
>
> In that case we will base the newer version on its top.
But if it saves some cycles for you, and also the travel from nvme to
linux-block tree - I can carry that refactoring as a prep patch in
this series. Your call.