virtio-blk: fix to match virtio spec

The merged patch series to support zoned block devices in virtio-blk
is not the most up to date version. The merged patch can be found at

https://lore.kernel.org/linux-block/[email protected]/

but the latest and reviewed version is

https://lore.kernel.org/linux-block/[email protected]/

The reason is apparently that the correct mailing lists and
maintainers were not copied.

The differences between the two are mostly cleanups, but there is one
change that is very important in terms of compatibility with the
approved virtio-zbd specification.

Before it was approved, the OASIS virtio spec had a change in
VIRTIO_BLK_T_ZONE_APPEND request layout that is not reflected in the
current virtio-blk driver code. In the running code, the status is
the first byte of the in-header that is followed by some pad bytes
and the u64 that carries the sector at which the data has been written
to the zone back to the driver, aka the append sector.

This layout turned out to be problematic for implementing in QEMU and
the request status byte has been eventually made the last byte of the
in-header. The current code doesn't expect that and this causes the
append sector value always come as zero to the block layer. This needs
to be fixed ASAP.

Fixes: 95bfec4 ("virtio-blk: add support for zoned block devices")
Cc: [email protected]
Signed-off-by: Dmitry Fomichev <[email protected]>
Reviewed-by: Stefan Hajnoczi <[email protected]>
Reviewed-by: Damien Le Moal <[email protected]>
Message-Id: <[email protected]>
Signed-off-by: Michael S. Tsirkin <[email protected]>

Author: dmitry-fomichev