Re: [virtio-dev] [PATCH 2/2] virtio-blk: fix ZBD probe in kernels without ZBD support

Re: [virtio-dev] [PATCH 2/2] virtio-blk: fix ZBD probe in kernels without ZBD support

[Stefan Hajnoczi]

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On Mon, Mar 27, 2023 at 10:29:28PM -0400, Dmitry Fomichev wrote:
> When the kernel is built without support for zoned block devices,
> virtio-blk probe needs to error out any host-managed device scans
> to prevent such devices from appearing in the system as non-zoned.
> The current virtio-blk code simply bypasses all ZBD checks if
> CONFIG_BLK_DEV_ZONED is not defined and this leads to host-managed
> block devices being presented as non-zoned in the OS. This is one of
> the main problems this patch series is aimed to fix.
> 
> In this patch, make VIRTIO_BLK_F_ZONED feature defined even when
> CONFIG_BLK_DEV_ZONED is not. This change makes the code compliant with
> the voted revision of virtio-blk ZBD spec. Modify the probe code to
> look at the situation when VIRTIO_BLK_F_ZONED is negotiated in a kernel
> that is built without ZBD support. In this case, the code checks
> the zoned model of the device and fails the probe is the device
> is host-managed.
> 
> The patch also adds the comment to clarify that the call to perform
> the zoned device probe is correctly placed after virtio_device ready().
> 
> Fixes: 95bfec41bd3d ("virtio-blk: add support for zoned block devices")
> Cc: stable@vger.kernel.org
> Signed-off-by: Dmitry Fomichev <dmitry.fomichev@wdc.com>
> ---
>  drivers/block/virtio_blk.c | 34 ++++++++++++++++++----------------
>  1 file changed, 18 insertions(+), 16 deletions(-)

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

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Re: [virtio-dev] [PATCH 1/2] virtio-blk: migrate to the latest patchset version

[Stefan Hajnoczi]

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On Mon, Mar 27, 2023 at 10:29:27PM -0400, Dmitry Fomichev wrote:
> 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/20221016034127.330942-3-dmitry.fomichev@wdc.com/
> 
> , but the latest and reviewed version is
> 
> https://lore.kernel.org/linux-block/20221110053952.3378990-3-dmitry.fomichev@wdc.com/
> 
> 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: 95bfec41bd3d ("virtio-blk: add support for zoned block devices")
> Cc: stable@vger.kernel.org
> Signed-off-by: Dmitry Fomichev <dmitry.fomichev@wdc.com>
> ---
>  drivers/block/virtio_blk.c      | 238 +++++++++++++++++++++-----------
>  include/uapi/linux/virtio_blk.h |  18 +--
>  2 files changed, 165 insertions(+), 91 deletions(-)

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

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