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

[Damien Le Moal <damien.lemoal@opensource.wdc.com>]

On 3/28/23 11:29, 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>

One nit below, but otherwise looks good to me.

Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>

> -static inline bool virtblk_has_zoned_feature(struct virtio_device *vdev)
> -{
> -	return false;
> +	u8 model;
> +
> +	virtio_cread(vdev, struct virtio_blk_config, zoned.model, &model);
> +	if (model == VIRTIO_BLK_Z_HM) {
> +		dev_err(&vdev->dev,
> +			"zoned devices are not supported by the kernel");

May be simply: "Zoned devices are not supported"
Or: "Support for zoned devices is disabled"


-- 
Damien Le Moal
Western Digital Research