[dm-devel] [PATCH v4 01/11] block: improve handling of all zones reset operation

[Chaitanya Kulkarni]

On 5/24/21 7:25 PM, Damien Le Moal wrote:
> SCSI, ZNS and null_blk zoned devices support resetting all zones using
> a single command (REQ_OP_ZONE_RESET_ALL), as indicated using the device
> request queue flag QUEUE_FLAG_ZONE_RESETALL. This flag is not set for
> device mapper targets creating zoned devices. In this case, a user
> request for resetting all zones of a device is processed in
> blkdev_zone_mgmt() by issuing a REQ_OP_ZONE_RESET operation for each
> zone of the device. This leads to different behaviors of the
> BLKRESETZONE ioctl() depending on the target device support for the
> reset all operation. E.g.
>
> blkzone reset /dev/sdX
>
> will reset all zones of a SCSI device using a single command that will
> ignore conventional, read-only or offline zones.
>
> But a dm-linear device including conventional, read-only or offline
> zones cannot be reset in the same manner as some of the single zone
> reset operations issued by blkdev_zone_mgmt() will fail. E.g.:
>
> blkzone reset /dev/dm-Y
> blkzone: /dev/dm-0: BLKRESETZONE ioctl failed: Remote I/O error
>
> To simplify applications and tools development, unify the behavior of
> the all-zone reset operation by modifying blkdev_zone_mgmt() to not
> issue a zone reset operation for conventional, read-only and offline
> zones, thus mimicking what an actual reset-all device command does on a
> device supporting REQ_OP_ZONE_RESET_ALL. This emulation is done using
> the new function blkdev_zone_reset_all_emulated(). The zones needing a
> reset are identified using a bitmap that is initialized using a zone
> report. Since empty zones do not need a reset, also ignore these zones.
> The function blkdev_zone_reset_all() is introduced for block devices
> natively supporting reset all operations. blkdev_zone_mgmt() is modified
> to call either function to execute an all zone reset request.
>
> Signed-off-by: Damien Le Moal <damien.lemoal at wdc.com>
> [hch: split into multiple functions]
> Signed-off-by: Christoph Hellwig <hch at lst.de>

Apart from nit mentioned earlier, looks good.

Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni at wdc.com>