[PATCH v4 8/8] sd_zbc: clear zone resources for non-zoned case

[Christoph Hellwig]

On Thu, Jan 28, 2021 at 01:47:33PM +0900, Damien Le Moal wrote:
> For host-aware ZBC disk, setting the device zoned model to BLK_ZONED_HA
> using blk_queue_set_zoned() in sd_read_block_characteristics() may
> result in the block device effective zoned model to be "none"
> (BLK_ZONED_NONE) if partitions are present on the device. In this case,
> sd_zbc_read_zones() should not setup the zone related queue limits for
> the disk so that the device limits and configuration is consistent with
> a regular disk and resources not uselessly allocated (e.g. the zone
> write pointer tracking array for zone append emulation).
> 
> Furthermore, if the disk zoned model changes at run time due to the
> creation of a partition by the user, the zone related resources can be
> released.
> 
> Fix both problems by introducing the function sd_zbc_clear_zone_info()
> to reset the scsi disk zone information and free resources and by
> returning early in sd_zbc_read_zones() for a block device that has a
> zoned model equal to BLK_ZONED_NONE.

So creating the partition doesn't even call into the driver, which
means we'll leak the info for now.  But I guess the next revalidate
will simply clean it up, so it is not a major issue.

Looks good:

Reviewed-by: Christoph Hellwig <hch at lst.de>