null_blk: Introduce zone_append_max_sectors attribute

Add the zone_append_max_sectors configfs attribute and module parameter
to allow configuring the maximum number of 512B sectors of zone append
operations. This attribute is meaningful only for zoned null block
devices.

If not specified, the default is unchanged and the zoned device max
append sectors limit is set to the device max sectors limit.
If a non 0 value is used for this attribute, which is the default,
then native support for zone append operations is enabled.
Setting a 0 value disables native zone append operations support to
instead use the block layer emulation.

Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Tested-by: Hans Holmberg <hans.holmberg@wdc.com>
Tested-by: Dennis Maisenbacher <dennis.maisenbacher@wdc.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20240408014128.205141-17-dlemoal@kernel.org


Signed-off-by: Jens Axboe <axboe@kernel.dk>