block: introduce blkdev_report_zones_cached()

block: introduce blkdev_report_zones_cached()

Introduce the function blkdev_report_zones_cached() to provide a fast
report zone built using the blkdev_get_zone_info() function, which gets
zone information from a disk zones_cond array or zone write plugs.
For a large capacity SMR drive, such fast report zone can be completed
in a few milliseconds compared to several seconds completion times
when the report zone is obtained from the device.

The zone report is built in the same manner as with the regular
blkdev_report_zones() function, that is, the first zone reported is the
one containing the specified start sector and the report is limited to
the specified number of zones (nr_zones argument). The information for
each zone in the report is obtained using blkdev_get_zone_info().

For zoned devices that do not use zone write plug resources,
using blkdev_get_zone_info() is inefficient as the zone report would
be very slow, generated one zone at a time. To avoid this,
blkdev_report_zones_cached() falls back to calling
blkdev_do_report_zones() to execute a regular zone report. In this case,
the .report_active field of struct blk_report_zones_args is set to true
to report zone conditions using the BLK_ZONE_COND_ACTIVE condition in
place of the implicit open, explicit open and closed conditions.

Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>