block: use zone condition to determine conventional zones

block: use zone condition to determine conventional zones

The conv_zones_bitmap field of struct gendisk is used to define a bitmap
to identify the conventional zones of a zoned block device. The bit for
a zone is set in this bitmap if the zone is a conventional one, that is,
if the zone type is BLK_ZONE_TYPE_CONVENTIONAL. For such zone, this
always corresponds to the zone condition BLK_ZONE_COND_NOT_WP.
In other words, conv_zones_bitmap tracks a single condition of the
zones of a zoned block device.

In preparation for tracking more zone conditions, change
conv_zones_bitmap into an array of zone conditions, using 1 byte per
zone. This increases the memory usage from 1 bit per zone to 1 byte per
zone, that is, from 16 KiB to about 100 KiB for a 30 TB SMR HDD with 256
MiB zones. This is a trade-off to allow fast cached report zones later
on top of this change.

Rename the conv_zones_bitmap field of struct gendisk to zones_cond. Add
a blk_revalidate_zone_cond() function to initialize the zones_cond array
of a disk during device scan and to update it on device revalidation.
Move the allocation of the zones_cond array to
disk_revalidate_zone_resources(), making sure that this array is always
allocated, even for devices that do not need zone write plugs (zone
resources), to ensure that bdev_zone_is_seq() can be re-implemented to
use the zone condition array in place of the conv zones bitmap.

Finally, the function bdev_zone_is_seq() is rewritten to use a test on
the condition of the target zone.

Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
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>