block: remember a zone type regardless of its condition

Currently, bdev_zone_is_seq() identifies a sequential zone by looking at
the zone condition, assuming that any zone that does not have the
condition BLK_ZONE_COND_NOT_WP is a sequential write required zone. That
is correct only as long as the target zoned device does not support
storage element depopulation (aka HDD head depopulation), which is a
feature that can transition conventional zones to the read-only or offline
condition. For such device, we cannot distinguish anymore between
conventional and sequential zones using the zone condition as both zone
types can have the same conditions.

Prepare for fully supporting storage element depopulation and restoration
by caching the type of a zone in addition to its condition. This is
implemented by reformating the zones_cond array using a more compact zone
condition representation with the new enum blk_zstate. This zone condition
representation only uses the lower 4 bits of a byte for the condition
values, thus leaving the high order 4 bits of each byte entry of the
array for flags. The flag BLK_ZFLAG_CONV is defined to indicate
conventional zones.

The helper functions blk_zstate_to_zone_cond() and
blk_zone_cond_to_zstate() are implemented using lookup tables to convert
between enum blk_zone_condition values and enum blk_zstate zone condition
values. The helper blk_zstate_set() can be used to set a zones_state
entry with a zone condition and zone type flags, safely in accordance to
the size of the zone state array being accessed. This helper is used in
disk_zone_set_cond() to update a zone condition.
bdev_zone_is_seq() is modified to use the flags of the zones_state array
entries to identify sequential zones. The zones_state array initialization
and revalidation is unchanged from the former zones_cond array.

Overall, any zone condition that is being considered outside of the
zones_state array always uses the enum blk_zone_condition values as
before, thus minimizing the number of changes.

Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@kernel.org>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://patch.msgid.link/20260908085745.1082697-6-dlemoal@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 1 insertions, 1 deletions

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 098a65f3e48b..b91511bfbfbd 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -198,7 +198,7 @@ struct gendisk {
 	unsigned int		nr_zones;
 	unsigned int		zone_capacity;
 	unsigned int		last_zone_capacity;
-	u8 __rcu		*zones_cond;
+	u8 __rcu		*zones_state;
 	unsigned int		zone_wplugs_hash_bits;
 	atomic_t		nr_zone_wplugs;
 	spinlock_t		zone_wplugs_hash_lock;