Re: [PATCH v2 04/13] block: remember a zone type regardless of its condition

[Hannes Reinecke <hare@suse.de>]

On 8/6/26 6:04 PM, Damien Le Moal wrote:
> 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 prepare a zones_state
> entry for a disk with a zone condition and zone type flags. 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>
> ---
>   block/blk-zoned.c      | 202 +++++++++++++++++++++++++++++------------
>   include/linux/blkdev.h |   2 +-
>   2 files changed, 143 insertions(+), 61 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@suse.de                                +49 911 74053 688
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