Re: [PATCH 07/13] block: track zone conditions

[Damien Le Moal <dlemoal@kernel.org>]

On 11/1/25 06:17, Bart Van Assche wrote:
> On 10/30/25 11:13 PM, Damien Le Moal wrote:
>> Implement tracking of the runtime changes to zone conditions using
>> the new cond field in struct blk_zone_wplug. The size of this structure
>> remains 112 Bytes as the new field replaces the 4 Bytes padding at the
>> end of the structure. For zones that do not have a zone write plug, the
>> zones_cond array of a disk is used to track changes to zone conditions,
>> e.g. when a zone reset, reset all or finish operation is executed.
> 
> Why is it necessary to track the condition of sequential zones that do
> not have a zone write plug? Please explain what the use cases are.

Because zones that do not have a zone write plug can be empty OR full.

> 
> The zoned UFS device on my desk has 3420 sequential zones and zero
> conventional zones. If the condition of zones that do not have a zone
> write plug wouldn't be tracked that would save some memory.

That would really be "some"... Not a lot. Your memory usage will be less than a
mem page...

>> +static void blk_zone_set_cond(u8 *zones_cond, unsigned int zno,
>> +			      enum blk_zone_cond cond)
>> +{
>> +	if (!zones_cond)
>> +		return;
>> +
>> +	switch (cond) {
>> +	case BLK_ZONE_COND_IMP_OPEN:
>> +	case BLK_ZONE_COND_EXP_OPEN:
>> +	case BLK_ZONE_COND_CLOSED:
>> +		zones_cond[zno] = BLK_ZONE_COND_ACTIVE;
>> +		return;
>> +	case BLK_ZONE_COND_NOT_WP:
>> +	case BLK_ZONE_COND_EMPTY:
>> +	case BLK_ZONE_COND_FULL:
>> +	case BLK_ZONE_COND_OFFLINE:
>> +	case BLK_ZONE_COND_READONLY:
>> +	default:
>> +		zones_cond[zno] = cond;
>> +		return;
>> +	}
>> +}
>> +
>> +static void disk_zone_set_cond(struct gendisk *disk, sector_t sector,
>> +			       enum blk_zone_cond cond)
>> +{
>> +	u8 *zones_cond;
>> +
>> +	rcu_read_lock();
>> +	zones_cond = rcu_dereference(disk->zones_cond);
>> +	if (zones_cond) {
>> +		unsigned int zno = disk_zone_no(disk, sector);
>> +
>> +		/*
>> +		 * The condition of a conventional, readonly and offline zones
>> +		 * never changes, so do nothing if the target zone is in one of
>> +		 * these conditions.
>> +		 */
>> +		switch (zones_cond[zno]) {
>> +		case BLK_ZONE_COND_NOT_WP:
>> +		case BLK_ZONE_COND_READONLY:
>> +		case BLK_ZONE_COND_OFFLINE:
>> +			break;
>> +		default:
>> +			blk_zone_set_cond(zones_cond, zno, cond);
>> +			break;
>> +		}
>> +	}
>> +	rcu_read_unlock();
>> +}
> 
> Why does blk_zone_set_cond() accept a zone number as second argument and
> why does disk_zone_set_cond() accept a sector number as second argument?
> The callers of disk_zone_set_cond() can be optimized if its second
> argument would be changed from a sector number into a zone number.

How so ? all the callers have a BIO sector or a zone start sector on hand, not a
zone number. On the other hand, blk_zone_set_cond() is always used in places
where the zone number is already available.

So this calling convention makes sense to me as it is.

-- 
Damien Le Moal
Western Digital Research