Re: [PATCH v3 3/5] dm: Always split write BIOs to zoned device limits

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

On 6/26/25 01:34, Bart Van Assche wrote:
> On 6/25/25 2:33 AM, Damien Le Moal wrote:
>> +	/*
>> +	 * Mapped devices that require zone append emulation will use the block
>> +	 * layer zone write plugging. In such case, we must split any large BIO
>> +	 * to the mapped device limits to avoid potential deadlocks with queue
>> +	 * freeze operations.
>> +	 */
>> +	if (!dm_emulate_zone_append(md))
>> +		return false;
>> +	return bio_needs_zone_write_plugging(bio) || bio_straddles_zones(bio);
> 
> Changing the dm_emulate_zone_append() call into a
> disk_need_zone_resources() call or a disk->zone_wplugs_hash test
> probably would make the intention of the if-statement more clear.

The comment is not clear enough ?

> Additionally, bio_needs_zone_write_plugging() already tests
> disk->zone_wplugs_hash. Isn't the dm_emulate_zone_append() call
> superfluous because of this?

Yes, I think it is. But I did try to minimize changes given that this is a fix
which is not small already...

I will do more testing and send follow-up cleanup patches.

-- 
Damien Le Moal
Western Digital Research