Re: [PATCH v6 1/7] block: Introduce the flag QUEUE_FLAG_NO_ZONE_WRITE_LOCK

[Jens Axboe <axboe@kernel.dk>]

On 8/8/23 3:46?PM, Bart Van Assche wrote:
> On 8/8/23 14:19, Jens Axboe wrote:
>> On 8/4/23 9:47?AM, Bart Van Assche wrote:
>>> Writes in sequential write required zones must happen at the write
>>> pointer. Even if the submitter of the write commands (e.g. a filesystem)
>>> submits writes for sequential write required zones in order, the block
>>> layer or the storage controller may reorder these write commands.
>>>
>>> The zone locking mechanism in the mq-deadline I/O scheduler serializes
>>> write commands for sequential zones. Some but not all storage controllers
>>> require this serialization. Introduce a new request queue flag to allow
>>> block drivers to indicate that they preserve the order of write commands
>>> and thus do not require serialization of writes per zone.
>>
>> Looking at how this is used, why not call it QUEUE_FLAG_ZONE_WRITE_LOCK
>> instead? That'd make the code easier to immediately grok, rather than
>> deal with double negations.
> 
> Hi Jens,
> 
> Do I understand correctly that you want me to set the
> QUEUE_FLAG_ZONE_WRITE_LOCK flag for all request queues by adding it to
> QUEUE_FLAG_MQ_DEFAULT and also that the UFS driver should clear the
> QUEUE_FLAG_ZONE_WRITE_LOCK flag?

I don't think setting that flag by default makes a lot of sense, if the
device in question isn't zoned. Maybe have variants of BLK_ZONED_* which
has a locked and unlocked variant for each where it applies? Perhaps
have the lock flag be common between them so you can check them in the
same way? That'd keep the fact that it's zoned and if it needs locking
in the same spot, rather than scatter them in two spots.

-- 
Jens Axboe