Re: [dm-devel] [PATCH v4 00/13] support non power of 2 zoned devices

Johannes Thumshirn
2022-05-19T07:34:59Z

On 19/05/2022 05:19, Damien Le Moal wrote:
> On 5/19/22 12:12, Luis Chamberlain wrote:
>> On Thu, May 19, 2022 at 12:08:26PM +0900, Damien Le Moal wrote:
>>> On 5/18/22 00:34, Theodore Ts'o wrote:
>>>> On Tue, May 17, 2022 at 10:10:48AM +0200, Christoph Hellwig wrote:
>>>>> I'm a little surprised about all this activity.
>>>>>
>>>>> I though the conclusion at LSF/MM was that for Linux itself there
>>>>> is very little benefit in supporting this scheme. It will massively
>>>>> fragment the supported based of devices and applications, while only
>>>>> having the benefit of supporting some Samsung legacy devices.
>>>>
>>>> FWIW,
>>>>
>>>> That wasn't my impression from that LSF/MM session, but once the
>>>> videos become available, folks can decide for themselves.
>>>
>>> There was no real discussion about zone size constraint on the zone
>>> storage BoF. Many discussions happened in the hallway track though.
>>
>> Right so no direct clear blockers mentioned at all during the BoF.
>
> Nor any clear OK.

So what about creating a device-mapper target, that's taking npo2 drives and
makes them po2 drives for the FS layers? It will be very similar code to
dm-linear.

After all zoned support for FSes started with a device-mapper (dm-zoned) and
as the need for a more integrated solution arose, it changed into natiive
support.

And all that is there is simple arithmetic and a bio_clone(), if this is the
slowest part of the stack involving a FS like f2fs or btrfs I'm throwing a
round of anyone's favorite beverage at next year's LSFMM.

Byte,
Johannes