linux-kernel - Re: [PATCH v15 00/13] support zoned block devices with non-power-of-2 zone sizes

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Message-ID: <bb2b3784-422f-fc82-e5be-e4d24412e21f@opensource.wdc.com>
Date:   Sat, 1 Oct 2022 09:45:10 +0900
From:   Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To:     Bart Van Assche <bvanassche@....org>, Jens Axboe <axboe@...nel.dk>,
        Pankaj Raghav <p.raghav@...sung.com>, hch@....de,
        Keith Busch <kbusch@...nel.org>
Cc:     jaegeuk@...nel.org, agk@...hat.com, gost.dev@...sung.com,
        snitzer@...nel.org, linux-kernel@...r.kernel.org, hare@...e.de,
        matias.bjorling@....com, Johannes.Thumshirn@....com,
        linux-block@...r.kernel.org, linux-nvme@...ts.infradead.org,
        pankydev8@...il.com, dm-devel@...hat.com,
        "Martin K. Petersen" <martin.petersen@...cle.com>
Subject: Re: [PATCH v15 00/13] support zoned block devices with non-power-of-2
 zone sizes

On 10/1/22 04:38, Bart Van Assche wrote:
> On 9/30/22 08:13, Jens Axboe wrote:
>> On 9/29/22 12:31 AM, Pankaj Raghav wrote:
>>>> Hi Jens,
>>>>    Please consider this patch series for the 6.1 release.
>>>>
>>>
>>> Hi Jens, Christoph, and Keith,
>>>   All the patches have a Reviewed-by tag at this point. Can we queue this up
>>> for 6.1?
>>
>> It's getting pretty late for 6.1 and I'd really like to have both Christoph
>> and Martin sign off on these changes.
> 
> Hi Jens,
> 
> Agreed that it's getting late for 6.1.
> 
> Since this has not been mentioned in the cover letter, I want to add 
> that in the near future we will need these patches for Android devices. 
> JEDEC is working on supporting zoned storage for UFS devices, the 
> storage devices used in all modern Android phones. Although it would be 
> possible to make the offset between zone starts a power of two by 
> inserting gap zones between data zones, UFS vendors asked not to do this 
> and hence need support for zone sizes that are not a power of two. An 
> advantage of not having to deal with gap zones is better filesystem 
> performance since filesystem extents cannot span gap zones. Having to 
> split filesystem extents because of gap zones reduces filesystem 
> performance.

As mentioned many times, my opinion is that a good implementation should
*not* have any extent span zone boundaries. So personally, I do not
consider such argument as a valid justification for the non-power-of-2
zone size support.

> 
> Thanks,
> 
> Bart.
> 
> 

-- 
Damien Le Moal
Western Digital Research