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Message-ID: <bb2b3784-422f-fc82-e5be-e4d24412e21f@opensource.wdc.com>
Date:   Sat, 1 Oct 2022 09:45:10 +0900
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Subject: Re: [PATCH v15 00/13] support zoned block devices with non-power-of-2
 zone sizes
Content-Language: en-US
To:     Bart Van Assche <bvanassche@acm.org>, Jens Axboe <axboe@kernel.dk>,
        Pankaj Raghav <p.raghav@samsung.com>, hch@lst.de,
        Keith Busch <kbusch@kernel.org>
Cc:     jaegeuk@kernel.org, agk@redhat.com, gost.dev@samsung.com,
        snitzer@kernel.org, linux-kernel@vger.kernel.org, hare@suse.de,
        matias.bjorling@wdc.com, Johannes.Thumshirn@wdc.com,
        linux-block@vger.kernel.org, linux-nvme@lists.infradead.org,
        pankydev8@gmail.com, dm-devel@redhat.com,
        "Martin K. Petersen" <martin.petersen@oracle.com>
References: <CGME20220923173619eucas1p13e645adbe1c8eb62fb48b52c0248ed65@eucas1p1.samsung.com>
 <20220923173618.6899-1-p.raghav@samsung.com>
 <5e9d678f-ffea-e015-53d8-7e80f3deda1e@samsung.com>
 <bd9479f4-ff87-6e5d-296e-e31e669fb148@kernel.dk>
 <0e5088a5-5408-c5bd-bf97-00803cb5faed@acm.org>
From:   Damien Le Moal <damien.lemoal@opensource.wdc.com>
Organization: Western Digital Research
In-Reply-To: <0e5088a5-5408-c5bd-bf97-00803cb5faed@acm.org>
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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