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Message-ID: <14108b56-10c9-8760-39b1-ffa56220e5a3@opensource.wdc.com>
Date:   Thu, 28 Jul 2022 12:28:11 +0900
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Subject: Re: [PATCH v8 00/11] support non power of 2 zoned device
Content-Language: en-US
To:     Bart Van Assche <bvanassche@acm.org>,
        Pankaj Raghav <p.raghav@samsung.com>, hch@lst.de,
        axboe@kernel.dk, snitzer@kernel.org, Johannes.Thumshirn@wdc.com
Cc:     matias.bjorling@wdc.com, gost.dev@samsung.com,
        linux-kernel@vger.kernel.org, hare@suse.de,
        linux-block@vger.kernel.org, pankydev8@gmail.com,
        jaegeuk@kernel.org, dm-devel@redhat.com,
        linux-nvme@lists.infradead.org
References: <CGME20220727162246eucas1p1a758799f13d36ba99d30bf92cc5e2754@eucas1p1.samsung.com>
 <20220727162245.209794-1-p.raghav@samsung.com>
 <51255650-ddc2-4f3d-52e5-14007b9ff538@acm.org>
 <f2f29f97-5994-37f9-c922-31158c1c1b9a@opensource.wdc.com>
 <024d16ac-d685-0fcf-1ad3-e99946852b03@acm.org>
From:   Damien Le Moal <damien.lemoal@opensource.wdc.com>
Organization: Western Digital Research
In-Reply-To: <024d16ac-d685-0fcf-1ad3-e99946852b03@acm.org>
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Precedence: bulk

On 7/28/22 11:58, Bart Van Assche wrote:
> On 7/27/22 18:52, Damien Le Moal wrote:
>> On 7/28/22 08:19, Bart Van Assche wrote:
>>> On 7/27/22 09:22, Pankaj Raghav wrote:
>>>> This series adds support to npo2 zoned devices in the block and nvme
>>>> layer and a new **dm target** is added: dm-po2z-target. This new
>>>> target will be initially used for filesystems such as btrfs and
>>>> f2fs that does not have native npo2 zone support.
>>>
>>> Should any SCSI changes be included in this patch series? From sd_zbc.c:
>>>
>>> 	if (!is_power_of_2(zone_blocks)) {
>>> 		sd_printk(KERN_ERR, sdkp,
>>> 			  "Zone size %llu is not a power of two.\n",
>>> 			  zone_blocks);
>>> 		return -EINVAL;
>>> 	}
>>
>> There are no non-power of 2 SMR drives on the market and no plans to have
>> any as far as I know. Users want power of 2 zone size. So I think it is
>> better to leave sd_zbc & scsi_debug as is for now.
> 
> Zoned UFS devices will support ZBC and may have a zone size that is not 
> a power of two.

OK. So the check needs to be removed then and the entire zone append
emulation checked carefully. The divisions for zone no etc on non power of
2 zone size devices in zone append emulation hot path are really not
welcome though.


> 
> Thanks,
> 
> Bart.


-- 
Damien Le Moal
Western Digital Research