linux-kernel - Re: [PATCH v8 00/11] support non power of 2 zoned device

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Date:   Thu, 28 Jul 2022 12:28:11 +0900
From:   Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To:     Bart Van Assche <bvanassche@....org>,
        Pankaj Raghav <p.raghav@...sung.com>, hch@....de,
        axboe@...nel.dk, snitzer@...nel.org, Johannes.Thumshirn@....com
Cc:     matias.bjorling@....com, gost.dev@...sung.com,
        linux-kernel@...r.kernel.org, hare@...e.de,
        linux-block@...r.kernel.org, pankydev8@...il.com,
        jaegeuk@...nel.org, dm-devel@...hat.com,
        linux-nvme@...ts.infradead.org
Subject: Re: [PATCH v8 00/11] support non power of 2 zoned device

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