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Date:   Fri, 20 May 2022 12:16:08 +0200
From:   Javier =?utf-8?B?R29uesOhbGV6?= <javier.gonz@samsung.com>
To:     Johannes Thumshirn <Johannes.Thumshirn@wdc.com>
CC:     Hannes Reinecke <hare@suse.de>,
        Damien Le Moal <damien.lemoal@opensource.wdc.com>,
        Luis Chamberlain <mcgrof@kernel.org>,
        Theodore Ts'o <tytso@mit.edu>, Christoph Hellwig <hch@lst.de>,
        Pankaj Raghav <p.raghav@samsung.com>,
        "axboe@kernel.dk" <axboe@kernel.dk>,
        "pankydev8@gmail.com" <pankydev8@gmail.com>,
        "gost.dev@samsung.com" <gost.dev@samsung.com>,
        "jiangbo.365@bytedance.com" <jiangbo.365@bytedance.com>,
        "linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
        "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
        "dm-devel@redhat.com" <dm-devel@redhat.com>,
        "dsterba@suse.com" <dsterba@suse.com>,
        "linux-btrfs@vger.kernel.org" <linux-btrfs@vger.kernel.org>,
        Jaegeuk Kim <jaegeuk@kernel.org>
Subject: Re: [dm-devel] [PATCH v4 00/13] support non power of 2 zoned
 devices
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Precedence: bulk

On 20.05.2022 09:30, Johannes Thumshirn wrote:
>On 20/05/2022 08:27, Javier González wrote:
>> So you are suggesting adding support for !PO2 in the block layer and
>> then a dm to present the device as a PO2 to the FS? This at least
>> addresses the hole issue for raw zoned block devices, so it can be a
>> first step.
>>
>> This said, it seems to me that the changes to the FS are not being a
>> real issue. In fact, we are exposing some bugs while we generalize the
>> zone size support.
>>
>> Could you point out what the challenges in btrfs are in the current
>> patches, that it makes sense to add an extra dm layer?
>
>I personally don't like the padding we need to do for the super block.
>
>As I've pointed out to Pankaj already, I don't think it is 100% powerfail
>safe as of now. It could probably be made, but that would also involve
>changing non-zoned btrfs code which we try to avoid as much as we can.
>
>As Damien already said, we still have issues with the general zoned
>support in btrfs, just have a look at the list of open issues [1] we
>have.
>
Sounds good Johannes. I understand that the priority is to make btrfs
stable now, before introducing more variables. Let's stick to this and
then we can bring it back as the list of open issues becomes more
manageable.

>[1] https://protect2.fireeye.com/v1/url?k=f14a1d6f-90c10859-f14b9620-74fe485fffe0-3f1861e7739d8cc7&q=1&e=213fcc28-3f9d-41a1-b653-0dc0e203c718&u=https%3A%2F%2Fgithub.com%2Fnaota%2Flinux%2Fissues%2F

Thanks for sharing this too. It is a good way to where to help