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From:   "NeilBrown" <neilb@suse.de>
To:     "Wang Yugui" <wangyugui@e16-tech.com>
Cc:     linux-nfs@vger.kernel.org
Subject: Re: any idea about auto export multiple btrfs snapshots?
In-reply-to: <20210613115313.BC59.409509F4@e16-tech.com>
References: <20210613115313.BC59.409509F4@e16-tech.com>
Date:   Tue, 15 Jun 2021 08:50:35 +1000
Message-id: <162371103543.23575.13662722966178222587@noble.neil.brown.name>
Precedence: bulk

On Sun, 13 Jun 2021, Wang Yugui wrote:
> Hi,
>=20
> Any idea about auto export multiple btrfs snapshots?
>=20
> One related patch is yet not merged to nfs-utils 2.5.3.
> From:   "NeilBrown" <neilb@suse.de>
> Subject: [PATCH/RFC v2 nfs-utils] Fix NFSv4 export of tmpfs filesystems.
>=20
> In this patch, an UUID is auto generated when a tmpfs have no UUID.
>=20
> for btrfs, multiple subvolume snapshot have the same filesystem UUID.
> Could we generate an UUID for btrfs subvol with 'filesystem UUID' + 'subvol=
 ID'?

You really need to ask this question of btrfs developers.  'mountd'
already has a special-case exception for btrfs, to prefer the uuid
provided by statfs64() rather than the uuid extracted from the block
device.  It would be quite easy to add another exception.
But it would only be reasonable to do that if the btrfs team told us how
that wanted us to generate a UUID for a given mount point, and promised
that would always provide a unique stable result.

This is completely separate from the tmpfs patch you identified.

NeilBrown


>=20
> Best Regards
> Wang Yugui (wangyugui@e16-tech.com)
> 2021/06/13
>=20
>=20
>=20