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From:   "Frank Filz" <ffilzlnx@mindspring.com>
To:     "'NeilBrown'" <neilb@suse.de>,
        "'Wang Yugui'" <wangyugui@e16-tech.com>
Cc:     <linux-nfs@vger.kernel.org>
References: <20210617122852.BE6A.409509F4@e16-tech.com>, <162397637680.29912.2268876490205517592@noble.neil.brown.name>, <20210618152631.F3DE.409509F4@e16-tech.com> <162425113589.17441.4163890972298681569@noble.neil.brown.name>
In-Reply-To: <162425113589.17441.4163890972298681569@noble.neil.brown.name>
Subject: RE: any idea about auto export multiple btrfs snapshots?
Date:   Mon, 21 Jun 2021 07:35:05 -0700
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> I think the problem is that the submount doesn't appear in =
/proc/mounts.
> "nfsd_fh()" in nfs-utils needs to be able to map from the uuid for a =
filesystem to
> the mount point.  To do this it walks through /proc/mounts checking =
the uuid of
> each filesystem.  If a filesystem isn't listed there, it obviously =
fails.
>=20
> I guess you could add code to nfs-utils to do whatever "btrfs subvol =
list" does to
> make up for the fact that btrfs doesn't register in /proc/mounts.
>=20
> NeilBrown

I've been watching this with interest for the nfs-ganesha project. We =
recently were made aware that we weren't working with btrfs subvols, and =
I added code so that in addition to using getmntent (essentially =
/proc/mounts) to populate filesystems, we also scan for btrfs subvols =
and with that we are able to export subvols. My question is does a =
snapshot look any different than a subvol? If they show up in the subvol =
list then we shouldn't need to do anything more for nfs-ganesha, but if =
there's something else needed to discover them, then we may need =
additional code in nfs-ganesha. I have not yet had a chance to check out =
exporting a snapshot yet.

Thanks

Frank Filz