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.

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.

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