quoted

quoted

I think the problem is that the submount doesn't appear in

/proc/mounts.

quoted

quoted

"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.

quoted

quoted

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.

quoted

quoted

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.

quoted

 My question is does a snapshot look any different than a subvol?

No difference between btrfs subvol and snapshot in theory.

but the btrfs subvol number in product env is usually fixed, and the btrfs
snapshot number is usually dynamic.

For fixed-number btrfs subvol/snapshot, it is OK to put them in the same
hierarchy, and then export all in /etc/exports static, as a walk around.

For dynamic-number btrfs snapshot number, we needs a dynamic way to export
them in nfs.

OK thanks for the information. I think they will just work in nfs-ganesha as
long as the snapshots or subvols are mounted within an nfs-ganesha export or
are exported explicitly. nfs-ganesha has the equivalent of knfsd's
nohide/crossmnt options and when nfs-ganesha detects crossing a filesystem
boundary will lookup the filesystem via getmntend and listing btrfs subvols
and then expose that filesystem (via the fsid attribute) to the clients
where at least the Linux nfs client will detect a filesystem boundary and
create a new mount entry for it.

Frank