Add NFSv3 tree root to mountd

[Mueller, Brian]

Similar to mountd's ability to specify the NFSv4 tree root via the V4: line in the exports file, I would like to add the ability to specify a NFSv3 tree root.  The goal to have the same exported path for both the V3 and V4.  If you have exports file like the following:

/foo/bar
V3: /foo/bar
V4: /foo/bar

NFS clients would mount /foo/bar by running

mount -t nfs -o ver=3 server:/ /mnt/v3
mount -t nfs -o ver=4 server:/ /mnt/v4

Without the change, the NFS client would need to specify different paths for v3 and v4

mount -t nfs -o ver=3 server:/foo/bar /mnt/v3
mount -t nfs -o ver=4 server:/ /mnt/v4

Feedback appreciated.  If there aren't any objections with incorporating this change into FreeBSD, I will start working on the changes to mountd.

Brian

Brian Mueller
Panasas Inc.