[linux-lvm] determining lv from mount point

[Galen Seitz <galens seitzassoc com>]

I'm trying to update my backup script (a tweaked version of hostdump.sh
from backupcentral.com) to use snapshots.  My machine has a mix of 
normal ext3 and ext3 on lvm filesystems.  What I'm looking for is an
easy way from a shell script to determine the lv from the mount point.
The ideal thing would be a shell function that takes the mount point
as an argument and returns the associated logical volume, or an error
if the filesystem doesn't use lvm.

Suggestions?

thanks,
galen