[linux-lvm] Snapshots of snapshots are not supported yet

[markw at mohawksoft.com]

I'm trying to get a snapshot of a snapshot. I know the new thin
provisioning stuff supports this, but I'm not sure the release state is
something I can use at a customer.

Using LVM2, the snapshot format is tried and true, but inefficient if you
want to take multiple snapshots.

Looking at dmsetup, there doesn't seem like there would be an issue taking
a snapshot of a snapshot, but it is disabled in the tools.

I guess my question is this: Can it be done? Is there any reason why it
should not work?