Bug#555958: Activation of lvm snapshots

[Alasdair G Kergon]

On Sun, Jul 24, 2011 at 05:25:07PM +0100, Ian Jackson wrote:
> should activate the underlying lv if that's necessary.  Or at the very
> least there should be some way to ask lvchange/vgchange to do so.
> So the real bug is in the lvm tools themselves, not in the initramfs
> scripts.
 
This could indeed be improved.

All snapshots + origin must be activated together as a group.  You can't
selectively activate snapshots: you get everything or nothing.  (This is
due to the current architecture.  When the userspace code for thin
provisioning is written, this restriction might get relaxed.)

This restriction is currently implemented by only allowing activation
requests on the origin, not the snapshots.

Now we could say "if you request activation of any snapshot, we'll
activate the origin and other snapshots too" OR "if you request
activation of a snapshot AND it is the only snapshot of that origin
we'll activate the origin too".  Is it worth doing either of these?

In all cases we could improve the error messages.

Alasdair