lvconvert: provide useful error when snapshot-merge target missing

On Thu, Oct 14 2010 at  5:04am -0400,
Zdenek Kabelac <[email protected]> wrote:

> Dne 13.10.2010 23:42, Alasdair G Kergon napsal(a):
> > On Wed, Oct 13, 2010 at 09:06:53PM +0200, Milan Broz wrote:
> >> I think this will break shared (external) segment module ABI.
> > 
> > Indeed - we make no guarantees for that ABI and don't even bother 
> > versioning it.  We don't believe there are any out-of-tree users.
> > 
> 
> I'd propose to drop/turn off this feature completely - targets usually cannot
> work without heavy tweaking through the rest of the code anyway. So in fact we
> rather 'pretend' there is such functionality.

I'm not following what you're saying.  There is no pretending here...

The feature fails gracefully with an informative error message.

What's the problem?

Mike