[dm-devel] [PATCH 08/10] kpartx: use partition UUID for non-DM devices

[Alasdair G Kergon]

On Sat, May 06, 2017 at 12:05:57AM +0200, Martin Wilck wrote:
> Introduce a "fake" UUID for these devices to make sure kpartx
> deletes only devices it had created previously. Otherwise kpartx
> might e.g. delete LVM LVs that are inside a device it is trying
> to delete partitions for. It seems to be wiser to make sure the
> user delete these manually before running "kpartx -d".
> 
> With the fake UUID in place, we can re-introduce the UUID check
> for non-DM device that was removed in the earlier patch
> "kpartx: dm_remove_partmaps: support non-dm devices".
> 
> This disables also deletion of partition mappings created
> by earlier versions of kpartx. If kpartx has been updated after
> partition mappings were created, the "-f" flag can be used
> to force delting these partitions, too.
 
Indeed - always supply a uuid for every dm device created.
Add a standard prefix to the beginning of it, ideally "KPARTX-" to be
consistent with other dm tools ("LVM-", "CRYPT-" etc.) if you're
able to break compatibility, but "part" is still unique and adequate.  
(Stacked devices can end up with a stack of prefixes - only the leftmost one
counts.)

Alasdair