Re: [dm-devel] DM_snapshot_cow filesystem (dmsetup create snapshot)

[Alasdair G Kergon <agk redhat com>]

On Thu, Dec 01, 2011 at 02:18:37PM -0600, Douglas McClendon wrote:
> The overlay device in this situation is a read-write tmpfile in tmpfs,  
> looped to be available as the dm-snapshot 'snapshot/overlay device'.

Ah - well if your base device is already read-only, then there is no
corruption and you should be able to edit the bit of the disk image
that says 'this image is invalid' and recover it read-only or extend it.

Alasdair