[dm-devel] [PATCH] announcing the dm-update target

[Alasdair G Kergon]

On Tue, Nov 23, 2021 at 04:07:21PM -0800, Akilesh Kailash wrote:
> Why not extend dm-snapshot; in that way you can have the existing
> kernel COW format + support compression.

In short, this is quite a focussed requirement and it doesn't seem worth
compromising on the goals by attempting to shoe-horn it into a framework
that was designed to fit around some quite different constraints twenty
years ago.

> I understand this for read-only but if dm-snapshot supports it,
> existing users  can have the
> compression feature if required.

I doubt that anyone wants to develop dm-snapshot any further.  It's only
really good for small short-term snapshots where performance and memory
usage don't matter.  The more-sophisticated thin provisioning approach
replaced it.

> Also, I am curious what are the other real world use case here apart
> from Android ?

There seems to be a general industry movement towards edge, attestation,
trusted boot, nested systems, confidential computing, containers,
<insert your favourite buzzwords> etc. and I think this type of
device-mapper target might play a useful role as one of the low-level
components involved in building up support for some of those scenarios.
(Just as we recently began adding support for attestation.)
 
Alasdair