Re: [Qemu-devel] [PATCH 14/16] block/parallels: introduce ParallelsSnapshot data structure

[Kevin Wolf <kwolf@redhat.com>]

Am 15.12.2014 um 09:27 hat Denis V. Lunev geschrieben:
> In order to support snapshots of parallels images we should maintain
> snapshots list in BDRVParallelsState. Snapshots actually forms tree.
> Though, in read-only case, we do need to traverse only from current
> snapshot leaf to the snapshot tree root. Thus interesting for us
> snapshots forms old good linked list.
> 
> This patch just introduces the structure for this and fills it with
> a signle image as was done before.

s/signle/single/

> True parsing be done in the next patch.
> 
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> CC: Jeff Cody <jcody@redhat.com>
> CC: Kevin Wolf <kwolf@redhat.com>
> CC: Stefan Hajnoczi <stefanha@redhat.com>

If I understand correctly, this is what actually describes the backing
file relationship. We should probably use the normal infrastructure for
this.

The challenge here seems to be that the single descriptor XML file
describes the complete chain of backing files. This is different from
the image formats that we support until now.

I think we need some design discussion here first before we even look at
code. Did you consider making the snapshots regular backing files, and
if so, what were the reasons that let you prefer a purely internal
solution?

Kevin