[libvirt] RFC: Exposing backing chains in <domain> XML

[Richard W.M. Jones]

On Fri, Mar 14, 2014 at 11:07:21AM +0000, Daniel P. Berrange wrote:
> I understand why you chose to use nesting, but I can't say I like
> the appearance of nesting. I think that in the common case where
> we have a single non-branching chain, the XML structure is kind of
> unpleasant and would be nicer if just a flat list. Using nesting
> makes it harder to extract info about backing files from the XML
> structure with XPath because you can't simply ask for all <source>
> elements at a given location.

OTOH, with nesting, existing XPath queries keep working.

https://github.com/libguestfs/libguestfs/blob/master/src/libvirt-domain.c#L445

Have a look in this file for existing XPath queries involving /source

However a flat list of backingStore nodes (as you suggested later)
would not break anything.

> I don't think we want todo that - there are genuine use cases where
> that is a reasonable thing todo. eg you can provide a raw file to a
> guest and that guest may genuinely want to format the virtual disk
> it received with some other format. We don't want to taint such use
> cases.

Ewww by formatting you mean turning raw into qcow2??

Rich.

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