Re: [Qemu-devel] [PATCH v5 02/12] qcow2: Implement bdrv_make_empty()

[Kevin Wolf]

Am 22.04.2014 um 18:02 hat Max Reitz geschrieben:
> On 22.04.2014 16:23, Kevin Wolf wrote:
> >QCOW2_DISCARD_REQUEST is for requests that come from the guest. SNAPSHOT
> >would be a nice fit if we reinterpreted it so that it doesn't only refer
> >to internal snapshots but also to external ones. I would be okay with
> >OTHER as well if you prefer.
> >
> >Perhaps a look at the defaults can help us: SNAPSHOT defaults to on,
> >OTHER to off. I think it totally makes sense to physically discard
> >clusters in qcow2_make_empty() in almost every case, so that might be a
> >good reason to use SNAPSHOT here.
> 
> My problem with using SNAPSHOT would be that this function is that
> there is no indication of this function being meant for committing
> snapshots only; however, in practice it is obviously only used for
> that purpose, thus I can accept it.

It all depends on what you call a snapshot. I think an image with a
backing file constitutes a snapshot pretty much by definition. But I
know that some people differentiate snapshots and templates, or things
like that.

> But I do like reasoning with the defaults. ;-)

:-)

> I'll go for SNAPSHOT then and include an explanatory comment.

Great, thanks.

Kevin