Re: [Qemu-devel] [PATCH v2 10/11] block: add option 'backing' to -drive options

[Paolo Bonzini]

Il 17/07/2013 15:48, Kevin Wolf ha scritto:
>> I understand this is the right thing to do long term, but pre-opening of
>> the target is not really needed for fleecing.
> 
> So for how much longer should we plan to procrastinate? (I know, not an
> entirely fair question, but we have to make the step at some point)

If we bring it up during soft freeze, we will procrastinate it a lot. :)
 If we bring it up at the beginning of a release cycle, the wait could
be as short as 1 month...

> I guess we can give a name to the target, and we can make drive-backup
> automatically connect the target with the original as its backing file
> (still needs the refcounting, by the way).

No, it doesn't need the refcounting (see my reply to the cover letter).
 In his next submission of drive-backup sync modes, Ian is already going
to handle the automatic connection of the target with the original.

> But is giving a name to the
> target not enough to allow "interesting" things to be done? I don't
> remember the details from the mirroring discussion, but it seems it were
> enough that you didn't want to do it.

Yes, but this time we have to bite the bullet on that one at least,
because we have no other choice (we want to do at least one
"interesting" thing, namely connect to it with the NBD server).

> And we'll want to reference existing BDSes as backing/protocol files in
> blockdev-add soon anyway, so if we decide against it here, it's just
> moving from Fam's to-do list to mine...

We can reconsider these very patches in 1 month.  It's just the timing,
combined with the fact that this is not necessary for fleecing, that I'm
uncomfortable with.

Paolo

> So no, I'm not totally comfortable with allowing it, but not allowing it
> isn't really an option either.
> 
> Kevin
>