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Date: Tue, 12 Mar 2013 10:33:30 +0100
From: Stefan Hajnoczi <stefanha@gmail.com>
Message-ID: <20130312093330.GA19624@stefanha-thinkpad.redhat.com>
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Subject: Re: [Qemu-devel] [RFC V6 19/33] block: Add qcow2_dedup format and
 image creation code.
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To: =?iso-8859-1?Q?Beno=EEt?= Canet <benoit.canet@irqsave.net>
Cc: kwolf@redhat.com, qemu-devel@nongnu.org, stefanha@redhat.com

On Mon, Mar 11, 2013 at 04:20:03PM +0100, Benoît Canet wrote:
> > > +    if (dedup) {
> > > +        version = 3;
> > > +    }
> > 
> > Lazy refcounts don't force the version.  It would be consistent to
> > refrain from forcing the version too.
> 
> I don't understand. Aren't the incompatible features bits implying version = 3 ?
> When compat=1.1 is set the code force version to 3.

Only compat= affects the version.  Lazy refcounts and dedup should be
orthogonal.

If you specify lazy_refcounts=on without compat=1.1 you get an error.

Same should apply to deduplication.  Otherwise the qemu-img create
behavior is inconsistent - you get an error for lazy_refcounts but no
error and silent version=3 for deduplication.

Stefan