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Re: [Qemu-devel] [PATCH v2 (for-2.11)] qcow2: fix image corruption after


From: Daniel P. Berrange
Subject: Re: [Qemu-devel] [PATCH v2 (for-2.11)] qcow2: fix image corruption after committing qcow2 image into base
Date: Fri, 17 Nov 2017 14:37:05 +0000
User-agent: Mutt/1.9.1 (2017-09-22)

On Fri, Nov 17, 2017 at 08:32:32AM -0600, Eric Blake wrote:
> On 11/17/2017 05:29 AM, Daniel P. Berrange wrote:
> > After committing the qcow2 image contents into the base image, qemu-img
> > will call bdrv_make_empty to drop the payload in the layered image.
> > 
> > When this is done for qcow2 images, it blows away the LUKS encryption
> > header, making the resulting image unusable. There are two codepaths
> > for emptying a qcow2 image, and the second (slower) codepath leaves
> > the LUKS header intact, so force use of that codepath.
> > 
> > Reviewed-by: Eric Blake <address@hidden>
> > Signed-off-by: Daniel P. Berrange <address@hidden>
> > ---
> 
> >  
> >      if (s->qcow_version >= 3 && !s->snapshots &&
> > -        3 + l1_clusters <= s->refcount_block_size) {
> > +        3 + l1_clusters <= s->refcount_block_size &&
> > +        s->crypt_method_header != QCOW_CRYPT_LUKS) {
> 
> Missing the check for s->nb_bitmaps == 0 that Vladimir mentioned on v1.
> Either we can add that in this patch, or I can post the obvious followup
> that also needs queuing.

That's unrelated to LUKS though, so best as a separate patch, which adds
a I/O test case that validates that feature.


Regards,
Daniel
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