Re: [Qemu-devel] [PATCH] qcow2: fix image corruption after committing qcow2 image into base

[Eric Blake <eblake@redhat.com>]

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On 11/03/2017 09:41 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) codepaths leaves
> the LUKS header intact, so force use of that codepath.
> 
> Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
> ---
> 
> NB, ideally we would fix the faster codepath in make_completely_empty, but
> having looked at the code, I've really no idea how to even start on fixing that
> to not kill the LUKS header clusters.

Hmm - I wonder if persistent bitmaps are also corrupted in the fast path.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


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