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

[Eric Blake <eblake@redhat.com>]

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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 <eblake@redhat.com>
> Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
> ---

>  
>      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.

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


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