Re: [Qemu-devel] [PATCH 0/2] qcow2: Add two more unalignment checks

[Eric Blake <eblake@redhat.com>]

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On 01/19/2015 01:49 PM, Max Reitz wrote:
> With the series adding unalignment checks and the series reworking the
> zero cluster expansion code overlapping, the unalignment checks have not
> been implemented in the latter code.
> 
> This series fixes it.
> 
> There are other places which would require unalignment checks, like the
> offsets of L1 tables, especially for snapshots; but because it would be
> best to add these checks in the function which reads the snapshot table,
> this would make images with broken snapshots completely unusable, which
> is something I opted to avoid for now.
> 
> Ideally, we need to make the qcow2 repair function repair such cases,
> but until that is done there is not much we can do about them.

What's the best repair? Read the data from the unaligned location, and
write a fresh copy into a new aligned allocation?  At any rate, I agree
that repairing unaligned locations is harder than detecting them, so
your series is fine as is.

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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