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Date: Thu, 10 Sep 2009 10:32:51 +0200
From: Kevin Wolf <kwolf@redhat.com>
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Subject: Re: [Qemu-devel] More qcow2 bugs? - qemu-img convert/commit
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To: Jamie Lokier <jamie@shareable.org>
Cc: qemu-devel@nongnu.org

Am 10.09.2009 10:27, schrieb Kevin Wolf:
> Am 10.09.2009 01:26, schrieb Jamie Lokier:
>> 37% is large enough to be a clue: Does it simply expand the qcow2 file
>> without reading the backing file at all?  A quick strace shows that
>> indeed, it does *open* the backing file and it does read the backing
>> file's header, but after that it doesn't read it at all.
>>
>> Did I miss something obvious which means this is ok?
> 
> No, this definitely looks like a bug. I tend to suspect qemu-img rather
> than qcow2, though. After all, your qcow2 image works when a VM reads it
> and from a qcow2 perspective there should be no difference from reading
> in qemu-img.
> 
> I'll have a look at it.

Actually, first of all, which qemu version are you using?

There is a qemu-iotests test case for qemu-img convert with backing
files and git master passes it for me. However, there was a fix to
qemu-img in July (commit d032044fb97d525ae93fb4c96713a5c467044c17)
concerning conversion with backing files.

Kevin