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Re: [Qemu-devel] More qcow2 bugs? - qemu-img convert/commit


From: Kevin Wolf
Subject: Re: [Qemu-devel] More qcow2 bugs? - qemu-img convert/commit
Date: Thu, 10 Sep 2009 10:27:17 +0200
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.1) Gecko/20090814 Fedora/3.0-2.6.b3.fc11 Thunderbird/3.0b3

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.

> Should the output of "qemu-img convert" be identical to the backing
> file after "qemu-img commit", assuming they are the same format?

No, same format isn't enough. Assuming they are both raw images (as in
your case), I would agree, though.

Kevin




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