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Re: [Qemu-devel] qcow2, lazy_refcounts and killing qemu
From: |
Markus Armbruster |
Subject: |
Re: [Qemu-devel] qcow2, lazy_refcounts and killing qemu |
Date: |
Mon, 08 Sep 2014 09:16:15 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) |
"Richard W.M. Jones" <address@hidden> writes:
> On Fri, Sep 05, 2014 at 04:39:51PM +0100, Stefan Hajnoczi wrote:
>> Did you try older QEMU versions? I'm curious if this is something that
>> crept in later or is fundamentally broken in lazy_refcounts=on.
>
> At your prompting, I've done a bit more investigation.
>
> I was basing my observations on qemu 2.1.0. However I tried my test
> against qemu from git today and the bug has gone. Good!
>
> For my entertainment, I bisected the problem, and the commit which
> *fixes* it is:
>
> commit 91af7014125895cc74141be6b60f3a3e882ed743
> Author: Max Reitz <address@hidden>
> Date: Fri Jul 18 20:24:56 2014 +0200
>
> block: Add bdrv_refresh_filename()
>
> I didn't believe this either, but I have checked the result manually
> and I'm pretty sure that whatever this commit does, it does end up
> fixing the lazy_refcounts problem as a side-effect.
Weird. Maybe Max (cc'ed) has an idea.
> ----------------------------------------------------------------------
>
> I've updated the test script (attached), so you can now run it against
> your own qemu, and also to improve the output.