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Re: [Qemu-devel] qcow2, lazy_refcounts and killing qemu
From: |
Richard W.M. Jones |
Subject: |
Re: [Qemu-devel] qcow2, lazy_refcounts and killing qemu |
Date: |
Fri, 5 Sep 2014 18:41:37 +0100 |
User-agent: |
Mutt/1.5.20 (2009-12-10) |
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.
----------------------------------------------------------------------
I've updated the test script (attached), so you can now run it against
your own qemu, and also to improve the output.
Rich.
--
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qemu-lazy-refcounts.sh
Description: Bourne shell script