Re: [Qemu-devel] core dump with drive-mirror

[Eric Blake <eblake@redhat.com>]

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On 06/30/2014 05:16 PM, Eric Blake wrote:
> I'm trying to track down a core dump with the QMP drive-mirror command.

Looks like the bug is related to a base image that is not a multiple of
a cluster size.

> 
> # in one terminal:
> cd /tmp
> rm -f base.img snap1.img snap2.img copy.img
> 
> # base.img <- snap1.img <- snap2.img; intentionally populating base.img
> # with a qcow2 header, but treating it as raw data
> qemu-img create -f qcow2 base.img 10M

If, right here, I inject:

truncate --size 262144 base.img

> qemu-img create -f qcow2 -b base.img -o backing_fmt=raw snap1.img
> qemu-img create -f qcow2 -b snap1.img -o backing_fmt=qcow2 snap2.img
> cp base.img copy.img
> # Yes, this command line is derived from libvirt...
> LC_ALL=C PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin \
>  QEMU_AUDIO_DRV=none gdb --args  /usr/bin/qemu-system-x86_64 \

...then everything else succeeds.  So it seems the problem is that qemu
is doing a lousy job of handling a backing file and/or destination file
that is not fully rounded out to a proper size.

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


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