Re: [Qemu-devel] [Bug 1179219] Re: segfault in alloc_refcount_block

[Stefan Hajnoczi]

On Sun, May 12, 2013 at 11:43:31PM -0000, Brian J. Murrell wrote:
> On 13-05-12 05:14 PM, Michael Tokarev wrote:
> > First, having a single qcow2 file open for read-write access by more
> > than one process in unsupported.
> 
> But I don't, if I understand how qcow2 snapshots work.  Let me apologize
> if I was not clear.  Each of the VMs have their own snapshot of the
> common "origin" qcow2 disk.  If I understand correctly in such a
> configuration, only one VM has each snapshot qcow2 open for read-write
> access and they all have the "origin" open read-only, is that correct?
> Surely that must be supported, yes?

$ qemu-img create -f qcow2 -b template.img vm001.qcow2
$ qemu-img create -f qcow2 -b template.img vm002.qcow2
$ qemu-img create -f qcow2 -b template.img vm003.qcow2
$ ...launch vm001-vm002...

This is safe.  The template.img backing file is open read-only.

Did you do anything else?

Stefan