Re: [Qemu-block] [Qemu-devel] [PATCH v4 00/27] block: Lock images when opening

[Fam Zheng]

On Tue, 05/10 13:22, Daniel P. Berrange wrote:
> On Tue, May 10, 2016 at 01:11:30PM +0100, Richard W.M. Jones wrote:
> > At no point did I say that it was safe to use libguestfs on live VMs
> > or that you would always get consistent data out.
> > 
> > But the fact that it can fail is understood, the chance of failure is
> > really tiny (it has literally only happened twice that I've read
> > corrupted data, in years of daily use), and the operation is very
> > useful.
> > 
> > So I think this patch series should either not lock r/o VMs, or should
> > add a nolock flag to override the locking (which libguestfs will
> > always use).

It sounds you are happy with either way but actually this series does both. So,
would it be okay for libguestfs if we go for "lock r/o VMs by default and
provide nolock flag"? It would then have the best default for non-libguestfs
users.

Fam

> 
> If QEMU locks r/o disks, then libvirt would likely end up setting the
> "nolock" flag unconditionally too, in order to avoid breaking libguestfs
> and other application usage of libvirt.
> 
> Regards,
> Daniel
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