Re: [Qemu-devel] Re: [PATCH] block: Enable fall-back to read-only for backing file

[Alexander Graf]

Am 01.02.2010 um 10:06 schrieb Christoph Hellwig <address@hidden>:

> On Mon, Feb 01, 2010 at 09:46:00AM +0100, Kevin Wolf wrote:
> > > Is it better to always open the backing file with read-only mode ?  
> > > this will be more consistent/predictable ?
> >
> > I would love to open them read-only unconditionally, but we can't. It
> > would break the commit monitor command. I think the read-only  
> > fallback
> > is appropriate for backing files.
>
> The clean way would be to require an explicit BACKING_WRITEABLE flag
> if we want to commit to it.  But I suspect it's too late to refit that
> now.

We don't know beforehand if a user will use the commit comnand during  
tje runtime of the vm.

IMHO it'd be best to always open backing files read only and try to  
open them for write access on the commit command. That command can  
then fail gaciously.

Alex
>