Re: [Qemu-devel] [RFC][PATCH 0/2] Allow cache settings for block devices to be changed at runtime.

[Anthony Liguori]

On 03/01/2011 07:50 AM, Christoph Hellwig wrote:
> On Tue, Mar 01, 2011 at 12:48:34PM +0000, Stefan Hajnoczi wrote:
>    
> > On Tue, Mar 01, 2011 at 01:42:54PM +0100, Christoph Hellwig wrote:
> >      
> > > I have patches to do that, and to allow changing O_DIRECT via a monitor
> > > command, but to toggle O_SYNC via fcntl I first need to get a kernel
> > > patch in as that's currently not allowed to be changed at runtime.
> > >        
> > Great it sounds like you have already implemented the two cases (guest wce and
> > host O_DIRECT) that we're talking about.
> >      
> At least in theory.  And for Linux I can add setting/clearing of O_SYNC
> via fcntl easily, but what do we do for other hosts?

To start with, we can just fail the command at the QMP level.

>    I'm not sure
> closing/reopening the backing file is easily feasible.
>    

Regards,

Anthony Liguori