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

[Christoph Hellwig]

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