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Date: Tue, 01 Mar 2011 14:13:45 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: Re: [Qemu-devel] [RFC][PATCH 0/2] Allow cache settings for block
	devices to be changed at runtime.
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To: Christoph Hellwig <hch@lst.de>
Cc: Kevin Wolf <kwolf@redhat.com>, Ananth Narayan <ananth@linux.vnet.ibm.com>, Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>, Prerna Saxena <prerna@linux.vnet.ibm.com>, qemu-devel <qemu-devel@nongnu.org>

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