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Date: Tue, 01 Mar 2011 13:52:52 +0100
From: Kevin Wolf <kwolf@redhat.com>
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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: Anthony Liguori <aliguori@us.ibm.com>, Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>, Stefan Hajnoczi <stefanha@gmail.com>, qemu-devel <qemu-devel@nongnu.org>, Ananth Narayan <ananth@linux.vnet.ibm.com>, Prerna Saxena <prerna@linux.vnet.ibm.com>

Am 01.03.2011 13:42, schrieb Christoph Hellwig:
> 
> The only way to change the cache settings is from the guest.  Without
> that we're guranteed to lose data when going from WCE=0 to WCE=1.
> 
> 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.

We can re-open the file for now, and we need an implementation for older
kernels/other host OSes anyway, so I don't think we have to wait for the
kernel patch to be accepted.

Kevin