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Date: Thu, 1 Sep 2011 16:05:26 +0200
From: Christoph Hellwig <hch@lst.de>
Message-ID: <20110901140526.GA9388@lst.de>
References: <20110901132755.GG14462@redhat.com>
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Subject: Re: [Qemu-devel] QEMU online guest disk resize wrt host block
	devices
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To: "Daniel P. Berrange" <berrange@redhat.com>
Cc: qemu-devel@nongnu.org, hch@lst.de

On Thu, Sep 01, 2011 at 02:27:55PM +0100, Daniel P. Berrange wrote:
> I see two likely approaches:
> 
>  1. Add a parameter to the existing 'block_resize' command
>     'refreshonly=true|false'
> 
>  2. Add a separate command  'block_refresh'

I think all that you need is a to implement a bdrv_truncate method
for host devices that simply checks if the new size smaller or equal
to the device size, and return 0 in that case or an error otherwise.