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Date: Thu, 9 Sep 2010 23:01:37 +0200
From: Christoph Hellwig <hch@lst.de>
Subject: Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format
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To: Avi Kivity <avi@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>, Stefan Hajnoczi <stefanha@gmail.com>, qemu-devel@nongnu.org, Alexander Graf <agraf@suse.de>, Christoph Hellwig <hch@lst.de>

On Thu, Sep 09, 2010 at 09:24:26AM +0300, Avi Kivity wrote:
> The other thing we can do is defragment the logical image, then 
> defragment the underlying file (if the filesystem supports it, issue the 
> appropriate ioctl, otherwise defragment to a new file which you write 
> linearly).

What's what the defragmentation code does in a slightly optimized
fashion anyway - so if you want to do it from qemu just do it that
way.  Don't even bother calling the filesystem ioctls directly given
that they just implementa low-level helpers and the actual logic is
in the userspace side of the defragmentation tools.