Re: [Qemu-devel] [PATCH] dmg: fix ->open failure

[Christoph Hellwig <hch@lst.de>]

On Mon, Jan 11, 2010 at 03:11:52PM +0100, Kevin Wolf wrote:
> More or less the same hack, just in cleaner? Or trying to fundamentally
> change things? I think you haven't answered yet to what I said in the
> thread of my original hack. I'm quoting it here for convenience:

Well, not dealing with the format list in raw, but rather in block.c

> > Ok, if you start talking about layering, we can have a fundamental
> > discussion on this topic and why the layering is broken anyway.
> > Logically, we have image formats like qcow2, VMDK and raw, and they are
> > stored in files, on CD-ROMs or general block devices. From a layering
> > perspective, it is wrong to include the latter in the raw format driver
> > in the first place.
> 
> Actually, I think the differentiation between raw files and host_* is at
> the same level as protocols are. Probably they should be implemented
> very similarly.
> 
> Do you think it's possible/worth the effort to try putting things
> straight here?

So what you want is basically:

 - hdev_* and file as protocols in addition to nbd/ftp/http/..
 - a raw image format that can be used ontop of any protocol instead of
   an image format

That would indeed be a much better, not to say actually logical
layering.  The raw image format would be more or less a no-op just
stacking ontop of the protocol.  If we can find a way to implement this
efficiently it might be the way to go.