From mboxrd@z Thu Jan  1 00:00:00 1970
From: Shaya Potter <spotter@cs.columbia.edu>
Subject: Re: [RFC][PATCH 10/14] In-kernel file copy between union mounted
 filesystems
Date: Fri, 18 May 2007 09:47:31 -0400
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Cc: Jan Engelhardt <jengelh@linux01.gwdg.de>,
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	Jan Blunck <j.blunck@tu-harburg.de>
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Bharata B Rao wrote:

> 
> Not really. This is called during copyup of a file residing in a lower
> layer. And that is done only for regular files.

That is broken.

You should be able to change the permissions on a device node on a layer 
that is RO.

so it would copy it up (1. mknod, 2. copy attributes) and then the 
appropriate attribute notification change would be called.