From: Arnd Bergmann <arnd@arndb.de>
Subject: Re: [RFC 0/7] [RFC] cramfs: fake write support
Date: Mon, 2 Jun 2008 16:13:14 +0200
Message-ID: <200806021613.15088.arnd@arndb.de>
References: <200805311737.58991.arnd@arndb.de> <200806021315.41211.arnd@arndb.de> <6880.1212411400@jrobl>
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Cc: Jamie Lokier <jamie@shareable.org>,
	Phillip Lougher <phillip@lougher.demon.co.uk>,
	David Newall <davidn@davidnewall.com>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	hch@lst.de
To: hooanon05@yahoo.co.jp
In-Reply-To: <6880.1212411400@jrobl>
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Sender: linux-fsdevel-owner@vger.kernel.org

On Monday 02 June 2008, hooanon05@yahoo.co.jp wrote:
> I don't want you to call aufs users crazy who are using such policies.
> By the way, how do you think link(2) or rename(2)? When the source file
> exists on the lower writable branch, do you think copy-up is the best
> way? Or do you think all lower branches should be readonly?
> There is an exception in aufs's branch-select policy. That is
> link/rename case. When the source file exists on a writable branch, aufs
> tries link/rename it on that branch in every policy. Do you think it
> best to do it on the top branch only?

Yes, I tend to consider the union case identical to the cross-mount
move or link, so I'd expect the kernel to return errno=EXDEV and user
space to handle this by doing the appropriate copy/unlink as it does
for other cases already.

	Arnd <><