From mboxrd@z Thu Jan  1 00:00:00 1970
From: Al Viro <viro@ZenIV.linux.org.uk>
Subject: Re: [PATCH 3/3] fs: Add the reflink(2) system call.
Date: Sun, 3 May 2009 12:16:04 +0100
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Cc: Matthew Wilcox <matthew@wil.cx>,
	Joel Becker <joel.becker@oracle.com>,
	linux-fsdevel@vger.kernel.org, jmorris@namei.org,
	ocfs2-devel@oss.oracle.com
To: Christoph Hellwig <hch@infradead.org>
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On Sun, May 03, 2009 at 03:48:49AM -0400, Christoph Hellwig wrote:
> On Sun, May 03, 2009 at 07:39:02AM +0100, Al Viro wrote:
> > Another question: do we want that to work across mounpoint boundary?
> > It's probably OK in this case, but...
> 
> I don't think so.  Allowing any link-like semantics over mount point
> boundaries will just cause problems.

Quite.  I realize that this is how vfs_link() is written, but I really
wonder if we should turn that if (foo->i_sb != bar->i_sb) into BUG_ON()
in both.  Their callers have vfsmounts and ought to do the vfsmount-level
check anyway, so running into *that* -EXDEV should be impossible.