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From: Al Boldi <a1426z@gawab.com>
To: Josef Sipek <jsipek@fsl.cs.sunysb.edu>
Subject: Re: [RFC] VFS: FS CoW using redirection
Date: Sat, 26 Aug 2006 22:05:21 +0300
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Cc: Eric Van Hensbergen <ericvh@gmail.com>, linux-fsdevel@vger.kernel.org,
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       =?iso-8859-1?q?J=F6rn=20Engel?= <joern@wohnheim.fh-wedel.de>
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Josef Sipek wrote:
> On Wed, Aug 23, 2006 at 07:24:02PM +0200, Jörn Engel wrote:
> > On Sun, 9 July 2006 15:50:36 +0300, Al Boldi wrote:
> > > Consider something simple like this:
> > >
> > > VFS - anyFS1 (r/w) used normally, unless ENotFound, then redirect read
> > > to \              anyFS2, or CoW from anyFS2 to anyFS1.
> > >       anyFS2 (r/o) used normally.
> >
> > That concept is known as union mount.  Jan Blunck did some patches in
> > that direction, you might be able to find them in the archives.  If
> > not, just send him a mail.

Thanks for the pointer!

So what was the rejecting theme?

> Or you can give Unionfs a try: http://www.unionfs.org

UnionFS is great, but it incurs additional overhead, as it lives below the 
real VFS.  What could be really great, is to move some basic functionality 
abstractions from UnionFS into VFS proper.


Thanks!

--
Al