From owner-freebsd-hackers@FreeBSD.ORG  Fri May  6 20:38:04 2005
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Date: Fri, 6 May 2005 16:37:30 -0400
From: "Kurt J. Lidl" <lidl@pix.net>
To: Warner Losh <imp@bsdimp.com>
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cc: freebsd-hackers@freebsd.org
Subject: Re: FS impl.
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On Fri, May 06, 2005 at 02:01:35PM -0600, Warner Losh wrote:
> >   I have been trying to write my own UFS-like filesystem
> > implementation for fun. I had read somewhere that UFS was developed in
> > user space (correct me if I'm wrong on that one) and then moved over
> > to kernel-space. I was wondering if there are any existing facilities
> > in the kernel source tree that would allow me to develop an fs in user
> > space easily or with a little tweaking? As of right now, I have to
> > develop, compile, panic, reboot, debug etc. which is frustrating and
> > time consuming.
> 
> Maybe you are thinking of NFS :-).  You can use the same hooks that
> amd and similar programs to implement your code in userland.

It's pretty well known that Kirk did the 4.2 FFS implementation
as a user-mode process.  This statement is made directly in
Luke Mewburn's paper on cross-building NetBSD:
	http://www.usenix.org/events/bsdcon03/tech/full_papers/mewburn/mewburn.pdf (page 9).

It doesn't say in the original 4.2 FFS paper.

-Kurt