From owner-freebsd-hackers  Thu Apr 17 10:15:59 1997
Return-Path: <owner-hackers>
Received: (from root@localhost)
          by freefall.freebsd.org (8.8.5/8.8.5) id KAA22024
          for hackers-outgoing; Thu, 17 Apr 1997 10:15:59 -0700 (PDT)
Received: from lestat.nas.nasa.gov (lestat.nas.nasa.gov [129.99.50.29])
          by freefall.freebsd.org (8.8.5/8.8.5) with ESMTP id KAA22017
          for <hackers@freebsd.org>; Thu, 17 Apr 1997 10:15:55 -0700 (PDT)
Received: from localhost (localhost [127.0.0.1]) by lestat.nas.nasa.gov (8.7.5/8.6.12) with SMTP id KAA17594; Thu, 17 Apr 1997 10:06:51 -0700 (PDT)
Message-Id: <199704171706.KAA17594@lestat.nas.nasa.gov>
X-Authentication-Warning: lestat.nas.nasa.gov: Host localhost [127.0.0.1] didn't use HELO protocol
To: "David S. Miller" <davem@jenolan.rutgers.edu>
Cc: bsdhack@shadows.aeon.net, spidaman@well.com, hackers@freebsd.org
Subject: Re: Feasibility of porting Linux filesystem code? 
Reply-To: Jason Thorpe <thorpej@nas.nasa.gov>
From: Jason Thorpe <thorpej@nas.nasa.gov>
Date: Thu, 17 Apr 1997 10:06:51 -0700
Sender: owner-hackers@freebsd.org
X-Loop: FreeBSD.org
Precedence: bulk

On Thu, 17 Apr 1997 06:16:55 -0400 
 "David S. Miller" <davem@jenolan.rutgers.edu> wrote:

 > XFS is SGI's bread and butter, if you write a freely available version
 > of it you'd:
 > 
 > 1) Have to reverse engineer it completely
 > 2) Would have a building full of lawyers on your ass
 > 
 > I know because I investigated such a thing ad nauseum while I was
 > hacking Linux at SGI, and that was the final word.

So, you read the papers that have been published on it, and implement
something that does basically the same thing.  You only have to
"reverse engineer it completely" if you want them to be compatible
(i.e. want to be able to plug a disk from your SGI into your PC or
whatever).  Personally, I don't care about that too much.

...can you point me to the clause in the license that accompanies the
IRIX binary distributions which specifically disallows reverse-engineering?

In any case, the notion of a journaled, extent-based file system that
uses b+ trees rather than bitmaps is a neat idea, but I wouldn't call it
patentable (of course, that doens't mean that SGI hasn't _tried_ to
patent it; I don't know if they have or not).  But, if they haven't,
I don't see how they could possibly stop someone from writing a file
system based on the same ideas.  (Sure, they could be jerks and generally
a PITA, but they couldn't _stop_ you...)

Jason R. Thorpe                                       thorpej@nas.nasa.gov
NASA Ames Research Center                               Home: 408.866.1912
NAS: M/S 258-6                                          Work: 415.604.0935
Moffett Field, CA 94035                                Pager: 415.428.6939