linux-kernel - Re: Thinking outside the box on file systems

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Date:	Wed, 15 Aug 2007 23:42:45 -0400
From:	Valdis.Kletnieks@...edu
To:	Marc Perkel <mperkel@...oo.com>
Cc:	Phillip Susi <psusi@....rr.com>,
	Kyle Moffett <mrmacman_g4@....com>,
	Michael Tharp <gxti@...tiallystapled.com>,
	alan <alan@...eserver.org>,
	LKML Kernel <linux-kernel@...r.kernel.org>,
	Lennart Sorensen <lsorense@...lub.uwaterloo.ca>
Subject: Re: Thinking outside the box on file systems

On Wed, 15 Aug 2007 15:48:15 PDT, Marc Perkel said:
> > Consider the rules:
> > 
> > peter '*a*' can create
> > peter '*b*' cannot create
> > 
> > Peter tries to create 'foo-ab-bar' - is he allowed
> > to or not?
> > 
> 
> First - I'm proposing a concept, not writing the
> implementation of the concept. You are asking what
> happens when someone write conflicting rules. That
> depends on how you implement it. Conflicting rules can
> cause unpredictable results.

Good. Go work out what the rules have to be in order for the system to
behave sanely.  "Hand-waving concept" doesn't get anywhere.  Fully fleshed-out
concepts sometimes do - once they sprout code to actually  implement them.

> The point is that one can choose any rule system they
> want and the rules applies to the names of the files
> and the permissions of the users.

No, you *can't* choose any rule system you want - some rule systems are
unworkable because they create security exposures (usually of the
"ln /etc/passwd /tmp/foo" variety, but sometimes race conditions as well).

> > For an exersize, either write a program or do by
> > hand:

> All you would have to do is create a set of rules that
> emulates the current rules and you would have the same
> results.

Good. Go create it. Let us know when you're done.  Remember - not only do
you need to have it generate the same results, you need to find a way to
implement it so that it's somewhere near the same speed as the current code.
If it's 10 times slower, it's not going to fly no matter *how* "cool" it is.

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