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Date: Tue, 3 Sep 2002 18:23:02 +0200
From: Lars Marowsky-Bree <lmb@suse.de>
To: "Peter T. Breuer" <ptb@it.uc3m.es>
Cc: linux kernel <linux-kernel@vger.kernel.org>
Subject: Re: [RFC] mount flag "direct"
Message-ID: <20020903162302.GD2344@marowsky-bree.de>
References: <Pine.SOL.3.96.1020903163309.14707D-100000@libra.cus.cam.ac.uk> <200209031544.g83FiAG03134@oboe.it.uc3m.es>
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On 2002-09-03T17:44:10,
   "Peter T. Breuer" <ptb@it.uc3m.es> said:

> No! I do not want /A/ fs, but /any/ fs, and I want to add the vfs
> support necessary :-).
> 
> That's really what my question is driving at. I see that I need to
> make VFS ops communicate "tag requests" to the block layer, in
> order to implement locking. Now you and Rik have pointed out one
> operation that needs locking. My next question is obviously: can you
> point me more or less precisely at this operation in the VFS layer?
> I've only started studying it and I am relatively unfamiliar with it.

Your approach is not feasible.

Distributed filesystems have a lot of subtle pitfalls - locking, cache
coherency, journal replay to name a few - which you can hardly solve at the
VFS layer.

Good reading would be any sort of entry literature on clustering, I would
recommend "In search of clusters" and many of the whitepapers Google will turn
up for you, as well as the OpenGFS source.


Sincerely,
    Lars Marowsky-Br?e <lmb@suse.de>

-- 
Immortality is an adequate definition of high availability for me.
	--- Gregory F. Pfister

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