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Date:      Mon, 9 Mar 1998 17:12:24 +0900 (JST)
From:      Michael Hancock <michaelh@cet.co.jp>
To:        Nate Williams <nate@mt.sri.com>
Cc:        Terry Lambert <tlambert@primenet.com>, dima@tejblum.dnttm.rssi.ru, current@FreeBSD.ORG
Subject:   Re: vnode_pager: *** WARNING *** stale FS code in system
Message-ID:  <Pine.SV4.3.95.980309170846.21097F-100000@parkplace.cet.co.jp>
In-Reply-To: <199803090805.BAA16882@mt.sri.com>

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On Mon, 9 Mar 1998, Nate Williams wrote:

> > I think this is good enough to go forward, but you need to understand that
> > with the Heidemann FS stacking framework you can extend the set of VOP's
> > in interesting ways.  For example, suppose you wanted to implement
> > VOP_NEWFEATURE.  You could do the following: 
> > 
> > Layer1 - Supports it and maps results from one below.
> > Layer2 - Doesn't support so does a bypass.
> > Layer3 - Supports it and maps results from one below.
> > Layer4 - Doesn't support so does a bypass.
> > Layer5 - Terminal layer, some support some don't.
> > 
> > I'm not sure traditional OOP can do this and this makes finding good
> > analogies difficult.
> 
> Traditional OOP does this right, since you inherit from the class below
> you, and not from the base class.  If you want to inherit from the base
> class, you inherit from it and not a subclass.

But do you get the mappings from layer1 and layer3?  They both touch the
results that finally get to the top.


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