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To: Hans Reiser <reiser@namesys.com>
Cc: Mark Hahn <hahn@physics.mcmaster.ca>, Rik van Riel <riel@conectiva.com.br>,
        linux-kernel@vger.kernel.org
Subject: Re: Possible Idea with filesystem buffering.
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From: ebiederm@xmission.com (Eric W. Biederman)
Date: 21 Jan 2002 08:37:12 -0700
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Hans Reiser <reiser@namesys.com> writes:

> Mark Hahn wrote:
> 
> >On Sun, 20 Jan 2002, Hans Reiser wrote:
> >
> >> Write clustering is one thing it achieves.   When we flush a slum, the
> >
> >sure, that's fine.  when the VM tells you to write a page,
> >you're free to write *more*, but you certainly must give back
> > that particular page.  afaicr, this was the conclusion of the long-ago thread
> > that you're referring to.
> >
> >regards, mark hahn.
> >
> >
> >
> This is bad for use with internal nodes.  It simplifies version 4 a bunch to
> assume that if a node is in cache, its parent is also.  Not sure what to do
> about it, maybe we need to copy the node.  Surely we don't want to copy it
> unless it is a DMA related page cleaning.

Increment the count on the parent page, and don't decrement it until
the child goes away.  This might need a notification from
page_cache_release when so you can decrement the count at the
appropriate time.  But internal nodes are ``meta'' data which has
always had special freeing rules.

Eric
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