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Date: Wed, 25 Apr 2007 23:40:37 -0700 (PDT)
From: Christoph Lameter <clameter@sgi.com>
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To: Nick Piggin <nickpiggin@yahoo.com.au>
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       Mel Gorman <mel@skynet.ie>, William Lee Irwin III <wli@holomorphy.com>,
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       Badari Pulavarty <pbadari@gmail.com>,
       Maxim Levitsky <maximlevitsky@gmail.com>
Subject: Re: [00/17] Large Blocksize Support V3
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On Thu, 26 Apr 2007, Nick Piggin wrote:

> > The page cache has no problems supporting things with a block
> > size larger then page size.  Now the block device layer may not
> > have the code to do the scatter gather into small pages and it
> > may not handle buffer heads whose data is split between multiple
> > pages. 
> 
> Yeah, this patch is not really large blocksize support (which we normally
> think of as block size > page cache size).

No? It depends on how you define block size. This patch definitely allows
a set blocksize function call with a size larger than 4k.

> > I suspect what needs to be fixed is the page cache block device
> > interface so that we have helper functions that know how to stuff
> > a single block into several pages.
> 
> I am working now and again on some code to do this, it is a big job but
> I think it is the right way to do it. But it would take a long time to
> get stable and supported by filesystems...

Ummm... We already have a radix tree for this???? What more is needed? You 
just need to go through all filesystems and make them use extends.