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Message-ID: <20070420165135.GB30100@kernel.dk>
Date: Fri, 20 Apr 2007 18:51:36 +0200
From: Jens Axboe <jens.axboe@...cle.com>
To: Christoph Lameter <clameter@....com>
Cc: Adam Litke <aglitke@...il.com>, linux-kernel@...r.kernel.org,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Nick Piggin <nickpiggin@...oo.com.au>, Andi Kleen <ak@...e.de>,
Paul Jackson <pj@....com>, Dave Chinner <dgc@....com>
Subject: Re: [RFC 4/8] Enhance fallback functions in libs to support higher order pages
On Fri, Apr 20 2007, Christoph Lameter wrote:
> On Fri, 20 Apr 2007, Jens Axboe wrote:
>
> > This works fine as long as you are in the submitter context, but once
> > you pass the into the block layer, we don't have any way to find the
> > address space (at least we don't want to). Would something like this be
> > workable, name withstanding:
> >
> > static unsigned long page_size(struct page *page)
> > {
> > struct address_space *mapping;
> > int order = 0;
> >
> > mapping = page_mapping(page);
> > if (mapping)
> > order = mapping->order;
> >
> > return PAGE_CACHE_SIZE << order;
> > }
>
> There is much simpler solution (possible with mm)
>
> PAGE_SIZE << compound_order(page)
>
> compound_order will return 0 for a non compound page.
Ah perfect, much easier. I'll spin a patchset for the block bits.
--
Jens Axboe
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