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Subject: Re: [RFC][patch 0/2] mm: remove PageReserved
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Russell King <rmk+lkml@arm.linux.org.uk>
Cc: "Martin J. Bligh" <mbligh@mbligh.org>,
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Date: Wed, 10 Aug 2005 11:27:24 +0200
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On Tue, 2005-08-09 at 20:41 +0100, Russell King wrote:
> On Tue, Aug 09, 2005 at 07:38:52AM -0700, Martin J. Bligh wrote:
> > pfn_valid() doesn't tell you it's RAM or not - it tells you whether you
> > have a backing struct page for that address. Could be an IO mapped device,
> > a small memory hole, whatever.
> 
> The only things which have a struct page is RAM.  Nothing else does.

Well, not anymore :)

With sparsemem, you can cheat now and have struct page for non-RAM, and
this is actually useful. I want some IO space to be "context switchable"
and thus map it with nopage() functionality, etc...

Ben.