From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jes Sorensen <jes@sgi.com>
Date: Fri, 17 Mar 2006 14:04:10 +0000
Subject: Re: [patch 2/2] mspec driver
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List-Id: <linux-ia64.vger.kernel.org>
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	<20060316163728.06f49c00.akpm@osdl.org>
	<yq0bqw5utyc.fsf_-_@jaguar.mkp.net> <441ABB68.1020502@yahoo.com.au>
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To: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Andrew Morton <akpm@osdl.org>, torvalds@osdl.org, linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org, hch@lst.de, cotte@de.ibm.com, Hugh Dickins <hugh@veritas.com>

>>>>> "Nick" = Nick Piggin <nickpiggin@yahoo.com.au> writes:

Nick> Jes Sorensen wrote:
>> + vma->vm_flags |= (VM_IO | VM_LOCKED | VM_RESERVED | VM_PFNMAP);

Nick> VM_PFNMAP actually has a fairly specific meaning [unlike the
Nick> rest of them :)] so you should be careful with it. Actually if
Nick> you set vm_pgoff in the right way, then that should enable you
Nick> to do COWs on these areas if that is what you want.

Yup, I went through that when I started using it. I think you guided
me through it :-)

We don't want COW here as the access is backed by special behavior in
the memory controller. We only allow shared mappings for that reason.

Cheers,
Jes