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SubjectRe: [patch 1/3] mm: introduce follow_pte()
On Tue, 5 May 2009 22:38:07 +0200
Johannes Weiner <hannes@cmpxchg.org> wrote:

> On Tue, May 05, 2009 at 12:24:42PM -0700, Andrew Morton wrote:
> > On Mon, 4 May 2009 11:54:32 +0200
> > Johannes Weiner <hannes@cmpxchg.org> wrote:
> >
> > > A generic readonly page table lookup helper to map an address space
> > > and an address from it to a pte.
> >
> > umm, OK.
> >
> > Is there actually some point to these three patches? If so, what is it?
>
> Magnus needs to check for physical contiguity of a VMAs backing pages
> to support zero-copy exportation of video data to userspace.
>
> This series implements follow_pfn() so he can walk the VMA backing
> pages and ensure their PFNs are in linear order.
>
> [ This patch can be collapsed with 2/3, I just thought it would be
> easier to read the diffs when having them separate. ]
>
> 1/3 and 2/3: factor out the page table walk from follow_phys() into
> follow_pte().
>
> 3/3: implement follow_pfn() on top of follow_pte().

So we could bundle these patches with Magnus's patchset, or we could
consider these three patches as a cleanup or something.

Given that 3/3 introduces an unused function, I'm inclined to sit tight
and await Magnus's work.



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