Re: [patch 1/3] mm: introduce follow_pte()

[Johannes Weiner]

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@xxxxxxxxxxx> 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().
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