The follow_page write-access case is relying on pte_page before checking
pfn_valid: rearrange that - and we don't need three struct page *pages.

(I notice mempolicy.c's verify_pages is also relying on pte_page, but I'll
leave that to Andi: maybe it ought to be failing on, or skipping over, VM_IO
or VM_RESERVED vmas?)
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>