pagemap: redefine callback functions for page table walker

pagemap: redefine callback functions for page table walker

pagemap_pte_range() connected to pmd_entry() does both of pmd loop and pte
loop.  So this patch moves pte part into pagemap_pte() on pte_entry().

We remove VM_SOFTDIRTY check in pagemap_pte_range(), because in the new
page table walker we call __walk_page_range() for each vma separately, so
we never experience multiple vmas in single pgd/pud/pmd/pte loop.

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Matt Mackall <mpm@selenic.com>
Cc: Cliff Wickman <cpw@sgi.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>