mm/migrate: Introduce migrate_misplaced_page()

mm/migrate: Introduce migrate_misplaced_page()

Add migrate_misplaced_page() which deals with migrating pages from
faults.

This includes adding a new MIGRATE_FAULT migration mode to
deal with the extra page reference required due to having to look up
the page.

Based-on-work-by: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Paul Turner <pjt@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-es03i8ne7xee0981brw40fl5@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>