We should not check loop+1 with loop end in loop body.  Just duplicate two
lines code to avoid it.

That will help a bit when we have huge amount of pages on system with
16TiB memory.
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Cc: Mel Gorman <mgorman@suse.de>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>