mm: fix a regression with HIGHMEM

mm: fix a regression with HIGHMEM

Changeset 7f1290f2f2 ("mm: fix-up zone present pages") tried to fix a
issue when calculating zone->present_pages, but it causes a regression to
32bit systems with HIGHMEM.  With that changeset,
reset_zone_present_pages() resets all zone->present_pages to zero, and
fixup_zone_present_pages() is called to recalculate zone->present_pages
when the boot allocator frees core memory pages into the buddy allocator.
Because highmem pages are not freed by bootmem allocator, all highmem
zones' present_pages becomes zero.

Actually there's no need to recalculate present_pages for the highmem zone
because the bootmem allocator never allocates pages from it.  So fix the
regression by skipping highmem in function reset_zone_present_pages() and
fixup_zone_present_pages().

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Signed-off-by: Jianguo Wu <wujianguo@huawei.com>
Reported-by: Maciej Rutecki <maciej.rutecki@gmail.com>
Tested-by: Maciej Rutecki <maciej.rutecki@gmail.com>
Tested-by: Chris Clayton <chris2553@googlemail.com>
Cc: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Minchan Kim <minchan@kernel.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>