Isolated free pages shouldn't be accounted to NR_FREE_PAGES counter.
Fix it by properly decreasing/increasing NR_FREE_PAGES counter in
set_migratetype_isolate()/unset_migratetype_isolate() and removing
counter adjustment for isolated pages from free_one_page() and
split_free_page().

Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Michal Nazarewicz <redacted>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <redacted>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
---
 mm/page_alloc.c     |  7 +++++--
 mm/page_isolation.c | 13 ++++++++++---
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e9da55c..3acdf0f 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c

@@ -691,7 +691,8 @@ static void free_one_page(struct zone *zone, struct page *page, int order,
 	zone->pages_scanned = 0;
 
 	__free_one_page(page, zone, order, migratetype);
-	__mod_zone_page_state(zone, NR_FREE_PAGES, 1 << order);
+	if (migratetype != MIGRATE_ISOLATE)

+		__mod_zone_page_state(zone, NR_FREE_PAGES, 1 << order);
 	spin_unlock(&zone->lock);
 }
 

@@ -1414,7 +1415,9 @@ int split_free_page(struct page *page, bool check_wmark)
 	list_del(&page->lru);
 	zone->free_area[order].nr_free--;
 	rmv_page_order(page);
-	__mod_zone_page_state(zone, NR_FREE_PAGES, -(1UL << order));
+
+	if (get_pageblock_migratetype(page) != MIGRATE_ISOLATE)