cma: count free CMA pages

Add NR_FREE_CMA_PAGES counter to be later used for checking watermark in
__zone_watermark_ok().  For simplicity and to avoid #ifdef hell make this
counter always available (not only when CONFIG_CMA=y).

[akpm@linux-foundation.org: use conventional migratetype naming]
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index 3ca1716..345643b 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -77,11 +77,12 @@
 out:
 	if (!ret) {
 		unsigned long nr_pages;
+		int migratetype = get_pageblock_migratetype(page);
 
 		set_pageblock_isolate(page);
 		nr_pages = move_freepages_block(zone, page, MIGRATE_ISOLATE);
 
-		__mod_zone_page_state(zone, NR_FREE_PAGES, -nr_pages);
+		__mod_zone_freepage_state(zone, -nr_pages, migratetype);
 	}
 
 	spin_unlock_irqrestore(&zone->lock, flags);
@@ -100,7 +101,7 @@
 	if (get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
 		goto out;
 	nr_pages = move_freepages_block(zone, page, migratetype);
-	__mod_zone_page_state(zone, NR_FREE_PAGES, nr_pages);
+	__mod_zone_freepage_state(zone, nr_pages, migratetype);
 	restore_pageblock_isolate(page, migratetype);
 out:
 	spin_unlock_irqrestore(&zone->lock, flags);