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/include/linux/vmstat.h b/include/linux/vmstat.h
index ad2cfd5..a5bb150 100644
--- a/include/linux/vmstat.h
+++ b/include/linux/vmstat.h
@@ -253,6 +253,14 @@
 
 #endif		/* CONFIG_SMP */
 
+static inline void __mod_zone_freepage_state(struct zone *zone, int nr_pages,
+					     int migratetype)
+{
+	__mod_zone_page_state(zone, NR_FREE_PAGES, nr_pages);
+	if (is_migrate_cma(migratetype))
+		__mod_zone_page_state(zone, NR_FREE_CMA_PAGES, nr_pages);
+}
+
 extern const char * const vmstat_text[];
 
 #endif /* _LINUX_VMSTAT_H */