mm: migrate: Add a tracepoint for migrate_pages

The pgmigrate_success and pgmigrate_fail vmstat counters tells the user
about migration activity but not the type or the reason. This patch adds
a tracepoint to identify the type of page migration and why the page is
being migrated.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 7bb35ac..5953dc2 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5707,7 +5707,8 @@
 
 		ret = migrate_pages(&cc->migratepages,
 				    alloc_migrate_target,
-				    0, false, MIGRATE_SYNC);
+				    0, false, MIGRATE_SYNC,
+				    MR_CMA);
 	}
 
 	putback_lru_pages(&cc->migratepages);