f2fs: add a tracepoint for f2fs_write_{meta,node,data}_page

This patch adds a tracepoint for f2fs_write_{meta,node,data}_page to trace when
page is writting out.

Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index 059aaf5..49bdddb 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -1199,6 +1199,8 @@
 		.rw = (wbc->sync_mode == WB_SYNC_ALL) ? WRITE_SYNC : WRITE,
 	};
 
+	trace_f2fs_writepage(page, NODE);
+
 	if (unlikely(sbi->por_doing))
 		goto redirty_out;