f2fs: support read iostat

Adds to support accounting read IOs from userspace/kernel.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index ecbd6bd1..4da0d87 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -1300,7 +1300,13 @@ static int read_node_page(struct page *page, int op_flags)
 	}
 
 	fio.new_blkaddr = fio.old_blkaddr = ni.blk_addr;
-	return f2fs_submit_page_bio(&fio);
+
+	err = f2fs_submit_page_bio(&fio);
+
+	if (!err)
+		f2fs_update_iostat(sbi, FS_NODE_READ_IO, F2FS_BLKSIZE);
+
+	return err;
 }
 
 /*