f2fs: avoid reverse IO order for NODE and DATA

There is a data race between allocate_data_block() and f2fs_sbumit_page_mbio(),
which incur unnecessary reversed bio submission.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 94bb87d..dc66f16 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -1436,6 +1436,8 @@
 
 	INIT_LIST_HEAD(&sbi->s_list);
 	mutex_init(&sbi->umount_mutex);
+	mutex_init(&sbi->wio_mutex[NODE]);
+	mutex_init(&sbi->wio_mutex[DATA]);
 
 #ifdef CONFIG_F2FS_FS_ENCRYPTION
 	memcpy(sbi->key_prefix, F2FS_KEY_DESC_PREFIX,