--- ufs/super.c	2015-09-26 17:18:46.000000000 +0800
+++ work/super.c	2015-10-12 23:46:40.964962685 +0800
@@ -805,6 +805,7 @@
 	UFSD("flag %u\n", (int)(sb->s_flags & MS_RDONLY));
 	
 	mutex_init(&sbi->mutex);
+	mutex_init(&sbi->s_lock);
 	spin_lock_init(&sbi->work_lock);
 	INIT_DELAYED_WORK(&sbi->sync_work, delayed_sync_fs);
 	/*