Btrfs: disable qgroup id 0

Qgroup id 0 is a special number, we should set the id of a qgroup to 0.
Fix it.
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>

fs/btrfs/ioctl.c

@@ -3698,6 +3698,11 @@ static long btrfs_ioctl_qgroup_create(struct file *file, void __user *arg)
 		goto drop_write;
 	}
 
+	if (!sa->qgroupid) {
+		ret = -EINVAL;
+		goto out;
+	}
+
 	trans = btrfs_join_transaction(root);
 	if (IS_ERR(trans)) {
 		ret = PTR_ERR(trans);