On Tue, Jun 15, 2021 at 02:21:18PM -0700, Kees Cook wrote:

-	if (!dev || !dev->total_size || !dev->read || !dev->write)
+	if (!dev || !dev->total_size || !dev->read || !dev->write) {
+		if (!dev)
+			pr_err("NULL device info\n");
+		else {
+			if (!dev->total_size)
+				pr_err("zero sized device\n");
+			if (!dev->read)
+				pr_err("no read handler for device\n");
+			if (!dev->write)
+				pr_err("no write handler for device\n");
+		}
 		return -EINVAL;
+	}

I still find this style of checks pretty strange..