diff --git a/block/ioctl.c b/block/ioctl.c
index ca939fc..d510c2a 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -180,6 +180,26 @@
 EXPORT_SYMBOL_GPL(__blkdev_driver_ioctl);
 
 /*
+ * Is it an unrecognized ioctl? The correct returns are either
+ * ENOTTY (final) or ENOIOCTLCMD ("I don't know this one, try a
+ * fallback"). ENOIOCTLCMD gets turned into ENOTTY by the ioctl
+ * code before returning.
+ *
+ * Confused drivers sometimes return EINVAL, which is wrong. It
+ * means "I understood the ioctl command, but the parameters to
+ * it were wrong".
+ *
+ * We should aim to just fix the broken drivers, the EINVAL case
+ * should go away.
+ */
+static inline int is_unrecognized_ioctl(int ret)
+{
+	return	ret == -EINVAL ||
+		ret == -ENOTTY ||
+		ret == -ENOIOCTLCMD;
+}
+
+/*
  * always keep this in sync with compat_blkdev_ioctl()
  */
 int blkdev_ioctl(struct block_device *bdev, fmode_t mode, unsigned cmd,
@@ -196,8 +216,7 @@
 			return -EACCES;
 
 		ret = __blkdev_driver_ioctl(bdev, mode, cmd, arg);
-		/* -EINVAL to handle old uncorrected drivers */
-		if (ret != -EINVAL && ret != -ENOTTY)
+		if (!is_unrecognized_ioctl(ret))
 			return ret;
 
 		fsync_bdev(bdev);
@@ -206,8 +225,7 @@
 
 	case BLKROSET:
 		ret = __blkdev_driver_ioctl(bdev, mode, cmd, arg);
-		/* -EINVAL to handle old uncorrected drivers */
-		if (ret != -EINVAL && ret != -ENOTTY)
+		if (!is_unrecognized_ioctl(ret))
 			return ret;
 		if (!capable(CAP_SYS_ADMIN))
 			return -EACCES;