ext4: hard fail dax mount on unsupported devices

As dax inches closer to production use, an administrator should not
be surprised by silently disabling the feature they asked for.
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/super.c

@@ -3864,12 +3864,12 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 		if (ext4_has_feature_inline_data(sb)) {
 			ext4_msg(sb, KERN_ERR, "Cannot use DAX on a filesystem"
 					" that may contain inline data");
-			sbi->s_mount_opt &= ~EXT4_MOUNT_DAX;
+			goto failed_mount;
 		}
 		if (!bdev_dax_supported(sb->s_bdev, blocksize)) {
 			ext4_msg(sb, KERN_ERR,
-				"DAX unsupported by block device. Turning off DAX.");
-			sbi->s_mount_opt &= ~EXT4_MOUNT_DAX;
+				"DAX unsupported by block device.");
+			goto failed_mount;
 		}
 	}