rbd: implement ->set_read_only to hook into BLKROSET processing

Implement the ->set_read_only method instead of parsing the actual
ioctl command.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/rbd.c

@@ -692,12 +692,9 @@ static void rbd_release(struct gendisk *disk, fmode_t mode)
 	put_device(&rbd_dev->dev);
 }
 
-static int rbd_ioctl_set_ro(struct rbd_device *rbd_dev, unsigned long arg)
+static int rbd_set_read_only(struct block_device *bdev, bool ro)
 {
-	int ro;
-
-	if (get_user(ro, (int __user *)arg))
-		return -EFAULT;
+	struct rbd_device *rbd_dev = bdev->bd_disk->private_data;
 
 	/*
 	 * Both images mapped read-only and snapshots can't be marked
@@ -710,43 +707,14 @@ static int rbd_ioctl_set_ro(struct rbd_device *rbd_dev, unsigned long arg)
 		rbd_assert(!rbd_is_snap(rbd_dev));
 	}
 
-	/* Let blkdev_roset() handle it */
-	return -ENOTTY;
-}
-
-static int rbd_ioctl(struct block_device *bdev, fmode_t mode,
-			unsigned int cmd, unsigned long arg)
-{
-	struct rbd_device *rbd_dev = bdev->bd_disk->private_data;
-	int ret;
-
-	switch (cmd) {
-	case BLKROSET:
-		ret = rbd_ioctl_set_ro(rbd_dev, arg);
-		break;
-	default:
-		ret = -ENOTTY;
-	}
-
-	return ret;
-}
-
-#ifdef CONFIG_COMPAT
-static int rbd_compat_ioctl(struct block_device *bdev, fmode_t mode,
-				unsigned int cmd, unsigned long arg)
-{
-	return rbd_ioctl(bdev, mode, cmd, arg);
+	return 0;
 }
-#endif /* CONFIG_COMPAT */
 
 static const struct block_device_operations rbd_bd_ops = {
 	.owner			= THIS_MODULE,
 	.open			= rbd_open,
 	.release		= rbd_release,
-	.ioctl			= rbd_ioctl,
-#ifdef CONFIG_COMPAT
-	.compat_ioctl		= rbd_compat_ioctl,
-#endif
+	.set_read_only		= rbd_set_read_only,
 };
 
 /*