rbd: remove the ->set_read_only method

Now that the hardware read-only state can't be changed by the BLKROSET
ioctl, the code in this method is not required anymore.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Acked-by: NIlya Dryomov <idryomov@gmail.com>
Reviewed-by: NMartin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

drivers/block/rbd.c

@@ -692,29 +692,10 @@ static void rbd_release(struct gendisk *disk, fmode_t mode)
 	put_device(&rbd_dev->dev);
 }
 
-static int rbd_set_read_only(struct block_device *bdev, bool ro)
-{
-	struct rbd_device *rbd_dev = bdev->bd_disk->private_data;
-
-	/*
-	 * Both images mapped read-only and snapshots can't be marked
-	 * read-write.
-	 */
-	if (!ro) {
-		if (rbd_is_ro(rbd_dev))
-			return -EROFS;
-
-		rbd_assert(!rbd_is_snap(rbd_dev));
-	}
-
-	return 0;
-}
-
 static const struct block_device_operations rbd_bd_ops = {
 	.owner			= THIS_MODULE,
 	.open			= rbd_open,
 	.release		= rbd_release,
-	.set_read_only		= rbd_set_read_only,
 };
 
 /*