rbd: revalidate_disk upon rbd resize

If rbd disk is open and rbd resize is done, new size is not
visible by filesystem.  Like is done in virtio-blk and dm driver,
revalidate_disk() permits to update the bd_inode size.
Signed-off-by: Laurent Barbe <laurent@ksperis.com>
Reviewed-by: Alex Elder <elder@inktank.com>

drivers/block/rbd.c

@@ -2781,6 +2781,7 @@ static int rbd_dev_refresh(struct rbd_device *rbd_dev, u64 *hver)
 	else
 		ret = rbd_dev_v2_refresh(rbd_dev, hver);
 	mutex_unlock(&ctl_mutex);
+	revalidate_disk(rbd_dev->disk);
 
 	return ret;
 }