def set_bdev_qos_limit(client, name, rw_ios_per_sec=None, rw_mbytes_per_sec=None):
    """Set QoS rate limit on a block device.

    Args:
        name: name of block device
        rw_ios_per_sec: R/W IOs per second limit (>=10000, example: 20000). 0 means unlimited.
        rw_mbytes_per_sec: R/W megabytes per second limit (>=10, example: 100). 0 means unlimited.
    """
    params = {}
    params['name'] = name
    if rw_ios_per_sec is not None:
        params['rw_ios_per_sec'] = rw_ios_per_sec
    if rw_mbytes_per_sec is not None:
        params['rw_mbytes_per_sec'] = rw_mbytes_per_sec
    return client.call('set_bdev_qos_limit', params)