'Return usage info for volumes attached to vms on
a given host.'

def get_all_volume_usage(self, context, compute_host_bdms):

    vol_usage = []
    for instance_bdms in compute_host_bdms:
        instance = instance_bdms['instance']
        for bdm in instance_bdms['instance_bdms']:
            mountpoint = bdm['device_name']
            if mountpoint.startswith('/dev/'):
                mountpoint = mountpoint[5:]
            volume_id = bdm['volume_id']
            LOG.debug('Trying    to    get    stats    for    the    volume    %s', volume_id, instance=instance)
            vol_stats = self.block_stats(instance, mountpoint)
            if vol_stats:
                stats = dict(volume=volume_id, instance=instance, rd_req=vol_stats[0], rd_bytes=vol_stats[1], wr_req=vol_stats[2], wr_bytes=vol_stats[3])
                LOG.debug('Got    volume    usage    stats    for    the    volume=%(volume)s,    rd_req=%(rd_req)d,    rd_bytes=%(rd_bytes)d,    wr_req=%(wr_req)d,    wr_bytes=%(wr_bytes)d', stats, instance=instance)
                vol_usage.append(stats)
    return vol_usage
