BAD_RING
BAD_RING(vq, "id %u is not a head!\n", last_used);
BAD_RING(vq, "id %u out of range\n", last_used);
BAD_RING(vq, "id %u is not a head!\n", last_used);
BAD_RING(vq, "id %u out of range\n", id);
BAD_RING(vq, "id %u is not a head!\n", id);
BAD_RING(vq, "id %u out of range\n", i);
BAD_RING(vq, "id %u is not a head!\n", i);