count_iov
total = count_iov(iov, niov);
size_t count_iov(const struct iovec *, size_t);
EPRINTLN("No space, drop %zu bytes", count_iov(iov, iovcnt));
count_iov(iov, iovcnt));
info[n_chains].len = (uint32_t)count_iov(riov, n);
ext_data_len = count_iov(req->vsr_data_iov_in,
ext_data_len = count_iov(req->vsr_data_iov_out,