iov_bunch_next_chunk
if (!iov_bunch_next_chunk(iob, &chunk, &sz))
extern bool iov_bunch_next_chunk(iov_bunch_t *, caddr_t *, size_t *);
bool iov_bunch_next_chunk(iov_bunch_t *, caddr_t *, uint32_t *);
while (iov_bunch_next_chunk(&iob, &chunk, &chunk_sz)) {