I write a /dev/szk resource manager and a client to test reading bytes from it. In overrided io_read, such values of ocb
->attr->nbytes is 0.

int io_read_valve (resmgr_context_t * ctp, io_read_t * msg, RESMGR_OCB_T * ocb) {
	int status;

	if ((status = iofunc_read_verify (ctp, msg, ocb, NULL)) != EOK) return (status);
        printf("serv: io_read, ocb->attr->nbytes= %d, ocb->offset = %lld, msg->i.nbytes = %d\n", ocb->attr->nbytes, ocb-
>offset, msg->i.nbytes);
       ...
}

In client.c, it read bytes using result = read(fd, buf, 12);

However, the print values are all 0. This is the output result:
serv: io_read, ocb->attr->nbytes = 0, ocb->offset = 0, msg->i.nbytes = 0

Why isn't 12 transferred from client read to io_read ocb->attr->nbytes?