sglist_count
KKASSERT(sglist_count(&req->vbr_hdr, sizeof(req->vbr_hdr))
KKASSERT(sglist_count(&req->vbr_ack, sizeof(req->vbr_ack))
req_nsegs = sglist_count(&req->vsr_ureq, sizeof(req->vsr_ureq));
resp_nsegs = sglist_count(&req->vsr_uresp, sizeof(req->vsr_uresp));
nsegs = sglist_count(buf, len);
int sglist_count(void *buf, size_t len);