prov/efa: Delegate iovec offset calc to utility function

This should correctly point the IOV base pointer to the start of the
data buffer in prefix mode. This accommodates non-contiguous iovec
entries where iov[0] is the prefix and iov[1] points the data buffer, as
well as the previously-supported behavior of a single iovec entry where
the buffer has ample space for the prefix and user data.

Signed-off-by: Darryl Abbate <[email protected]>

prov/efa/src/rdm/efa_rdm_ope.c

@@ -57,10 +57,8 @@ void efa_rdm_txe_construct(struct efa_rdm_ope *txe,
 	txe->cq_entry.len = ofi_total_iov_len(txe->iov, txe->iov_count);
 	txe->cq_entry.buf = OFI_LIKELY(txe->cq_entry.len > 0) ? txe->iov[0].iov_base : NULL;
 
-	if (ep->msg_prefix_size > 0) {
-		assert(txe->iov[0].iov_len >= ep->msg_prefix_size);
-		txe->iov[0].iov_base = (char *)txe->iov[0].iov_base + ep->msg_prefix_size;
-		txe->iov[0].iov_len -= ep->msg_prefix_size;
+	if (ep->user_info->mode & FI_MSG_PREFIX) {
+		ofi_consume_iov(txe->iov, &txe->iov_count, ep->msg_prefix_size);
 	}
 	txe->total_len = ofi_total_iov_len(txe->iov, txe->iov_count);