RDMA/rxe: Remove unused pkt->offset

The pkt->offset field is never used except to assign it to 0.  But it adds
lots of unneeded code. This patch removes the field and related code. This
causes a measurable improvement in performance.

Link: https://lore.kernel.org/r/20210211210455.3274-1-rpearson@hpe.comSigned-off-by: Bob Pearson <rpearson@hpe.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/sw/rxe/rxe_recv.c

@@ -353,9 +353,7 @@ void rxe_rcv(struct sk_buff *skb)
 	__be32 *icrcp;
 	u32 calc_icrc, pack_icrc;
 
-	pkt->offset = 0;
-
-	if (unlikely(skb->len < pkt->offset + RXE_BTH_BYTES))
+	if (unlikely(skb->len < RXE_BTH_BYTES))
 		goto drop;
 
 	if (rxe_chk_dgid(rxe, skb) < 0) {

drivers/infiniband/sw/rxe/rxe_req.c

@@ -375,7 +375,6 @@ static struct sk_buff *init_req_packet(struct rxe_qp *qp,
 	pkt->psn	= qp->req.psn;
 	pkt->mask	= rxe_opcode[opcode].mask;
 	pkt->paylen	= paylen;
-	pkt->offset	= 0;
 	pkt->wqe	= wqe;
 
 	/* init skb */

drivers/infiniband/sw/rxe/rxe_resp.c

@@ -586,11 +586,10 @@ static struct sk_buff *prepare_ack_packet(struct rxe_qp *qp,
 	ack->qp = qp;
 	ack->opcode = opcode;
 	ack->mask = rxe_opcode[opcode].mask;
-	ack->offset = pkt->offset;
 	ack->paylen = paylen;
 
 	/* fill in bth using the request packet headers */
-	memcpy(ack->hdr, pkt->hdr, pkt->offset + RXE_BTH_BYTES);
+	memcpy(ack->hdr, pkt->hdr, RXE_BTH_BYTES);
 
 	bth_set_opcode(ack, opcode);
 	bth_set_qpn(ack, qp->attr.dest_qp_num);