RDMA, core and ULPs: Declare ib_post_send() and ib_post_recv() arguments const

Since neither ib_post_send() nor ib_post_recv() modify the data structure
their second argument points at, declare that argument const. This change
makes it necessary to declare the 'bad_wr' argument const too and also to
modify all ULPs that call ib_post_send(), ib_post_recv() or
ib_post_srq_recv(). This patch does not change any functionality but makes
it possible for the compiler to verify whether the
ib_post_(send|recv|srq_recv) really do not modify the posted work request.

To make this possible, only one cast had to be introduce that casts away
constness, namely in rpcrdma_post_recvs(). The only way I can think of to
avoid that cast is to introduce an additional loop in that function or to
change the data type of bad_wr from struct ib_recv_wr ** into int
(an index that refers to an element in the work request list). However,
both approaches would require even more extensive changes than this
patch.

Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/hw/cxgb4/qp.c

@@ -620,7 +620,7 @@ static int build_rdma_read(union t4_wr *wqe, const struct ib_send_wr *wr,
 }
 
 static int build_rdma_recv(struct c4iw_qp *qhp, union t4_recv_wr *wqe,
-			   struct ib_recv_wr *wr, u8 *len16)
+			   const struct ib_recv_wr *wr, u8 *len16)
 {
 	int ret;
 
@@ -634,7 +634,7 @@ static int build_rdma_recv(struct c4iw_qp *qhp, union t4_recv_wr *wqe,
 	return 0;
 }
 
-static int build_srq_recv(union t4_recv_wr *wqe, struct ib_recv_wr *wr,
+static int build_srq_recv(union t4_recv_wr *wqe, const struct ib_recv_wr *wr,
 			  u8 *len16)
 {
 	int ret;
@@ -903,8 +903,9 @@ static int complete_sq_drain_wr(struct c4iw_qp *qhp,
 	return 0;
 }
 
-static int complete_sq_drain_wrs(struct c4iw_qp *qhp, struct ib_send_wr *wr,
-				struct ib_send_wr **bad_wr)
+static int complete_sq_drain_wrs(struct c4iw_qp *qhp,
+				 const struct ib_send_wr *wr,
+				 const struct ib_send_wr **bad_wr)
 {
 	int ret = 0;
 
@@ -919,7 +920,8 @@ static int complete_sq_drain_wrs(struct c4iw_qp *qhp, struct ib_send_wr *wr,
 	return ret;
 }
 
-static void complete_rq_drain_wr(struct c4iw_qp *qhp, struct ib_recv_wr *wr)
+static void complete_rq_drain_wr(struct c4iw_qp *qhp,
+				 const struct ib_recv_wr *wr)
 {
 	struct t4_cqe cqe = {};
 	struct c4iw_cq *rchp;
@@ -951,7 +953,8 @@ static void complete_rq_drain_wr(struct c4iw_qp *qhp, struct ib_recv_wr *wr)
 	}
 }
 
-static void complete_rq_drain_wrs(struct c4iw_qp *qhp, struct ib_recv_wr *wr)
+static void complete_rq_drain_wrs(struct c4iw_qp *qhp,
+				  const struct ib_recv_wr *wr)
 {
 	while (wr) {
 		complete_rq_drain_wr(qhp, wr);
@@ -959,8 +962,8 @@ static void complete_rq_drain_wrs(struct c4iw_qp *qhp, struct ib_recv_wr *wr)
 	}
 }
 
-int c4iw_post_send(struct ib_qp *ibqp, struct ib_send_wr *wr,
-		   struct ib_send_wr **bad_wr)
+int c4iw_post_send(struct ib_qp *ibqp, const struct ib_send_wr *wr,
+		   const struct ib_send_wr **bad_wr)
 {
 	int err = 0;
 	u8 len16 = 0;
@@ -1110,8 +1113,8 @@ int c4iw_post_send(struct ib_qp *ibqp, struct ib_send_wr *wr,
 	return err;
 }
 
-int c4iw_post_receive(struct ib_qp *ibqp, struct ib_recv_wr *wr,
-		      struct ib_recv_wr **bad_wr)
+int c4iw_post_receive(struct ib_qp *ibqp, const struct ib_recv_wr *wr,
+		      const struct ib_recv_wr **bad_wr)
 {
 	int err = 0;
 	struct c4iw_qp *qhp;
@@ -1206,8 +1209,8 @@ static void defer_srq_wr(struct t4_srq *srq, union t4_recv_wr *wqe,
 	t4_srq_produce_pending_wr(srq);
 }
 
-int c4iw_post_srq_recv(struct ib_srq *ibsrq, struct ib_recv_wr *wr,
-		       struct ib_recv_wr **bad_wr)
+int c4iw_post_srq_recv(struct ib_srq *ibsrq, const struct ib_recv_wr *wr,
+		       const struct ib_recv_wr **bad_wr)
 {
 	union t4_recv_wr *wqe, lwqe;
 	struct c4iw_srq *srq;