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/mlx4/qp.c

@@ -3569,8 +3569,8 @@ static void add_zero_len_inline(void *wqe)
 	inl->byte_count = cpu_to_be32(1 << 31);
 }
 
-static int _mlx4_ib_post_send(struct ib_qp *ibqp, struct ib_send_wr *wr,
-			      struct ib_send_wr **bad_wr, bool drain)
+static int _mlx4_ib_post_send(struct ib_qp *ibqp, const struct ib_send_wr *wr,
+			      const struct ib_send_wr **bad_wr, bool drain)
 {
 	struct mlx4_ib_qp *qp = to_mqp(ibqp);
 	void *wqe;
@@ -3901,14 +3901,14 @@ out:
 	return err;
 }
 
-int mlx4_ib_post_send(struct ib_qp *ibqp, struct ib_send_wr *wr,
-		      struct ib_send_wr **bad_wr)
+int mlx4_ib_post_send(struct ib_qp *ibqp, const struct ib_send_wr *wr,
+		      const struct ib_send_wr **bad_wr)
 {
 	return _mlx4_ib_post_send(ibqp, wr, bad_wr, false);
 }
 
-static int _mlx4_ib_post_recv(struct ib_qp *ibqp, struct ib_recv_wr *wr,
-			      struct ib_recv_wr **bad_wr, bool drain)
+static int _mlx4_ib_post_recv(struct ib_qp *ibqp, const struct ib_recv_wr *wr,
+			      const struct ib_recv_wr **bad_wr, bool drain)
 {
 	struct mlx4_ib_qp *qp = to_mqp(ibqp);
 	struct mlx4_wqe_data_seg *scat;
@@ -3995,8 +3995,8 @@ out:
 	return err;
 }
 
-int mlx4_ib_post_recv(struct ib_qp *ibqp, struct ib_recv_wr *wr,
-		      struct ib_recv_wr **bad_wr)
+int mlx4_ib_post_recv(struct ib_qp *ibqp, const struct ib_recv_wr *wr,
+		      const struct ib_recv_wr **bad_wr)
 {
 	return _mlx4_ib_post_recv(ibqp, wr, bad_wr, false);
 }
@@ -4536,7 +4536,7 @@ void mlx4_ib_drain_sq(struct ib_qp *qp)
 	struct ib_cq *cq = qp->send_cq;
 	struct ib_qp_attr attr = { .qp_state = IB_QPS_ERR };
 	struct mlx4_ib_drain_cqe sdrain;
-	struct ib_send_wr *bad_swr;
+	const struct ib_send_wr *bad_swr;
 	struct ib_rdma_wr swr = {
 		.wr = {
 			.next = NULL,
@@ -4571,7 +4571,8 @@ void mlx4_ib_drain_rq(struct ib_qp *qp)
 	struct ib_cq *cq = qp->recv_cq;
 	struct ib_qp_attr attr = { .qp_state = IB_QPS_ERR };
 	struct mlx4_ib_drain_cqe rdrain;
-	struct ib_recv_wr rwr = {}, *bad_rwr;
+	struct ib_recv_wr rwr = {};
+	const struct ib_recv_wr *bad_rwr;
 	int ret;
 	struct mlx4_ib_dev *dev = to_mdev(qp->device);
 	struct mlx4_dev *mdev = dev->dev;