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/cxgb3/iwch_qp.c

@@ -246,7 +246,7 @@ static int iwch_sgl2pbl_map(struct iwch_dev *rhp, struct ib_sge *sg_list,
 }
 
 static int build_rdma_recv(struct iwch_qp *qhp, union t3_wr *wqe,
-				struct ib_recv_wr *wr)
+			   const struct ib_recv_wr *wr)
 {
 	int i, err = 0;
 	u32 pbl_addr[T3_MAX_SGE];
@@ -286,7 +286,7 @@ static int build_rdma_recv(struct iwch_qp *qhp, union t3_wr *wqe,
 }
 
 static int build_zero_stag_recv(struct iwch_qp *qhp, union t3_wr *wqe,
-				struct ib_recv_wr *wr)
+				const struct ib_recv_wr *wr)
 {
 	int i;
 	u32 pbl_addr;
@@ -348,8 +348,8 @@ static int build_zero_stag_recv(struct iwch_qp *qhp, union t3_wr *wqe,
 	return 0;
 }
 
-int iwch_post_send(struct ib_qp *ibqp, struct ib_send_wr *wr,
-		      struct ib_send_wr **bad_wr)
+int iwch_post_send(struct ib_qp *ibqp, const struct ib_send_wr *wr,
+		   const struct ib_send_wr **bad_wr)
 {
 	int err = 0;
 	u8 uninitialized_var(t3_wr_flit_cnt);
@@ -463,8 +463,8 @@ out:
 	return err;
 }
 
-int iwch_post_receive(struct ib_qp *ibqp, struct ib_recv_wr *wr,
-		      struct ib_recv_wr **bad_wr)
+int iwch_post_receive(struct ib_qp *ibqp, const struct ib_recv_wr *wr,
+		      const struct ib_recv_wr **bad_wr)
 {
 	int err = 0;
 	struct iwch_qp *qhp;