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/nes/nes_verbs.c

@@ -3067,8 +3067,8 @@ fill_wqe_sg_send(struct nes_hw_qp_wqe *wqe, const struct ib_send_wr *ib_wr,
 /**
  * nes_post_send
  */
-static int nes_post_send(struct ib_qp *ibqp, struct ib_send_wr *ib_wr,
-		struct ib_send_wr **bad_wr)
+static int nes_post_send(struct ib_qp *ibqp, const struct ib_send_wr *ib_wr,
+			 const struct ib_send_wr **bad_wr)
 {
 	u64 u64temp;
 	unsigned long flags = 0;
@@ -3329,8 +3329,8 @@ out:
 /**
  * nes_post_recv
  */
-static int nes_post_recv(struct ib_qp *ibqp, struct ib_recv_wr *ib_wr,
-		struct ib_recv_wr **bad_wr)
+static int nes_post_recv(struct ib_qp *ibqp, const struct ib_recv_wr *ib_wr,
+			 const struct ib_recv_wr **bad_wr)
 {
 	u64 u64temp;
 	unsigned long flags = 0;