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>

4 files changed, 9 insertions, 6 deletions

diff --git a/net/rds/ib_send.c b/net/rds/ib_send.c
index 8557a1cae041..8ac80c1b051e 100644
--- a/net/rds/ib_send.c
+++ b/net/rds/ib_send.c
@@ -492,7 +492,7 @@ int rds_ib_xmit(struct rds_connection *conn, struct rds_message *rm,
 	struct rds_ib_send_work *send = NULL;
 	struct rds_ib_send_work *first;
 	struct rds_ib_send_work *prev;
-	struct ib_send_wr *failed_wr;
+	const struct ib_send_wr *failed_wr;
 	struct scatterlist *scat;
 	u32 pos;
 	u32 i;
@@ -758,7 +758,7 @@ int rds_ib_xmit_atomic(struct rds_connection *conn, struct rm_atomic_op *op)
 {
 	struct rds_ib_connection *ic = conn->c_transport_data;
 	struct rds_ib_send_work *send = NULL;
-	struct ib_send_wr *failed_wr;
+	const struct ib_send_wr *failed_wr;
 	struct rds_ib_device *rds_ibdev;
 	u32 pos;
 	u32 work_alloc;
@@ -849,7 +849,7 @@ int rds_ib_xmit_rdma(struct rds_connection *conn, struct rm_rdma_op *op)
 	struct rds_ib_send_work *send = NULL;
 	struct rds_ib_send_work *first;
 	struct rds_ib_send_work *prev;
-	struct ib_send_wr *failed_wr;
+	const struct ib_send_wr *failed_wr;
 	struct scatterlist *scat;
 	unsigned long len;
 	u64 remote_addr = op->op_remote_addr;
diff --git a/net/sunrpc/xprtrdma/frwr_ops.c b/net/sunrpc/xprtrdma/frwr_ops.c
index a167eebf63d5..1bb00dd6ccdb 100644
--- a/net/sunrpc/xprtrdma/frwr_ops.c
+++ b/net/sunrpc/xprtrdma/frwr_ops.c
@@ -517,7 +517,8 @@ frwr_op_reminv(struct rpcrdma_rep *rep, struct list_head *mrs)
 static void
 frwr_op_unmap_sync(struct rpcrdma_xprt *r_xprt, struct list_head *mrs)
 {
-	struct ib_send_wr *first, **prev, *last, *bad_wr;
+	struct ib_send_wr *first, **prev, *last;
+	const struct ib_send_wr *bad_wr;
 	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
 	struct rpcrdma_frwr *frwr;
 	struct rpcrdma_mr *mr;
diff --git a/net/sunrpc/xprtrdma/svc_rdma_rw.c b/net/sunrpc/xprtrdma/svc_rdma_rw.c
index ce3ea8419704..04cb3363172a 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_rw.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_rw.c
@@ -307,7 +307,8 @@ static int svc_rdma_post_chunk_ctxt(struct svc_rdma_chunk_ctxt *cc)
 {
 	struct svcxprt_rdma *rdma = cc->cc_rdma;
 	struct svc_xprt *xprt = &rdma->sc_xprt;
-	struct ib_send_wr *first_wr, *bad_wr;
+	struct ib_send_wr *first_wr;
+	const struct ib_send_wr *bad_wr;
 	struct list_head *tmp;
 	struct ib_cqe *cqe;
 	int ret;
diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
index 112a15abc4a4..5efeba08918b 100644
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -1559,7 +1559,8 @@ rpcrdma_post_recvs(struct rpcrdma_xprt *r_xprt, bool temp)
 	if (!count)
 		return;
 
-	rc = ib_post_recv(r_xprt->rx_ia.ri_id->qp, wr, &bad_wr);
+	rc = ib_post_recv(r_xprt->rx_ia.ri_id->qp, wr,
+			  (const struct ib_recv_wr **)&bad_wr);
 	if (rc) {
 		for (wr = bad_wr; wr; wr = wr->next) {
 			struct rpcrdma_rep *rep;