xprtrdma: Set up an xdr_stream in rpcrdma_marshal_req()

Initialize an xdr_stream at the top of rpcrdma_marshal_req(), and
use it to encode the fixed transport header fields. This xdr_stream
will be used to encode the chunk lists in a subsequent patch.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

net/sunrpc/xprtrdma/rpc_rdma.c

@@ -667,17 +667,20 @@ rpcrdma_unmap_sges(struct rpcrdma_ia *ia, struct rpcrdma_req *req)
  *	%-ENOTCONN if the connection was lost,
  *	%-EAGAIN if not enough pages are available for on-demand reply buffer,
  *	%-ENOBUFS if no MRs are available to register chunks,
+ *	%-EMSGSIZE if the transport header is too small,
  *	%-EIO if a permanent problem occurred while marshaling.
  */
 int
 rpcrdma_marshal_req(struct rpcrdma_xprt *r_xprt, struct rpc_rqst *rqst)
 {
 	struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
+	struct xdr_stream *xdr = &req->rl_stream;
 	enum rpcrdma_chunktype rtype, wtype;
 	struct rpcrdma_msg *headerp;
 	bool ddp_allowed;
 	ssize_t hdrlen;
 	__be32 *iptr;
+	__be32 *p;
 
 #if defined(CONFIG_SUNRPC_BACKCHANNEL)
 	if (test_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state))
@@ -685,11 +688,18 @@ rpcrdma_marshal_req(struct rpcrdma_xprt *r_xprt, struct rpc_rqst *rqst)
 #endif
 
 	headerp = rdmab_to_msg(req->rl_rdmabuf);
-	/* don't byte-swap XID, it's already done in request */
-	headerp->rm_xid = rqst->rq_xid;
-	headerp->rm_vers = rpcrdma_version;
-	headerp->rm_credit = cpu_to_be32(r_xprt->rx_buf.rb_max_requests);
-	headerp->rm_type = rdma_msg;
+	rpcrdma_set_xdrlen(&req->rl_hdrbuf, 0);
+	xdr_init_encode(xdr, &req->rl_hdrbuf,
+			req->rl_rdmabuf->rg_base);
+
+	/* Fixed header fields */
+	iptr = ERR_PTR(-EMSGSIZE);
+	p = xdr_reserve_space(xdr, 4 * sizeof(*p));
+	if (!p)
+		goto out_err;
+	*p++ = rqst->rq_xid;
+	*p++ = rpcrdma_version;
+	*p++ = cpu_to_be32(r_xprt->rx_buf.rb_max_requests);
 
 	/* When the ULP employs a GSS flavor that guarantees integrity
 	 * or privacy, direct data placement of individual data items
@@ -729,12 +739,14 @@ rpcrdma_marshal_req(struct rpcrdma_xprt *r_xprt, struct rpc_rqst *rqst)
 	 * by themselves are larger than the inline threshold.
 	 */
 	if (rpcrdma_args_inline(r_xprt, rqst)) {
+		*p++ = rdma_msg;
 		rtype = rpcrdma_noch;
 	} else if (ddp_allowed && rqst->rq_snd_buf.flags & XDRBUF_WRITE) {
+		*p++ = rdma_msg;
 		rtype = rpcrdma_readch;
 	} else {
 		r_xprt->rx_stats.nomsg_call_count++;
-		headerp->rm_type = htonl(RDMA_NOMSG);
+		*p++ = rdma_nomsg;
 		rtype = rpcrdma_areadch;
 	}
 

net/sunrpc/xprtrdma/transport.c

@@ -559,6 +559,7 @@ rpcrdma_get_rdmabuf(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req,
 
 	r_xprt->rx_stats.hardway_register_count += size;
 	req->rl_rdmabuf = rb;
+	xdr_buf_init(&req->rl_hdrbuf, rb->rg_base, rdmab_length(rb));
 	return true;
 }
 

net/sunrpc/xprtrdma/xprt_rdma.h

@@ -345,6 +345,8 @@ struct rpcrdma_req {
 	unsigned int		rl_connect_cookie;
 	struct rpcrdma_buffer	*rl_buffer;
 	struct rpcrdma_rep	*rl_reply;
+	struct xdr_stream	rl_stream;
+	struct xdr_buf		rl_hdrbuf;
 	struct ib_send_wr	rl_send_wr;
 	struct ib_sge		rl_send_sge[RPCRDMA_MAX_SEND_SGES];
 	struct rpcrdma_regbuf	*rl_rdmabuf;	/* xprt header */