svcrdma: Create a generic tracing class for displaying xdr_buf layout

This class can be used to create trace points in either the RPC
client or RPC server paths. It simply displays the length of each
part of an xdr_buf, which is useful to determine that the transport
and XDR codecs are operating correctly.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

include/trace/events/sunrpc.h

@@ -14,6 +14,49 @@
 #include <linux/net.h>
 #include <linux/tracepoint.h>
 
+DECLARE_EVENT_CLASS(xdr_buf_class,
+	TP_PROTO(
+		const struct xdr_buf *xdr
+	),
+
+	TP_ARGS(xdr),
+
+	TP_STRUCT__entry(
+		__field(const void *, head_base)
+		__field(size_t, head_len)
+		__field(const void *, tail_base)
+		__field(size_t, tail_len)
+		__field(unsigned int, page_len)
+		__field(unsigned int, msg_len)
+	),
+
+	TP_fast_assign(
+		__entry->head_base = xdr->head[0].iov_base;
+		__entry->head_len = xdr->head[0].iov_len;
+		__entry->tail_base = xdr->tail[0].iov_base;
+		__entry->tail_len = xdr->tail[0].iov_len;
+		__entry->page_len = xdr->page_len;
+		__entry->msg_len = xdr->len;
+	),
+
+	TP_printk("head=[%p,%zu] page=%u tail=[%p,%zu] len=%u",
+		__entry->head_base, __entry->head_len, __entry->page_len,
+		__entry->tail_base, __entry->tail_len, __entry->msg_len
+	)
+);
+
+#define DEFINE_XDRBUF_EVENT(name)					\
+		DEFINE_EVENT(xdr_buf_class, name,			\
+				TP_PROTO(				\
+					const struct xdr_buf *xdr	\
+				),					\
+				TP_ARGS(xdr))
+
+DEFINE_XDRBUF_EVENT(xprt_sendto);
+DEFINE_XDRBUF_EVENT(xprt_recvfrom);
+DEFINE_XDRBUF_EVENT(svc_recvfrom);
+DEFINE_XDRBUF_EVENT(svc_sendto);
+
 TRACE_DEFINE_ENUM(RPC_AUTH_OK);
 TRACE_DEFINE_ENUM(RPC_AUTH_BADCRED);
 TRACE_DEFINE_ENUM(RPC_AUTH_REJECTEDCRED);

net/sunrpc/clnt.c

@@ -2509,6 +2509,7 @@ call_decode(struct rpc_task *task)
 		goto out;
 
 	req->rq_rcv_buf.len = req->rq_private_buf.len;
+	trace_xprt_recvfrom(&req->rq_rcv_buf);
 
 	/* Check that the softirq receive buffer is valid */
 	WARN_ON(memcmp(&req->rq_rcv_buf, &req->rq_private_buf,

net/sunrpc/svc_xprt.c

@@ -802,6 +802,8 @@ static int svc_handle_xprt(struct svc_rqst *rqstp, struct svc_xprt *xprt)
 			len = svc_deferred_recv(rqstp);
 		else
 			len = xprt->xpt_ops->xpo_recvfrom(rqstp);
+		if (len > 0)
+			trace_svc_recvfrom(&rqstp->rq_arg);
 		rqstp->rq_stime = ktime_get();
 		rqstp->rq_reserved = serv->sv_max_mesg;
 		atomic_add(rqstp->rq_reserved, &xprt->xpt_reserved);
@@ -905,6 +907,7 @@ int svc_send(struct svc_rqst *rqstp)
 	xb->len = xb->head[0].iov_len +
 		xb->page_len +
 		xb->tail[0].iov_len;
+	trace_svc_sendto(xb);
 
 	/* Grab mutex to serialize outgoing data. */
 	mutex_lock(&xprt->xpt_mutex);

net/sunrpc/xprt.c

@@ -1117,8 +1117,6 @@ void xprt_complete_rqst(struct rpc_task *task, int copied)
 	struct rpc_rqst *req = task->tk_rqstp;
 	struct rpc_xprt *xprt = req->rq_xprt;
 
-	dprintk("RPC: %5u xid %08x complete (%d bytes received)\n",
-			task->tk_pid, ntohl(req->rq_xid), copied);
 	trace_xprt_complete_rqst(xprt, req->rq_xid, copied);
 
 	xprt->stat.recvs++;
@@ -1462,6 +1460,7 @@ xprt_request_transmit(struct rpc_rqst *req, struct rpc_task *snd_task)
 	 */
 	req->rq_ntrans++;
 
+	trace_xprt_sendto(&req->rq_snd_buf);
 	connect_cookie = xprt->connect_cookie;
 	status = xprt->ops->send_request(req);
 	if (status != 0) {