SUNRPC: Clean up request deferral tracepoints

- Rename these so they are easy to enable and search for as a set
- Move the tracepoints to get a more accurate sense of control flow
- Tracepoints should not fire on xprt shutdown
- Display memory address in case data structure had been corrupted
- Abandon dprintk in these paths

I haven't ever gotten one of these tracepoints to trigger. I wonder
if we should simply remove them.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

include/trace/events/sunrpc.h

@@ -1406,27 +1406,32 @@ DECLARE_EVENT_CLASS(svc_deferred_event,
 	TP_ARGS(dr),
 
 	TP_STRUCT__entry(
+		__field(const void *, dr)
 		__field(u32, xid)
 		__string(addr, dr->xprt->xpt_remotebuf)
 	),
 
 	TP_fast_assign(
+		__entry->dr = dr;
 		__entry->xid = be32_to_cpu(*(__be32 *)(dr->args +
 						       (dr->xprt_hlen>>2)));
 		__assign_str(addr, dr->xprt->xpt_remotebuf);
 	),
 
-	TP_printk("addr=%s xid=0x%08x", __get_str(addr), __entry->xid)
+	TP_printk("addr=%s dr=%p xid=0x%08x", __get_str(addr), __entry->dr,
+		__entry->xid)
 );
+
 #define DEFINE_SVC_DEFERRED_EVENT(name) \
-	DEFINE_EVENT(svc_deferred_event, svc_##name##_deferred, \
+	DEFINE_EVENT(svc_deferred_event, svc_defer_##name, \
 			TP_PROTO( \
 				const struct svc_deferred_req *dr \
 			), \
 			TP_ARGS(dr))
 
 DEFINE_SVC_DEFERRED_EVENT(drop);
-DEFINE_SVC_DEFERRED_EVENT(revisit);
+DEFINE_SVC_DEFERRED_EVENT(queue);
+DEFINE_SVC_DEFERRED_EVENT(recv);
 
 TRACE_EVENT(svcsock_new_socket,
 	TP_PROTO(

net/sunrpc/svc_xprt.c

@@ -1145,16 +1145,15 @@ static void svc_revisit(struct cache_deferred_req *dreq, int too_many)
 	set_bit(XPT_DEFERRED, &xprt->xpt_flags);
 	if (too_many || test_bit(XPT_DEAD, &xprt->xpt_flags)) {
 		spin_unlock(&xprt->xpt_lock);
-		dprintk("revisit canceled\n");
+		trace_svc_defer_drop(dr);
 		svc_xprt_put(xprt);
-		trace_svc_drop_deferred(dr);
 		kfree(dr);
 		return;
 	}
-	dprintk("revisit queued\n");
 	dr->xprt = NULL;
 	list_add(&dr->handle.recent, &xprt->xpt_deferred);
 	spin_unlock(&xprt->xpt_lock);
+	trace_svc_defer_queue(dr);
 	svc_xprt_enqueue(xprt);
 	svc_xprt_put(xprt);
 }
@@ -1200,22 +1199,24 @@ static struct cache_deferred_req *svc_defer(struct cache_req *req)
 		memcpy(dr->args, rqstp->rq_arg.head[0].iov_base - skip,
 		       dr->argslen << 2);
 	}
+	trace_svc_defer(rqstp);
 	svc_xprt_get(rqstp->rq_xprt);
 	dr->xprt = rqstp->rq_xprt;
 	set_bit(RQ_DROPME, &rqstp->rq_flags);
 
 	dr->handle.revisit = svc_revisit;
-	trace_svc_defer(rqstp);
 	return &dr->handle;
 }
 
 /*
  * recv data from a deferred request into an active one
  */
-static int svc_deferred_recv(struct svc_rqst *rqstp)
+static noinline int svc_deferred_recv(struct svc_rqst *rqstp)
 {
 	struct svc_deferred_req *dr = rqstp->rq_deferred;
 
+	trace_svc_defer_recv(dr);
+
 	/* setup iov_base past transport header */
 	rqstp->rq_arg.head[0].iov_base = dr->args + (dr->xprt_hlen>>2);
 	/* The iov_len does not include the transport header bytes */
@@ -1246,7 +1247,6 @@ static struct svc_deferred_req *svc_deferred_dequeue(struct svc_xprt *xprt)
 				struct svc_deferred_req,
 				handle.recent);
 		list_del_init(&dr->handle.recent);
-		trace_svc_revisit_deferred(dr);
 	} else
 		clear_bit(XPT_DEFERRED, &xprt->xpt_flags);
 	spin_unlock(&xprt->xpt_lock);