NFSv4.1: add tracepoint to trunked nfs4_exchange_id calls

Add a tracepoint to track when the client sends EXCHANGE_ID to test
a new transport for session trunking.

nfs4_detect_session_trunking() tests for trunking and returns
EINVAL if trunking can't be done, add EINVAL mapping to
show_nfs4_status() in tracepoints.

Signed-off-by: Olga Kornievskaia <[e-mail]>
Reviewed-by: Benjamin Coddington <[e-mail]>
Signed-off-by: Trond Myklebust <[e-mail]>

fs/nfs/nfs4proc.c

···
 		return;
 
 	status = task->tk_status;
-	if (status == 0)
+	if (status == 0) {
 		status = nfs4_detect_session_trunking(adata->clp,
 				task->tk_msg.rpc_resp, xprt);
-
+		trace_nfs4_trunked_exchange_id(adata->clp,
+			xprt->address_strings[RPC_DISPLAY_ADDR], status);
+	}
 	if (status == 0)
 		rpc_clnt_xprt_switch_add_xprt(clnt, xprt);
 	else if (status != -NFS4ERR_DELAY && rpc_clnt_xprt_switch_has_addr(clnt,

fs/nfs/nfs4trace.h

···
 DEFINE_NFS4_CLIENTID_EVENT(nfs4_sequence);
 DEFINE_NFS4_CLIENTID_EVENT(nfs4_reclaim_complete);
 
+TRACE_EVENT(nfs4_trunked_exchange_id,
+		TP_PROTO(
+			const struct nfs_client *clp,
+			const char *addr,
+			int error
+		),
+
+		TP_ARGS(clp, addr, error),
+
+		TP_STRUCT__entry(
+			__string(main_addr, clp->cl_hostname)
+			__string(trunk_addr, addr)
+			__field(unsigned long, error)
+		),
+
+		TP_fast_assign(
+			__entry->error = error < 0 ? -error : 0;
+			__assign_str(main_addr, clp->cl_hostname);
+			__assign_str(trunk_addr, addr);
+		),
+
+		TP_printk(
+			"error=%ld (%s) main_addr=%s trunk_addr=%s",
+			-__entry->error,
+			show_nfs4_status(__entry->error),
+			__get_str(main_addr),
+			__get_str(trunk_addr)
+		)
+);
+
 TRACE_EVENT(nfs4_sequence_done,
 		TP_PROTO(
 			const struct nfs4_session *session,

include/trace/misc/nfs.h

···
 		{ EHOSTDOWN,			"EHOSTDOWN" }, \
 		{ EPIPE,			"EPIPE" }, \
 		{ EPFNOSUPPORT,			"EPFNOSUPPORT" }, \
+		{ EINVAL,			"EINVAL" }, \
 		{ EPROTONOSUPPORT,		"EPROTONOSUPPORT" }, \
 		{ NFS4ERR_ACCESS,		"ACCESS" }, \
 		{ NFS4ERR_ATTRNOTSUPP,		"ATTRNOTSUPP" }, \