mptcp: add tracepoint in mptcp_subflow_get_send

This patch added a tracepoint in the packet scheduler function
mptcp_subflow_get_send().

Suggested-by: Paolo Abeni <pabeni@redhat.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Geliang Tang <geliangtang@gmail.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

MAINTAINERS

@@ -12546,6 +12546,7 @@ W:	https://github.com/multipath-tcp/mptcp_net-next/wiki
 B:	https://github.com/multipath-tcp/mptcp_net-next/issues
 F:	Documentation/networking/mptcp-sysctl.rst
 F:	include/net/mptcp.h
+F:	include/trace/events/mptcp.h
 F:	include/uapi/linux/mptcp.h
 F:	net/mptcp/
 F:	tools/testing/selftests/net/mptcp/

include/trace/events/mptcp.h

@@ -0,0 +1,60 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM mptcp
+
+#if !defined(_TRACE_MPTCP_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_MPTCP_H
+
+#include <linux/tracepoint.h>
+
+TRACE_EVENT(mptcp_subflow_get_send,
+
+	TP_PROTO(struct mptcp_subflow_context *subflow),
+
+	TP_ARGS(subflow),
+
+	TP_STRUCT__entry(
+		__field(bool, active)
+		__field(bool, free)
+		__field(u32, snd_wnd)
+		__field(u32, pace)
+		__field(u8, backup)
+		__field(u64, ratio)
+	),
+
+	TP_fast_assign(
+		struct sock *ssk;
+
+		__entry->active = mptcp_subflow_active(subflow);
+		__entry->backup = subflow->backup;
+
+		if (subflow->tcp_sock && sk_fullsock(subflow->tcp_sock))
+			__entry->free = sk_stream_memory_free(subflow->tcp_sock);
+		else
+			__entry->free = 0;
+
+		ssk = mptcp_subflow_tcp_sock(subflow);
+		if (ssk && sk_fullsock(ssk)) {
+			__entry->snd_wnd = tcp_sk(ssk)->snd_wnd;
+			__entry->pace = ssk->sk_pacing_rate;
+		} else {
+			__entry->snd_wnd = 0;
+			__entry->pace = 0;
+		}
+
+		if (ssk && sk_fullsock(ssk) && __entry->pace)
+			__entry->ratio = div_u64((u64)ssk->sk_wmem_queued << 32, __entry->pace);
+		else
+			__entry->ratio = 0;
+	),
+
+	TP_printk("active=%d free=%d snd_wnd=%u pace=%u backup=%u ratio=%llu",
+		  __entry->active, __entry->free,
+		  __entry->snd_wnd, __entry->pace,
+		  __entry->backup, __entry->ratio)
+);
+
+#endif /* _TRACE_MPTCP_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>

net/mptcp/protocol.c

@@ -25,6 +25,9 @@
 #include "protocol.h"
 #include "mib.h"
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/mptcp.h>
+
 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 struct mptcp6_sock {
 	struct mptcp_sock msk;
@@ -1410,6 +1413,7 @@ static struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk)
 		send_info[i].ratio = -1;
 	}
 	mptcp_for_each_subflow(msk, subflow) {
+		trace_mptcp_subflow_get_send(subflow);
 		ssk =  mptcp_subflow_tcp_sock(subflow);
 		if (!mptcp_subflow_active(subflow))
 			continue;
@@ -1430,10 +1434,6 @@ static struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk)
 		}
 	}
 
-	pr_debug("msk=%p nr_active=%d ssk=%p:%lld backup=%p:%lld",
-		 msk, nr_active, send_info[0].ssk, send_info[0].ratio,
-		 send_info[1].ssk, send_info[1].ratio);
-
 	/* pick the best backup if no other subflow is active */
 	if (!nr_active)
 		send_info[0].ssk = send_info[1].ssk;