[PATCH net-next 1/3] net/smc: Introduce tracepoint for fallback

Tony Lu
2021-11-01T07:40:48Z

This introduces tracepoint for smc fallback to TCP, so that we can track
which connection and why it fallbacks, and map the clcsocks' pointer with
/proc/net/tcp to find more details about TCP connections. Compared with
kprobe or other dynamic tracing, tracepoints are stable and easy to use.

Signed-off-by: Tony Lu <tonylu@linux.alibaba.com>
Reviewed-by: Wen Gu <guwen@linux.alibaba.com>
---
net/smc/Makefile | 2 ++
net/smc/af_smc.c | 2 ++
net/smc/smc_tracepoint.c | 6 +++++
net/smc/smc_tracepoint.h | 49 ++++++++++++++++++++++++++++++++++++++++
4 files changed, 59 insertions(+)
create mode 100644 net/smc/smc_tracepoint.c
create mode 100644 net/smc/smc_tracepoint.h

diff --git a/net/smc/Makefile b/net/smc/Makefile
index 99a0186cba5b..196fb6f01b14 100644
--- a/net/smc/Makefile
+++ b/net/smc/Makefile
@@ -1,5 +1,7 @@
# SPDX-License-Identifier: GPL-2.0-only
+ccflags-y += -I$(src)
obj-$(CONFIG_SMC) += smc.o
obj-$(CONFIG_SMC_DIAG) += smc_diag.o
smc-y := af_smc.o smc_pnet.o smc_ib.o smc_clc.o smc_core.o smc_wr.o smc_llc.o
smc-y += smc_cdc.o smc_tx.o smc_rx.o smc_close.o smc_ism.o smc_netlink.o smc_stats.o
+smc-y += smc_tracepoint.o
diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 8dc34388b2c1..0cf7ed2f5d41 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -50,6 +50,7 @@
#include "smc_rx.h"
#include "smc_close.h"
#include "smc_stats.h"
+#include "smc_tracepoint.h"

static DEFINE_MUTEX(smc_server_lgr_pending); /* serialize link group
* creation on server
@@ -564,6 +565,7 @@ static void smc_switch_to_fallback(struct smc_sock *smc, int reason_code)
smc->use_fallback = true;
smc->fallback_rsn = reason_code;
smc_stat_fallback(smc);
+ trace_smc_switch_to_fallback(smc, reason_code);
if (smc->sk.sk_socket && smc->sk.sk_socket->file) {
smc->clcsock->file = smc->sk.sk_socket->file;
smc->clcsock->file->private_data = smc->clcsock;
diff --git a/net/smc/smc_tracepoint.c b/net/smc/smc_tracepoint.c
new file mode 100644
index 000000000000..861a41644971
--- /dev/null
+++ b/net/smc/smc_tracepoint.c
@@ -0,0 +1,6 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#define CREATE_TRACE_POINTS
+#include "smc_tracepoint.h"
+
+EXPORT_TRACEPOINT_SYMBOL(smc_switch_to_fallback);
diff --git a/net/smc/smc_tracepoint.h b/net/smc/smc_tracepoint.h
new file mode 100644
index 000000000000..3bc97f5f2134
--- /dev/null
+++ b/net/smc/smc_tracepoint.h
@@ -0,0 +1,49 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM smc
+
+#if !defined(_TRACE_SMC_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_SMC_H
+
+#include <linux/ipv6.h>
+#include <linux/tcp.h>
+#include <linux/tracepoint.h>
+#include <net/ipv6.h>
+#include "smc.h"
+#include "smc_core.h"
+
+TRACE_EVENT(smc_switch_to_fallback,
+
+ TP_PROTO(const struct smc_sock *smc, int fallback_rsn),
+
+ TP_ARGS(smc, fallback_rsn),
+
+ TP_STRUCT__entry(
+ __field(const void *, sk)
+ __field(const void *, clcsk)
+ __field(int, fallback_rsn)
+ ),
+
+ TP_fast_assign(
+ const struct sock *sk = &smc->sk;
+ const struct sock *clcsk = smc->clcsock->sk;
+
+ __entry->sk = sk;
+ __entry->clcsk = clcsk;
+ __entry->fallback_rsn = fallback_rsn;
+ ),
+
+ TP_printk("sk=%p clcsk=%p fallback_rsn=%d",
+ __entry->sk, __entry->clcsk, __entry->fallback_rsn)
+);
+
+#endif /* _TRACE_SMC_H */
+
+#undef TRACE_INCLUDE_PATH
+#define TRACE_INCLUDE_PATH .
+
+#undef TRACE_INCLUDE_FILE
+#define TRACE_INCLUDE_FILE smc_tracepoint
+
+#include <trace/define_trace.h>
--
2.19.1.6.gb485710b