block/rnbd-srv: Add event tracing support

Add event tracing mechanism for following routines:
- create_sess()
- destroy_sess()
- process_rdma()
- process_msg_sess_info()
- process_msg_open()
- process_msg_close()

How to use:
1. Load the rnbd_server module
2. cd /sys/kernel/debug/tracing
3. If all the events need to be enabled:
echo 1 > events/rnbd_srv/enable
4. OR only speific routine/event needs to be enabled e.g.
echo 1 > events/rnbd_srv/create_sess/enable
5. cat trace
5. Run some workload which can trigger create_sess() routine/event

Signed-off-by: Santosh Pradhan <[e-mail]>
Signed-off-by: Jack Wang <[e-mail]>
Signed-off-by: Md Haris Iqbal <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jens Axboe <[e-mail]>

drivers/block/rnbd/Makefile

···
 		  rnbd-clt-sysfs.o \
 		  rnbd-common.o
 
+CFLAGS_rnbd-srv-trace.o = -I$(src)
+
 rnbd-server-y := rnbd-common.o \
 		  rnbd-srv.o \
 		  rnbd-srv-dev.o \
-		  rnbd-srv-sysfs.o
+		  rnbd-srv-sysfs.o \
+		  rnbd-srv-trace.o
 
 obj-$(CONFIG_BLK_DEV_RNBD_CLIENT) += rnbd-client.o
 obj-$(CONFIG_BLK_DEV_RNBD_SERVER) += rnbd-server.o

drivers/block/rnbd/rnbd-srv-trace.c

···
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * RDMA Network Block Driver
+ *
+ * Copyright (c) 2022 1&1 IONOS SE. All rights reserved.
+ */
+#include "rtrs.h"
+#include "rtrs-srv.h"
+#include "rnbd-srv.h"
+#include "rnbd-proto.h"
+
+/*
+ * We include this last to have the helpers above available for the trace
+ * event implementations.
+ */
+#define CREATE_TRACE_POINTS
+#include "rnbd-srv-trace.h"

drivers/block/rnbd/rnbd-srv-trace.h

···
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * RDMA Network Block Driver
+ *
+ * Copyright (c) 2022 1&1 IONOS SE. All rights reserved.
+ */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM rnbd_srv
+
+#if !defined(_TRACE_RNBD_SRV_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_RNBD_SRV_H
+
+#include <linux/tracepoint.h>
+
+struct rnbd_srv_session;
+struct rtrs_srv_op;
+
+DECLARE_EVENT_CLASS(rnbd_srv_link_class,
+	TP_PROTO(struct rnbd_srv_session *srv),
+
+	TP_ARGS(srv),
+
+	TP_STRUCT__entry(
+		__field(int, qdepth)
+		__string(sessname, srv->sessname)
+	),
+
+	TP_fast_assign(
+		__entry->qdepth = srv->queue_depth;
+		__assign_str(sessname, srv->sessname);
+	),
+
+	TP_printk("sessname: %s qdepth: %d",
+		   __get_str(sessname),
+		   __entry->qdepth
+	)
+);
+
+#define DEFINE_LINK_EVENT(name) \
+DEFINE_EVENT(rnbd_srv_link_class, name, \
+	TP_PROTO(struct rnbd_srv_session *srv), \
+	TP_ARGS(srv))
+
+DEFINE_LINK_EVENT(create_sess);
+DEFINE_LINK_EVENT(destroy_sess);
+
+TRACE_DEFINE_ENUM(RNBD_OP_READ);
+TRACE_DEFINE_ENUM(RNBD_OP_WRITE);
+TRACE_DEFINE_ENUM(RNBD_OP_FLUSH);
+TRACE_DEFINE_ENUM(RNBD_OP_DISCARD);
+TRACE_DEFINE_ENUM(RNBD_OP_SECURE_ERASE);
+TRACE_DEFINE_ENUM(RNBD_F_SYNC);
+TRACE_DEFINE_ENUM(RNBD_F_FUA);
+
+#define show_rnbd_rw_flags(x) \
+	__print_flags(x, "|", \
+		{ RNBD_OP_READ,		"READ" }, \
+		{ RNBD_OP_WRITE,	"WRITE" }, \
+		{ RNBD_OP_FLUSH,	"FLUSH" }, \
+		{ RNBD_OP_DISCARD,	"DISCARD" }, \
+		{ RNBD_OP_SECURE_ERASE,	"SECURE_ERASE" }, \
+		{ RNBD_F_SYNC,		"SYNC" }, \
+		{ RNBD_F_FUA,		"FUA" })
+
+TRACE_EVENT(process_rdma,
+	TP_PROTO(struct rnbd_srv_session *srv,
+		 const struct rnbd_msg_io *msg,
+		 struct rtrs_srv_op *id,
+		 u32 datalen,
+		 size_t usrlen),
+
+	TP_ARGS(srv, msg, id, datalen, usrlen),
+
+	TP_STRUCT__entry(
+		__string(sessname, srv->sessname)
+		__field(u8, dir)
+		__field(u8, ver)
+		__field(u32, device_id)
+		__field(u64, sector)
+		__field(u32, flags)
+		__field(u32, bi_size)
+		__field(u16, ioprio)
+		__field(u32, datalen)
+		__field(size_t, usrlen)
+	),
+
+	TP_fast_assign(
+		__assign_str(sessname, srv->sessname);
+		__entry->dir = id->dir;
+		__entry->ver = srv->ver;
+		__entry->device_id = le32_to_cpu(msg->device_id);
+		__entry->sector = le64_to_cpu(msg->sector);
+		__entry->bi_size = le32_to_cpu(msg->bi_size);
+		__entry->flags = le32_to_cpu(msg->rw);
+		__entry->ioprio = le16_to_cpu(msg->prio);
+		__entry->datalen = datalen;
+		__entry->usrlen = usrlen;
+	),
+
+	TP_printk("I/O req: sess: %s, type: %s, ver: %d, devid: %u, sector: %llu, bsize: %u, flags: %s, ioprio: %d, datalen: %u, usrlen: %zu",
+		   __get_str(sessname),
+		   __print_symbolic(__entry->dir,
+			 { READ,  "READ" },
+			 { WRITE, "WRITE" }),
+		   __entry->ver,
+		   __entry->device_id,
+		   __entry->sector,
+		   __entry->bi_size,
+		   show_rnbd_rw_flags(__entry->flags),
+		   __entry->ioprio,
+		   __entry->datalen,
+		   __entry->usrlen
+	)
+);
+
+TRACE_EVENT(process_msg_sess_info,
+	TP_PROTO(struct rnbd_srv_session *srv,
+		 const struct rnbd_msg_sess_info *msg),
+
+	TP_ARGS(srv, msg),
+
+	TP_STRUCT__entry(
+		__field(u8, proto_ver)
+		__field(u8, clt_ver)
+		__field(u8, srv_ver)
+		__string(sessname, srv->sessname)
+	),
+
+	TP_fast_assign(
+		__entry->proto_ver = srv->ver;
+		__entry->clt_ver = msg->ver;
+		__entry->srv_ver = RNBD_PROTO_VER_MAJOR;
+		__assign_str(sessname, srv->sessname);
+	),
+
+	TP_printk("Session %s using proto-ver %d (clt-ver: %d, srv-ver: %d)",
+		   __get_str(sessname),
+		   __entry->proto_ver,
+		   __entry->clt_ver,
+		   __entry->srv_ver
+	)
+);
+
+TRACE_DEFINE_ENUM(RNBD_ACCESS_RO);
+TRACE_DEFINE_ENUM(RNBD_ACCESS_RW);
+TRACE_DEFINE_ENUM(RNBD_ACCESS_MIGRATION);
+
+#define show_rnbd_access_mode(x) \
+	__print_symbolic(x, \
+		{ RNBD_ACCESS_RO,		"RO" }, \
+		{ RNBD_ACCESS_RW,		"RW" }, \
+		{ RNBD_ACCESS_MIGRATION,	"MIGRATION" })
+
+TRACE_EVENT(process_msg_open,
+	TP_PROTO(struct rnbd_srv_session *srv,
+		 const struct rnbd_msg_open *msg),
+
+	TP_ARGS(srv, msg),
+
+	TP_STRUCT__entry(
+		__field(u8, access_mode)
+		__string(sessname, srv->sessname)
+		__string(dev_name, msg->dev_name)
+	),
+
+	TP_fast_assign(
+		__entry->access_mode = msg->access_mode;
+		__assign_str(sessname, srv->sessname);
+		__assign_str(dev_name, msg->dev_name);
+	),
+
+	TP_printk("Open message received: session='%s' path='%s' access_mode=%s",
+		   __get_str(sessname),
+		   __get_str(dev_name),
+		   show_rnbd_access_mode(__entry->access_mode)
+	)
+);
+
+TRACE_EVENT(process_msg_close,
+	TP_PROTO(struct rnbd_srv_session *srv,
+		 const struct rnbd_msg_close *msg),
+
+	TP_ARGS(srv, msg),
+
+	TP_STRUCT__entry(
+		__field(u32, device_id)
+		__string(sessname, srv->sessname)
+	),
+
+	TP_fast_assign(
+		__entry->device_id = le32_to_cpu(msg->device_id);
+		__assign_str(sessname, srv->sessname);
+	),
+
+	TP_printk("Close message received: session='%s' device id='%d'",
+		   __get_str(sessname),
+		   __entry->device_id
+	)
+);
+
+#endif /* _TRACE_RNBD_SRV_H */
+
+#undef TRACE_INCLUDE_PATH
+#define TRACE_INCLUDE_PATH .
+#define TRACE_INCLUDE_FILE rnbd-srv-trace
+#include <trace/define_trace.h>
+

drivers/block/rnbd/rnbd-srv.c

···
 
 #include "rnbd-srv.h"
 #include "rnbd-srv-dev.h"
+#include "rnbd-srv-trace.h"
 
 MODULE_DESCRIPTION("RDMA Network Block Device Server");
 MODULE_LICENSE("GPL");
···
 	struct bio *bio;
 	short prio;
 
+	trace_process_rdma(srv_sess, msg, id, datalen, usrlen);
+
 	priv = kmalloc(sizeof(*priv), GFP_KERNEL);
 	if (!priv)
 		return -ENOMEM;
···
 	if (xa_empty(&srv_sess->index_idr))
 		goto out;
 
+	trace_destroy_sess(srv_sess);
+
 	mutex_lock(&srv_sess->lock);
 	xa_for_each(&srv_sess->index_idr, index, sess_dev)
 		rnbd_srv_destroy_dev_session_sysfs(sess_dev);
···
 	strscpy(srv_sess->sessname, pathname, sizeof(srv_sess->sessname));
 
 	rtrs_srv_set_sess_priv(rtrs, srv_sess);
+
+	trace_create_sess(srv_sess);
 
 	return 0;
 }
···
 {
 	const struct rnbd_msg_close *close_msg = usr;
 	struct rnbd_srv_sess_dev *sess_dev;
+
+	trace_process_msg_close(srv_sess, close_msg);
 
 	sess_dev = rnbd_get_sess_dev(le32_to_cpu(close_msg->device_id),
 				      srv_sess);
···
 	struct rnbd_msg_sess_info_rsp *rsp = data;
 
 	srv_sess->ver = min_t(u8, sess_info_msg->ver, RNBD_PROTO_VER_MAJOR);
-	pr_debug("Session %s using protocol version %d (client version: %d, server version: %d)\n",
-		 srv_sess->sessname, srv_sess->ver,
-		 sess_info_msg->ver, RNBD_PROTO_VER_MAJOR);
+
+	trace_process_msg_sess_info(srv_sess, sess_info_msg);
 
 	rsp->hdr.type = cpu_to_le16(RNBD_MSG_SESS_INFO_RSP);
 	rsp->ver = srv_sess->ver;
···
 	struct rnbd_dev *rnbd_dev;
 	struct rnbd_msg_open_rsp *rsp = data;
 
-	pr_debug("Open message received: session='%s' path='%s' access_mode=%d\n",
-		 srv_sess->sessname, open_msg->dev_name,
-		 open_msg->access_mode);
+	trace_process_msg_open(srv_sess, open_msg);
+
 	open_flags = FMODE_READ;
 	if (open_msg->access_mode != RNBD_ACCESS_RO)
 		open_flags |= FMODE_WRITE;