[Cluster-devel] [PATCH dlm/next 1/2] fs: dlm: initial support for tracepoints

[Alexander Aring <aahringo@redhat.com>]

This patch adds initial support for dlm tracepoints. It will introduce
tracepoints to dlm main functionality dlm_lock() and their complete
ast() callback or blocking bast() callback.

The lock functionality has a start and end functionality, this is
because there exists a race in case if would have a tracepoint at the
end position only the complete/blocking callbacks could occur before. To
work with eBPF tracing and using their lookup hash functionality there
could be problems. However use the start functionality and for hash
insert and check again in end functionality if there was an dlm internal
error. In further it might also that locks with local masters will
occur those callbacks immediately so we must have such functionality.

I did not make everything accessible yet, although it seems eBPF can be
used to access a lot of internal datastructures if it's aware of the
struct definitions of the running kernel instance. We still can change
it, if you do eBPF experiments e.g. time measurements between lock and
callback functionality you can simple use the local lkb_id field as hash
value in combination with the lockspace id if you have multiple
lockspaces. Otherwise you can simple use trace-cmd for some functionality,
e.g. `trace-cmd record -e dlm` and `trace-cmd report` afterwards.

Signed-off-by: Alexander Aring <aahringo@redhat.com>
---
 fs/dlm/ast.c               |   4 +
 fs/dlm/lock.c              |   7 ++
 fs/dlm/main.c              |   3 +
 include/trace/events/dlm.h | 159 +++++++++++++++++++++++++++++++++++++
 4 files changed, 173 insertions(+)
 create mode 100644 include/trace/events/dlm.h

diff --git a/fs/dlm/ast.c b/fs/dlm/ast.c
index 283c7b94edda..0e7c6f6819ac 100644
--- a/fs/dlm/ast.c
+++ b/fs/dlm/ast.c
@@ -9,6 +9,8 @@
 *******************************************************************************
 ******************************************************************************/
 
+#include <trace/events/dlm.h>
+
 #include "dlm_internal.h"
 #include "lock.h"
 #include "user.h"
@@ -254,10 +256,12 @@ void dlm_callback_work(struct work_struct *work)
 			continue;
 		} else if (callbacks[i].flags & DLM_CB_BAST) {
 			bastfn(lkb->lkb_astparam, callbacks[i].mode);
+			trace_dlm_bast(ls, lkb, callbacks[i].mode);
 		} else if (callbacks[i].flags & DLM_CB_CAST) {
 			lkb->lkb_lksb->sb_status = callbacks[i].sb_status;
 			lkb->lkb_lksb->sb_flags = callbacks[i].sb_flags;
 			castfn(lkb->lkb_astparam);
+			trace_dlm_ast(ls, lkb, lkb->lkb_lksb);
 		}
 	}
 
diff --git a/fs/dlm/lock.c b/fs/dlm/lock.c
index c502c065d007..8c6a3d4e7b67 100644
--- a/fs/dlm/lock.c
+++ b/fs/dlm/lock.c
@@ -53,6 +53,8 @@
                                    R: do_xxxx()
    L: receive_xxxx_reply()     <-  R: send_xxxx_reply()
 */
+#include <trace/events/dlm.h>
+
 #include <linux/types.h>
 #include <linux/rbtree.h>
 #include <linux/slab.h>
@@ -3434,6 +3436,8 @@ int dlm_lock(dlm_lockspace_t *lockspace,
 	else
 		error = create_lkb(ls, &lkb);
 
+	trace_dlm_lock_start(ls, lkb, mode, flags);
+
 	if (error)
 		goto out;
 
@@ -3457,6 +3461,9 @@ int dlm_lock(dlm_lockspace_t *lockspace,
  out:
 	dlm_unlock_recovery(ls);
 	dlm_put_lockspace(ls);
+
+	trace_dlm_lock_end(ls, lkb, mode, flags, error);
+
 	return error;
 }
 
diff --git a/fs/dlm/main.c b/fs/dlm/main.c
index afc66a1346d3..1c5be4b70ac1 100644
--- a/fs/dlm/main.c
+++ b/fs/dlm/main.c
@@ -19,6 +19,9 @@
 #include "config.h"
 #include "lowcomms.h"
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/dlm.h>
+
 static int __init init_dlm(void)
 {
 	int error;
diff --git a/include/trace/events/dlm.h b/include/trace/events/dlm.h
new file mode 100644
index 000000000000..5887a4db3dfa
--- /dev/null
+++ b/include/trace/events/dlm.h
@@ -0,0 +1,159 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM dlm
+
+#if !defined(_TRACE_DLM_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_DLM_H
+
+#include <linux/dlm.h>
+#include <linux/dlmconstants.h>
+#include <linux/tracepoint.h>
+
+#include "../../../fs/dlm/dlm_internal.h"
+
+#define show_lock_flags(flags) __print_flags(flags, "|",	\
+	{ DLM_LKF_NOQUEUE,	"NOQUEUE" },			\
+	{ DLM_LKF_CANCEL,	"CANCEL" },			\
+	{ DLM_LKF_CONVERT,	"CONVERT" },			\
+	{ DLM_LKF_VALBLK,	"VALBLK" },			\
+	{ DLM_LKF_QUECVT,	"QUECVT" },			\
+	{ DLM_LKF_IVVALBLK,	"IVVALBLK" },			\
+	{ DLM_LKF_CONVDEADLK,	"CONVDEADLK" },			\
+	{ DLM_LKF_PERSISTENT,	"PERSISTENT" },			\
+	{ DLM_LKF_NODLCKWT,	"NODLCKWT" },			\
+	{ DLM_LKF_NODLCKBLK,	"NODLCKBLK" },			\
+	{ DLM_LKF_EXPEDITE,	"EXPEDITE" },			\
+	{ DLM_LKF_NOQUEUEBAST,	"NOQUEUEBAST" },		\
+	{ DLM_LKF_HEADQUE,	"HEADQUE" },			\
+	{ DLM_LKF_NOORDER,	"NOORDER" },			\
+	{ DLM_LKF_ORPHAN,	"ORPHAN" },			\
+	{ DLM_LKF_ALTPR,	"ALTPR" },			\
+	{ DLM_LKF_ALTCW,	"ALTCW" },			\
+	{ DLM_LKF_FORCEUNLOCK,	"FORCEUNLOCK" },		\
+	{ DLM_LKF_TIMEOUT,	"TIMEOUT" })
+
+#define show_lock_mode(mode) __print_symbolic(mode,		\
+	{ DLM_LOCK_IV,		"IV"},				\
+	{ DLM_LOCK_NL,		"NL"},				\
+	{ DLM_LOCK_CR,		"CR"},				\
+	{ DLM_LOCK_CW,		"CW"},				\
+	{ DLM_LOCK_PR,		"PR"},				\
+	{ DLM_LOCK_PW,		"PW"},				\
+	{ DLM_LOCK_EX,		"EX"})
+
+#define show_dlm_sb_flags(flags) __print_flags(flags, "|",	\
+	{ DLM_SBF_DEMOTED,	"DEMOTED" },			\
+	{ DLM_SBF_VALNOTVALID,	"VALNOTVALID" },		\
+	{ DLM_SBF_ALTMODE,	"ALTMODE" })
+
+TRACE_EVENT(dlm_lock_start,
+
+	TP_PROTO(struct dlm_ls *ls, struct dlm_lkb *lkb, int mode,
+		 uint32_t flags),
+
+	TP_ARGS(ls, lkb, mode, flags),
+
+	TP_STRUCT__entry(
+		__field(u32, ls_id)
+		__field(u32, lkb_id)
+		__field(int, mode)
+		__field(u32, flags)
+	),
+
+	TP_fast_assign(
+		__entry->ls_id = ls->ls_global_id;
+		__entry->lkb_id = lkb->lkb_id;
+		__entry->mode = mode;
+		__entry->flags = flags;
+	),
+
+	TP_printk("ls_id=%u lkb_id=%u mode=%s flags=%s",
+		  __entry->ls_id, __entry->lkb_id,
+		  show_lock_mode(__entry->mode),
+		  show_lock_flags(__entry->flags))
+
+);
+
+TRACE_EVENT(dlm_lock_end,
+
+	TP_PROTO(struct dlm_ls *ls, struct dlm_lkb *lkb, int mode,
+		 uint32_t flags, int error),
+
+	TP_ARGS(ls, lkb, mode, flags, error),
+
+	TP_STRUCT__entry(
+		__field(u32, ls_id)
+		__field(u32, lkb_id)
+		__field(int, mode)
+		__field(u32, flags)
+		__field(int, error)
+	),
+
+	TP_fast_assign(
+		__entry->ls_id = ls->ls_global_id;
+		__entry->lkb_id = lkb->lkb_id;
+		__entry->mode = mode;
+		__entry->flags = flags;
+		__entry->error = error;
+	),
+
+	TP_printk("ls_id=%u lkb_id=%u mode=%s flags=%s error=%d",
+		  __entry->ls_id, __entry->lkb_id,
+		  show_lock_mode(__entry->mode),
+		  show_lock_flags(__entry->flags), __entry->error)
+
+);
+
+TRACE_EVENT(dlm_bast,
+
+	TP_PROTO(struct dlm_ls *ls, struct dlm_lkb *lkb, int mode),
+
+	TP_ARGS(ls, lkb, mode),
+
+	TP_STRUCT__entry(
+		__field(u32, ls_id)
+		__field(u32, lkb_id)
+		__field(int, mode)
+	),
+
+	TP_fast_assign(
+		__entry->ls_id = ls->ls_global_id;
+		__entry->lkb_id = lkb->lkb_id;
+		__entry->mode = mode;
+	),
+
+	TP_printk("ls_id=%u lkb_id=%u mode=%s", __entry->ls_id,
+		  __entry->lkb_id, show_lock_mode(__entry->mode))
+
+);
+
+TRACE_EVENT(dlm_ast,
+
+	TP_PROTO(struct dlm_ls *ls, struct dlm_lkb *lkb, struct dlm_lksb *lksb),
+
+	TP_ARGS(ls, lkb, lksb),
+
+	TP_STRUCT__entry(
+		__field(u32, ls_id)
+		__field(u32, lkb_id)
+		__field(u8, sb_flags)
+		__field(int, sb_status)
+	),
+
+	TP_fast_assign(
+		__entry->ls_id = ls->ls_global_id;
+		__entry->lkb_id = lkb->lkb_id;
+		__entry->sb_flags = lksb->sb_flags;
+		__entry->sb_status = lksb->sb_status;
+	),
+
+	TP_printk("ls_id=%u lkb_id=%u sb_flags=%s sb_status=%d",
+		  __entry->ls_id, __entry->lkb_id,
+		  show_dlm_sb_flags(__entry->sb_flags), __entry->sb_status)
+
+);
+
+#endif /* if !defined(_TRACE_DLM_H) || defined(TRACE_HEADER_MULTI_READ) */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
-- 
2.27.0