Date:   Wed, 15 Feb 2023 15:33:45 -0700
From:   Ross Zwisler <zwisler@...omium.org>
To:     linux-kernel@...r.kernel.org
Cc:     Ross Zwisler <zwisler@...gle.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        linux-trace-kernel@...r.kernel.org
Subject: [PATCH v2 1/6] tracing: always use canonical ftrace path

The canonical location for the tracefs filesystem is at /sys/kernel/tracing.

But, from Documentation/trace/ftrace.rst:

  Before 4.1, all ftrace tracing control files were within the debugfs
  file system, which is typically located at /sys/kernel/debug/tracing.
  For backward compatibility, when mounting the debugfs file system,
  the tracefs file system will be automatically mounted at:

  /sys/kernel/debug/tracing

Many comments and Kconfig help messages in the tracing code still refer
to this older debugfs path, so let's update them to avoid confusion.

Signed-off-by: Ross Zwisler <zwisler@...gle.com>
---
 include/linux/kernel.h                    |  2 +-
 include/linux/tracepoint.h                |  4 ++--
 kernel/trace/Kconfig                      | 20 ++++++++++----------
 kernel/trace/kprobe_event_gen_test.c      |  2 +-
 kernel/trace/ring_buffer.c                |  2 +-
 kernel/trace/synth_event_gen_test.c       |  2 +-
 kernel/trace/trace.c                      |  2 +-
 samples/user_events/example.c             |  4 ++--
 scripts/tracing/draw_functrace.py         |  6 +++---
 tools/lib/api/fs/tracing_path.c           |  4 ++--
 tools/tracing/latency/latency-collector.c |  2 +-
 11 files changed, 25 insertions(+), 25 deletions(-)

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index fe6efb24d151..40bce7495af8 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -297,7 +297,7 @@ bool mac_pton(const char *s, u8 *mac);
  *
  * Use tracing_on/tracing_off when you want to quickly turn on or off
  * tracing. It simply enables or disables the recording of the trace events.
- * This also corresponds to the user space /sys/kernel/debug/tracing/tracing_on
+ * This also corresponds to the user space /sys/kernel/tracing/tracing_on
  * file, which gives a means for the kernel and userspace to interact.
  * Place a tracing_off() in the kernel where you want tracing to end.
  * From user space, examine the trace, and then echo 1 > tracing_on
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 4b33b95eb8be..fa1004fcf810 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -471,7 +471,7 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
  *	* This is how the trace record is structured and will
  *	* be saved into the ring buffer. These are the fields
  *	* that will be exposed to user-space in
- *	* /sys/kernel/debug/tracing/events/<*>/format.
+ *	* /sys/kernel/tracing/events/<*>/format.
  *	*
  *	* The declared 'local variable' is called '__entry'
  *	*
@@ -531,7 +531,7 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
  * tracepoint callback (this is used by programmatic plugins and
  * can also by used by generic instrumentation like SystemTap), and
  * it is also used to expose a structured trace record in
- * /sys/kernel/debug/tracing/events/.
+ * /sys/kernel/tracing/events/.
  *
  * A set of (un)registration functions can be passed to the variant
  * TRACE_EVENT_FN to perform any (un)registration work.
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index d7043043f59c..5f5e64f9e715 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -239,7 +239,7 @@ config DYNAMIC_FTRACE
 	  enabled, and the functions not enabled will not affect
 	  performance of the system.
 
-	  See the files in /sys/kernel/debug/tracing:
+	  See the files in /sys/kernel/tracing:
 	    available_filter_functions
 	    set_ftrace_filter
 	    set_ftrace_notrace
@@ -299,7 +299,7 @@ config STACK_TRACER
 	select KALLSYMS
 	help
 	  This special tracer records the maximum stack footprint of the
-	  kernel and displays it in /sys/kernel/debug/tracing/stack_trace.
+	  kernel and displays it in /sys/kernel/tracing/stack_trace.
 
 	  This tracer works by hooking into every function call that the
 	  kernel executes, and keeping a maximum stack depth value and
@@ -339,7 +339,7 @@ config IRQSOFF_TRACER
 	  disabled by default and can be runtime (re-)started
 	  via:
 
-	      echo 0 > /sys/kernel/debug/tracing/tracing_max_latency
+	      echo 0 > /sys/kernel/tracing/tracing_max_latency
 
 	  (Note that kernel size and overhead increase with this option
 	  enabled. This option and the preempt-off timing option can be
@@ -363,7 +363,7 @@ config PREEMPT_TRACER
 	  disabled by default and can be runtime (re-)started
 	  via:
 
-	      echo 0 > /sys/kernel/debug/tracing/tracing_max_latency
+	      echo 0 > /sys/kernel/tracing/tracing_max_latency
 
 	  (Note that kernel size and overhead increase with this option
 	  enabled. This option and the irqs-off timing option can be
@@ -515,7 +515,7 @@ config TRACER_SNAPSHOT
 	  Allow tracing users to take snapshot of the current buffer using the
 	  ftrace interface, e.g.:
 
-	      echo 1 > /sys/kernel/debug/tracing/snapshot
+	      echo 1 > /sys/kernel/tracing/snapshot
 	      cat snapshot
 
 config TRACER_SNAPSHOT_PER_CPU_SWAP
@@ -527,7 +527,7 @@ config TRACER_SNAPSHOT_PER_CPU_SWAP
 	  full swap (all buffers). If this is set, then the following is
 	  allowed:
 
-	      echo 1 > /sys/kernel/debug/tracing/per_cpu/cpu2/snapshot
+	      echo 1 > /sys/kernel/tracing/per_cpu/cpu2/snapshot
 
 	  After which, only the tracing buffer for CPU 2 was swapped with
 	  the main tracing buffer, and the other CPU buffers remain the same.
@@ -574,7 +574,7 @@ config PROFILE_ANNOTATED_BRANCHES
 	  This tracer profiles all likely and unlikely macros
 	  in the kernel. It will display the results in:
 
-	  /sys/kernel/debug/tracing/trace_stat/branch_annotated
+	  /sys/kernel/tracing/trace_stat/branch_annotated
 
 	  Note: this will add a significant overhead; only turn this
 	  on if you need to profile the system's use of these macros.
@@ -587,7 +587,7 @@ config PROFILE_ALL_BRANCHES
 	  taken in the kernel is recorded whether it hit or miss.
 	  The results will be displayed in:
 
-	  /sys/kernel/debug/tracing/trace_stat/branch_all
+	  /sys/kernel/tracing/trace_stat/branch_all
 
 	  This option also enables the likely/unlikely profiler.
 
@@ -638,8 +638,8 @@ config BLK_DEV_IO_TRACE
 	  Tracing also is possible using the ftrace interface, e.g.:
 
 	    echo 1 > /sys/block/sda/sda1/trace/enable
-	    echo blk > /sys/kernel/debug/tracing/current_tracer
-	    cat /sys/kernel/debug/tracing/trace_pipe
+	    echo blk > /sys/kernel/tracing/current_tracer
+	    cat /sys/kernel/tracing/trace_pipe
 
 	  If unsure, say N.
 
diff --git a/kernel/trace/kprobe_event_gen_test.c b/kernel/trace/kprobe_event_gen_test.c
index c736487fc0e4..4850fdfe27f1 100644
--- a/kernel/trace/kprobe_event_gen_test.c
+++ b/kernel/trace/kprobe_event_gen_test.c
@@ -21,7 +21,7 @@
  * Then:
  *
  * # insmod kernel/trace/kprobe_event_gen_test.ko
- * # cat /sys/kernel/debug/tracing/trace
+ * # cat /sys/kernel/tracing/trace
  *
  * You should see many instances of the "gen_kprobe_test" and
  * "gen_kretprobe_test" events in the trace buffer.
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index c366a0a9ddba..4cdb2feccff3 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -2886,7 +2886,7 @@ rb_check_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
 		  sched_clock_stable() ? "" :
 		  "If you just came from a suspend/resume,\n"
 		  "please switch to the trace global clock:\n"
-		  "  echo global > /sys/kernel/debug/tracing/trace_clock\n"
+		  "  echo global > /sys/kernel/tracing/trace_clock\n"
 		  "or add trace_clock=global to the kernel command line\n");
 }
 
diff --git a/kernel/trace/synth_event_gen_test.c b/kernel/trace/synth_event_gen_test.c
index 8d77526892f4..8dfe85499d4a 100644
--- a/kernel/trace/synth_event_gen_test.c
+++ b/kernel/trace/synth_event_gen_test.c
@@ -22,7 +22,7 @@
  * Then:
  *
  * # insmod kernel/trace/synth_event_gen_test.ko
- * # cat /sys/kernel/debug/tracing/trace
+ * # cat /sys/kernel/tracing/trace
  *
  * You should see several events in the trace buffer -
  * "create_synth_test", "empty_synth_test", and several instances of
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index c9e40f692650..1101220052b3 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1142,7 +1142,7 @@ void tracing_snapshot_instance(struct trace_array *tr)
  *
  * Note, make sure to allocate the snapshot with either
  * a tracing_snapshot_alloc(), or by doing it manually
- * with: echo 1 > /sys/kernel/debug/tracing/snapshot
+ * with: echo 1 > /sys/kernel/tracing/snapshot
  *
  * If the snapshot buffer is not allocated, it will stop tracing.
  * Basically making a permanent snapshot.
diff --git a/samples/user_events/example.c b/samples/user_events/example.c
index d06dc24156ec..18e34c9d708e 100644
--- a/samples/user_events/example.c
+++ b/samples/user_events/example.c
@@ -23,8 +23,8 @@
 #endif
 
 /* Assumes debugfs is mounted */
-const char *data_file = "/sys/kernel/debug/tracing/user_events_data";
-const char *status_file = "/sys/kernel/debug/tracing/user_events_status";
+const char *data_file = "/sys/kernel/tracing/user_events_data";
+const char *status_file = "/sys/kernel/tracing/user_events_status";
 
 static int event_status(long **status)
 {
diff --git a/scripts/tracing/draw_functrace.py b/scripts/tracing/draw_functrace.py
index 438516bdfb3c..42fa87300941 100755
--- a/scripts/tracing/draw_functrace.py
+++ b/scripts/tracing/draw_functrace.py
@@ -12,9 +12,9 @@ calls. Only the functions's names and the call time are provided.
 
 Usage:
 	Be sure that you have CONFIG_FUNCTION_TRACER
-	# mount -t debugfs nodev /sys/kernel/debug
-	# echo function > /sys/kernel/debug/tracing/current_tracer
-	$ cat /sys/kernel/debug/tracing/trace_pipe > ~/raw_trace_func
+	# mount -t tracefs nodev /sys/kernel/tracing
+	# echo function > /sys/kernel/tracing/current_tracer
+	$ cat /sys/kernel/tracing/trace_pipe > ~/raw_trace_func
 	Wait some times but not too much, the script is a bit slow.
 	Break the pipe (Ctrl + Z)
 	$ scripts/tracing/draw_functrace.py < ~/raw_trace_func > draw_functrace
diff --git a/tools/lib/api/fs/tracing_path.c b/tools/lib/api/fs/tracing_path.c
index b8e457c841ab..7ba3e81274e8 100644
--- a/tools/lib/api/fs/tracing_path.c
+++ b/tools/lib/api/fs/tracing_path.c
@@ -14,8 +14,8 @@
 #include "tracing_path.h"
 
 static char tracing_mnt[PATH_MAX]  = "/sys/kernel/debug";
-static char tracing_path[PATH_MAX]        = "/sys/kernel/debug/tracing";
-static char tracing_events_path[PATH_MAX] = "/sys/kernel/debug/tracing/events";
+static char tracing_path[PATH_MAX]        = "/sys/kernel/tracing";
+static char tracing_events_path[PATH_MAX] = "/sys/kernel/tracing/events";
 
 static void __tracing_path_set(const char *tracing, const char *mountpoint)
 {
diff --git a/tools/tracing/latency/latency-collector.c b/tools/tracing/latency/latency-collector.c
index 59a7f2346eab..0fd9c747d396 100644
--- a/tools/tracing/latency/latency-collector.c
+++ b/tools/tracing/latency/latency-collector.c
@@ -1584,7 +1584,7 @@ static void *do_printloop(void *arg)
 		/*
 		 * Toss a coin to decide if we want to sleep before printing
 		 * out the backtrace. The reason for this is that opening
-		 * /sys/kernel/debug/tracing/trace will cause a blackout of
+		 * /sys/kernel/tracing/trace will cause a blackout of
 		 * hundreds of ms, where no latencies will be noted by the
 		 * latency tracer. Thus by randomly sleeping we try to avoid
 		 * missing traces systematically due to this. With this option
-- 
2.39.1.637.g21b0678d19-goog

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