tracing/eprobe: Iterate trace_eprobe directly

Refer to the description in [1], we can skip "container_of()" following
"list_for_each_entry()" by using "list_for_each_entry()" with
"struct trace_eprobe" and "tp.list".

Also, this patch defines "for_each_trace_eprobe_tp" to simplify the code
of the same logic.

[1] https://lore.kernel.org/all/CAHk-=wjakjw6-rDzDDBsuMoDCqd+9ogifR_EE1F0K-jYek1CdA@mail.gmail.com/

Link: https://lore.kernel.org/all/20230822022433.262478-1-nashuiliang@gmail.com/Signed-off-by: Chuang Wang <nashuiliang@gmail.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

kernel/trace/trace_eprobe.c

@@ -41,6 +41,10 @@ struct eprobe_data {
 	struct trace_eprobe	*ep;
 };
 
+
+#define for_each_trace_eprobe_tp(ep, _tp) \
+	list_for_each_entry(ep, trace_probe_probe_list(_tp), tp.list)
+
 static int __trace_eprobe_create(int argc, const char *argv[]);
 
 static void trace_event_probe_cleanup(struct trace_eprobe *ep)
@@ -640,7 +644,7 @@ static int disable_eprobe(struct trace_eprobe *ep,
 static int enable_trace_eprobe(struct trace_event_call *call,
 			       struct trace_event_file *file)
 {
-	struct trace_probe *pos, *tp;
+	struct trace_probe *tp;
 	struct trace_eprobe *ep;
 	bool enabled;
 	int ret = 0;
@@ -662,8 +666,7 @@ static int enable_trace_eprobe(struct trace_event_call *call,
 	if (enabled)
 		return 0;
 
-	list_for_each_entry(pos, trace_probe_probe_list(tp), list) {
-		ep = container_of(pos, struct trace_eprobe, tp);
+	for_each_trace_eprobe_tp(ep, tp) {
 		ret = enable_eprobe(ep, file);
 		if (ret)
 			break;
@@ -680,8 +683,7 @@ static int enable_trace_eprobe(struct trace_event_call *call,
 			 */
 			WARN_ON_ONCE(ret != -ENOMEM);
 
-			list_for_each_entry(pos, trace_probe_probe_list(tp), list) {
-				ep = container_of(pos, struct trace_eprobe, tp);
+			for_each_trace_eprobe_tp(ep, tp) {
 				disable_eprobe(ep, file->tr);
 				if (!--cnt)
 					break;
@@ -699,7 +701,7 @@ static int enable_trace_eprobe(struct trace_event_call *call,
 static int disable_trace_eprobe(struct trace_event_call *call,
 				struct trace_event_file *file)
 {
-	struct trace_probe *pos, *tp;
+	struct trace_probe *tp;
 	struct trace_eprobe *ep;
 
 	tp = trace_probe_primary_from_call(call);
@@ -716,10 +718,8 @@ static int disable_trace_eprobe(struct trace_event_call *call,
 		trace_probe_clear_flag(tp, TP_FLAG_PROFILE);
 
 	if (!trace_probe_is_enabled(tp)) {
-		list_for_each_entry(pos, trace_probe_probe_list(tp), list) {
-			ep = container_of(pos, struct trace_eprobe, tp);
+		for_each_trace_eprobe_tp(ep, tp)
 			disable_eprobe(ep, file->tr);
-		}
 	}
 
  out: