tracing histograms: Simplify parse_actions() function

The parse_actions() function uses 'len = str_has_prefix()' to test which
action is in the string being parsed. But then it goes and repeats the
logic for each different action. This logic can be simplified and
duplicate code can be removed as 'len' contains the length of the found
prefix which should be used for all actions.

Link: https://lore.kernel.org/all/20240107112044.6702cb66@gandalf.local.home/
Link: https://lore.kernel.org/linux-trace-kernel/20240107203258.37e26d2b@gandalf.local.home

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andy Shevchenko <andy@kernel.org>
Cc: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Author: rostedt

kernel/trace/trace_events_hist.c

@@ -4805,36 +4805,35 @@ static int parse_actions(struct hist_trigger_data *hist_data)
 	int len;
 
 	for (i = 0; i < hist_data->attrs->n_actions; i++) {
+		enum handler_id hid = 0;
+		char *action_str;
+
 		str = hist_data->attrs->action_str[i];
 
-		if ((len = str_has_prefix(str, "onmatch("))) {
-			char *action_str = str + len;
+		if ((len = str_has_prefix(str, "onmatch(")))
+			hid = HANDLER_ONMATCH;
+		else if ((len = str_has_prefix(str, "onmax(")))
+			hid = HANDLER_ONMAX;
+		else if ((len = str_has_prefix(str, "onchange(")))
+			hid = HANDLER_ONCHANGE;
 
-			data = onmatch_parse(tr, action_str);
-			if (IS_ERR(data)) {
-				ret = PTR_ERR(data);
-				break;
-			}
-		} else if ((len = str_has_prefix(str, "onmax("))) {
-			char *action_str = str + len;
+		action_str = str + len;
 
-			data = track_data_parse(hist_data, action_str,
-						HANDLER_ONMAX);
-			if (IS_ERR(data)) {
-				ret = PTR_ERR(data);
-				break;
-			}
-		} else if ((len = str_has_prefix(str, "onchange("))) {
-			char *action_str = str + len;
+		switch (hid) {
+		case HANDLER_ONMATCH:
+			data = onmatch_parse(tr, action_str);
+			break;
+		case HANDLER_ONMAX:
+		case HANDLER_ONCHANGE:
+			data = track_data_parse(hist_data, action_str, hid);
+			break;
+		default:
+			data = ERR_PTR(-EINVAL);
+			break;
+		}
 
-			data = track_data_parse(hist_data, action_str,
-						HANDLER_ONCHANGE);
-			if (IS_ERR(data)) {
-				ret = PTR_ERR(data);
-				break;
-			}
-		} else {
-			ret = -EINVAL;
+		if (IS_ERR(data)) {
+			ret = PTR_ERR(data);
 			break;
 		}