linux-kernel - [PATCH] Revert "tracing/trigger: Fix to return error if failed to alloc snapshot"

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Date: Thu, 18 Apr 2024 18:58:06 +0530
From: Siddh Raman Pant <siddh.raman.pant@...cle.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Steven Rostedt <rostedt@...dmis.org>, Ingo Molnar <mingo@...hat.com>
Cc: linux-trace-kernel <linux-trace-kernel@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>, stable@...nel.org
Subject: [PATCH] Revert "tracing/trigger: Fix to return error if failed to alloc snapshot"

This reverts commit b5085b5ac1d96ea2a8a6240f869655176ce44197.

The change has an incorrect assumption about the return value because
in the current stable trees for versions 5.15 and before, the following
commit responsible for making 0 a success value is not present:
b8cc44a4d3c1 ("tracing: Remove logic for registering multiple event triggers at a time")

The return value should be 0 on failure in the current tree, because in
the functions event_trigger_callback() and event_enable_trigger_func(),
we have:

	ret = cmd_ops->reg(glob, trigger_ops, trigger_data, file);
	/*
	 * The above returns on success the # of functions enabled,
	 * but if it didn't find any functions it returns zero.
	 * Consider no functions a failure too.
	 */
	if (!ret) {
		ret = -ENOENT;

Cc: stable@...nel.org # 5.15, 5.10, 5.4, 4.19
Signed-off-by: Siddh Raman Pant <siddh.raman.pant@...cle.com>
---
 kernel/trace/trace_events_trigger.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index dfdbcf1da216..106f9813841a 100644
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -1161,10 +1161,8 @@ register_snapshot_trigger(char *glob, struct event_trigger_ops *ops,
 			  struct event_trigger_data *data,
 			  struct trace_event_file *file)
 {
-	int ret = tracing_alloc_snapshot_instance(file->tr);
-
-	if (ret < 0)
-		return ret;
+	if (tracing_alloc_snapshot_instance(file->tr) != 0)
+		return 0;
 
 	return register_trigger(glob, ops, data, file);
 }
-- 
2.43.0