[PATCH 4.19 16/77] Revert "tracing/trigger: Fix to return error if failed to alloc snapshot"

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Siddh Raman Pant <siddh.raman.pant@xxxxxxxxxx>

This reverts commit bcf4a115a5068f3331fafb8c176c1af0da3d8b19 which is
commit 0958b33ef5a04ed91f61cef4760ac412080c4e08 upstream.

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@xxxxxxxxxx # 5.15, 5.10, 5.4, 4.19
Signed-off-by: Siddh Raman Pant <siddh.raman.pant@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 kernel/trace/trace_events_trigger.c |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -1133,10 +1133,8 @@ register_snapshot_trigger(char *glob, st
 			  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);
 }