tracing: Have the error of __tracing_resize_ring_buffer() passed to user

BugLink: https://bugs.launchpad.net/bugs/2106494

[ Upstream commit 60b8f71 ]

Currently if __tracing_resize_ring_buffer() returns an error, the
tracing_resize_ringbuffer() returns -ENOMEM. But it may not be a memory
issue that caused the function to fail. If the ring buffer is memory
mapped, then the resizing of the ring buffer will be disabled. But if the
user tries to resize the buffer, it will get an -ENOMEM returned, which is
confusing because there is plenty of memory. The actual error returned was
-EBUSY, which would make much more sense to the user.

Cc: [email protected]
Cc: Mathieu Desnoyers <[email protected]>
Cc: Vincent Donnefort <[email protected]>
Link: https://lore.kernel.org/[email protected]
Fixes: 117c392 ("ring-buffer: Introducing ring-buffer mapping functions")
Signed-off-by: Steven Rostedt (Google) <[email protected]>
Reviewed-by: Masami Hiramatsu (Google) <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
Signed-off-by: Noah Wager <[email protected]>
Signed-off-by: Mehmet Basaran <[email protected]>

Author: rostedt

kernel/trace/trace.c

@@ -5911,8 +5911,6 @@ static int __tracing_resize_ring_buffer(struct trace_array *tr,
 ssize_t tracing_resize_ring_buffer(struct trace_array *tr,
 				  unsigned long size, int cpu_id)
 {
-	int ret;
-
 	guard(mutex)(&trace_types_lock);
 
 	if (cpu_id != RING_BUFFER_ALL_CPUS) {
@@ -5921,11 +5919,7 @@ ssize_t tracing_resize_ring_buffer(struct trace_array *tr,
 			return -EINVAL;
 	}
 
-	ret = __tracing_resize_ring_buffer(tr, size, cpu_id);
-	if (ret < 0)
-		ret = -ENOMEM;
-
-	return ret;
+	return __tracing_resize_ring_buffer(tr, size, cpu_id);
 }