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

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

[Steven Rostedt]

From: Steven Rostedt <rostedt@goodmis.org>

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: stable@vger.kernel.org
Fixes: 117c39200d9d7 ("ring-buffer: Introducing ring-buffer mapping functions")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 kernel/trace/trace.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 1496a5ac33ae..25ff37aab00f 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -5977,8 +5977,6 @@ 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) {
@@ -5987,11 +5985,7 @@ 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);
 }
 
 static void update_last_data(struct trace_array *tr)
-- 
2.47.2

Re: [PATCH] tracing: Have the error of __tracing_resize_ring_buffer() passed to user

[Masami Hiramatsu]

On Thu, 13 Feb 2025 13:41:32 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:

> From: Steven Rostedt <rostedt@goodmis.org>
> 
> 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.
> 

Looks good to me.

Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Thanks,

> Cc: stable@vger.kernel.org
> Fixes: 117c39200d9d7 ("ring-buffer: Introducing ring-buffer mapping functions")
> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
> ---
>  kernel/trace/trace.c | 8 +-------
>  1 file changed, 1 insertion(+), 7 deletions(-)
> 
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 1496a5ac33ae..25ff37aab00f 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -5977,8 +5977,6 @@ 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) {
> @@ -5987,11 +5985,7 @@ 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);
>  }
>  
>  static void update_last_data(struct trace_array *tr)
> -- 
> 2.47.2
> 


-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>