linux-kernel - Re: [PATCH] tracing: Have the error of __tracing_resize_ring

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Message-Id: <20250214092732.32e4a05358f2e9a96fecf5d7@kernel.org>
Date: Fri, 14 Feb 2025 09:27:32 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: LKML <linux-kernel@...r.kernel.org>, Linux Trace Kernel
 <linux-trace-kernel@...r.kernel.org>, Masami Hiramatsu
 <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Vincent Donnefort <vdonnefort@...gle.com>
Subject: Re: [PATCH] tracing: Have the error of
 __tracing_resize_ring_buffer() passed to user

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

> From: Steven Rostedt <rostedt@...dmis.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@...nel.org>

Thanks,

> Cc: stable@...r.kernel.org
> Fixes: 117c39200d9d7 ("ring-buffer: Introducing ring-buffer mapping functions")
> Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.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@...nel.org>