[PATCH] ring-buffer: Unlock resize on mmap error

[PATCH] ring-buffer: Unlock resize on mmap error

[Steven Rostedt]

From: Steven Rostedt <rostedt@goodmis.org>

Memory mapping the tracing ring buffer will disable resizing the buffer.
But if there's an error in the memory mapping like an invalid parameter,
the function exits out without re-enabling the resizing of the ring
buffer, preventing the ring buffer from being resized after that.

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/ring_buffer.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index b8e0ae15ca5b..07b421115692 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -7126,6 +7126,7 @@ int ring_buffer_map(struct trace_buffer *buffer, int cpu,
 		kfree(cpu_buffer->subbuf_ids);
 		cpu_buffer->subbuf_ids = NULL;
 		rb_free_meta_page(cpu_buffer);
+		atomic_dec(&cpu_buffer->resize_disabled);
 	}
 
 unlock:
-- 
2.47.2

Re: [PATCH] ring-buffer: Unlock resize on mmap error

[Masami Hiramatsu]

On Thu, 13 Feb 2025 13:19:57 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:

> From: Steven Rostedt <rostedt@goodmis.org>
> 
> Memory mapping the tracing ring buffer will disable resizing the buffer.
> But if there's an error in the memory mapping like an invalid parameter,
> the function exits out without re-enabling the resizing of the ring
> buffer, preventing the ring buffer from being resized after that.
> 

Looks good to me.

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

Thank you,

> 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/ring_buffer.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
> index b8e0ae15ca5b..07b421115692 100644
> --- a/kernel/trace/ring_buffer.c
> +++ b/kernel/trace/ring_buffer.c
> @@ -7126,6 +7126,7 @@ int ring_buffer_map(struct trace_buffer *buffer, int cpu,
>  		kfree(cpu_buffer->subbuf_ids);
>  		cpu_buffer->subbuf_ids = NULL;
>  		rb_free_meta_page(cpu_buffer);
> +		atomic_dec(&cpu_buffer->resize_disabled);
>  	}
>  
>  unlock:
> -- 
> 2.47.2
> 


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