linux-kernel - Re: [PATCH] ring-buffer: remove obsolete comment for free_buffer

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Date:   Thu, 16 Mar 2023 09:29:30 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Mukesh Ojha <quic_mojha@...cinc.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Ingo Molnar <mingo@...e.hu>
Cc:     linux-trace-kernel@...r.kernel.org, linux-kernel@...r.kernel.org,
        patches@...ts.linux.dev, Mike Rapoport <mike.rapoport@...il.com>
Subject: Re: [PATCH] ring-buffer: remove obsolete comment for
 free_buffer_page()

On 3/15/23 16:53, Mukesh Ojha wrote:
> 
> 
> On 3/15/2023 9:21 PM, Mukesh Ojha wrote:
>> 
>> 
>> On 3/15/2023 7:54 PM, Vlastimil Babka wrote:
>>> The comment refers to mm/slob.o which is being removed. It comes from
> 
> nit: mm/slob.c

Thanks, Steven can you fix that up while picking the patch, or need v2?

> -- Mukesh
> 
>> 
>> 
>>> commit ed56829cb319 ("ring_buffer: reset buffer page when freeing") and
>>> according to Steven the borrowed code was a page mapcount and mapping
>>> reset, which was later removed by commit e4c2ce82ca27 ("ring_buffer:
>>> allocate buffer page pointer"). Thus the comment is not accurate anyway,
>>> remove it.
>>>
>>> Reported-by: Mike Rapoport <mike.rapoport@...il.com>
>>> Suggested-by: Steven Rostedt (Google) <rostedt@...dmis.org>
>>> Fixes: e4c2ce82ca27 ("ring_buffer: allocate buffer page pointer")
>>> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
>>> ---
>>>   kernel/trace/ring_buffer.c | 4 ----
>>>   1 file changed, 4 deletions(-)
>>>
>>> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
>>> index af50d931b020..c6f47b6cfd5f 100644
>>> --- a/kernel/trace/ring_buffer.c
>>> +++ b/kernel/trace/ring_buffer.c
>>> @@ -354,10 +354,6 @@ static void rb_init_page(struct buffer_data_page 
>>> *bpage)
>>>       local_set(&bpage->commit, 0);
>>>   }
>>> -/*
>>> - * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
>>> - * this issue out.
>>> - */
>> 
>> Thanks for the clean up.
>> 
>> Reviewed-by: Mukesh Ojha <quic_mojha@...cinc.com>

Thanks.

>> 
>> -- Mukesh
>> 
>>>   static void free_buffer_page(struct buffer_page *bpage)
>>>   {
>>>       free_page((unsigned long)bpage->page);