linux-kernel - Re: [PATCH] ring-buffer: Add rb_check_bpage in __rb_allocate

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Message-ID: <20201014113823.4296521d@gandalf.local.home>
Date:   Wed, 14 Oct 2020 11:38:23 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Qiujun Huang <hqjagain@...il.com>
Cc:     mingo@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ring-buffer: Add rb_check_bpage in __rb_allocate_pages

On Wed, 14 Oct 2020 23:16:14 +0800
Qiujun Huang <hqjagain@...il.com> wrote:

> It may be better to check each page is aligned by 4 bytes. The 2
> least significant bits of the address will be used as flags.
> 
> Signed-off-by: Qiujun Huang <hqjagain@...il.com>
> ---
>  kernel/trace/ring_buffer.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
> index 93ef0ab6ea20..9dec7d58b177 100644
> --- a/kernel/trace/ring_buffer.c
> +++ b/kernel/trace/ring_buffer.c
> @@ -1420,7 +1420,8 @@ static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
>  	return 0;
>  }
>  
> -static int __rb_allocate_pages(long nr_pages, struct list_head *pages, int cpu)
> +static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
> +		long nr_pages, struct list_head *pages, int cpu)
>  {
>  	struct buffer_page *bpage, *tmp;
>  	bool user_thread = current->mm != NULL;
> @@ -1464,6 +1465,8 @@ static int __rb_allocate_pages(long nr_pages, struct list_head *pages, int cpu)
>  		if (!bpage)
>  			goto free_pages;
>  
> +		rb_check_bpage(cpu_buffer, bpage);
> +
>  

Why add it here, and not just add this check to the scan in
rb_check_pages()?

-- Steve