linux-kernel - Re: [PATCH RESEND 2/2] ring-buffer/selftest: Handle meta-page bigger than the system

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Message-ID: <20240910124555.180428eb@gandalf.local.home>
Date: Tue, 10 Sep 2024 12:45:55 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Vincent Donnefort <vdonnefort@...gle.com>
Cc: mhiramat@...nel.org, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org, kernel-team@...roid.com, Shuah Khan
 <skhan@...uxfoundation.org>, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH RESEND 2/2] ring-buffer/selftest: Handle meta-page
 bigger than the system


Shuah,

Can you take this through your tree?

Acked-by: Steven Rostedt (Google) <rostedt@...dmis.org>

-- Steve

On Tue, 10 Sep 2024 17:23:35 +0100
Vincent Donnefort <vdonnefort@...gle.com> wrote:

> Handle the case where the meta-page content is bigger than the system
> page-size. This prepares the ground for extending features covered by
> the meta-page.
> 
> Cc: Shuah Khan <skhan@...uxfoundation.org>
> Cc: linux-kselftest@...r.kernel.org
> Signed-off-by: Vincent Donnefort <vdonnefort@...gle.com>
> 
> diff --git a/tools/testing/selftests/ring-buffer/map_test.c b/tools/testing/selftests/ring-buffer/map_test.c
> index ba12fd31de87..d10a847130fb 100644
> --- a/tools/testing/selftests/ring-buffer/map_test.c
> +++ b/tools/testing/selftests/ring-buffer/map_test.c
> @@ -92,12 +92,22 @@ int tracefs_cpu_map(struct tracefs_cpu_map_desc *desc, int cpu)
>  	if (desc->cpu_fd < 0)
>  		return -ENODEV;
>  
> +again:
>  	map = mmap(NULL, page_size, PROT_READ, MAP_SHARED, desc->cpu_fd, 0);
>  	if (map == MAP_FAILED)
>  		return -errno;
>  
>  	desc->meta = (struct trace_buffer_meta *)map;
>  
> +	/* the meta-page is bigger than the original mapping */
> +	if (page_size < desc->meta->meta_struct_len) {
> +		int meta_page_size = desc->meta->meta_page_size;
> +
> +		munmap(desc->meta, page_size);
> +		page_size = meta_page_size;
> +		goto again;
> +	}
> +
>  	return 0;
>  }
>