linux-kernel - Re: [PATCH v18 2/3] mm: memory-failure: move return value documentation to function declaration

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Message-ID: <Z8BbFRupgknBTvH8@arm.com>
Date: Thu, 27 Feb 2025 12:31:17 +0000
From: Catalin Marinas <catalin.marinas@....com>
To: Shuai Xue <xueshuai@...ux.alibaba.com>
Cc: yazen.ghannam@....com, mark.rutland@....com, mingo@...hat.com,
	robin.murphy@....com, Jonathan.Cameron@...wei.com, bp@...en8.de,
	rafael@...nel.org, linux-arm-kernel@...ts.infradead.org,
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	zhuo.song@...ux.alibaba.com
Subject: Re: [PATCH v18 2/3] mm: memory-failure: move return value
 documentation to function declaration

(going through patches in my inbox)

On Tue, Jan 07, 2025 at 04:17:34PM +0800, Shuai Xue wrote:
> Part of return value comments for memory_failure() were originally
> documented at the call site. Move those comments to the function
> declaration to improve code readability and to provide developers with

s/declaration/definition/

> immediate access to function usage and return information.
> 
> Signed-off-by: Shuai Xue <xueshuai@...ux.alibaba.com>
> Reviewed-by: Jarkko Sakkinen <jarkko@...nel.org>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Reviewed-by: Yazen Ghannam <yazen.ghannam@....com>
> Reviewed-by: Jane Chu <jane.chu@...cle.com>
> ---
>  arch/x86/kernel/cpu/mce/core.c |  7 -------
>  mm/memory-failure.c            | 10 +++++++---
>  2 files changed, 7 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
> index 7fb5556a0b53..d1dd7f892514 100644
> --- a/arch/x86/kernel/cpu/mce/core.c
> +++ b/arch/x86/kernel/cpu/mce/core.c
> @@ -1398,13 +1398,6 @@ static void kill_me_maybe(struct callback_head *cb)
>  		return;
>  	}
>  
> -	/*
> -	 * -EHWPOISON from memory_failure() means that it already sent SIGBUS
> -	 * to the current process with the proper error info,
> -	 * -EOPNOTSUPP means hwpoison_filter() filtered the error event,
> -	 *
> -	 * In both cases, no further processing is required.
> -	 */
>  	if (ret == -EHWPOISON || ret == -EOPNOTSUPP)
>  		return;
>  
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index a7b8ccd29b6f..14c316d7d38d 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -2211,9 +2211,13 @@ static void kill_procs_now(struct page *p, unsigned long pfn, int flags,
>   * Must run in process context (e.g. a work queue) with interrupts
>   * enabled and no spinlocks held.
>   *
> - * Return: 0 for successfully handled the memory error,
> - *         -EOPNOTSUPP for hwpoison_filter() filtered the error event,
> - *         < 0(except -EOPNOTSUPP) on failure.
> + * Return:
> + *   0             - success,
> + *   -ENXIO        - memory not managed by the kernel
> + *   -EOPNOTSUPP   - hwpoison_filter() filtered the error event,
> + *   -EHWPOISON    - the page was already poisoned, potentially
> + *                   kill process,
> + *   other negative values - failure.
>   */
>  int memory_failure(unsigned long pfn, int flags)
>  {

Why not keep the comment in both places? One is about the x86 decisions,
the other is about what memory_failure() can return.

-- 
Catalin