linux-kernel - Re: [PATCH v1 7/7] panic: sys_info: Factor out read and write handlers

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Message-ID: <aHEpHEtnPms2LUi-@U-2FWC9VHC-2323.local>
Date: Fri, 11 Jul 2025 23:09:16 +0800
From: Feng Tang <feng.tang@...ux.alibaba.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: linux-kernel@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>,
	Nathan Chancellor <nathan@...nel.org>
Subject: Re: [PATCH v1 7/7] panic: sys_info: Factor out read and write
 handlers

On Fri, Jul 11, 2025 at 12:51:13PM +0300, Andy Shevchenko wrote:
> For the sake of the code readability and easier maintenance
> factor out read and write sys_info handlers.

IIRC, I did implement separate 'write' handler, but chose not
to do that to save some common definition. I guess it's personal
preference, and I'm fine with either one. 

Thanks,
Feng

> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>  lib/sys_info.c | 72 ++++++++++++++++++++++++++++++--------------------
>  1 file changed, 44 insertions(+), 28 deletions(-)
> 
> diff --git a/lib/sys_info.c b/lib/sys_info.c
> index 7483b6e9b30b..32bf639c4de2 100644
> --- a/lib/sys_info.c
> +++ b/lib/sys_info.c
> @@ -40,13 +40,52 @@ unsigned long sys_info_parse_param(char *str)
>  }
>  
>  #ifdef CONFIG_SYSCTL
> +static int sys_info_write_handler(struct ctl_table *table,
> +				  void *buffer, size_t *lenp, loff_t *ppos,
> +				  unsigned long *si_bits_global)
> +{
> +	unsigned long si_bits;
> +	int ret;
> +
> +	ret = proc_dostring(table, 1, buffer, lenp, ppos);
> +	if (ret)
> +		return ret;
> +
> +	si_bits = sys_info_parse_param(table->data);
> +
> +	/* The access to the global value is not synchronized. */
> +	WRITE_ONCE(*si_bits_global, si_bits);
> +
> +	return 0;
> +}
> +
> +static int sys_info_read_handler(struct ctl_table *table,
> +				 void *buffer, size_t *lenp, loff_t *ppos,
> +				 unsigned long *si_bits_global)
> +{
> +	unsigned long si_bits;
> +	unsigned int len = 0;
> +	char *delim = "";
> +	unsigned int i;
> +
> +	/* The access to the global value is not synchronized. */
> +	si_bits = READ_ONCE(*si_bits_global);
> +
> +	for_each_set_bit(i, &si_bits, ARRAY_SIZE(si_names)) {
> +		len += scnprintf(table->data + len, table->maxlen - len,
> +				 "%s%s", delim, si_names[i]);
> +		delim = ",";
> +	}
> +
> +	return proc_dostring(table, 0, buffer, lenp, ppos);
> +}
> +
>  int sysctl_sys_info_handler(const struct ctl_table *ro_table, int write,
>  					  void *buffer, size_t *lenp,
>  					  loff_t *ppos)
>  {
>  	struct ctl_table table;
>  	unsigned long *si_bits_global;
> -	unsigned long si_bits;
>  	unsigned int i;
>  	size_t maxlen;
>  
> @@ -64,33 +103,10 @@ int sysctl_sys_info_handler(const struct ctl_table *ro_table, int write,
>  	table.data = names;
>  	table.maxlen = maxlen;
>  
> -	if (write) {
> -		int ret;
> -
> -		ret = proc_dostring(&table, write, buffer, lenp, ppos);
> -		if (ret)
> -			return ret;
> -
> -		si_bits = sys_info_parse_param(names);
> -		/* The access to the global value is not synchronized. */
> -		WRITE_ONCE(*si_bits_global, si_bits);
> -		return 0;
> -	} else {
> -		/* for 'read' operation */
> -		unsigned int len = 0;
> -		char *delim = "";
> -
> -		/* The access to the global value is not synchronized. */
> -		si_bits = READ_ONCE(*si_bits_global);
> -
> -		for_each_set_bit(i, &si_bits, ARRAY_SIZE(si_names)) {
> -			len += scnprintf(names + len, maxlen - len,
> -					 "%s%s", delim, si_names[i]);
> -			delim = ",";
> -		}
> -
> -		return proc_dostring(&table, write, buffer, lenp, ppos);
> -	}
> +	if (write)
> +		return sys_info_write_handler(&table, buffer, lenp, ppos, si_bits_global);
> +	else
> +		return sys_info_read_handler(&table, buffer, lenp, ppos, si_bits_global);
>  }
>  #endif
>  
> -- 
> 2.47.2