linux-kernel - Re: [PATCH v2 1/3] lib/vsprintf: Avoid redundant work with 0 size

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Message-ID: <YfdPNPCjSZ5WI9+4@google.com>
Date:   Mon, 31 Jan 2022 11:53:40 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     Waiman Long <longman@...hat.com>
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
        linux-mm@...ck.org, Ira Weiny <ira.weiny@...el.com>,
        Rafael Aquini <aquini@...hat.com>
Subject: Re: [PATCH v2 1/3] lib/vsprintf: Avoid redundant work with 0 size

On (22/01/29 15:53), Waiman Long wrote:
> For *scnprintf(), vsnprintf() is always called even if the input size is
> 0. That is a waste of time, so just return 0 in this case.
> 
> Signed-off-by: Waiman Long <longman@...hat.com>

Reviewed-by: Sergey Senozhatsky <senozhatsky@...omium.org>


> +++ b/lib/vsprintf.c
> @@ -2895,13 +2895,15 @@ int vscnprintf(char *buf, size_t size, const char *fmt, va_list args)
>  {
>  	int i;
>  
> +	if (!size)
> +		return 0;
> +
>  	i = vsnprintf(buf, size, fmt, args);
>  
>  	if (likely(i < size))
>  		return i;
> -	if (size != 0)
> -		return size - 1;
> -	return 0;
> +
> +	return size - 1;
>  }
>  EXPORT_SYMBOL(vscnprintf);