linux-kernel - Re: [PATCH 4/5] mm: shmem: Convert shmem_enabled_show to use sysfs_emit

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Message-ID: <20201101204834.GF27442@casper.infradead.org>
Date:   Sun, 1 Nov 2020 20:48:34 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     Joe Perches <joe@...ches.com>
Cc:     Hugh Dickins <hughd@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/5] mm: shmem: Convert shmem_enabled_show to use
 sysfs_emit_at

On Sun, Nov 01, 2020 at 12:12:51PM -0800, Joe Perches wrote:
> @@ -4024,7 +4024,7 @@ int __init shmem_init(void)
>  
>  #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && defined(CONFIG_SYSFS)
>  static ssize_t shmem_enabled_show(struct kobject *kobj,
> -		struct kobj_attribute *attr, char *buf)
> +				  struct kobj_attribute *attr, char *buf)
>  {
>  	static const int values[] = {
>  		SHMEM_HUGE_ALWAYS,

Why?

> @@ -4034,16 +4034,19 @@ static ssize_t shmem_enabled_show(struct kobject *kobj,
>  		SHMEM_HUGE_DENY,
>  		SHMEM_HUGE_FORCE,
>  	};
> -	int i, count;
> -
> -	for (i = 0, count = 0; i < ARRAY_SIZE(values); i++) {
> -		const char *fmt = shmem_huge == values[i] ? "[%s] " : "%s ";
> +	int len = 0;
> +	int i;

Better:
	int i, len = 0;

> -		count += sprintf(buf + count, fmt,
> -				shmem_format_huge(values[i]));
> +	for (i = 0; i < ARRAY_SIZE(values); i++) {
> +		len += sysfs_emit_at(buf, len,
> +				     shmem_huge == values[i] ? "%s[%s]" : "%s%s",
> +				     i ? " " : "",
> +				     shmem_format_huge(values[i]));

This is ... complicated.  I thought the point of doing all the sysfs_emit
stuff was to simplify things.