linux-kernel - Re: [PATCH] fs/drop_caches: move drop

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Date:   Tue, 21 Mar 2023 15:28:36 +0100
From:   Christian Brauner <brauner@...nel.org>
To:     Yangtao Li <frank.li@...o.com>,
        Luis Chamberlain <mcgrof@...nel.org>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        Iurii Zaikin <yzaikin@...gle.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH] fs/drop_caches: move drop_caches sysctls into its own
 file

On Tue, Mar 21, 2023 at 09:09:07PM +0800, Yangtao Li wrote:
> This moves the fs/drop_caches.c respective sysctls to its own file.
> 
> Signed-off-by: Yangtao Li <frank.li@...o.com>
> ---
>  fs/drop_caches.c   | 25 ++++++++++++++++++++++---
>  include/linux/mm.h |  6 ------
>  kernel/sysctl.c    |  9 ---------
>  3 files changed, 22 insertions(+), 18 deletions(-)
> 
> diff --git a/fs/drop_caches.c b/fs/drop_caches.c
> index e619c31b6bd9..3032b83ce6f2 100644
> --- a/fs/drop_caches.c
> +++ b/fs/drop_caches.c
> @@ -12,8 +12,7 @@
>  #include <linux/gfp.h>
>  #include "internal.h"
>  
> -/* A global variable is a bit ugly, but it keeps the code simple */
> -int sysctl_drop_caches;
> +static int sysctl_drop_caches;
>  
>  static void drop_pagecache_sb(struct super_block *sb, void *unused)
>  {
> @@ -47,7 +46,7 @@ static void drop_pagecache_sb(struct super_block *sb, void *unused)
>  	iput(toput_inode);
>  }
>  
> -int drop_caches_sysctl_handler(struct ctl_table *table, int write,
> +static int drop_caches_sysctl_handler(struct ctl_table *table, int write,
>  		void *buffer, size_t *length, loff_t *ppos)
>  {
>  	int ret;
> @@ -75,3 +74,23 @@ int drop_caches_sysctl_handler(struct ctl_table *table, int write,
>  	}
>  	return 0;
>  }
> +
> +static struct ctl_table drop_caches_table[] = {
> +	{
> +		.procname	= "drop_caches",
> +		.data		= &sysctl_drop_caches,
> +		.maxlen		= sizeof(int),
> +		.mode		= 0200,
> +		.proc_handler	= drop_caches_sysctl_handler,
> +		.extra1		= SYSCTL_ONE,
> +		.extra2		= SYSCTL_FOUR,
> +	},
> +	{}
> +};
> +
> +static int __init drop_cache_init(void)
> +{
> +	register_sysctl_init("vm", drop_caches_table);

Does this belong under mm/ or fs/?
And is it intended to be moved into a completely separate file?
Feels abit wasteful for 20 lines of code...