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

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Message-ID: <226a6fc1-f6f4-4972-b76e-774094ffb821@p183>
Date:   Tue, 21 Mar 2023 17:37:10 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     brauner@...nel.org, frank.li@...o.com
Cc:     mcgrof@...nel.org, 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

> > +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...

It is better to keep all sysctls in one preallocated structure
for memory reasons:

	header = kzalloc(sizeof(struct ctl_table_header) +
                         sizeof(struct ctl_node)*nr_entries, GFP_KERNEL_ACCOUNT);