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

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Date:   Tue, 21 Mar 2023 09:56:03 -0700
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Yangtao Li <frank.li@...o.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>,
        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 04:42:32PM +0000, Matthew Wilcox wrote:
> On Tue, Mar 21, 2023 at 09:09:07PM +0800, Yangtao Li wrote:
> > +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,
> > +	},
> > +	{}
> > +};
> 
> Could we avoid doing this until we no longer need an entire zero entry
> after the last one? 

That may be 2-3 kernel release from now. The way to use ARRAY_SIZE()
really is to deprecate the crap APIs that allow messy directory sysctl
structures.

> Also, please post scripts/bloat-o-meter results
> for before-and-after.

It should be one extry ~ ctl_table per move.

  Luis