linux-kernel - Re: [PATCH 08/11] sysctl: Add size to register_sysctl

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Message-ID: <ZJLgzo1GuykDV8fd@alley>
Date:   Wed, 21 Jun 2023 13:36:46 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     Joel Granados <j.granados@...sung.com>
Cc:     mcgrof@...nel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
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Subject: Re: [PATCH 08/11] sysctl: Add size to register_sysctl_init

On Wed 2023-06-21 11:09:57, Joel Granados wrote:
> In order to remove the end element from the ctl_table struct arrays, we
> explicitly define the size when registering the targes. We add a size
> argument to the register_sysctl_init call and pass an ARRAY_SIZE for all
> the callers.

This does not explain the motivatin why the end element is removed.

I agree with Jiri that saving 9k is a questionable gain. According to
the cover letter it saved 0,00%. It is because it saved 9k with allyes
config which produces huge kernel. IMHO, the 9k might be interesting
only for a tiny kernel. But I guess that it would safe much less
bytes there.

And the code with the added ARRAY_SIZE() parameter looks worse than before.

> diff --git a/kernel/printk/sysctl.c b/kernel/printk/sysctl.c
> index c228343eeb97..28f37b86414e 100644
> --- a/kernel/printk/sysctl.c
> +++ b/kernel/printk/sysctl.c
> @@ -81,5 +81,6 @@ static struct ctl_table printk_sysctls[] = {
>  
>  void __init printk_sysctl_init(void)
>  {
> -	register_sysctl_init("kernel", printk_sysctls);
> +	register_sysctl_init("kernel", printk_sysctls,
> +			     ARRAY_SIZE(printk_sysctls));
>  }

Is register_sysctl_init() still ready to handle the last empty element,
please? I am not in Cc on the related patches.

Best Regards,
Petr