linux-kernel - Re: [PATCH 32/32] x86/boot/e820: Move index increments outside accessors in e820__update

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Message-ID: <dc7c39c3-4388-4660-b3ae-e285419713d3@suse.com>
Date: Mon, 2 Jun 2025 17:57:50 +0300
From: Nikolay Borisov <nik.borisov@...e.com>
To: Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org
Cc: Andy Shevchenko <andy@...nel.org>, Arnd Bergmann <arnd@...nel.org>,
 Borislav Petkov <bp@...en8.de>, Juergen Gross <jgross@...e.com>,
 "H . Peter Anvin" <hpa@...or.com>, Kees Cook <keescook@...omium.org>,
 Linus Torvalds <torvalds@...ux-foundation.org>,
 Mike Rapoport <rppt@...nel.org>, Paul Menzel <pmenzel@...gen.mpg.de>,
 Peter Zijlstra <peterz@...radead.org>, Thomas Gleixner <tglx@...utronix.de>,
 David Woodhouse <dwmw@...zon.co.uk>
Subject: Re: [PATCH 32/32] x86/boot/e820: Move index increments outside
 accessors in e820__update_table()

On 5/15/25 15:05, Ingo Molnar wrote:
> This kind of code:
> 
> 	change_point[chg_idx++]->entry  = &entries[idx];
> 
> Can be a bit confusing to human readers, and GCC-15 started
> warning about these patterns.
> 
> Move the index increment outside the accessor.
> 
> Suggested-by: Andy Shevchenko <andy@...nel.org>
> Signed-off-by: Ingo Molnar <mingo@...nel.org>
> Cc: Arnd Bergmann <arnd@...nel.org>
> Cc: David Woodhouse <dwmw@...zon.co.uk>
> Cc: H. Peter Anvin <hpa@...or.com>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Cc: Mike Rapoport (Microsoft) <rppt@...nel.org>
> ---
>   arch/x86/kernel/e820.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
> index 10c6e7dc72d7..afb312620c82 100644
> --- a/arch/x86/kernel/e820.c
> +++ b/arch/x86/kernel/e820.c
> @@ -421,9 +421,11 @@ __init int e820__update_table(struct e820_table *table)
>   	for (idx = 0; idx < table->nr_entries; idx++)	{
>   		if (entries[idx].size != 0) {
nit: The level of nesting can easily be reduced by doing
if (entries[idx].size == 0)
	continue;
>   			change_point[chg_idx]->addr	= entries[idx].addr;
> -			change_point[chg_idx++]->entry	= &entries[idx];
> +			change_point[chg_idx]->entry	= &entries[idx];
> +			chg_idx++;

nit: I have to agree with H. Peter Anvin that this seems somewhat odd to 
me as well.

<snip>