linux-kernel - Re: [PATCH bpf] bpf: Use cpumask_next_wrap() in get_next

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Message-ID: <75cd7b00-53b6-496f-a934-339eed8f9a72@iogearbox.net>
Date: Fri, 15 Aug 2025 11:03:33 +0200
From: Daniel Borkmann <daniel@...earbox.net>
To: Fushuai Wang <wangfushuai@...du.com>, linux-kernel@...r.kernel.org,
 bpf@...r.kernel.org
Cc: martin.lau@...ux.dev, ast@...nel.org, andrii@...nel.org,
 eddyz87@...il.com, song@...nel.org, yonghong.song@...ux.dev,
 john.fastabend@...il.com, kpsingh@...nel.org, sdf@...ichev.me,
 haoluo@...gle.com, jolsa@...nel.org
Subject: Re: [PATCH bpf] bpf: Use cpumask_next_wrap() in get_next_cpu()

On 8/7/25 4:48 AM, Fushuai Wang wrote:
> Replace the manual sequence of cpumask_next() and cpumask_first()
> with a single call to cpumask_next_wrap() in get_next_cpu().
> 
> Signed-off-by: Fushuai Wang <wangfushuai@...du.com>
> ---
>   kernel/bpf/bpf_lru_list.c | 5 +----
>   1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/kernel/bpf/bpf_lru_list.c b/kernel/bpf/bpf_lru_list.c
> index 2d6e1c98d8ad..34881f4da8ae 100644
> --- a/kernel/bpf/bpf_lru_list.c
> +++ b/kernel/bpf/bpf_lru_list.c
> @@ -21,10 +21,7 @@
>   
>   static int get_next_cpu(int cpu)
>   {
> -	cpu = cpumask_next(cpu, cpu_possible_mask);
> -	if (cpu >= nr_cpu_ids)
> -		cpu = cpumask_first(cpu_possible_mask);
> -	return cpu;
> +	return cpumask_next_wrap(cpu, cpu_possible_mask);
>   }

Lets then get rid of the get_next_cpu() function since its only used
once, and just use the cpumask_next_wrap() at call site ?

[...]
                 raw_spin_unlock_irqrestore(&steal_loc_l->lock, flags);

                 steal = cpumask_next_wrap(steal, cpu_possible_mask);
         } while (!node && steal != first_steal);
[...]

Btw, in $subj please target [PATCH bpf-next] given its a cleanup,
not a fix.

Thanks,
Daniel