linux-kernel - Re: [PATCH -next] sched/fair: Use struct

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Message-ID: <20230725132559.GK3765278@hirez.programming.kicks-ass.net>
Date:   Tue, 25 Jul 2023 15:25:59 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Ruan Jinjie <ruanjinjie@...wei.com>
Cc:     mingo@...hat.com, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com, vschneid@...hat.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next] sched/fair: Use struct_size()

On Tue, Jul 25, 2023 at 07:50:20PM +0000, Ruan Jinjie wrote:
> Use struct_size() instead of hand-writing it, when allocating a structure
> with a flex array.
> 
> This is less verbose.

As per all the other times, no. It is also less clear. I never can
remember what that thing does and the code it replaces is utterly
trivial.

> Signed-off-by: Ruan Jinjie <ruanjinjie@...wei.com>
> ---
>  kernel/sched/fair.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index f8b71ea5948b..cc041a48100f 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -2889,9 +2889,8 @@ static void task_numa_group(struct task_struct *p, int cpupid, int flags,
>  	int i;
>  
>  	if (unlikely(!deref_curr_numa_group(p))) {
> -		unsigned int size = sizeof(struct numa_group) +
> -				    NR_NUMA_HINT_FAULT_STATS *
> -				    nr_node_ids * sizeof(unsigned long);
> +		unsigned int size = struct_size(grp, faults,
> +		                                NR_NUMA_HINT_FAULT_STATS * nr_node_ids);
>  
>  		grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
>  		if (!grp)
> -- 
> 2.34.1
>