linux-kernel - Re: [PATCH -next] x86/events:Use struct

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Message-ID: <YoT6tHWbBOchi29i@hirez.programming.kicks-ass.net>
Date:   Wed, 18 May 2022 15:55:00 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc:     Lin Yujun <linyujun809@...wei.com>, mingo@...hat.com,
        acme@...nel.org, mark.rutland@....com,
        alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
        namhyung@...nel.org, tglx@...utronix.de, bp@...en8.de,
        dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        johnny.chenyi@...wei.com, chenjiahao16@...wei.com,
        chenlifu@...wei.com, lizhengyu3@...wei.com, liaochang1@...wei.com,
        wangzhu9@...wei.com, xuyihang@...wei.com, chris.zjh@...wei.com,
        zouyipeng@...wei.com
Subject: Re: [PATCH -next] x86/events:Use struct_size() helper in kzalloc()

On Wed, May 18, 2022 at 08:49:20AM -0500, Gustavo A. R. Silva wrote:

> > Signed-off-by: Lin Yujun <linyujun809@...wei.com>
> > ---
> >  arch/x86/events/rapl.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/arch/x86/events/rapl.c b/arch/x86/events/rapl.c
> > index 77e3a47af5ad..c7e79f0ac04f 100644
> > --- a/arch/x86/events/rapl.c
> > +++ b/arch/x86/events/rapl.c
> > @@ -685,7 +685,7 @@ static int __init init_rapl_pmus(void)
> >  	int maxdie = topology_max_packages() * topology_max_die_per_package();
> >  	size_t size;
> >  
> > -	size = sizeof(*rapl_pmus) + maxdie * sizeof(struct rapl_pmu *);
> > +	size = struct_size(rapl_pmus, pmus, maxdie);
> >  	rapl_pmus = kzalloc(size, GFP_KERNEL);
> 
> It seems that in this case, size could be entirely replaced by
> struct_size().

Except every time I look at struct_size() I go: WTF does that do; while
the code as-is is crystal clear, no de-obfucstaion required.