linux-kernel - Re: [PATCH] perf: arm_spe: remove unnecessary zero check

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Message-ID: <20200309105219.GC25261@lakrids.cambridge.arm.com>
Date:   Mon, 9 Mar 2020 10:52:20 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     luanshi <zhangliguang@...ux.alibaba.com>
Cc:     Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf: arm_spe: remove unnecessary zero check

On Wed, Feb 26, 2020 at 12:25:06PM +0800, luanshi wrote:
> The "nr_pages" variable has been checked before, it can't be zero, so a check here would be useless.
> 
> Signed-off-by: Liguang Zhang <zhangliguang@...ux.alibaba.com>

As the commit message states, a  done:

| /* We need at least two pages for this to work. */
| if (nr_pages < 2)
|         return NULL;

... so this looks sensible to me:

Acked-by: Mark Rutland <mark.rutland@....com>

Mark.

> ---
>  drivers/perf/arm_spe_pmu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/perf/arm_spe_pmu.c b/drivers/perf/arm_spe_pmu.c
> index 4e4984a..b72c048 100644
> --- a/drivers/perf/arm_spe_pmu.c
> +++ b/drivers/perf/arm_spe_pmu.c
> @@ -831,7 +831,7 @@ static void *arm_spe_pmu_setup_aux(struct perf_event *event, void **pages,
>  	 * parts and give userspace a fighting chance of getting some
>  	 * useful data out of it.
>  	 */
> -	if (!nr_pages || (snapshot && (nr_pages & 1)))
> +	if (snapshot && (nr_pages & 1))
>  		return NULL;
>  
>  	if (cpu == -1)
> -- 
> 1.8.3.1
>