linux-kernel - Re: [PATCH V4 06/12] trace: Add a generic function to read/write u64 values from tracefs

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Message-ID: <20210618125651.7de04840@oasis.local.home>
Date:   Fri, 18 Jun 2021 12:56:51 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Daniel Bristot de Oliveira <bristot@...hat.com>
Cc:     Phil Auld <pauld@...hat.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Kate Carcia <kcarcia@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        Clark Willaims <williams@...hat.com>,
        John Kacur <jkacur@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V4 06/12] trace: Add a generic function to read/write
 u64 values from tracefs

On Tue, 15 Jun 2021 11:28:45 +0200
Daniel Bristot de Oliveira <bristot@...hat.com> wrote:
> +static ssize_t
> +trace_min_max_read(struct file *filp, char __user *ubuf, size_t cnt,
> +		      loff_t *ppos)
> +{
> +	struct trace_min_max_param *param = filp->private_data;
> +	char buf[ULL_STR_SIZE];
> +	u64 val;
> +        int len;

White space issue above?

> +
> +        if (!param)
> +                return -EFAULT;

And above here too?


> +
> +	val = *param->val;
> +
> +        if (cnt > sizeof(buf))
> +                cnt = sizeof(buf);
> +
> +        len = snprintf(buf, sizeof(buf), "%llu\n", val);
> +
> +        return simple_read_from_buffer(ubuf, cnt, ppos, buf, len);

Egad, this entire patch is filled with whitespace issues!

Please check your other patches too.

> +}
> +


> +
> +#define ULL_STR_SIZE		22	/* 20 digits max */

Nit. I'd make this 24, just to be integer aligned. I mean, it's used as:


trace_min_max_read(struct file *filp, char __user *ubuf, size_t cnt,
		      loff_t *ppos)
{
	struct trace_min_max_param *param = filp->private_data;
	char buf[ULL_STR_SIZE];
	u64 val;
	int len;

Probably should reverse the above as well, that way if you do have
ULL_STR_SIZE as 24, then the int len, will fit right in before the u64
val. Although, I think compilers are free to optimize that too :-/

-- Steve