linux-kernel - Re: [PATCH] btrfs: replace snprintf in show functions with sysfs

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Message-ID: <20211013103642.GC9286@twin.jikos.cz>
Date:   Wed, 13 Oct 2021 12:36:42 +0200
From:   David Sterba <dsterba@...e.cz>
To:     Anand Jain <anand.jain@...cle.com>
Cc:     Qing Wang <wangqing@...o.com>, Chris Mason <clm@...com>,
        Josef Bacik <josef@...icpanda.com>,
        David Sterba <dsterba@...e.com>, linux-btrfs@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] btrfs: replace snprintf in show functions with sysfs_emit

On Wed, Oct 13, 2021 at 03:51:33PM +0800, Anand Jain wrote:
> On 13/10/2021 11:28, Qing Wang wrote:
> > coccicheck complains about the use of snprintf() in sysfs show functions.
> 
> It looks like the reason is snprintf() unaware of the PAGE_SIZE 
> max_limit of the buf.
> 
> > Fix the following coccicheck warning:
> > fs/btrfs/sysfs.c:335:8-16: WARNING: use scnprintf or sprintf.
> 
> Hm. We use snprintf() at quite a lot more places in sysfs.c and, I don't 
> see them getting this fix. Why?

I guess the patch is only addressing the warning for snprintf, reading
the sources would show how many more conversions could have been done of
scnprintf calls.

> > Use sysfs_emit instead of scnprintf or sprintf makes more sense.
> 
> Below commit has added it. Nice.
> 
> commit 2efc459d06f1630001e3984854848a5647086232
> Date:   Wed Sep 16 13:40:38 2020 -0700
> 
>      sysfs: Add sysfs_emit and sysfs_emit_at to format sysfs out

The conversion to the standard helper is good, but should be done
in the entire file.