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

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Message-ID: <6f03e790-6f21-703f-c761-a034575f465e@oracle.com>
Date:   Wed, 13 Oct 2021 15:51:33 +0800
From:   Anand Jain <anand.jain@...cle.com>
To:     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 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?

> 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

Thanks, Anand

> 
> Signed-off-by: Qing Wang <wangqing@...o.com>
> ---
>   fs/btrfs/sysfs.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
> index 9d1d140..fda094a 100644
> --- a/fs/btrfs/sysfs.c
> +++ b/fs/btrfs/sysfs.c
> @@ -332,7 +332,7 @@ BTRFS_ATTR(static_feature, supported_checksums, supported_checksums_show);
>   static ssize_t send_stream_version_show(struct kobject *kobj,
>   					struct kobj_attribute *ka, char *buf)
>   {
> -	return snprintf(buf, PAGE_SIZE, "%d\n", BTRFS_SEND_STREAM_VERSION);
> +	return sysfs_emit(buf, "%d\n", BTRFS_SEND_STREAM_VERSION);
>   }
>   BTRFS_ATTR(static_feature, send_stream_version, send_stream_version_show);
>   
>