linux-kernel - Re: [PATCH] kprobes: no need to check return value of debugfs

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Date:   Wed, 23 Jan 2019 11:15:16 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org,
        "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Masami Hiramatsu <mhiramat@...nel.org>
Subject: Re: [PATCH] kprobes: no need to check return value of
 debugfs_create functions

On Tue, 22 Jan 2019 16:21:46 +0100
Greg Kroah-Hartman <gregkh@...uxfoundation.org> wrote:

> When calling debugfs functions, there is no need to ever check the
> return value.  The function can work or not, but the code logic should
> never do something different based on this.
> 
> Cc: "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>
> Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Masami Hiramatsu <mhiramat@...nel.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> ---
>  kernel/kprobes.c | 25 ++++++-------------------
>  1 file changed, 6 insertions(+), 19 deletions(-)
> 
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index f4ddfdd2d07e..7287e7de2350 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -2566,33 +2566,20 @@ static const struct file_operations fops_kp = {
>  
>  static int __init debugfs_kprobe_init(void)
>  {
> -	struct dentry *dir, *file;
> +	struct dentry *dir;
>  	unsigned int value = 1;
>  
>  	dir = debugfs_create_dir("kprobes", NULL);
> -	if (!dir)
> -		return -ENOMEM;

Here, I think IS_ERR(dir) is OK for debugfs_create_file(),
but dir == NULL has different meaning. I think we'd better
keep this check. (I see, -ENOMEM will be no good...)

Thank you,

>  
> -	file = debugfs_create_file("list", 0400, dir, NULL,
> -				&debugfs_kprobes_operations);
> -	if (!file)
> -		goto error;
> +	debugfs_create_file("list", 0400, dir, NULL,
> +			    &debugfs_kprobes_operations);
>  
> -	file = debugfs_create_file("enabled", 0600, dir,
> -					&value, &fops_kp);
> -	if (!file)
> -		goto error;
> +	debugfs_create_file("enabled", 0600, dir, &value, &fops_kp);
>  
> -	file = debugfs_create_file("blacklist", 0400, dir, NULL,
> -				&debugfs_kprobe_blacklist_ops);
> -	if (!file)
> -		goto error;
> +	debugfs_create_file("blacklist", 0400, dir, NULL,
> +			    &debugfs_kprobe_blacklist_ops);
>  
>  	return 0;
> -
> -error:
> -	debugfs_remove(dir);
> -	return -ENOMEM;
>  }
>  
>  late_initcall(debugfs_kprobe_init);
> -- 
> 2.20.1
> 


-- 
Masami Hiramatsu <mhiramat@...nel.org>