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

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Date:   Wed, 12 Jun 2019 12:58:19 -0400
From:   Joel Fernandes <joel@...lfernandes.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Qian Cai <cai@....us>, Thomas Gleixner <tglx@...utronix.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Waiman Long <longman@...hat.com>,
        Zhong Jiang <zhongjiang@...wei.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] lib: debugobjects: no need to check return value of
 debugfs_create functions

On Wed, Jun 12, 2019 at 05:35:13PM +0200, Greg Kroah-Hartman 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: Qian Cai <cai@....us>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Waiman Long <longman@...hat.com>
> Cc: "Joel Fernandes (Google)" <joel@...lfernandes.org>
> Cc: Zhong Jiang <zhongjiang@...wei.com>
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> ---
>  lib/debugobjects.c | 14 ++------------
>  1 file changed, 2 insertions(+), 12 deletions(-)
> 
> diff --git a/lib/debugobjects.c b/lib/debugobjects.c
> index 55437fd5128b..2ac42286cd08 100644
> --- a/lib/debugobjects.c
> +++ b/lib/debugobjects.c
> @@ -850,26 +850,16 @@ static const struct file_operations debug_stats_fops = {
>  
>  static int __init debug_objects_init_debugfs(void)
>  {
> -	struct dentry *dbgdir, *dbgstats;
> +	struct dentry *dbgdir;
>  
>  	if (!debug_objects_enabled)
>  		return 0;
>  
>  	dbgdir = debugfs_create_dir("debug_objects", NULL);
> -	if (!dbgdir)
> -		return -ENOMEM;
>  
> -	dbgstats = debugfs_create_file("stats", 0444, dbgdir, NULL,
> -				       &debug_stats_fops);
> -	if (!dbgstats)
> -		goto err;
> +	debugfs_create_file("stats", 0444, dbgdir, NULL, &debug_stats_fops);


One weirdness is, if dbgdir is ever NULL, then debugfs_create_file() may end
up creating the stats file in the root.

In debugfs_create_file():
        /* If the parent is not specified, we create it in the root.
         * We need the root dentry to do this, which is in the super
         * block. A pointer to that is in the struct vfsmount that we
         * have around.
         */
        if (!parent)
                parent = debugfs_mount->mnt_root;

But I guess that's not a major issue since its debugfs :-) So LGTM,
Reviewed-by: Joel Fernandes (Google) <joel@...lfernandes.org>

thanks,

 - Joel

>  
>  	return 0;
> -
> -err:
> -	debugfs_remove(dbgdir);
> -
> -	return -ENOMEM;
>  }
>  __initcall(debug_objects_init_debugfs);
>  
> -- 
> 2.22.0
>