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

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Message-ID: <20190612171026.GB6986@kroah.com>
Date:   Wed, 12 Jun 2019 19:10:26 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Joel Fernandes <joel@...lfernandes.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 12:58:19PM -0400, Joel Fernandes wrote:
> 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.

Yes, but dbgdir can not be NULL.

> 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;

Yes, but debugfs_create_dir() will never return NULL.

> But I guess that's not a major issue since its debugfs :-) So LGTM,

Yup!

> Reviewed-by: Joel Fernandes (Google) <joel@...lfernandes.org>

thanks for the review.

greg k-h