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

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Message-ID: <20190123065422.GA27466@kroah.com>
Date:   Wed, 23 Jan 2019 07:54:22 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Masami Hiramatsu <mhiramat@...nel.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>
Subject: Re: [PATCH] kprobes: no need to check return value of debugfs_create
 functions

On Wed, Jan 23, 2019 at 11:15:16AM +0900, Masami Hiramatsu wrote:
> 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...)

dir == NULL means the system is out of memory.  Which I'll change and
just make it return an error, so it is fine to ignore this value.

thanks,

greg k-h