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

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Message-Id: <20190123171000.b1cbc9e1b52251bdd78b2338@kernel.org>
Date:   Wed, 23 Jan 2019 17:10:00 +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>
Subject: Re: [PATCH] kprobes: no need to check return value of
 debugfs_create functions

On Wed, 23 Jan 2019 07:54:22 +0100
Greg Kroah-Hartman <gregkh@...uxfoundation.org> wrote:

> 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.

Got it! Thanks!

Acked-by: Masami Hiramatsu <mhiramat@...nel.org>




> 
> thanks,
> 
> greg k-h


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