linux-kernel - Re: [PATCH 2/2] debugfs: log errors when something goes wrong

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Date:   Wed, 3 Jul 2019 16:53:57 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Mark Brown <broonie@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] debugfs: log errors when something goes wrong

On Wed, Jul 03, 2019 at 11:35:50AM +0200, Takashi Iwai wrote:
> On Wed, 03 Jul 2019 11:32:33 +0200,
> Greg Kroah-Hartman wrote:
> > 
> > On Wed, Jul 03, 2019 at 11:10:44AM +0200, Rafael J. Wysocki wrote:
> > > On Wed, Jul 3, 2019 at 9:17 AM Greg Kroah-Hartman
> > > <gregkh@...uxfoundation.org> wrote:
> > > >
> > > > As it is not recommended that debugfs calls be checked, it was pointed
> > > > out that major errors should still be logged somewhere so that
> > > > developers and users have a chance to figure out what went wrong.  To
> > > > help with this, error logging has been added to the debugfs core so that
> > > > it is not needed to be present in every individual file that calls
> > > > debugfs.
> > > >
> > > > Reported-by: Mark Brown <broonie@...nel.org>
> > > > Reported-by: Takashi Iwai <tiwai@...e.de>
> > > > Cc: "Rafael J. Wysocki" <rafael@...nel.org>
> > > > Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > > 
> > > Generally speaking
> > > 
> > > Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > > 
> > > > ---
> > > >  fs/debugfs/inode.c | 25 ++++++++++++++++++++-----
> > > >  1 file changed, 20 insertions(+), 5 deletions(-)
> > > >
> > > > diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
> > > > index f04c8475d9a1..7f43c8acfcbf 100644
> > > > --- a/fs/debugfs/inode.c
> > > > +++ b/fs/debugfs/inode.c
> > > > @@ -2,8 +2,9 @@
> > > >  /*
> > > >   *  inode.c - part of debugfs, a tiny little debug file system
> > > >   *
> > > > - *  Copyright (C) 2004 Greg Kroah-Hartman <greg@...ah.com>
> > > > + *  Copyright (C) 2004,2019 Greg Kroah-Hartman <greg@...ah.com>
> > > >   *  Copyright (C) 2004 IBM Inc.
> > > > + *  Copyright (C) 2019 Linux Foundation <gregkh@...uxfoundation.org>
> > > >   *
> > > >   *  debugfs is for people to use instead of /proc or /sys.
> > > >   *  See ./Documentation/core-api/kernel-api.rst for more details.
> > > > @@ -294,8 +295,10 @@ static struct dentry *start_creating(const char *name, struct dentry *parent)
> > > >
> > > >         error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
> > > >                               &debugfs_mount_count);
> > > > -       if (error)
> > > > +       if (error) {
> > > > +               pr_err("Unable to pin filesystem for file '%s'\n", name);
> > > 
> > > But I'm not sure about the log level here.  Particularly, why would
> > > pr_info() not work?
> > 
> > It could, but it is an error in that debugfs didn't do what was asked of
> > it.  I really don't care either way, the odds of anyone ever seeing this
> > message is almost none :)
> 
> Yes, that's an obvious error and I see no big reason to hide it.
> 
> For both:
>   Reviewed-by: Takashi Iwai <tiwai@...e.de>

Thanks all for the review, I'll go apply these to my tree now.

greg k-h