linux-kernel - Re: [PATCH 2/2] debugfs: make return value of all debugfs helpers consistent

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Date:   Mon, 15 Apr 2019 16:29:59 -0700
From:   "Life is hard, and then you die" <ronald@...ovation.ch>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Jonathan Corbet <corbet@....net>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] debugfs: make return value of all debugfs helpers
 consistent


  Hi Greg,

On Mon, Apr 15, 2019 at 10:48:44AM +0200, Greg Kroah-Hartman wrote:
> On Mon, Apr 15, 2019 at 01:25:06AM -0700, Ronald Tschalär wrote:
> > Since commit ff9fb72bc077 ("debugfs: return error values, not NULL")
> > almost all the debugfs helpers have stopped returning NULL. The lone
> > holdeout was debugfs_create_u32_array(). So fix that.
> > 
> > Signed-off-by: Ronald Tschalär <ronald@...ovation.ch>
> > ---
> >  fs/debugfs/file.c | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> > 
> > diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
> > index ddd708b09fa1..bb706d073782 100644
> > --- a/fs/debugfs/file.c
> > +++ b/fs/debugfs/file.c
> > @@ -999,8 +999,8 @@ static const struct file_operations u32_array_fops = {
> >   * Once array is created its size can not be changed.
> >   *
> >   * The function returns a pointer to dentry on success. If an error occurs,
> > - * %ERR_PTR(-ERROR) or NULL will be returned. If debugfs is not enabled in
> > - * the kernel, the value %ERR_PTR(-ENODEV) will be returned.
> > + * %ERR_PTR(-ERROR) will be returned. If debugfs is not enabled in the kernel,
> > + * the value %ERR_PTR(-ENODEV) will be returned.
> >   */
> >  struct dentry *debugfs_create_u32_array(const char *name, umode_t mode,
> >  					    struct dentry *parent,
> > @@ -1009,7 +1009,7 @@ struct dentry *debugfs_create_u32_array(const char *name, umode_t mode,
> >  	struct array_data *data = kmalloc(sizeof(*data), GFP_KERNEL);
> >  
> >  	if (data == NULL)
> > -		return NULL;
> > +		return ERR_PTR(-ENOMEM);
> >  
> >  	data->array = array;
> >  	data->elements = elements;
> 
> There is only one caller of this function in the kernel now, and it does
> not even care about the return value at all, so we should just remove
> the return value entirely as that's the easiest and best thing to do
> here.

Interesting argument: since this is a helper/library function, and
therefore potentially used in the future by others, it seems to me
that consistency with the other functions and providing error feedback
would be important.

> I was going to start doing this slowly over time, but as you are
> touching the function now, might as well do it here :)

Are you saying the plan is to make all these helpers return void?


  Cheers,

  Ronald