linux-kernel - Re: [RFC] debugfs: create file error handling

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Message-ID: <20070618142713.4d030a42@localhost.localdomain>
Date:	Mon, 18 Jun 2007 14:27:13 -0700
From:	Stephen Hemminger <shemminger@...ux-foundation.org>
To:	Greg KH <greg@...ah.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [RFC] debugfs: create file error handling

On Mon, 18 Jun 2007 13:57:27 -0700
Greg KH <greg@...ah.com> wrote:

> On Mon, Jun 18, 2007 at 01:41:32PM -0700, Stephen Hemminger wrote:
> > Shouldn't Debugfs file routines should either return NULL or use ERR_PTR()
> > not mixed? The following patch changes the create routines to
> > propagate return values.
> > 
> > --- a/fs/debugfs/file.c	2007-05-30 10:32:32.000000000 -0700
> > +++ b/fs/debugfs/file.c	2007-06-18 13:38:01.000000000 -0700
> > @@ -83,12 +83,11 @@ DEFINE_SIMPLE_ATTRIBUTE(fops_u8, debugfs
> >   * This function will return a pointer to a dentry if it succeeds.  This
> >   * pointer must be passed to the debugfs_remove() function when the file is
> >   * to be removed (no automatic cleanup happens if your module is unloaded,
> > - * you are responsible here.)  If an error occurs, %NULL will be returned.
> > + * you are responsible here.)
> >   *
> > - * If debugfs is not enabled in the kernel, the value -%ENODEV will be
> > - * returned.  It is not wise to check for this value, but rather, check for
> > - * %NULL or !%NULL instead as to eliminate the need for #ifdef in the calling
> > - * code.
> > + * If an error occurs, an invalid pointer will be returned, use
> > + * the function IS_ERR() to check. The error code can be extracted
> > + * with PTR_ERR().
> 
> No, you are forgetting the issue when debugfs is not enabled in the
> kernel.
> 
> The goal is not to return -ENODEV when it's not configured in, to make
> it "simpler" to handle that case.

But it makes sense to pass error values back not just: create failed
sorry!

> 
> Check the lkml archives for previous times this has come up and example
> code to use to handle the error cases properly.
> 
> I agree it isn't the "simplest" way, and if you can suggest something
> that is easier, and allow for the code to "easily" determine the option
> isn't built in that would be great.

Checking for ENODEV works fine in either case.

-- 
Stephen Hemminger <shemminger@...ux-foundation.org>
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