Subject: Re: [PATCH v3 01/10] mtd: powernv_flash: Use WARN_ON_ONCE() rather than BUG_ON()

From: Cyril Bur <[email-masked]>
Date: Tue, 18 Jul 2017 10:27:19 +1000

On Mon, 2017-07-17 at 13:33 +0200, Frans Klaver wrote:
> On Wed, Jul 12, 2017 at 6:22 AM, Cyril Bur <[email-masked]> wrote:
> > BUG_ON() should be reserved in situations where we can not longer
> > guarantee the integrity of the system. In the case where
> > powernv_flash_async_op() receives an impossible op, we can still
> > guarantee the integrity of the system.
> > 
> > Signed-off-by: Cyril Bur <[email-masked]>
> > ---
> >  drivers/mtd/devices/powernv_flash.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/mtd/devices/powernv_flash.c b/drivers/mtd/devices/powernv_flash.c
> > index f5396f26ddb4..a9a20c00687c 100644
> > --- a/drivers/mtd/devices/powernv_flash.c
> > +++ b/drivers/mtd/devices/powernv_flash.c
> > @@ -78,7 +78,8 @@ static int powernv_flash_async_op(struct mtd_info *mtd, enum flash_op op,
> >                 rc = opal_flash_erase(info->id, offset, len, token);
> >                 break;
> >         default:
> > -               BUG_ON(1);
> > +               WARN_ON_ONCE(1);
> > +               return -EIO;
> 
> Based on the fact that all three values in enum flash_op are handled,
> I would go as far as stating that the default lemma adds no value and
> can be removed.
> 

The way I see it is that it isn't doing any harm being there and in
cases of future programmer error or during corruption events, that
WARN_ON might prove useful.

> Frans