linux-kernel - Re: [PATCH 1/1] drivers/s390/cio/qdio_main.c: replace shift loop by ilog2

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Message-Id: <20140602201757.66cf234bcba12078dc278eba@skynet.be>
Date:	Mon, 2 Jun 2014 20:17:57 +0200
From:	Fabian Frederick <fabf@...net.be>
To:	Sebastian Ott <sebott@...ux.vnet.ibm.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	akpm <akpm@...ux-foundation.org>
Subject: Re: [PATCH 1/1] drivers/s390/cio/qdio_main.c: replace shift loop by
 ilog2

On Mon, 2 Jun 2014 16:41:48 +0200 (CEST)
Sebastian Ott <sebott@...ux.vnet.ibm.com> wrote:

> Hello Fabian,
> 
> On Tue, 20 May 2014, Fabian Frederick wrote:
> > 
> > This is untested.
> > 
> > Cc: Sebastian Ott <sebott@...ux.vnet.ibm.com>
> > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > Signed-off-by: Fabian Frederick <fabf@...net.be>
> > ---
> >  drivers/s390/cio/qdio_main.c | 5 ++---
> >  1 file changed, 2 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/s390/cio/qdio_main.c b/drivers/s390/cio/qdio_main.c
> > index 77466c4..8bf9ec1 100644
> > --- a/drivers/s390/cio/qdio_main.c
> > +++ b/drivers/s390/cio/qdio_main.c
> > @@ -411,15 +411,14 @@ static inline void qdio_stop_polling(struct qdio_q *q)
> > 
> >  static inline void account_sbals(struct qdio_q *q, int count)
> >  {
> > -	int pos = 0;
> > +	int pos;
> > 
> >  	q->q_stats.nr_sbal_total += count;
> >  	if (count == QDIO_MAX_BUFFERS_MASK) {
> >  		q->q_stats.nr_sbals[7]++;
> >  		return;
> >  	}
> > -	while (count >>= 1)
> > -		pos++;
> > +	pos = ilog2(count);
> >  	q->q_stats.nr_sbals[pos]++;
> >  }
> > 
> > -- 
> > 1.8.4.5
> > 
> > 
> 
> Could you please resend the patch with a better description plus
> the change Joe suggested.
> 
> Thanks,
> Sebastian

Hello Sebastian,
   Conclusion of that patch/thread was that callers guarantee count to be > 0

Joe suggested to have unsigned count. Is it what you're talking about ?

Regards,
Fabian
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