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

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Message-ID: <1400604342.26709.2.camel@joe-AO725>
Date:	Tue, 20 May 2014 09:45:42 -0700
From:	Joe Perches <joe@...ches.com>
To:	Fabian Frederick <fabf@...net.be>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	Sebastian Ott <sebott@...ux.vnet.ibm.com>,
	akpm <akpm@...ux-foundation.org>
Subject: Re: [PATCH 1/1] drivers/s390/cio/qdio_main.c: replace shift loop by
 ilog2

On Tue, 2014-05-20 at 18:37 +0200, Fabian Frederick wrote:
> This is untested.
[]
> diff --git 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);

What guarantees count > 0 here?

count may be better unsigned.

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