Re: [PATCH 3/5] writeback: dirty rate control

[Peter Zijlstra]

On Sat, 2011-08-06 at 16:44 +0800, Wu Fengguang wrote:

> +       pos_bw = bw * pos_ratio >> BANDWIDTH_CALC_SHIFT;
> +       pos_bw++;  /* this avoids bdi->dirty_ratelimit get stuck in 0 */
> +

> +       pos_ratio *= bdi->avg_write_bandwidth;
> +       do_div(pos_ratio, dirty_bw | 1);
> +       ref_bw = bw * pos_ratio >> BANDWIDTH_CALC_SHIFT; 

when written out that results in:

           bw * pos_ratio * bdi->avg_write_bandwidth
  ref_bw = -----------------------------------------
                         dirty_bw

which would suggest you write it like:

  ref_bw = div_u64((u64)pos_bw * bdi->avg_write_bandwidth, dirty_bw | 1);

since pos_bw is already bw * pos_ratio per the above.

Or am I missing something?
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