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SubjectRe: [PATCH] cfq-iosched: fix slice_left calculation
On Thu, Nov 10 2005, Tejun Heo wrote:
> When cfq slice expires, remainder of slice is calculated and stored in
> cfqq->slice_left. Current code calculates the opposite of remainder -
> how many jiffies the cfqq has used past slice end. This patch fixes
> the bug.
>
> Signed-off-by: Tejun Heo <htejun@gmail.com>
>
> diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
> --- a/block/cfq-iosched.c
> +++ b/block/cfq-iosched.c
> @@ -861,8 +861,8 @@ __cfq_slice_expired(struct cfq_data *cfq
> * store what was left of this slice, if the queue idled out
> * or was preempted
> */
> - if (time_after(now, cfqq->slice_end))
> - cfqq->slice_left = now - cfqq->slice_end;
> + if (time_after(cfqq->slice_end, now))
> + cfqq->slice_left = cfqq->slice_end - now;
> else
> cfqq->slice_left = 0;

That looks more correct, good spotting. Applied.

--
Jens Axboe

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