The following commit has been merged in the linux branch: commit b9c8946b192397394a0ccd4fcecb31bc060f79f8 Author: Jens Axboe jens.axboe@oracle.com Date: Tue Oct 6 20:53:44 2009 +0200

cfq-iosched: fix the slice residual sign

We should subtract the slice residual from the rb tree key, since a negative residual count indicates that the cfqq overran its slice the last time. Hence we want to add the overrun time, to position it a bit further away in the service tree.

Reported-by: Corrado Zoccolo czoccolo@gmail.com Signed-off-by: Jens Axboe jens.axboe@oracle.com

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index 5c3cee9..4ab33d8 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -507,8 +507,14 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq, } else rb_key += jiffies; } else if (!add_front) { + /* + * Get our rb key offset. Subtract any residual slice + * value carried from last service. A negative resid + * count indicates slice overrun, and this should position + * the next service time further away in the tree. + */ rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies; - rb_key += cfqq->slice_resid; + rb_key -= cfqq->slice_resid; cfqq->slice_resid = 0; } else { rb_key = -HZ;