The following commit has been merged in the linux branch: commit 48e025e63ac908ed6ec5394a294f4ecd510a7476 Author: Corrado Zoccolo czoccolo@gmail.com Date: Mon Oct 5 08:49:23 2009 +0200

cfq-iosched: fix possible problem with jiffies wraparound

The RR service tree is indexed by a key that is relative to current jiffies. This can cause problems on jiffies wraparound.

The patch fixes it using time_before comparison, and changing the add_front path to use a relative number, too.

Signed-off-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 e7f9e4e..ae14cba 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -512,8 +512,11 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq, rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies; rb_key += cfqq->slice_resid; cfqq->slice_resid = 0; - } else - rb_key = 0; + } else { + rb_key = -HZ; + __cfqq = cfq_rb_first(&cfqd->service_tree); + rb_key += __cfqq ? __cfqq->rb_key : jiffies; + }

if (!RB_EMPTY_NODE(&cfqq->rb_node)) { /* @@ -547,7 +550,7 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq, n = &(*p)->rb_left; else if (cfq_class_idle(cfqq) > cfq_class_idle(__cfqq)) n = &(*p)->rb_right; - else if (rb_key < __cfqq->rb_key) + else if (time_before(rb_key, __cfqq->rb_key)) n = &(*p)->rb_left; else n = &(*p)->rb_right;