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Subject[PATCH 1/1] Correct sorting problem in cfq_service_tree_add
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Sort order was being incorrectly calculated using just the class, this
patch includes the priority within the classes when deciding sort order.

Note: IOPRIO_CLASS_NONE classes are converted to IOPRIO_CLASS_BE before
getting to this function, hence the WARN_ON in the added function
cfq_class_prio.

Signed-off-by: Alan D. Brunelle <alan.brunelle@hp.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
---
block/cfq-iosched.c | 27 ++++++++++++++++-----------
1 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index aa1e953..7b9ca4d 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -226,6 +226,12 @@ CFQ_CFQQ_FNS(coop);
CFQ_CFQQ_FNS(coop_preempt);
#undef CFQ_CFQQ_FNS

+static inline int cfq_class_prio(struct cfq_queue *cfqq)
+{
+ WARN_ON(cfqq->ioprio_class == IOPRIO_CLASS_NONE);
+ return IOPRIO_PRIO_VALUE(cfqq->ioprio_class, cfqq->ioprio);
+}
+
#define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \
blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args)
#define cfq_log(cfqd, fmt, args...) \
@@ -536,30 +542,29 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
p = &cfqd->service_tree.rb.rb_node;
while (*p) {
struct rb_node **n;
+ int cfqq_prio, __cfqq_prio;

parent = *p;
__cfqq = rb_entry(parent, struct cfq_queue, rb_node);

+ cfqq_prio = cfq_class_prio(cfqq);
+ __cfqq_prio = cfq_class_prio(__cfqq);
+
/*
* sort RT queues first, we always want to give
* preference to them. IDLE queues goes to the back.
* after that, sort on the next service time.
+ * (Lower priority values represent higher priorities.)
*/
- if (cfq_class_rt(cfqq) > cfq_class_rt(__cfqq))
+ if (cfqq_prio < __cfqq_prio)
n = &(*p)->rb_left;
- else if (cfq_class_rt(cfqq) < cfq_class_rt(__cfqq))
- n = &(*p)->rb_right;
- else if (cfq_class_idle(cfqq) < cfq_class_idle(__cfqq))
+ else if (cfqq_prio == __cfqq_prio &&
+ time_before(rb_key, __cfqq->rb_key))
n = &(*p)->rb_left;
- else if (cfq_class_idle(cfqq) > cfq_class_idle(__cfqq))
- n = &(*p)->rb_right;
- else if (time_before(rb_key, __cfqq->rb_key))
- n = &(*p)->rb_left;
- else
+ else {
n = &(*p)->rb_right;
-
- if (n == &(*p)->rb_right)
left = 0;
+ }

p = n;
}
--
1.6.3.3




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