cfq: async queue allocation per priority

If we have two processes with different ioprio_class, but the same
ioprio_data, their async requests will fall into the same queue. I guess
such behavior is not expected, because it's not right to put real-time
requests and best-effort requests in the same queue.

The attached patch fixes the problem by introducing additional *cfqq
fields on cfqd, pointing to per-(class,priority) async queues.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/include/linux/ioprio.h b/include/linux/ioprio.h
index 2eaa142..baf2938 100644
--- a/include/linux/ioprio.h
+++ b/include/linux/ioprio.h
@@ -53,6 +53,14 @@ static inline int task_ioprio(struct task_struct *task)
 	return IOPRIO_NORM;
 }
 
+static inline int task_ioprio_class(struct task_struct *task)
+{
+	if (ioprio_valid(task->ioprio))
+		return IOPRIO_PRIO_CLASS(task->ioprio);
+
+	return IOPRIO_CLASS_BE;
+}
+
 static inline int task_nice_ioprio(struct task_struct *task)
 {
 	return (task_nice(task) + 20) / 5;