cfq-iosched: make io priorities inherit CPU scheduling class as well as nice

We currently set all processes to the best-effort scheduling class,
regardless of what CPU scheduling class they belong to. Improve that
so that we correctly track idle and rt scheduling classes as well.

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

1 files changed, 14 insertions, 0 deletions

diff --git a/include/linux/ioprio.h b/include/linux/ioprio.h
index 2a3bb1b..f98a656 100644
--- a/include/linux/ioprio.h
+++ b/include/linux/ioprio.h
@@ -68,6 +68,20 @@ static inline int task_nice_ioprio(struct task_struct *task)
 }
 
 /*
+ * This is for the case where the task hasn't asked for a specific IO class.
+ * Check for idle and rt task process, and return appropriate IO class.
+ */
+static inline int task_nice_ioclass(struct task_struct *task)
+{
+	if (task->policy == SCHED_IDLE)
+		return IOPRIO_CLASS_IDLE;
+	else if (task->policy == SCHED_FIFO || task->policy == SCHED_RR)
+		return IOPRIO_CLASS_RT;
+	else
+		return IOPRIO_CLASS_BE;
+}
+
+/*
  * For inheritance, return the highest of the two given priorities
  */
 extern int ioprio_best(unsigned short aprio, unsigned short bprio);