Reinstate the old BFS schedule flush plug behaviour after locking in
schedule().

-ck

---
 kernel/sched/bfs.c |   30 ++++++++++++++----------------
 1 file changed, 14 insertions(+), 16 deletions(-)

Index: linux-4.1.4-ck1/kernel/sched/bfs.c
===================================================================
--- linux-4.1.4-ck1.orig/kernel/sched/bfs.c	2015-08-06 09:31:07.317487340 +1000
+++ linux-4.1.4-ck1/kernel/sched/bfs.c	2015-08-06 09:38:39.367987643 +1000
@@ -3368,10 +3368,12 @@ static void __sched __schedule(void)
 {
 	struct task_struct *prev, *next, *idle;
 	unsigned long *switch_count;
-	bool deactivate = false;
+	bool deactivate;
 	struct rq *rq;
 	int cpu;
 
+need_resched:
+	deactivate = false;
 	preempt_disable();
 	cpu = smp_processor_id();
 	rq = cpu_rq(cpu);
@@ -3418,6 +3420,17 @@ static void __sched __schedule(void)
 		switch_count = &prev->nvcsw;
 	}
 
+	/*
+	 * If we are going to sleep and we have plugged IO queued, make
+	 * sure to submit it to avoid deadlocks.
+	 */
+	if (unlikely(deactivate && blk_needs_flush_plug(prev))) {
+		grq_unlock_irq();
+		preempt_enable_no_resched();
+		blk_schedule_flush_plug(prev);
+		goto need_resched;
+	}
+
 	update_clocks(rq);
 	update_cpu_clock_switch(rq, prev);
 	if (rq->clock - rq->last_tick > HALF_JIFFY_NS)
@@ -3508,23 +3521,8 @@ rerun_prev_unlocked:
 	sched_preempt_enable_no_resched();
 }
 
-static inline void sched_submit_work(struct task_struct *tsk)
-{
-	if (!tsk->state || tsk_is_pi_blocked(tsk))
-		return;
-	/*
-	 * If we are going to sleep and we have plugged IO queued,
-	 * make sure to submit it to avoid deadlocks.
-	 */
-	if (blk_needs_flush_plug(tsk))
-		blk_schedule_flush_plug(tsk);
-}
-
 asmlinkage __visible void __sched schedule(void)
 {
-	struct task_struct *tsk = current;
-
-	sched_submit_work(tsk);
 	do {
 		__schedule();
 	} while (need_resched());