NVMe: Set TASK_INTERRUPTIBLE before processing queues

The kthread has two tasks; handling timeouts (for which it runs once per
second), and submitting queued BIOs.  If a BIO happens to be queued after
the thread has processed the queue but before it calls schedule_timeout(),
the thread will sleep for a second before submitting it, which can cause
performance problems in some rare cases (that will become more common in
a subsequent patch).
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Tested-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>

drivers/block/nvme-core.c

@@ -1291,7 +1291,7 @@ static int nvme_kthread(void *data)
 	struct nvme_dev *dev;
 
 	while (!kthread_should_stop()) {
-		__set_current_state(TASK_RUNNING);
+		set_current_state(TASK_INTERRUPTIBLE);
 		spin_lock(&dev_list_lock);
 		list_for_each_entry(dev, &dev_list, node) {
 			int i;
@@ -1308,7 +1308,6 @@ static int nvme_kthread(void *data)
 			}
 		}
 		spin_unlock(&dev_list_lock);
-		set_current_state(TASK_INTERRUPTIBLE);
 		schedule_timeout(round_jiffies_relative(HZ));
 	}
 	return 0;