mmc: queue: amend buffer swap for non-blocking transfer

In case both 'req' and 'mq->mqrq_prev->req' are null, there is no request
to be processed. That means there is no need to switch buffer.
Switching buffer is required only after finishing 'issue_fn'.
Signed-off-by: NSeungwon Jeon <tgih.jun@samsung.com>
Reviewed-by: NPer Forlin <per.forlin@stericsson.com>
Tested-by: NJohan Rudholm <johan.rudholm@stericsson.com>
Signed-off-by: NChris Ball <cjb@laptop.org>

drivers/mmc/card/queue.c

@@ -68,6 +68,16 @@ static int mmc_queue_thread(void *d)
 		if (req || mq->mqrq_prev->req) {
 			set_current_state(TASK_RUNNING);
 			mq->issue_fn(mq, req);
+
+			/*
+			 * Current request becomes previous request
+			 * and vice versa.
+			 */
+			mq->mqrq_prev->brq.mrq.data = NULL;
+			mq->mqrq_prev->req = NULL;
+			tmp = mq->mqrq_prev;
+			mq->mqrq_prev = mq->mqrq_cur;
+			mq->mqrq_cur = tmp;
 		} else {
 			if (kthread_should_stop()) {
 				set_current_state(TASK_RUNNING);
@@ -77,13 +87,6 @@ static int mmc_queue_thread(void *d)
 			schedule();
 			down(&mq->thread_sem);
 		}
-
-		/* Current request becomes previous request and vice versa. */
-		mq->mqrq_prev->brq.mrq.data = NULL;
-		mq->mqrq_prev->req = NULL;
-		tmp = mq->mqrq_prev;
-		mq->mqrq_prev = mq->mqrq_cur;
-		mq->mqrq_cur = tmp;
 	} while (1);
 	up(&mq->thread_sem);