mmc: queue: exclude asynchronous transfer for special request

Unlike normal r/w request, special requests(discard, flush)
is finished with a one-time issue_fn. Request change to
mqrq_prev makes unnecessary call.
Signed-off-by: NSeungwon Jeon <tgih.jun@samsung.com>
Reviewed-by: NKonstantin Dorfman <kdorfman@codeaurora.org>
Signed-off-by: NChris Ball <cjb@laptop.org>

drivers/mmc/card/queue.c

@@ -24,6 +24,8 @@
 
 #define MMC_QUEUE_SUSPENDED	(1 << 0)
 
+#define MMC_REQ_SPECIAL_MASK	(REQ_DISCARD | REQ_FLUSH)
+
 /*
  * Prepare a MMC request. This just filters out odd stuff.
  */
@@ -58,6 +60,7 @@ static int mmc_queue_thread(void *d)
 	do {
 		struct request *req = NULL;
 		struct mmc_queue_req *tmp;
+		unsigned int cmd_flags = 0;
 
 		spin_lock_irq(q->queue_lock);
 		set_current_state(TASK_INTERRUPTIBLE);
@@ -67,12 +70,19 @@ static int mmc_queue_thread(void *d)
 
 		if (req || mq->mqrq_prev->req) {
 			set_current_state(TASK_RUNNING);
+			cmd_flags = req ? req->cmd_flags : 0;
 			mq->issue_fn(mq, req);
 
 			/*
 			 * Current request becomes previous request
 			 * and vice versa.
+			 * In case of special requests, current request
+			 * has been finished. Do not assign it to previous
+			 * request.
 			 */
+			if (cmd_flags & MMC_REQ_SPECIAL_MASK)
+				mq->mqrq_cur->req = NULL;
+
 			mq->mqrq_prev->brq.mrq.data = NULL;
 			mq->mqrq_prev->req = NULL;
 			tmp = mq->mqrq_prev;