blk-mq: mq plug list breakage

We switched to plug mq_list for mq, but some code are still using old list.
Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-core.c

@@ -1401,13 +1401,19 @@ bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
 	struct blk_plug *plug;
 	struct request *rq;
 	bool ret = false;
+	struct list_head *plug_list;
 
 	plug = current->plug;
 	if (!plug)
 		goto out;
 	*request_count = 0;
 
-	list_for_each_entry_reverse(rq, &plug->list, queuelist) {
+	if (q->mq_ops)
+		plug_list = &plug->mq_list;
+	else
+		plug_list = &plug->list;
+
+	list_for_each_entry_reverse(rq, plug_list, queuelist) {
 		int el_ret;
 
 		if (rq->q == q)

block/blk-mq.c

@@ -950,7 +950,7 @@ static void blk_mq_make_request(struct request_queue *q, struct bio *bio)
 
 		if (plug) {
 			blk_mq_bio_to_request(rq, bio);
-			if (list_empty(&plug->list))
+			if (list_empty(&plug->mq_list))
 				trace_block_plug(q);
 			else if (request_count >= BLK_MAX_REQUEST_COUNT) {
 				blk_flush_plug_list(plug, false);