diff --git a/block/blk-mq.c b/block/blk-mq.c
index d4d7c1caa439..927189a55575 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -361,11 +361,12 @@ static struct request *__blk_mq_alloc_request(struct blk_mq_alloc_data *data)
 
 	if (e) {
 		/*
-		 * Flush requests are special and go directly to the
+		 * Flush/passthrough requests are special and go directly to the
 		 * dispatch list. Don't include reserved tags in the
 		 * limiting, as it isn't useful.
 		 */
 		if (!op_is_flush(data->cmd_flags) &&
+		    !blk_op_is_passthrough(data->cmd_flags) &&
 		    e->type->ops.limit_depth &&
 		    !(data->flags & BLK_MQ_REQ_RESERVED))
 			e->type->ops.limit_depth(data->cmd_flags, data);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 30d2090583ad..f2e77ba97550 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -274,6 +274,12 @@ static inline bool bio_is_passthrough(struct bio *bio)
 	return blk_op_is_scsi(op) || blk_op_is_private(op);
 }
 
+static inline bool blk_op_is_passthrough(unsigned int op)
+{
+	return (blk_op_is_scsi(op & REQ_OP_MASK) ||
+			blk_op_is_private(op & REQ_OP_MASK));
+}
+
 static inline unsigned short req_get_ioprio(struct request *req)
 {
 	return req->ioprio;