virtio_blk: use blk_rq_map_kern

Similar to how SCSI and NVMe prepare passthrough requests.  This avoids
poking into request internals too much.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@fb.com>

drivers/block/virtio_blk.c

@@ -236,25 +236,23 @@ static int virtio_queue_rq(struct blk_mq_hw_ctx *hctx,
 static int virtblk_get_id(struct gendisk *disk, char *id_str)
 {
 	struct virtio_blk *vblk = disk->private_data;
+	struct request_queue *q = vblk->disk->queue;
 	struct request *req;
-	struct bio *bio;
 	int err;
 
-	bio = bio_map_kern(vblk->disk->queue, id_str, VIRTIO_BLK_ID_BYTES,
-			   GFP_KERNEL);
-	if (IS_ERR(bio))
-		return PTR_ERR(bio);
-
-	req = blk_make_request(vblk->disk->queue, bio, GFP_KERNEL);
-	if (IS_ERR(req)) {
-		bio_put(bio);
+	req = blk_get_request(q, READ, GFP_KERNEL);
+	if (IS_ERR(req))
 		return PTR_ERR(req);
-	}
-
+	blk_rq_set_block_pc(req);
 	req->cmd_type = REQ_TYPE_DRV_PRIV;
+
+	err = blk_rq_map_kern(q, req, id_str, VIRTIO_BLK_ID_BYTES, GFP_KERNEL);
+	if (err)
+		goto out;
+
 	err = blk_execute_rq(vblk->disk->queue, vblk->disk, req, false);
+out:
 	blk_put_request(req);
-
 	return err;
 }