virtio-blk: fallback to draining the queue if barrier ops are not supported

Commit Message

Avi Kivity Oct. 14, 2009, 12:03 p.m. UTC

None

Patch

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 43f1938..2627cc3 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -354,12 +354,16 @@  static int __devinit virtblk_probe(struct virtio_device *vdev)
 	vblk->disk->driverfs_dev = &vdev->dev;
 	index++;
 
-	/* If barriers are supported, tell block layer that queue is ordered */
+	/* If barriers are supported, tell block layer that queue is ordered;
+	 * otherwise just drain the queue.
+	 */
 	if (virtio_has_feature(vdev, VIRTIO_BLK_F_FLUSH))
 		blk_queue_ordered(vblk->disk->queue, QUEUE_ORDERED_DRAIN_FLUSH,
 				  virtblk_prepare_flush);
 	else if (virtio_has_feature(vdev, VIRTIO_BLK_F_BARRIER))
 		blk_queue_ordered(vblk->disk->queue, QUEUE_ORDERED_TAG, NULL);
+	else
+		blk_queue_ordered(vblk->disk->queue, QUEUE_ORDERED_DRAIN, NULL);
 
 	/* If disk is read-only in the host, the guest should obey */
 	if (virtio_has_feature(vdev, VIRTIO_BLK_F_RO))