+static int negotiate_mq(struct blkfront_info *info)
+{
+ unsigned int backend_max_queues = 0;
+ int err;
+ unsigned int i;
+
+ BUG_ON(info->nr_rings);
+
+ /* Check if backend supports multiple queues. */
+ err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
+ "multi-queue-max-queues", "%u", &backend_max_queues);
+ if (err < 0)
+ backend_max_queues = 1;
+
+ info->nr_rings = min(backend_max_queues, xen_blkif_max_queues);
+ /* We need at least one ring. */
+ if (!info->nr_rings)
+ info->nr_rings = 1;
+
+ info->rinfo = kzalloc(sizeof(struct blkfront_ring_info) * info->nr_rings, GFP_KERNEL);
+ if (!info->rinfo) {
+ xenbus_dev_fatal(info->xbdev, -ENOMEM, "allocating ring_info structure");
+ return -ENOMEM;
+ }
+
+ for (i = 0; i < info->nr_rings; i++) {
+ struct blkfront_ring_info *rinfo;
+
+ rinfo = &info->rinfo[i];
+ INIT_LIST_HEAD(&rinfo->indirect_pages);
+ INIT_LIST_HEAD(&rinfo->grants);
+ rinfo->dev_info = info;
+ INIT_WORK(&rinfo->work, blkif_restart_queue);
+ spin_lock_init(&rinfo->ring_lock);
+ }
+ return 0;
+}