Re: [PATCH 8/9] nvme: implement multipath access to nvme subsystems

[Sagi Grimberg]

+static const struct block_device_operations nvme_subsys_ops = {
+       .owner          = THIS_MODULE,
+};

Nit - maybe better to name this nvme_ns_head_ops

+       ret = -ENOMEM;
+       q = blk_alloc_queue_node(GFP_KERNEL, NUMA_NO_NODE);
+       if (!q)
+               goto out_free_head;
+       q->queuedata = head;
+       blk_queue_make_request(q, nvme_make_request);
+       queue_flag_set_unlocked(QUEUE_FLAG_NONROT, q);
+       /* set to a default value for 512 until disk is validated */
+       blk_queue_logical_block_size(q, 512);
+       nvme_set_queue_limits(ctrl, q);
+
+       head->disk = alloc_disk(0);
+       if (!head->disk)
+               goto out_cleanup_queue;
+       head->disk->fops = &nvme_subsys_ops;
+       head->disk->private_data = head;
+       head->disk->queue = q;
+       head->disk->flags = GENHD_FL_EXT_DEVT;
+       sprintf(head->disk->disk_name, "nvm-sub%dn%d",
+                       ctrl->subsys->instance, nsid);

Did we end up in agreement on nvmsXnY?

@@ -2669,8 +2905,10 @@ static void nvme_ns_remove(struct nvme_ns *ns)
        }

mutex_lock(&ns->ctrl->subsys->lock);

-       if (head)
+       if (head) {
+               rcu_assign_pointer(head->current_path, NULL);

Doesn't this assignment need to happen only when the ns *is* the
current_path?