[PATCHv2] nvme: allow to re-attach namespaces after all paths are down

@@ -546,6 +546,9 @@ static void nvme_free_ns_head(struct kref *ref)
 	struct nvme_ns_head *head =
 		container_of(ref, struct nvme_ns_head, ref);
 
+	mutex_lock(&head->subsys->lock);
+	list_del_init(&head->entry);
+	mutex_unlock(&head->subsys->lock);
 	nvme_mpath_remove_disk(head);
 	ida_simple_remove(&head->subsys->ns_ida, head->instance);
 	cleanup_srcu_struct(&head->srcu);

@@ -3549,7 +3552,7 @@ static struct nvme_ns_head *nvme_alloc_ns_head(struct nvme_ctrl *ctrl,
 		goto out_ida_remove;
 	head->subsys = ctrl->subsys;
 	head->ns_id = nsid;
-	head->ids = *ids;
+	memcpy(&head->ids, ids, sizeof(sturct nvme_ns_ids));
 	kref_init(&head->ref);
 
 	ret = __nvme_check_ids(ctrl->subsys, head);

@@ -3605,15 +3608,23 @@ static int nvme_init_ns_head(struct nvme_ns *ns, unsigned nsid,
 		head->shared = is_shared;
 	} else {
 		ret = -EINVAL;
+		/*
+		 * If multipath is enabled we might hit an ns head with no
+		 * paths, but that doesn't indicate it's a shared namespace.
+		 */
+		if (nvme_ns_head_multipath(head) &&
+		    list_empty(&head->list))
+			goto check_ids;
 		if (!is_shared || !head->shared) {
 			dev_err(ctrl->device,
 				"Duplicate unshared namespace %d\n", nsid);
 			goto out_put_ns_head;
 		}
+check_ids:
 		if (!nvme_ns_ids_equal(&head->ids, ids)) {
 			dev_err(ctrl->device,
 				"IDs don't match for shared namespace %d\n",
-					nsid);
+				nsid);
 			goto out_put_ns_head;
 		}
 	}

@@ -3764,8 +3775,6 @@ static void nvme_ns_remove(struct nvme_ns *ns)
 
 	mutex_lock(&ns->ctrl->subsys->lock);
 	list_del_rcu(&ns->siblings);
-	if (list_empty(&ns->head->list))
-		list_del_init(&ns->head->entry);
 	mutex_unlock(&ns->ctrl->subsys->lock);
 
 	synchronize_rcu(); /* guarantee not available in head->list */