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

[Hannes Reinecke]

We should only remove the ns head from the list of heads per
subsystem if the reference count drops to zero. Removing it
at the start of nvme_ns_remove() will prevent us from reattaching
the namespace to the correct ns head once a path becomes available
again.

Signed-off-by: Hannes Reinecke <hare at suse.de>
---
 drivers/nvme/host/core.c | 33 ++++++++++++++++++++++-----------
 1 file changed, 22 insertions(+), 11 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 762125f2905f..08ff0fc01f9e 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -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);
@@ -3605,16 +3608,26 @@ static int nvme_init_ns_head(struct nvme_ns *ns, unsigned nsid,
 		head->shared = is_shared;
 	} else {
 		ret = -EINVAL;
-		if (!is_shared || !head->shared) {
-			dev_err(ctrl->device,
-				"Duplicate unshared namespace %d\n", nsid);
-			goto out_put_ns_head;
-		}
-		if (!nvme_ns_ids_equal(&head->ids, ids)) {
-			dev_err(ctrl->device,
-				"IDs don't match for shared namespace %d\n",
+		/*
+		 * 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)) {
+			if (!is_shared || !head->shared) {
+				dev_err(ctrl->device,
+					"Duplicate unshared namespace %d\n", nsid);
+				goto out_put_ns_head;
+			}
+			if (!nvme_ns_ids_equal(&head->ids, ids)) {
+				dev_err(ctrl->device,
+					"IDs don't match for shared namespace %d\n",
 					nsid);
-			goto out_put_ns_head;
+				goto out_put_ns_head;
+			}
+		} else {
+			/* But the ids might have changed, so reset them */
+			head->ids = *ids;
 		}
 	}
 
@@ -3764,8 +3777,6 @@ 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 */
-- 
2.26.2