nvme-fc: Reattach to localports on re-registration

If the LLDD resets or detaches from an fc port, the LLDD will
deregister all remoteports seen by the fc port and deregister the
localport associated with the fc port. The teardown of the localport
structure will be held off due to reference counting until all the
remoteports are removed (and they are held off until all
controllers/associations to terminated). Currently, if the fc port
is reinit/reattached and registered again as a localport it is
treated as an independent entity from the prior localport and all
prior remoteports and controllers cannot be revived. They are
created as new and separate entities.

This patch changes the localport registration to look at the known
localports that are waiting to be torndown. If they are the same port
based on wwn's, the local port is transitioned out of the teardown
state.  This allows the remote ports and controller connections to
be reestablished and resumed as long as the localport can also be
reregistered within the timeout windows.

The patch adds a new routine nvme_fc_attach_to_unreg_lport() with
the functionality and moves the lport get/put routines to avoid
forward references.

Signed-off-by: James Smart <james.smart@broadcom.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/host/fc.c

@@ -220,6 +220,90 @@ static int __nvme_fc_del_ctrl(struct nvme_fc_ctrl *);
 static void __nvme_fc_delete_hw_queue(struct nvme_fc_ctrl *,
 			struct nvme_fc_queue *, unsigned int);
 
+static void
+nvme_fc_free_lport(struct kref *ref)
+{
+	struct nvme_fc_lport *lport =
+		container_of(ref, struct nvme_fc_lport, ref);
+	unsigned long flags;
+
+	WARN_ON(lport->localport.port_state != FC_OBJSTATE_DELETED);
+	WARN_ON(!list_empty(&lport->endp_list));
+
+	/* remove from transport list */
+	spin_lock_irqsave(&nvme_fc_lock, flags);
+	list_del(&lport->port_list);
+	spin_unlock_irqrestore(&nvme_fc_lock, flags);
+
+	/* let the LLDD know we've finished tearing it down */
+	lport->ops->localport_delete(&lport->localport);
+
+	ida_simple_remove(&nvme_fc_local_port_cnt, lport->localport.port_num);
+	ida_destroy(&lport->endp_cnt);
+
+	put_device(lport->dev);
+
+	kfree(lport);
+}
+
+static void
+nvme_fc_lport_put(struct nvme_fc_lport *lport)
+{
+	kref_put(&lport->ref, nvme_fc_free_lport);
+}
+
+static int
+nvme_fc_lport_get(struct nvme_fc_lport *lport)
+{
+	return kref_get_unless_zero(&lport->ref);
+}
+
+
+static struct nvme_fc_lport *
+nvme_fc_attach_to_unreg_lport(struct nvme_fc_port_info *pinfo)
+{
+	struct nvme_fc_lport *lport;
+	unsigned long flags;
+
+	spin_lock_irqsave(&nvme_fc_lock, flags);
+
+	list_for_each_entry(lport, &nvme_fc_lport_list, port_list) {
+		if (lport->localport.node_name != pinfo->node_name ||
+		    lport->localport.port_name != pinfo->port_name)
+			continue;
+
+		if (lport->localport.port_state != FC_OBJSTATE_DELETED) {
+			lport = ERR_PTR(-EEXIST);
+			goto out_done;
+		}
+
+		if (!nvme_fc_lport_get(lport)) {
+			/*
+			 * fails if ref cnt already 0. If so,
+			 * act as if lport already deleted
+			 */
+			lport = NULL;
+			goto out_done;
+		}
+
+		/* resume the lport */
+
+		lport->localport.port_role = pinfo->port_role;
+		lport->localport.port_id = pinfo->port_id;
+		lport->localport.port_state = FC_OBJSTATE_ONLINE;
+
+		spin_unlock_irqrestore(&nvme_fc_lock, flags);
+
+		return lport;
+	}
+
+	lport = NULL;
+
+out_done:
+	spin_unlock_irqrestore(&nvme_fc_lock, flags);
+
+	return lport;
+}
 
 /**
  * nvme_fc_register_localport - transport entry point called by an
@@ -257,6 +341,28 @@ nvme_fc_register_localport(struct nvme_fc_port_info *pinfo,
 		goto out_reghost_failed;
 	}
 
+	/*
+	 * look to see if there is already a localport that had been
+	 * deregistered and in the process of waiting for all the
+	 * references to fully be removed.  If the references haven't
+	 * expired, we can simply re-enable the localport. Remoteports
+	 * and controller reconnections should resume naturally.
+	 */
+	newrec = nvme_fc_attach_to_unreg_lport(pinfo);
+
+	/* found an lport, but something about its state is bad */
+	if (IS_ERR(newrec)) {
+		ret = PTR_ERR(newrec);
+		goto out_reghost_failed;
+
+	/* found existing lport, which was resumed */
+	} else if (newrec) {
+		*portptr = &newrec->localport;
+		return 0;
+	}
+
+	/* nothing found - allocate a new localport struct */
+
 	newrec = kmalloc((sizeof(*newrec) + template->local_priv_sz),
 			 GFP_KERNEL);
 	if (!newrec) {
@@ -310,44 +416,6 @@ out_reghost_failed:
 }
 EXPORT_SYMBOL_GPL(nvme_fc_register_localport);
 
-static void
-nvme_fc_free_lport(struct kref *ref)
-{
-	struct nvme_fc_lport *lport =
-		container_of(ref, struct nvme_fc_lport, ref);
-	unsigned long flags;
-
-	WARN_ON(lport->localport.port_state != FC_OBJSTATE_DELETED);
-	WARN_ON(!list_empty(&lport->endp_list));
-
-	/* remove from transport list */
-	spin_lock_irqsave(&nvme_fc_lock, flags);
-	list_del(&lport->port_list);
-	spin_unlock_irqrestore(&nvme_fc_lock, flags);
-
-	/* let the LLDD know we've finished tearing it down */
-	lport->ops->localport_delete(&lport->localport);
-
-	ida_simple_remove(&nvme_fc_local_port_cnt, lport->localport.port_num);
-	ida_destroy(&lport->endp_cnt);
-
-	put_device(lport->dev);
-
-	kfree(lport);
-}
-
-static void
-nvme_fc_lport_put(struct nvme_fc_lport *lport)
-{
-	kref_put(&lport->ref, nvme_fc_free_lport);
-}
-
-static int
-nvme_fc_lport_get(struct nvme_fc_lport *lport)
-{
-	return kref_get_unless_zero(&lport->ref);
-}
-
 /**
  * nvme_fc_unregister_localport - transport entry point called by an
  *                              LLDD to deregister/remove a previously