[PATCH 1/5] nvmet: call transport on subsystem add and delete

[jsmart2021@gmail.com (James Smart)]

A transport may have a transport-specific mechanism that can signal
when discovery controller content has changed and request a host
to reconnect to the discovery controller.

FC is such a transport. RSCNs may be generated by the FC port with
the discovery server, with the RSCNs then broadcast to the FC-NVME
hosts. A host, upon receiving the RSCN, would validate connectivity
then initiate a discovery controller rescan, allowing new subsystems
to be connected to or updating subsystem connectivity tables.

Modify the subsystem link/unlink routines to always call a new
nvmet_port_subsystem_chg() routine whenever a new subsystem is
linked to a port or removed from a port.

The nvmet_port_subsystem_chg() routine will look to see if the
transport supports a discovery change callback, and if so, calls
the callback.

Signed-off-by: James Smart <james.smart at broadcom.com>
---
 drivers/nvme/target/configfs.c |  2 ++
 drivers/nvme/target/core.c     | 10 ++++++++++
 drivers/nvme/target/nvmet.h    |  2 ++
 3 files changed, 14 insertions(+)

diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c
index b6aeb1d70951..38adcd7eafb1 100644
--- a/drivers/nvme/target/configfs.c
+++ b/drivers/nvme/target/configfs.c
@@ -503,6 +503,7 @@ static int nvmet_port_subsys_allow_link(struct config_item *parent,
 	list_add_tail(&link->entry, &port->subsystems);
 	nvmet_genctr++;
 	up_write(&nvmet_config_sem);
+	nvmet_port_subsystem_chg(port);
 	return 0;
 
 out_free_link:
@@ -529,6 +530,7 @@ static void nvmet_port_subsys_drop_link(struct config_item *parent,
 found:
 	list_del(&p->entry);
 	nvmet_genctr++;
+	nvmet_port_subsystem_chg(port);
 	if (list_empty(&port->subsystems))
 		nvmet_disable_port(port);
 	up_write(&nvmet_config_sem);
diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
index da088293eafc..f70d900774d0 100644
--- a/drivers/nvme/target/core.c
+++ b/drivers/nvme/target/core.c
@@ -206,6 +206,16 @@ void nvmet_disable_port(struct nvmet_port *port)
 	module_put(ops->owner);
 }
 
+void nvmet_port_subsystem_chg(struct nvmet_port *port)
+{
+	struct nvmet_fabrics_ops *ops;
+
+	ops = nvmet_transports[port->disc_addr.trtype];
+
+	if (ops->discov_chg)
+		ops->discov_chg(port);
+}
+
 static void nvmet_keep_alive_timer(struct work_struct *work)
 {
 	struct nvmet_ctrl *ctrl = container_of(to_delayed_work(work),
diff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h
index e342f02845c1..87c7f6e84694 100644
--- a/drivers/nvme/target/nvmet.h
+++ b/drivers/nvme/target/nvmet.h
@@ -209,6 +209,7 @@ struct nvmet_fabrics_ops {
 	int (*add_port)(struct nvmet_port *port);
 	void (*remove_port)(struct nvmet_port *port);
 	void (*delete_ctrl)(struct nvmet_ctrl *ctrl);
+	void (*discov_chg)(struct nvmet_port *port);
 };
 
 #define NVMET_MAX_INLINE_BIOVEC	8
@@ -302,6 +303,7 @@ void nvmet_unregister_transport(struct nvmet_fabrics_ops *ops);
 
 int nvmet_enable_port(struct nvmet_port *port);
 void nvmet_disable_port(struct nvmet_port *port);
+void nvmet_port_subsystem_chg(struct nvmet_port *port);
 
 void nvmet_referral_enable(struct nvmet_port *parent, struct nvmet_port *port);
 void nvmet_referral_disable(struct nvmet_port *port);
-- 
2.13.1