nvmet: make sure discovery change log event is protected

Generation counter is protected by nvmet_config_sem. Make sure the
callers that call functions that might change it, are calling it
properly.

Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Reviewed-by: Israel Rukshin <israelr@nvidia.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/target/discovery.c

@@ -69,6 +69,7 @@ void nvmet_subsys_disc_changed(struct nvmet_subsys *subsys,
 	struct nvmet_port *port;
 	struct nvmet_subsys_link *s;
 
+	lockdep_assert_held(&nvmet_config_sem);
 	nvmet_genctr++;
 
 	list_for_each_entry(port, nvmet_ports, global_entry)