nvmet-fc: add transport discovery change event callback support

This patch adds support for the nvmet discovery_change transport op.
In turn, the transport adds it's own LLDD api callback discovery_event
op to request the LLDD to generate an RSCN for the discovery change.

Signed-off-by: James Smart <jsmart2021@gmail.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Arun Easi <aeasi@marvell.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/target/fc.c

@@ -2549,6 +2549,16 @@ nvmet_fc_remove_port(struct nvmet_port *port)
 	kfree(pe);
 }
 
+static void
+nvmet_fc_discovery_chg(struct nvmet_port *port)
+{
+	struct nvmet_fc_port_entry *pe = port->priv;
+	struct nvmet_fc_tgtport *tgtport = pe->tgtport;
+
+	if (tgtport && tgtport->ops->discovery_event)
+		tgtport->ops->discovery_event(&tgtport->fc_target_port);
+}
+
 static const struct nvmet_fabrics_ops nvmet_fc_tgt_fcp_ops = {
 	.owner			= THIS_MODULE,
 	.type			= NVMF_TRTYPE_FC,
@@ -2557,6 +2567,7 @@ static const struct nvmet_fabrics_ops nvmet_fc_tgt_fcp_ops = {
 	.remove_port		= nvmet_fc_remove_port,
 	.queue_response		= nvmet_fc_fcp_nvme_cmd_done,
 	.delete_ctrl		= nvmet_fc_delete_ctrl,
+	.discovery_chg		= nvmet_fc_discovery_chg,
 };
 
 static int __init nvmet_fc_init_module(void)