target: Add TFO->put_session() caller for HW fabric session shutdown

This patch adds an optional target_core_fabric_ops->put_session() caller
within the existing target_put_session() code path.

This is required by tcm_qla2xxx code in order to invoke it's own fabric
specific session shutdown handler using se_session->sess_kref.
Signed-off-by: Joern Engel <joern@logfs.org>
Cc: Roland Dreier <roland@purestorage.com>
Cc: Arun Easi <arun.easi@qlogic.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/target_core_transport.c

@@ -315,7 +315,7 @@ void transport_register_session(
 }
 EXPORT_SYMBOL(transport_register_session);
 
-static void target_release_session(struct kref *kref)
+void target_release_session(struct kref *kref)
 {
 	struct se_session *se_sess = container_of(kref,
 			struct se_session, sess_kref);
@@ -332,6 +332,12 @@ EXPORT_SYMBOL(target_get_session);
 
 void target_put_session(struct se_session *se_sess)
 {
+	struct se_portal_group *tpg = se_sess->se_tpg;
+
+	if (tpg->se_tpg_tfo->put_session != NULL) {
+		tpg->se_tpg_tfo->put_session(se_sess);
+		return;
+	}
 	kref_put(&se_sess->sess_kref, target_release_session);
 }
 EXPORT_SYMBOL(target_put_session);

include/target/target_core_fabric.h

@@ -47,6 +47,7 @@ struct target_core_fabric_ops {
 	 */
 	int (*check_stop_free)(struct se_cmd *);
 	void (*release_cmd)(struct se_cmd *);
+	void (*put_session)(struct se_session *);
 	/*
 	 * Called with spin_lock_bh(struct se_portal_group->session_lock held.
 	 */