scsi: iscsi: Add iscsi_cls_conn refcount helpers

There are a couple places where we could free the iscsi_cls_conn while it's
still in use. This adds some helpers to get/put a refcount on the struct
and converts an exiting user. Subsequent commits will then use the helpers
to fix 2 bugs in the eh code.

Link: https://lore.kernel.org/r/[e-mail]
Reviewed-by: Lee Duncan <[e-mail]>
Signed-off-by: Mike Christie <[e-mail]>
Signed-off-by: Martin K. Petersen <[e-mail]>

drivers/scsi/libiscsi.c

···
 			   enum iscsi_err err)
 {
 	struct iscsi_conn *conn;
-	struct device *dev;
 
 	spin_lock_bh(&session->frwd_lock);
 	conn = session->leadconn;
···
 		return;
 	}
 
-	dev = get_device(&conn->cls_conn->dev);
+	iscsi_get_conn(conn->cls_conn);
 	spin_unlock_bh(&session->frwd_lock);
-	if (!dev)
-	        return;
 	/*
 	 * if the host is being removed bypass the connection
 	 * recovery initialization because we are going to kill
···
 		iscsi_conn_error_event(conn->cls_conn, err);
 	else
 		iscsi_conn_failure(conn, err);
-	put_device(dev);
+	iscsi_put_conn(conn->cls_conn);
 }
 EXPORT_SYMBOL_GPL(iscsi_session_failure);
 

drivers/scsi/scsi_transport_iscsi.c

···
 }
 EXPORT_SYMBOL_GPL(iscsi_destroy_conn);
 
+void iscsi_put_conn(struct iscsi_cls_conn *conn)
+{
+	put_device(&conn->dev);
+}
+EXPORT_SYMBOL_GPL(iscsi_put_conn);
+
+void iscsi_get_conn(struct iscsi_cls_conn *conn)
+{
+	get_device(&conn->dev);
+}
+EXPORT_SYMBOL_GPL(iscsi_get_conn);
+
 /*
  * iscsi interface functions
  */

include/scsi/scsi_transport_iscsi.h

···
 extern void iscsi_free_session(struct iscsi_cls_session *session);
 extern struct iscsi_cls_conn *iscsi_create_conn(struct iscsi_cls_session *sess,
 						int dd_size, uint32_t cid);
+extern void iscsi_put_conn(struct iscsi_cls_conn *conn);
+extern void iscsi_get_conn(struct iscsi_cls_conn *conn);
 extern int iscsi_destroy_conn(struct iscsi_cls_conn *conn);
 extern void iscsi_unblock_session(struct iscsi_cls_session *session);
 extern void iscsi_block_session(struct iscsi_cls_session *session);