net: genetlink: introduce dump info struct to be available during dumpit op

Currently the cb->data is taken by ops during non-parallel dumping.
Introduce a new structure genl_dumpit_info and store the ops there.
Distribute the info to both non-parallel and parallel dumping. Also add
a helper genl_dumpit_info() to easily get the info structure in the
dumpit callback from cb.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/genetlink.h

@@ -127,6 +127,20 @@ enum genl_validate_flags {
 	GENL_DONT_VALIDATE_DUMP_STRICT		= BIT(2),
 };
 
+/**
+ * struct genl_info - info that is available during dumpit op call
+ * @ops: generic netlink ops - for internal genl code usage
+ */
+struct genl_dumpit_info {
+	const struct genl_ops *ops;
+};
+
+static inline const struct genl_dumpit_info *
+genl_dumpit_info(struct netlink_callback *cb)
+{
+	return cb->data;
+}
+
 /**
  * struct genl_ops - generic netlink operations
  * @cmd: command identifier