SUNRPC: Allow addition of new transports to a struct rpc_clnt

Add a function to allow creation and addition of a new transport
to an existing rpc_clnt
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

include/linux/sunrpc/clnt.h

@@ -186,6 +186,17 @@ int 		rpc_clnt_iterate_for_each_xprt(struct rpc_clnt *clnt,
 			int (*fn)(struct rpc_clnt *, struct rpc_xprt *, void *),
 			void *data);
 
+int 		rpc_clnt_test_and_add_xprt(struct rpc_clnt *clnt,
+			struct rpc_xprt_switch *xps,
+			struct rpc_xprt *xprt,
+			void *dummy);
+int		rpc_clnt_add_xprt(struct rpc_clnt *, struct xprt_create *,
+			int (*setup)(struct rpc_clnt *,
+				struct rpc_xprt_switch *,
+				struct rpc_xprt *,
+				void *),
+			void *data);
+
 const char *rpc_proc_name(const struct rpc_task *task);
 #endif /* __KERNEL__ */
 #endif /* _LINUX_SUNRPC_CLNT_H */

net/sunrpc/clnt.c

@@ -2492,7 +2492,10 @@ static int rpc_ping(struct rpc_clnt *clnt)
 	return err;
 }
 
-struct rpc_task *rpc_call_null(struct rpc_clnt *clnt, struct rpc_cred *cred, int flags)
+static
+struct rpc_task *rpc_call_null_helper(struct rpc_clnt *clnt,
+		struct rpc_xprt *xprt, struct rpc_cred *cred, int flags,
+		const struct rpc_call_ops *ops, void *data)
 {
 	struct rpc_message msg = {
 		.rpc_proc = &rpcproc_null,
@@ -2500,14 +2503,140 @@ struct rpc_task *rpc_call_null(struct rpc_clnt *clnt, struct rpc_cred *cred, int
 	};
 	struct rpc_task_setup task_setup_data = {
 		.rpc_client = clnt,
+		.rpc_xprt = xprt,
 		.rpc_message = &msg,
-		.callback_ops = &rpc_default_ops,
+		.callback_ops = (ops != NULL) ? ops : &rpc_default_ops,
+		.callback_data = data,
 		.flags = flags,
 	};
+
 	return rpc_run_task(&task_setup_data);
 }
+
+struct rpc_task *rpc_call_null(struct rpc_clnt *clnt, struct rpc_cred *cred, int flags)
+{
+	return rpc_call_null_helper(clnt, NULL, cred, flags, NULL, NULL);
+}
 EXPORT_SYMBOL_GPL(rpc_call_null);
 
+struct rpc_cb_add_xprt_calldata {
+	struct rpc_xprt_switch *xps;
+	struct rpc_xprt *xprt;
+};
+
+static void rpc_cb_add_xprt_done(struct rpc_task *task, void *calldata)
+{
+	struct rpc_cb_add_xprt_calldata *data = calldata;
+
+	if (task->tk_status == 0)
+		rpc_xprt_switch_add_xprt(data->xps, data->xprt);
+}
+
+static void rpc_cb_add_xprt_release(void *calldata)
+{
+	struct rpc_cb_add_xprt_calldata *data = calldata;
+
+	xprt_put(data->xprt);
+	xprt_switch_put(data->xps);
+	kfree(data);
+}
+
+const static struct rpc_call_ops rpc_cb_add_xprt_call_ops = {
+	.rpc_call_done = rpc_cb_add_xprt_done,
+	.rpc_release = rpc_cb_add_xprt_release,
+};
+
+/**
+ * rpc_clnt_test_and_add_xprt - Test and add a new transport to a rpc_clnt
+ * @clnt: pointer to struct rpc_clnt
+ * @xps: pointer to struct rpc_xprt_switch,
+ * @xprt: pointer struct rpc_xprt
+ * @dummy: unused
+ */
+int rpc_clnt_test_and_add_xprt(struct rpc_clnt *clnt,
+		struct rpc_xprt_switch *xps, struct rpc_xprt *xprt,
+		void *dummy)
+{
+	struct rpc_cb_add_xprt_calldata *data;
+	struct rpc_cred *cred;
+	struct rpc_task *task;
+
+	data = kmalloc(sizeof(*data), GFP_NOFS);
+	if (!data)
+		return -ENOMEM;
+	data->xps = xprt_switch_get(xps);
+	data->xprt = xprt_get(xprt);
+
+	cred = authnull_ops.lookup_cred(NULL, NULL, 0);
+	task = rpc_call_null_helper(clnt, xprt, cred,
+			RPC_TASK_SOFT|RPC_TASK_SOFTCONN|RPC_TASK_ASYNC,
+			&rpc_cb_add_xprt_call_ops, data);
+	put_rpccred(cred);
+	if (IS_ERR(task))
+		return PTR_ERR(task);
+	rpc_put_task(task);
+	return 1;
+}
+EXPORT_SYMBOL_GPL(rpc_clnt_test_and_add_xprt);
+
+/**
+ * rpc_clnt_add_xprt - Add a new transport to a rpc_clnt
+ * @clnt: pointer to struct rpc_clnt
+ * @xprtargs: pointer to struct xprt_create
+ * @setup: callback to test and/or set up the connection
+ * @data: pointer to setup function data
+ *
+ * Creates a new transport using the parameters set in args and
+ * adds it to clnt.
+ * If ping is set, then test that connectivity succeeds before
+ * adding the new transport.
+ *
+ */
+int rpc_clnt_add_xprt(struct rpc_clnt *clnt,
+		struct xprt_create *xprtargs,
+		int (*setup)(struct rpc_clnt *,
+			struct rpc_xprt_switch *,
+			struct rpc_xprt *,
+			void *),
+		void *data)
+{
+	struct rpc_xprt_switch *xps;
+	struct rpc_xprt *xprt;
+	unsigned char resvport;
+	int ret = 0;
+
+	rcu_read_lock();
+	xps = xprt_switch_get(rcu_dereference(clnt->cl_xpi.xpi_xpswitch));
+	xprt = xprt_iter_xprt(&clnt->cl_xpi);
+	if (xps == NULL || xprt == NULL) {
+		rcu_read_unlock();
+		return -EAGAIN;
+	}
+	resvport = xprt->resvport;
+	rcu_read_unlock();
+
+	xprt = xprt_create_transport(xprtargs);
+	if (IS_ERR(xprt)) {
+		ret = PTR_ERR(xprt);
+		goto out_put_switch;
+	}
+	xprt->resvport = resvport;
+
+	rpc_xprt_switch_set_roundrobin(xps);
+	if (setup) {
+		ret = setup(clnt, xps, xprt, data);
+		if (ret != 0)
+			goto out_put_xprt;
+	}
+	rpc_xprt_switch_add_xprt(xps, xprt);
+out_put_xprt:
+	xprt_put(xprt);
+out_put_switch:
+	xprt_switch_put(xps);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(rpc_clnt_add_xprt);
+
 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
 static void rpc_show_header(void)
 {