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>

2 files changed, 142 insertions, 2 deletions

diff --git a/include/linux/sunrpc/clnt.h b/include/linux/sunrpc/clnt.h
index d6510f64a361..9a7ddbaf116e 100644
--- a/include/linux/sunrpc/clnt.h
+++ b/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 */
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index 4b6ceb7c5e1d..7e0c9bf22df8 100644
--- a/net/sunrpc/clnt.c
+++ b/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)
 {