SUNRPC: Finish API to load RPC transport implementations dynamically

Allow RPC client transport implementations to be loaded as needed, or
as they become available from distributors or third-party vendors.

Note that we leave the IP sockets implementation in sunrpc.o
permanently, as IP functionality is always available in any
kernel that runs NFS.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Tom Talpey <tmt@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

2 files changed, 57 insertions, 16 deletions

diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index 520859622af5..7f8c60b84396 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -983,19 +983,23 @@ struct rpc_xprt *xprt_create_transport(struct rpc_xprtsock_create *args)
 {
         struct rpc_xprt *xprt;
         struct rpc_rqst *req;
+        struct xprt_class *t;
 
-        switch (args->proto) {
-        case IPPROTO_UDP:
-                xprt = xs_setup_udp(args);
-                break;
-        case IPPROTO_TCP:
-                xprt = xs_setup_tcp(args);
-                break;
-        default:
-                printk(KERN_ERR "RPC: unrecognized transport protocol: %d\n",
-                                args->proto);
-                return ERR_PTR(-EIO);
+        spin_lock(&xprt_list_lock);
+        list_for_each_entry(t, &xprt_list, list) {
+                if ((t->family == args->dstaddr->sa_family) &&
+                    (t->protocol == args->proto)) {
+                        spin_unlock(&xprt_list_lock);
+                        goto found;
+                }
         }
+        spin_unlock(&xprt_list_lock);
+        printk(KERN_ERR "RPC: transport (%u/%d) not supported\n",
+                        args->dstaddr->sa_family, args->proto);
+        return ERR_PTR(-EIO);
+
+found:
+        xprt = t->setup(args);
         if (IS_ERR(xprt)) {
                 dprintk("RPC:       xprt_create_transport: failed, %ld\n",
                                 -PTR_ERR(xprt));
diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index 5bdce8fa2d56..3bc9c921c82f 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -20,6 +20,7 @@
 
 #include <linux/types.h>
 #include <linux/slab.h>
+#include <linux/module.h>
 #include <linux/capability.h>
 #include <linux/pagemap.h>
 #include <linux/errno.h>
@@ -777,6 +778,7 @@ static void xs_destroy(struct rpc_xprt *xprt)
         xs_free_peer_addresses(xprt);
         kfree(xprt->slot);
         kfree(xprt);
+        module_put(THIS_MODULE);
 }
 
 static inline struct rpc_xprt *xprt_from_sock(struct sock *sk)
@@ -1782,7 +1784,8 @@ static struct rpc_xprt_ops xs_tcp_ops = {
         .print_stats            = xs_tcp_print_stats,
 };
 
-static struct rpc_xprt *xs_setup_xprt(struct rpc_xprtsock_create *args, unsigned int slot_table_size)
+static struct rpc_xprt *xs_setup_xprt(struct rpc_xprtsock_create *args,
+                                      unsigned int slot_table_size)
 {
         struct rpc_xprt *xprt;
         struct sock_xprt *new;
@@ -1876,7 +1879,12 @@ struct rpc_xprt *xs_setup_udp(struct rpc_xprtsock_create *args)
         dprintk("RPC:       set up transport to address %s\n",
                         xprt->address_strings[RPC_DISPLAY_ALL]);
 
-        return xprt;
+        if (try_module_get(THIS_MODULE))
+                return xprt;
+
+        kfree(xprt->slot);
+        kfree(xprt);
+        return ERR_PTR(-EINVAL);
 }
 
 /**
@@ -1934,11 +1942,34 @@ struct rpc_xprt *xs_setup_tcp(struct rpc_xprtsock_create *args)
         dprintk("RPC:       set up transport to address %s\n",
                         xprt->address_strings[RPC_DISPLAY_ALL]);
 
-        return xprt;
+        if (try_module_get(THIS_MODULE))
+                return xprt;
+
+        kfree(xprt->slot);
+        kfree(xprt);
+        return ERR_PTR(-EINVAL);
 }
 
+static struct xprt_class        xs_udp_transport = {
+        .list           = LIST_HEAD_INIT(xs_udp_transport.list),
+        .name           = "udp",
+        .owner          = THIS_MODULE,
+        .family         = AF_INET,
+        .protocol       = IPPROTO_UDP,
+        .setup          = xs_setup_udp,
+};
+
+static struct xprt_class        xs_tcp_transport = {
+        .list           = LIST_HEAD_INIT(xs_tcp_transport.list),
+        .name           = "tcp",
+        .owner          = THIS_MODULE,
+        .family         = AF_INET,
+        .protocol       = IPPROTO_TCP,
+        .setup          = xs_setup_tcp,
+};
+
 /**
- * init_socket_xprt - set up xprtsock's sysctls
+ * init_socket_xprt - set up xprtsock's sysctls, register with RPC client
  *
  */
 int init_socket_xprt(void)
@@ -1948,11 +1979,14 @@ int init_socket_xprt(void)
                 sunrpc_table_header = register_sysctl_table(sunrpc_table);
 #endif
 
+        xprt_register_transport(&xs_udp_transport);
+        xprt_register_transport(&xs_tcp_transport);
+
         return 0;
 }
 
 /**
- * cleanup_socket_xprt - remove xprtsock's sysctls
+ * cleanup_socket_xprt - remove xprtsock's sysctls, unregister
  *
  */
 void cleanup_socket_xprt(void)
@@ -1963,4 +1997,7 @@ void cleanup_socket_xprt(void)
                 sunrpc_table_header = NULL;
         }
 #endif
+
+        xprt_unregister_transport(&xs_udp_transport);
+        xprt_unregister_transport(&xs_tcp_transport);
 }