1 files changed, 24 insertions, 10 deletions

diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index 96549df836ee..c431f5a57960 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -2359,6 +2359,15 @@ static struct rpc_xprt *xs_setup_bc_tcp(struct xprt_create *args)
         struct svc_sock *bc_sock;
         struct rpc_xprt *ret;
 
+        if (args->bc_xprt->xpt_bc_xprt) {
+                /*
+                 * This server connection already has a backchannel
+                 * export; we can't create a new one, as we wouldn't be
+                 * able to match replies based on xid any more.  So,
+                 * reuse the already-existing one:
+                 */
+                 return args->bc_xprt->xpt_bc_xprt;
+        }
         xprt = xs_setup_xprt(args, xprt_tcp_slot_table_entries);
         if (IS_ERR(xprt))
                 return xprt;
@@ -2375,16 +2384,6 @@ static struct rpc_xprt *xs_setup_bc_tcp(struct xprt_create *args)
         xprt->reestablish_timeout = 0;
         xprt->idle_timeout = 0;
 
-        /*
-         * The backchannel uses the same socket connection as the
-         * forechannel
-         */
-        xprt->bc_xprt = args->bc_xprt;
-        bc_sock = container_of(args->bc_xprt, struct svc_sock, sk_xprt);
-        bc_sock->sk_bc_xprt = xprt;
-        transport->sock = bc_sock->sk_sock;
-        transport->inet = bc_sock->sk_sk;
-
         xprt->ops = &bc_tcp_ops;
 
         switch (addr->sa_family) {
@@ -2407,6 +2406,20 @@ static struct rpc_xprt *xs_setup_bc_tcp(struct xprt_create *args)
                         xprt->address_strings[RPC_DISPLAY_PROTO]);
 
         /*
+         * Once we've associated a backchannel xprt with a connection,
+         * we want to keep it around as long as long as the connection
+         * lasts, in case we need to start using it for a backchannel
+         * again; this reference won't be dropped until bc_xprt is
+         * destroyed.
+         */
+        xprt_get(xprt);
+        args->bc_xprt->xpt_bc_xprt = xprt;
+        xprt->bc_xprt = args->bc_xprt;
+        bc_sock = container_of(args->bc_xprt, struct svc_sock, sk_xprt);
+        transport->sock = bc_sock->sk_sock;
+        transport->inet = bc_sock->sk_sk;
+
+        /*
          * Since we don't want connections for the backchannel, we set
          * the xprt status to connected
          */
@@ -2415,6 +2428,7 @@ static struct rpc_xprt *xs_setup_bc_tcp(struct xprt_create *args)
 
         if (try_module_get(THIS_MODULE))
                 return xprt;
+        xprt_put(xprt);
         ret = ERR_PTR(-EINVAL);
 out_err:
         xprt_free(xprt);