svcrdma: Select NFSv4.1 backchannel transport based on forward channel

The current code always selects XPRT_TRANSPORT_BC_TCP for the back
channel, even when the forward channel was not TCP (eg, RDMA). When
a 4.1 mount is attempted with RDMA, the server panics in the TCP BC
code when trying to send CB_NULL.

Instead, construct the transport protocol number from the forward
channel transport or'd with XPRT_TRANSPORT_BC. Transports that do
not support bi-directional RPC will not have registered a "BC"
transport, causing create_backchannel_client() to fail immediately.

Fixes: https://bugzilla.linux-nfs.org/show_bug.cgi?id=265
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

3 files changed, 4 insertions, 1 deletions

diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index b507cd327d9b..b2437ee93657 100644
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -692,6 +692,7 @@ static struct svc_xprt_class svc_udp_class = {
         .xcl_owner = THIS_MODULE,
         .xcl_ops = &svc_udp_ops,
         .xcl_max_payload = RPCSVC_MAXPAYLOAD_UDP,
+        .xcl_ident = XPRT_TRANSPORT_UDP,
 };
 
 static void svc_udp_init(struct svc_sock *svsk, struct svc_serv *serv)
@@ -1292,6 +1293,7 @@ static struct svc_xprt_class svc_tcp_class = {
         .xcl_owner = THIS_MODULE,
         .xcl_ops = &svc_tcp_ops,
         .xcl_max_payload = RPCSVC_MAXPAYLOAD_TCP,
+        .xcl_ident = XPRT_TRANSPORT_TCP,
 };
 
 void svc_init_xprt_sock(void)
diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index c3b2b3369e52..51c63165073c 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -1306,7 +1306,7 @@ struct rpc_xprt *xprt_create_transport(struct xprt_create *args)
                 }
         }
         spin_unlock(&xprt_list_lock);
-        printk(KERN_ERR "RPC: transport (%d) not supported\n", args->ident);
+        dprintk("RPC: transport (%d) not supported\n", args->ident);
         return ERR_PTR(-EIO);
 
 found:
diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c
index e7323fbbd348..06a5d9235107 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_transport.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c
@@ -92,6 +92,7 @@ struct svc_xprt_class svc_rdma_class = {
         .xcl_owner = THIS_MODULE,
         .xcl_ops = &svc_rdma_ops,
         .xcl_max_payload = RPCSVC_MAXPAYLOAD_TCP,
+        .xcl_ident = XPRT_TRANSPORT_RDMA,
 };
 
 struct svc_rdma_op_ctxt *svc_rdma_get_context(struct svcxprt_rdma *xprt)