svcrdma: Add backward direction service for RPC/RDMA transport

On NFSv4.1 mount points, the Linux NFS client uses this transport
endpoint to receive backward direction calls and route replies back
to the NFSv4.1 server.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Acked-by: "J. Bruce Fields" <bfields@fieldses.org>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Tested-By: Devesh Sharma <devesh.sharma@avagotech.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

2 files changed, 64 insertions, 0 deletions

diff --git a/net/sunrpc/xprtrdma/svc_rdma.c b/net/sunrpc/xprtrdma/svc_rdma.c
index 2cd252f023a5..1b7051bdbdc8 100644
--- a/net/sunrpc/xprtrdma/svc_rdma.c
+++ b/net/sunrpc/xprtrdma/svc_rdma.c
@@ -239,6 +239,9 @@ void svc_rdma_cleanup(void)
                 unregister_sysctl_table(svcrdma_table_header);
                 svcrdma_table_header = NULL;
         }
+#if defined(CONFIG_SUNRPC_BACKCHANNEL)
+        svc_unreg_xprt_class(&svc_rdma_bc_class);
+#endif
         svc_unreg_xprt_class(&svc_rdma_class);
         kmem_cache_destroy(svc_rdma_map_cachep);
         kmem_cache_destroy(svc_rdma_ctxt_cachep);
@@ -286,6 +289,9 @@ int svc_rdma_init(void)
 
         /* Register RDMA with the SVC transport switch */
         svc_reg_xprt_class(&svc_rdma_class);
+#if defined(CONFIG_SUNRPC_BACKCHANNEL)
+        svc_reg_xprt_class(&svc_rdma_bc_class);
+#endif
         return 0;
  err1:
         kmem_cache_destroy(svc_rdma_map_cachep);
diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c
index fcc3eb80c265..a133b1e5b5f6 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_transport.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c
@@ -56,6 +56,7 @@
 
 #define RPCDBG_FACILITY RPCDBG_SVCXPRT
 
+static struct svcxprt_rdma *rdma_create_xprt(struct svc_serv *, int);
 static struct svc_xprt *svc_rdma_create(struct svc_serv *serv,
                                         struct net *net,
                                         struct sockaddr *sa, int salen,
@@ -95,6 +96,63 @@ struct svc_xprt_class svc_rdma_class = {
         .xcl_ident = XPRT_TRANSPORT_RDMA,
 };
 
+#if defined(CONFIG_SUNRPC_BACKCHANNEL)
+static struct svc_xprt *svc_rdma_bc_create(struct svc_serv *, struct net *,
+                                           struct sockaddr *, int, int);
+static void svc_rdma_bc_detach(struct svc_xprt *);
+static void svc_rdma_bc_free(struct svc_xprt *);
+
+static struct svc_xprt_ops svc_rdma_bc_ops = {
+        .xpo_create = svc_rdma_bc_create,
+        .xpo_detach = svc_rdma_bc_detach,
+        .xpo_free = svc_rdma_bc_free,
+        .xpo_prep_reply_hdr = svc_rdma_prep_reply_hdr,
+        .xpo_secure_port = svc_rdma_secure_port,
+};
+
+struct svc_xprt_class svc_rdma_bc_class = {
+        .xcl_name = "rdma-bc",
+        .xcl_owner = THIS_MODULE,
+        .xcl_ops = &svc_rdma_bc_ops,
+        .xcl_max_payload = (1024 - RPCRDMA_HDRLEN_MIN)
+};
+
+static struct svc_xprt *svc_rdma_bc_create(struct svc_serv *serv,
+                                           struct net *net,
+                                           struct sockaddr *sa, int salen,
+                                           int flags)
+{
+        struct svcxprt_rdma *cma_xprt;
+        struct svc_xprt *xprt;
+
+        cma_xprt = rdma_create_xprt(serv, 0);
+        if (!cma_xprt)
+                return ERR_PTR(-ENOMEM);
+        xprt = &cma_xprt->sc_xprt;
+
+        svc_xprt_init(net, &svc_rdma_bc_class, xprt, serv);
+        serv->sv_bc_xprt = xprt;
+
+        dprintk("svcrdma: %s(%p)\n", __func__, xprt);
+        return xprt;
+}
+
+static void svc_rdma_bc_detach(struct svc_xprt *xprt)
+{
+        dprintk("svcrdma: %s(%p)\n", __func__, xprt);
+}
+
+static void svc_rdma_bc_free(struct svc_xprt *xprt)
+{
+        struct svcxprt_rdma *rdma =
+                container_of(xprt, struct svcxprt_rdma, sc_xprt);
+
+        dprintk("svcrdma: %s(%p)\n", __func__, xprt);
+        if (xprt)
+                kfree(rdma);
+}
+#endif  /* CONFIG_SUNRPC_BACKCHANNEL */
+
 struct svc_rdma_op_ctxt *svc_rdma_get_context(struct svcxprt_rdma *xprt)
 {
         struct svc_rdma_op_ctxt *ctxt;