xprtrdma: Handle incoming backward direction RPC calls

Introduce a code path in the rpcrdma_reply_handler() to catch
incoming backward direction RPC calls and route them to the ULP's
backchannel server.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Tested-By: Devesh Sharma <devesh.sharma@avagotech.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
index e2d23ea..eb87d96e8 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -353,6 +353,7 @@
 	unsigned long		failed_marshal_count;
 	unsigned long		bad_reply_count;
 	unsigned long		nomsg_call_count;
+	unsigned long		bcall_count;
 };
 
 /*
@@ -520,6 +521,7 @@
 #if defined(CONFIG_SUNRPC_BACKCHANNEL)
 int xprt_rdma_bc_setup(struct rpc_xprt *, unsigned int);
 int rpcrdma_bc_post_recv(struct rpcrdma_xprt *, unsigned int);
+void rpcrdma_bc_receive_call(struct rpcrdma_xprt *, struct rpcrdma_rep *);
 int rpcrdma_bc_marshal_reply(struct rpc_rqst *);
 void xprt_rdma_bc_free_rqst(struct rpc_rqst *);
 void xprt_rdma_bc_destroy(struct rpc_xprt *, unsigned int);