nfs41: Backchannel callback service helper routines

Executes the backchannel task on the RPC state machine using
the existing open connection previously established by the client.

Signed-off-by: Ricardo Labiaga <ricardo.labiaga@netapp.com>

nfs41: Add bc_svc.o to sunrpc Makefile.

[nfs41: bc_send() does not need to be exported outside RPC module]
[nfs41: xprt_free_bc_request() need not be exported outside RPC module]
Signed-off-by: Ricardo Labiaga <Ricardo.Labiaga@netapp.com>
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
[Update copyright]
Signed-off-by: Ricardo Labiaga <Ricardo.Labiaga@netapp.com>
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
diff --git a/net/sunrpc/Makefile b/net/sunrpc/Makefile
index 4a01f96..db73fd2 100644
--- a/net/sunrpc/Makefile
+++ b/net/sunrpc/Makefile
@@ -13,6 +13,6 @@
 	    rpcb_clnt.o timer.o xdr.o \
 	    sunrpc_syms.o cache.o rpc_pipe.o \
 	    svc_xprt.o
-sunrpc-$(CONFIG_NFS_V4_1) += backchannel_rqst.o
+sunrpc-$(CONFIG_NFS_V4_1) += backchannel_rqst.o bc_svc.o
 sunrpc-$(CONFIG_PROC_FS) += stats.o
 sunrpc-$(CONFIG_SYSCTL) += sysctl.o