nfsd: use nfs client rpc callback program

since commit ff7d9756b501744540be65e172d27ee321d86103
"nfsd: use static memory for callback program and stats"
do_probe_callback uses a static callback program
(NFS4_CALLBACK) rather than the one set in clp->cl_callback.cb_prog
as passed in by the client in setclientid (4.0)
or create_session (4.1).

This patches introduces rpc_create_args.prognumber that allows
overriding program->number when creating rpc_clnt.

Signed-off-by: Benny Halevy <[e-mail]>
Signed-off-by: J. Bruce Fields <[e-mail]>

fs/nfsd/nfs4callback.c

···
 		.addrsize	= sizeof(addr),
 		.timeout	= &timeparms,
 		.program	= &cb_program,
+		.prognumber	= cb->cb_prog,
 		.version	= nfs_cb_version[1]->number,
 		.authflavor	= RPC_AUTH_UNIX, /* XXX: need AUTH_GSS... */
 		.flags		= (RPC_CLNT_CREATE_NOPING | RPC_CLNT_CREATE_QUIET),

include/linux/sunrpc/clnt.h

···
 	const struct rpc_timeout *timeout;
 	char			*servername;
 	struct rpc_program	*program;
+	u32			prognumber;	/* overrides program->number */
 	u32			version;
 	rpc_authflavor_t	authflavor;
 	unsigned long		flags;

net/sunrpc/clnt.c

···
 	clnt->cl_procinfo = version->procs;
 	clnt->cl_maxproc  = version->nrprocs;
 	clnt->cl_protname = program->name;
-	clnt->cl_prog     = program->number;
+	clnt->cl_prog     = args->prognumber ? : program->number;
 	clnt->cl_vers     = version->number;
 	clnt->cl_stats    = program->stats;
 	clnt->cl_metrics  = rpc_alloc_iostats(clnt);