NFSv4.1 restrict GETATTR fs_location query to the main transport

In the presence of trunking transports, it's helpful to make sure
that during the migration event, the GETATTR for fs_location attribute
happens on the main transport.

Signed-off-by: Olga Kornievskaia <[e-mail]>
Signed-off-by: Trond Myklebust <[e-mail]>

fs/nfs/nfs4proc.c

···
 		.rpc_resp	= &res,
 		.rpc_cred	= cred,
 	};
+	struct nfs4_call_sync_data data = {
+		.seq_server = server,
+		.seq_args = &args.seq_args,
+		.seq_res = &res.seq_res,
+	};
+	struct rpc_task_setup task_setup_data = {
+		.rpc_client = clnt,
+		.rpc_message = &msg,
+		.callback_ops = server->nfs_client->cl_mvops->call_sync_ops,
+		.callback_data = &data,
+		.flags = RPC_TASK_NO_ROUND_ROBIN,
+	};
 	int status;
 
 	nfs_fattr_init(&locations->fattr);
···
 	locations->nlocations = 0;
 
 	nfs4_init_sequence(&args.seq_args, &res.seq_res, 0, 1);
-	status = nfs4_call_sync_sequence(clnt, server, &msg,
-					&args.seq_args, &res.seq_res);
+	status = nfs4_call_sync_custom(&task_setup_data);
 	if (status == NFS4_OK &&
 	    res.seq_res.sr_status_flags & SEQ4_STATUS_LEASE_MOVED)
 		status = -NFS4ERR_LEASE_MOVED;