Not all kernels have relay (formerly relayfs) support.  When they do,
there are a few forms.

  none
  	No relay support.

  fs5
  	The first relayfs in Linus's tree uses relayfs_fs.h with 5
  	parms to relay_open.

	commit e82894f84dbba130ab46c97748c03647f8204f92
	Author: Tom Zanussi <zanussi@us.ibm.com>
	Date:   Tue Sep 6 15:16:30 2005 -0700

	This commit appears in v2.6.14-rc1~734.

  relay5
  	Then it was made "relay", not "relayfs", and the header file
  	changed.

	commit b86ff981a8252d83d6a7719ae09f3a05307e3592
	Author: Jens Axboe <axboe@suse.de>
	Date:   Thu Mar 23 19:56:55 2006 +0100

  relay6	NEW
  	Finally a private data parameter was added to relay_open.

	commit 23c887522e912ca494950796a95df8dd210f4b01
	Author: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
	Date:   Sat Feb 10 01:45:05 2007 -0800