Correct failure to attach the PV block front device on Citrix

XenServer configurations that advertise the multi-page ring extension,
but only allow a single page of ring space.

sys/dev/xen/blkfront/blkfront.c:
	If only one page of ring space is being used, do not publish
	in the XenStore the number of pages in use (1), via either
	of the supported multi-page ring extension schemes.

	Single page operation is the same with or without the
	ring-page extension being negotiated.   Relying on the
	legacy behavior avoids an incompatible difference in how
	the two ring-page extension schemes that are out in the
	wild, deal with the base case of a single page.  The
	Amazon/Red Hat drivers use the same XenStore variable as
	if the extension was not negotiated.  The Citrix drivers
	assume the new ring reference XenStore variables will be
	available

Reported by:	Oliver Schonefeld <schonefeld@ids-mannheim.de>
MFC after:	3 days

0 files changed, 0 insertions, 0 deletions