xfs: eagerly remove vmap mappings to avoid upsetting Xen

xfs: eagerly remove vmap mappings to avoid upsetting Xen

patch ace2e92e193126711cb3a83a3752b2c5b8396950 in mainline.

XFS leaves stray mappings around when it vmaps memory to make it
virtually contigious.  This upsets Xen if one of those pages is being
recycled into a pagetable, since it finds an extra writable mapping of
the page.

This patch solves the problem in a brute force way, by making XFS
always eagerly unmap its mappings.

[ Stable: This works around a bug in 2.6.23.  We may come up with a
better solution for mainline, but this seems like a low-impact fix for
the stable kernel. ]

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: XFS masters <xfs-masters@oss.sgi.com>
Cc: Morten =?utf-8?q?B=C3=B8geskov?= <xen-users@morten.bogeskov.dk>
Cc: Mark Williamson <mark.williamson@cl.cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>