dm: merge max_hw_sector

Make sure dm honours max_hw_sectors of underlying devices

  We still have no firm testing evidence in support of this patch but
  believe it may help to resolve some bug reports.  - agk

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index b8b7c51..e765e19 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -115,6 +115,7 @@
 	unsigned short		max_hw_segments;
 	unsigned short		hardsect_size;
 	unsigned int		max_segment_size;
+	unsigned int		max_hw_sectors;
 	unsigned long		seg_boundary_mask;
 	unsigned long		bounce_pfn;
 	unsigned char		no_cluster; /* inverted so that 0 is default */