[S390] System z large page support.

This adds hugetlbfs support on System z, using both hardware large page
support if available and software large page emulation on older hardware.
Shared (large) page tables are implemented in software emulation mode,
by using page->index of the first tail page from a compound large page
to store page table information.

Signed-off-by: Gerald Schaefer <geraldsc@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/mm/fault.c

@@ -28,6 +28,7 @@
 #include <linux/hardirq.h>
 #include <linux/kprobes.h>
 #include <linux/uaccess.h>
+#include <linux/hugetlb.h>
 #include <asm/system.h>
 #include <asm/pgtable.h>
 #include <asm/s390_ext.h>
@@ -367,6 +368,8 @@ good_area:
 	}
 
 survive:
+	if (is_vm_hugetlb_page(vma))
+		address &= HPAGE_MASK;
 	/*
 	 * If for any reason at all we couldn't handle the fault,
 	 * make sure we exit gracefully rather than endlessly redo