s390/mm: modify pmdp_invalidate to return old value.

It's required to avoid losing dirty and accessed bits.

Link: http://lkml.kernel.org/r/20171213105756.69879-8-kirill.shutemov@linux.intel.com
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/s390/include/asm/pgtable.h

@@ -1505,12 +1505,12 @@ static inline pmd_t pmdp_huge_clear_flush(struct vm_area_struct *vma,
 }
 
 #define __HAVE_ARCH_PMDP_INVALIDATE
-static inline void pmdp_invalidate(struct vm_area_struct *vma,
+static inline pmd_t pmdp_invalidate(struct vm_area_struct *vma,
 				   unsigned long addr, pmd_t *pmdp)
 {
 	pmd_t pmd = __pmd(pmd_val(*pmdp) | _SEGMENT_ENTRY_INVALID);
 
-	pmdp_xchg_direct(vma->vm_mm, addr, pmdp, pmd);
+	return pmdp_xchg_direct(vma->vm_mm, addr, pmdp, pmd);
 }
 
 #define __HAVE_ARCH_PMDP_SET_WRPROTECT