s390/mm: enable split page table lock for PMD level

Add the pgtable_pmd_page_ctor/pgtable_pmd_page_dtor calls to the pmd
allocation and free functions and enable ARCH_ENABLE_SPLIT_PMD_PTLOCK
for 64 bit.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/include/asm/pgalloc.h b/arch/s390/include/asm/pgalloc.h
index 14d43c7..884017c 100644
--- a/arch/s390/include/asm/pgalloc.h
+++ b/arch/s390/include/asm/pgalloc.h
@@ -92,11 +92,22 @@
 static inline pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long vmaddr)
 {
 	unsigned long *table = crst_table_alloc(mm);
-	if (table)
-		crst_table_init(table, _SEGMENT_ENTRY_EMPTY);
+
+	if (!table)
+		return NULL;
+	crst_table_init(table, _SEGMENT_ENTRY_EMPTY);
+	if (!pgtable_pmd_page_ctor(virt_to_page(table))) {
+		crst_table_free(mm, table);
+		return NULL;
+	}
 	return (pmd_t *) table;
 }
-#define pmd_free(mm, pmd) crst_table_free(mm, (unsigned long *) pmd)
+
+static inline void pmd_free(struct mm_struct *mm, pmd_t *pmd)
+{
+	pgtable_pmd_page_dtor(virt_to_page(pmd));
+	crst_table_free(mm, (unsigned long *) pmd);
+}
 
 static inline void pgd_populate(struct mm_struct *mm, pgd_t *pgd, pud_t *pud)
 {