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>

arch/s390/Kconfig

@@ -415,6 +415,10 @@ config ARCH_ENABLE_MEMORY_HOTPLUG
 config ARCH_ENABLE_MEMORY_HOTREMOVE
 	def_bool y
 
+config ARCH_ENABLE_SPLIT_PMD_PTLOCK
+	def_bool y
+	depends on 64BIT
+
 config FORCE_MAX_ZONEORDER
 	int
 	default "9"

arch/s390/include/asm/pgalloc.h

@@ -92,11 +92,22 @@ static inline pud_t *pud_alloc_one(struct mm_struct *mm, unsigned long address)
 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)
 {

arch/s390/mm/pgtable.c

@@ -1397,7 +1397,7 @@ void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
 {
 	struct list_head *lh = (struct list_head *) pgtable;
 
-	assert_spin_locked(&mm->page_table_lock);
+	assert_spin_locked(pmd_lockptr(mm, pmdp));
 
 	/* FIFO */
 	if (!pmd_huge_pte(mm, pmdp))
@@ -1413,7 +1413,7 @@ pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp)
 	pgtable_t pgtable;
 	pte_t *ptep;
 
-	assert_spin_locked(&mm->page_table_lock);
+	assert_spin_locked(pmd_lockptr(mm, pmdp));
 
 	/* FIFO */
 	pgtable = pmd_huge_pte(mm, pmdp);