s390/mm: Allocate page table with PAGE_SIZE granularity

Make vmem_pte_alloc() consistent by always allocating page table of
PAGE_SIZE granularity, regardless of whether page_table_alloc() (with
slab) or memblock_alloc() is used. This ensures page table can be fully
freed when the corresponding page table entries are removed.

Fixes: d08d4e7 ("s390/mm: use full 4KB page for 2KB PTE")
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>

Author: sumanthkorikkar

arch/s390/mm/vmem.c

@@ -64,13 +64,12 @@ void *vmem_crst_alloc(unsigned long val)
 
 pte_t __ref *vmem_pte_alloc(void)
 {
-	unsigned long size = PTRS_PER_PTE * sizeof(pte_t);
 	pte_t *pte;
 
 	if (slab_is_available())
-		pte = (pte_t *) page_table_alloc(&init_mm);
+		pte = (pte_t *)page_table_alloc(&init_mm);
 	else
-		pte = (pte_t *) memblock_alloc(size, size);
+		pte = (pte_t *)memblock_alloc(PAGE_SIZE, PAGE_SIZE);
 	if (!pte)
 		return NULL;
 	memset64((u64 *)pte, _PAGE_INVALID, PTRS_PER_PTE);