s390/mm: make pmd/pud_deref() large page aware

pmd/pud_deref() assume that they will never operate on large pmd/pud
entries, and therefore only use the non-large _xxx_ENTRY_ORIGIN mask.
With commit 9ec8fa8d ("s390/vmemmap: extend modify_pagetable()
to handle vmemmap"), that assumption is no longer true, at least for
pmd_deref().

In theory, we could end up with wrong addresses because some of the
non-address bits of a large entry would not be masked out.
In practice, this does not (yet) show any impact, because vmemmap_free()
is currently never used for s390.

Fix pmd/pud_deref() to check for the entry type and use the
_xxx_ENTRY_ORIGIN_LARGE mask for large entries.

While at it, also move pmd/pud_pfn() around, in order to avoid code
duplication, because they do the same thing.

Fixes: 9ec8fa8d ("s390/vmemmap: extend modify_pagetable() to handle vmemmap")
Cc: <stable@vger.kernel.org> # 5.9
Signed-off-by: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

arch/s390/include/asm/pgtable.h

@@ -692,16 +692,6 @@ static inline int pud_large(pud_t pud)
 	return !!(pud_val(pud) & _REGION3_ENTRY_LARGE);
 }
 
-static inline unsigned long pud_pfn(pud_t pud)
-{
-	unsigned long origin_mask;
-
-	origin_mask = _REGION_ENTRY_ORIGIN;
-	if (pud_large(pud))
-		origin_mask = _REGION3_ENTRY_ORIGIN_LARGE;
-	return (pud_val(pud) & origin_mask) >> PAGE_SHIFT;
-}
-
 #define pmd_leaf	pmd_large
 static inline int pmd_large(pmd_t pmd)
 {
@@ -747,16 +737,6 @@ static inline int pmd_none(pmd_t pmd)
 	return pmd_val(pmd) == _SEGMENT_ENTRY_EMPTY;
 }
 
-static inline unsigned long pmd_pfn(pmd_t pmd)
-{
-	unsigned long origin_mask;
-
-	origin_mask = _SEGMENT_ENTRY_ORIGIN;
-	if (pmd_large(pmd))
-		origin_mask = _SEGMENT_ENTRY_ORIGIN_LARGE;
-	return (pmd_val(pmd) & origin_mask) >> PAGE_SHIFT;
-}
-
 #define pmd_write pmd_write
 static inline int pmd_write(pmd_t pmd)
 {
@@ -1238,11 +1218,39 @@ static inline pte_t mk_pte(struct page *page, pgprot_t pgprot)
 #define pud_index(address) (((address) >> PUD_SHIFT) & (PTRS_PER_PUD-1))
 #define pmd_index(address) (((address) >> PMD_SHIFT) & (PTRS_PER_PMD-1))
 
-#define pmd_deref(pmd) (pmd_val(pmd) & _SEGMENT_ENTRY_ORIGIN)
-#define pud_deref(pud) (pud_val(pud) & _REGION_ENTRY_ORIGIN)
 #define p4d_deref(pud) (p4d_val(pud) & _REGION_ENTRY_ORIGIN)
 #define pgd_deref(pgd) (pgd_val(pgd) & _REGION_ENTRY_ORIGIN)
 
+static inline unsigned long pmd_deref(pmd_t pmd)
+{
+	unsigned long origin_mask;
+
+	origin_mask = _SEGMENT_ENTRY_ORIGIN;
+	if (pmd_large(pmd))
+		origin_mask = _SEGMENT_ENTRY_ORIGIN_LARGE;
+	return pmd_val(pmd) & origin_mask;
+}
+
+static inline unsigned long pmd_pfn(pmd_t pmd)
+{
+	return pmd_deref(pmd) >> PAGE_SHIFT;
+}
+
+static inline unsigned long pud_deref(pud_t pud)
+{
+	unsigned long origin_mask;
+
+	origin_mask = _REGION_ENTRY_ORIGIN;
+	if (pud_large(pud))
+		origin_mask = _REGION3_ENTRY_ORIGIN_LARGE;
+	return pud_val(pud) & origin_mask;
+}
+
+static inline unsigned long pud_pfn(pud_t pud)
+{
+	return pud_deref(pud) >> PAGE_SHIFT;
+}
+
 /*
  * The pgd_offset function *always* adds the index for the top-level
  * region/segment table. This is done to get a sequence like the