mm: add dummy pmd_young() for architectures not having it

In order to avoid #ifdeffery add a dummy pmd_young() implementation as a
fallback.  This is required for the later patch "mm: introduce
arch_has_hw_nonleaf_pmd_young()".

Link: https://lkml.kernel.org/r/fd3ac3cd-7349-6bbd-890a-71a9454ca0b3@suse.com
Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Yu Zhao <yuzhao@google.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Sander Eikelenboom <linux@eikelenboom.it>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

arch/loongarch/include/asm/pgtable.h

@@ -482,6 +482,7 @@ static inline pmd_t pmd_mkdirty(pmd_t pmd)
 	return pmd;
 }
 
+#define pmd_young pmd_young
 static inline int pmd_young(pmd_t pmd)
 {
 	return !!(pmd_val(pmd) & _PAGE_ACCESSED);

arch/mips/include/asm/pgtable.h

@@ -622,6 +622,7 @@ static inline pmd_t pmd_mkdirty(pmd_t pmd)
 	return pmd;
 }
 
+#define pmd_young pmd_young
 static inline int pmd_young(pmd_t pmd)
 {
 	return !!(pmd_val(pmd) & _PAGE_ACCESSED);

arch/riscv/include/asm/pgtable.h

@@ -600,6 +600,7 @@ static inline int pmd_dirty(pmd_t pmd)
 	return pte_dirty(pmd_pte(pmd));
 }
 
+#define pmd_young pmd_young
 static inline int pmd_young(pmd_t pmd)
 {
 	return pte_young(pmd_pte(pmd));

arch/s390/include/asm/pgtable.h

@@ -763,6 +763,7 @@ static inline int pmd_dirty(pmd_t pmd)
 	return (pmd_val(pmd) & _SEGMENT_ENTRY_DIRTY) != 0;
 }
 
+#define pmd_young pmd_young
 static inline int pmd_young(pmd_t pmd)
 {
 	return (pmd_val(pmd) & _SEGMENT_ENTRY_YOUNG) != 0;

arch/sparc/include/asm/pgtable_64.h

@@ -693,6 +693,7 @@ static inline unsigned long pmd_dirty(pmd_t pmd)
 	return pte_dirty(pte);
 }
 
+#define pmd_young pmd_young
 static inline unsigned long pmd_young(pmd_t pmd)
 {
 	pte_t pte = __pte(pmd_val(pmd));

arch/x86/include/asm/pgtable.h

@@ -139,6 +139,7 @@ static inline int pmd_dirty(pmd_t pmd)
 	return pmd_flags(pmd) & _PAGE_DIRTY;
 }
 
+#define pmd_young pmd_young
 static inline int pmd_young(pmd_t pmd)
 {
 	return pmd_flags(pmd) & _PAGE_ACCESSED;

include/linux/pgtable.h

@@ -165,6 +165,13 @@ static inline pte_t *virt_to_kpte(unsigned long vaddr)
 	return pmd_none(*pmd) ? NULL : pte_offset_kernel(pmd, vaddr);
 }
 
+#ifndef pmd_young
+static inline int pmd_young(pmd_t pmd)
+{
+	return 0;
+}
+#endif
+
 #ifndef __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS
 extern int ptep_set_access_flags(struct vm_area_struct *vma,
 				 unsigned long address, pte_t *ptep,