mm/pgtable: add stubs for {pmd/pub}_{set/clear}_huge

For architectures with no PMD and/or no PUD, add stubs similar to what we
have for architectures without P4D.

[[e-mail]: arm64: define only {pud/pmd}_{set/clear}_huge when useful]
Link: https://lkml.kernel.org/r/73ec95f4[e-mail]
[[e-mail]: x86: define only {pud/pmd}_{set/clear}_huge when useful]
Link: https://lkml.kernel.org/r/7fbf1b6b[e-mail]

Link: https://lkml.kernel.org/r/5ac59764[e-mail]
Signed-off-by: Christophe Leroy <[e-mail]>
Cc: Benjamin Herrenschmidt <[e-mail]>
Cc: Michael Ellerman <[e-mail]>
Cc: Mike Kravetz <[e-mail]>
Cc: Mike Rapoport <[e-mail]>
Cc: Nicholas Piggin <[e-mail]>
Cc: Paul Mackerras <[e-mail]>
Cc: Uladzislau Rezki <[e-mail]>
Cc: Naresh Kamboju <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/arm64/mm/mmu.c

···
 	return dt_virt;
 }
 
+#if CONFIG_PGTABLE_LEVELS > 3
 int pud_set_huge(pud_t *pudp, phys_addr_t phys, pgprot_t prot)
 {
 	pud_t new_pud = pfn_pud(__phys_to_pfn(phys), mk_pud_sect_prot(prot));
···
 	return 1;
 }
 
+int pud_clear_huge(pud_t *pudp)
+{
+	if (!pud_sect(READ_ONCE(*pudp)))
+		return 0;
+	pud_clear(pudp);
+	return 1;
+}
+#endif
+
+#if CONFIG_PGTABLE_LEVELS > 2
 int pmd_set_huge(pmd_t *pmdp, phys_addr_t phys, pgprot_t prot)
 {
 	pmd_t new_pmd = pfn_pmd(__phys_to_pfn(phys), mk_pmd_sect_prot(prot));
···
 	return 1;
 }
 
-int pud_clear_huge(pud_t *pudp)
-{
-	if (!pud_sect(READ_ONCE(*pudp)))
-		return 0;
-	pud_clear(pudp);
-	return 1;
-}
-
 int pmd_clear_huge(pmd_t *pmdp)
 {
 	if (!pmd_sect(READ_ONCE(*pmdp)))
···
 	pmd_clear(pmdp);
 	return 1;
 }
+#endif
 
 int pmd_free_pte_page(pmd_t *pmdp, unsigned long addr)
 {

arch/x86/mm/pgtable.c

···
 }
 #endif
 
+#if CONFIG_PGTABLE_LEVELS > 3
 /**
  * pud_set_huge - setup kernel PUD mapping
  *
···
 }
 
 /**
+ * pud_clear_huge - clear kernel PUD mapping when it is set
+ *
+ * Returns 1 on success and 0 on failure (no PUD map is found).
+ */
+int pud_clear_huge(pud_t *pud)
+{
+	if (pud_large(*pud)) {
+		pud_clear(pud);
+		return 1;
+	}
+
+	return 0;
+}
+#endif
+
+#if CONFIG_PGTABLE_LEVELS > 2
+/**
  * pmd_set_huge - setup kernel PMD mapping
  *
  * See text over pud_set_huge() above.
···
 }
 
 /**
- * pud_clear_huge - clear kernel PUD mapping when it is set
- *
- * Returns 1 on success and 0 on failure (no PUD map is found).
- */
-int pud_clear_huge(pud_t *pud)
-{
-	if (pud_large(*pud)) {
-		pud_clear(pud);
-		return 1;
-	}
-
-	return 0;
-}
-
-/**
  * pmd_clear_huge - clear kernel PMD mapping when it is set
  *
  * Returns 1 on success and 0 on failure (no PMD map is found).
···
 
 	return 0;
 }
+#endif
 
 #ifdef CONFIG_X86_64
 /**

include/linux/pgtable.h

···
 }
 #endif /* !__PAGETABLE_P4D_FOLDED */
 
+#ifndef __PAGETABLE_PUD_FOLDED
 int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot);
-int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot);
 int pud_clear_huge(pud_t *pud);
+#else
+static inline int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot)
+{
+	return 0;
+}
+static inline int pud_clear_huge(pud_t *pud)
+{
+	return 0;
+}
+#endif /* !__PAGETABLE_PUD_FOLDED */
+
+#ifndef __PAGETABLE_PMD_FOLDED
+int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot);
 int pmd_clear_huge(pmd_t *pmd);
+#else
+static inline int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot)
+{
+	return 0;
+}
+static inline int pmd_clear_huge(pmd_t *pmd)
+{
+	return 0;
+}
+#endif /* !__PAGETABLE_PMD_FOLDED */
+
 int p4d_free_pud_page(p4d_t *p4d, unsigned long addr);
 int pud_free_pmd_page(pud_t *pud, unsigned long addr);
 int pmd_free_pte_page(pmd_t *pmd, unsigned long addr);