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

This reverts commit c742199a014de23ee92055c2473d91fe5561ffdf.

c742199a014d ("mm/pgtable: add stubs for {pmd/pub}_{set/clear}_huge")
breaks arm64 in at least two ways for configurations where PUD or PMD
folding occur:

1. We no longer install huge-vmap mappings and silently fall back to
page-granular entries, despite being able to install block entries
at what is effectively the PGD level.

2. If the linear map is backed with block mappings, these will now
silently fail to be created in alloc_init_pud(), causing a panic
early during boot.

The pgtable selftests caught this, although a fix has not been
forthcoming and Christophe is AWOL at the moment, so just revert the
change for now to get a working -rc3 on which we can queue patches for
5.15.

A simple revert breaks the build for 32-bit PowerPC 8xx machines, which
rely on the default function definitions when the corresponding
page-table levels are folded, since commit a6a8f7c4aa7e ("powerpc/8xx:
add support for huge pages on VMAP and VMALLOC"), eg:

powerpc64-linux-ld: mm/vmalloc.o: in function `vunmap_pud_range':
linux/mm/vmalloc.c:362: undefined reference to `pud_clear_huge'

To avoid that, add stubs for pud_clear_huge() and pmd_clear_huge() in
arch/powerpc/mm/nohash/8xx.c as suggested by Christophe.

Cc: Christophe Leroy <[e-mail]>
Cc: Catalin Marinas <[e-mail]>
Cc: Andrew Morton <[e-mail]>
Cc: Nicholas Piggin <[e-mail]>
Cc: Mike Rapoport <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Geert Uytterhoeven <[e-mail]>
Fixes: c742199a014d ("mm/pgtable: add stubs for {pmd/pub}_{set/clear}_huge")
Signed-off-by: Jonathan Marek <[e-mail]>
Reviewed-by: Ard Biesheuvel <[e-mail]>
Acked-by: Marc Zyngier <[e-mail]>
[mpe: Fold in 8xx.c changes from Christophe and mention in change log]
Signed-off-by: Michael Ellerman <[e-mail]>
Link: https://lore.kernel.org/linux-arm-kernel/[e-mail]/
Link: https://lore.kernel.org/r/[e-mail]
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Will Deacon <[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/powerpc/mm/nohash/8xx.c

···
 	mtspr(SPRN_MD_AP, MD_APG_KUAP);
 }
 #endif
+
+int pud_clear_huge(pud_t *pud)
+{
+	 return 0;
+}
+
+int pmd_clear_huge(pmd_t *pmd)
+{
+	 return 0;
+}

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 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 pud_clear_huge(pud_t *pud);
 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);