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 <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Nicholas Piggin <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Geert Uytterhoeven <[email protected]>
Fixes: c742199a014d ("mm/pgtable: add stubs for {pmd/pub}_{set/clear}_huge")
Signed-off-by: Jonathan Marek <[email protected]>
Reviewed-by: Ard Biesheuvel <[email protected]>
Acked-by: Marc Zyngier <[email protected]>
[mpe: Fold in 8xx.c changes from Christophe and mention in change log]
Signed-off-by: Michael Ellerman <[email protected]>
Link: https://lore.kernel.org/linux-arm-kernel/CAMuHMdXShORDox-xxaeUfDW3wx2PeggFSqhVSHVZNKCGK-y_vQ@mail.gmail.com/
Link: https://lore.kernel.org/r/[email protected]
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Will Deacon <[email protected]>

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