powerpc/mm: Reinstate ARCH_FORCE_MAX_ORDER ranges

Commit 1e8fed873e74 ("powerpc: drop ranges for definition of
ARCH_FORCE_MAX_ORDER") removed the limits on the possible values for

However removing the ranges entirely causes some common work flows to
break. For example building a defconfig (which uses 64K pages), changing
the page size to 4K, and rebuilding used to work, because
ARCH_FORCE_MAX_ORDER would be clamped to 12 by the ranges.

With the ranges removed it creates a kernel that builds but crashes at
  kernel BUG at mm/huge_memory.c:470!
  Oops: Exception in kernel mode, sig: 5 [#1]
  NIP hugepage_init+0x9c/0x278
  LR  do_one_initcall+0x80/0x320
  Call Trace:

The reasoning for removing the ranges was that some of the values were
too large. So take that into account and limit the maximums to 10 which
is the default max, except for the 4K case which uses 12.

Fixes: 1e8fed873e74 ("powerpc: drop ranges for definition of ARCH_FORCE_MAX_ORDER")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230519113806.370635-1-mpe@ellerman.id.au

1 file changed