[RFC V2] mm: Enable generic pfn_valid() to handle early sections with memmap holes

[Anshuman Khandual]

On 4/22/21 3:12 PM, Mike Rapoport wrote:
> The "generic" pfn_valid() is only available with CONFIG_SPARSEMEM.
> With FLATMEM it's wild west:
> 
> $ git grep -w "define pfn_valid" arch/*/include/asm/ | wc -l
> 22
> 
> This would actually mean that we still need arm64::pfn_valid() for the
> FLATMEM case.

SPARSEMEM would be the only memory model going forward.

https://patchwork.kernel.org/project/linux-arm-kernel/patch/20210420093559.23168-1-catalin.marinas@arm.com/