Re: [PATCH] mm/spase: never partially remove memmap for early section

[Dan Williams]

On Wed, Jun 24, 2020 at 3:44 PM Wei Yang
<richard.weiyang@xxxxxxxxxxxxxxxxx> wrote:
[..]
> >So, you are right that there is a mismatch here, but I think the
> >comprehensive fix is to allow early sections to be partially
> >depopulated/repopulated rather than have section_activate() and
> >section_deacticate() special case early sections. The special casing
> >is problematic in retrospect as section_deactivate() can't be
> >maintained without understand special rules in section_activate().
>
> Hmm... This means we need to adjust pfn_valid() too, which always return true
> for early sections.

Right, rather than carry workarounds in 3 locations, and the bug that
has resulted from then getting out of sync, just teach early section
mapping to allow for the subsection populate/depopulate.