Re: [PATCH v2 1/1] mm/vmscan: avoid split PMD-mapped THP during shrink_folio_list()

[David Hildenbrand]

> > I was wondering if we can better integrate that into the pagewalk below.
> >
> > That is, don't do the TTU_SPLIT_HUGE_PMD immediately. Start the pagewalk
> > first. If we walk a PMD, try to unmap it. Only if that fails, split it.
>
> Nice. Thanks for the suggestion!
> I'll work on integrating it into the pagewalk as you suggested.
>
> > Less working on "vma + address" and instead directly on PMDs.
>
> Yes, some of the work on "vma + address" can be avoided :)

Doing the conditional split while in the pagewalk will be the 
interesting bit to sort out (we temporarily have to drop the PTL and 
start once again from that now-PTE-mapped page table). But it should be 
a reasonable thing to have.

Please let us know if you run into bigger issues with that!

See walk_pmd_range() as an inspiration where we call split_huge_pmd().

--
Cheers,

David / dhildenb