Re: [PATCH hotfix v2 2/2] mm/thp: fix deferred split unqueue naming and locking

[David Hildenbrand <david@redhat.com>]

>> https://lkml.kernel.org/r/20241025012304.2473312-3-shakeel.butt@linux.dev
>>
>> So I wonder ... as a quick fix should we simply handle it like the code
>> further down where we refuse PTE-mapped large folios completely?
> 
> (I went through the same anxiety attack as you did, wondering what
> happens to the large-but-not-PMD-large folios: then noticed it's safe
> as you did.  The v1 commit message had a paragraph pondering whether
> the deprecated code will need a patch to extend it for the new feature:
> but once Shakeel posted the ripout, I ripped out that paragraph -
> no longer any need for an answer.)

Ah, missed that.

> 
>>
>> "ignore such a partial THP and keep it in original memcg"
>>
>> ...
>>
>> and simply skip this folio similarly? I mean, it's a corner case either way.
> 
> I certainly considered that option: it's known to give up like that
> for many reasons.  But my thinking (in the commit message) was "Not ideal,
> but moving charge has been requested, and khugepaged should repair the THP
> later" - if someone is still using move_charge_at_immigrate, I thought
> this change would generate fewer surprises - that huge charge likely
> to be moved as it used to be.

Fair enough, I'd have kept it simpler for this almost-dead code :)

Looks good to me, thanks!

Acked-by: David Hildenbrand <david@redhat.com>

-- 
Cheers,

David / dhildenb