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SubjectRe: [PATCH v1 0/4] smaps / mm/gup: fix gup_can_follow_protnone fallout
On Fri, Jul 28, 2023 at 09:40:54PM +0200, David Hildenbrand wrote:
> Hmm. So three alternatives I see:
>
> 1) Use FOLL_FORCE in follow_page() to unconditionally disable protnone
> checks. Alternatively, have an internal FOLL_NO_PROTNONE flag if we
> don't like that.
>
> 2) Revert the commit and reintroduce unconditional FOLL_NUMA without
> FOLL_FORCE.
>
> 3) Have a FOLL_NUMA that callers like KVM can pass.

I'm afraid 3) means changing numa balancing to opt-in, probably no-go for
any non-kvm gup users as that could start to break there, even if making
smaps/follow_page happy again.

I keep worrying 1) on FOLL_FORCE abuse.

So I keep my vote on 2).

Thanks,

--
Peter Xu

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