Re: [PATCH v9 mm-new 03/11] mm: thp: add support for BPF based THP order selection

[Alexei Starovoitov]

On Mon, Sep 29, 2025 at 10:59 PM Yafang Shao <laoar.shao@xxxxxxxxx> wrote:
>
> +unsigned long bpf_hook_thp_get_orders(struct vm_area_struct *vma,
> +                                     enum tva_type type,
> +                                     unsigned long orders)
> +{
> +       thp_order_fn_t *bpf_hook_thp_get_order;
> +       int bpf_order;
> +
> +       /* No BPF program is attached */
> +       if (!test_bit(TRANSPARENT_HUGEPAGE_BPF_ATTACHED,
> +                     &transparent_hugepage_flags))
> +               return orders;
> +
> +       rcu_read_lock();
> +       bpf_hook_thp_get_order = rcu_dereference(bpf_thp.thp_get_order);
> +       if (WARN_ON_ONCE(!bpf_hook_thp_get_order))
> +               goto out;
> +
> +       bpf_order = bpf_hook_thp_get_order(vma, type, orders);
> +       orders &= BIT(bpf_order);
> +
> +out:
> +       rcu_read_unlock();
> +       return orders;
> +}

I thought I explained it earlier.
Nack to a single global prog approach.

The logic must accommodate multiple programs per-container
or any other way from the beginning.
If cgroup based scoping doesn't fit use per process tree scoping.