On 08/06/2025 08:35, Yafang Shao wrote:
> A new hook bpf_thp_allocator() is added to determine if the THP is
> allocated by khugepaged or by the current task.
I would add in the summary why we need this. I am assuming I will find out
when reviewing the next few patches, but would be good to know here.
>
> Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
> ---
> include/linux/huge_mm.h | 10 ++++++++++
> mm/khugepaged.c | 2 ++
> 2 files changed, 12 insertions(+)
>
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index 2f190c90192d..db2eadd3f65b 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -190,6 +190,14 @@ static inline bool hugepage_global_always(void)
> (1<<TRANSPARENT_HUGEPAGE_FLAG);
> }
>
> +#define THP_ALLOC_KHUGEPAGED (1 << 1)
> +#define THP_ALLOC_CURRENT (1 << 2)
> +static inline int bpf_thp_allocator(unsigned long vm_flags,
> + unsigned long tva_flags)
> +{
> + return THP_ALLOC_KHUGEPAGED | THP_ALLOC_CURRENT;
You dont use either vm_flags or tva_flags in this function?
I am guessing you wanted to check if these bits are set here?
But you dont seem to be setting these flags anywhere? I am guessing
its in a future patch. If it is, I would move the setting of these bits
here as its confusing to only see the check without knowing where its
I feel this patch is broken and needs to be rewritten.
> +}
> +
> static inline int highest_order(unsigned long orders)
> {
> return fls_long(orders) - 1;
> @@ -290,6 +298,8 @@ unsigned long thp_vma_allowable_orders(struct vm_area_struct *vma,
> if ((tva_flags & TVA_ENFORCE_SYSFS) && vma_is_anonymous(vma)) {
> unsigned long mask = READ_ONCE(huge_anon_orders_always);
>
> + if (!(bpf_thp_allocator(vm_flags, tva_flags) & THP_ALLOC_CURRENT))
> + return 0;
I am assuming that this is the point to check for allocation, but thp_vma_allowable_orders
is not just used for allocation, its used for in other places as well, like hugepage_vma_revalidate
and swap.
> if (vm_flags & VM_HUGEPAGE)
> mask |= READ_ONCE(huge_anon_orders_madvise);
> if (hugepage_global_always() ||
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 79e208999ddb..18f800fe7335 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -472,6 +472,8 @@ void __khugepaged_enter(struct mm_struct *mm)
> void khugepaged_enter_vma(struct vm_area_struct *vma,
> unsigned long vm_flags)
> {
> + if (!(bpf_thp_allocator(vm_flags, 0) & THP_ALLOC_KHUGEPAGED))
> + return;
> if (!test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags) &&
> hugepage_pmd_enabled()) {
> if (__thp_vma_allowable_orders(vma, vm_flags, TVA_ENFORCE_SYSFS,
