Re: [RFC PATCH v3 3/5] mm, thp: add bpf thp hook to determine thp reclaimer

[Usama Arif <usamaarif642@gmail.com>]

On 08/06/2025 08:35, Yafang Shao wrote:
> A new hook, bpf_thp_gfp_mask(), is introduced to determine whether memory
> reclamation is being performed by the current task or by kswapd.
> 
> Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> ---
>  include/linux/huge_mm.h | 5 +++++
>  mm/huge_memory.c        | 5 +++++
>  2 files changed, 10 insertions(+)
> 
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index db2eadd3f65b..6a40ebf25f5c 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -198,6 +198,11 @@ static inline int bpf_thp_allocator(unsigned long vm_flags,
>  	return THP_ALLOC_KHUGEPAGED | THP_ALLOC_CURRENT;
>  }
>  
> +static inline gfp_t bpf_thp_gfp_mask(bool vma_madvised)
> +{
> +	return 0;
> +}
> +
>  static inline int highest_order(unsigned long orders)
>  {
>  	return fls_long(orders) - 1;
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index d3e66136e41a..81c1711d13fa 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -1280,6 +1280,11 @@ static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf)
>  gfp_t vma_thp_gfp_mask(struct vm_area_struct *vma)
>  {
>  	const bool vma_madvised = vma && (vma->vm_flags & VM_HUGEPAGE);
> +	gfp_t gfp_mask;
> +
> +	gfp_mask = bpf_thp_gfp_mask(vma_madvised);


I am guessing bpf_thp_gfp_mask returns 0, as its something yet to be implemented, 
but I really dont understand what this patch is supposed to do.


> +	if (gfp_mask)
> +		return gfp_mask;
>  
>  	/* Always do synchronous compaction */
>  	if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))