Re: [PATCH v2 08/46] hugetlb: add HugeTLB HGM enablement helpers

[Mina Almasry]

On Fri, Feb 17, 2023 at 4:28 PM James Houghton <jthoughton@xxxxxxxxxx> wrote:
>
> hugetlb_hgm_eligible indicates that a VMA is eligible to have HGM
> explicitly enabled via MADV_SPLIT, and hugetlb_hgm_enabled indicates
> that HGM has been enabled.
>
> Signed-off-by: James Houghton <jthoughton@xxxxxxxxxx>

Only nits:
Reviewed-by: Mina Almasry <almasrymina@xxxxxxxxxx>

>
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index 7c977d234aba..efd2635a87f5 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -1211,6 +1211,20 @@ static inline void hugetlb_unregister_node(struct node *node)
>  }
>  #endif /* CONFIG_HUGETLB_PAGE */
>
> +#ifdef CONFIG_HUGETLB_HIGH_GRANULARITY_MAPPING
> +bool hugetlb_hgm_enabled(struct vm_area_struct *vma);
> +bool hugetlb_hgm_eligible(struct vm_area_struct *vma);
> +#else
> +static inline bool hugetlb_hgm_enabled(struct vm_area_struct *vma)
> +{
> +       return false;
> +}
> +static inline bool hugetlb_hgm_eligible(struct vm_area_struct *vma)
> +{
> +       return false;
> +}
> +#endif
> +
>  static inline spinlock_t *huge_pte_lock(struct hstate *h,
>                                         struct mm_struct *mm, pte_t *pte)
>  {
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 6c008c9de80e..0576dcc98044 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -7004,6 +7004,10 @@ static bool pmd_sharing_possible(struct vm_area_struct *vma)
>  #ifdef CONFIG_USERFAULTFD
>         if (uffd_disable_huge_pmd_share(vma))
>                 return false;
> +#endif
> +#ifdef CONFIG_HUGETLB_HIGH_GRANULARITY_MAPPING
> +       if (hugetlb_hgm_enabled(vma))
> +               return false;
>  #endif
>         /*
>          * Only shared VMAs can share PMDs.
> @@ -7267,6 +7271,18 @@ __weak unsigned long hugetlb_mask_last_page(struct hstate *h)
>
>  #endif /* CONFIG_ARCH_WANT_GENERAL_HUGETLB */
>
> +#ifdef CONFIG_HUGETLB_HIGH_GRANULARITY_MAPPING
> +bool hugetlb_hgm_eligible(struct vm_area_struct *vma)

I think the other function you named pmd_sharing_possible(), I suggest
hugetlb_hgm_possible() for some consistency.

> +{
> +       /* All shared VMAs may have HGM. */

I think this is a redundant comment.

> +       return vma && (vma->vm_flags & VM_MAYSHARE);
> +}
> +bool hugetlb_hgm_enabled(struct vm_area_struct *vma)
> +{
> +       return vma && (vma->vm_flags & VM_HUGETLB_HGM);
> +}
> +#endif /* CONFIG_HUGETLB_HIGH_GRANULARITY_MAPPING */
> +
>  /*
>   * These functions are overwritable if your architecture needs its own
>   * behavior.
> --
> 2.39.2.637.g21b0678d19-goog
>