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References: <20230218002819.1486479-1-jthoughton@google.com> <20230218002819.1486479-9-jthoughton@google.com>
In-Reply-To: <20230218002819.1486479-9-jthoughton@google.com>
From:   Mina Almasry <almasrymina@google.com>
Date:   Fri, 17 Feb 2023 17:40:13 -0800
Message-ID: <CAHS8izM8xcOg8384-692O2Aaj7xiOO=GYWH=g7-RGES=2tNxhw@mail.gmail.com>
Subject: Re: [PATCH v2 08/46] hugetlb: add HugeTLB HGM enablement helpers
To:     James Houghton <jthoughton@google.com>
Cc:     Mike Kravetz <mike.kravetz@oracle.com>,
        Muchun Song <songmuchun@bytedance.com>,
        Peter Xu <peterx@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        David Hildenbrand <david@redhat.com>,
        David Rientjes <rientjes@google.com>,
        Axel Rasmussen <axelrasmussen@google.com>,
        "Zach O'Keefe" <zokeefe@google.com>,
        Manish Mishra <manish.mishra@nutanix.com>,
        Naoya Horiguchi <naoya.horiguchi@nec.com>,
        "Dr . David Alan Gilbert" <dgilbert@redhat.com>,
        "Matthew Wilcox (Oracle)" <willy@infradead.org>,
        Vlastimil Babka <vbabka@suse.cz>,
        Baolin Wang <baolin.wang@linux.alibaba.com>,
        Miaohe Lin <linmiaohe@huawei.com>,
        Yang Shi <shy828301@gmail.com>,
        Frank van der Linden <fvdl@google.com>,
        Jiaqi Yan <jiaqiyan@google.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
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On Fri, Feb 17, 2023 at 4:28=E2=80=AFPM James Houghton <jthoughton@google.c=
om> 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@google.com>

Only nits:
Reviewed-by: Mina Almasry <almasrymina@google.com>

>
> 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_st=
ruct *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
>