Re: [PATCH v4 4/4] mm: huge_memory: use folio_needs_prot_numa() for pmd folio

[Kefeng Wang <wangkefeng.wang@huawei.com>]

On 2025/10/20 23:18, Kefeng Wang wrote:
> 
> 
> On 2025/10/20 21:23, David Hildenbrand wrote:
>>
>>>>           /*
>>>>            * Avoid trapping faults against the zero page. The read-only
>>>>            * data is likely to be read-cached on the local CPU and
>>>> @@ -2490,19 +2490,13 @@ int change_huge_pmd(struct mmu_gather *tlb, 
>>>> struct vm_area_struct *vma,
>>>>           if (pmd_protnone(*pmd))
>>>>               goto unlock;
>>>>
>>>> -        folio = pmd_folio(*pmd);
>>>> -        toptier = node_is_toptier(folio_nid(folio));
>>>> -        /*
>>>> -         * Skip scanning top tier node if normal numa
>>>> -         * balancing is disabled
>>>> -         */
>>>> -        if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_NORMAL) &&
>>>> -            toptier)
>>>> -            goto unlock;
>>>> +        /* Get target node for single threaded private VMAs */
>>>> +        if (!(vma->vm_flags & VM_SHARED) &&
>>>> +            atomic_read(&vma->vm_mm->mm_users) == 1)
>>>> +            target_node = numa_node_id();
>>>
>>> This is duplicated in both callers, and only used by 
>>> folio_needs_prot_numa(),
>>> why not abstract this to the function also?
>>
>> There was a discussion on that in v3 I think where I asked the same 
>> question.
>>
> 
> Yes, it is in v1, for pte, we could avoid 512 times check and the
> numa_node_id(), so we leave it as is.
> 

If no objection, I won't change this and will send a new version with

1) kerneldoc refresh for folio_need_prot_numa, per Lorenzo
2) update the changelog of this one, per David

Thanks