linux-kernel - Re: [PATCH v2 1/2] mm: khugepaged: convert set_huge

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Message-ID: <4decbf69-23cd-4717-ad9b-3315a9df7b37@linux.alibaba.com>
Date: Mon, 12 May 2025 10:17:26 +0800
From: Baolin Wang <baolin.wang@...ux.alibaba.com>
To: David Hildenbrand <david@...hat.com>, akpm@...ux-foundation.org,
 willy@...radead.org
Cc: hannes@...xchg.org, lorenzo.stoakes@...cle.com, Liam.Howlett@...cle.com,
 npache@...hat.com, ryan.roberts@....com, dev.jain@....com, ziy@...dia.com,
 vbabka@...e.cz, rppt@...nel.org, surenb@...gle.com, mhocko@...e.com,
 linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] mm: khugepaged: convert set_huge_pmd() to take a
 folio



On 2025/5/9 22:58, David Hildenbrand wrote:
>> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
>> index b04b6a770afe..aca66e7f4fd9 100644
>> --- a/mm/khugepaged.c
>> +++ b/mm/khugepaged.c
>> @@ -1467,7 +1467,7 @@ static void collect_mm_slot(struct 
>> khugepaged_mm_slot *mm_slot)
>>   #ifdef CONFIG_SHMEM
>>   /* hpage must be locked, and mmap_lock must be held */
> 
> ^ that comment probably needs some love.

Ah, missed that. Will update the comments in next version.

> 
>>   static int set_huge_pmd(struct vm_area_struct *vma, unsigned long addr,
>> -            pmd_t *pmdp, struct page *hpage)
>> +            pmd_t *pmdp, struct folio *folio)
>>   {
>>       struct vm_fault vmf = {
>>           .vma = vma,
>> @@ -1476,13 +1476,12 @@ static int set_huge_pmd(struct vm_area_struct 
>> *vma, unsigned long addr,
>>           .pmd = pmdp,
>>       };
>> -    VM_BUG_ON(!PageTransHuge(hpage));
>>       mmap_assert_locked(vma->vm_mm);
>> -    if (do_set_pmd(&vmf, hpage))
>> +    if (do_set_pmd(&vmf, &folio->page))
>>           return SCAN_FAIL;
>> -    get_page(hpage);
>> +    folio_get(folio);
>>       return SCAN_SUCCEED;
>>   }
>> @@ -1689,7 +1688,7 @@ int collapse_pte_mapped_thp(struct mm_struct 
>> *mm, unsigned long addr,
>>   maybe_install_pmd:
>>       /* step 5: install pmd entry */
>>       result = install_pmd
>> -            ? set_huge_pmd(vma, haddr, pmd, &folio->page)
>> +            ? set_huge_pmd(vma, haddr, pmd, folio)
> 
> Wondering why we are not passing in the folio+page pair in here as well. 
> I assume in the foreseeable future this code will not be able to work 
> with folios large than PMDs?

OK. Will do in next version.

> Apart from that LGTM.
> 
> Acked-by: David Hildenbrand <david@...hat.com>

Thanks.