linux-kernel - Re: [PATCH v9 02/14] introduce collapse_single_pmd to unify khugepaged and madvise

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Message-ID: <d8474462-a90d-4b35-bfd2-dc1a641cc837@redhat.com>
Date: Tue, 15 Jul 2025 17:53:56 +0200
From: David Hildenbrand <david@...hat.com>
To: Nico Pache <npache@...hat.com>, linux-mm@...ck.org,
 linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org
Cc: ziy@...dia.com, baolin.wang@...ux.alibaba.com,
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Subject: Re: [PATCH v9 02/14] introduce collapse_single_pmd to unify
 khugepaged and madvise_collapse

On 14.07.25 02:31, Nico Pache wrote:
> The khugepaged daemon and madvise_collapse have two different
> implementations that do almost the same thing.
> 
> Create collapse_single_pmd to increase code reuse and create an entry
> point to these two users.
> 
> Refactor madvise_collapse and collapse_scan_mm_slot to use the new
> collapse_single_pmd function. This introduces a minor behavioral change
> that is most likely an undiscovered bug. The current implementation of
> khugepaged tests collapse_test_exit_or_disable before calling
> collapse_pte_mapped_thp, but we weren't doing it in the madvise_collapse
> case. By unifying these two callers madvise_collapse now also performs
> this check.
> 
> Reviewed-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> Signed-off-by: Nico Pache <npache@...hat.com>
> ---
>   mm/khugepaged.c | 95 +++++++++++++++++++++++++------------------------
>   1 file changed, 49 insertions(+), 46 deletions(-)
> 
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index eb0babb51868..47a80638af97 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -2362,6 +2362,50 @@ static int collapse_scan_file(struct mm_struct *mm, unsigned long addr,
>   	return result;
>   }
>   
> +/*
> + * Try to collapse a single PMD starting at a PMD aligned addr, and return
> + * the results.
> + */
> +static int collapse_single_pmd(unsigned long addr,
> +				   struct vm_area_struct *vma, bool *mmap_locked,
> +				   struct collapse_control *cc)

Nit: we tend to use two-tabs indent here.

Nice cleanup!

Acked-by: David Hildenbrand <david@...hat.com>

-- 
Cheers,

David / dhildenb