linux-kernel - Re: [PATCH v2 3/3] mm/huge_memory: fix kernel-doc comments for folio

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Message-ID: <cc0bc182-8147-42ed-9c2e-d3f4b99bbac2@lucifer.local>
Date: Fri, 17 Oct 2025 10:20:52 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Zi Yan <ziy@...dia.com>
Cc: linmiaohe@...wei.com, david@...hat.com, jane.chu@...cle.com,
        kernel@...kajraghav.com,
        syzbot+e6367ea2fdab6ed46056@...kaller.appspotmail.com,
        syzkaller-bugs@...glegroups.com, akpm@...ux-foundation.org,
        mcgrof@...nel.org, nao.horiguchi@...il.com,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Nico Pache <npache@...hat.com>, Ryan Roberts <ryan.roberts@....com>,
        Dev Jain <dev.jain@....com>, Barry Song <baohua@...nel.org>,
        Lance Yang <lance.yang@...ux.dev>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Wei Yang <richard.weiyang@...il.com>, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v2 3/3] mm/huge_memory: fix kernel-doc comments for
 folio_split() and related.

On Wed, Oct 15, 2025 at 11:34:52PM -0400, Zi Yan wrote:
> try_folio_split_to_order(), folio_split, __folio_split(), and
> __split_unmapped_folio() do not have correct kernel-doc comment format.
> Fix them.
>
> Signed-off-by: Zi Yan <ziy@...dia.com>

Thanks for doing this! LGTM, so:

Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>

> ---
>  include/linux/huge_mm.h | 10 ++++++----
>  mm/huge_memory.c        | 27 +++++++++++++++------------
>  2 files changed, 21 insertions(+), 16 deletions(-)
>
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index 3d9587f40c0b..1a1b9ed50acc 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -382,9 +382,9 @@ static inline int split_huge_page_to_list_to_order(struct page *page, struct lis
>  	return __split_huge_page_to_list_to_order(page, list, new_order, false);
>  }
>
> -/*
> - * try_folio_split_to_order - try to split a @folio at @page to @new_order using
> - * non uniform split.
> +/**
> + * try_folio_split_to_order() - try to split a @folio at @page to @new_order
> + * using non uniform split.
>   * @folio: folio to be split
>   * @page: split to @order at the given page
>   * @new_order: the target split order
> @@ -394,7 +394,7 @@ static inline int split_huge_page_to_list_to_order(struct page *page, struct lis
>   * folios are put back to LRU list. Use min_order_for_split() to get the lower
>   * bound of @new_order.
>   *
> - * Return: 0: split is successful, otherwise split failed.
> + * Return: 0 - split is successful, otherwise split failed.
>   */
>  static inline int try_folio_split_to_order(struct folio *folio,
>  		struct page *page, unsigned int new_order)
> @@ -483,6 +483,8 @@ static inline spinlock_t *pud_trans_huge_lock(pud_t *pud,
>  /**
>   * folio_test_pmd_mappable - Can we map this folio with a PMD?
>   * @folio: The folio to test
> + *
> + * Return: true - @folio can be mapped, false - @folio cannot be mapped.
>   */
>  static inline bool folio_test_pmd_mappable(struct folio *folio)
>  {
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index f308f11dc72f..89179711539e 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -3552,8 +3552,9 @@ static void __split_folio_to_order(struct folio *folio, int old_order,
>  		ClearPageCompound(&folio->page);
>  }
>
> -/*
> - * It splits an unmapped @folio to lower order smaller folios in two ways.
> +/**
> + * __split_unmapped_folio() - splits an unmapped @folio to lower order folios in
> + * two ways: uniform split or non-uniform split.
>   * @folio: the to-be-split folio
>   * @new_order: the smallest order of the after split folios (since buddy
>   *             allocator like split generates folios with orders from @folio's
> @@ -3588,8 +3589,8 @@ static void __split_folio_to_order(struct folio *folio, int old_order,
>   * folio containing @page. The caller needs to unlock and/or free after-split
>   * folios if necessary.
>   *
> - * For !uniform_split, when -ENOMEM is returned, the original folio might be
> - * split. The caller needs to check the input folio.
> + * Return: 0 - successful, <0 - failed (if -ENOMEM is returned, @folio might be
> + * split but not to @new_order, the caller needs to check)
>   */
>  static int __split_unmapped_folio(struct folio *folio, int new_order,
>  		struct page *split_at, struct xa_state *xas,
> @@ -3703,8 +3704,8 @@ bool uniform_split_supported(struct folio *folio, unsigned int new_order,
>  	return true;
>  }
>
> -/*
> - * __folio_split: split a folio at @split_at to a @new_order folio
> +/**
> + * __folio_split() - split a folio at @split_at to a @new_order folio
>   * @folio: folio to split
>   * @new_order: the order of the new folio
>   * @split_at: a page within the new folio
> @@ -3722,7 +3723,7 @@ bool uniform_split_supported(struct folio *folio, unsigned int new_order,
>   * 1. for uniform split, @lock_at points to one of @folio's subpages;
>   * 2. for buddy allocator like (non-uniform) split, @lock_at points to @folio.
>   *
> - * return: 0: successful, <0 failed (if -ENOMEM is returned, @folio might be
> + * Return: 0 - successful, <0 - failed (if -ENOMEM is returned, @folio might be
>   * split but not to @new_order, the caller needs to check)
>   */
>  static int __folio_split(struct folio *folio, unsigned int new_order,
> @@ -4111,14 +4112,13 @@ int __split_huge_page_to_list_to_order(struct page *page, struct list_head *list
>  				unmapped);
>  }
>
> -/*
> - * folio_split: split a folio at @split_at to a @new_order folio
> +/**
> + * folio_split() - split a folio at @split_at to a @new_order folio
>   * @folio: folio to split
>   * @new_order: the order of the new folio
>   * @split_at: a page within the new folio
> - *
> - * return: 0: successful, <0 failed (if -ENOMEM is returned, @folio might be
> - * split but not to @new_order, the caller needs to check)
> + * @list: after-split folios are added to @list if not null, otherwise to LRU
> + *        list
>   *
>   * It has the same prerequisites and returns as
>   * split_huge_page_to_list_to_order().
> @@ -4132,6 +4132,9 @@ int __split_huge_page_to_list_to_order(struct page *page, struct list_head *list
>   * [order-4, {order-3}, order-3, order-5, order-6, order-7, order-8].
>   *
>   * After split, folio is left locked for caller.
> + *
> + * Return: 0 - successful, <0 - failed (if -ENOMEM is returned, @folio might be
> + * split but not to @new_order, the caller needs to check)
>   */
>  int folio_split(struct folio *folio, unsigned int new_order,
>  		struct page *split_at, struct list_head *list)
> --
> 2.51.0
>