linux-kernel - Re: [PATCH v1 2/2] mm/page_isolation: fixup isolate_single_pageblock() comment regarding splitting free pages

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Message-ID: <987BDF68-11E7-4CE3-B5C1-9F18B8E569C7@nvidia.com>
Date: Fri, 06 Dec 2024 11:59:51 -0500
From: Zi Yan <ziy@...dia.com>
To: David Hildenbrand <david@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
 Andrew Morton <akpm@...ux-foundation.org>, Vlastimil Babka <vbabka@...e.cz>,
 Yu Zhao <yuzhao@...gle.com>
Subject: Re: [PATCH v1 2/2] mm/page_isolation: fixup
 isolate_single_pageblock() comment regarding splitting free pages

On 6 Dec 2024, at 4:59, David Hildenbrand wrote:

> Let's fixup the comment, documenting how free_one_page_maybe_split()
> comes into play.
>
> Signed-off-by: David Hildenbrand <david@...hat.com>
> ---
>  mm/page_isolation.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/mm/page_isolation.c b/mm/page_isolation.c
> index c608e9d728655..63fddf283e681 100644
> --- a/mm/page_isolation.c
> +++ b/mm/page_isolation.c
> @@ -298,11 +298,10 @@ __first_valid_page(unsigned long pfn, unsigned long nr_pages)
>   * pagelbocks.
>   * [      MAX_PAGE_ORDER         ]
>   * [  pageblock0  |  pageblock1  ]
> - * When either pageblock is isolated, if it is a free page, the page is not
> - * split into separate migratetype lists, which is supposed to; if it is an
> - * in-use page and freed later, __free_one_page() does not split the free page
> - * either. The function handles this by splitting the free page or migrating
> - * the in-use page then splitting the free page.
> + * When either pageblock is isolated, if it is an in-use page and freed later,
> + * __free_one_page_maybe_split() will split the free page if required. If the
> + * page is already free, this function handles this by splitting the free page
> + * through move_freepages_block_isolate()->__free_one_page_maybe_split().
>   */
>  static int isolate_single_pageblock(unsigned long boundary_pfn, int flags,
>  		bool isolate_before, bool skip_isolation, int migratetype)

LGTM. Reviewed-by: Zi Yan <ziy@...dia.com>

Best Regards,
Yan, Zi