linux-kernel - Re: [PATCH v2 1/8] mm: migrate: remove PageTransHuge check in numamigrate_isolate

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Date:   Mon, 21 Aug 2023 13:38:35 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Kefeng Wang <wangkefeng.wang@...wei.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, ying.huang@...el.com,
        david@...hat.com, Zi Yan <ziy@...dia.com>,
        Mike Kravetz <mike.kravetz@...cle.com>, hughd@...gle.com
Subject: Re: [PATCH v2 1/8] mm: migrate: remove PageTransHuge check in
 numamigrate_isolate_page()

On Mon, Aug 21, 2023 at 07:56:17PM +0800, Kefeng Wang wrote:
> Since we begin to convert the numa migration code to use folio, which
> could let us to handle arbitrary sizes of folio, so drop assert that
> we only support PageTransHuge page(PMD size) when order > 0.

Have you looked at the implementation of PageTransHuge()?  Your
description doesn't match what the code does.

> Suggested-by: Matthew Wilcox (Oracle) <willy@...radead.org>
> Signed-off-by: Kefeng Wang <wangkefeng.wang@...wei.com>
> ---
>  mm/migrate.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/mm/migrate.c b/mm/migrate.c
> index b7fa020003f3..646d8ee7f102 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -2483,8 +2483,6 @@ static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
>  	int nr_pages = thp_nr_pages(page);
>  	int order = compound_order(page);
>  
> -	VM_BUG_ON_PAGE(order && !PageTransHuge(page), page);
> -
>  	/* Do not migrate THP mapped by multiple processes */
>  	if (PageTransHuge(page) && total_mapcount(page) > 1)
>  		return 0;
> -- 
> 2.41.0
> 
>