linux-kernel - Re: [PATCH v3 2/4] mm/migration: remove unneeded lock page and PageMovable check

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Message-ID: <Yo3p9qhDWmcoJXV6@localhost.localdomain>
Date:   Wed, 25 May 2022 10:33:58 +0200
From:   Oscar Salvador <osalvador@...e.de>
To:     Miaohe Lin <linmiaohe@...wei.com>
Cc:     akpm@...ux-foundation.org, mike.kravetz@...cle.com,
        naoya.horiguchi@....com, peterx@...hat.com, apopple@...dia.com,
        ying.huang@...el.com, david@...hat.com, songmuchun@...edance.com,
        hch@....de, dhowells@...hat.com, cl@...ux.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/4] mm/migration: remove unneeded lock page and
 PageMovable check

On Wed, May 25, 2022 at 04:18:20PM +0800, Miaohe Lin wrote:
> When non-lru movable page was freed from under us, __ClearPageMovable must
> have been done.  So we can remove unneeded lock page and PageMovable check
> here. Also free_pages_prepare() will clear PG_isolated for us, so we can
> further remove ClearPageIsolated as suggested by David.
> 
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
> Reviewed-by: Christoph Hellwig <hch@....de>

Reviewed-by: Oscar Salvador <osalvador@...e.de>

> ---
>  mm/migrate.c | 9 ++-------
>  1 file changed, 2 insertions(+), 7 deletions(-)
> 
> diff --git a/mm/migrate.c b/mm/migrate.c
> index e88ebb88fa6f..337336115e43 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1090,15 +1090,10 @@ static int unmap_and_move(new_page_t get_new_page,
>  		return -ENOSYS;
>  
>  	if (page_count(page) == 1) {
> -		/* page was freed from under us. So we are done. */
> +		/* Page was freed from under us. So we are done. */
>  		ClearPageActive(page);
>  		ClearPageUnevictable(page);
> -		if (unlikely(__PageMovable(page))) {
> -			lock_page(page);
> -			if (!PageMovable(page))
> -				ClearPageIsolated(page);
> -			unlock_page(page);
> -		}
> +		/* free_pages_prepare() will clear PG_isolated. */
>  		goto out;
>  	}
>  
> -- 
> 2.23.0
> 
> 

-- 
Oscar Salvador
SUSE Labs