linux-kernel - Re: [PATCH 01/16] mm/migration: remove unneeded local variable mapping

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Message-ID: <87bkyi7c8f.fsf@yhuang6-desk2.ccr.corp.intel.com>
Date:   Mon, 07 Mar 2022 10:00:48 +0800
From:   "Huang, Ying" <ying.huang@...el.com>
To:     Miaohe Lin <linmiaohe@...wei.com>
Cc:     <akpm@...ux-foundation.org>, <mike.kravetz@...cle.com>,
        <shy828301@...il.com>, <willy@...radead.org>, <ziy@...dia.com>,
        <minchan@...nel.org>, <apopple@...dia.com>,
        <ave.hansen@...ux.intel.com>, <o451686892@...il.com>,
        <almasrymina@...gle.com>, <jhubbard@...dia.com>,
        <rcampbell@...dia.com>, <peterx@...hat.com>,
        <naoya.horiguchi@....com>, <mhocko@...e.com>, <riel@...hat.com>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 01/16] mm/migration: remove unneeded local variable
 mapping_locked

Miaohe Lin <linmiaohe@...wei.com> writes:

> When mapping_locked is true, TTU_RMAP_LOCKED is always set to ttu. We can
> check ttu instead so mapping_locked can be removed. And ttu is either 0
> or TTU_RMAP_LOCKED now. Change '|=' to '=' to reflect this.
>
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
> ---
>  mm/migrate.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 42e3a944f35c..50bc62d85eaf 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1230,7 +1230,6 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
>  		goto put_anon;
>  
>  	if (page_mapped(hpage)) {
> -		bool mapping_locked = false;
>  		enum ttu_flags ttu = 0;
>  
>  		if (!PageAnon(hpage)) {
> @@ -1244,14 +1243,13 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
>  			if (unlikely(!mapping))
>  				goto unlock_put_anon;
>  
> -			mapping_locked = true;
> -			ttu |= TTU_RMAP_LOCKED;
> +			ttu = TTU_RMAP_LOCKED;
>  		}
>  
>  		try_to_migrate(src, ttu);
>  		page_was_mapped = 1;
>  
> -		if (mapping_locked)
> +		if (ttu & TTU_RMAP_LOCKED)
>  			i_mmap_unlock_write(mapping);
>  	}

I think this is a code style issue.  The original code looks more
readable for me.

Best Regards,
Huang, Ying