linux-kernel - Re: [RFC 04/11] mm: remove SWAP_MLOCK check for SWAP

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Message-Id: <65fd1dd1-7ca4-6610-285c-09436879d8ed@linux.vnet.ibm.com>
Date:   Thu, 2 Mar 2017 20:21:46 +0530
From:   Anshuman Khandual <khandual@...ux.vnet.ibm.com>
To:     Minchan Kim <minchan@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     kernel-team@....com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...e.com>
Subject: Re: [RFC 04/11] mm: remove SWAP_MLOCK check for SWAP_SUCCESS in ttu

On 03/02/2017 12:09 PM, Minchan Kim wrote:
> If the page is mapped and rescue in ttuo, page_mapcount(page) == 0 cannot

Nit: "ttuo" is very cryptic. Please expand it.

> be true so page_mapcount check in ttu is enough to return SWAP_SUCCESS.
> IOW, SWAP_MLOCK check is redundant so remove it.

Right, page_mapcount(page) should be enough to tell whether swapping
out happened successfully or the page is still mapped in some page
table.

> 
> Signed-off-by: Minchan Kim <minchan@...nel.org>
> ---
>  mm/rmap.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/rmap.c b/mm/rmap.c
> index 3a14013..0a48958 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -1523,7 +1523,7 @@ int try_to_unmap(struct page *page, enum ttu_flags flags)
>  	else
>  		ret = rmap_walk(page, &rwc);
>  
> -	if (ret != SWAP_MLOCK && !page_mapcount(page))
> +	if (!page_mapcount(page))
>  		ret = SWAP_SUCCESS;
>  	return ret;
>  }
>