linux-kernel - Re: + mm-reclaim-madv_free-pages.patch added to -mm tree

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Date:   Tue, 7 Mar 2017 10:58:33 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Minchan Kim <minchan@...nel.org>
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, shli@...com,
        hillf.zj@...baba-inc.com, hughd@...gle.com,
        mgorman@...hsingularity.net, riel@...hat.com,
        mm-commits@...r.kernel.org
Subject: Re: + mm-reclaim-madv_free-pages.patch added to -mm tree

On Tue 07-03-17 14:55:51, Minchan Kim wrote:
[...]
> >From d42d296950c3bbce74afddcff307fa18eef305fe Mon Sep 17 00:00:00 2001
> From: Minchan Kim <minchan@...nel.org>
> Date: Tue, 7 Mar 2017 14:48:37 +0900
> Subject: [PATCH] mm: fix lazyfree bug on check in try_to_unmap_one
> 
> If a page is swapbacked, it means it should be in swapcache
> in try_to_unmap_one's path.
> 
> If a page is !swapbacked, it mean it shouldn't be in swapcache
> in try_to_unmap_one's path.
> 
> Check both two cases all at once and if it fails, warn and
> return SWAP_FAIL. Such bug never mean we should shut down
> the kernel.
> 
> Suggested-by: Johannes Weiner <hannes@...xchg.org>
> Signed-off-by: Minchan Kim <minchan@...nel.org>

looks good to me
Acked-by: Michal Hocko <mhocko@...e.com>

> ---
>  mm/rmap.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/rmap.c b/mm/rmap.c
> index 35acb83..9925f32 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -1413,8 +1413,13 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
>  			 * Store the swap location in the pte.
>  			 * See handle_pte_fault() ...
>  			 */
> -			VM_BUG_ON_PAGE(!PageSwapCache(page) && PageSwapBacked(page),
> -				page);
> +			if (VM_WARN_ON_ONCE(PageSwapBacked(page) !=
> +						PageSwapCache(page))) {
> +				ret = SWAP_FAIL;
> +				page_vma_mapped_walk_done(&pvmw);
> +				break;
> +
> +			}
>  
>  			/* MADV_FREE page check */
>  			if (!PageSwapBacked(page)) {
> -- 
> 2.7.4
> 

-- 
Michal Hocko
SUSE Labs