linux-kernel - Re: [PATCH v3] mm: use swp_offset as key in shmem_replace

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Date:   Wed, 21 Nov 2018 16:36:37 -0800 (PST)
From:   Hugh Dickins <hughd@...gle.com>
To:     Yu Zhao <yuzhao@...gle.com>
cc:     Hugh Dickins <hughd@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>, stable@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] mm: use swp_offset as key in shmem_replace_page()

On Wed, 21 Nov 2018, Yu Zhao wrote:

> We changed key of swap cache tree from swp_entry_t.val to
> swp_offset. Need to do so in shmem_replace_page() as well.
> 
> Fixes: f6ab1f7f6b2d ("mm, swap: use offset of swap entry as key of swap cache")
> Cc: stable@...r.kernel.org # v4.9+
> Signed-off-by: Yu Zhao <yuzhao@...gle.com>

Acked-by: Hugh Dickins <hughd@...gle.com>

Thanks!

> ---
>  mm/shmem.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/shmem.c b/mm/shmem.c
> index d44991ea5ed4..42b70978e814 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -1509,11 +1509,13 @@ static int shmem_replace_page(struct page **pagep, gfp_t gfp,
>  {
>  	struct page *oldpage, *newpage;
>  	struct address_space *swap_mapping;
> +	swp_entry_t entry;
>  	pgoff_t swap_index;
>  	int error;
>  
>  	oldpage = *pagep;
> -	swap_index = page_private(oldpage);
> +	entry.val = page_private(oldpage);
> +	swap_index = swp_offset(entry);
>  	swap_mapping = page_mapping(oldpage);
>  
>  	/*
> @@ -1532,7 +1534,7 @@ static int shmem_replace_page(struct page **pagep, gfp_t gfp,
>  	__SetPageLocked(newpage);
>  	__SetPageSwapBacked(newpage);
>  	SetPageUptodate(newpage);
> -	set_page_private(newpage, swap_index);
> +	set_page_private(newpage, entry.val);
>  	SetPageSwapCache(newpage);
>  
>  	/*
> -- 
> 2.19.1.1215.g8438c0b245-goog