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Subject: Re: [PATCH 01/18] mm: fix NUMA node file count error in
 replace_page_cache()
To:     Johannes Weiner <hannes@cmpxchg.org>,
        Joonsoo Kim <js1304@gmail.com>
Cc:     Shakeel Butt <shakeelb@google.com>,
        Hugh Dickins <hughd@google.com>,
        Michal Hocko <mhocko@suse.com>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
        Roman Gushchin <guro@fb.com>, linux-mm@kvack.org,
        cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
        kernel-team@fb.com
References: <20200420221126.341272-1-hannes@cmpxchg.org>
 <20200420221126.341272-2-hannes@cmpxchg.org>
From:   Alex Shi <alex.shi@linux.alibaba.com>
Message-ID: <c5c379d5-d580-58ec-c9d1-f05d6cdc57b4@linux.alibaba.com>
Date:   Tue, 21 Apr 2020 16:28:10 +0800
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?? 2020/4/21 ????6:11, Johannes Weiner д??:
> When replacing one page with another one in the cache, we have to
> decrease the file count of the old page's NUMA node and increase the
> one of the new NUMA node, otherwise the old node leaks the count and
> the new node eventually underflows its counter.
> 
> Fixes: 74d609585d8b ("page cache: Add and replace pages using the XArray")
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>

Reviewed-by: Alex Shi <alex.shi@linux.alibaba.com>

> ---
>  mm/filemap.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 23a051a7ef0f..49e3b5da0216 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -808,11 +808,11 @@ int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
>  	old->mapping = NULL;
>  	/* hugetlb pages do not participate in page cache accounting. */
>  	if (!PageHuge(old))
> -		__dec_node_page_state(new, NR_FILE_PAGES);
> +		__dec_node_page_state(old, NR_FILE_PAGES);
>  	if (!PageHuge(new))
>  		__inc_node_page_state(new, NR_FILE_PAGES);
>  	if (PageSwapBacked(old))
> -		__dec_node_page_state(new, NR_SHMEM);
> +		__dec_node_page_state(old, NR_SHMEM);
>  	if (PageSwapBacked(new))
>  		__inc_node_page_state(new, NR_SHMEM);
>  	xas_unlock_irqrestore(&xas, flags);
>