linux-kernel - Re: [PATCH] mm/zsmalloc.c: fix the migrated zspage statistics.

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Message-ID: <43d28728-2cc2-7978-633a-fbae48433b87@suse.cz>
Date:   Fri, 29 Nov 2019 16:17:33 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Chanho Min <chanho.min@....com>, Minchan Kim <minchan@...nel.org>,
        Nitin Gupta <ngupta@...are.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        seungho1.park@....com, Inkyu Hwang <inkyu.hwang@....com>,
        Jinsuk Choi <jjinsuk.choi@....com>
Subject: Re: [PATCH] mm/zsmalloc.c: fix the migrated zspage statistics.

On 11/29/19 2:29 AM, Chanho Min wrote:
> When zspage is migrated to the other zone, the zone page state should
> be updated as well.

What are the user visible effects? I assume NR_ZSPAGES accounting can go
wrong otherwise? Has it been observed in practice?
Should we Cc stable and identify a Fixes: commit?

Thanks,
Vlastimil

> Signed-off-by: Chanho Min <chanho.min@....com>
> Signed-off-by: Jinsuk Choi <jjinsuk.choi@....com>
> ---
>  mm/zsmalloc.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index 2b2b9aa..22d17ec 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -2069,6 +2069,11 @@ static int zs_page_migrate(struct address_space *mapping, struct page *newpage,
>  		zs_pool_dec_isolated(pool);
>  	}
>  
> +	if (page_zone(newpage) != page_zone(page)) {
> +		dec_zone_page_state(page, NR_ZSPAGES);
> +		inc_zone_page_state(newpage, NR_ZSPAGES);
> +	}
> +
>  	reset_page(page);
>  	put_page(page);
>  	page = newpage;
>