linux-kernel - Re: [PATCH 6/6] mm, hwpoison: avoid trying to unpoison reserved page

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Message-ID: <20220819052455.GF613144@hori.linux.bs1.fc.nec.co.jp>
Date:   Fri, 19 Aug 2022 05:24:55 +0000
From:   HORIGUCHI NAOYA(堀口　直也) 
        <naoya.horiguchi@....com>
To:     Miaohe Lin <linmiaohe@...wei.com>
CC:     "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 6/6] mm, hwpoison: avoid trying to unpoison reserved page

On Thu, Aug 18, 2022 at 09:00:16PM +0800, Miaohe Lin wrote:
> For reserved pages, HWPoison flag will be set without increasing the page
> refcnt. So we shouldn't even try to unpoison these pages and thus decrease
> the page refcnt unexpectly. Add a PageReserved() check to filter this case
> out and remove the below unneeded zero page (zero page is reserved) check.
> 
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>

Looks good to me, thank you.

Acked-by: Naoya Horiguchi <naoya.horiguchi@....com>

> ---
>  mm/memory-failure.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 5f9615a86296..c831c41bb092 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -2355,7 +2355,7 @@ int unpoison_memory(unsigned long pfn)
>  		goto unlock_mutex;
>  	}
>  
> -	if (PageSlab(page) || PageTable(page))
> +	if (PageSlab(page) || PageTable(page) || PageReserved(page))
>  		goto unlock_mutex;
>  
>  	ret = get_hwpoison_page(p, MF_UNPOISON);
> @@ -2386,7 +2386,7 @@ int unpoison_memory(unsigned long pfn)
>  		freeit = !!TestClearPageHWPoison(p);
>  
>  		put_page(page);
> -		if (freeit && !(pfn == my_zero_pfn(0) && page_count(p) == 1)) {
> +		if (freeit) {
>  			put_page(page);
>  			ret = 0;
>  		}
> -- 
> 2.23.0