linux-kernel - Re: [PATCH v8 2/3] mm/hwpoison: put page in already hwpoisoned case with MF_COUNT

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Message-ID: <84062e94-8356-a2b2-1074-e0143297223e@huawei.com>
Date:   Sat, 9 Apr 2022 10:04:41 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     Naoya Horiguchi <naoya.horiguchi@...ux.dev>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Yang Shi <shy828301@...il.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Naoya Horiguchi <naoya.horiguchi@....com>,
        <linux-kernel@...r.kernel.org>, Linux-MM <linux-mm@...ck.org>
Subject: Re: [PATCH v8 2/3] mm/hwpoison: put page in already hwpoisoned case
 with MF_COUNT_INCREASED

On 2022/4/8 21:53, Naoya Horiguchi wrote:
> From: Naoya Horiguchi <naoya.horiguchi@....com>
> 
> In already hwpoisoned case, memory_failure() is supposed to return with
> releasing the page refcount taken for error handling. But currently the
> refcount is not released when called with MF_COUNT_INCREASED, which
> makes page refcount inconsistent.  This should be rare and non-critical,
> but it might be inconvenient in testing (unpoison doesn't work).

IMHO, this issue will lead to memoryleak as page isn't freed even owner process
is killed. So we might need a Fixes tag?

Anyway, this patch looks good to me. Thanks!
Reviewed-by: Miaohe Lin <linmiaohe@...wei.com>

> 
> Suggested-by: Miaohe Lin <linmiaohe@...wei.com>
> Signed-off-by: Naoya Horiguchi <naoya.horiguchi@....com>
> ---
>  mm/memory-failure.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 2020944398c9..b2e32cdc3823 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1811,6 +1811,8 @@ int memory_failure(unsigned long pfn, int flags)
>  		res = -EHWPOISON;
>  		if (flags & MF_ACTION_REQUIRED)
>  			res = kill_accessing_process(current, pfn, flags);
> +		if (flags & MF_COUNT_INCREASED)
> +			put_page(p);
>  		goto unlock_mutex;
>  	}
>  
>