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Date:   Tue, 27 Jun 2023 12:30:46 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Miaohe Lin <linmiaohe@huawei.com>
Cc:     <naoya.horiguchi@nec.com>, <linux-mm@kvack.org>,
        <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm: memory-failure: fix unexpected return value in
 soft_offline_page()
Message-Id: <20230627123046.ef7e791208214bbfecd71e42@linux-foundation.org>
In-Reply-To: <20230627112808.1275241-1-linmiaohe@huawei.com>
References: <20230627112808.1275241-1-linmiaohe@huawei.com>
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On Tue, 27 Jun 2023 19:28:08 +0800 Miaohe Lin <linmiaohe@huawei.com> wrote:

> When page_handle_poison() fails to handle the hugepage or free page in
> retry path, soft_offline_page() will return 0 while -EBUSY is expected
> in this case.

What are the user visible effects of the bug?

> Fixes: b94e02822deb ("mm,hwpoison: try to narrow window race for free pages")
>
> ...
>
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -2737,10 +2737,13 @@ int soft_offline_page(unsigned long pfn, int flags)
>  	if (ret > 0) {
>  		ret = soft_offline_in_use_page(page);
>  	} else if (ret == 0) {
> -		if (!page_handle_poison(page, true, false) && try_again) {
> -			try_again = false;
> -			flags &= ~MF_COUNT_INCREASED;
> -			goto retry;
> +		if (!page_handle_poison(page, true, false)) {
> +			if (try_again) {
> +				try_again = false;
> +				flags &= ~MF_COUNT_INCREASED;
> +				goto retry;
> +			}
> +			ret = -EBUSY;
>  		}
>  	}