linux-kernel - Re: [PATCH v3 1/2] mm: soft-offline: return -EBUSY if set_hwpoison_free_buddy

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Message-ID: <20190618145748.GA14817@linux>
Date:   Tue, 18 Jun 2019 16:57:52 +0200
From:   Oscar Salvador <osalvador@...e.de>
To:     Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...nel.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        xishi.qiuxishi@...baba-inc.com,
        "Chen, Jerry T" <jerry.t.chen@...el.com>,
        "Zhuo, Qiuxu" <qiuxu.zhuo@...el.com>, linux-kernel@...r.kernel.org,
        Anshuman Khandual <anshuman.khandual@....com>
Subject: Re: [PATCH v3 1/2] mm: soft-offline: return -EBUSY if
 set_hwpoison_free_buddy_page() fails

On Mon, Jun 17, 2019 at 05:51:15PM +0900, Naoya Horiguchi wrote:
> The pass/fail of soft offline should be judged by checking whether the
> raw error page was finally contained or not (i.e. the result of
> set_hwpoison_free_buddy_page()), but current code do not work like that.
> So this patch is suggesting to fix it.
> 
> Without this fix, there are cases where madvise(MADV_SOFT_OFFLINE) may
> not offline the original page and will not return an error.  It might
> lead us to misjudge the test result when set_hwpoison_free_buddy_page()
> actually fails.
> 
> Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
> Fixes: 6bc9b56433b76 ("mm: fix race on soft-offlining")
> Cc: <stable@...r.kernel.org> # v4.19+

Reviewed-by: Oscar Salvador <osalvador@...e.de>

> ---
> ChangeLog v2->v3:
> - update patch description to clarify user visible change
> ---
>  mm/memory-failure.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git v5.2-rc4/mm/memory-failure.c v5.2-rc4_patched/mm/memory-failure.c
> index 8da0334..8ee7b16 100644
> --- v5.2-rc4/mm/memory-failure.c
> +++ v5.2-rc4_patched/mm/memory-failure.c
> @@ -1730,6 +1730,8 @@ static int soft_offline_huge_page(struct page *page, int flags)
>  		if (!ret) {
>  			if (set_hwpoison_free_buddy_page(page))
>  				num_poisoned_pages_inc();
> +			else
> +				ret = -EBUSY;
>  		}
>  	}
>  	return ret;
> -- 
> 2.7.0
> 

-- 
Oscar Salvador
SUSE L3