linux-kernel - Re: [PATCH 1/2] mm/hwpoison: fix fail to split THP w/ refcount held

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Date:	Mon, 10 Aug 2015 08:10:20 +0000
From:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
To:	Wanpeng Li <wanpeng.li@...mail.com>
CC:	Andrew Morton <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 1/2] mm/hwpoison: fix fail to split THP w/ refcount held

On Mon, Aug 10, 2015 at 02:32:30PM +0800, Wanpeng Li wrote:
> THP pages will get a refcount in madvise_hwpoison() w/ MF_COUNT_INCREASED 
> flag, however, the refcount is still held when fail to split THP pages.
> 
> Fix it by reducing the refcount of THP pages when fail to split THP.
> 
> Signed-off-by: Wanpeng Li <wanpeng.li@...mail.com>

It seems that the same conditional put_page() would be added to
"soft offline: %#lx page already poisoned" branch too, right?

> ---
>  mm/memory-failure.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 8077b1c..56b8a71 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1710,6 +1710,8 @@ int soft_offline_page(struct page *page, int flags)
>  		if (PageAnon(hpage) && unlikely(split_huge_page(hpage))) {
>  			pr_info("soft offline: %#lx: failed to split THP\n",
>  				pfn);
> +			if (flags & MF_COUNT_INCREASED)
> +				put_page(page);
>  			return -EBUSY;
>  		}
>  	}
> -- 
> 1.7.1
> 
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