Date: Thu, 16 Jul 2015 04:33:07 +0200
From: Andi Kleen <andi@firstfloor.org>
To: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Andi Kleen <andi@firstfloor.org>, Dean Nelson <dnelson@redhat.com>,
        Tony Luck <tony.luck@intel.com>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
        Hugh Dickins <hughd@google.com>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Naoya Horiguchi <nao.horiguchi@gmail.com>
Subject: Re: [PATCH v1 3/4] mm/memory-failure: give up error handling for
 non-tail-refcounted thp
Message-ID: <20150716023307.GF1747@two.firstfloor.org>
References: <1437010894-10262-1-git-send-email-n-horiguchi@ah.jp.nec.com>
 <1437010894-10262-4-git-send-email-n-horiguchi@ah.jp.nec.com>
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> @@ -909,6 +909,15 @@ int get_hwpoison_page(struct page *page)
>  	 * directly for tail pages.
>  	 */
>  	if (PageTransHuge(head)) {
> +		/*
> +		 * Non anonymous thp exists only in allocation/free time. We
> +		 * can't handle such a case correctly, so let's give it up.
> +		 * This should be better than triggering BUG_ON when kernel
> +		 * tries to touch a "partially handled" page.
> +		 */
> +		if (!PageAnon(head))
> +			return 0;

Please print a message for this case. In the future there will be
likely more non anonymous THP pages from Kirill's large page cache work
(so eventually we'll need it)

-Andi

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