linux-kernel - Re: [PATCH v1 3/4] mm/memory-failure: give up error handling for non-tail-refcounted thp

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Message-ID: <20150716023307.GF1747@two.firstfloor.org>
Date:	Thu, 16 Jul 2015 04:33:07 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>,
	Dean Nelson <dnelson@...hat.com>,
	Tony Luck <tony.luck@...el.com>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	Hugh Dickins <hughd@...gle.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Naoya Horiguchi <nao.horiguchi@...il.com>
Subject: Re: [PATCH v1 3/4] mm/memory-failure: give up error handling for
 non-tail-refcounted thp

> @@ -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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