From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f173.google.com (mail-pd0-f173.google.com [209.85.192.173]) by kanga.kvack.org (Postfix) with ESMTP id 739A06B0253 for ; Mon, 10 Aug 2015 04:43:14 -0400 (EDT) Received: by pdrh1 with SMTP id h1so51119071pdr.0 for ; Mon, 10 Aug 2015 01:43:14 -0700 (PDT) Received: from tyo202.gate.nec.co.jp (TYO202.gate.nec.co.jp. [210.143.35.52]) by mx.google.com with ESMTPS id nj7si32046923pdb.158.2015.08.10.01.43.13 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Mon, 10 Aug 2015 01:43:13 -0700 (PDT) From: Naoya Horiguchi Subject: Re: [PATCH 2/2] mm/hwpoison: fix refcount of THP head page in no-injection case Date: Mon, 10 Aug 2015 08:35:30 +0000 Message-ID: <20150810083529.GB21282@hori1.linux.bs1.fc.nec.co.jp> References: <1439188351-24292-1-git-send-email-wanpeng.li@hotmail.com> In-Reply-To: Content-Language: ja-JP Content-Type: text/plain; charset="iso-2022-jp" Content-ID: <24B41AF21A75A04BA2E3468CB07A92FF@gisp.nec.co.jp> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: Wanpeng Li Cc: Andrew Morton , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" On Mon, Aug 10, 2015 at 02:32:31PM +0800, Wanpeng Li wrote: > Hwpoison injection takes a refcount of target page and another refcount > of head page of THP if the target page is the tail page of a THP. However= , > current code doesn't release the refcount of head page if the THP is not= =20 > supported to be injected wrt hwpoison filter.=20 >=20 > Fix it by reducing the refcount of head page if the target page is the ta= il=20 > page of a THP and it is not supported to be injected. >=20 > Signed-off-by: Wanpeng Li > --- > mm/hwpoison-inject.c | 2 ++ > 1 files changed, 2 insertions(+), 0 deletions(-) >=20 > diff --git a/mm/hwpoison-inject.c b/mm/hwpoison-inject.c > index 5015679..c343a45 100644 > --- a/mm/hwpoison-inject.c > +++ b/mm/hwpoison-inject.c > @@ -56,6 +56,8 @@ inject: > return memory_failure(pfn, 18, MF_COUNT_INCREASED); > put_out: > put_page(p); > + if (p !=3D hpage) > + put_page(hpage); Yes, we need this when we inject to a thp tail page and "goto put_out" is called. But it seems that this code can be called also when injecting error to a hugetlb tail page and hwpoison_filter() returns non-zero, which is not expected. Unfortunately simply doing like below + if (!PageHuge(p) && p !=3D hpage) + put_page(hpage); doesn't work, because exisiting put_page(p) can release refcount of hugetlb tail page, while get_hwpoison_page() takes refcount of hugetlb head page. So I feel that we need put_hwpoison_page() to properly release the refcount taken by memory error handlers. I'll post some patch(es) to address this problem this week. Thanks, Naoya Horiguchi= -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org