Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754093AbbHJInR (ORCPT ); Mon, 10 Aug 2015 04:43:17 -0400 Received: from TYO202.gate.nec.co.jp ([210.143.35.52]:57506 "EHLO tyo202.gate.nec.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753392AbbHJInP convert rfc822-to-8bit (ORCPT ); Mon, 10 Aug 2015 04:43:15 -0400 From: Naoya Horiguchi To: Wanpeng Li CC: Andrew Morton , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 2/2] mm/hwpoison: fix refcount of THP head page in no-injection case Thread-Topic: [PATCH 2/2] mm/hwpoison: fix refcount of THP head page in no-injection case Thread-Index: AQHQ0zjJFF+Ln+B3nEavQuvZcEKyVp4EUbSA 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: Accept-Language: ja-JP, en-US Content-Language: ja-JP X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.128.101.31] Content-Type: text/plain; charset="iso-2022-jp" Content-ID: <24B41AF21A75A04BA2E3468CB07A92FF@gisp.nec.co.jp> Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1848 Lines: 46 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 > supported to be injected wrt hwpoison filter. > > Fix it by reducing the refcount of head page if the target page is the tail > page of a THP and it is not supported to be injected. > > Signed-off-by: Wanpeng Li > --- > mm/hwpoison-inject.c | 2 ++ > 1 files changed, 2 insertions(+), 0 deletions(-) > > 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 != 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 != 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 from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/