Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932284AbbHJIzO (ORCPT ); Mon, 10 Aug 2015 04:55:14 -0400 Received: from blu004-omc1s38.hotmail.com ([65.55.116.49]:62836 "EHLO BLU004-OMC1S38.hotmail.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932105AbbHJIzM (ORCPT ); Mon, 10 Aug 2015 04:55:12 -0400 X-TMN: [WksdrY5pZe2ayVs5e+fibOLGdDFfKko6] X-Originating-Email: [wanpeng.li@hotmail.com] Message-ID: Subject: Re: [PATCH 2/2] mm/hwpoison: fix refcount of THP head page in no-injection case To: Naoya Horiguchi References: <1439188351-24292-1-git-send-email-wanpeng.li@hotmail.com> <20150810083529.GB21282@hori1.linux.bs1.fc.nec.co.jp> CC: Andrew Morton , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" From: Wanpeng Li Date: Mon, 10 Aug 2015 16:54:39 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:38.0) Gecko/20100101 Thunderbird/38.0.1 MIME-Version: 1.0 In-Reply-To: <20150810083529.GB21282@hori1.linux.bs1.fc.nec.co.jp> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 10 Aug 2015 08:55:10.0351 (UTC) FILETIME=[4346F9F0:01D0D34A] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2046 Lines: 56 On 8/10/15 4:35 PM, Naoya Horiguchi wrote: > 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. Good point. I think I will continue to do it and will post it out soon. :) Regards, Wanpeng Li > 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/