From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f52.google.com (mail-oi0-f52.google.com [209.85.218.52]) by kanga.kvack.org (Postfix) with ESMTP id 93C476B0254 for ; Mon, 10 Aug 2015 04:55:12 -0400 (EDT) Received: by oio137 with SMTP id 137so81707573oio.0 for ; Mon, 10 Aug 2015 01:55:12 -0700 (PDT) Received: from BLU004-OMC1S38.hotmail.com (blu004-omc1s38.hotmail.com. [65.55.116.49]) by mx.google.com with ESMTPS id b188si992827oih.121.2015.08.10.01.55.11 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Mon, 10 Aug 2015 01:55:11 -0700 (PDT) Message-ID: Subject: Re: [PATCH 2/2] mm/hwpoison: fix refcount of THP head page in no-injection case References: <1439188351-24292-1-git-send-email-wanpeng.li@hotmail.com> <20150810083529.GB21282@hori1.linux.bs1.fc.nec.co.jp> From: Wanpeng Li Date: Mon, 10 Aug 2015 16:54:39 +0800 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 Sender: owner-linux-mm@kvack.org List-ID: To: Naoya Horiguchi Cc: Andrew Morton , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" 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, 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