From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763229Ab3DCUEu (ORCPT ); Wed, 3 Apr 2013 16:04:50 -0400 Received: from mx1.redhat.com ([209.132.183.28]:40634 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759768Ab3DCUEt (ORCPT ); Wed, 3 Apr 2013 16:04:49 -0400 Message-ID: <515C8AB1.7060003@redhat.com> Date: Wed, 03 Apr 2013 16:01:53 -0400 From: Rik van Riel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/17.0 Thunderbird/17.0 MIME-Version: 1.0 To: Naoya Horiguchi CC: Andrew Morton , Mel Gorman , Hugh Dickins , KOSAKI Motohiro , Konstantin Khlebnikov , Michal Hocko , HATAYAMA Daisuke , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 3/3] hugetlbfs: add swap entry check in follow_hugetlb_page() References: <1365014138-19589-1-git-send-email-n-horiguchi@ah.jp.nec.com> <1365014138-19589-4-git-send-email-n-horiguchi@ah.jp.nec.com> In-Reply-To: <1365014138-19589-4-git-send-email-n-horiguchi@ah.jp.nec.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/03/2013 02:35 PM, Naoya Horiguchi wrote: > With applying the previous patch "hugetlbfs: stop setting VM_DONTDUMP in > initializing vma(VM_HUGETLB)" to reenable hugepage coredump, if a memory > error happens on a hugepage and the affected processes try to access > the error hugepage, we hit VM_BUG_ON(atomic_read(&page->_count) <= 0) > in get_page(). > > The reason for this bug is that coredump-related code doesn't recognise > "hugepage hwpoison entry" with which a pmd entry is replaced when a memory > error occurs on a hugepage. > In other words, physical address information is stored in different bit layout > between hugepage hwpoison entry and pmd entry, so follow_hugetlb_page() > which is called in get_dump_page() returns a wrong page from a given address. > > We need to filter out only hwpoison hugepages to have data on healthy > hugepages in coredump. So this patch makes follow_hugetlb_page() avoid > trying to get page when a pmd is in swap entry like format. > > ChangeLog v3: > - add comment about using is_swap_pte() > > Signed-off-by: Naoya Horiguchi > Reviewed-by: Michal Hocko > Acked-by: Konstantin Khlebnikov > Cc: stable@vger.kernel.org Reviewed-by: Rik van Riel