From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx104.postini.com [74.125.245.104]) by kanga.kvack.org (Postfix) with SMTP id 944F46B0005 for ; Wed, 3 Apr 2013 16:03:22 -0400 (EDT) Message-ID: <515C8AB1.7060003@redhat.com> Date: Wed, 03 Apr 2013 16:01:53 -0400 From: Rik van Riel MIME-Version: 1.0 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: owner-linux-mm@kvack.org List-ID: 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 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 -- 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