From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756580Ab3C1Pn6 (ORCPT ); Thu, 28 Mar 2013 11:43:58 -0400 Received: from mx1.redhat.com ([209.132.183.28]:11211 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751385Ab3C1Pnz (ORCPT ); Thu, 28 Mar 2013 11:43:55 -0400 From: Naoya Horiguchi To: Andrew Morton Cc: Mel Gorman , Hugh Dickins , Rik van Riel , KOSAKI Motohiro , stable@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH 2/2] hugetlbfs: add swap entry check in follow_hugetlb_page() Date: Thu, 28 Mar 2013 11:42:38 -0400 Message-Id: <1364485358-8745-3-git-send-email-n-horiguchi@ah.jp.nec.com> In-Reply-To: <1364485358-8745-1-git-send-email-n-horiguchi@ah.jp.nec.com> References: <1364485358-8745-1-git-send-email-n-horiguchi@ah.jp.nec.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Signed-off-by: Naoya Horiguchi --- mm/hugetlb.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git v3.9-rc3.orig/mm/hugetlb.c v3.9-rc3/mm/hugetlb.c index 0d1705b..8462e2c 100644 --- v3.9-rc3.orig/mm/hugetlb.c +++ v3.9-rc3/mm/hugetlb.c @@ -2968,7 +2968,8 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, * first, for the page indexing below to work. */ pte = huge_pte_offset(mm, vaddr & huge_page_mask(h)); - absent = !pte || huge_pte_none(huge_ptep_get(pte)); + absent = !pte || huge_pte_none(huge_ptep_get(pte)) || + is_swap_pte(huge_ptep_get(pte)); /* * When coredumping, it suits get_dump_page if we just return -- 1.7.11.7 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx187.postini.com [74.125.245.187]) by kanga.kvack.org (Postfix) with SMTP id B28156B0036 for ; Thu, 28 Mar 2013 11:43:11 -0400 (EDT) From: Naoya Horiguchi Subject: [PATCH 2/2] hugetlbfs: add swap entry check in follow_hugetlb_page() Date: Thu, 28 Mar 2013 11:42:38 -0400 Message-Id: <1364485358-8745-3-git-send-email-n-horiguchi@ah.jp.nec.com> In-Reply-To: <1364485358-8745-1-git-send-email-n-horiguchi@ah.jp.nec.com> References: <1364485358-8745-1-git-send-email-n-horiguchi@ah.jp.nec.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Mel Gorman , Hugh Dickins , Rik van Riel , KOSAKI Motohiro , stable@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org 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. Signed-off-by: Naoya Horiguchi --- mm/hugetlb.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git v3.9-rc3.orig/mm/hugetlb.c v3.9-rc3/mm/hugetlb.c index 0d1705b..8462e2c 100644 --- v3.9-rc3.orig/mm/hugetlb.c +++ v3.9-rc3/mm/hugetlb.c @@ -2968,7 +2968,8 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, * first, for the page indexing below to work. */ pte = huge_pte_offset(mm, vaddr & huge_page_mask(h)); - absent = !pte || huge_pte_none(huge_ptep_get(pte)); + absent = !pte || huge_pte_none(huge_ptep_get(pte)) || + is_swap_pte(huge_ptep_get(pte)); /* * When coredumping, it suits get_dump_page if we just return -- 1.7.11.7 -- 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