Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754922Ab3DVOaN (ORCPT ); Mon, 22 Apr 2013 10:30:13 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:51555 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754862Ab3DVOaE (ORCPT ); Mon, 22 Apr 2013 10:30:04 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Linus Torvalds" , "HATAYAMA Daisuke" , "Naoya Horiguchi" , "Rik van Riel" , "David Rientjes" , "KOSAKI Motohiro" , "Michal Hocko" Date: Mon, 22 Apr 2013 15:25:59 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [50/75] hugetlbfs: add swap entry check in follow_hugetlb_page() In-Reply-To: X-SA-Exim-Connect-IP: 2001:470:1f08:1539:6834:ff73:7553:7f84 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3216 Lines: 79 3.2.44-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Naoya Horiguchi commit 9cc3a5bd40067b9a0fbd49199d0780463fc2140f upstream. 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. The expected behavior is like this: absent is_swap_pte FOLL_DUMP Expected behavior ------------------------------------------------------------------- true false false hugetlb_fault false true false hugetlb_fault false false false return page true false true skip page (to avoid allocation) false true true hugetlb_fault false false true return page With this patch, we can call hugetlb_fault() and take proper actions (we wait for migration entries, fail with VM_FAULT_HWPOISON_LARGE for hwpoisoned entries,) and as the result we can dump all hugepages except for hwpoisoned ones. Signed-off-by: Naoya Horiguchi Cc: Rik van Riel Acked-by: Michal Hocko Cc: HATAYAMA Daisuke Acked-by: KOSAKI Motohiro Acked-by: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Ben Hutchings --- mm/hugetlb.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -2889,7 +2889,17 @@ int follow_hugetlb_page(struct mm_struct break; } - if (absent || + /* + * We need call hugetlb_fault for both hugepages under migration + * (in which case hugetlb_fault waits for the migration,) and + * hwpoisoned hugepages (in which case we need to prevent the + * caller from accessing to them.) In order to do this, we use + * here is_swap_pte instead of is_hugetlb_entry_migration and + * is_hugetlb_entry_hwpoisoned. This is because it simply covers + * both cases, and because we can't follow correct pages + * directly from any kind of swap entries. + */ + if (absent || is_swap_pte(huge_ptep_get(pte)) || ((flags & FOLL_WRITE) && !pte_write(huge_ptep_get(pte)))) { int ret; -- 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/