From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io1-f71.google.com (mail-io1-f71.google.com [209.85.166.71]) by kanga.kvack.org (Postfix) with ESMTP id F04218E0001 for ; Tue, 18 Dec 2018 17:36:13 -0500 (EST) Received: by mail-io1-f71.google.com with SMTP id f24so16769970ioh.21 for ; Tue, 18 Dec 2018 14:36:13 -0800 (PST) Received: from userp2120.oracle.com (userp2120.oracle.com. [156.151.31.85]) by mx.google.com with ESMTPS id m14si1878363itl.54.2018.12.18.14.36.12 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 18 Dec 2018 14:36:12 -0800 (PST) From: Mike Kravetz Subject: [PATCH v2 0/2] hugetlbfs: use i_mmap_rwsem for better synchronization Date: Tue, 18 Dec 2018 14:35:55 -0800 Message-Id: <20181218223557.5202-1-mike.kravetz@oracle.com> Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Michal Hocko , Hugh Dickins , Naoya Horiguchi , "Aneesh Kumar K . V" , Andrea Arcangeli , "Kirill A . Shutemov" , Davidlohr Bueso , Prakash Sangappa , Andrew Morton , Mike Kravetz There are two primary issues addressed here: 1) For shared pmds, huge PTE pointers returned by huge_pte_alloc can become invalid via a call to huge_pmd_unshare by another thread. 2) hugetlbfs page faults can race with truncation causing invalid global reserve counts and state. Both issues are addressed by expanding the use of i_mmap_rwsem. These issues have existed for a long time. They can be recreated with a test program that causes page fault/truncation races. For simple mappings, this results in a negative HugePages_Rsvd count. If racing with mappings that contain shared pmds, we can hit "BUG at fs/hugetlbfs/inode.c:444!" or Oops! as the result of an invalid memory reference. v1 -> v2 Combined patches 2 and 3 of v1 series as suggested by Aneesh. No other changes were made. Patches are a follow up to the RFC, http://lkml.kernel.org/r/20181024045053.1467-1-mike.kravetz@oracle.com Comments made by Naoya were addressed. Mike Kravetz (2): hugetlbfs: use i_mmap_rwsem for more pmd sharing synchronization hugetlbfs: Use i_mmap_rwsem to fix page fault/truncate race fs/hugetlbfs/inode.c | 50 +++++++++---------------- mm/hugetlb.c | 87 +++++++++++++++++++++++++++++++------------- mm/memory-failure.c | 14 ++++++- mm/migrate.c | 13 ++++++- mm/rmap.c | 3 ++ mm/userfaultfd.c | 11 +++++- 6 files changed, 116 insertions(+), 62 deletions(-) -- 2.17.2