From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk1-f198.google.com (mail-qk1-f198.google.com [209.85.222.198]) by kanga.kvack.org (Postfix) with ESMTP id 4B04E6B6AD9 for ; Mon, 3 Dec 2018 15:09:09 -0500 (EST) Received: by mail-qk1-f198.google.com with SMTP id v74so14171331qkb.21 for ; Mon, 03 Dec 2018 12:09:09 -0800 (PST) Received: from aserp2120.oracle.com (aserp2120.oracle.com. [141.146.126.78]) by mx.google.com with ESMTPS id x189si183100qke.171.2018.12.03.12.09.07 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 03 Dec 2018 12:09:08 -0800 (PST) From: Mike Kravetz Subject: [PATCH 0/3] hugetlbfs: use i_mmap_rwsem for better synchronization Date: Mon, 3 Dec 2018 12:08:47 -0800 Message-Id: <20181203200850.6460-1-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 These 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. There are two primary issues addressed here: 1) For shared pmds, huge PE 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. I broke up the larger RFC into separate patches addressing each issue. Hopefully, this is easier to understand/review. Mike Kravetz (3): hugetlbfs: use i_mmap_rwsem for more pmd sharing synchronization hugetlbfs: Use i_mmap_rwsem to fix page fault/truncate race hugetlbfs: remove unnecessary code after i_mmap_rwsem synchronization 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