From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lj1-f197.google.com (mail-lj1-f197.google.com [209.85.208.197]) by kanga.kvack.org (Postfix) with ESMTP id CAB038E0001 for ; Mon, 24 Dec 2018 05:13:54 -0500 (EST) Received: by mail-lj1-f197.google.com with SMTP id 2-v6so3762039ljs.15 for ; Mon, 24 Dec 2018 02:13:54 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id m72sor8610525lfe.8.2018.12.24.02.13.52 for (Google Transport Security); Mon, 24 Dec 2018 02:13:52 -0800 (PST) Date: Mon, 24 Dec 2018 13:13:49 +0300 From: "Kirill A. Shutemov" Subject: Re: [PATCH v3 0/2] hugetlbfs: use i_mmap_rwsem for better synchronization Message-ID: <20181224101349.jjjmk2hzwah6g64h@kshutemo-mobl1> References: <20181222223013.22193-1-mike.kravetz@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181222223013.22193-1-mike.kravetz@oracle.com> Sender: owner-linux-mm@kvack.org List-ID: To: Mike Kravetz Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Michal Hocko , Hugh Dickins , Naoya Horiguchi , "Aneesh Kumar K . V" , Andrea Arcangeli , "Kirill A . Shutemov" , Davidlohr Bueso , Prakash Sangappa , Andrew Morton On Sat, Dec 22, 2018 at 02:30:11PM -0800, Mike Kravetz wrote: > 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. > > v2 -> v3 > Incorporated suggestions from Kirill. Code change to hold i_mmap_rwsem > for duration of copy in copy_hugetlb_page_range. Took i_mmap_rwsem in > hugetlbfs_evict_inode to be consistent with other callers. Other changes > were to documentation/comments. > 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 Looks good to me. Acked-by: Kirill A. Shutemov -- Kirill A. Shutemov