From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf1-f70.google.com (mail-lf1-f70.google.com [209.85.167.70]) by kanga.kvack.org (Postfix) with ESMTP id A5D1A8E0001 for ; Fri, 21 Dec 2018 15:21:42 -0500 (EST) Received: by mail-lf1-f70.google.com with SMTP id m10so727896lfk.6 for ; Fri, 21 Dec 2018 12:21:42 -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 j81-v6sor16901847ljb.30.2018.12.21.12.21.40 for (Google Transport Security); Fri, 21 Dec 2018 12:21:40 -0800 (PST) Date: Fri, 21 Dec 2018 23:21:37 +0300 From: "Kirill A. Shutemov" Subject: Re: [PATCH v2 2/2] hugetlbfs: Use i_mmap_rwsem to fix page fault/truncate race Message-ID: <20181221202136.crrwojz3k7muvyrh@kshutemo-mobl1> References: <20181218223557.5202-1-mike.kravetz@oracle.com> <20181218223557.5202-3-mike.kravetz@oracle.com> <20181221102824.5v36l6l5t2zthpgr@kshutemo-mobl1> <849f5202-2200-265f-7769-8363053e8373@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <849f5202-2200-265f-7769-8363053e8373@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 , stable@vger.kernel.org On Fri, Dec 21, 2018 at 10:28:25AM -0800, Mike Kravetz wrote: > On 12/21/18 2:28 AM, Kirill A. Shutemov wrote: > > On Tue, Dec 18, 2018 at 02:35:57PM -0800, Mike Kravetz wrote: > >> Instead of writing the required complicated code for this rare > >> occurrence, just eliminate the race. i_mmap_rwsem is now held in read > >> mode for the duration of page fault processing. Hold i_mmap_rwsem > >> longer in truncation and hold punch code to cover the call to > >> remove_inode_hugepages. > > > > One of remove_inode_hugepages() callers is noticeably missing -- > > hugetlbfs_evict_inode(). Why? > > > > It at least deserves a comment on why the lock rule doesn't apply to it. > > In the case of hugetlbfs_evict_inode, the vfs layer guarantees there are > no more users of the inode/file. I'm not convinced that it is true. See documentation for ->evict_inode() in Documentation/filesystems/porting: Caller does *not* evict the pagecache or inode-associated metadata buffers; the method has to use truncate_inode_pages_final() to get rid of those. Is hugetlbfs special here? -- Kirill A. Shutemov