From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AB2D5C3F2CD for ; Sat, 29 Feb 2020 18:40:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 87EFA214DB for ; Sat, 29 Feb 2020 18:40:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727461AbgB2Sko (ORCPT ); Sat, 29 Feb 2020 13:40:44 -0500 Received: from outgoing-auth-1.mit.edu ([18.9.28.11]:53000 "EHLO outgoing.mit.edu" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727194AbgB2Skn (ORCPT ); Sat, 29 Feb 2020 13:40:43 -0500 Received: from callcc.thunk.org (75-104-88-164.mobility.exede.net [75.104.88.164] (may be forged)) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id 01TIeOgp027765 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Sat, 29 Feb 2020 13:40:31 -0500 Received: by callcc.thunk.org (Postfix, from userid 15806) id 7F1D242045B; Sat, 29 Feb 2020 13:40:23 -0500 (EST) Date: Sat, 29 Feb 2020 13:40:23 -0500 From: "Theodore Y. Ts'o" To: Jan Kara Cc: Qian Cai , jack@suse.com, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] fs/jbd2: fix data races at struct journal_head Message-ID: <20200229184023.GE7378@mit.edu> References: <20200222043111.2227-1-cai@lca.pw> <20200224091051.GC27857@quack2.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200224091051.GC27857@quack2.suse.cz> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 24, 2020 at 10:10:51AM +0100, Jan Kara wrote: > On Fri 21-02-20 23:31:11, Qian Cai wrote: > > journal_head::b_transaction and journal_head::b_next_transaction could > > be accessed concurrently as noticed by KCSAN, > > > > LTP: starting fsync04 > > /dev/zero: Can't open blockdev > > EXT4-fs (loop0): mounting ext3 file system using the ext4 subsystem > > EXT4-fs (loop0): mounted filesystem with ordered data mode. Opts: (null) > > ================================================================== > > BUG: KCSAN: data-race in __jbd2_journal_refile_buffer [jbd2] / jbd2_write_access_granted [jbd2] > > > > write to 0xffff99f9b1bd0e30 of 8 bytes by task 25721 on cpu 70: > > __jbd2_journal_refile_buffer+0xdd/0x210 [jbd2] > > __jbd2_journal_refile_buffer at fs/jbd2/transaction.c:2569 > > jbd2_journal_commit_transaction+0x2d15/0x3f20 [jbd2] > > (inlined by) jbd2_journal_commit_transaction at fs/jbd2/commit.c:1034 > > kjournald2+0x13b/0x450 [jbd2] > > kthread+0x1cd/0x1f0 > > ret_from_fork+0x27/0x50 > > > > read to 0xffff99f9b1bd0e30 of 8 bytes by task 25724 on cpu 68: > > jbd2_write_access_granted+0x1b2/0x250 [jbd2] > > jbd2_write_access_granted at fs/jbd2/transaction.c:1155 > > jbd2_journal_get_write_access+0x2c/0x60 [jbd2] > > __ext4_journal_get_write_access+0x50/0x90 [ext4] > > ext4_mb_mark_diskspace_used+0x158/0x620 [ext4] > > ext4_mb_new_blocks+0x54f/0xca0 [ext4] > > ext4_ind_map_blocks+0xc79/0x1b40 [ext4] > > ext4_map_blocks+0x3b4/0x950 [ext4] > > _ext4_get_block+0xfc/0x270 [ext4] > > ext4_get_block+0x3b/0x50 [ext4] > > __block_write_begin_int+0x22e/0xae0 > > __block_write_begin+0x39/0x50 > > ext4_write_begin+0x388/0xb50 [ext4] > > generic_perform_write+0x15d/0x290 > > ext4_buffered_write_iter+0x11f/0x210 [ext4] > > ext4_file_write_iter+0xce/0x9e0 [ext4] > > new_sync_write+0x29c/0x3b0 > > __vfs_write+0x92/0xa0 > > vfs_write+0x103/0x260 > > ksys_write+0x9d/0x130 > > __x64_sys_write+0x4c/0x60 > > do_syscall_64+0x91/0xb05 > > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > > > 5 locks held by fsync04/25724: > > #0: ffff99f9911093f8 (sb_writers#13){.+.+}, at: vfs_write+0x21c/0x260 > > #1: ffff99f9db4c0348 (&sb->s_type->i_mutex_key#15){+.+.}, at: ext4_buffered_write_iter+0x65/0x210 [ext4] > > #2: ffff99f5e7dfcf58 (jbd2_handle){++++}, at: start_this_handle+0x1c1/0x9d0 [jbd2] > > #3: ffff99f9db4c0168 (&ei->i_data_sem){++++}, at: ext4_map_blocks+0x176/0x950 [ext4] > > #4: ffffffff99086b40 (rcu_read_lock){....}, at: jbd2_write_access_granted+0x4e/0x250 [jbd2] > > irq event stamp: 1407125 > > hardirqs last enabled at (1407125): [] __find_get_block+0x107/0x790 > > hardirqs last disabled at (1407124): [] __find_get_block+0x49/0x790 > > softirqs last enabled at (1405528): [] __do_softirq+0x34c/0x57c > > softirqs last disabled at (1405521): [] irq_exit+0xa2/0xc0 > > > > Reported by Kernel Concurrency Sanitizer on: > > CPU: 68 PID: 25724 Comm: fsync04 Tainted: G L 5.6.0-rc2-next-20200221+ #7 > > Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40 07/10/2019 > > > > The plain reads are outside of jh->b_state_lock critical section which result > > in data races. Fix them by adding pairs of READ|WRITE_ONCE(). > > > > Signed-off-by: Qian Cai > > Yeah, makes sense. You can add: > > Reviewed-by: Jan Kara Thanks, applied. - Ted