From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:42005 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756867AbcJMVUE (ORCPT ); Thu, 13 Oct 2016 17:20:04 -0400 Subject: Re: btrfs bio linked list corruption. To: Dave Jones , Al Viro , Josef Bacik , David Sterba , , Linux Kernel References: <20161011144507.okg6baqvodn2m2lh@codemonkey.org.uk> <20161012134717.n74tww5eywc7dqp7@codemonkey.org.uk> <20161012144012.7vvfehceoykswmun@codemonkey.org.uk> <20161013181622.qpi5puv6ivxvslnf@codemonkey.org.uk> From: Chris Mason Message-ID: <7b476728-75f8-e3d3-1261-b9b0d598ed10@fb.com> Date: Thu, 13 Oct 2016 17:18:46 -0400 MIME-Version: 1.0 In-Reply-To: <20161013181622.qpi5puv6ivxvslnf@codemonkey.org.uk> Content-Type: text/plain; charset="windows-1252"; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 10/13/2016 02:16 PM, Dave Jones wrote: > On Wed, Oct 12, 2016 at 10:42:46AM -0400, Chris Mason wrote: > > On 10/12/2016 10:40 AM, Dave Jones wrote: > > > On Wed, Oct 12, 2016 at 09:47:17AM -0400, Dave Jones wrote: > > > > On Tue, Oct 11, 2016 at 11:54:09AM -0400, Chris Mason wrote: > > > > > > > > > > > > > > > On 10/11/2016 10:45 AM, Dave Jones wrote: > > > > > > This is from Linus' current tree, with Al's iovec fixups on top. > > > > > > > > > > > > ------------[ cut here ]------------ > > > > > > WARNING: CPU: 1 PID: 3673 at lib/list_debug.c:33 __list_add+0x89/0xb0 > > > > > > list_add corruption. prev->next should be next (ffffe8ffff806648), but was ffffc9000067fcd8. (prev=ffff880503878b80). > > > > > > CPU: 1 PID: 3673 Comm: trinity-c0 Not tainted 4.8.0-think+ #13 > > > > > > ffffc90000d87458 ffffffff8d32007c ffffc90000d874a8 0000000000000000 > > > > > > ffffc90000d87498 ffffffff8d07a6c1 0000002100000246 ffff88050388e880 > > > > > > > > I hit this again overnight, it's the same trace, the only difference > > > > being slightly different addresses in the list pointers: > > > > > > > > [42572.777196] list_add corruption. prev->next should be next (ffffe8ffff806648), but was ffffc90000647cd8. (prev=ffff880503a0ba00). > > > > > > > > I'm actually a little surprised that ->next was the same across two > > > > reboots on two different kernel builds. That might be a sign this is > > > > more repeatable than I'd thought, even if it does take hours of runtime > > > > right now to trigger it. I'll try and narrow the scope of what trinity > > > > is doing to see if I can make it happen faster. > > > > > > .. and of course the first thing that happens is a completely different > > > btrfs trace.. > > > > > > > > > WARNING: CPU: 1 PID: 21706 at fs/btrfs/transaction.c:489 start_transaction+0x40a/0x440 [btrfs] > > > CPU: 1 PID: 21706 Comm: trinity-c16 Not tainted 4.8.0-think+ #14 > > > ffffc900019076a8 ffffffffb731ff3c 0000000000000000 0000000000000000 > > > ffffc900019076e8 ffffffffb707a6c1 000001e9f5806ce0 ffff8804f74c4d98 > > > 0000000000000801 ffff880501cfa2a8 000000000000008a 000000000000008a > > > > This isn't even IO. Uuughhhh. We're going to need a fast enough test > > that we can bisect. > > Progress... > I've found that this combination of syscalls.. > > ./trinity -C64 -q -l off -a64 --enable-fds=testfile -c fsync -c fsetxattr -c lremovexattr -c pwritev2 > > hits one of these two bugs in a few minutes runtime. > > Just the xattr syscalls + fsync isn't enough, neither is just pwrite + fsync. > Mix them together though, and something goes awry. > Hasn't triggered here yet. I'll leave it running though. -chris