From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-eopbgr50070.outbound.protection.outlook.com ([40.107.5.70]:53760 "EHLO EUR03-VE1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1759487AbdKRM3v (ORCPT ); Sat, 18 Nov 2017 07:29:51 -0500 Subject: Re: 4.14 balance: kernel BUG at /home/kernel/COD/linux/fs/btrfs/ctree.c:1856! From: Hans van Kranenburg To: Roman Mamedov Cc: Tomasz Chmielewski , Btrfs BTRFS References: <5000f429-8b4b-b4ea-5e38-89f7c91af6f3@mendix.com> <20171118144037.0fa8ad4b@natsu> <2cbd136b-4fa7-fcee-7472-0941efa97047@mendix.com> Message-ID: <909afcf3-3eff-52eb-c679-4e300dd61bda@mendix.com> Date: Sat, 18 Nov 2017 13:29:45 +0100 MIME-Version: 1.0 In-Reply-To: <2cbd136b-4fa7-fcee-7472-0941efa97047@mendix.com> Content-Type: text/plain; charset=utf-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 11/18/2017 12:48 PM, Hans van Kranenburg wrote: > > So, who wants to help? > > 1. Find a test system that you can crash. > 2. Create a test filesystem with some data. > 3. Run with 4.14? (makes the most sense I think) > 4. Continuously feed the data to balance and send everything to /dev/null > 5. Collect stack traces and borken filesystem images. Ok, what I just did: -# mkfs.btrfs --nodiscard /dev/xvdb -# mount -o noatime /dev/xvdb /btrfs -# cd btrfs/ -# btrfs sub create usr -# rsync -av /usr/ usr/ -# btrfs sub snap -r usr/ usro And then, both at the same time: -# while true; do btrfs send usro/ > /dev/null; date; echo 3 > /proc/sys/vm/drop_caches; done and -# while true; do btrfs balance start --full-balance /btrfs; done After a few minutes we have the first error: [ 1605.484627] BTRFS error (device xvdb): did not find backref in send_root. inode=4260, offset=0, disk_byte=130793844736 found extent=130793844736 Sat Nov 18 13:25:28 CET 2017 At subvol usro/ ERROR: send ioctl failed with -5: Input/output error No big stack trace this time. -- Hans van Kranenburg