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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 205F4C48BCD for ; Wed, 9 Jun 2021 16:31:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E66DE613C0 for ; Wed, 9 Jun 2021 16:31:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233417AbhFIQdQ (ORCPT ); Wed, 9 Jun 2021 12:33:16 -0400 Received: from www262.sakura.ne.jp ([202.181.97.72]:58891 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232165AbhFIQdQ (ORCPT ); Wed, 9 Jun 2021 12:33:16 -0400 Received: from fsav109.sakura.ne.jp (fsav109.sakura.ne.jp [27.133.134.236]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id 159GVKkL099910; Thu, 10 Jun 2021 01:31:20 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav109.sakura.ne.jp (F-Secure/fsigk_smtp/550/fsav109.sakura.ne.jp); Thu, 10 Jun 2021 01:31:20 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/fsav109.sakura.ne.jp) Received: from [192.168.1.9] (M106072142033.v4.enabler.ne.jp [106.72.142.33]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id 159GVJHY099907 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NO); Thu, 10 Jun 2021 01:31:19 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: Re: [syzbot] possible deadlock in del_gendisk From: Tetsuo Handa To: Christoph Hellwig , Jens Axboe , Stefan Haberland , Jan Hoeppner Cc: linux-block , syzbot , Tyler Hicks , Petr Vorel , Pavel Tatashin , Tejun Heo References: <000000000000ae236f05bfde0678@google.com> <1435f266-9f6d-22ef-ba7d-f031c616aede@I-love.SAKURA.ne.jp> Message-ID: <7b8c9eeb-789d-e5e6-04d6-130ee8be7305@i-love.sakura.ne.jp> Date: Thu, 10 Jun 2021 01:31:17 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <1435f266-9f6d-22ef-ba7d-f031c616aede@I-love.SAKURA.ne.jp> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Hello, Christoph. I'm currently trying full bisection. # bad: [fc0586062816559defb14c947319ef8c4c326fb3] Merge tag 'for-5.13/drivers-2021-04-27' of git://git.kernel.dk/linux-block # good: [42dec9a936e7696bea1f27d3c5a0068cd9aa95fd] Merge tag 'perf-core-2021-04-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip # good: [68a32ba14177d4a21c4a9a941cf1d7aea86d436f] Merge tag 'drm-next-2021-04-28' of git://anongit.freedesktop.org/drm/drm # good: [a800abd3ecb9acc55821f7ac9bba6c956b36a595] net: enetc: move skb creation into enetc_build_skb # good: [6cc8e7430801fa238bd7d3acae1eb406c6e02fe1] loop: scale loop device by introducing per device lock git bisect start 'fc0586062816559defb14c947319ef8c4c326fb3' '42dec9a936e7696bea1f27d3c5a0068cd9aa95fd' '68a32ba14177d4a21c4a9a941cf1d7aea86d436f' 'a800abd3ecb9acc55821f7ac9bba6c956b36a595' '6cc8e7430801fa238bd7d3acae1eb406c6e02fe1' # good: [2958a995edc94654df690318df7b9b49e5a3ef88] block/rnbd-clt: Support polling mode for IO latency optimization git bisect good 2958a995edc94654df690318df7b9b49e5a3ef88 I think we will bisect this problem to commit c76f48eb5c084b1e ("block: take bd_mutex around delete_partitions in del_gendisk") because that commit introduced new locking dependency bdev_lookup_sem => disk->part0->bd_mutex which matches the lockdep's report. ====================================================== WARNING: possible circular locking dependency detected 5.12.0-rc6-next-20210409-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.4/10285 is trying to acquire lock: ffff8881423245a0 (&bdev->bd_mutex){+.+.}-{3:3}, at: del_gendisk+0x250/0x9e0 block/genhd.c:618 but task is already holding lock: ffffffff8c7d9430 (bdev_lookup_sem){++++}-{3:3}, at: del_gendisk+0x222/0x9e0 block/genhd.c:616 Do we need to revert "partition iteration simplifications" work? On 2021/06/07 19:56, Tetsuo Handa wrote: > Hello. > > syzbot is reporting "possible deadlock in del_gendisk" problem. > > I guess this is caused by commit 6cc8e7430801fa23 ("loop: scale loop device > by introducing per device lock") because it touches loop_ctl_mutex usage > between v5.11 and v5.12-rc1. Please have a look. > > On 2021/04/14 2:33, syzbot wrote: >> Hello, >> >> syzbot found the following issue on: >> >> HEAD commit: e99d8a84 Add linux-next specific files for 20210409 >> git tree: linux-next >> console output: https://syzkaller.appspot.com/x/log.txt?x=13b01681d00000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=7cd69574979bfeb7 >> dashboard link: https://syzkaller.appspot.com/bug?extid=61e04e51b7ac86930589 >> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=148265d9d00000 >> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16a981a1d00000 >