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=-7.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,UNPARSEABLE_RELAY,USER_AGENT_SANE_1 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 9B852C4338F for ; Thu, 19 Aug 2021 02:03:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7A7EC610A1 for ; Thu, 19 Aug 2021 02:03:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235616AbhHSCDe (ORCPT ); Wed, 18 Aug 2021 22:03:34 -0400 Received: from out30-43.freemail.mail.aliyun.com ([115.124.30.43]:40273 "EHLO out30-43.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235433AbhHSCDd (ORCPT ); Wed, 18 Aug 2021 22:03:33 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R481e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04420;MF=joseph.qi@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0UjtBWdz_1629338576; Received: from B-D1K7ML85-0059.local(mailfrom:joseph.qi@linux.alibaba.com fp:SMTPD_---0UjtBWdz_1629338576) by smtp.aliyun-inc.com(127.0.0.1); Thu, 19 Aug 2021 10:02:56 +0800 Subject: Re: [PATCH] ocfs2: reflink deadlock when clone file to the same directory simultaneously To: Gang He , mark@fasheh.com, jlbec@evilplan.org, Wengang Wang Cc: linux-kernel@vger.kernel.org, ocfs2-devel@oss.oracle.com, akpm@linux-foundation.org References: <20210729110230.18983-1-ghe@suse.com> <5821fd0f-2018-dc1b-a5c0-f948a7debff4@linux.alibaba.com> <71608a14-58f4-dba0-d695-fee65de89192@linux.alibaba.com> <801438f5-655a-c708-aa25-343d54a2f11e@suse.com> <86e3d724-3147-ccaa-998f-0f857c575f7e@linux.alibaba.com> From: Joseph Qi Message-ID: <4ba3b404-824b-90a3-ef43-9ab6510ee073@linux.alibaba.com> Date: Thu, 19 Aug 2021 10:02:55 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/19/21 9:51 AM, Gang He wrote: > > > On 2021/8/18 19:20, Joseph Qi wrote: >> >> >> On 8/18/21 5:20 PM, Gang He wrote: >>> >>> >>> On 2021/8/13 17:54, Joseph Qi wrote: >>>> >>>> >>>> On 8/9/21 6:08 PM, Gang He wrote: >>>>> Hi Joseph and All, >>>>> >>>>> The deadlock is caused by self-locking on one node. >>>>> There is three node cluster (mounted to /mnt/shared), the user run reflink command to clone the file to the same directory repeatedly, >>>>> e.g. >>>>>    reflink "/mnt/shared/test" \ >>>>>    "/mnt/shared/.snapshots/test.`date +%m%d%H%M%S`.`hostname`" >>>>> >>>>> After a while, the reflink process on each node is hung, the file system cannot be listed. >>>>> The problematic reflink command process is blocked by itself, e.g. the reflink process is hung at ghe-sle15sp2-nd2, >>>>> kernel: task:reflink         state:D stack:    0 pid:16992 ppid:  4530 >>>>> kernel: Call Trace: >>>>> kernel:  __schedule+0x2fd/0x750 >>>>> kernel:  ? try_to_wake_up+0x17b/0x4e0 >>>>> kernel:  schedule+0x2f/0xa0 >>>>> kernel:  schedule_timeout+0x1cc/0x310 >>>>> kernel:  ? __wake_up_common+0x74/0x120 >>>>> kernel:  wait_for_completion+0xba/0x140 >>>>> kernel:  ? wake_up_q+0xa0/0xa0 >>>>> kernel:  __ocfs2_cluster_lock.isra.41+0x3b5/0x820 [ocfs2] >>>>> kernel:  ? ocfs2_inode_lock_full_nested+0x1fc/0x960 [ocfs2] >>>>> kernel:  ocfs2_inode_lock_full_nested+0x1fc/0x960 [ocfs2] >>>>> kernel:  ocfs2_init_security_and_acl+0xbe/0x1d0 [ocfs2] >>>>> kernel:  ocfs2_reflink+0x436/0x4c0 [ocfs2] >>>>> kernel:  ? ocfs2_reflink_ioctl+0x2ca/0x360 [ocfs2] >>>>> kernel:  ocfs2_reflink_ioctl+0x2ca/0x360 [ocfs2] >>>>> kernel:  ocfs2_ioctl+0x25e/0x670 [ocfs2] >>>>> kernel:  do_vfs_ioctl+0xa0/0x680 >>>>> kernel:  ksys_ioctl+0x70/0x80 >>>>> >>>>> In fact, the destination directory(.snapshots) inode dlm lock was acquired by ghe-sle15sp2-nd2, next there is bast message from other nodes to ask ghe-sle15sp2-nd2 downconvert lock, but the operation failed, the kernel message is printed like, >>>>> kernel: (ocfs2dc-AA35DD9,2560,3):ocfs2_downconvert_lock:3660 ERROR: DLM error -16 while calling ocfs2_dlm_lock on resource M0000000000000000046e0200000000 >>>>> kernel: (ocfs2dc-AA35DD9,2560,3):ocfs2_unblock_lock:3904 ERROR: status = -16 >>>>> kernel: (ocfs2dc-AA35DD9,2560,3):ocfs2_process_blocked_lock:4303 ERROR: status = -16 >>>>> >>>>> Then, the reflink process tries to acquire this directory inode dlm lock, the process is blocked, the dlm lock resource in memory looks like >>>>> >>>>>       l_name = "M0000000000000000046e0200000000", >>>>>       l_ro_holders = 0, >>>>>       l_ex_holders = 0, >>>>>       l_level = 5 '\005', >>>>>       l_requested = 0 '\000', >>>>>       l_blocking = 5 '\005', >>>>>       l_type = 0 '\000', >>>>>       l_action = 0 '\000', >>>>>       l_unlock_action = 0 '\000', >>>>>       l_pending_gen = 645948, >>>>> >>>>> >>>>> So far, I do not know what makes dlm lock function failed, it also looks we do not handle this failure case in dlmglue layer, but I always reproduce this hang with my test script, e.g. >>>>> >>>>>     loop=1 >>>>>     while ((loop++)) ; do >>>>>           for i in `seq 1 100`; do >>>>>             reflink "/mnt/shared/test" "/mnt/shared/.snapshots /test.${loop}.${i}.`date +%m%d%H%M%S`.`hostname`" >>>>>           done >>>>>           usleep 500000 >>>>>           rm -f /mnt/shared/.snapshots/testnode1.qcow2.*.`hostname` >>>>>     done >>>>> >>>>> My patch changes multiple acquiring dest directory inode dlm lock during in ocfs2_reflink function, it avoids the hang issue happen again.The code change also can improve reflink performance in this case. >>>>> >>>>> Thanks >>>>> Gang >>>> >>>> 'status = -16' implies DLM_CANCELGRANT. >>>> Do you use stack user instead of o2cb? If yes, can you try o2cb with >>>> your reproducer? >>> >>> I setup o2cb based ocfs2 clusters with sle15sp2 and oracleLinux8u4. >>> After two day testing with the same script, I did not encounter dlm_lock downconvert failure, the hang issue did not happen. >>> After my patch was applied, there was not any side effect, the reflink performance was doubled in the case. >>> >> >> Do you mean the hang only happens on stack user? > Yes. > Why? since o2cb based dlm_lock did not return error -16 when downcovert dlm lock during the whole testing. > But pmck based dlm_lock retuned error -16 during the testing, then we did not handle this error further in dlmglue layer, next encounter the hang issue when dlm_lock acquire the lock. Maybe there is a race condition when using dlm_lock/dlm_unlock(cancel) in dlmglue layer. > Anyway, the problem belongs to ocfs2 own parts. > I meant if DLM_CANCELGRANT is not the expected return code, we'd better fix the issue in stack_user.c but not dlmglue, e.g. some specific wrapper. Thanks, Joseph