From: Joseph Qi <joseph.qi@linux.alibaba.com>
To: Gang He <ghe@suse.com>,
mark@fasheh.com, jlbec@evilplan.org,
Wengang Wang <wen.gang.wang@oracle.com>
Cc: linux-kernel@vger.kernel.org, ocfs2-devel@oss.oracle.com
Subject: Re: [Ocfs2-devel] [PATCH] ocfs2: reflink deadlock when clone file to the same directory simultaneously
Date: Wed, 18 Aug 2021 19:20:45 +0800 [thread overview]
Message-ID: <86e3d724-3147-ccaa-998f-0f857c575f7e@linux.alibaba.com> (raw)
In-Reply-To: <801438f5-655a-c708-aa25-343d54a2f11e@suse.com>
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?
IMO, we'd better directly fix the stack user hang first, and then optimize
reflink performance.
Thanks,
Joseph
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next prev parent reply other threads:[~2021-08-18 11:21 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-29 11:02 [Ocfs2-devel] [PATCH] ocfs2: reflink deadlock when clone file to the same directory simultaneously Gang He
2021-07-29 22:07 ` Wengang Wang
2021-07-30 6:16 ` Gang He
2021-07-30 16:35 ` Wengang Wang
2021-08-02 4:35 ` Gang He
2021-08-02 18:22 ` Wengang Wang
2021-08-03 1:00 ` Gang He
2021-08-03 20:08 ` Wengang Wang
2021-08-04 1:57 ` Joseph Qi
2021-08-09 10:08 ` Gang He
2021-08-13 9:54 ` Joseph Qi
2021-08-18 9:20 ` Gang He
2021-08-18 11:20 ` Joseph Qi [this message]
2021-08-19 1:51 ` Gang He
2021-08-19 2:02 ` Joseph Qi
2021-08-19 6:31 ` Gang He
2021-08-26 5:56 ` Gang He
2022-10-16 23:29 ` Andrew Morton via Ocfs2-devel
2022-10-17 1:51 ` Joseph Qi via Ocfs2-devel
2022-10-17 2:29 ` Andrew Morton via Ocfs2-devel
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