[Ocfs2-devel] [PATCH] ocfs2: wait for recovering done after direct unlock request
Changwei Ge
ge.changwei at h3c.com
Mon Feb 18 18:27:18 PST 2019
Hi Jun,
On 2019/2/19 9:16, piaojun wrote:
> Hi Changwei,
>
> Thanks for your patient explaination, and I get your point. But I have
> some suggestion about your patch below.
Thanks your advise to this patch.
>
> On 2019/2/18 17:46, Changwei Ge wrote:
>> Hi Jun,
>>
>> Ping...
>>
>> Do you have any further question?
>> If any question uncleared, please let me know.
>> Otherwise, could you please give a feedback?
>>
>> Thanks,
>> Changwei
>>
>> On 2019/2/15 16:48, Changwei Ge wrote:
>>> Hi Jun,
>>>
>>> On 2019/2/15 16:36, piaojun wrote:
>>>> Hi Changwei,
>>>>
>>>> Thanks for your explaination, and I still have a question below.
>>>
>>> Thank you for looking into this.
>>>
>>>>
>>>> On 2019/2/15 14:29, Changwei Ge wrote:
>>>>> Hi Jun,
>>>>>
>>>>> On 2019/2/15 14:20, piaojun wrote:
>>>>>> Hi Changwei,
>>>>>>
>>>>>> The DLM process is a little bit complex, so I suggest pasting the code
>>>>>> path. And I wonder if my code is right?
>>>>>>
>>>>>> Thanks,
>>>>>> Jun
>>>>>>
>>>>>> On 2019/2/14 14:14, Changwei Ge wrote:
>>>>>>> There is scenario causing ocfs2 umount hang when multiple hosts are
>>>>>>> rebooting at the same time.
>>>>>>>
>>>>>>> NODE1 NODE2 NODE3
>>>>>>> send unlock requset to NODE2
>>>>>>> dies
>>>>>>> become recovery master
>>>>>>> recover NODE2
>>>>>>> find NODE2 dead
>>>>>>> mark resource RECOVERING
>>>>>>> directly remove lock from grant list
>>>>>> dlm_do_local_recovery_cleanup
>>>>>> dlm_move_lockres_to_recovery_list
>>>>>> res->state |= DLM_LOCK_RES_RECOVERING;
>>>>>> list_add_tail(&res->recovering, &dlm->reco.resources);
>>>>>>
>>>>>>> calculate usage but RECOVERING marked
>>>>>>> **miss the window of purging
>>>>>> dlmunlock
>>>>>> dlmunlock_remote
>>>>>> dlmunlock_common // unlock successfully directly
>>>>>>
>>>>>> dlm_lockres_calc_usage
>>>>>> __dlm_lockres_calc_usage
>>>>>> __dlm_lockres_unused
>>>>>> if (res->state & (DLM_LOCK_RES_RECOVERING| // won't purge lock as DLM_LOCK_RES_RECOVERING is set
>>>>>
>>>>> True.
>>>>>
>>>>>>
>>>>>>> clear RECOVERING
>>>>>> dlm_finish_local_lockres_recovery
>>>>>> res->state &= ~DLM_LOCK_RES_RECOVERING;
>>>>>>
>>>>>> Could you help explaining where getting stuck?
>>>>>
>>>>> Sure,
>>>>> As dlm missed the window to purge lock resource, it can't be unhashed.
>>>>>
>>>>> During umount:
>>>>> dlm_unregister_domain
>>>>> dlm_migrate_all_locks -> there is always a lock resource hashed, so can't return from dlm_migrate_all_locks() thus hang during umount.
>>>>
>>>> In dlm_migrate_all_locks, lockres will be move to purge_list and purged again:
>>>> dlm_migrate_all_locks
>>>> __dlm_lockres_calc_usage
>>>> list_add_tail(&res->purge, &dlm->purge_list);
>>>>
>>>> Do you mean this process does not work?
>>>
>>> Yes, only for Migrating lock resources, it has a chance to call __dlm_lockres_calc_usage()
>>> But in our situation, the problematic lock resource is obviously no master. So no chance for it to set stack variable *dropped* in dlm_migrate_all_locks()
>>>
>>> Thanks,
>>> Changwei
>>>
>>>>
>>>>>
>>>>> Thanks,
>>>>> Changwei
>>>>>
>>>>>
>>>>>>
>>>>>>>
>>>>>>> To reproduce this iusse, crash a host and then umount ocfs2
>>>>>>> from another node.
>>>>>>>
>>>>>>> To sovle this, just let unlock progress wait for recovery done.
>>>>>>>
>>>>>>> Signed-off-by: Changwei Ge <ge.changwei at h3c.com>
>>>>>>> ---
>>>>>>> fs/ocfs2/dlm/dlmunlock.c | 23 +++++++++++++++++++----
>>>>>>> 1 file changed, 19 insertions(+), 4 deletions(-)
>>>>>>>
>>>>>>> diff --git a/fs/ocfs2/dlm/dlmunlock.c b/fs/ocfs2/dlm/dlmunlock.c
>>>>>>> index 63d701c..c8e9b70 100644
>>>>>>> --- a/fs/ocfs2/dlm/dlmunlock.c
>>>>>>> +++ b/fs/ocfs2/dlm/dlmunlock.c
>>>>>>> @@ -105,7 +105,8 @@ static enum dlm_status dlmunlock_common(struct dlm_ctxt *dlm,
>>>>>>> enum dlm_status status;
>>>>>>> int actions = 0;
>>>>>>> int in_use;
>>>>>>> - u8 owner;
>>>>>>> + u8 owner;
>>>>>>> + int recovery_wait = 0;
>>>>>>>
>>>>>>> mlog(0, "master_node = %d, valblk = %d\n", master_node,
>>>>>>> flags & LKM_VALBLK);
>>>>>>> @@ -208,9 +209,12 @@ static enum dlm_status dlmunlock_common(struct dlm_ctxt *dlm,
>>>>>>> }
>>>>>>> if (flags & LKM_CANCEL)
>>>>>>> lock->cancel_pending = 0;
>>>>>>> - else
>>>>>>> - lock->unlock_pending = 0;
>>>>>>> -
>>>>>>> + else {
>>>>>>> + if (!lock->unlock_pending)
>>>>>>> + recovery_wait = 1;
>
> Could we just check if res->state is in DLM_LOCK_RES_RECOVERING or
> status is DLM_RECOVERING? And there is no need to define an extra
> variable.
As the lock resource master had died, DLM_RECOVERING can't be returned.
I prefer adding a stack variable like *recovery_wait* to tell if involved lock resource has a chance to be recovered.
In this way, we won't make code subtle comparing with normal code path. As you know, the case we discuss here is not
that possible to happen when each node in cluster works well. And we can also save some CPU cycles this way.
Thanks,
Changwei
>
>>>>>>> + else
>>>>>>> + lock->unlock_pending = 0;
>>>>>>> + }
>>>>>>> }
>>>>>>>
>>>>>>> /* get an extra ref on lock. if we are just switching
>>>>>>> @@ -244,6 +248,17 @@ static enum dlm_status dlmunlock_common(struct dlm_ctxt *dlm,
>>>>>>> spin_unlock(&res->spinlock);
>>>>>>> wake_up(&res->wq);
>>>>>>>
>>>>>>> + if (recovery_wait) {
>>>>>>> + spin_lock(&res->spinlock);
>>>>>>> + /* Unlock request will directly succeed after owner dies,
>>>>>>> + * and the lock is already removed from grant list. We have to
>>>>>>> + * wait for RECOVERING done or we miss the chance to purge it
>>>>>>> + * since the removement is much faster than RECOVERING proc.
>>>>>>> + */
>>>>>>> + __dlm_wait_on_lockres_flags(res, DLM_LOCK_RES_RECOVERING);
>>>>>>> + spin_unlock(&res->spinlock);
>>>>>>> + }
>>>>>>> +
>>>>>>> /* let the caller's final dlm_lock_put handle the actual kfree */
>>>>>>> if (actions & DLM_UNLOCK_FREE_LOCK) {
>>>>>>> /* this should always be coupled with list removal */
>>>>>>>
>>>>>>
>>>>> .
>>>>>
>>>>
>>>
>>> _______________________________________________
>>> Ocfs2-devel mailing list
>>> Ocfs2-devel at oss.oracle.com
>>> https://oss.oracle.com/mailman/listinfo/ocfs2-devel
>>>
>> .
>>
>
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