[Ocfs2-devel] [PATCH] ocfs2/dlm: Clean DLM_LKSB_GET_LVB and DLM_LKSB_PUT_LVB when the cancel_pending is set
wangjian
wangjian161 at huawei.com
Fri Dec 7 23:40:07 PST 2018
Hi Changwei,
What do you mean by setting the LVB bit to be 428 lines of memcpy?
If so, you should realize that under the scenario and problem solving method I mentioned,
the result of the last AST processing of the if statement in line 426 is false.
This is indeed a more complicated anomaly scenario,
and you may not fully understand the scenario I mentioned above.
Below I will describe the key points of this scenario again.
The master of the lock resource has died. Because Node3 is in the cancel_convert process,
Node3 moves the lock to the grant queue in the dlm_move_lockres_to_recovery_list
function (the DLM_LKSB_GET_LVB and DLM_LKSB_PUT_LVB are not cleared).
The lock information is sent to the new master (Node4) during the recovery process.
Then the cancel_convert process clears DLM_LKSB_GET_LVB and DLM_LKSB_PUT_LVB.
The lock_3 information on the new master (Node4) is inconsistent with
the local lock_3 information on Node3, causing a BUG to occur when Node3 receives the AST.
Thanks,
Jian
On 12/7/2018 11:40 AM, Changwei Ge wrote:
> Hi Jian,
>
> Um...
> I am a little puzzled after delving into this patch.
>
> Do you mean the BUG check below?
> '''
> 425 /* if we requested the lvb, fetch it into our lksb now */
> 426 if (flags & LKM_GET_LVB) {
> 427 BUG_ON(!(lock->lksb->flags & DLM_LKSB_GET_LVB));
> 428 memcpy(lock->lksb->lvb, past->lvb, DLM_LVB_LEN);
> 429 }
>
> '''
>
> If so, you clear DLM_LKSB_GET_LVB in dlm_commit_pending_cancel() and how could the LVB bit be set in dlm_proxy_ast_handler()?
>
> Thanks,
> Changwei
>
>
> On 2018/12/6 19:54, wangjian wrote:
>> Hi Changwei,
>>
>> The core information that causes the bug in the dlm_proxy_ast_handler function is as follows.
>>
>> [ 699.795843] kernel BUG at /home/Euler_compile_env/usr/src/linux-4.18/fs/ocfs2/dlm/dlmast.c:427!
>> [ 699.797525] invalid opcode: 0000 [#1] SMP NOPTI
>> [ 699.798383] CPU: 8 PID: 510 Comm: kworker/u24:1 Kdump: loaded Tainted: G OE 4.18.0 #1
>> [ 699.800002] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 09/30/2014
>> [ 699.801963] Workqueue: o2net o2net_rx_until_empty [ocfs2_nodemanager]
>> [ 699.803275] RIP: 0010:dlm_proxy_ast_handler+0x738/0x740 [ocfs2_dlm]
>> [ 699.804710] Code: 00 10 48 8d 7c 24 48 48 89 44 24 48 48 c7 c1 f1 35 92 c0 ba 30 01 00 00 48 c7 c6 30 a9 91 c0 31 c0 e8
>> ac 88 fb ff 0f 0b 0f 0b <0f> 0b 66 0f 1f 44 00 00 0f 1f 44 00 00 55 48 89 e5 41 57 45 89 c7
>> [ 699.808506] RSP: 0018:ffffba64c6f2fd38 EFLAGS: 00010246
>> [ 699.809456] RAX: ffff9f34a9b39148 RBX: ffff9f30b7af4000 RCX: ffff9f34a9b39148
>> [ 699.810698] RDX: 000000000000019e RSI: ffffffffc091a930 RDI: ffffba64c6f2fd80
>> [ 699.811927] RBP: ffff9f2cb7aa3000 R08: ffff9f2cb7b99400 R09: 000000000000001f
>> [ 699.813457] R10: ffff9f34a9249200 R11: ffff9f34af23aa00 R12: 0000000040000000
>> [ 699.814719] R13: ffff9f34a9249210 R14: 0000000000000002 R15: ffff9f34af23aa28
>> [ 699.815984] FS: 0000000000000000(0000) GS:ffff9f32b7c00000(0000) knlGS:0000000000000000
>> [ 699.817417] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> [ 699.818825] CR2: 00007fd772f5a140 CR3: 000000005b00a001 CR4: 00000000001606e0
>> [ 699.820123] Call Trace:
>> [ 699.820658] o2net_rx_until_empty+0x94b/0xcc0 [ocfs2_nodemanager]
>> [ 699.821848] process_one_work+0x171/0x370
>> [ 699.822595] worker_thread+0x49/0x3f0
>> [ 699.823301] kthread+0xf8/0x130
>> [ 699.823972] ? max_active_store+0x80/0x80
>> [ 699.824881] ? kthread_bind+0x10/0x10
>> [ 699.825589] ret_from_fork+0x35/0x40
>>
>> The reasons for clearing the LVB flag are as follows. First, The owner of the lock resource
>> may have died, the lock has been moved to the grant queue, the purpose of the lock
>> cancellation has been reached, and the LVB flag should be cleared. Second, solve this panic problem.
>>
>> Thanks,
>> Jian
>>
>> On 12/5/2018 10:01 AM, Changwei Ge wrote:
>>> Hi Jian,
>>>
>>> Could your please also share the panic backtrace in dlm_proxy_ast_handler()?
>>> After that I can help to review this patch and analyze what's wrong in DLM.
>>>
>>> It will be better for you to tell your intention why LVB flags should be cleared rather
>>> than just giving a longggg time sequence diagram.
>>>
>>> Moreover, your patches are hard be applied to my tree :(
>>>
>>> Thanks,
>>> Changwei
>>>
>>>
>>> On 2018/12/3 20:08, wangjian wrote:
>>>> Function dlm_move_lockres_to_recovery_list should clean
>>>> DLM_LKSB_GET_LVB and DLM_LKSB_PUT_LVB when the cancel_pending
>>>> is set. Otherwise node may panic in dlm_proxy_ast_handler.
>>>>
>>>> Here is the situation: At the beginning, Node1 is the master
>>>> of the lock resource and has NL lock, Node2 has PR lock,
>>>> Node3 has PR lock, Node4 has NL lock.
>>>>
>>>> Node1 Node2 Node3 Node4
>>>> convert lock_2 from
>>>> PR to EX.
>>>>
>>>> the mode of lock_3 is
>>>> PR, which blocks the
>>>> conversion request of
>>>> Node2. move lock_2 to
>>>> conversion list.
>>>>
>>>> convert lock_3 from
>>>> PR to EX.
>>>>
>>>> move lock_3 to conversion
>>>> list. send BAST to Node3.
>>>>
>>>> receive BAST from Node1.
>>>> downconvert thread execute
>>>> canceling convert operation.
>>>>
>>>> Node2 dies because
>>>> the host is powered down.
>>>>
>>>> in dlmunlock_common function,
>>>> the downconvert thread set
>>>> cancel_pending. at the same
>>>> time, Node 3 realized that
>>>> Node 1 is dead, so move lock_3
>>>> back to granted list in
>>>> dlm_move_lockres_to_recovery_list
>>>> function and remove Node 1 from
>>>> the domain_map in
>>>> __dlm_hb_node_down function.
>>>> then downconvert thread failed
>>>> to send the lock cancellation
>>>> request to Node1 and return
>>>> DLM_NORMAL from
>>>> dlm_send_remote_unlock_request
>>>> function.
>>>>
>>>> become recovery master.
>>>>
>>>> during the recovery
>>>> process, send
>>>> lock_2 that is
>>>> converting form
>>>> PR to EX to Node4.
>>>>
>>>> during the recovery process,
>>>> send lock_3 in the granted list and
>>>> cantain the DLM_LKSB_GET_LVB
>>>> flag to Node4. Then downconvert thread
>>>> delete DLM_LKSB_GET_LVB flag in
>>>> dlmunlock_common function.
>>>>
>>>> Node4 finish recovery.
>>>> the mode of lock_3 is
>>>> PR, which blocks the
>>>> conversion request of
>>>> Node2, so send BAST
>>>> to Node3.
>>>>
>>>> receive BAST from Node4.
>>>> convert lock_3 from PR to NL.
>>>>
>>>> change the mode of lock_3
>>>> from PR to NL and send
>>>> message to Node3.
>>>>
>>>> receive message from
>>>> Node4. The message contain
>>>> LKM_GET_LVB flag, but the
>>>> lock->lksb->flags does not
>>>> contain DLM_LKSB_GET_LVB,
>>>> BUG_ON in dlm_proxy_ast_handler
>>>> function.
>>>>
>>>> Signed-off-by: Jian Wang<wangjian161 at huawei.com>
>>>> Reviewed-by: Yiwen Jiang<jiangyiwen at huawei.com>
>>>> ---
>>>> fs/ocfs2/dlm/dlmunlock.c | 1 +
>>>> 1 file changed, 1 insertion(+)
>>>>
>>>> diff --git a/fs/ocfs2/dlm/dlmunlock.c b/fs/ocfs2/dlm/dlmunlock.c
>>>> index 63d701c..6e04fc7 100644
>>>> --- a/fs/ocfs2/dlm/dlmunlock.c
>>>> +++ b/fs/ocfs2/dlm/dlmunlock.c
>>>> @@ -277,6 +277,7 @@ void dlm_commit_pending_cancel(struct dlm_lock_resource *res,
>>>> {
>>>> list_move_tail(&lock->list, &res->granted);
>>>> lock->ml.convert_type = LKM_IVMODE;
>>>> + lock->lksb->flags &= ~(DLM_LKSB_GET_LVB|DLM_LKSB_PUT_LVB);
>>>> }
>>>>
>>>>
>>>> --
>>>> 1.8.3.1
>>>>
>>> .
>>>
> .
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://oss.oracle.com/pipermail/ocfs2-devel/attachments/20181208/188b6ce1/attachment.html
More information about the Ocfs2-devel
mailing list