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<pre>Hi Changwei,
What I said is not the conversion cancellation success. For the dlm_send_remote_unlock_request function
called in the dlmunlock_common function, If the node is aware that the master of the lock resource is dead at this time,
the dlm_send_remote_unlock_request function will return DLM_NORMAL (at this time it also considers the execution to succeed).
DLM_LKSB_GET_LVB and DLM_LKSB_PUT_LVB are then cleared at the end of the dlm_send_remote_unlock_request function.
Let us look at dlm_send_remote_unlock_request function. The dlm_is_host_down function returns true and
the dlm_is_node_dead function returns true, then The dlm_send_remote_unlock_request function will returns true.
Also, this problem is not caused by the same problem that my other patch solves. In the scenario
that caused another bug (dlm/dlmrecovery.c 2137), the dlm_send_remote_unlock_request function has not been called yet.
Thanks,
Jian
</pre>
<div class="moz-cite-prefix">On 12/8/2018 4:14 PM, Changwei Ge
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:63ADC13FD55D6546B7DECE290D39E37301277F2187@H3CMLB12-EX.srv.huawei-3com.com">
<pre class="moz-quote-pre" wrap="">On 2018/12/8 15:40, wangjian wrote:
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">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.
</pre>
</blockquote>
<pre class="moz-quote-pre" wrap="">
Aha... I got your point and what's the problem like.
So as the old master died Node3 thinks that the conversion cancellation succeeds and thus clears _DLM_LKSB_PUT_LVB_ and _DLM_LKSB_GET_LVB_ in dlmunlock_common().
But before that dlm recovery procedure had already sent lksb of lock to the *new* master, right? Um, so we have a very fast dlm recovery progress. :-)
I admit its possibility.
So actually, we can justify if conversion cancellation succeeds or not like your another patch, right?
If we already know we had a field conversion cancellation, why we still clear _DLM_LKSB_PUT_LVB_ and _DLM_LKSB_GET_LVB_ ?
And IMO in your case sending _DLM_LKSB_PUT_LVB_ and _DLM_LKSB_GET_LVB_ to *new* master makes sense as we still can ask the new master transfer LVB back to boost performace.
So I prefer to merge your two patches addressing the problems and I think they have the same root cause.
Thanks,
Changwei
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">
Thanks,
Jian
On 12/7/2018 11:40 AM, Changwei Ge wrote:
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">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:
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">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:
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">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:
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">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<a class="moz-txt-link-rfc2396E" href="mailto:wangjian161@huawei.com"><wangjian161@huawei.com></a>
Reviewed-by: Yiwen Jiang<a class="moz-txt-link-rfc2396E" href="mailto:jiangyiwen@huawei.com"><jiangyiwen@huawei.com></a>
---
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
</pre>
</blockquote>
<pre class="moz-quote-pre" wrap="">.
</pre>
</blockquote>
</blockquote>
<pre class="moz-quote-pre" wrap="">.
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