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<pre>Hi Changwei,
I don't fully agree with your point of view. In my opinion, the lock cancellation process and the lock
conversion process are asynchronous. We can't guarantee that the lock must be in the convert list
during the lock conversion process, otherwise this BUG will not happen.
So, I think this is a meaningless BUG.
Thanks,
Jian
</pre>
<div class="moz-cite-prefix">On 12/5/2018 9:49 AM, Changwei Ge
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:63ADC13FD55D6546B7DECE290D39E37301277EFAA1@H3CMLB12-EX.srv.huawei-3com.com">
<pre class="moz-quote-pre" wrap="">Hi Jian,
I suppose you can't just remove the BUG_ON() check.
If you remove it, below code violates the original logic.
'''
2141 dlm_commit_pending_cancel(res, lock);
'''
What's more important is *locking cancel* must be against a *locking conversion* progress.
So it makes sense to check if this lock is on converting list.
So I have to NACK to this patch.
Thanks,
Changwei
On 2018/12/3 20:23, wangjian wrote:
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">In the dlm_move_lockres_to_recovery_list function, if the lock
is in the granted queue and cancel_pending is set, it will
encounter a BUG. I think this is a meaningless BUG,
so be prepared to remove it. A scenario that causes
this BUG will be given below.
At the beginning, Node 1 is the master and has NL lock,
Node 2 has PR lock, Node 3 has PR lock too.
Node 1 Node 2 Node 3
want to get EX lock.
want to get EX lock.
Node 3 hinder
Node 2 to get
EX lock, send
Node 3 a BAST.
receive BAST from
Node 1. downconvert
thread begin to
cancel PR to EX conversion.
In dlmunlock_common function,
downconvert thread has set
lock->cancel_pending,
but did not enter
dlm_send_remote_unlock_request
function.
Node2 dies because
the host is powered down.
In recovery process,
clean the lock that
related to Node2.
then finish Node 3
PR to EX request.
give Node 3 a AST.
receive AST from Node 1.
change lock level to EX,
move lock to granted list.
Node1 dies because
the host is powered down.
In dlm_move_lockres_to_recovery_list
function. the lock is in the
granted queue and cancel_pending
is set. BUG_ON.
But after clearing this BUG, process will encounter
the second BUG in the ocfs2_unlock_ast function.
Here is a scenario that will cause the second BUG
in ocfs2_unlock_ast as follows:
At the beginning, Node 1 is the master and has NL lock,
Node 2 has PR lock, Node 3 has PR lock too.
Node 1 Node 2 Node 3
want to get EX lock.
want to get EX lock.
Node 3 hinder
Node 2 to get
EX lock, send
Node 3 a BAST.
receive BAST from
Node 1. downconvert
thread begin to
cancel PR to EX conversion.
In dlmunlock_common function,
downconvert thread has released
lock->spinlock and res->spinlock,
but did not enter
dlm_send_remote_unlock_request
function.
Node2 dies because
the host is powered down.
In recovery process,
clean the lock that
related to Node2.
then finish Node 3
PR to EX request.
give Node 3 a AST.
receive AST from Node 1.
change lock level to EX,
move lock to granted list,
set lockres->l_unlock_action
as OCFS2_UNLOCK_INVALID
in ocfs2_locking_ast function.
Node2 dies because
the host is powered down.
Node 3 realize that Node 1
is dead, remove Node 1 from
domain_map. downconvert thread
get DLM_NORMAL from
dlm_send_remote_unlock_request
function and set *call_ast as 1.
Then downconvert thread meet
BUG in ocfs2_unlock_ast function.
To avoid meet the second BUG, function dlmunlock_common shuold
return DLM_CANCELGRANT if the lock is on granted list and
the operation is canceled.
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/dlmrecovery.c | 1 -
fs/ocfs2/dlm/dlmunlock.c | 5 +++++
2 files changed, 5 insertions(+), 1 deletion(-)
diff --git a/fs/ocfs2/dlm/dlmrecovery.c b/fs/ocfs2/dlm/dlmrecovery.c
index 802636d..7489652 100644
--- a/fs/ocfs2/dlm/dlmrecovery.c
+++ b/fs/ocfs2/dlm/dlmrecovery.c
@@ -2134,7 +2134,6 @@ void dlm_move_lockres_to_recovery_list(struct dlm_ctxt *dlm,
* if this had completed successfully
* before sending this lock state to the
* new master */
- BUG_ON(i != DLM_CONVERTING_LIST);
mlog(0, "node died with cancel pending "
"on %.*s. move back to granted list.\n",
res->lockname.len, res->lockname.name);
diff --git a/fs/ocfs2/dlm/dlmunlock.c b/fs/ocfs2/dlm/dlmunlock.c
index 63d701c..505bb6c 100644
--- a/fs/ocfs2/dlm/dlmunlock.c
+++ b/fs/ocfs2/dlm/dlmunlock.c
@@ -183,6 +183,11 @@ static enum dlm_status dlmunlock_common(struct dlm_ctxt *dlm,
flags, owner);
spin_lock(&res->spinlock);
spin_lock(&lock->spinlock);
+
+ if ((flags & LKM_CANCEL) &&
+ dlm_lock_on_list(&res->granted, lock))
+ status = DLM_CANCELGRANT;
+
/* if the master told us the lock was already granted,
* let the ast handle all of these actions */
if (status == DLM_CANCELGRANT) {
--
1.8.3.1
</pre>
</blockquote>
<pre class="moz-quote-pre" wrap="">.
</pre>
</blockquote>
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