[Ocfs2-devel] [PATCH] ocfs2/dlm: move lock to the tail of grant queue while doing in-place convert

[xuejiufei]

Hi Eric,

On 2016/1/29 16:25, Eric Ren wrote:
> Hello jiufei,
> 
> On Wed, Jan 27, 2016 at 05:52:05PM +0800, xuejiufei wrote: 
>> We have found a bug when two nodes doing umount one after another.
>> 1) Node 1 migrate a lockres that has 3 locks in grant queue such as
>> N2(PR)<->N3(NL)<->N4(PR) to N2. After migration, lvb of the lock N3(NL)
>> and N4(PR) are empty on node 2 because migration target do not copy lvb
>> to these two lock.
>> 2) Node 3 want to convert to PR, it can be granted in
>> __dlmconvert_master(), and the order of these locks is unchanged. The
>> lvb of the lock N3(PR) on node 2 is copyed from lockres in function
>> dlm_update_lvb() while the lvb of lock N4(PR) is still empty.
>> 3) Node 2 want to leave domain, it will migrate this lockres to node 3.
>> Then node 2 will trigger the BUG in dlm_prepare_lvb_for_migration()
>> when adding the lock N4(PR) to mres with the following message because
>> the lvb of mres is already copied from lock N3(PR), but the lvb of lock
>> N4(PR) is empty.
>>
>> "Mismatched lvb in lock cookie=%u:%llu, name=%.*s, node=%u"
>>
>> Signed-off-by: xuejiufei <xuejiufei at huawei.com>
>> ---
>>  fs/ocfs2/dlm/dlmconvert.c | 6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/fs/ocfs2/dlm/dlmconvert.c b/fs/ocfs2/dlm/dlmconvert.c
>> index e36d63f..ae0c9d1 100644
>> --- a/fs/ocfs2/dlm/dlmconvert.c
>> +++ b/fs/ocfs2/dlm/dlmconvert.c
>> @@ -212,6 +212,12 @@ grant:
>>  	if (lock->lksb->flags & DLM_LKSB_PUT_LVB)
>>  		memcpy(res->lvb, lock->lksb->lvb, DLM_LVB_LEN);
>>
>> +	/*
>> +	 * move the lock to tail because it may be the only lock who has
>> +	 * a invalid lvb.
>> +	 */
> 
> I'm not fimiliar with ocfs2/dlm yet, just out of curious, by "invalid lvb"
> here it means when a lock has been upconvert in place, its lvb is invalid?
> If so, why not reset it than move?
> 
"invalid lvb" means that the lvb can not be trusted. After migration, lvb in
all locks on master are invalid because the locks are new created. The lock
been upconverted is valid after copy from lock resource on master.

Thanks,
Jiufei

> Thanks,
> Eric
>> +	list_move_tail(&lock->list, &res->granted);
>> +
>>  	status = DLM_NORMAL;
>>  	*call_ast = 1;
>>  	goto unlock_exit;
>> -- 
>> 1.8.4.3
>>
>>
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>>
> 
> .
>