[Ocfs2-devel] [PATCH 1/2] ocfs2 fix o2dlm dlm run purgelist

[Srinivas Eeda]

Sunil,

as of now, there is still a window in dlm_get_lock_resource, where it 
finds the lockres but it doesn't protect it from getting purged. Second 
patch fixes this by marking it in_use, can you please review that one as 
well.

Thanks,
--Srini

On 6/17/2010 8:06 AM, Sunil Mushran wrote:
> On 06/15/2010 11:06 PM, Wengang Wang wrote:
>> still the question.
>> If you have sent DEREF request to the master, and the lockres became 
>> in-use
>> again, then the lockres remains in the hash table and also in the 
>> purge list.
>> So
>> 1) If this node is the last ref, there is a possibility that the master
>> purged the lockres after receiving DEREF request from this node. In this
>> case, when this node does dlmlock_remote(), the lockres won't be 
>> found on the
>> master. How to deal with it?
>>
>> 2) The lockres on this node is going to be purged again, it means it 
>> will send
>> secondary DEREFs to the master. This is not good I think.
>>
>> A thought is setting lockres->owner to DLM_LOCK_RES_OWNER_UNKNOWN after
>> sending a DEREF request againt this lockres. Also redo master reqeust
>> before locking on it.
>>    
>
> The fix we are working towards is to ensure that we set
> DLM_LOCK_RES_DROPPING_REF once we are determined
> to purge the lockres. As in, we should not let go of the spinlock
> before we have either set the flag or decided against purging
> that resource.
>
> Once the flag is set, new users looking up the resource via
> dlm_get_lock_resource() will notice the flag and will then wait
> for that flag to be cleared before looking up the lockres hash
> again. If all goes well, the lockres will not be found (because it
> has since been unhashed) and it will be forced to go thru the
> full mastery process.