[Ocfs2-devel] [PATCH 1/1] Ocfs2: Add a mount option "coherency=*" to handle cluster coherency for O_DIRECT writes.

[Tao Ma]

Tao Ma wrote:
> Hi Joel,
> Joel Becker wrote:
>   
>> On Mon, Oct 11, 2010 at 04:46:39PM +0800, Tristan Ye wrote:
>>   
>>     
>>> Currently, default behavior of O_DIRECT writes was allowing
>>> concurrent writing among nodes, no cluster coherency guaranteed
>>> (no EX locks was taken), it hurts buffered reads on other nodes
>>> by reading stale data from cache.
>>>
>>> The new mount option introduce a chance to choose two different
>>> behaviors for O_DIRECT writes:
>>>
>>>     * coherency=full, as the default value, will disallow
>>>                       concurrent O_DIRECT writes by taking
>>>                       EX locks.
>>>
>>>     * coherency=buffered, allow concurrent O_DIRECT writes
>>>                           without EX lock among nodes, which
>>>                           gains high performance at risk of
>>>                           getting stale data on other nodes.
>>>
>>> Signed-off-by: Tristan Ye <tristan.ye at oracle.com>
>>>     
>>>       
>> 	This patch is now in the merge-window branch of ocfs2.git.
>>   
>>     
> I think that you agree with me that we only need to take PR lock in 
> full_coherency, but this patch
> still try the exclusive one. So do I miss something?
>   
Oh, my mistake. I read the words wrongly. Sorry for the noise.

Regards,
Tao