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

[Tao Ma]

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?

Regards,
Tao