[Ocfs2-users] ping_pong using o2cb and cman

[Sunil Mushran]

fcntl() locking does not pair at all with dlm locking. So both ocfs2 and gfs2
use a special scheme just for this lock. Both use the ordered messaging
provided by the corosync cluster engine. This lock is fully synchronised and
thus is not as performant as it can be. (Both cman and pacemaker use cce.)

But that's ok because fcntl()'s locking semantics is not what you think it is.
The lock is almost useless in this day and age. The only use is supporting
legacy apps. For more refer to Jeremy Allison's overview of this user lock.
http://www.samba.org/samba/news/articles/low_point/tale_two_stds_os2.html

Given that and considering most apps allow users to choose between fcntl()
and flock(), we've decided for now to just support the latter with o2cb.

flock() pairs well with dlm locking.

On 01/18/2011 10:22 AM, Dan Warner wrote:
> OK thanks for the clarification.
>
> Is the support of fcntl() locking within o2cb, on the wishlist of features to be implemented at a future date? Is it even a priority to do?
>
> Thanks, Dan
>
> On 18 January 2011 18:00, Sunil Mushran <sunil.mushran at oracle.com <mailto:sunil.mushran at oracle.com>> wrote:
>
>     ping_long tests the fcntl() user locks.
>
>     ocfs2 supports clustered fcntl() locking with cman and pacemaker
>     cluster stacks. Not with o2cb.
>
>     ocfs2 supports clustered flock() with all stacks. o2cb, cman and pacemaker.
>
>
>
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