[Cluster-devel] [GFS2 PATCH 1/2] GFS2: Introduce EXSH (exclusively shared on one node)

[Bob Peterson <rpeterso@redhat.com>]

----- Original Message -----
> Hi,
> 
> 
> On 18/04/18 17:58, Bob Peterson wrote:
> > This patch is a first step in rgrp sharing. It allows for a new
> > type of glock mode called EXSH, which stands for a lock that is
> > Exclusive to one node, but shared amongst processes on that node.
> > Like a Shared glock, multiple processes may acquire the lock in
> > EXSH mode at the same time, provided they're all on the same
> > node. All other nodes will see this as an EX lock. In other words,
> > to the DLM, the lock is granted to the node in EX, but at the
> > glock layer, they may be shared.
> >
> > For now, there are no users of the new EXSH glock mode.
> > Future patches will use it to improve performance with rgrp sharing.
> Is there a reason why we cannot just add a lock flag here, rather than
> requiring a new lock state? That should make it a much smaller change,
> and leaves the lock state always reflecting the cluster lock state,
> 
> Steve.

Hi,

Well, yes, we can add a new lock flag. The new locking mode just
gave me more clarity how I thought about things. A flag ought to
work just as well.

I was also trying to extrapolate how we can use this in the future
for other types of local lock sharing, but we can also do that
with the same flag.

Also, I had originally coded it so it did everything through glops,
but I decided it was just too confusing to follow.

Regards,

Bob Peterson
Red Hat File Systems