[Linux-cluster] Re: [NFS] [RFC] NLM lock failover admin interface
Wendy Cheng
wcheng at redhat.com
Tue Jun 13 07:00:11 UTC 2006
On Tue, 2006-06-13 at 13:17 +1000, Neil Brown wrote:
> So:
> I think if we really want to "remove all NFS locks on a filesystem",
> we could probably tie it into umount - maybe have lockd register some
> callback which gets called just before s_op->umount_begin.
The "umount_begin" idea was one time on my list but got discarded. The
thought was that nfsd was not a filesystem, neither was lockd. How to
register something with VFS umount for non-filesystem kernel modules ?
Invent another autofs-like pseudo filesystem ? Mostly, not every
filesystem would like to get un-mounted upon failover (GFS, for example,
does not get un-mounted by our cluster suite upon failover).
> If we want to remove all locks that arrived on a particular
> interface, then we should arrange to do exactly that. There are a
> number of different options here.
> One is the multiple-lockd-threads idea.
Certainly a good option. To make it happen, we still need admin
interface. How to pass IP address from user mode into kernel - care to
give this some suggestions if you have them handy ? Should socket ports
get dynamics assigned ? Will we have scalibility issues ?
> One is to register a callback when an interface is shut down.
> Another (possibly the best) is to arrange a new signal for lockd
> which say "Drop any locks which were sent to IP addresses that are
> no longer valid local addresses".
These, again, give individual filesystem no freedom to adjust what they
need upon failover. But I'll check them out this week - maybe there are
good socket layer hooks that I overlook.
>
> So those are my thoughts. Do any of them seem reasonable to you?
>
The comments are greatly appreciated. And hopefully we can reach
agreement soon.
-- Wendy
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