[Linux-cluster] Re: [NFS] [RFC] NLM lock failover admin interface

[Wendy Cheng]

Hi,

KABI (kernel application binary interface) commitment is a big thing
from our end - so I would like to focus more on the interface agreement
before jumping into coding and implementation details. 

>   One is the multiple-lockd-threads idea.

Assume we still have this on the table.... Could I expect the admin
interface goes thru rpc.lockd command (man page and nfs-util code
changes) ? The modified command will take similar options as rpc.statd;
more specifically, the -n, -o, and -p (see "man rpc.statd"). To pass the
individual IP (socket address) to kernel, we'll need nfsctl with struct
nfsctl_svc modified.

For the kernel piece, since we're there anyway, could we have the
individual lockd IP interface passed to SM (statd) (in SM_MON call) ?
This would allow statd to structure its SM files based on each lockd IP
address, an important part of lock recovery.

>   One is to register a callback when an interface is shut down.

Haven't checked out (linux) socket interface yet. I'm very fuzzy how
this can be done. Anyone has good ideas ? 

>   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   no longer valid local addresses".

Very appealing - but the devil's always in the details. How to decide
which IP address is no longer valid ? Or how does lockd know about these
IP addresses ? And how to associate one particular IP address with the
"struct nlm_file" entries within nlm_files list ? Need few more days to
sort this out (or any one already has ideas in mind ?).

-- Wendy