[NFS] [Cluster-devel] [PATCH 0/4 Revised] NLM - lock failover

[Wendy Cheng <wcheng@redhat.com>]

Frank van Maarseveen wrote:

>I'm quite interested in _any_ patch which would allow me to drop
>the locks obtained by NFS clients on a specific export, either by (1)
>"exportfs -uh" or by (2) "echo /some/path > /proc/fs/nfsd/nlm_drop_lock"
>as Neil mentioned.
>  
>
Thanks for commenting on this. Opinions from users who will eventually 
use these interfaces are always valued.

>[snip]
>
>
>I'd prefer (2) "echo /some/path > /proc/fs/nfsd/nlm_drop_lock" because:
>  
>
To convert the first patch of this submitted series from "fsid" to 
"/some/path" is a no-brainer, since we had gone thru several rounds of 
similar changes. However, my questions (it is more of a Neil's question) 
are, if I convert the first patch to do this,

1) then why do we still need the RPC drop-lock call in nfs-util ?
2) what should we do for the 2nd patch ? i.e., how do we communicate 
with the take-over server it is time for its action, by RPC call or by 
"echo /some/path > /proc/fs/nfsd/nlm_set_grace_or_whatever" ?

In general, I feel if we do this "/some/path" approach, we may as well 
simply convert the 2nd patch from "fsid" to "/some/path". Then we would 
finish this long journey.

-- Wendy

>- Tying the -h (drop locks) option to -u (unexport) is too restrictive IMO.
>  For one thing, there's a bug in the linux NFS client locking code (I
>  reported this earlier) which results in locks not being removed from
>  the server. It was not too difficult to reproduce and programs on the
>  client will wait forever due to this. To handle these kind of situations
>  I need (2) on the server.
>
>- (2) may be useful for other NFS server setups: it is inherently more
>  flexible.
>
>- (2) does not depend on nfs-utils. It's simpler.
>
>
>(*) virtual in this case means a UUID or IP based fsid= option and an
>additional IP address on eth0 per export entry, such, that it becomes
>possible to move an export entry + disk partition + local mount to
>different hardware without needing to remount it on all <large number>
>NFS clients.
>
>  
>