Re: clients fail to reclaim locks after server reboot or manual sm-notify

[Bryan Schumaker <bjschuma@netapp.com>]

On 11/16/2011 10:30 AM, J. Bruce Fields wrote:
> On Wed, Nov 16, 2011 at 09:25:01AM -0500, Bryan Schumaker wrote:
>> Here is what I'm doing (On debian with 2.6.32):
>> - (On Client) Mount the server: `sudo mount -o vers=3 
>> 192.168.122.202:/home/bjschuma /mnt`
>> - (On Client) Lock a file using nfs-utils/tools/locktest: `./testlk 
>> /mnt/test`
>> - (On Server) Call sm-notify with the server's IP address: `sudo 
>> sm-notify -f -v 192.168.122.202`
>> - dmesg on the client has this message:
>>     lockd: spurious grace period reject?!
>>     lockd: failed to reclaim lock for pid 2099 (errno -37, status 4)
>> - (In wireshark) The client sends a lock request with the "Reclaim" bit 
>> set to "yes" but the server replies with "NLM_DENIED_GRACE_PERIOD".
> 
> That sounds like correct server behavior to me.
> 
> Once the server ends the grace period and starts accepting regular
> non-reclaim locks, there's the chance of a situation like:
> 
> 	client A		client B
> 	--------		--------
> 
> 	acquires lock
> 
> 		---server reboot---
> 		---grace period ends---
> 
> 				acquires conflicting lock
> 				drops conflicting lock
> 
> And if the server permits a reclaim of the original lock from client A,
> then it gives client A the impression that it has held its lock
> continuously over this whole time, when in fact someone else has held a
> conflicting lock.
> 
> So: no non-reclaim locks are allowed outside the grace period.

I see where I was confused.  I thought that running sm-notify also restarted the grace period.

- Bryan

> 
> If you restart the server, and *then* immediately run sm-notify while
> the new nfsd is still in its grace period, I'd expect the reclaim to
> succeed.
> 
> And that may be where the HA setup isn't right--if you're doing
> active/passive failover, then you need to make sure you don't start nfsd
> on the backup machine until just before you send the sm-notify.
> 
> --b.
> 
>>
>> Shouldn't the server be allowing the lock reclaim?  When I tried 
>> yesterday using 3.0 it only triggered DNS packets, I tried again a few 
>> minutes ago and got the same results that I did using .32.