[Lustre-devel] Thinking of Hacks around bug #12329

[Oleg Drokin]

Hello!

On May 14, 2009, at 10:25 AM, Oleg Drokin wrote:

> Actually just to combat situqtion like this MGCs are doing a bit of a
> pause
> for a few seconds before refetching config, I remember there was a bug
> and this measure was introduced as a fix.

Nic actually tuned in and said that the backoff (set at 3 seconds now)
is certainly not enough, since it takes this long to only mount actual
on-disk fs.
Anyway that got me thinking that we have a "coarse-grained" locking  
problem.
Since OSTs don't connect to other OSTs, they do not care about OT  
connections,
and perhaps if we introduce bit-locks to MGS locks as well to indicate  
client
type, then locks from OSTs would only be revoked when MDS connects or  
disconnects,
MDS locks would only be revoked when OSTs connect or disconnect and  
client locks
would be revoked always.
Or alternatively we can split our single resource right now to a few  
separate:
one for osts one for MDSes for example, sure that would mean clients  
would not have to
take two locks, but on the other hand there would be supposedly less  
information to
reparse when one of those locks is invalidated.

Nathan, what do you think?

Bye,
     Oleg