2011/11/16 Bryan Schumaker <bjschuma@xxxxxxxxxx>: > On 11/16/2011 03:08 PM, J. Bruce Fields wrote: >> On Wed, Nov 16, 2011 at 09:09:07PM +0200, Pavel A wrote: >>> I've read about this issue here: >>> http://www.time-travellers.org/shane/papers/NFS_considered_harmful.html >>> >>> /*----- >>> In the event of server failure (e.g. server reboot or lock daemon >>> restart), all client locks are lost. However, the clients are not >>> informed of this, and because the other operations (read, write, and >>> so on) are not visibly interrupted, they have no reliable way to >>> prevent other clients from obtaining a lock on a file they think they >>> have locked. >>> -----*/ >> >> That's incorrect. Perhaps the article is out of date, I don't know. > > Looks like it was written about 11 years ago, so I'll believe that it's out of date. Yes, should have watched out for that. > > - Bryan > >> >>> Can't get this. If there is a grace period after reboot and clients >>> can successfully reclaim locks, then how other clients can obtain >>> locks? >> >> That's right, in the absence of bugs, if a client succesfully reclaims a >> lock, then it knows that no other client can have acquired that lock in >> the interim: since the reclaim succeeded, that means the server is still >> in the grace period, which means the only other locks that it has >> allowed are also reclaims. If some reclaim conflicts with this lock, >> then the other client must have reclaimed a lock that it didn't actually >> hold before (hence must be buggy). >> >>>> You need to restart nfsd on the node that is taking over. That means >>>> that clients usings both filesystems (A and B) will have to do lock >>>> recovery, when in theory only those using volume B should have to, and >>>> that is suboptimal. But it is also correct. >>>> >>> >>> Seems to work. As of a more optimal solution: what do you think of the >>> contents of /proc/locks? May it be possible to use this info to then >>> perform locking locally on the other node (after failover)? >> >> No, I don't think so. And I'd be careful about using /proc/locks for >> anything but debugging. >> >> --b. > > Well, looks like this is it. Thank you very much, Bruce, Bryan - you real helped me to keep this going :) -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
