On Fri, 2018-06-01 at 10:17 -0400, J. Bruce Fields wrote: > On Fri, Jun 01, 2018 at 06:42:37AM -0400, Jeff Layton wrote: > > Thanks for having a look. Hmm...you're right. > > > > nn->nfsd4_lease = 90; /* default lease time */ > > nn->nfsd4_grace = 90; > > > > nit: We should probably add a #define'd constant for that at some > > point...but, might this be problematic? > > > > In the pessimal case, you might renew your lease just before the server > > crashes. It then comes back up quickly and starts the grace period. By > > the time the client contacts the server again the grace period is almost > > over and you may have very little time to actually do any reclaim. > > > > ISTR that when we were working on the server at PD we had determined > > that we needed around 2 grace periods + a small fudge factor. I don't > > recall the details of how we determined it though. > > OK, I'd be interested in any of that. > > If we decide we need a larger grace/lease ratio, we may want to adjust > default lease down at same time to avoid increasing grace period, as > that's always an annoyance. > I think we just figured that we ought to give the client a full lease period to reclaim everything, in case it holds a lot of state. You also need to give it a full lease period to figure out that the server has rebooted, and then I think we added a few seconds to account for "other factors" (transport delays and whatnot). > > Even worse: > > > > $ cat /proc/sys/fs/lease-break-time > > 45 > > > > Maybe we should be basing the v4 lease time on the lease-break-time > > value? It seems like we ought to revoke delegations after two lease > > periods rather than after half of one. > > No, we ignore lease-break-time on delegations. See the comment in > fs/nfsd/nfs4state.c:nfsd_break_deleg_cb(): > > /* > * We don't want the locks code to timeout the lease for us; > * we'll remove it ourself if a delegation isn't returned > * in time: > */ > fl->fl_break_time = 0; > Ahh thanks, I had forgotten that. Whew! -- Jeff Layton <jlayton@xxxxxxxxxx> -- 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
