On Mon, Nov 10, 2008 at 08:41:38AM -0500, Steve Dickson wrote: > J. Bruce Fields wrote: > > On Wed, Oct 29, 2008 at 04:30:32PM -0400, Chuck Lever wrote: > >> I assume sync() is required because this logic performs a rename as well > >> as a simple write? > > > > I think an fsync() on the containing directory (together with an fsync() > > of the file itself) would do the job if you wanted to avoid the globaly > > sync(). I don't think ext3 is capable of doing anything finer-grained > > than a whole-filesystem sync, though, so this doesn't help many people > > in practice right now. > > > > In any case, the rename adds an extra level of safety by ensuring the > > nsm state is updated atomically, so we shouldn't get rid of it. > > > >>> Anyway, I think the nsm state updating shouldn't matter if you don't > >>> even have any peers to notify. > >> It probably does matter. > >> > >> When a system is initially installed, it likely does not have a state > >> file in /var/lib/nfs. This may be harmless if it's not present; > >> rpc.statd probably does the right thing in this case. > > > > The "right thing" in that case would be, I guess, to create a state file > > with "0" in it. It doesn't do that. So this patch *does* break stuff. > > Oops! > > > > So should we revert it and do something else, or patch statd to create > > a new state file if necessary? > I have to agree with Chuck, that managing the state file from one > place is desirable... Although does it make sense to move that management > into a init script? Maybe insuring the state is different before any > daemons are started? Would we still need the sync()? > > > > >> However, the rest of the logic in nsm_get_state() is needed to bump the > >> system's state value properly after every reboot. It may be > >> inconsequential if there were no mounts or no NFS clients during the > >> last reboot, but this is subtle. I wouldn't bet on it. > > > > If the state is only every communicated to hosts by notifications, then > > if we're not notifying, the update of the state can't matter. > I had the same notion... If there are no clients to notify, why would > any clients care if our state changed?? With that said.... I do have a > sinking feeling that this patch will come back to bite us... > It was just too easy of a fix... :-) Any progress on this? I don't think we can release in the current state, since as far as I can tell that means on a new system, unless the install scripts create /var/lib/nfs/state, neither sm-notify nor statd ever writes to /proc/sys/fs/nfs/nsm_local_state, and (without testing) it looks to me like that means lockd defaults to a state of 0, which is nonsense? One possible compromise that I think would be correct might be to skip the sync in the case where there are no peers to notify, instead of exiting early in that case. As long as a sync happens at some point before we grant any locks (which statd can guarantee), I think that will work.... --b. -- 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
