On Tue, 2016-08-02 at 16:38 -0400, J. Bruce Fields wrote: > On Tue, Aug 02, 2016 at 02:15:27PM -0400, Jeff Layton wrote: > > > > A small set of patches that should add CB_NOTIFY_LOCK support for knfsd. > > The basic idea is to use FL_SLEEP to set blocks when a lock is contended, > > and then queue a callback to issue a CB_NOTIFY_LOCK in the lm_notify op. > > > > Per the RFC, we take no steps to reserve the lock for the client. This is > > a simple notification to tell the client that it may want to poll for it > > again. > > > > It also takes steps to clean out old, abandoned blocks when the client > > loses interest in obtaining the lock. > > I had to double-check the spec language here: ok, 5661 9.6 does > explicitly say that clients can't depend on the notify, so they do need > to continue polling--so that cleanup doesn't risk leaving clients > blocking indefinitely. Might be worth a comment referencing that > language. > Yep, exactly. This is 100% a best-effort kind of thing. The clients have to poll regardless of whether we send a notification. > > Looks like you're not attempting any sort of fair queueing, so clients > that get a notify just race for the lock? That's fine. > Yep. I don't think that we can reasonably do anything more sophisticated. Hopefully the delay between callbacks will be enough to prevent the herd from thundering too badly. > > Thanks for looking at this! > > --b. > No problem. It has been on my to-do list for a while now... > > > > > > Only lightly tested so far, but it seems to do the right thing. > > The client-side piece is the next step. > > > > Jeff Layton (4): > > nfsd: plumb in a CB_NOTIFY_LOCK operation > > nfsd: have nfsd4_lock use blocking locks for v4.1+ locks > > nfsd: add a LRU list for blocked locks > > nfsd: set the MAY_NOTIFY_LOCK flag in OPEN replies > > > > fs/nfsd/netns.h | 1 + > > fs/nfsd/nfs4callback.c | 57 +++++++++++++ > > fs/nfsd/nfs4state.c | 209 ++++++++++++++++++++++++++++++++++++++++++---- > > fs/nfsd/state.h | 21 ++++- > > fs/nfsd/xdr4cb.h | 9 ++ > > include/uapi/linux/nfs4.h | 5 +- > > 6 files changed, 281 insertions(+), 21 deletions(-) > > > > -- > > 2.7.4 -- 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
