On Fri, 26 Sep 2014 14:39:49 -0400
"J. Bruce Fields" <bfields@xxxxxxxxxxxx> wrote:
> By the way, I've seen the following *before* your patches, but in case
> you're still looking at reboot recovery problems:
>
> I'm getting sporadic failures in the REBT6 pynfs test--a reclaim open
> succeeds after a previous boot (with full grace period) during which the
> client had failed to reclaim.
>
> I managed to catch one trace, the relevant parts looked like:
>
> SETCLIENTID client1
> OPEN
> LOCK
>
> (server restart here)
>
> SETCLIENTID client2
> OPEN
> LOCK (lock that conflicts with client1's)
>
> (server restart here)
>
> SETCLIENTID client1
> OPEN CLAIM_PREVIOUS
>
> And all those ops (including the last reclaim open) succeeded.
>
> So I didn't have a chance to review it more carefully, but it certainly
> looks like a server bug, not a test bug. (Well, technically the server
> behavior above is correct since it's not required to refuse anything
> till we actually attempt to reclaim the original lock, but we know our
> server's not that smart.)
>
> But I haven't gotten any further than that....
>
> --b.
>
Ewww...v4.0... ;)
Well, I guess that could happen if, after the first reboot, client1 also
did a SETCLIENTID *and* reclaimed something that didn't conflict with
the lock that client2 grabs...or, did an OPEN/OPEN_CONFIRM after the
grace period without reclaiming its lock previously.
If it didn't do one or the other, then its record should have been
cleaned out of the DB after the grace period ended between the reboots
and it wouldn't have been able to reclaim after the second reboot.
It's a bit of a pathological case, and I don't see a way to fix that in
the context of v4.0. The fact that there's no RECLAIM_COMPLETE is a
pretty nasty protocol bug, IMO. Yet another reason to start really
moving people toward v4.1+...
> On Tue, Aug 19, 2014 at 02:38:24PM -0400, Jeff Layton wrote:
> > v2:
> > - move grace period handling into its own module
> >
> > One of the huge annoyances in dealing with knfsd is the 90s grace period
> > that's imposed when the server reboots. This is not just an annoyance,
> > but means a siginificant amount of "downtime" in many production
> > environments.
> >
> > This patchset aimed at reducing this pain. It adds a couple of /proc
> > knobs that tell the lockd and nfsd lock managers to lift the grace
> > period.
> >
> > It also changes the UMH upcalls to pass a little bit of extra info in
> > the form of environment variables so that the upcall program can
> > determine whether there are still any clients that may be in the process
> > of reclaiming.
> >
> > There are also a couple of cleanup patches in here that are not strictly
> > required. In particular, making a separate grace.ko module doesn't have
> > to be done, but I think it's a good idea.
> >
> > Jeff Layton (5):
> > lockd: move lockd's grace period handling into its own module
> > lockd: add a /proc/fs/lockd/nlm_end_grace file
> > nfsd: add a v4_end_grace file to /proc/fs/nfsd
> > nfsd: remove redundant boot_time parm from grace_done client tracking
> > op
> > nfsd: pass extra info in env vars to upcalls to allow for early grace
> > period end
> >
> > fs/Kconfig | 6 ++-
> > fs/lockd/Makefile | 3 +-
> > fs/lockd/netns.h | 1 -
> > fs/lockd/procfs.c | 76 +++++++++++++++++++++++++++
> > fs/lockd/procfs.h | 28 ++++++++++
> > fs/lockd/svc.c | 10 +++-
> > fs/nfs_common/Makefile | 3 +-
> > fs/{lockd => nfs_common}/grace.c | 68 +++++++++++++++++++++----
> > fs/nfsd/Kconfig | 1 +
> > fs/nfsd/nfs4recover.c | 107 +++++++++++++++++++++++++++++++--------
> > fs/nfsd/nfs4state.c | 8 +--
> > fs/nfsd/nfsctl.c | 35 +++++++++++++
> > fs/nfsd/state.h | 5 +-
> > include/linux/proc_fs.h | 2 +
> > 14 files changed, 312 insertions(+), 41 deletions(-)
> > create mode 100644 fs/lockd/procfs.c
> > create mode 100644 fs/lockd/procfs.h
> > rename fs/{lockd => nfs_common}/grace.c (50%)
> >
> > --
> > 1.9.3
> >
--
Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
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