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Date:      Wed, 29 Jul 2015 11:33:29 +0200
From:      Ahmed Kamal <email.ahmedkamal@googlemail.com>
To:        Rick Macklem <rmacklem@uoguelph.ca>
Cc:        Graham Allan <allan@physics.umn.edu>,  Ahmed Kamal via freebsd-fs <freebsd-fs@freebsd.org>
Subject:   Re: Linux NFSv4 clients are getting (bad sequence-id error!)
Message-ID:  <CANzjMX7J7wm4f8nCXqjGe7F%2BZgwYFBtFtKTFOzrPJN-MeXJ5EA@mail.gmail.com>
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hmm, if I understand you correctly, this time_seconds value is the number
of seconds till the box booted ? If so, I guess this is not really the
cause of what we're seeing as the box is only up for 8 days

bsd# uptime
11:28AM  up 8 days,  6:20, 6 users, load averages: 0.94, 0.91, 0.84

The NFS client box's uptime is
linux# uptime
 11:31:39 up 8 days,  5:51, 11 users,  load average: 87.74, 87.43, 87.35

and yes the huge load is most likely due to this NFS bug

On Wed, Jul 29, 2015 at 1:39 AM, Rick Macklem <rmacklem@uoguelph.ca> wrote:

> Ahmed Kamal wrote:
> > Hi again Rick,
> >
> > Seems that I'm still being unlucky with nfs :/ I caught one of the newly
> > installed RHEL6 boxes having high CPU usage, and bombarding the BSD NFS
> box
> > with 10Mbps traffic .. I caught a tcpdump as you mentioned .. You can
> > download it here:
> >
> >
> https://dl.dropboxusercontent.com/u/51939288/nfs41-high-client-cpu.pcap.bz2
> >
> Ok, the packet trace suggests that the NFSv4 server is broken (it is
> replying
> with NFS4ERR_STALE_CLIENTID for a recently generated ClientID).
> Now, I can't be sure, but the only explanation I can come up with is...
> - For some arches (I only have i386, so I wouldn't have seen this during
> testing),
>   time_t is 64bits (uint64_t).
>   --> If time_seconds somehow doesn't fit in the low order 32bits, then
> the code
>       would be busted for these arches because nfsrvboottime is set to
> time_seconds
>       when the server is started and then there are comparisons like:
>       if (nfsrvboottime != clientid.lval[0])
>            return (NFSERR_STALECLIENTID);
>        /* where clientid.lval[0] is a uint32_t */
> Anyhow, if this is what is happening, the attached simple patch should fix
> it.
> (I don't know how time_seconds would exceed 4billion, but the clock code is
>  pretty convoluted, so I can't say if it can possibly happen?)
>
> rick
> ps: Hmm, on i386 time_seconds ends up at 1438126486, so maybe it can exceed
>     4*1024*1024*1024 - 1 on amd64?
>
> > I didn't restart the client yet .. so if you catch me in the next few
> hours
> > and want me to run any diagnostics, let me know. Thanks a lot all for
> > helping
> >
> > On Thu, Jul 23, 2015 at 11:59 PM, Rick Macklem <rmacklem@uoguelph.ca>
> wrote:
> >
> > > Ahmed Kamal wrote:
> > > > Can you please let me know the ultimate packet trace command I'd
> need to
> > > > run in case of any nfs4 troubles .. I guess this should be
> comprehensive
> > > > even at the expense of a larger output size (which we can trim
> later)..
> > > > Thanks a lot for the help!
> > > >
> > > tcpdump -s 0 -w <file>.pcap host <client-host-name>
> > > (<file> refers to a file name you choose and <client-host-name> refers
> to
> > >  the host name of a client generating traffic.)
> > > --> But you won't be able to allow this to run for long during the
> storm
> > > or the
> > >     file will be huge.
> > >
> > > Then you look at <file>.pcap in wireshark, which knows NFS.
> > >
> > > rick
> > >
> > > > On Thu, Jul 23, 2015 at 11:53 PM, Rick Macklem <rmacklem@uoguelph.ca
> >
> > > wrote:
> > > >
> > > > > Graham Allan wrote:
> > > > > > For our part, the user whose code triggered the pathological
> > > behaviour
> > > > > > on SL5 reran it on SL6 without incident - I still see lots of
> > > > > > sequence-id errors in the logs, but nothing bad happened.
> > > > > >
> > > > > > I'd still like to ask them to rerun again on SL5 to see if the
> > > "accept
> > > > > > skipped seqid" patch had any effect, though I think we expect
> not.
> > > Maybe
> > > > > > it would be nice if I could get set up to capture rolling
> tcpdumps of
> > > > > > the nfs traffic before they run that though...
> > > > > >
> > > > > > Graham
> > > > > >
> > > > > > On 7/20/2015 10:26 PM, Ahmed Kamal wrote:
> > > > > > > Hi folks,
> > > > > > >
> > > > > > > I've upgraded a test client to rhel6 today, and I'll keep an
> eye
> > > on it
> > > > > > > to see what happens.
> > > > > > >
> > > > > > > During the process, I made the (I guess mistake) of zfs send |
> > > recv to
> > > > > a
> > > > > > > locally attached usb disk for backup purposes .. long story
> short,
> > > > > > > sharenfs property on the received filesystem was causing some
> > > > > nfs/mountd
> > > > > > > errors in logs .. I wasn't too happy with what I got .. I
> > > destroyed the
> > > > > > > backup datasets and the whole pool eventually .. and then
> rebooted
> > > the
> > > > > > > whole nas box .. After reboot my logs are still flooded with
> > > > > > >
> > > > > > > Jul 21 05:12:36 nas kernel: nfsrv_cache_session: no session
> > > > > > > Jul 21 05:13:07 nas last message repeated 7536 times
> > > > > > > Jul 21 05:15:08 nas last message repeated 29664 times
> > > > > > >
> > > > > > > Not sure what that means .. or how it can be stopped .. Anyway,
> > > will
> > > > > > > keep you posted on progress.
> > > > > >
> > > > > Oh, I didn't see the part about "reboot" before. Unfortunately, it
> > > sounds
> > > > > like the
> > > > > client isn't recovering after the session is lost. When the server
> > > > > reboots, the
> > > > > client(s) will get NFS4ERR_BAD_SESSION errors back because the
> server
> > > > > reboot has
> > > > > deleted all sessions. The NFS4ERR_BAD_SESSION should trigger state
> > > > > recovery on the client.
> > > > > (It doesn't sound like the clients went into recovery, starting
> with a
> > > > > Create_session
> > > > >  operation, but without a packet trace, I can't be sure?)
> > > > >
> > > > > rick
> > > > >
> > > > > >
> > > > > > --
> > > > > >
> > >
> -------------------------------------------------------------------------
> > > > > > Graham Allan - gta@umn.edu - allan@physics.umn.edu
> > > > > > School of Physics and Astronomy - University of Minnesota
> > > > > >
> > >
> -------------------------------------------------------------------------
> > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>



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