Date: Wed, 8 Jul 2015 19:30:47 -0400 (EDT) From: Rick Macklem <rmacklem@uoguelph.ca> To: Ahmed Kamal <email.ahmedkamal@googlemail.com> Cc: Julian Elischer <julian@freebsd.org>, freebsd-fs@freebsd.org, Xin LI <d@delphij.net> Subject: Re: Linux NFSv4 clients are getting (bad sequence-id error!) Message-ID: <502673468.6406432.1436398247559.JavaMail.zimbra@uoguelph.ca> In-Reply-To: <CANzjMX4MzqtBD-myifpT6i_HM97FVQ31vWjh7fiMsLJBe7Bh0w@mail.gmail.com> References: <CANzjMX45QaC8yZx2nHPAohJRvQjmUOHuhMQWP9nX%2BsrJs707Hg@mail.gmail.com> <791936587.3443190.1435873993955.JavaMail.zimbra@uoguelph.ca> <CANzjMX427XNQJ1o6Wh2CVy1LF1ivspGcfNeRCmv%2BOyApK2UhJg@mail.gmail.com> <CANzjMX5xyUz6OkMKS4O-MrV2w58YT9ricOPLJWVtAR5Ci-LMew@mail.gmail.com> <2010996878.3611963.1435884702063.JavaMail.zimbra@uoguelph.ca> <CANzjMX6EoPOcY9V5EQeu5KO1WhwFxxo7-mYRhccVvKiaDW8nGQ@mail.gmail.com> <1463698530.4486572.1436135333962.JavaMail.zimbra@uoguelph.ca> <CANzjMX4MzqtBD-myifpT6i_HM97FVQ31vWjh7fiMsLJBe7Bh0w@mail.gmail.com>
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Ahmed Kamal wrotes:
> Hi folks,
>
> I have tested Xin's patches .. Unfortunately the problem didn't go away :/
> Many users are still reporting hung processes. If it would help, can you
> show me how to dump a network trace that would help you identify the issue ?
>
Oops, I didn't see this. Ignore my comment w.r.t. testing it in the other post.
rick
> Also, is it possible in any way to have my trusted nfs3, handle the case
> where every zfs /home folder is its own dataset ?
>
These would all need to be separate mounts. If the # of mounts is very large,
maybe using an automounter would be helpful?
(As far as I know, there is no limit to the # of mounts, so I don't see why
you can't just mount them all.)
rick
> On Mon, Jul 6, 2015 at 12:28 AM, Rick Macklem <rmacklem@uoguelph.ca> wrote:
>
> > Ahmed Kamal wrote:
> > > Hi folks,
> > >
> > > Just a quick update. I did not test Xin's patches yet .. What I did so
> > far
> > > is to increase the tcp highwater tunable and increase nfsd threads to 60.
> > > Today (a working day) I noticed I only got one bad sequence error
> > message!
> > > Check this:
> > >
> > > # grep 'bad sequence' messages* | awk '{print $1 $2}' | uniq -c
> > > 1 messages:Jul5
> > > 39 messages.1:Jun28
> > > 15 messages.1:Jun29
> > > 4 messages.1:Jun30
> > > 9 messages.1:Jul1
> > > 23 messages.1:Jul2
> > > 1 messages.1:Jul4
> > > 1 messages.2:Jun28
> > >
> > > So there seems to be an improvement! Not sure if the Linux nfs4 client is
> > > able to somehow recover from those bad-sequence situations or not .. I
> > did
> > > get some user complaints that running "ls -l" is sometimes slow and
> > takes a
> > > couple of seconds to finish.
> > >
> > > One final question .. Do you folks think nfs4.1 is more reliable in
> > general
> > > than nfs4 .. I've always only used nfs3 (I guess it can't work here with
> > > /home/* being separate zfs filesystems) .. So should I go through the
> > pain
> > > of upgrading a few servers to RHEL-6 to try out nfs4.1 ? Basically do you
> > > expect the protocol to be more solid ? I know it's a fluffy question,
> > just
> > > give me your thoughts. Thanks a lot!
> > >
> > All I can say is that the "bad seqid" errors should not occur, since
> > NFSv4.1
> > doesn't use the seqid#s to order RPCs.
> >
> > Also I would say that a correctly implemented NFSv4.1 protocol should
> > function
> > "more correctly" since all RPCs and performed "exactly once". (How much
> > effect
> > this will have in practice, I can't say.)
> >
> > On the other hand, NFSv4.1 is a newer protocol (with an RFC of over
> > 500pages),
> > so it is hard to say how mature the implementations are.
> > I think only testing will give you the answer.
> >
> > I would suggest that you test Xi Lin's patch that allows the "seqid + 2"
> > case
> > and see if that makes the "bad seqid" errors go away. (Even though I think
> > this
> > would indicate a client bug, adding this in way that it can be enabled via
> > a sysctl
> > seems reasonable.)
> >
> > Btw, I haven't seen any additional posts from nfsv4@ietf.org on this, rick
> >
> > >
> > >
> > > On Fri, Jul 3, 2015 at 2:51 AM, Rick Macklem <rmacklem@uoguelph.ca>
> > wrote:
> > >
> > > > Ahmed Kamal wrote:
> > > > > PS: Today (after adjusting tcp.highwater) I didn't get any screaming
> > > > > reports from users about hung vnc sessions. So maybe just maybe,
> > linux
> > > > > clients are able to somehow recover from this bad sequence messages.
> > I
> > > > > could still see the bad sequence error message in logs though
> > > > >
> > > > > Why isn't the highwater tunable set to something better by default ?
> > I
> > > > mean
> > > > > this server is certainly not under a high or unusual load (it's only
> > 40
> > > > PCs
> > > > > mounting from it)
> > > > >
> > > > > On Fri, Jul 3, 2015 at 1:15 AM, Ahmed Kamal <
> > > > email.ahmedkamal@googlemail.com
> > > > > > wrote:
> > > > >
> > > > > > Thanks all .. I understand now we're doing the "right thing" ..
> > > > Although
> > > > > > if mounting keeps wedging, I will have to solve it somehow! Either
> > > > using
> > > > > > Xin's patch .. or Upgrading RHEL to 6.x and using NFS4.1.
> > > > > >
> > > > > > Regarding Xin's patch, is it possible to build the patched nfsd
> > code,
> > > > as a
> > > > > > kernel module ? I'm looking to minimize my delta to upstream.
> > > > > >
> > > > Yes, you can build the nfsd as a module. If your kernel config does not
> > > > include
> > > > "options NFSD" the module will get loaded/used. It is also possible to
> > > > replace
> > > > the module without rebooting, but you need to kill of the nfsd daemon
> > then
> > > > kldunload nfsd.ko and replace nfsd.ko with the new one. (In
> > > > /boot/<kernel-name>.)
> > > >
> > > > > > Also would adopting Xin's patch and hiding it behind a
> > > > > > kern.nfs.allow_linux_broken_client be an option (I'm probably not
> > the
> > > > last
> > > > > > person on earth to hit this) ?
> > > > > >
> > > > If it fixes your problem, I think this is reasonable.
> > > > I'm also hoping that someone that works on the Linux client reports
> > > > if/when this
> > > > was changed.
> > > >
> > > > rick
> > > >
> > > > > > Thanks a lot for all the help!
> > > > > >
> > > > > > On Thu, Jul 2, 2015 at 11:53 PM, Rick Macklem <
> > rmacklem@uoguelph.ca>
> > > > > > wrote:
> > > > > >
> > > > > >> Ahmed Kamal wrote:
> > > > > >> > Appreciating the fruitful discussion! Can someone please
> > explain to
> > > > me,
> > > > > >> > what would happen in the current situation (linux client doing
> > this
> > > > > >> > skip-by-1 thing, and freebsd not doing it) ? What is the effect
> > of
> > > > that?
> > > > > >> Well, as you've seen, the Linux client doesn't function correctly
> > > > against
> > > > > >> the FreeBSD server (and probably others that don't support this
> > > > > >> "skip-by-1"
> > > > > >> case).
> > > > > >>
> > > > > >> > What do users see? Any chances of data loss?
> > > > > >> Hmm. Mostly it will cause Opens to fail, but I can't guess what
> > the
> > > > Linux
> > > > > >> client behaviour is after receiving NFS4ERR_BAD_SEQID. You're the
> > guy
> > > > > >> observing
> > > > > >> it.
> > > > > >>
> > > > > >> >
> > > > > >> > Also, I find it strange that netapp have acknowledged this is a
> > bug
> > > > on
> > > > > >> > their side, which has been fixed since then!
> > > > > >> Yea, I think Netapp screwed up. For some reason their server
> > allowed
> > > > this,
> > > > > >> then was fixed to not allow it and then someone decided that was
> > > > broken
> > > > > >> and
> > > > > >> reversed it.
> > > > > >>
> > > > > >> > I also find it strange that I'm the first to hit this :) Is no
> > one
> > > > > >> running
> > > > > >> > nfs4 yet!
> > > > > >> >
> > > > > >> Well, it seems to be slowly catching on. I suspect that the Linux
> > > > client
> > > > > >> mounting a Netapp is the most common use of it. Since it appears
> > that
> > > > they
> > > > > >> flip flopped w.r.t. who's bug this is, it has probably persisted.
> > > > > >>
> > > > > >> It may turn out that the Linux client has been fixed or it may
> > turn
> > > > out
> > > > > >> that most servers allowed this "skip-by-1" even though David
> > Noveck
> > > > (one
> > > > > >> of the main authors of the protocol) seems to agree with me that
> > it
> > > > should
> > > > > >> not be allowed.
> > > > > >>
> > > > > >> It is possible that others have bumped into this, but it wasn't
> > > > isolated
> > > > > >> (I wouldn't have guessed it, so it was good you pointed to the
> > RedHat
> > > > > >> discussion)
> > > > > >> and they worked around it by reverting to NFSv3 or similar.
> > > > > >> The protocol is rather complex in this area and changed
> > completely for
> > > > > >> NFSv4.1,
> > > > > >> so many have also probably moved onto NFSv4.1 where this won't be
> > an
> > > > > >> issue.
> > > > > >> (NFSv4.1 uses sessions to provide exactly once RPC semantics and
> > > > doesn't
> > > > > >> use
> > > > > >> these seqid fields.)
> > > > > >>
> > > > > >> This is all just mho, rick
> > > > > >>
> > > > > >> > On Thu, Jul 2, 2015 at 1:59 PM, Rick Macklem <
> > rmacklem@uoguelph.ca>
> > > > > >> wrote:
> > > > > >> >
> > > > > >> > > Julian Elischer wrote:
> > > > > >> > > > On 7/2/15 9:09 AM, Rick Macklem wrote:
> > > > > >> > > > > I am going to post to nfsv4@ietf.org to see what they
> > say.
> > > > Please
> > > > > >> > > > > let me know if Xin Li's patch resolves your problem, even
> > > > though I
> > > > > >> > > > > don't believe it is correct except for the UINT32_MAX
> > case.
> > > > Good
> > > > > >> > > > > luck with it, rick
> > > > > >> > > > and please keep us all in the loop as to what they say!
> > > > > >> > > >
> > > > > >> > > > the general N+2 bit sounds like bullshit to me.. its always
> > N+1
> > > > in a
> > > > > >> > > > number field that has a
> > > > > >> > > > bit of slack at wrap time (probably due to some ambiguity
> > in the
> > > > > >> > > > original spec).
> > > > > >> > > >
> > > > > >> > > Actually, since N is the lock op already done, N + 1 is the
> > next
> > > > lock
> > > > > >> > > operation in order. Since lock ops need to be strictly
> > ordered,
> > > > > >> allowing
> > > > > >> > > N + 2 (which means N + 2 would be done before N + 1) makes no
> > > > sense.
> > > > > >> > >
> > > > > >> > > I think the author of the RFC meant that N + 2 or greater
> > fails,
> > > > but
> > > > > >> it
> > > > > >> > > was poorly worded.
> > > > > >> > >
> > > > > >> > > I will pass along whatever I get from nfsv4@ietf.org. (There
> > is
> > > > an
> > > > > >> archive
> > > > > >> > > of it somewhere, but I can't remember where.;-)
> > > > > >> > >
> > > > > >> > > rick
> > > > > >> > > _______________________________________________
> > > > > >> > > freebsd-fs@freebsd.org mailing list
> > > > > >> > > http://lists.freebsd.org/mailman/listinfo/freebsd-fs
> > > > > >> > > To unsubscribe, send any mail to "
> > > > freebsd-fs-unsubscribe@freebsd.org"
> > > > > >> > >
> > > > > >> >
> > > > > >>
> > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>
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