Date: Fri, 3 Jul 2015 01:21:00 +0200 From: Ahmed Kamal <email.ahmedkamal@googlemail.com> To: Rick Macklem <rmacklem@uoguelph.ca> 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: <CANzjMX5xyUz6OkMKS4O-MrV2w58YT9ricOPLJWVtAR5Ci-LMew@mail.gmail.com> In-Reply-To: <CANzjMX427XNQJ1o6Wh2CVy1LF1ivspGcfNeRCmv%2BOyApK2UhJg@mail.gmail.com> References: <CANzjMX45QaC8yZx2nHPAohJRvQjmUOHuhMQWP9nX%2BsrJs707Hg@mail.gmail.com> <684628776.2772174.1435793776748.JavaMail.zimbra@uoguelph.ca> <CANzjMX7xKBvnzJhQhB_ZrUnyE2m_FJXXy4fm_RFnuZfBDyDm2A@mail.gmail.com> <55947C6E.5060409@delphij.net> <1491630362.2785531.1435799383802.JavaMail.zimbra@uoguelph.ca> <5594B008.10202@freebsd.org> <1022558302.2863702.1435838360534.JavaMail.zimbra@uoguelph.ca> <CANzjMX5eN1FsnHMf6KGZe_b3vwxxF=dy3fJUHxeGO4BXuNzfPA@mail.gmail.com> <791936587.3443190.1435873993955.JavaMail.zimbra@uoguelph.ca> <CANzjMX427XNQJ1o6Wh2CVy1LF1ivspGcfNeRCmv%2BOyApK2UhJg@mail.gmail.com>
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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. > > 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) ? > > 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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