Date: Thu, 11 Feb 2021 22:54:19 +0000 From: Rick Macklem <rmacklem@uoguelph.ca> To: Alan Somers <asomers@freebsd.org> Cc: freebsd-fs <freebsd-fs@freebsd.org> Subject: Re: NFS delegations don't expire after unmounting client Message-ID: <YQXPR0101MB09687C56A3237F48FE6115C0DD8C9@YQXPR0101MB0968.CANPRD01.PROD.OUTLOOK.COM> In-Reply-To: <CAOtMX2jXC-h8kuKn2tqYyY1VnDmZd9Yy%2BjHQNwgmVBC8nHtYQQ@mail.gmail.com> References: <CAOtMX2h_2zCNpyzOs=SzuohRvLgga=Eip-LJ-7QjJBvwmueLXg@mail.gmail.com> <YQXPR0101MB09684A4372F120C3B3FE5BE5DD8C9@YQXPR0101MB0968.CANPRD01.PROD.OUTLOOK.COM>, <CAOtMX2jXC-h8kuKn2tqYyY1VnDmZd9Yy%2BjHQNwgmVBC8nHtYQQ@mail.gmail.com>
next in thread | previous in thread | raw e-mail | index | archive | help
Alan Somers wrote:=0A= >On Thu, Feb 11, 2021 at 2:54 PM Rick Macklem wrote:=0A= >>Alan Somers wrote:=0A= >>>I have several Linux 5.9.15 clients mounting NFS 4.1 served from a FreeB= SD=0A= >>>12.2-RELEASE server. Today, most of those clients' mounts hung, and the= ir=0A= >>>dmesg displayed "nfs: server XXX not responding, still trying".=0A= >>Usually these messages indicate a networking layer problem.=0A= >>Next time (or if it still happening), check basic network connectivity.= =0A= >>Also, if any net interface does not handle TSO correctly for an RPC=0A= >>message near 64Kbytes in size (the nasty one is where the NFS RPC is=0A= >>less than 64K by less than 14bytes, so when the MAC layer header is=0A= >>prepended, the total exceed 64K), you can get "stuck" TCP connections.=0A= >>Most FreeBSD net chip drivers should be fixed for this, but I wouldn't be= =0A= >>surprised if there are some broken ones out there.=0A= >>--> Disabling TSO fixes the problem in this case.=0A= >=0A= >In fact it is still happening. Basic network connectivity works. But tcp= dump shows almost no network activity. Just >a few keepalive packets of le= ngth 0-1. Based on the fact that unmount and even lsof hang on the client,= I'm >suspecting a Linux bug somewhere.=0A= Yea, without a packet capture being done when the failure first occurs, it = is pretty hard=0A= to diagnose.=0A= There is some way to turn on debugging output in Linux NFS, but I've forgot= ten how to do it.=0A= =0A= As an aside, delegations are rarely useful and make the protocol more compl= ex,=0A= including the need for callbacks to work correctly (in NFSv4.1, they normal= ly=0A= use the same TCP connection as the regular RPCs).=0A= - You might just want to disable them on the server. (You must have set the= sysctl non-zero,=0A= since they are disabled by default).=0A= =0A= Have fun with it, rick=0A= =0A= -Alan=0A=
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?YQXPR0101MB09687C56A3237F48FE6115C0DD8C9>