[Bug 2062568] Re: nfsd gets unresponsive after some hours of operation

[Jeff]

Ran into this again just hours after commenting by attempting to unpack a large archive file. Apparently the new setup of higher performance host with more network bandwidth is just too overwhelming to be usable with NFS with this issue.
Reading alone still seems to be fine though.

Torturing 50% of the memory with memtester didn't reveal any problems,
and getting the server to do the unpacking of files does the same mixed
I/O with no issues so far, progressing way beyond where I could get over
NFS, so it doesn't look like an HDD issue either.

The info dumping described here seems to be potentially useful for the next catch, so linking it here:
https://www.spinics.net/lists/linux-nfs/msg97486.html

At some point I may try to reproduce the issue with just writing to see
if the mixed workload is really required for the freeze, but not sure
when will I get to it, can't just restart NFSd, and the mandatory reboot
to get it going again is only feasible when all other tasks running on
the host can be interrupted.

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Title:
  nfsd gets unresponsive after some hours of operation

Status in nfs-utils package in Ubuntu:
  Confirmed

Bug description:
  I installed the 24.04 Beta on two test machines that were running
  22.04 without issues before. One of them exports two volumes that are
  mounted by the other machine, which primarily uses them as a secondary
  storage for ccache.

  After being up for a couple of hours (happened twice since yesterday
  evening) it seems that nfsd on the machine exporting the volumes hangs
  on something.

  From dmesg on the server (repeated a few times):

  [11183.290548] INFO: task nfsd:1419 blocked for more than 1228 seconds.
  [11183.290558]       Not tainted 6.8.0-22-generic #22-Ubuntu
  [11183.290563] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
  [11183.290582] task:nfsd            state:D stack:0     pid:1419  tgid:1419  ppid:2      flags:0x00004000
  [11183.290587] Call Trace:
  [11183.290602]  <TASK>
  [11183.290606]  __schedule+0x27c/0x6b0
  [11183.290612]  schedule+0x33/0x110
  [11183.290615]  schedule_timeout+0x157/0x170
  [11183.290619]  wait_for_completion+0x88/0x150
  [11183.290623]  __flush_workqueue+0x140/0x3e0
  [11183.290629]  nfsd4_probe_callback_sync+0x1a/0x30 [nfsd]
  [11183.290689]  nfsd4_destroy_session+0x186/0x260 [nfsd]
  [11183.290744]  nfsd4_proc_compound+0x3af/0x770 [nfsd]
  [11183.290798]  nfsd_dispatch+0xd4/0x220 [nfsd]
  [11183.290851]  svc_process_common+0x44d/0x710 [sunrpc]
  [11183.290924]  ? __pfx_nfsd_dispatch+0x10/0x10 [nfsd]
  [11183.290976]  svc_process+0x132/0x1b0 [sunrpc]
  [11183.291041]  svc_handle_xprt+0x4d3/0x5d0 [sunrpc]
  [11183.291105]  svc_recv+0x18b/0x2e0 [sunrpc]
  [11183.291168]  ? __pfx_nfsd+0x10/0x10 [nfsd]
  [11183.291220]  nfsd+0x8b/0xe0 [nfsd]
  [11183.291270]  kthread+0xef/0x120
  [11183.291274]  ? __pfx_kthread+0x10/0x10
  [11183.291276]  ret_from_fork+0x44/0x70
  [11183.291279]  ? __pfx_kthread+0x10/0x10
  [11183.291281]  ret_from_fork_asm+0x1b/0x30
  [11183.291286]  </TASK>

  From dmesg on the client (repeated a number of times):
  [ 6596.911785] RPC: Could not send backchannel reply error: -110
  [ 6596.972490] RPC: Could not send backchannel reply error: -110
  [ 6837.281307] RPC: Could not send backchannel reply error: -110

  ProblemType: Bug
  DistroRelease: Ubuntu 24.04
  Package: nfs-kernel-server 1:2.6.4-3ubuntu5
  ProcVersionSignature: Ubuntu 6.8.0-22.22-generic 6.8.1
  Uname: Linux 6.8.0-22-generic x86_64
  .etc.request-key.d.id_resolver.conf: create	id_resolver	*	*	/usr/sbin/nfsidmap -t 600 %k %d
  ApportVersion: 2.28.1-0ubuntu1
  Architecture: amd64
  CasperMD5CheckResult: pass
  Date: Fri Apr 19 14:10:25 2024
  InstallationDate: Installed on 2024-04-16 (3 days ago)
  InstallationMedia: Ubuntu-Server 24.04 LTS "Noble Numbat" - Beta amd64 (20240410.1)
  NFSMounts:

  NFSv4Mounts:

  ProcEnviron:
   LANG=en_US.UTF-8
   PATH=(custom, no user)
   SHELL=/bin/bash
   TERM=xterm-256color
   XDG_RUNTIME_DIR=<set>
  SourcePackage: nfs-utils
  UpgradeStatus: No upgrade log present (probably fresh install)

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