Bug#1071501: linux-image-6.1.0-21-arm64: Linux NFS client hangs in nfs4_lookup_revalidate

[Salvatore Bonaccorso <carnil@debian.org>]

Hi Richard,

On Mon, May 20, 2024 at 09:27:24AM +0000, Richard Kojedzinszky wrote:
> Package: src:linux
> Version: 6.1.90-1
> Severity: normal
> X-Debbugs-Cc: richard+debian+bugreport@kojedz.in
> 
> Dear Maintainer,
> 
> I am running kubernetes on debian, and pods are mounting multiple nfs
> shares. I am running dovecot processes in PODs, which receive mails from
> the internet, and also serves as imap server for clients. I am
> monitoring my mail system by sending mails periodically (15 seconds) and
> also downloading them via imap. I found a few times that some dovecot process
> stuck in D state, a reboot was always needed to recover from that state.
> 
> Unfortunately, I was not able to trigger the bug really fast, I dont
> really know what operations does dovecot issue and in what order to trigger
> this behavior. So until I get closer, I've set up a similar, but smaller
> environment with just a single dovecot process, and it also does the
> same work, delivering only test mails locally, and serving them via imap
> to the monitoring client, storing everything on NFS. Fortunately, this also
> triggers the bug, after a few hours one of the dovecot processes is stuck
> in D state. Kernel also shows blocked state:

As you seem in the lucky position to be able to trigger the issue in a
more localized setup, might you:

- try as well more recent kernels from upper suites (6.8.9-1 in
  unstable would be ideal to check if the issue is there as well).
- I did read you cannot trigger with 5.15. If you build 6.1.90 from
  upstream without Debian patches I assume you can trigger the issue
  likewise? If so could you bisect the changes introducing the issue?
  This is a cumbersome process in particular if you need few hours to
  trigger it  So maybe the following point could be done first:
- Can you report the issue to the linux-nfs list, keeping us in the
  loop?

Regards,
Salvatore