Re: [Ms-nfs41-client-devel] FreeBSD 16.0-CURRENT nfsd causes kernel panic when ms-nfs41-client runs WinZFS from file

On Tue, Jun 16, 2026 at 3:03 PM Rick Macklem <rick.macklem@gmail.com> wrote:
>
> On Tue, Jun 16, 2026 at 1:42 AM Aurélien Couderc
> <aurelien.couderc2002@gmail.com> wrote:
> >
> > FreeBSD NFSD causes repeated kernel panics with ms-nfs41-client, but
> > only if we run a Windows OpenZFS zpool from a NFS filesystem.
> >
> > Steps to use OpenZFS on NFS (I've send the instructions to Roland):
> > cd nfs_subdir_on_freebsd26
> > truncate -s $((512*1024*1024*1024)) poolfile1.bin
> > chmod a+rw poolfile1.bin
> > zpool.exe create -o ashift=15 -o autotrim=on -O
> > casesensitivity=insensitive -O driveletter=Z nfspool1
> > "\\\\?\\$(cygpath -w "$PWD/poolfile1.bin")"
> >
> > The ZFS filesystem on Windows works for a while until the FreeBSD
> > kernel drops into the kernel debugger prompt, warning that NFSD had
> > become unresponsive.
> >
> > How can I debug this?
> Capture packets until the FreeBSD server hangs. On the FreeBSD
> server:
> # tcpdump -s 0 -w out.pcap host <windows-client>
> --> Hopefully the hang doesn't result in a huge out.pcap, but..
>
> Create a bug report on bugs.freebsd.org and either attach
> out.pcap to it or email me w.r.t. where I can grab it.
>
> I need to be able to look at out.pcap in wireshark.
>
> Once the FreeBSD server appears hung..
> - If you can get onto it before it panics.
> # ps axHl > proc.txt
> # procstat -kk -a > stat.txt
> and attach both proc.txt and stat.txt to the bug report as well.

That machine panics after a while, when no one is around. I could
swear it senses the presence of our lab technicians, and only panics
when all are in meetings or out for getting a café noisette.

I did a wshark capture, but that file was almost 270GB and ANSSI will
declare a manhunt if I send the data around.
I need help with a clean, simple setup.

Aurélien
-- 
Aurélien Couderc <aurelien.couderc2002@gmail.com>
Big Data/Data mining expert, chess enthusiast