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

On Sat, Jun 20, 2026 at 9:17 AM Aurélien Couderc
<[email protected]> wrote:
>
> On Tue, Jun 16, 2026 at 3:03 PM Rick Macklem <[email protected]> wrote:
> >
> > On Tue, Jun 16, 2026 at 1:42 AM Aurélien Couderc
> > <[email protected]> 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.
The interesting stuff probably happens in the last minute before the hang.
So, if the capture goes up until the hang, you could just clip the
last bit of it.
(Wireshark will complain that the first packets aren't a complete RPC message,
but it usually can decode what follows.)

rick

> I need help with a clean, simple setup.
>
> Aurélien
> --
> Aurélien Couderc <[email protected]>
> Big Data/Data mining expert, chess enthusiast
>