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 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.

rick

>
>
> FreeBSD version: FreeBSD 16.0-CURRENT installed from
> FreeBSD-16.0-CURRENT-amd64-20260505-8e8d87856241-285702
> uname -a
> FreeBSD fbsd7283 16.0-CURRENT FreeBSD 16.0-CURRENT
> main-n285769-1d24638d3e88 GENERIC amd64
> Delegations are ENABLED for nfsd.
>
> Windows version: Win11
> OpenZFS version:
> https://github.com/openzfsonwindows/openzfs/releases/download/zfswin-2.4.1rc11/OpenZFSOnWindows-debug-2.4.1rc11b.exe
> ms-nfs41-client version: ms-nfs41-client-release-2026-06-01
>
> Aurélien
> --
> Aurélien Couderc <[email protected]>
> Big Data/Data mining expert, chess enthusiast
>
>
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