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

On Tue, Jun 16, 2026 at 10:41 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?

Panic text on FreeBSD console:

panic: deadlres_td_sleep_q: possible deadlock detected for 0xfffff
800b8169700 (nfsd: service), blocked for 180216 ticks cpuid = 0 time =
1781600416 KDB: stack backtrace: db_trace_self_wrapper() at
db_trace_self_wrapper+0x2b/frame 0xfffffe00adde9d20 vpanic() at
vpanic+0x149/frame 0xfffffe00adde9e50 panic() at panic+0x43/frame
0xfffffe00adde9eb0 deadlkres() at deadlkres+0x32a/frame
0xfffffe00adde9ef0 fork_exit() at fork_exit+0x82/frame
0xfffffe00adde9f30 fork_trampoline() at fork_trampoline+0xe/frame
0xfffffe00adde9f30 --- trap 0, rip = 0, rsp = 0, rbp = 0 --- KDB:
enter: panic [ thread pid 0 tid 100101 ] Stopped at kdb_enter+0x33:
movq $0,0x15dc172(%rip) db>

Aurélien
-- 
Aurélien Couderc <[email protected]>
Big Data/Data mining expert, chess enthusiast