6.1/amd64 panic in ufs_fhtovp

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

This happened on my 6.1/amd64 NFS server:

uvm_fault(0xfffffe8419d06490, 0x0, 1) -> e
fatal page fault in supervisor mode
trap type 6 code 0 rip ffffffff803fa3d1 cs 8 rflags 10246 cr2  c8 cpl 0 rsp ff 
fe811db1e660
kernel: page fault trap, code=0
stopped in pid 430.2 (nfsd) at  netbsd:ufs_fhtovp+0x2e: cmpw    $0,c8(%rdx)

uvs_fhtovp() at netbsd:uvs_fhtovp+0x2e
ffs_fhtovp() at netbsd:ffs_fhtovp+0x55
VFS_FHTOVP() at netbsd:VFS_FHTOVP+0x1c
nfsrvc_fhtovp() at netbsd:nfsrv_fhtovv+0x9a
nfsrvc_write() at netbsd:nfsrvc_write+0x502
nfssvc_nfsd at netbsd:nfssvc_nfsd+0x1d7
sys_nfssvc() at netbsd:sys_nfssvc+0x22c
syscall() at netbsd:syscall+0xc4

ds      30
es      1cf8
fs      2790
gs      5000
rdi     fffffe82f87a43f8
rsi     1
rbp     fffffe811db1e680
rbx     fffffe811db1e690
rdx     0
rcx     fffffe8419f4e024
rax     0
r8      fffffe8419f4e020
r9      0
r10     0
r11     1
r12     fffffe811db1e958
r13     fffffe8088290e00
r14     1
r15     fffffe80d1f306c0
rip     ffffffff803fa3d1        ufs_fhtovp+0x2e
cs      8
rflags  10246
rsp     fffffe811db1e660
ss      10
netbsd:ufs_fhtovp+0x2e: cmpw    $0,c8(%rdx)

It then hung on the ddb reboot. I pressed Ctrl-Alt-ESC and tried reboot 0x4,
which hung. I had to press the reset button.