page fault in ufs_fhtovp

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

On a 6.1/amd64 NFS server, I got the following:

uvm_fault(0xfffffe82cd149228, 0x0, 1) -> e
fatal page fault in supervisor mode
trap type 6 code 0 rip ffffffff803fc5a1 cs 8 rflags 10246 cr2  c8 cpl 0 rsp 
fffffe82aaa38660
kernel: page fault trap, code=0
Stopped in pid 9953.3 (nfsd) at netbsd:ufs_fhtovp+0x2e: cmpw $0,c8(%rdx)

db{1}> bt
ufs_fhtovp() at netbsd:ufs_fhtovp+0x2e
ffs_fhtovp() at netbsd:ffs_fhtovp+0x55
VFS_FHTOVP() at netbsd:VFS_FHTOVP+0x1c
nfsrv_fhtovp() at netbsd:nfssrv_fhtovp+0x9a
nfsrv_write() at netbsd:nfssrv_write+0x502
nfssvc_nfsd() at netbsd:nfssvc_nfsd+0x1d7
sys_nfssvc() at netbsd:sys_nfssvc+0x22c
syscall() at netbsd:syscall+0xc4

db{1}> show reg
ds              30
es              bcf0
fs              bcf0
rdi             fffffe83bfbd3a78
rsi             1
rbp             fffffe82aaa38680
rbx             fffffe82aaa38680
rdx             0
rcx             fffffe823c1f5324
rax             0
r8              fffffe823c1f5320
r9              0
r10             0
r11             1
r12             fffffe82aaa38958
r13             fffffe8272333e00
r14             1
r15             fffffe8247b4a840
rip             ffffffff803fc5a1    ufs_fhtovp+0x2e
cs              8
rflags          10246
rsp             fffffe82aaa38660
ss              10
netbsd:ufs_fhtovp+0x2e: cmpw       $0,c8(%rdx)

I then tried reboot 4, but the machine hung such that I had to press reset.
Thanks to RAIDframe parity maps and WAPBL, I was back to normal rather quickly.
Does it ring a bell to someone? Anything I could have investigated further?