panic: vputonfreelist: lock count is not zero
Starting stack trace...
panic(ffffffff827da16e) at panic+0x155 sys/kern/subr_prf.c:229
vputonfreelist(fffffd8075da0b48) at vputonfreelist+0x19f sys/kern/vfs_subr.c:719
vput(fffffd8075da0b48) at vput+0xee sys/kern/vfs_subr.c:781
ufs_mknod(ffff80002497f3f0) at ufs_mknod+0x109 sys/ufs/ufs/ufs_vnops.c:190
VOP_MKNOD(fffffd806c027620,ffff80002497f550,ffff80002497f580,ffff80002497f480) at VOP_MKNOD+0xbf sys/kern/vfs_vops.c:121
domknodat(ffff80002170fa50,ffffff9c,200000c0,6100,8) at domknodat+0x326 sys/kern/vfs_syscalls.c:1628
syscall(ffff80002497f720) at syscall+0x446 sys/arch/amd64/amd64/trap.c:599
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0xf030c6cd7f0, count: 249
End of stack trace.
syncing disks...18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18  giving up

dump to dev 4,1 not possible
rebooting...
SeaBIOS (version 1.8.2-google)
Total RAM Size = 0x0000000080000000 = 2048 MiB
CPUs found: 2     Max CPUs supported: 2
SeaBIOS (version 1.8.2-google)
Machine UUID db0dc653-7a57-7afa-fd77-d87c02d918a4
found virtio-scsi at 0:3
virtio-scsi vendor='Google' product='PersistentDisk' rev='1' type=0 removable=0
virtio-scsi blksize=512 sectors=4194304 = 2048 MiB
drive 0x000f2480: PCHS=0/0/0 translation=lba LCHS=520/128/63 s=4194304
Sending Seabios boot VM event.
Booting from Hard Disk 0...
>> OpenBSD/amd64 BOOT 3.55
boot> show all pools
boot: illegal argument all
boot> machine ddbcpu 0
machine: syntax error
boot> trace
boot> machine ddbcpu 1
machine: syntax error
boot> trace