DF-2831 environment
===================
stock kernel : DragonFly dfbsd 6.5-DEVELOPMENT #0: Thu Jul  2 06:02:54 UTC 2026 root@dfbsd:/usr/obj/usr/src/sys/X86_64_GENERIC x86_64 (INVARIANTS)
instr kernel : #1: Tue Sep  1 21:58:05 UTC 2026 (kprintf tracing in dssize; panic.txt captured here)
fix+instr    : #2: Tue Sep  1 22:44:11 UTC 2026 (token fix + tracing; RAWPSIZE provenance)
final fix    : #3: Tue Sep  1 23:37:41 UTC 2026 (fix.diff as shipped)
compiler     : cc 8.3 [DragonFly] Release/2019-02-22
build        : cd /usr/src && make nativekernel && make installkernel (in-guest)
disk         : /dev/vn0 backed by 8 MiB file image (MBR + DFLYBSD slice s1 @ LBA128/8000 sectors + valid disklabel64, partition 'a' 2 MiB FS_SWAP)
hammer       : DIOCSYNCSLICEINFO ioctl with arg=1 on /dev/vn0 (forced reprobe; ~150-300k per run)
victim       : swapon("/dev/vn0s1a") + swapoff loop (d_psize -> dssize walk)