Crash in base/head in abd_put() after r320156

Has anyone else seen a crash in base/head in abd_put() after r320156?

One of my experimental VMs at home crashed spectacularly after 
upgrading to r320156. I even wiped my /usr/obj, recompiled everything 
and got the same result. Everything's back to normal when I boot 
r320146.

Here's the backtrace:

Fatal trap 12: page fault while in kernel mode
cpuid = 3; apic id = 03

fault virtual address	= 0x8

Fatal trap 12: page fault while in kernel mode

cpuid = 2; 
Fatal trap 12: page fault while in kernel mode
apic id = 02
fault virtual address	= 0x8
cpuid = 0; apic id = 00
fault virtual address	= 0x8
fault code		= supervisor read data, page not present
fault code		= supervisor read data, page not present
instruction pointer	= 0x20:0xffffffff803260fa
stack pointer	        = 0x28:0xfffffe01b0231860
frame pointer	        = 0x28:0xfffffe01b0231870
code segment		= base 0x0, limit 0xfffff, type 0x1b

			= DPL 0, pres 1, long 1, def32 0, gran 1

Fatal trap 12: page fault while in kernel mode
fault code		= supervisor read data, page not present
processor eflags	= interrupt enabled, resume, IOPL = 0
current process		= 0 (zio_free_issue_5_2)
trap number		= 12
instruction pointer	= 0x20:0xffffffff803260fa
stack pointer	        = 0x28:0xfffffe01b022c860
frame pointer	        = 0x28:0xfffffe01b022c870
panic: page fault
cpuid = 0
time = 4
KDB: stack backtrace:
db_trace_self_wrapper() at 0xffffffff8044f93b = db_trace_self_wrapper+0x2b/frame 0xfffffe01b0231440
vpanic() at 0xffffffff8067ec0c = vpanic+0x19c/frame 0xfffffe01b02314c0
panic() at 0xffffffff8067ea63 = panic+0x43/frame 0xfffffe01b0231520
trap_fatal() at 0xffffffff80983b32 = trap_fatal+0x322/frame 0xfffffe01b0231570
trap_pfault() at 0xffffffff80983b89 = trap_pfault+0x49/frame 0xfffffe01b02315d0
trap() at 0xffffffff809833c5 = trap+0x295/frame 0xfffffe01b0231790
calltrap() at 0xffffffff80968c21 = calltrap+0x8/frame 0xfffffe01b0231790
--- trap 0xc, rip = 0xffffffff803260fa, rsp = 0xfffffe01b0231860, rbp = 0xfffffe01b0231870 ---
abd_put() at 0xffffffff803260fa = abd_put+0xa/frame 0xfffffe01b0231870
vdev_raidz_map_free() at 0xffffffff803aa7c2 = vdev_raidz_map_free+0x82/frame 0xfffffe01b02318a0
zio_vdev_io_assess() at 0xffffffff803ecc04 = zio_vdev_io_assess+0x74/frame 0xfffffe01b02318e0
zio_execute() at 0xffffffff803e913c = zio_execute+0xac/frame 0xfffffe01b0231930
zio_vdev_io_start() at 0xffffffff803ec894 = zio_vdev_io_start+0x2b4/frame 0xfffffe01b0231990
zio_execute() at 0xffffffff803e913c = zio_execute+0xac/frame 0xfffffe01b02319e0
zio_nowait() at 0xffffffff803e8a8b = zio_nowait+0xcb/frame 0xfffffe01b0231a20
vdev_mirror_io_start() at 0xffffffff803a744c = vdev_mirror_io_start+0x35c/frame 0xfffffe01b0231a70
zio_vdev_io_start() at 0xffffffff803ec86c = zio_vdev_io_start+0x28c/frame 0xfffffe01b0231ad0
zio_execute() at 0xffffffff803e913c = zio_execute+0xac/frame 0xfffffe01b0231b20
taskqueue_run_locked() at 0xffffffff806d3d27 = taskqueue_run_locked+0x127/frame 0xfffffe01b0231b80
taskqueue_thread_loop() at 0xffffffff806d4ee8 = taskqueue_thread_loop+0xc8/frame 0xfffffe01b0231bb0
fork_exit() at 0xffffffff80640df5 = fork_exit+0x85/frame 0xfffffe01b0231bf0
fork_trampoline() at 0xffffffff8096915e = fork_trampoline+0xe/frame 0xfffffe01b0231bf0
--- trap 0, rip = 0, rsp = 0, rbp = 0 ---
Uptime: 4s

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| Vennlig hilsen,               | Best regards,                      |
| Trond Endrestøl,              | Trond Endrestøl,                   |
| IT-ansvarlig,                 | System administrator,              |
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