Cam panic on r271170

I've been getting this quite frequently on head recently. I have dumps 
if anyone is interested in more information.

> Fatal trap 9: general protection fault while in kernel mode
> cpuid = 10; Memory modified after free 0xfffff8003e0b0800(2040) val=ffffffff _at_ 0xfffff8003e0b0808
> apanic: Most recently used by CAM CCB
>
> cpuid = 6
> KDB: stack backtrace:
> db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe124735b4c0
> kdb_backtrace() at kdb_backtrace+0x39/frame 0xfffffe124735b570
> vpanic() at vpanic+0x189/frame 0xfffffe124735b5f0
> panic() at panic+0x43/frame 0xfffffe124735b650
> mtrash_ctor() at mtrash_ctor+0x8a/frame 0xfffffe124735b680
> uma_zalloc_arg() at uma_zalloc_arg+0x4f1/frame 0xfffffe124735b6f0
> malloc() at malloc+0x192/frame 0xfffffe124735b740
> xpt_run_allocq() at xpt_run_allocq+0xb5/frame 0xfffffe124735b780
> adastrategy() at adastrategy+0x117/frame 0xfffffe124735b7b0
> g_io_request() at g_io_request+0x3b7/frame 0xfffffe124735b810
> g_part_start() at g_part_start+0x2b7/frame 0xfffffe124735b890
> g_io_request() at g_io_request+0x3b7/frame 0xfffffe124735b8f0
> g_io_request() at g_io_request+0x3b7/frame 0xfffffe124735b950
> vdev_geom_io_start() at vdev_geom_io_start+0x137/frame 0xfffffe124735b970
> zio_vdev_io_start() at zio_vdev_io_start+0x49f/frame 0xfffffe124735b9d0
> zio_execute() at zio_execute+0x204/frame 0xfffffe124735ba30
> vdev_queue_io_done() at vdev_queue_io_done+0x180/frame 0xfffffe124735ba80
> zio_vdev_io_done() at zio_vdev_io_done+0x11d/frame 0xfffffe124735bac0
> zio_execute() at zio_execute+0x204/frame 0xfffffe124735bb20
> taskqueue_run_locked() at taskqueue_run_locked+0xf0/frame 0xfffffe124735bb80
> taskqueue_thread_loop() at taskqueue_thread_loop+0x9b/frame 0xfffffe124735bbb0
> fork_exit() at fork_exit+0x84/frame 0xfffffe124735bbf0
> fork_trampoline() at fork_trampoline+0xe/frame 0xfffffe124735bbf0
> --- trap 0, rip = 0, rsp = 0xfffffe124735bcb0, rbp = 0 ---
> KDB: enter: panic
> [ thread pid 0 tid 100571 ]
> Stopped at      kdb_enter+0x3e: movq    $0,kdb_why


-- 
Regards,
Bryan Drewery