kern/106030: panic while rebooting with a dead disk

[mjacob at freebsd.org]

And just to note that this isn't necessarily part of rebooting
(I'll change the summary)... Note that errno=6 is a pretty
good hint to the upper layers that the device is now gone.

I really don't see how I can make multipathing work for Ironport unless 
I or somebody else fixes this.

(da7:isp1:0:6:1): isp1: watchdog timeout for handle 0x363
(da7:isp1:0:6:1): isp1: watchdog timeout for handle 0x364
(da6:isp1:0:6:0): isp1: watchdog timeout for handle 0x362
(da7:isp1:0:6:1): isp1: watchdog timeout for handle 0x365
(da6:isp1:0:6:0): isp1: watchdog timeout for handle 0x366
(da7:isp1:0:6:1): isp1: watchdog timeout for handle 0x367
g_vfs_done():(da6:isp1:0:6:0): lost device
(da7:isp1:0:6:1): lost device
(da8:isp1:0:6:2): lost device
(da8:isp1:0:6:2): removing device entry
(da7:isp1:0:6:1): Invalidating pack
stripe/billa[WRITE(offset=65536, length=2048)]error = 6
g_vfs_done():stripe/billa[WRITE(offset=6144000, length=2048)]error = 6
g_vfs_done():stripe/billa[WRITE(offset=192790528, length=16384)]error = 
6
panic: bundirty: buffer 0xc6d8a4d0 still on queue 1
cpuid = 1
KDB: enter: panic
[thread pid 3 tid 100000 ]
Stopped at      kdb_enter+0x2b: nop
db> bt
Tracing pid 3 tid 100000 td 0xc1e98000
kdb_enter(c09365e4) at kdb_enter+0x2b
panic(c093f31c,c6d8a4d0,1,c6d8a4d0,cba0ec48,...) at panic+0x127
bundirty(c6d8a4d0) at bundirty+0x35
brelse(c6d8a4d0) at brelse+0x82f
bufdone_finish(c6d8a4d0) at bufdone_finish+0x34c
bufdone(c6d8a4d0) at bufdone+0xaa
ffs_backgroundwritedone(c6d8a4d0) at ffs_backgroundwritedone+0xca
bufdone(c6d8a4d0) at bufdone+0x8f
g_vfs_done(c22b9000) at g_vfs_done+0x8a
biodone(c22b9000) at biodone+0x58
g_io_schedule_up(c1e98000) at g_io_schedule_up+0xe6
g_up_procbody(0,cba0ed38) at g_up_procbody+0x5a
fork_exit(c067d570,0,cba0ed38) at fork_exit+0xac
fork_trampoline() at fork_trampoline+0x8
--- trap 0x1, eip = 0, esp = 0xcba0ed6c, ebp = 0 ---