panic in g_vfs_strategy()

After a forced umount of a msdos filesystem, I received
a panic.  I have the kernel and vmcore.  The first hundred
or so lines of core.txt.4 follow my .sig.

-- 
Steve


troutmask.apl.washington.edu dumped core - see /var/crash/vmcore.4

Tue Jun 21 14:32:29 PDT 2016

FreeBSD troutmask.apl.washington.edu 11.0-CURRENT FreeBSD 11.0-CURRENT #0 r299122: Thu May  5 10:03:31 PDT 2016     kargl_at_troutmask.apl.washington.edu:/data/obj/usr/src/sys/SPEW  amd64

panic: general protection fault

Unread portion of the kernel message buffer:
Device da1s1 went missing before all of the data could be written to it; expect data loss.

Fatal trap 9: general protection fault while in kernel mode
cpuid = 0; apic id = 10
instruction pointer	= 0x20:0xffffffff8050c4a1
stack pointer	        = 0x28:0xfffffe0239276fc0
frame pointer	        = 0x28:0xfffffe0239277000
code segment		= base 0x0, limit 0xfffff, type 0x1b
			= DPL 0, pres 1, long 1, def32 0, gran 1
processor eflags	= interrupt enabled, resume, IOPL = 0
current process		= 30604 (sendmail)
trap number		= 9
panic: general protection fault
cpuid = 0
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe0239276c60
vpanic() at vpanic+0x182/frame 0xfffffe0239276ce0
panic() at panic+0x43/frame 0xfffffe0239276d40
trap_fatal() at trap_fatal+0x351/frame 0xfffffe0239276da0
trap() at trap+0x6d1/frame 0xfffffe0239276f00
calltrap() at calltrap+0x8/frame 0xfffffe0239276f00
--- trap 0x9, rip = 0xffffffff8050c4a1, rsp = 0xfffffe0239276fd0, rbp = 0xfffffe0239277000 ---
g_vfs_strategy() at g_vfs_strategy+0x31/frame 0xfffffe0239277000
bufwrite() at bufwrite+0x1da/frame 0xfffffe0239277040
vop_stdfsync() at vop_stdfsync+0x220/frame 0xfffffe02392770b0
devfs_fsync() at devfs_fsync+0x67/frame 0xfffffe02392770e0
VOP_FSYNC_APV() at VOP_FSYNC_APV+0x80/frame 0xfffffe0239277110
bufsync() at bufsync+0x35/frame 0xfffffe0239277140
bufobj_invalbuf() at bufobj_invalbuf+0x126/frame 0xfffffe02392771b0
vgonel() at vgonel+0x17e/frame 0xfffffe0239277220
vgone() at vgone+0x4c/frame 0xfffffe0239277250
devfs_delete() at devfs_delete+0x1f3/frame 0xfffffe02392772c0
devfs_populate_loop() at devfs_populate_loop+0x20f/frame 0xfffffe0239277320
devfs_populate() at devfs_populate+0x2a/frame 0xfffffe0239277340
devfs_populate_vp() at devfs_populate_vp+0x9b/frame 0xfffffe0239277390
devfs_lookup() at devfs_lookup+0x2c/frame 0xfffffe02392774a0
VOP_LOOKUP_APV() at VOP_LOOKUP_APV+0x7a/frame 0xfffffe02392774d0
lookup() at lookup+0x561/frame 0xfffffe0239277560
namei() at namei+0x3ef/frame 0xfffffe0239277620
vn_open_cred() at vn_open_cred+0x26c/frame 0xfffffe0239277790
kern_openat() at kern_openat+0x220/frame 0xfffffe0239277910
amd64_syscall() at amd64_syscall+0x33f/frame 0xfffffe0239277a30
Xfast_syscall() at Xfast_syscall+0xfb/frame 0xfffffe0239277a30
--- syscall (499, FreeBSD ELF64, sys_openat), rip = 0x2015336da, rsp = 0x7fffffffb328, rbp = 0x7fffffffb410 ---
Uptime: 7d21h3m52s
Dumping 1033 out of 8143 MB:..2%..11%..21%..31%..41%..52%..61%..72%..81%..92%

#0  doadump (textdump=1) at pcpu.h:221
221	pcpu.h: No such file or directory.
	in pcpu.h
(kgdb) #0  doadump (textdump=1) at pcpu.h:221
#1  0xffffffff8057e7f2 in kern_reboot (howto=260)
    at /usr/src/sys/kern/kern_shutdown.c:366
#2  0xffffffff8057ec6b in vpanic (fmt=<value optimized out>, 
    ap=<value optimized out>) at /usr/src/sys/kern/kern_shutdown.c:759
#3  0xffffffff8057eaa3 in panic (fmt=0x0)
    at /usr/src/sys/kern/kern_shutdown.c:690
#4  0xffffffff807e5ab1 in trap_fatal (frame=0xfffffe0239276f10, eva=0)
    at /usr/src/sys/amd64/amd64/trap.c:841
#5  0xffffffff807e5741 in trap (frame=0xfffffe0239276f10)
    at /usr/src/sys/amd64/amd64/trap.c:203
#6  0xffffffff807cc133 in calltrap ()
    at /usr/src/sys/amd64/amd64/exception.S:236
#7  0xffffffff8050c4a1 in g_vfs_strategy (bo=0xfffff801303510d0, 
    bp=0xfffffe01f05637c0) at atomic.h:184
#8  0xffffffff8060d41a in bufwrite (bp=0xfffffe01f05637c0) at buf.h:405
#9  0xffffffff8061a750 in vop_stdfsync (ap=0xfffffe0239277120)
    at /usr/src/sys/kern/vfs_default.c:695
#10 0xffffffff8047d637 in devfs_fsync (ap=0xfffffe0239277120)
    at /usr/src/sys/fs/devfs/devfs_vnops.c:694
#11 0xffffffff8084d920 in VOP_FSYNC_APV (vop=<value optimized out>, 
    a=<value optimized out>) at vnode_if.c:1331
#12 0xffffffff8060d535 in bufsync (bo=<value optimized out>, 
    waitfor=<value optimized out>) at vnode_if.h:549
#13 0xffffffff80627686 in bufobj_invalbuf (bo=<value optimized out>, 
    flags=<value optimized out>, slpflag=<value optimized out>, 
    slptimeo=<value optimized out>) at /usr/src/sys/kern/vfs_subr.c:1539
#14 0xffffffff8062a20e in vgonel (vp=<value optimized out>)
    at /usr/src/sys/kern/vfs_subr.c:1617
#15 0xffffffff8062a6bc in vgone (vp=0xfffff80130351000)
    at /usr/src/sys/kern/vfs_subr.c:3079
#16 0xffffffff80477e33 in devfs_delete (dm=0xfffff800088d6080, 
    de=0xfffff8022d551500, flags=0) at /usr/src/sys/fs/devfs/devfs_devs.c:397
#17 0xffffffff804782df in devfs_populate_loop (dm=<value optimized out>, 
    cleanup=<value optimized out>) at /usr/src/sys/fs/devfs/devfs_devs.c:535
#18 0xffffffff804780ba in devfs_populate (dm=<value optimized out>)
    at /usr/src/sys/fs/devfs/devfs_devs.c:662
#19 0xffffffff8047cd1b in devfs_populate_vp (vp=0xfffff8000a0071d8)
    at /usr/src/sys/fs/devfs/devfs_vnops.c:241
#20 0xffffffff8047aeec in devfs_lookup (ap=0xfffffe0239277518)
    at /usr/src/sys/fs/devfs/devfs_vnops.c:1050
#21 0xffffffff8084c48a in VOP_LOOKUP_APV (vop=<value optimized out>, 
    a=<value optimized out>) at vnode_if.c:127
#22 0xffffffff8061e3e1 in lookup (ndp=<value optimized out>) at vnode_if.h:54
#23 0xffffffff8061db6f in namei (ndp=<value optimized out>)
    at /usr/src/sys/kern/vfs_lookup.c:306
#24 0xffffffff8063839c in vn_open_cred (ndp=<value optimized out>, 
    flagp=0xfffffe02392778cc, cmode=0, vn_open_flags=<value optimized out>, 
    cred=<value optimized out>, fp=0xffffffff80040b30)
    at /usr/src/sys/kern/vfs_vnops.c:277
#25 0xffffffff80631790 in kern_openat (td=0xfffff8013adf1000, fd=-100, 
    path=0x48a13c <Address 0x48a13c out of bounds>, pathseg=UIO_USERSPACE, 
    flags=808784080, mode=<value optimized out>)
    at /usr/src/sys/kern/vfs_syscalls.c:998
#26 0xffffffff807e623f in amd64_syscall (td=0xfffff8013adf1000, traced=0)
    at subr_syscall.c:135
#27 0xffffffff807cc41b in Xfast_syscall ()
    at /usr/src/sys/amd64/amd64/exception.S:396
#28 0x00000002015336da in ?? ()
Previous frame inner to this frame (corrupt stack?)
Current language:  auto; currently minimal