LOR: vfs_mount.c (ufs) / msdosfs_vfsops.c (devfs)

[Bruce Cran]

Running -CURRENT from today, I unmounted the msdosfs filesystem on my 
phone and got the following LOR:

lock order reversal:
 1st 0xffffff00c51279f8 ufs (ufs) @ /usr/src/sys/kern/vfs_mount.c:1204
 2nd 0xffffff010b892278 devfs (devfs) @ 
/usr/src/sys/modules/msdosfs/../../fs/msdosfs/msdosfs_vfsops.c:944
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2a
_witness_debugger() at witness_debugger+0x2e
witness_checkorder() at witness_checkorder+0x81e
__lockmgr_args() at __lockmgr_args+0xd11
vop_stdlock() at vop_stdlock+0x39
VOP_LOCK1_APV() VOP_LOCK1_APV+0x9b
_vn_lock() at _vn_lock+0x47
msdosfs_sync() at msdosfs_sync+0x227
dounmount() at dounmount+0x2ca
unmount() at unmount+0x216
syscall() at syscall+0x2a2
Xfast_syscall() at Xfast_syscall+0xe1
--- syscall (22, FreeBSD ELF64, unmount), rip = 0x8006a1e3c, rsp = 
0x7fffffffe3a8, rbp = 0x800c08010 ---

-- 
Bruce Cran