LOR on nfs: vfs_vnops.c:301 kern_descrip.c:1580

Hi.

Seeing on mostly idle, recently updated current, while closing a file.
Presumably never reported on ML.

lock order reversal:
 1st 0xffffff00198199f8 nfs (nfs) _at_ /usr/src/sys/kern/vfs_vnops.c:301
 2nd 0xffffff000234a048 filedesc structure (filedesc structure) _at_
/usr/src/sys/kern/kern_descrip.c:1580
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2a
_witness_debugger() at _witness_debugger+0x2e
witness_checkorder() at witness_checkorder+0x807
_sx_xlock() at _sx_xlock+0x55
fdinit() at fdinit+0x5b
fdcopy() at fdcopy+0x2a
fork1() at fork1+0x836
kproc_create() at kproc_create+0x63
nfs_nfsiodnew() at nfs_nfsiodnew+0xd7
nfs_asyncio() at nfs_asyncio+0xa6
nfs_strategy() at nfs_strategy+0x83
bufstrategy() at bufstrategy+0x43
nfs_writebp() at nfs_writebp+0xcf
nfs_flush() at nfs_flush+0x1dc
nfs_close() at nfs_close+0x213
vn_close() at vn_close+0x10e
vn_closefile() at vn_closefile+0x5a
_fdrop() at _fdrop+0x23
closef() at closef+0x5b
kern_close() at kern_close+0x110
syscallenter() at syscallenter+0x1aa
syscall() at syscall+0x4c
Xfast_syscall() at Xfast_syscall+0xe2
--- syscall (6, FreeBSD ELF64, close), rip = 0x80089830c, rsp =
0x7fffffffea88, rbp = 0 ---


-- 
wbr,
pluknet