LOR: vm page queue mutex -> vnode interlock

Hi.

I get this LOR on boot (this is diskless machine):

Starting file system checks:
lock order reversal
 1st 0xc068f940 vm page queue mutex (vm page queue mutex) _at_ /usr/src/HEAD/src/sys/kern/vfs_bio.c:1485
 2nd 0xc127da30 vnode interlock (vnode interlock) _at_ /usr/src/HEAD/src/sys/kern/vfs_subr.c:1989
KDB: stack backtrace:
kdb_backtrace(0,ffffffff,c064eb28,c064d980,c061ab88) at kdb_backtrace+0x29
witness_checkorder(c127da30,9,c05f52cb,7c5) at witness_checkorder+0x54c
_mtx_lock_flags(c127da30,0,c05f52cb,7c5,c1253e70) at _mtx_lock_flags+0x5b
vdrop(c127d9b4) at vdrop+0x1d
vm_page_remove(c0ebde38,c0ebde38) at vm_page_remove+0xd4
vm_page_free_toq(c0ebde38,c0ebde38,40,c0ebde38,ca782a50) at vm_page_free_toqx90
vm_page_free(c0ebde38,c0ebde38) at vm_page_free+0x15
vfs_vmio_release(c4d644f0) at vfs_vmio_release+0x9b
brelse(c4d644f0,c4d644f0) at brelse+0x485
flushbuflist(c127da7c,1,c127da78,0,0) at flushbuflist+0x1c6
bufobj_invalbuf(c127da78,1,c116e730,0,0) at bufobj_invalbuf+0x10d
vinvalbuf(c127d9b4,1,c116e730,0,0) at vinvalbuf+0x1d
nfs_vinvalbuf(c127d9b4,1,c116e730,1,a) at nfs_vinvalbuf+0xc4
nfs_close(ca782b84) at nfs_close+0xca
VOP_CLOSE_APV(c06272c0,ca782b84) at VOP_CLOSE_APV+0x7e
vn_close(c127d9b4,a,c0fdf480,c116e730,ca782be8) at vn_close+0x8b
vn_closefile(c1214ca8,c116e730) at vn_closefile+0xca
fdrop_locked(c1214ca8,c116e730,c0fcb6ac,0,c05e999f) at fdrop_locked+0x88
fdrop(c1214ca8,c116e730,6a6,c0645100,0) at fdrop+0x24
closef(c1214ca8,c116e730,0,0,4) at closef+0x35f
close(c116e730,ca782d14,1,5,216) at close+0x1a3
syscall(2f,2f,2f,0,2814c160) at syscall+0x213
Xint0x80_syscall() at Xint0x80_syscall+0x1f
--- syscall (6, FreeBSD ELF32, close), eip = 0x280b909b, esp = 0xbfbfe8bc, ebp = 0xbfbfe8d8 ---

-- 
Pawel Jakub Dawidek                       http://www.wheel.pl
pjd_at_FreeBSD.org                           http://www.FreeBSD.org
FreeBSD committer                         Am I Evil? Yes, I Am!