ZFS: LOR in dbuf.c

Hi Pawel,

I upgraded my sources last night (just before your 2 commits) and now
I get this constant LOR every 5 seconds:

lock order reversal:
 1st 0xc7b90c20 zfs:&dr->dt.di.dr_mtx (zfs:&dr->dt.di.dr_mtx) _at_
/usr/src/sys/modules/zfs/../../contrib/opensolaris/uts/common/fs/zfs/dbuf.c:1866
 2nd 0xc48e17e4 zfs:&db->db_mtx (zfs:&db->db_mtx) _at_
/usr/src/sys/modules/zfs/../../contrib/opensolaris/uts/common/fs/zfs/dbuf.c:1888
KDB: stack backtrace:
db_trace_self_wrapper(c0a1ae29,e67a45a0,c076d9ee,c0a1d252,c48e17e4,...)
at db_trace_self_wrapper+0x26
kdb_backtrace(c0a1d252,c48e17e4,c0d1b6f4,c0d1b6f4,c0d1b5d1,...) at
kdb_backtrace+0x29
witness_checkorder(c48e17e4,9,c0d1b5d1,760,c48e17a8,...) at
witness_checkorder+0x6de
_sx_xlock(c48e17e4,c0d1b5d1,760,c1474788,1,...) at _sx_xlock+0x7a
dbuf_sync_list(c7b90c38,c894de80,74a,2,c48e0910,...) at dbuf_sync_list+0x16f
dbuf_sync_list(c48e09d0,c894de80,257,3,3,...) at dbuf_sync_list+0x107
dnode_sync(c48e0910,c894de80,7,3,3,...) at dnode_sync+0x1cd
dmu_objset_sync(c4441000,c47a4678,c894de80,0,c4441698,...) at
dmu_objset_sync+0x130
dsl_pool_sync(c4441600,49482,0,0,0,...) at dsl_pool_sync+0x190
spa_sync(c403d000,49482,0,c4441740,c444171c,...) at spa_sync+0x3f8
txg_sync_thread(c4441600,e67a4d38,c0a14eb6,324,c44b3900,...) at
txg_sync_thread+0x15a
fork_exit(c0ce46e0,c4441600,e67a4d38) at fork_exit+0xf1
fork_trampoline() at fork_trampoline+0x8
--- trap 0, eip = 0, esp = 0xe67a4d70, ebp = 0 ---

Let me know if you need more info.

-- 
Joao Barros