LoR when drives are dirty

Another LoR for your review folks.  If my file system is dirty it
appears that the background fsck generates the following LoR.  Fairly
easy to reproduce on my box.



lock order reversal:
 1st 0xc4d6a164 ufs (ufs) _at_ ufs/ffs/ffs_snapshot.c:424
 2nd 0xd850d7c0 bufwait (bufwait) _at_ kern/vfs_bio.c:2443
 3rd 0xc4b0b058 ufs (ufs) _at_ ufs/ffs/ffs_snapshot.c:545
KDB: stack backtrace:
db_trace_self_wrapper(c0be8332,e696540c,c087a295,4,c0be39cf,...) at
db_trace_self_wrapper+0x26
kdb_backtrace(4,c0be39cf,c4523740,c4526730,e6965468,...) at
kdb_backtrace+0x29
_witness_debugger(c0beb040,c4b0b058,c0bdea8a,c4526730,c0c078ce,...) at
_witness_debugger+0x25
witness_checkorder(c4b0b058,9,c0c078c5,221,0,...) at witness_checkorder
+0x839
__lockmgr_args(c4b0b058,80100,c4b0b074,0,0,...) at __lockmgr_args+0x797
ffs_lock(e6965578,c0e7aa00,c4a770a4,80100,c4b0b000,...) at ffs_lock+0x8a
VOP_LOCK1_APV(c0ced860,e6965578,e6965598,c0d06180,c4b0b000,...) at
VOP_LOCK1_APV+0xb5
_vn_lock(c4b0b000,80100,c0c078c5,221,c4553200,...) at _vn_lock+0x5e
ffs_snapshot(c4a4fa00,c4b3e7c0,c0c09222,15e,3,...) at ffs_snapshot
+0x1527
ffs_mount(c4a4fa00,c4a77000,c0bf1665,3d7,c4839b20,...) at ffs_mount
+0x146f
vfs_donmount(c4a77000,211000,c4a54e80,c4a54e80,bfbfed04,...) at
vfs_donmount+0x130e
nmount(c4a77000,e6965cf8,c,e6965d38,c0ccadf0,...) at nmount+0xbe
syscall(e6965d38) at syscall+0x2a3
Xint0x80_syscall() at Xint0x80_syscall+0x20
--- syscall (378, FreeBSD ELF32, nmount), eip = 0x280e6cab, esp =
0xbfbfeb2c, ebp = 0xbfbfee78 ---
lock order reversal:
 1st 0xd850d7c0 bufwait (bufwait) _at_ kern/vfs_bio.c:2443
 2nd 0xc4961a1c snaplk (snaplk) _at_ ufs/ffs/ffs_snapshot.c:794
KDB: stack backtrace:
db_trace_self_wrapper(c0be8332,e696540c,c087a295,4,c0be39cf,...) at
db_trace_self_wrapper+0x26
kdb_backtrace(4,c0be39cf,c4523740,c4526a70,e6965468,...) at
kdb_backtrace+0x29
_witness_debugger(c0beb027,c4961a1c,c0c07923,c4526a70,c0c078ce,...) at
_witness_debugger+0x25
witness_checkorder(c4961a1c,9,c0c078c5,31a,c4d6a180,...) at
witness_checkorder+0x839
__lockmgr_args(c4961a1c,80400,c4d6a180,0,0,...) at __lockmgr_args+0x797
ffs_lock(e6965578,0,0,80400,c4d6a10c,...) at ffs_lock+0x8a
VOP_LOCK1_APV(c0ced860,e6965578,c1901b14,c0d06180,c4d6a10c,...) at
VOP_LOCK1_APV+0xb5
_vn_lock(c4d6a10c,80400,c0c078c5,31a,0,...) at _vn_lock+0x5e
ffs_snapshot(c4a4fa00,c4b3e7c0,c0c09222,15e,3,...) at ffs_snapshot
+0x28c6
ffs_mount(c4a4fa00,c4a77000,c0bf1665,3d7,c4839b20,...) at ffs_mount
+0x146f
vfs_donmount(c4a77000,211000,c4a54e80,c4a54e80,bfbfed04,...) at
vfs_donmount+0x130e
nmount(c4a77000,e6965cf8,c,e6965d38,c0ccadf0,...) at nmount+0xbe
syscall(e6965d38) at syscall+0x2a3
Xint0x80_syscall() at Xint0x80_syscall+0x20
--- syscall (378, FreeBSD ELF32, nmount), eip = 0x280e6cab, esp =
0xbfbfeb2c, ebp = 0xbfbfee78 ---
lock order reversal:
 1st 0xc4961a1c snaplk (snaplk) _at_ kern/vfs_vnops.c:293
 2nd 0xc4d6a164 ufs (ufs) _at_ ufs/ffs/ffs_snapshot.c:1588
KDB: stack backtrace:
db_trace_self_wrapper(c0be8332,e69658c4,c087a295,4,c0be39cf,...) at
db_trace_self_wrapper+0x26
kdb_backtrace(4,c0be39cf,c4526a70,c4526730,e6965920,...) at
kdb_backtrace+0x29
_witness_debugger(c0beb027,c4d6a164,c0bdea8a,c4526730,c0c078ce,...) at
_witness_debugger+0x25
witness_checkorder(c4d6a164,9,c0c078c5,634,0,...) at witness_checkorder
+0x839
__lockmgr_args(c4d6a164,80000,0,0,0,...) at __lockmgr_args+0x797
ffs_snapremove(c4d6a10c,c4a4fa00,0,c0bf2e5d,414,...) at ffs_snapremove
+0x11f
softdep_releasefile(c4a5a168,e6965aa8,2,c0e7a9d0,c0ccf6a4,...) at
softdep_releasefile+0x3b
ufs_inactive(e6965ae8,c4d6a180,c4d6a10c,c4d6a180,e6965b00,...) at
ufs_inactive+0x1bc
VOP_INACTIVE_APV(c0ced860,e6965ae8,c0bf1c91,92d,c0d06140,...) at
VOP_INACTIVE_APV+0xa5
vinactive(c0ced860,e6965b1c,c0bf1c91,8b3,129,...) at vinactive+0x8e
vput(c4d6a10c,e6965b54,c0bf2e5d,125,c0d05ea0,...) at vput+0x1db
vn_close(c4d6a10c,1,c456c400,c4a77000,e6965be0,...) at vn_close+0xee
vn_closefile(c4a64bd0,c4a77000,3,0,c4a64bd0,...) at vn_closefile+0xe9
_fdrop(c4a64bd0,c4a77000,e6965c1c,c087a0dc,0,c4a770a4,c0e7a9d0,c0cd0eb0,c0be0764,c4b4612c,44f,c0be075b,e6965c44,c0842890,c4b4612c,8,c0be075b,44f) at _fdrop+0x43
closef(c4a64bd0,c4a77000,44f,434,c4a64bd0,...) at closef+0x290
kern_close(c4a77000,4,e6965d2c,c0b3e1e3,c4a77000,...) at kern_close
+0x11d
close(c4a77000,e6965cf8,4,c0bebdc0,c0cc8b10,...) at close+0x1a
syscall(e6965d38) at syscall+0x2a3
Xint0x80_syscall() at Xint0x80_syscall+0x20
--- syscall (6, FreeBSD ELF32, close), eip = 0x28184c53, esp =
0xbfbfeb2c, ebp = 0xbfbfee78 ---


Sean