[2.6.27-rc4] XFS i_lock vs i_iolock...

[Daniel J Blueman]

On 2.6.27-rc4 with various debug options enabled, lockdep claims lock
ordering issues with XFS [1] - easiest reproducer is just running
xfs_fsr. Mount options I was using were
'nobarrier,noatime,nodiratime'.

Thanks,
  Daniel

--- [1]

=======================================================
[ INFO: possible circular locking dependency detected ]
2.6.27-rc4-224c #1
-------------------------------------------------------
xfs_fsr/5763 is trying to acquire lock:
 (&(&ip->i_lock)->mr_lock/2){--..}, at: [<ffffffff803ad8fc>] xfs_ilock+0x8c/0xb0

but task is already holding lock:
 (&(&ip->i_iolock)->mr_lock/3){--..}, at: [<ffffffff803ad915>]
xfs_ilock+0xa5/0xb0

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&(&ip->i_iolock)->mr_lock/3){--..}:
       [<ffffffff8026b011>] __lock_acquire+0xdb1/0x1150
       [<ffffffff8026b441>] lock_acquire+0x91/0xc0
       [<ffffffff8025d967>] down_write_nested+0x57/0x90
       [<ffffffff803ad915>] xfs_ilock+0xa5/0xb0
       [<ffffffff803cb086>] xfs_lock_two_inodes+0x106/0x120
       [<ffffffff803b78e0>] xfs_swap_extents+0x70/0x5b0
       [<ffffffff803b7f68>] xfs_swapext+0x148/0x150
       [<ffffffff803d8195>] xfs_ioctl+0x6a5/0x810
       [<ffffffff803d58bd>] xfs_file_ioctl_invis+0x3d/0x80
       [<ffffffff802d4586>] vfs_ioctl+0x36/0xb0
       [<ffffffff802d488b>] do_vfs_ioctl+0x28b/0x2f0
       [<ffffffff802d493f>] sys_ioctl+0x4f/0x80
       [<ffffffff8020c74b>] system_call_fastpath+0x16/0x1b
       [<ffffffffffffffff>] 0xffffffffffffffff

-> #0 (&(&ip->i_lock)->mr_lock/2){--..}:
       [<ffffffff8026b0f5>] __lock_acquire+0xe95/0x1150
       [<ffffffff8026b441>] lock_acquire+0x91/0xc0
       [<ffffffff8025d967>] down_write_nested+0x57/0x90
       [<ffffffff803ad8fc>] xfs_ilock+0x8c/0xb0
       [<ffffffff803caff0>] xfs_lock_two_inodes+0x70/0x120
       [<ffffffff803b7b03>] xfs_swap_extents+0x293/0x5b0
       [<ffffffff803b7f68>] xfs_swapext+0x148/0x150
       [<ffffffff803d8195>] xfs_ioctl+0x6a5/0x810
       [<ffffffff803d58bd>] xfs_file_ioctl_invis+0x3d/0x80
       [<ffffffff802d4586>] vfs_ioctl+0x36/0xb0
       [<ffffffff802d488b>] do_vfs_ioctl+0x28b/0x2f0
       [<ffffffff802d493f>] sys_ioctl+0x4f/0x80
       [<ffffffff8020c74b>] system_call_fastpath+0x16/0x1b
       [<ffffffffffffffff>] 0xffffffffffffffff

other info that might help us debug this:

2 locks held by xfs_fsr/5763:
 #0:  (&(&ip->i_iolock)->mr_lock/2){--..}, at: [<ffffffff803ad915>]
xfs_ilock+0xa5/0xb0
 #1:  (&(&ip->i_iolock)->mr_lock/3){--..}, at: [<ffffffff803ad915>]
xfs_ilock+0xa5/0xb0

stack backtrace:
Pid: 5763, comm: xfs_fsr Not tainted 2.6.27-rc4-224c #1

Call Trace:
 [<ffffffff80268d1f>] print_circular_bug_tail+0x9f/0xe0
 [<ffffffff8026b0f5>] __lock_acquire+0xe95/0x1150
 [<ffffffff8026b441>] lock_acquire+0x91/0xc0
 [<ffffffff803ad8fc>] ? xfs_ilock+0x8c/0xb0
 [<ffffffff8025d967>] down_write_nested+0x57/0x90
 [<ffffffff803ad8fc>] ? xfs_ilock+0x8c/0xb0
 [<ffffffff803ad8fc>] xfs_ilock+0x8c/0xb0
 [<ffffffff803caff0>] xfs_lock_two_inodes+0x70/0x120
 [<ffffffff803b7b03>] xfs_swap_extents+0x293/0x5b0
 [<ffffffff803b7f68>] xfs_swapext+0x148/0x150
 [<ffffffff803d8195>] xfs_ioctl+0x6a5/0x810
 [<ffffffff802148b0>] ? native_sched_clock+0x70/0xa0
 [<ffffffff802e24f2>] ? mnt_drop_write+0x62/0x140
 [<ffffffff803d58bd>] xfs_file_ioctl_invis+0x3d/0x80
 [<ffffffff802d4586>] vfs_ioctl+0x36/0xb0
 [<ffffffff802d488b>] do_vfs_ioctl+0x28b/0x2f0
 [<ffffffff8064128e>] ? trace_hardirqs_on_thunk+0x3a/0x3f
 [<ffffffff802d493f>] sys_ioctl+0x4f/0x80
 [<ffffffff8020c74b>] system_call_fastpath+0x16/0x1b
-- 
Daniel J Blueman
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