My setup: ext2 partition, exported to localhost; nfs4 mounted on localhost;
unionfs mounted on top of nfs4 mount. Issuing assorted regression tests via
the union. Kernel compiled with lockdep. Four of my tests (rmdir, readdir,
rename, and rename with whiteouts), trigger the same lockdep warning when
unmounting nfs4. It doesn't happen when unionfs is mounted on top of
anything else, including nfs2 and nfs3.
I've not tried to reproduce it w/o unionfs, but the lockdep warning below
appears to be unrelated to unionfs. If you'd like me to try and reproduce
it w/o unionfs, let me know.
Cheers,
Erez.
=======================================================
[ INFO: possible circular locking dependency detected ]
2.6.24-rc6-unionfs2 #80
-------------------------------------------------------
umount.nfs4/4017 is trying to acquire lock:
(&(&clp->cl_renewd)->work){--..}, at: [<c0223e53>] __cancel_work_timer+0x83/0x17f
but task is already holding lock:
(&clp->cl_sem){----}, at: [<f8879897>] nfs4_kill_renewd+0x17/0x29 [nfs]
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (&clp->cl_sem){----}:
[<c0230699>] __lock_acquire+0x9cc/0xb95
[<c0230c39>] lock_acquire+0x5f/0x78
[<c0397cb8>] down_read+0x3a/0x4c
[<f88798e6>] nfs4_renew_state+0x1c/0x1b8 [nfs]
[<c0223821>] run_workqueue+0xd9/0x1ac
[<c0224220>] worker_thread+0x7a/0x86
[<c0226b49>] kthread+0x3b/0x62
[<c02033a3>] kernel_thread_helper+0x7/0x10
[<ffffffff>] 0xffffffff
-> #0 (&(&clp->cl_renewd)->work){--..}:
[<c0230589>] __lock_acquire+0x8bc/0xb95
[<c0230c39>] lock_acquire+0x5f/0x78
[<c0223e87>] __cancel_work_timer+0xb7/0x17f
[<c0223f5a>] cancel_delayed_work_sync+0xb/0xd
[<f887989e>] nfs4_kill_renewd+0x1e/0x29 [nfs]
[<f885a8f6>] nfs_free_client+0x37/0x9e [nfs]
[<f885ab20>] nfs_put_client+0x5d/0x62 [nfs]
[<f885ab9a>] nfs_free_server+0x75/0xae [nfs]
[<f8862672>] nfs4_kill_super+0x27/0x2b [nfs]
[<c0258aab>] deactivate_super+0x3f/0x51
[<c0269668>] mntput_no_expire+0x42/0x67
[<c025d0e4>] path_release_on_umount+0x15/0x18
[<c0269d30>] sys_umount+0x1a3/0x1cb
[<c0269d71>] sys_oldumount+0x19/0x1b
[<c02026ca>] sysenter_past_esp+0x5f/0xa5
[<ffffffff>] 0xffffffff
other info that might help us debug this:
1 lock held by umount.nfs4/4017:
#0: (&clp->cl_sem){----}, at: [<f8879897>] nfs4_kill_renewd+0x17/0x29 [nfs]
stack backtrace:
Pid: 4017, comm: umount.nfs4 Not tainted 2.6.24-rc6-unionfs2 #80
[<c020371f>] show_trace_log_lvl+0x1a/0x2f
[<c02040a8>] show_trace+0x12/0x14
[<c020497f>] dump_stack+0x6c/0x72
[<c022eca5>] print_circular_bug_tail+0x5f/0x68
[<c0230589>] __lock_acquire+0x8bc/0xb95
[<c0230c39>] lock_acquire+0x5f/0x78
[<c0223e87>] __cancel_work_timer+0xb7/0x17f
[<c0223f5a>] cancel_delayed_work_sync+0xb/0xd
[<f887989e>] nfs4_kill_renewd+0x1e/0x29 [nfs]
[<f885a8f6>] nfs_free_client+0x37/0x9e [nfs]
[<f885ab20>] nfs_put_client+0x5d/0x62 [nfs]
[<f885ab9a>] nfs_free_server+0x75/0xae [nfs]
[<f8862672>] nfs4_kill_super+0x27/0x2b [nfs]
[<c0258aab>] deactivate_super+0x3f/0x51
[<c0269668>] mntput_no_expire+0x42/0x67
[<c025d0e4>] path_release_on_umount+0x15/0x18
[<c0269d30>] sys_umount+0x1a3/0x1cb
[<c0269d71>] sys_oldumount+0x19/0x1b
[<c02026ca>] sysenter_past_esp+0x5f/0xa5
=======================
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