Another lockdep issue reported with ecryptfs

[Roland Dreier <rdreier@cisco.com>]

Same setup as before: ecryptfs home directory on Ubuntu 9.10, with the
lockdep fix for ecryptfs I just posted (so lockdep is not being
instantly disabled on login); I got the following on a system with an
idle firefox-3.5 window:

 =============================================
 [ INFO: possible recursive locking detected ]
 2.6.31-2-generic #14~rbd3
 ---------------------------------------------
 firefox-3.5/4162 is trying to acquire lock:
  (&s->s_vfs_rename_mutex){+.+.+.}, at: [<ffffffff81139d31>] lock_rename+0x41/0xf0
 
 but task is already holding lock:
  (&s->s_vfs_rename_mutex){+.+.+.}, at: [<ffffffff81139d31>] lock_rename+0x41/0xf0
 
 other info that might help us debug this:
 3 locks held by firefox-3.5/4162:
  #0:  (&s->s_vfs_rename_mutex){+.+.+.}, at: [<ffffffff81139d31>] lock_rename+0x41/0xf0
  #1:  (&sb->s_type->i_mutex_key#11/1){+.+.+.}, at: [<ffffffff81139d5a>] lock_rename+0x6a/0xf0
  #2:  (&sb->s_type->i_mutex_key#11/2){+.+.+.}, at: [<ffffffff81139d6f>] lock_rename+0x7f/0xf0
 
 stack backtrace:
 Pid: 4162, comm: firefox-3.5 Tainted: G         C 2.6.31-2-generic #14~rbd3
 Call Trace:
  [<ffffffff8108ae74>] print_deadlock_bug+0xf4/0x100
  [<ffffffff8108ce26>] validate_chain+0x4c6/0x750
  [<ffffffff8108d2e7>] __lock_acquire+0x237/0x430
  [<ffffffff8108d585>] lock_acquire+0xa5/0x150
  [<ffffffff81139d31>] ? lock_rename+0x41/0xf0
  [<ffffffff815526ad>] __mutex_lock_common+0x4d/0x3d0
  [<ffffffff81139d31>] ? lock_rename+0x41/0xf0
  [<ffffffff81139d31>] ? lock_rename+0x41/0xf0
  [<ffffffff8120eaf9>] ? ecryptfs_rename+0x99/0x170
  [<ffffffff81552b36>] mutex_lock_nested+0x46/0x60
  [<ffffffff81139d31>] lock_rename+0x41/0xf0
  [<ffffffff8120eb2a>] ecryptfs_rename+0xca/0x170
  [<ffffffff81139a9e>] vfs_rename_dir+0x13e/0x160
  [<ffffffff8113ac7e>] vfs_rename+0xee/0x290
  [<ffffffff8113c212>] ? __lookup_hash+0x102/0x160
  [<ffffffff8113d512>] sys_renameat+0x252/0x280
  [<ffffffff81133eb4>] ? cp_new_stat+0xe4/0x100
  [<ffffffff8101316a>] ? sysret_check+0x2e/0x69
  [<ffffffff8108c34d>] ? trace_hardirqs_on_caller+0x14d/0x190
  [<ffffffff8113d55b>] sys_rename+0x1b/0x20
  [<ffffffff81013132>] system_call_fastpath+0x16/0x1b

haven't tried to debug this yet.