Our mail server's Dovecot uses inotify to watch file modifications, and this occured in kernel log:

[189824.600064] ------------[ cut here ]------------
[189824.600087] WARNING: at fs/notify/inotify/inotify_fsnotify.c:129 idr_callback+0x36/0x60()
[189824.600090] Hardware name: VMware Virtual Platform
[189824.600092] inotify closing but id=0 for entry=ffff88023db1a9a0 in group=ffff8801d8eedf00 still in idr.  Probably leaking memory
[189824.600095] Modules linked in:
[189824.600098] Pid: 26618, comm: imap Not tainted 2.6.32.2-VMWARE #1
[189824.600101] Call Trace:
[189824.600105]  [<ffffffff810e0326>] ? idr_callback+0x36/0x60
[189824.600108]  [<ffffffff810e0326>] ? idr_callback+0x36/0x60
[189824.600112]  [<ffffffff8103f404>] ? warn_slowpath_common+0x74/0xd0
[189824.600116]  [<ffffffff8103f4c1>] ? warn_slowpath_fmt+0x51/0x60
[189824.600121]  [<ffffffff814689bc>] ? _spin_lock_irq+0xc/0x10
[189824.600125]  [<ffffffff81466576>] ? wait_for_common+0x156/0x1a0
[189824.600129]  [<ffffffff8103b330>] ? default_wake_function+0x0/0x10
[189824.600132]  [<ffffffff810e0326>] ? idr_callback+0x36/0x60
[189824.600137]  [<ffffffff812645c4>] ? idr_for_each+0x84/0xe0
[189824.600139]  [<ffffffff810e02f0>] ? idr_callback+0x0/0x60
[189824.600144]  [<ffffffff810de5c7>] ? fsnotify_remove_priv_from_event+0x17/0x90
[189824.600147]  [<ffffffff810e02da>] ? inotify_free_group_priv+0x1a/0x30
[189824.600150]  [<ffffffff810de7db>] ? fsnotify_final_destroy_group+0x1b/0x30
[189824.600154]  [<ffffffff810e056c>] ? inotify_release+0x2c/0x50
[189824.600158]  [<ffffffff810af63d>] ? __fput+0xcd/0x1f0
[189824.600161]  [<ffffffff810abb1a>] ? filp_close+0x4a/0x80
[189824.600164]  [<ffffffff810abc03>] ? sys_close+0xb3/0x120
[189824.600168]  [<ffffffff8100b482>] ? system_call_fastpath+0x16/0x1b
[189824.600170] ---[ end trace fab63940f8ddf26e ]---
[189824.600172] entry->group=(null) inode=(null) wd=4096