------------[ cut here ]------------
kernel BUG at /build/buildd/linux-3.2.0/fs/btrfs/transaction.c:1337!
invalid opcode: 0000 [#1] SMP 
CPU 0 
Modules linked in: nls_iso8859_1 nls_cp437 usb_storage ufs qnx4 hfsplus hfs minix ntfs vfat msdos fat jfs xfs reiserfs ext2 snd_hrtimer btusb parport_pc ppdev snd_hda_codec_conexant tp_smapi(O) thinkpad_ec(O) joydev pci_stub vboxpci(O) vboxnetadp(O) vboxnetflt(O) usbhid hid arc4 cdc_wdm cdc_ether cdc_acm usbnet vboxdrv(O) snd_hda_intel snd_hda_codec snd_hwdep snd_pcm iwlwifi snd_seq_midi snd_rawmidi snd_seq_midi_event psmouse serio_raw mac80211 snd_seq cfg80211 snd_timer snd_seq_device thinkpad_acpi nvram tpm_tis snd wmi bnep rfcomm bluetooth i915 soundcore snd_page_alloc drm_kms_helper mac_hid drm i2c_algo_bit video binfmt_misc mei(C) lp parport e1000e btrfs zlib_deflate libcrc32c

Pid: 13202, comm: umount Tainted: G         C O 3.2.0-20-generic #32-Ubuntu LENOVO 7453WQ2/7453WQ2
RIP: 0010:[<ffffffffa003a8ff>]  [<ffffffffa003a8ff>] btrfs_commit_transaction+0x82f/0x840 [btrfs]
RSP: 0018:ffff88022adc1d88  EFLAGS: 00010282
RAX: 00000000fffffffb RBX: ffff8801a8bf1000 RCX: 0000000000000000
RDX: ffff88022adc1c90 RSI: 0000000001c03000 RDI: ffff8801a8bf1060
RBP: ffff88022adc1e18 R08: 0000000000002000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801a8bf1078
R13: ffff8801c3462c00 R14: ffff880173770000 R15: 0000000000000000
FS:  00007f80ee95d800(0000) GS:ffff88023bc00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 00007fb668000020 CR3: 000000018008a000 CR4: 00000000000406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process umount (pid: 13202, threadinfo ffff88022adc0000, task ffff88022c4296f0)
Stack:
 0000000000000000 0000000000000001 0000000000000000 ffff88022c4296f0
 ffffffff8108aef0 ffff88022adc1db0 ffff88022adc1db0 00000000a0053cbb
 ffff88022adc1e58 ffff8801c3462c00 0000000000000001 ffff88022d3654c0
Call Trace:
 [<ffffffff8108aef0>] ? add_wait_queue+0x60/0x60
 [<ffffffffa001523c>] btrfs_sync_fs+0x6c/0xf0 [btrfs]
 [<ffffffff811a6523>] __sync_filesystem+0x63/0x90
 [<ffffffff811a65cb>] sync_filesystem+0x4b/0x70
 [<ffffffff81179bfb>] generic_shutdown_super+0x3b/0xe0
 [<ffffffff81179d36>] kill_anon_super+0x16/0x30
 [<ffffffff8117a37c>] deactivate_locked_super+0x3c/0xa0
 [<ffffffff8117abee>] deactivate_super+0x4e/0x70
 [<ffffffff8119720d>] mntput_no_expire+0x9d/0xf0
 [<ffffffff8119852b>] sys_umount+0x5b/0xd0
 [<ffffffff81664502>] system_call_fastpath+0x16/0x1b
Code: e9 90 f9 ff ff 0f 0b 0f 0b 0f 0b 0f 0b 0f 0b 0f 0b be fc 04 00 00 48 c7 c7 58 fb 08 a0 e8 ba c9 02 e1 e9 48 fb ff ff 0f 0b 0f 0b <0f> 0b 66 66 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 55 48 89 e5 
RIP  [<ffffffffa003a8ff>] btrfs_commit_transaction+0x82f/0x840 [btrfs]
 RSP <ffff88022adc1d88>
---[ end trace 4fc196cc3b54372c ]---