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kernel BUG at /build/buildd/linux-2.6.35/fs/btrfs/volumes.c:1980!
invalid opcode: 0000 [#1] SMP 
last sysfs file: /sys/devices/pci0000:00/0000:00:06.0/usb1/1-1/1-1:1.0/uevent
CPU 0 
Modules linked in: binfmt_misc snd_intel8x0 snd_ac97_codec ac97_bus snd_pcm snd_seq_midi snd_rawmidi snd_seq_midi_event snd_seq snd_timer snd_seq_device ppdev parport_pc snd psmouse joydev serio_raw lp soundcore i2c_piix4 snd_page_alloc parport usbhid hid btrfs zlib_deflate ahci crc32c libahci libcrc32c e1000

Pid: 3132, comm: btrfs Not tainted 2.6.35-14-generic #19-Ubuntu /VirtualBox
RIP: 0010:[<ffffffffa009f25f>]  [<ffffffffa009f25f>] btrfs_balance+0x24f/0x260 [btrfs]
RSP: 0018:ffff88000cba1dc8  EFLAGS: 00010282
RAX: 00000000fffffffb RBX: ffff8800173aa090 RCX: ffffea0000077aa8
RDX: 0000000000000014 RSI: ffff880001d22970 RDI: 0000000000000282
RBP: ffff88000cba1e48 R08: ffffea0000077000 R09: 0000000000000004
R10: 0000000000000001 R11: 0000000000000001 R12: ffff88001816a000
R13: 0000000000000000 R14: 00000000a9c40000 R15: ffff88000cba1df8
FS:  00007fbfba080740(0000) GS:ffff880001e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 00007f0148608160 CR3: 000000000cbab000 CR4: 00000000000006f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process btrfs (pid: 3132, threadinfo ffff88000cba0000, task ffff88001e40adc0)
Stack:
 ffff88001816a800 0000000000000100 0000000000000100 000000a9c40000e4
<0> ffff880001d23c00 ffff88001f82f800 0000000000000100 000000d77bffffe4
<0> ffff88000cba1e00 ffffffff81128185 ffff88000ca03030 ffff880010f73300
Call Trace:
 [<ffffffff81128185>] ? page_add_new_anon_rmap+0x95/0xa0
 [<ffffffffa00a74b0>] btrfs_ioctl+0x2c0/0x4c0 [btrfs]
 [<ffffffff8116163d>] vfs_ioctl+0x3d/0xd0
 [<ffffffff81161f11>] do_vfs_ioctl+0x81/0x340
 [<ffffffff8158c9ae>] ? do_page_fault+0x15e/0x350
 [<ffffffff81162251>] sys_ioctl+0x81/0xa0
 [<ffffffff8100a0f2>] system_call_fastpath+0x16/0x1b
Code: fb ff 48 8b 45 80 48 8b b8 28 01 00 00 48 81 c7 20 1c 00 00 e8 d3 81 4e e1 e9 00 fe ff ff 45 31 ed eb d7 0f 0b eb fe 85 c0 74 a5 <0f> 0b eb fe 0f 0b eb fe 0f 0b eb fe 0f 0b eb fe 90 55 48 89 e5 
RIP  [<ffffffffa009f25f>] btrfs_balance+0x24f/0x260 [btrfs]
 RSP <ffff88000cba1dc8>
---[ end trace 42d9b3699d38b73a ]---