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[Brad Figg <brad.figg@xxxxxxxxxxxxx>]

** Package changed: linux-meta (Ubuntu) => linux (Ubuntu)

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https://bugs.launchpad.net/bugs/1252508

Title:
  during sys_exit, ip BUGs when dropping an ext3 superblock during
  namespace exit

Status in “linux” package in Ubuntu:
  New

Bug description:
  I've hit the same BUG twice in as many working days. I'll give a brief
  description of what I'm doing, paste the two BUG reports, then paste
  the requested information.

  I've been doing some performance testing on OpenStack. The tests just
  involve booting and deleting a bunch of virtual machine instances. A
  couple of things happen during VM creation that seem to cause the bug
  on. First, tap devices are created in various network namespaces.
  Second, nbd devices, served locally by qemu-nbd, with ext3 data are
  connected to /dev/nbd* and mounted and fiddled with.

  The ip program is used to operate in the network namespaces (ip netns
  exec ...). Occasionally, when ip exits, it hits a BUG in some block
  layer code. Apparently the BUGging ip task had the last reference to a
  mount.

  This BUG is fairly nasty because it happens when the superblock's
  s_umount semaphore is held, so other tasks that try to do stuff with
  the mount deadlock.

  Here are the processes involved in today's BUG:

  15488 sudo ip netns exec qdhcp-1ca153f0-3ece-4574-a0af-317c21cce5b4 ip route list dev tap4fad7e3b-f4
  15492  \_ [ip]
  27607 /bin/mount /dev/nbd13 /tmp/openstack-vfs-localfsKV3wPV
  27592 /usr/bin/qemu-nbd -c /dev/nbd13 /opt/stack/data/nova/instances/4d46d4f9-a812-4e84-8659-b30e8e01dd27/disk

   % sudo cat /proc/27607/stack
  [<ffffffff811df193>] __blkdev_get+0x63/0x4c0
  [<ffffffff811df7b5>] blkdev_get+0x1c5/0x340
  [<ffffffff811df9db>] blkdev_open+0x5b/0x80
  [<ffffffff811a4cab>] do_dentry_open+0x1eb/0x280
  [<ffffffff811a4dc9>] vfs_open+0x49/0x50
  [<ffffffff811b4111>] do_last+0x1c1/0xe40
  [<ffffffff811b5981>] path_openat+0xc1/0x630
  [<ffffffff811b6cfa>] do_filp_open+0x3a/0x90
  [<ffffffff811a5fac>] do_sys_open+0x12c/0x270
  [<ffffffff811a610e>] SyS_open+0x1e/0x20
  [<ffffffff816f521d>] system_call_fastpath+0x1a/0x1f
  [<ffffffffffffffff>] 0xffffffffffffffff

   % sudo cat /proc/27592/task/27595/stack
  [<ffffffff81369714>] call_rwsem_down_read_failed+0x14/0x30
  [<ffffffff811a99c5>] get_super+0x95/0xe0
  [<ffffffff811dee64>] fsync_bdev+0x14/0x60
  [<ffffffff81340824>] invalidate_partition+0x24/0x50
  [<ffffffff81343a19>] rescan_partitions+0x49/0x2c0
  [<ffffffff811df5e2>] __blkdev_get+0x4b2/0x4c0
  [<ffffffff811df7b5>] blkdev_get+0x1c5/0x340
  [<ffffffff811df9db>] blkdev_open+0x5b/0x80
  [<ffffffff811a4cab>] do_dentry_open+0x1eb/0x280
  [<ffffffff811a4dc9>] vfs_open+0x49/0x50
  [<ffffffff811b4111>] do_last+0x1c1/0xe40
  [<ffffffff811b5981>] path_openat+0xc1/0x630
  [<ffffffff811b6cfa>] do_filp_open+0x3a/0x90
  [<ffffffff811a5fac>] do_sys_open+0x12c/0x270
  [<ffffffff811a610e>] SyS_open+0x1e/0x20
  [<ffffffff816f521d>] system_call_fastpath+0x1a/0x1f
  [<ffffffffffffffff>] 0xffffffffffffffff

  I'm running on the stock ubuntu kernel; no custom modules have been
  inserted.

  This is the first BUG cut from a few days ago. I don't have the entire
  dmesg log from this run:

  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.131201] ------------[ cut here ]------------
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.131469] Kernel BUG at ffffffff811d77d4 [verbose debug info unavailable]
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.131881] invalid opcode: 0000 [#1] SMP 
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.132148] Modules linked in: xt_LOG(F) vhost_net vhost macvtap(F) macvlan(F) nf_conntrack_ipv6(F) nf_defrag_ipv6(F) ebt_arp(F) ebt_ip(F)
  xt_mac(F) xt_physdev(F) veth(F) xt_nat(F) xt_REDIRECT(F) ipt_MASQUERADE(F) iptable_nat(F) nf_nat_ipv4(F) nf_nat(F) nf_conntrack_ipv4(F) nf_defrag_ipv4(F) xt_conntrack(F) nf_conntrack(F
  ) ipt_REJECT(F) xt_CHECKSUM(F) iptable_mangle(F) xt_tcpudp(F) bridge(F) stp(F) llc(F) ip6table_filter(F) ip6_tables(F) iptable_filter(F) ip_tables(F) ebtable_nat(F) ebtables(F) x_tables
  (F) openvswitch(OF) dm_multipath(F) scsi_dh(F) nbd(F) vesafb(F) x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel(F) kvm(F) crct10dif_pclmul(F) crc32_pclmul(F) ghash_clmulni_inte
  l(F) aesni_intel(F) aes_x86_64(F) lrw(F) gf128mul(F) glue_helper(F) ablk_helper(F) cryptd(F) gpio_ich microcode(F) joydev(F) sb_edac edac_core mei_me mei lpc_ich ioatdma mac_hid lp(F) p
  arport(F) dm_snapshot(F) hid_generic igb isci ixgbe i2c_algo_bit usbhid dca hid libsas(F) ahci(F) ptp(F) libahci(
  Nov 15 14:52:44 node-0025904feb5c kernel: F) pps_core(F) mdio scsi_transport_sas(F)
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.138029] CPU: 15 PID: 27942 Comm: ip Tainted: GF          O 3.11.0-12-generic #19-Ubuntu
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.131881] invalid opcode: 0000 [#1] SMP 
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.132148] Modules linked in: xt_LOG(F) vhost_net vhost macvtap(F) macvlan(F) nf_conntrack_ipv6(F) nf_defrag_ipv6(F) ebt_arp(F) ebt_ip(F)
  xt_mac(F) xt_physdev(F) veth(F) xt_nat(F) xt_REDIRECT(F) ipt_MASQUERADE(F) iptable_nat(F) nf_nat_ipv4(F) nf_nat(F) nf_conntrack_ipv4(F) nf_defrag_ipv4(F) xt_conntrack(F) nf_conntrack(F
  ) ipt_REJECT(F) xt_CHECKSUM(F) iptable_mangle(F) xt_tcpudp(F) bridge(F) stp(F) llc(F) ip6table_filter(F) ip6_tables(F) iptable_filter(F) ip_tables(F) ebtable_nat(F) ebtables(F) x_tables
  ) ipt_REJECT(F) xt_CHECKSUM(F) iptable_mangle(F) xt_tcpudp(F) bridge(F) stp(F) llc(F) ip6table_filter(F) ip6_tables(F) iptable_filter(F) ip_tables(F) ebtable_nat(F) ebtables(F) x_tables
  (F) openvswitch(OF) dm_multipath(F) scsi_dh(F) nbd(F) vesafb(F) x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel(F) kvm(F) crct10dif_pclmul(F) crc32_pclmul(F) ghash_clmulni_inte
  l(F) aesni_intel(F) aes_x86_64(F) lrw(F) gf128mul(F) glue_helper(F) ablk_helper(F) cryptd(F) gpio_ich microcode(F) joydev(F) sb_edac edac_core mei_me mei lpc_ich ioatdma mac_hid lp(F) p
  arport(F) dm_snapshot(F) hid_generic igb isci ixgbe i2c_algo_bit usbhid dca hid libsas(F) ahci(F) ptp(F) libahci(
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.131881] invalid opcode: 0000 [#1] SMP 
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.132148] Modules linked in: xt_LOG(F) vhost_net vhost macvtap(F) macvlan(F) nf_conntrack_ipv6(F) nf_defrag_ipv6(F) ebt_arp(F) ebt_ip(F)
  xt_mac(F) xt_physdev(F) veth(F) xt_nat(F) xt_REDIRECT(F) ipt_MASQUERADE(F) iptable_nat(F) nf_nat_ipv4(F) nf_nat(F) nf_conntrack_ipv4(F) nf_defrag_ipv4(F) xt_conntrack(F) nf_conntrack(F
  ) ipt_REJECT(F) xt_CHECKSUM(F) iptable_mangle(F) xt_tcpudp(F) bridge(F) stp(F) llc(F) ip6table_filter(F) ip6_tables(F) iptable_filter(F) ip_tables(F) ebtable_nat(F) ebtables(F) x_tables
  (F) openvswitch(OF) dm_multipath(F) scsi_dh(F) nbd(F) vesafb(F) x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel(F) kvm(F) crct10dif_pclmul(F) crc32_pclmul(F) ghash_clmulni_inte
  l(F) aesni_intel(F) aes_x86_64(F) lrw(F) gf128mul(F) glue_helper(F) ablk_helper(F) cryptd(F) gpio_ich microcode(F) joydev(F) sb_edac edac_core mei_me mei lpc_ich ioatdma mac_hid lp(F) p
  arport(F) dm_snapshot(F) hid_generic igb isci ixgbe i2c_algo_bit usbhid dca hid libsas(F) ahci(F) ptp(F) libahci(
  Nov 15 14:52:44 node-0025904feb5c kernel: F) pps_core(F) mdio scsi_transport_sas(F)
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.138029] CPU: 15 PID: 27942 Comm: ip Tainted: GF          O 3.11.0-12-generic #19-Ubuntu
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.131881] invalid opcode: 0000 [#1] SMP 
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.132148] Modules linked in: xt_LOG(F) vhost_net vhost macvtap(F) macvlan(F) nf_conntrack_ipv6(F) nf_defrag_ipv6(F) ebt_arp(F) ebt_ip(F)
  xt_mac(F) xt_physdev(F) veth(F) xt_nat(F) xt_REDIRECT(F) ipt_MASQUERADE(F) iptable_nat(F) nf_nat_ipv4(F) nf_nat(F) nf_conntrack_ipv4(F) nf_defrag_ipv4(F) xt_conntrack(F) nf_conntrack(F
  ) ipt_REJECT(F) xt_CHECKSUM(F) iptable_mangle(F) xt_tcpudp(F) bridge(F) stp(F) llc(F) ip6table_filter(F) ip6_tables(F) iptable_filter(F) ip_tables(F) ebtable_nat(F) ebtables(F) x_tables
  (F) openvswitch(OF) dm_multipath(F) scsi_dh(F) nbd(F) vesafb(F) x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel(F) kvm(F) crct10dif_pclmul(F) crc32_pclmul(F) ghash_clmulni_inte
  l(F) aesni_intel(F) aes_x86_64(F) lrw(F) gf128mul(F) glue_helper(F) ablk_helper(F) cryptd(F) gpio_ich microcode(F) joydev(F) sb_edac edac_core mei_me mei lpc_ich ioatdma mac_hid lp(F) p
  arport(F) dm_snapshot(F) hid_generic igb isci ixgbe i2c_algo_bit usbhid dca hid libsas(F) ahci(F) ptp(F) libahci(
  Nov 15 14:52:44 node-0025904feb5c kernel: F) pps_core(F) mdio scsi_transport_sas(F)
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.138029] CPU: 15 PID: 27942 Comm: ip Tainted: GF          O 3.11.0-12-generic #19-Ubuntu
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.157795] Hardware name: Supermicro X9DRFR/X9DRFR, BIOS 1.0a 09/11/2012
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.167959] task: ffff88053c631770 ti: ffff88060d788000 task.ti: ffff88060d788000
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.189055] RIP: 0010:[<ffffffff811d77d4>]  [<ffffffff811d77d4>] _submit_bh+0x184/0x210
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.209728] RSP: 0018:ffff88060d789c98  EFLAGS: 00010246
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.220248] RAX: 0000000000000005 RBX: ffff880772e019c0 RCX: ffff88060d789fd8
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.241884] RDX: 0000000000000000 RSI: ffff880772e019c0 RDI: 0000000000000411
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.263641] RBP: ffff88060d789cb8 R08: 0000000000000000 R09: 0000000000000002
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.286483] R10: ffff880772e01068 R11: ffffffff8128badd R12: 0000000000000411
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.309833] R13: ffff8807a6499400 R14: ffff88076b528000 R15: 00007fff6b62dc00
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.333067] FS:  00007fb0e72c2740(0000) GS:ffff88085fd20000(0000) knlGS:0000000000000000
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.356632] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.368780] CR2: 00007fb1a1025f50 CR3: 00000007be808000 CR4: 00000000000427e0
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.384379]  nbd9: unknown partition table
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.403462] Stack:
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.414237]  ffff880772e019c0 0000000000000411 ffff8807a6499400 ffff88076b528000
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.436155]  ffff88060d789cd8 ffffffff811d84a5 ffff880772e019c0 ffff88060155e400
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.457077] kjournald starting.  Commit interval 5 seconds
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.480247] EXT3-fs (nbd9): using internal journal
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.480251] EXT3-fs (nbd9): mounted filesystem with ordered data mode
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.469329]  ffff88060d789ce8 ffffffff811d8543 ffff88060d789d10 ffffffff812310d0
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.513658] Call Trace:
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.524287]  [<ffffffff811d84a5>] __sync_dirty_buffer+0x55/0xe0
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.534920]  [<ffffffff811d8543>] sync_dirty_buffer+0x13/0x20
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.545623]  [<ffffffff812310d0>] ext3_commit_super.constprop.89+0x60/0xf0
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.556287]  [<ffffffff81231b21>] ext3_put_super+0x271/0x2a0
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.566461]  [<ffffffff811a8eb6>] generic_shutdown_super+0x56/0xe0
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.576653]  [<ffffffff811a9177>] kill_block_super+0x27/0x70
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.586668]  [<ffffffff811a94ed>] deactivate_locked_super+0x3d/0x60
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.596335]  [<ffffffff811a9556>] deactivate_super+0x46/0x60
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.606253]  [<ffffffff811c549f>] mntput_no_expire+0xef/0x150
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.615477]  [<ffffffff811c5526>] mntput+0x26/0x40
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.624622]  [<ffffffff811c563d>] namespace_unlock+0xfd/0x110
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.634156]  [<ffffffff811c7d4b>] put_mnt_ns+0x4b/0x60
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.643059]  [<ffffffff810891ab>] free_nsproxy+0x1b/0x90
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.651554]  [<ffffffff810893d5>] switch_task_namespaces+0x45/0x50
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.659768]  [<ffffffff810893f0>] exit_task_namespaces+0x10/0x20
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.667855]  [<ffffffff81064222>] do_exit+0x2b2/0xa40
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.676050]  [<ffffffff81064a2f>] do_group_exit+0x3f/0xa0
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.685242]  [<ffffffff81064aa4>] SyS_exit_group+0x14/0x20
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.693422]  [<ffffffff816f521d>] system_call_fastpath+0x1a/0x1f
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.701737] Code: 52 00 00 89 d8 5b 41 5c 41 5d 41 5e 5d c3 66 0f 1f 84 00 00 00 00 00 40 f6 c7 01 0f 84 e7 fe ff ff f0 80 66 01 f7 e9 dd fe ff ff <0f> 0b 49 8b 54 24 70 c1 e0 09 41 f6 c5 01 41 89 44 24 30 89 42 
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.725473] RIP  [<ffffffff811d77d4>] _submit_bh+0x184/0x210
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.733137]  RSP <ffff88060d789c98>
  Nov 15 14:52:44 node-0025904feb5c kernel: [1902861.753260] ---[ end trace 79cbd7bd94cca2ea ]---

  This is the second BUG cut from today. The full dmesg is attached.

  [Mon Nov 18 17:23:02 2013] ------------[ cut here ]------------
  [Mon Nov 18 17:23:02 2013] Kernel BUG at ffffffff811d77d4 [verbose debug info unavailable]
  [Mon Nov 18 17:23:02 2013] invalid opcode: 0000 [#1] SMP 
  [Mon Nov 18 17:23:02 2013] Modules linked in: nf_conntrack_ipv6(F) nf_defrag_ipv6(F) xt_mac(F) xt_physdev(F) vhost_net vhost macvtap(F) macvlan(F) xt_nat(F) xt_REDIRECT(F) ipt_MASQUERADE(F) iptable_nat(F) nf_nat_ipv4(F) nf_nat(F) nf_conntrack_ipv4(F) nf_defrag_ipv4(F) xt_conntrack(F) nf_conntrack(F) ipt_REJECT(F) xt_CHECKSUM(F) iptable_mangle(F) xt_tcpudp(F) bridge(F) stp(F) llc(F) ip6table_filter(F) ip6_tables(F) iptable_filter(F) ip_tables(F) ebtable_nat(F) ebtables(F) x_tables(F) ib_iser rdma_cm(F) ib_addr(F) iw_cm(F) ib_cm(F) ib_sa(F) ib_mad(F) ib_core(F) iscsi_tcp(F) libiscsi_tcp(F) libiscsi(F) scsi_transport_iscsi(F) openvswitch(OF) vesafb(F) gpio_ich x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel(F) kvm(F) crct10dif_pclmul(F) crc32_pclmul(F) ghash_clmulni_intel(F) aesni_intel(F) aes_x86_64(F) lrw(F) gf128mul(F) glue_helper(F) ablk_helper(F) cryptd(F) dm_multipath(F) microcode(F) scsi_dh(F) sb_edac edac_core joydev(F) mei_me mei lpc_ich ioatdma mac_hid lp(F) parport(F) dm_snapshot(F) hid_generic igb ixgbe usbhid isci i2c_algo_bit hid dca nbd(F) ahci(F) libsas(F) libahci(F) ptp(F) pps_core(F) mdio scsi_transport_sas(F)
  [Mon Nov 18 17:23:02 2013] CPU: 19 PID: 15492 Comm: ip Tainted: GF          O 3.11.0-12-generic #19-Ubuntu
  [Mon Nov 18 17:23:02 2013] Hardware name: Supermicro X9DRFR/X9DRFR, BIOS 1.0a 09/11/2012
  [Mon Nov 18 17:23:02 2013] task: ffff8810516f9770 ti: ffff88103e7ca000 task.ti: ffff88103e7ca000
  [Mon Nov 18 17:23:02 2013] RIP: 0010:[<ffffffff811d77d4>]  [<ffffffff811d77d4>] _submit_bh+0x184/0x210
  [Mon Nov 18 17:23:02 2013] RSP: 0018:ffff88103e7cbc98  EFLAGS: 00010246
  [Mon Nov 18 17:23:02 2013] RAX: 0000000000000005 RBX: ffff880701165820 RCX: ffff88103e7cbfd8
  [Mon Nov 18 17:23:02 2013] RDX: 0000000000000000 RSI: ffff880701165820 RDI: 0000000000000411
  [Mon Nov 18 17:23:02 2013]  nbd15: unknown partition table
  [Mon Nov 18 17:23:02 2013] RBP: ffff88103e7cbcb8 R08: 0000000000000000 R09: 0000000000000002
  [Mon Nov 18 17:23:02 2013] R10: ffff880701165888 R11: ffffffff8128badd R12: 0000000000000411
  [Mon Nov 18 17:23:02 2013] kjournald starting.  Commit interval 5 seconds
  [Mon Nov 18 17:23:02 2013] R13: ffff880802fef400 R14: ffff880eff6b4180 R15: 00007fff345eb930
  [Mon Nov 18 17:23:02 2013] EXT3-fs (nbd15): using internal journal
  [Mon Nov 18 17:23:02 2013] EXT3-fs (nbd15): mounted filesystem with ordered data mode
  [Mon Nov 18 17:23:02 2013] FS:  00007f3a9ddf1740(0000) GS:ffff88107fce0000(0000) knlGS:0000000000000000
  [Mon Nov 18 17:23:02 2013] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  [Mon Nov 18 17:23:02 2013] CR2: 00007fd38a321be0 CR3: 0000000001c0e000 CR4: 00000000000407f0
  [Mon Nov 18 17:23:02 2013] Stack:
  [Mon Nov 18 17:23:02 2013]  ffff880701165820 0000000000000411 ffff880802fef400 ffff880eff6b4180
  [Mon Nov 18 17:23:02 2013]  ffff88103e7cbcd8 ffffffff811d84a5 ffff880701165820 ffff88085422c000
  [Mon Nov 18 17:23:02 2013]  ffff88103e7cbce8 ffffffff811d8543 ffff88103e7cbd10 ffffffff812310d0
  [Mon Nov 18 17:23:02 2013] Call Trace:
  [Mon Nov 18 17:23:02 2013]  [<ffffffff811d84a5>] __sync_dirty_buffer+0x55/0xe0
  [Mon Nov 18 17:23:02 2013]  [<ffffffff811d8543>] sync_dirty_buffer+0x13/0x20
  [Mon Nov 18 17:23:02 2013]  [<ffffffff812310d0>] ext3_commit_super.constprop.89+0x60/0xf0
  [Mon Nov 18 17:23:02 2013]  [<ffffffff81231b21>] ext3_put_super+0x271/0x2a0
  [Mon Nov 18 17:23:02 2013]  [<ffffffff811a8eb6>] generic_shutdown_super+0x56/0xe0
  [Mon Nov 18 17:23:02 2013]  [<ffffffff811a9177>] kill_block_super+0x27/0x70
  [Mon Nov 18 17:23:02 2013]  [<ffffffff811a94ed>] deactivate_locked_super+0x3d/0x60
  [Mon Nov 18 17:23:02 2013]  [<ffffffff811a9556>] deactivate_super+0x46/0x60
  [Mon Nov 18 17:23:02 2013]  [<ffffffff811c549f>] mntput_no_expire+0xef/0x150
  [Mon Nov 18 17:23:02 2013]  [<ffffffff811c5526>] mntput+0x26/0x40
  [Mon Nov 18 17:23:02 2013]  [<ffffffff811c563d>] namespace_unlock+0xfd/0x110
  [Mon Nov 18 17:23:02 2013]  [<ffffffff811c7d4b>] put_mnt_ns+0x4b/0x60
  [Mon Nov 18 17:23:02 2013]  [<ffffffff810891ab>] free_nsproxy+0x1b/0x90
  [Mon Nov 18 17:23:02 2013]  [<ffffffff810893d5>] switch_task_namespaces+0x45/0x50
  [Mon Nov 18 17:23:02 2013]  [<ffffffff810893f0>] exit_task_namespaces+0x10/0x20
  [Mon Nov 18 17:23:02 2013]  [<ffffffff81064222>] do_exit+0x2b2/0xa40
  [Mon Nov 18 17:23:02 2013]  [<ffffffff81064a2f>] do_group_exit+0x3f/0xa0
  [Mon Nov 18 17:23:02 2013]  [<ffffffff81064aa4>] SyS_exit_group+0x14/0x20
  [Mon Nov 18 17:23:02 2013]  [<ffffffff816f521d>] system_call_fastpath+0x1a/0x1f
  [Mon Nov 18 17:23:02 2013] Code: 52 00 00 89 d8 5b 41 5c 41 5d 41 5e 5d c3 66 0f 1f 84 00 00 00 00 00 40 f6 c7 01 0f 84 e7 fe ff ff f0 80 66 01 f7 e9 dd fe ff ff <0f> 0b 49 8b 54 24 70 c1 e0 09 41 f6 c5 01 41 89 44 24 30 89 42 
  [Mon Nov 18 17:23:02 2013] RIP  [<ffffffff811d77d4>] _submit_bh+0x184/0x210
  [Mon Nov 18 17:23:02 2013]  RSP <ffff88103e7cbc98>
  [Mon Nov 18 17:23:02 2013] ---[ end trace 5fa4e7d1e416ec13 ]---

  
   % uname -a
  Linux node-0025904feb5c 3.11.0-12-generic #19-Ubuntu SMP Wed Oct 9 16:20:46 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
   % cat /proc/version_signature
  Ubuntu 3.11.0-12.19-generic 3.11.3

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