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[Robin Baumgartner <rb@xxxxxxxxxxxxxxxxx>]

I can confirm that this is still an issue in Ubuntu 14.04.4. I ran into
this problem trying to backup a server hosting lxc containers, some of
them using overlayfs as the root fs. When the containers are running
(and therefore overlayfs is mounted) lvcreate -s hangs forever. The
debug output is:

root@host:~# lvcreate -n foobar -L 5G -s -d -v /dev/vg0/var
    Setting logging type to disk
    Setting chunksize to 8 sectors.
    Finding volume group "vg0"
    Archiving volume group "vg0" metadata (seqno 5091).
    Creating logical volume foobar
    Creating volume group backup "/etc/lvm/backup/vg0" (seqno 5092).
    Found volume group "vg0"
    activation/volume_list configuration setting not defined: Checking only host tags for vg0/foobar
    Creating vg0-foobar
    Loading vg0-foobar table (252:5)
    Resuming vg0-foobar (252:5)
    Clearing start of logical volume "foobar"
    Creating logical volume snapshot0
    Found volume group "vg0"
    Found volume group "vg0"
    Executing: /sbin/modprobe dm-snapshot
    Creating vg0-var-real
    Loading vg0-var-real table (252:6)
    Loading vg0-var table (252:3)
    Creating vg0-foobar-cow
    Loading vg0-foobar-cow table (252:7)
    Resuming vg0-foobar-cow (252:7)
    Loading vg0-foobar table (252:5)
    Suspending vg0-var (252:3) with filesystem sync with device flush

When the containers are stopped (and therefore overlayfs is no longer
mounted), the snapshot is created without issues.

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https://bugs.launchpad.net/bugs/1328595

Title:
  lvcreate -s hangs when overlayfs is in use

Status in linux package in Ubuntu:
  Confirmed

Bug description:
  I am using xbuntu 14.04 LTS in combination with KVM, lxc, logical volumes and overlayfs.
  After I started  using overlayfs i realized that my backup based on LVM snapshots made the system "go mad".

  As described in the manual I tried the kernel from 13.10 (3.11.0-xx) with the same result.
  A test against main line does not help, since it does not include the overlayfs support.

  I tested the behaviour on a server as well as in a VirtualBox environment with the same result:
  lvcreate -s -n backup -L512M /dev/VG/NAME hangs and does not come back.

  This issue is easy reproducable:

  sudo mkdir /mnt/test /mnt/delta
  sudo mount -t overlayfs -o lowerdir=/usr,upperdir=/mnt/delta overlayfs /mnt/test
  sudo lvcreate -s -n backup -L512M /dev/xubuntu-vg/root

  -> Hang
  df@feretti-virt:~$ uname -r
  3.13.0-29-generic

  df@feretti-virt:~$ cat /proc/version_signature 
  Ubuntu 3.13.0-29.53-generic 3.13.11.2

  ProblemType: Bug
  DistroRelease: Ubuntu 14.04
  Package: linux-image-3.13.0-29-generic 3.13.0-29.53
  ProcVersionSignature: Ubuntu 3.13.0-29.53-generic 3.13.11.2
  Uname: Linux 3.13.0-29-generic x86_64
  ApportVersion: 2.14.1-0ubuntu3.2
  Architecture: amd64
  AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/by-path', '/dev/snd/controlC0', '/dev/snd/pcmC0D0c', '/dev/snd/pcmC0D0p', '/dev/snd/pcmC0D1c', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
  Date: Tue Jun 10 18:02:13 2014
  HibernationDevice: RESUME=UUID=6e68761a-6768-4e19-9c4e-f188538d6068
  InstallationDate: Installed on 2014-02-18 (112 days ago)
  InstallationMedia: Xubuntu 13.10 "Saucy Salamander" - Release amd64 (20131016)
  Lsusb:
   Bus 001 Device 002: ID 80ee:0021 VirtualBox USB Tablet
   Bus 001 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
  MachineType: innotek GmbH VirtualBox
  ProcEnviron:
   TERM=xterm
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=de_DE.UTF-8
   SHELL=/bin/bash
  ProcFB: 0 VESA VGA
  ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.13.0-29-generic root=/dev/mapper/xubuntu--vg-root ro quiet splash vt.handoff=7
  PulseList: Error: command ['pacmd', 'list'] failed with exit code 1: No PulseAudio daemon running, or not running as session daemon.
  RelatedPackageVersions:
   linux-restricted-modules-3.13.0-29-generic N/A
   linux-backports-modules-3.13.0-29-generic  N/A
   linux-firmware                             1.127.2
  RfKill:
   
  SourcePackage: linux
  UpgradeStatus: Upgraded to trusty on 2014-04-22 (49 days ago)
  dmi.bios.date: 12/01/2006
  dmi.bios.vendor: innotek GmbH
  dmi.bios.version: VirtualBox
  dmi.board.name: VirtualBox
  dmi.board.vendor: Oracle Corporation
  dmi.board.version: 1.2
  dmi.chassis.type: 1
  dmi.chassis.vendor: Oracle Corporation
  dmi.modalias: dmi:bvninnotekGmbH:bvrVirtualBox:bd12/01/2006:svninnotekGmbH:pnVirtualBox:pvr1.2:rvnOracleCorporation:rnVirtualBox:rvr1.2:cvnOracleCorporation:ct1:cvr:
  dmi.product.name: VirtualBox
  dmi.product.version: 1.2
  dmi.sys.vendor: innotek GmbH

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