[Bug 1556602] Re: LVM in 16.04 cannot mount LVM Cached Volumes created in 15.10

[Guy Thouret]

I've restored my system to a working state by building lvm2 from
upstream source that includes the referenced patch and using the
compiled lvm to do a config backup which added the missing metadata
attributes then using native lvm (lvm2 2.02.133-1ubuntu7) to restore the
config backup.

All is working now using lvm2 2.02.133-1ubuntu7 package.

guy at mediaserver:~/tools$ sudo lvs
  LV lv_cache has invalid cache's feature flag.
  LV lv_cache is missing cache policy name.
  Internal error: LV segments corrupted in lv_cache.

guy at mediaserver:~/tools$ sudo ./lvm vgcfgbackup -v
    Using volume group(s) on command line.
    Cache is missing cache policy, using mq.
    Cache is missing cache mode, using writethrough.
    Creating volume group backup "/etc/lvm/backup/vg1" (seqno 13).
  Volume group "vg1" successfully backed up.

guy at mediaserver:~/tools$ sudo vgcfgrestore vg1
  Restored volume group vg1

guy at mediaserver:~/tools$ sudo lvs
  LV    VG   Attr       LSize   Pool       Origin        Data%  Meta%  Move Log Cpy%Sync Convert
  media vg1  Cwi---C--- 500.00g [lv_cache] [media_corig]

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https://bugs.launchpad.net/bugs/1556602

Title:
  LVM in 16.04 cannot mount LVM Cached Volumes created in 15.10

Status in lvm2 package in Ubuntu:
  Confirmed

Bug description:
  I'm test driving Ubuntu Mate Beta 1 (from USB) on a machine that uses
  LVM caching. (I use some SSD to cache old hard drives). My LVM setup
  was created with Linux Mint Debian Edition - Betsy release.

  The system cannot mount these cached volumes due to the following
  error reported by 'pvs':

  ubuntu-mate at ubuntu-mate:~$ sudo pvs
    LV CacheArchive has invalid cache's feature flag.
    LV CacheArchive is missing cache policy name.
    Internal error: LV segments corrupted in CacheArchive.
    LV CacheArchive has invalid cache's feature flag.
    LV CacheArchive is missing cache policy name.
    Internal error: LV segments corrupted in CacheArchive.
    PV         VG   Fmt  Attr PSize   PFree 
    /dev/sda5  vga  lvm2 a--   80.00g 70.00g
    /dev/sda6  vga  lvm2 a--  160.00g 50.00g
    /dev/sdb1  vga  lvm2 a--  200.00g 50.00g

  I did a bit of googling and found a similar report for upgrades from
  Fedora 21 to Fedora 23. See
  https://bugzilla.redhat.com/show_bug.cgi?id=1282188.

  I'll annotate this bug with the LVM version from my existing Debian
  based configuration in a few minutes.

  This is a show-stopper for me because I use LVM caching on both of my
  PCs. It's a great way to marry a 256 GB SSD with a 2 TB hard drive. I
  keep the OS and some key partitions on the SSD and then use the rest
  of the SSD to cache the hard drive.

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: lvm2 2.02.133-1ubuntu7
  ProcVersionSignature: Ubuntu 4.4.0-7.22-generic 4.4.2
  Uname: Linux 4.4.0-7-generic x86_64
  ApportVersion: 2.20-0ubuntu3
  Architecture: amd64
  CasperVersion: 1.367
  CurrentDesktop: MATE
  Date: Sun Mar 13 12:48:41 2016
  LiveMediaBuild: Ubuntu-MATE 16.04 LTS "Xenial Xerus" - Alpha amd64 (20160224)
  ProcEnviron:
   TERM=xterm
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  SourcePackage: lvm2
  UpgradeStatus: No upgrade log present (probably fresh install)

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