[linux-lvm] Snapshot removal fails first time under RAID

[Philip Boulain]

We have a Debian Wheezy server using mirrored RAID running kernel
3.2.0-1-amd64 and LVM version 2.02.88-2. There seems to be an issue
where snapshot removal fails due to being "in use" the first time, but
repeating the operation will succeed:

# lvcreate --size 128M --name testvolume buildturbo64
  Logical volume "testvolume" created
# lvcreate --size 128M --snapshot --name testsnap buildturbo64/testvolume
  Logical volume "testsnap" created
# lvremove buildturbo64/testsnap
Do you really want to remove active logical volume testsnap? [y/n]: y
  LV buildturbo64/testsnap in use: not deactivating
  Unable to deactivate logical volume "testsnap"
# lvremove buildturbo64/testsnap
Do you really want to remove active logical volume testsnap? [y/n]: y
  Logical volume "testsnap" successfully removed
# lvremove buildturbo64/testvolume
Do you really want to remove active logical volume testvolume? [y/n]: y
  Logical volume "testvolume" successfully removed

Note that no filesystem is even created here, so it's not mounted or
anything. That volume group has plenty of free extents (vgdisplay
excerpt):

  Alloc PE / Size       52353 / 204.50 GiB
  Free  PE / Size       66794 / 260.91 GiB

This is repeatable every time and waiting arbitrary delays between the
operations makes no difference. There is no difference if the logical
volume is specified by its device node (/dev/buildturbo64/testsnap).

Under a *non-RAID* Debian Wheezy VM with an otherwise identical
configuration, lvremove works first time, as I'd expect.

Is this a bug, or some form of user error?

Here is the verbose output of the remove steps, if that is helpful:

# lvremove --verbose buildturbo64/testsnap
    Using logical volume(s) on command line
Do you really want to remove active logical volume testsnap? [y/n]: y
    Archiving volume group "buildturbo64" metadata (seqno 117).
    Removing snapshot testsnap
    Found volume group "buildturbo64"
    Found volume group "buildturbo64"
    Loading buildturbo64-testvolume table (254:3)
    Loading buildturbo64-testsnap table (254:5)
    Suspending buildturbo64-testvolume (254:3) with device flush
    Suspending buildturbo64-testsnap (254:5) with device flush
    Suspending buildturbo64-testvolume-real (254:6) with device flush
    Suspending buildturbo64-testsnap-cow (254:7) with device flush
    Found volume group "buildturbo64"
    Resuming buildturbo64-testsnap-cow (254:7)
    Resuming buildturbo64-testvolume-real (254:6)
    Resuming buildturbo64-testsnap (254:5)
    Removing buildturbo64-testsnap-cow (254:7)
    Found volume group "buildturbo64"
    Resuming buildturbo64-testvolume (254:3)
    Removing buildturbo64-testvolume-real (254:6)
    Found volume group "buildturbo64"
  LV buildturbo64/testsnap in use: not deactivating
  Unable to deactivate logical volume "testsnap"
# lvremove --verbose buildturbo64/testsnap
    Using logical volume(s) on command line
Do you really want to remove active logical volume testsnap? [y/n]: y
    Archiving volume group "buildturbo64" metadata (seqno 118).
    Found volume group "buildturbo64"
    Removing buildturbo64-testsnap (254:5)
    Releasing logical volume "testsnap"
    Creating volume group backup "/etc/lvm/backup/buildturbo64" (seqno 119).
  Logical volume "testsnap" successfully removed

-- 
Philip Boulain
Developer

philip.boulain at smoothwall.net

Smoothwall Ltd
1 John Charles Way, Leeds, LS12 6QA United Kingdom
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