Bug#344040: lvm2: sometimes can create snapshot, sometimes can't

[Filippo Giunchedi]

Package: lvm2
Version: 2.02.01-1
Severity: normal

consider the following setup:

# /sbin/lvscan
  ACTIVE            '/dev/chroots/unstable' [1.00 GB] inherit
  ACTIVE            '/dev/chroots/experimental' [1.00 GB] inherit

I can't deterministically create snapshot of the above LVs:

# lvcreate --verbose --snapshot --name test1 --size 1g chroots/experimental
    Setting chunksize to 16 sectors.
    Finding volume group "chroots"
    Archiving volume group "chroots" metadata (seqno 203).
    Creating logical volume test1
    Creating volume group backup "/etc/lvm/backup/chroots" (seqno 204).
    Found volume group "chroots"
    Creating chroots-test1
    Loading chroots-test1 table
    Resuming chroots-test1 (253:1)
    Zeroing start of logical volume "test1"
    Found volume group "chroots"
  LV chroots/test1 in use: not deactivating
  Couldn't deactivate new snapshot.

but sometimes I can successfully create snapshots.. looks like there is some
cache (write_cache_state = 0 though) or some locking mechanism, lvm dumpconfig follows:

devices {
	dir="/dev"
	scan="/dev"
	filter=["r|/dev/cdrom|", "r|/dev/nbd.*|"]
	cache="/etc/lvm/.cache"
	write_cache_state=0
	sysfs_scan=1
	md_component_detection=0
}
activation {
	missing_stripe_filler="/dev/ioerror"
	mirror_region_size=512
	reserved_stack=256
	reserved_memory=8192
	process_priority=-18
}
global {
	umask=63
	test=0
	activation=1
	proc="/proc"
	locking_type=1
	locking_dir="/var/lock/lvm"
}
shell {
	history_size=100
}
backup {
	backup=1
	backup_dir="/etc/lvm/backup"
	archive=1
	archive_dir="/etc/lvm/archive"
	retain_min=10
	retain_days=30
}
log {
	verbose=0
	syslog=1
	overwrite=0
	level=0
	indent=1
	command_names=0
	prefix="  "
}

-- System Information:
Debian Release: testing/unstable
  APT prefers experimental
  APT policy: (650, 'experimental'), (600, 'unstable')
Architecture: powerpc (ppc)
Shell:  /bin/sh linked to /bin/bash
Kernel: Linux 2.6.15-rc5
Locale: LANG=en_US, LC_CTYPE=en_US (charmap=ISO-8859-1)

Versions of packages lvm2 depends on:
ii  debconf [debconf-2.0]        1.4.62      Debian configuration management sy
ii  libc6                        2.3.5-9     GNU C Library: Shared libraries an
ii  libdevmapper1.02             2:1.02.02-1 The Linux Kernel Device Mapper use
ii  libncurses5                  5.5-1       Shared libraries for terminal hand
ii  libreadline5                 5.0-11      GNU readline and history libraries
ii  libselinux1                  1.26-1      SELinux shared libraries
ii  lvm-common                   1.5.20      The Logical Volume Manager for Lin

lvm2 recommends no packages.

-- no debconf information