Continuing in the investigation have better defined the reasons of the
bug. The following command gives the number of references to my
filesystem ocfs. Here are the results of this command before starting
the service o2cb.

r...@db1:~# ocfs2_hb_ctl -I -u FC046AD7B2584E7EB12A7293993C81B0
ocfs2_hb_ctl: Unable to access cluster service Cannot initialize cluster

After starting the service o2cb the number of references is always zero.

r...@db1:~# /etc/init.d/o2cb start
Loading filesystem "configfs": OK
Mounting configfs filesystem at /sys/kernel/config: OK
Loading stack plugin "o2cb": OK
Loading filesystem "ocfs2_dlmfs": OK
Mounting ocfs2_dlmfs filesystem at /dlm: OK
Setting cluster stack "o2cb": OK
Starting O2CB cluster ocfs2: OK

r...@db1:~# ocfs2_hb_ctl -I -u FC046AD7B2584E7EB12A7293993C81B0
FC046AD7B2584E7EB12A7293993C81B0: 0 refs

After mounting, the number of references becomes 1.

r...@db1:~# mount -v -t ocfs2 /dev/gfsapp/gfs /mnt/gfs
device=/dev/mapper/gfsapp-gfs
/dev/mapper/gfsapp-gfs on /mnt/gfs type ocfs2 (rw,_netdev,heartbeat=local)

r...@db1:~# ocfs2_hb_ctl -I -u FC046AD7B2584E7EB12A7293993C81B0
FC046AD7B2584E7EB12A7293993C81B0: 1 refs

The reference number is still 1 after umounting.

r...@db1:~# umount -v /mnt/gfs
eseguito umount di /dev/mapper/gfsapp-gfs

r...@db1:~# ocfs2_hb_ctl -I -u FC046AD7B2584E7EB12A7293993C81B0
FC046AD7B2584E7EB12A7293993C81B0: 1 refs

Now the service o2cb can not be stopped.

r...@db1:~# /etc/init.d/o2cb stop
Cleaning heartbeat on ocfs2:
DEBUG ocfs2_hb_ctl -I -u FC046AD7B2584E7EB12A7293993C81B0 2>&1
DEBUG FC046AD7B2584E7EB12A7293993C81B0: 1 refs
DEBUG REF=1
Failed
At least one heartbeat region still active

If you mount the ocfs filesystem again the number of references becomes
2.

r...@db1:~# mount -v -t ocfs2 /dev/gfsapp/gfs /mnt/gfs
device=/dev/mapper/gfsapp-gfs
/dev/mapper/gfsapp-gfs on /mnt/gfs type ocfs2 (rw,_netdev,heartbeat=local)

r...@db1:~# ocfs2_hb_ctl -I -u FC046AD7B2584E7EB12A7293993C81B0
FC046AD7B2584E7EB12A7293993C81B0: 2 refs

At this point I tried to stop the heartbeat ocfs directly with the
command ocfs2_hb_ctl -K.

r...@db1:~# umount -v /mnt/gfs
eseguito umount di /dev/mapper/gfsapp-gfs

r...@db1:~# ocfs2_hb_ctl -I -u FC046AD7B2584E7EB12A7293993C81B0
FC046AD7B2584E7EB12A7293993C81B0: 2 refs

r...@db1:~# ocfs2_hb_ctl -K -u FC046AD7B2584E7EB12A7293993C81B0
ocfs2_hb_ctl: File not found by ocfs2_lookup while stopping heartbeat

ocfs2_hb_ctl exits with an error because it can not find the device
corresponding to ocfs filesystem. This program reads the file
/proc/partitions and uses the column name to find the ocfs filesystem
device. My /proc/partitions file is:

r...@db1:~# cat /proc/partitions 
major minor  #blocks  name

 104        0   71652960 cciss/c0d0
 104        1   63865856 cciss/c0d0p1
 104        2    7785472 cciss/c0d0p2
   8        0  244141056 sda
   8        1  244139741 sda1
   8       32  488282112 sdc
   8       16 1758130176 sdb
   8       48  488282112 sdd
 251        0  488280064 dm-0
 251        1  488280064 dm-1
 251        2   20971520 dm-2
   8       64  244141056 sde
   8       65  244139741 sde1
   8       80 1758130176 sdf
   8      112  488282112 sdh
 251        3 1737154560 dm-3
   8       96  488282112 sdg

The name that corresponds to the ocfs filesystem device is dm-0. This
device does not exist as shown by the following command.

r...@db1:~# ll /dev/dm-0
ls: can not access /dev/dm-0: Nessun file o directory

The device dm-0 is not created even if udev contains the rules to make
it, as shown by the following commands (I use the default udev rules
with this distribution).

r...@db1:~# udevadm info --query=all --name=gfsapp/gfs
P: /devices/virtual/block/dm-0
N: mapper/gfsapp-gfs
L: 50
W: 197
S: block/251:0
S: dm-0
S: disk/by-id/dm-name-gfsapp-gfs
S: 
disk/by-id/dm-uuid-LVM-Se1805vbwYqSzX2KEfSWPZ9PqdWcQtMcfhaRcHV0oE9j814Nj97Af4vjRbCEYaYN
S: disk/by-uuid/fc046ad7-b258-4e7e-b12a-7293993c81b0
S: disk/by-label/ocfs2
S: gfsapp/gfs
E: UDEV_LOG=3
E: DEVPATH=/devices/virtual/block/dm-0
E: MAJOR=251
E: MINOR=0
E: DEVNAME=/dev/mapper/gfsapp-gfs
E: DEVTYPE=disk
E: SUBSYSTEM=block
E: DM_NAME=gfsapp-gfs
E: DM_UUID=LVM-Se1805vbwYqSzX2KEfSWPZ9PqdWcQtMcfhaRcHV0oE9j814Nj97Af4vjRbCEYaYN
E: DM_SUSPENDED=0
E: DM_UDEV_RULES=1
E: DM_VG_NAME=gfsapp
E: DM_LV_NAME=gfs
E: DEVLINKS=/dev/block/251:0 /dev/dm-0 /dev/disk/by-id/dm-name-gfsapp-gfs 
/dev/disk/by-id/dm-uuid-LVM-Se1805vbwYqSzX2KEfSWPZ9PqdWcQtMcfhaRcHV0oE9j814Nj97Af4vjRbCEYaYN
 /dev/disk/by-uuid/fc046ad7-b258-4e7e-b12a-7293993c81b0 
/dev/disk/by-label/ocfs2 /dev/gfsapp/gfs
E: ID_FS_LABEL=ocfs2
E: ID_FS_LABEL_ENC=ocfs2
E: ID_FS_UUID=fc046ad7-b258-4e7e-b12a-7293993c81b0
E: ID_FS_UUID_ENC=fc046ad7-b258-4e7e-b12a-7293993c81b0
E: ID_FS_VERSION=0.90
E: ID_FS_TYPE=ocfs2
E: ID_FS_USAGE=filesystem
E: FSTAB_NAME=/dev/gfsapp/gfs
E: FSTAB_DIR=/mnt/gfs
E: FSTAB_TYPE=ocfs2
E: FSTAB_OPTS=_netdev,noauto
E: FSTAB_FREQ=0
E: FSTAB_PASSNO=0
E: DM_TABLE_STATE=LIVE
E: DM_STATE=ACTIVE
E: DM_TYPE=raid

r...@db1:~# udevadm test /devices/virtual/block/dm-0
run_command: calling: test
udevadm_test: version 151
This program is for debugging only, it does not run any program,
specified by a RUN key. It may show incorrect results, because
some values may be different, or not available at a simulation run.

parse_file: reading '/lib/udev/rules.d/40-fuse-utils.rules' as rules file
parse_file: reading '/lib/udev/rules.d/40-gnupg.rules' as rules file
parse_file: reading '/lib/udev/rules.d/40-ia64.rules' as rules file
parse_file: reading '/lib/udev/rules.d/40-infiniband.rules' as rules file
parse_file: reading '/lib/udev/rules.d/40-isdn.rules' as rules file
parse_file: reading '/lib/udev/rules.d/40-pilot-links.rules' as rules file
parse_file: reading '/lib/udev/rules.d/40-ppc.rules' as rules file
parse_file: reading '/lib/udev/rules.d/40-zaptel.rules' as rules file
parse_file: reading '/lib/udev/rules.d/45-fuse.rules' as rules file
parse_file: reading '/lib/udev/rules.d/50-firmware.rules' as rules file
parse_file: reading '/lib/udev/rules.d/50-udev-default.rules' as rules file
parse_file: reading '/lib/udev/rules.d/55-dm.rules' as rules file
parse_file: reading '/lib/udev/rules.d/56-lvm.rules' as rules file
parse_file: reading '/lib/udev/rules.d/60-cdrom_id.rules' as rules file
parse_file: reading '/lib/udev/rules.d/60-floppy.rules' as rules file
parse_file: reading '/lib/udev/rules.d/60-persistent-alsa.rules' as rules file
parse_file: reading '/lib/udev/rules.d/60-persistent-input.rules' as rules file
parse_file: reading '/lib/udev/rules.d/60-persistent-serial.rules' as rules file
parse_file: reading '/lib/udev/rules.d/60-persistent-storage-dm.rules' as rules 
file
parse_file: reading '/lib/udev/rules.d/60-persistent-storage-lvm.rules' as 
rules file
parse_file: reading '/lib/udev/rules.d/60-persistent-storage-tape.rules' as 
rules file
parse_file: reading '/lib/udev/rules.d/60-persistent-storage.rules' as rules 
file
parse_file: reading '/lib/udev/rules.d/60-persistent-v4l.rules' as rules file
parse_file: reading '/lib/udev/rules.d/61-mobile-action.rules' as rules file
parse_file: reading '/lib/udev/rules.d/61-option-modem-modeswitch.rules' as 
rules file
parse_file: reading '/lib/udev/rules.d/61-persistent-storage-edd.rules' as 
rules file
parse_file: reading '/lib/udev/rules.d/64-device-mapper.rules' as rules file
parse_file: reading '/lib/udev/rules.d/70-acl.rules' as rules file
parse_file: reading '/lib/udev/rules.d/70-hid2hci.rules' as rules file
parse_file: reading '/etc/udev/rules.d/70-persistent-cd.rules' as rules file
parse_file: reading '/etc/udev/rules.d/70-persistent-net.rules' as rules file
parse_file: reading '/lib/udev/rules.d/75-cd-aliases-generator.rules' as rules 
file
parse_file: reading '/lib/udev/rules.d/75-net-description.rules' as rules file
parse_file: reading '/lib/udev/rules.d/75-persistent-net-generator.rules' as 
rules file
parse_file: reading '/lib/udev/rules.d/75-tty-description.rules' as rules file
parse_file: reading '/lib/udev/rules.d/78-graphics-card.rules' as rules file
parse_file: reading '/lib/udev/rules.d/78-sound-card.rules' as rules file
parse_file: reading '/lib/udev/rules.d/79-fstab_import.rules' as rules file
parse_file: reading '/lib/udev/rules.d/80-drivers.rules' as rules file
parse_file: reading '/lib/udev/rules.d/85-console-setup.rules' as rules file
parse_file: reading '/lib/udev/rules.d/85-hdparm.rules' as rules file
parse_file: reading '/lib/udev/rules.d/85-lvm2.rules' as rules file
parse_file: reading '/lib/udev/rules.d/85-regulatory.rules' as rules file
parse_file: reading '/lib/udev/rules.d/95-keyboard-force-release.rules' as 
rules file
parse_file: reading '/lib/udev/rules.d/95-keymap.rules' as rules file
parse_file: reading '/lib/udev/rules.d/95-kpartx.rules' as rules file
parse_file: reading '/lib/udev/rules.d/95-multipath.rules' as rules file
parse_file: reading '/lib/udev/rules.d/95-udev-late.rules' as rules file
parse_file: reading '/dev/.udev/rules.d/root.rules' as rules file
udev_rules_new: rules use 24204 bytes tokens (2017 * 12 bytes), 15657 bytes 
buffer
udev_rules_new: temporary index used 16140 bytes (807 * 20 bytes)
udev_device_new_from_syspath: device 0x7f6d4dde1620 has devpath 
'/devices/virtual/block/dm-0'
udev_device_new_from_syspath: device 0x7f6d4ddcf170 has devpath 
'/devices/virtual/block/dm-0'
udev_device_read_db: device 0x7f6d4ddcf170 filled with db file data
udev_device_read_db: device 0x7f6d4ddcf170 filled with db file data
udev_rules_apply_to_event: LINK 'block/251:0' 
/lib/udev/rules.d/50-udev-default.rules:3
udev_rules_apply_to_event: GROUP 6 /lib/udev/rules.d/50-udev-default.rules:77
udev_rules_apply_to_event: NAME 'mapper/gfsapp-gfs' 
/lib/udev/rules.d/55-dm.rules:42
udev_rules_apply_to_event: LINK 'dm-0' /lib/udev/rules.d/55-dm.rules:42
udev_rules_apply_to_event: IMPORT '/sbin/dmsetup splitname --nameprefixes 
--noheadings --rows gfsapp-gfs' /lib/udev/rules.d/56-lvm.rules:8
util_run_program: '/sbin/dmsetup splitname --nameprefixes --noheadings --rows 
gfsapp-gfs' started
util_run_program: '/sbin/dmsetup' (stdout) 'DM_VG_NAME='gfsapp''
util_run_program: '/sbin/dmsetup' (stdout) 'DM_LV_NAME='gfs''
util_run_program: '/sbin/dmsetup' (stdout) 'DM_LV_LAYER='''
util_run_program: '/sbin/dmsetup splitname --nameprefixes --noheadings --rows 
gfsapp-gfs' returned with exitcode 0
udev_rules_apply_to_event: LINK 'disk/by-id/dm-name-gfsapp-gfs' 
/lib/udev/rules.d/60-persistent-storage-dm.rules:9
udev_rules_apply_to_event: LINK 
'disk/by-id/dm-uuid-LVM-Se1805vbwYqSzX2KEfSWPZ9PqdWcQtMcfhaRcHV0oE9j814Nj97Af4vjRbCEYaYN'
 /lib/udev/rules.d/60-persistent-storage-dm.rules:10
udev_rules_apply_to_event: IMPORT '/sbin/blkid -o udev -p /dev/block/251:0' 
/lib/udev/rules.d/60-persistent-storage-dm.rules:15
util_run_program: '/sbin/blkid -o udev -p /dev/block/251:0' started
util_run_program: '/sbin/blkid' (stdout) 'ID_FS_LABEL=ocfs2'
util_run_program: '/sbin/blkid' (stdout) 'ID_FS_LABEL_ENC=ocfs2'
util_run_program: '/sbin/blkid' (stdout) 
'ID_FS_UUID=fc046ad7-b258-4e7e-b12a-7293993c81b0'
util_run_program: '/sbin/blkid' (stdout) 
'ID_FS_UUID_ENC=fc046ad7-b258-4e7e-b12a-7293993c81b0'
util_run_program: '/sbin/blkid' (stdout) 'ID_FS_VERSION=0.90'
util_run_program: '/sbin/blkid' (stdout) 'ID_FS_TYPE=ocfs2'
util_run_program: '/sbin/blkid' (stdout) 'ID_FS_USAGE=filesystem'
util_run_program: '/sbin/blkid -o udev -p /dev/block/251:0' returned with 
exitcode 0
udev_rules_apply_to_event: LINK 
'disk/by-uuid/fc046ad7-b258-4e7e-b12a-7293993c81b0' 
/lib/udev/rules.d/60-persistent-storage-dm.rules:16
udev_rules_apply_to_event: LINK 'disk/by-label/ocfs2' 
/lib/udev/rules.d/60-persistent-storage-dm.rules:17
udev_rules_apply_to_event: LINK 'gfsapp/gfs' 
/lib/udev/rules.d/60-persistent-storage-lvm.rules:9
udev_rules_apply_to_event: IMPORT 'fstab_import mapper/gfsapp-gfs block/251:0 
dm-0 disk/by-id/dm-name-gfsapp-gfs 
disk/by-id/dm-uuid-LVM-Se1805vbwYqSzX2KEfSWPZ9PqdWcQtMcfhaRcHV0oE9j814Nj97Af4vjRbCEYaYN
 disk/by-uuid/fc046ad7-b258-4e7e-b12a-7293993c81b0 disk/by-label/ocfs2 
gfsapp/gfs mapper/gfsapp-gfs' /lib/udev/rules.d/79-fstab_import.rules:1
util_run_program: 'fstab_import mapper/gfsapp-gfs block/251:0 dm-0 
disk/by-id/dm-name-gfsapp-gfs 
disk/by-id/dm-uuid-LVM-Se1805vbwYqSzX2KEfSWPZ9PqdWcQtMcfhaRcHV0oE9j814Nj97Af4vjRbCEYaYN
 disk/by-uuid/fc046ad7-b258-4e7e-b12a-7293993c81b0 disk/by-label/ocfs2 
gfsapp/gfs mapper/gfsapp-gfs' started
util_run_program: '/lib/udev/fstab_import' (stdout) 'FSTAB_NAME=/dev/gfsapp/gfs'
util_run_program: '/lib/udev/fstab_import' (stdout) 'FSTAB_DIR=/mnt/gfs'
util_run_program: '/lib/udev/fstab_import' (stdout) 'FSTAB_TYPE=ocfs2'
util_run_program: '/lib/udev/fstab_import' (stdout) 'FSTAB_OPTS=_netdev,noauto'
util_run_program: '/lib/udev/fstab_import' (stdout) 'FSTAB_FREQ=0'
util_run_program: '/lib/udev/fstab_import' (stdout) 'FSTAB_PASSNO=0'
util_run_program: 'fstab_import mapper/gfsapp-gfs block/251:0 dm-0 
disk/by-id/dm-name-gfsapp-gfs 
disk/by-id/dm-uuid-LVM-Se1805vbwYqSzX2KEfSWPZ9PqdWcQtMcfhaRcHV0oE9j814Nj97Af4vjRbCEYaYN
 disk/by-uuid/fc046ad7-b258-4e7e-b12a-7293993c81b0 disk/by-label/ocfs2 
gfsapp/gfs mapper/gfsapp-gfs' returned with exitcode 0
udev_rules_apply_to_event: RUN '/sbin/modprobe -Qba dm-multipath' 
/lib/udev/rules.d/95-kpartx.rules:10
udev_rules_apply_to_event: IMPORT '/lib/udev/dmsetup_env 251 0' 
/lib/udev/rules.d/95-kpartx.rules:17
util_run_program: '/lib/udev/dmsetup_env 251 0' started
util_run_program: '/lib/udev/dmsetup_env' (stdout) 
'DM_UUID=LVM-Se1805vbwYqSzX2KEfSWPZ9PqdWcQtMcfhaRcHV0oE9j814Nj97Af4vjRbCEYaYN'
util_run_program: '/lib/udev/dmsetup_env' (stdout) 'DM_TABLE_STATE=LIVE'
util_run_program: '/lib/udev/dmsetup_env' (stdout) 'DM_STATE=ACTIVE'
util_run_program: '/lib/udev/dmsetup_env' (stdout) 'DM_NAME=gfsapp-gfs'
util_run_program: '/lib/udev/dmsetup_env 251 0' returned with exitcode 0
udev_rules_apply_to_event: IMPORT 'kpartx_id 251 0 
LVM-Se1805vbwYqSzX2KEfSWPZ9PqdWcQtMcfhaRcHV0oE9j814Nj97Af4vjRbCEYaYN' 
/lib/udev/rules.d/95-kpartx.rules:21
util_run_program: 'kpartx_id 251 0 
LVM-Se1805vbwYqSzX2KEfSWPZ9PqdWcQtMcfhaRcHV0oE9j814Nj97Af4vjRbCEYaYN' started
util_run_program: '/lib/udev/kpartx_id' (stdout) 'DM_TYPE=raid'
util_run_program: 'kpartx_id 251 0 
LVM-Se1805vbwYqSzX2KEfSWPZ9PqdWcQtMcfhaRcHV0oE9j814Nj97Af4vjRbCEYaYN' returned 
with exitcode 0
udev_rules_apply_to_event: RUN 'socket:/org/kernel/dm/multipath_event' 
/lib/udev/rules.d/95-multipath.rules:7
udev_rules_apply_to_event: RUN '/sbin/multipath -v0 /dev/%k' 
/lib/udev/rules.d/95-multipath.rules:11
udev_device_update_db: created db file for '/devices/virtual/block/dm-0' in 
'/dev/.udev/db/block:dm-0'
udev_node_add: creating device node '/dev/mapper/gfsapp-gfs', devnum=251:0, 
mode=0660, uid=0, gid=6
udev_node_mknod: preserve file '/dev/mapper/gfsapp-gfs', because it has correct 
dev_t
node_symlink: preserve already existing symlink '/dev/block/251:0' to 
'../mapper/gfsapp-gfs'
link_find_prioritized: found '/sys/devices/virtual/block/dm-0' claiming 
'/dev/.udev/links/dm-0'
link_update: creating link '/dev/dm-0' to '/dev/mapper/gfsapp-gfs'
node_symlink: creating symlink '/dev/dm-0' to 'mapper/gfsapp-gfs'
link_find_prioritized: found '/sys/devices/virtual/block/dm-0' claiming 
'/dev/.udev/links/disk\x2fby-id\x2fdm-name-gfsapp-gfs'
link_update: creating link '/dev/disk/by-id/dm-name-gfsapp-gfs' to 
'/dev/mapper/gfsapp-gfs'
node_symlink: preserve already existing symlink 
'/dev/disk/by-id/dm-name-gfsapp-gfs' to '../../mapper/gfsapp-gfs'
link_find_prioritized: found '/sys/devices/virtual/block/dm-0' claiming 
'/dev/.udev/links/disk\x2fby-id\x2fdm-uuid-LVM-Se1805vbwYqSzX2KEfSWPZ9PqdWcQtMcfhaRcHV0oE9j814Nj97Af4vjRbCEYaYN'
link_update: creating link 
'/dev/disk/by-id/dm-uuid-LVM-Se1805vbwYqSzX2KEfSWPZ9PqdWcQtMcfhaRcHV0oE9j814Nj97Af4vjRbCEYaYN'
 to '/dev/mapper/gfsapp-gfs'
node_symlink: preserve already existing symlink 
'/dev/disk/by-id/dm-uuid-LVM-Se1805vbwYqSzX2KEfSWPZ9PqdWcQtMcfhaRcHV0oE9j814Nj97Af4vjRbCEYaYN'
 to '../../mapper/gfsapp-gfs'
link_find_prioritized: found '/sys/devices/virtual/block/dm-0' claiming 
'/dev/.udev/links/disk\x2fby-uuid\x2ffc046ad7-b258-4e7e-b12a-7293993c81b0'
link_update: creating link 
'/dev/disk/by-uuid/fc046ad7-b258-4e7e-b12a-7293993c81b0' to 
'/dev/mapper/gfsapp-gfs'
node_symlink: preserve already existing symlink 
'/dev/disk/by-uuid/fc046ad7-b258-4e7e-b12a-7293993c81b0' to 
'../../mapper/gfsapp-gfs'
link_find_prioritized: found '/sys/devices/virtual/block/dm-0' claiming 
'/dev/.udev/links/disk\x2fby-label\x2focfs2'
link_find_prioritized: found '/sys/devices/virtual/block/dm-1' claiming 
'/dev/.udev/links/disk\x2fby-label\x2focfs2'
udev_device_new_from_syspath: device 0x7f6d4ddd5930 has devpath 
'/devices/virtual/block/dm-1'
udev_device_read_db: device 0x7f6d4ddd5930 filled with db file data
link_update: creating link '/dev/disk/by-label/ocfs2' to 
'/dev/mapper/gfsapp-gfs'
node_symlink: preserve already existing symlink '/dev/disk/by-label/ocfs2' to 
'../../mapper/gfsapp-gfs'
link_find_prioritized: found '/sys/devices/virtual/block/dm-0' claiming 
'/dev/.udev/links/gfsapp\x2fgfs'
link_update: creating link '/dev/gfsapp/gfs' to '/dev/mapper/gfsapp-gfs'
node_symlink: preserve already existing symlink '/dev/gfsapp/gfs' to 
'../mapper/gfsapp-gfs'
udev_event_execute_rules: removed kernel created node '/dev/dm-0'
udevadm_test: UDEV_LOG=6
udevadm_test: DEVPATH=/devices/virtual/block/dm-0
udevadm_test: MAJOR=251
udevadm_test: MINOR=0
udevadm_test: DEVNAME=/dev/mapper/gfsapp-gfs
udevadm_test: DEVTYPE=disk
udevadm_test: ACTION=add
udevadm_test: SUBSYSTEM=block
udevadm_test: DEVLINKS=/dev/block/251:0 /dev/dm-0 
/dev/disk/by-id/dm-name-gfsapp-gfs 
/dev/disk/by-id/dm-uuid-LVM-Se1805vbwYqSzX2KEfSWPZ9PqdWcQtMcfhaRcHV0oE9j814Nj97Af4vjRbCEYaYN
 /dev/disk/by-uuid/fc046ad7-b258-4e7e-b12a-7293993c81b0 
/dev/disk/by-label/ocfs2 /dev/gfsapp/gfs
udevadm_test: DM_NAME=gfsapp-gfs
udevadm_test: 
DM_UUID=LVM-Se1805vbwYqSzX2KEfSWPZ9PqdWcQtMcfhaRcHV0oE9j814Nj97Af4vjRbCEYaYN
udevadm_test: DM_SUSPENDED=0
udevadm_test: DM_UDEV_RULES=1
udevadm_test: DM_VG_NAME=gfsapp
udevadm_test: DM_LV_NAME=gfs
udevadm_test: DM_LV_LAYER=
udevadm_test: ID_FS_LABEL=ocfs2
udevadm_test: ID_FS_LABEL_ENC=ocfs2
udevadm_test: ID_FS_UUID=fc046ad7-b258-4e7e-b12a-7293993c81b0
udevadm_test: ID_FS_UUID_ENC=fc046ad7-b258-4e7e-b12a-7293993c81b0
udevadm_test: ID_FS_VERSION=0.90
udevadm_test: ID_FS_TYPE=ocfs2
udevadm_test: ID_FS_USAGE=filesystem
udevadm_test: FSTAB_NAME=/dev/gfsapp/gfs
udevadm_test: FSTAB_DIR=/mnt/gfs
udevadm_test: FSTAB_TYPE=ocfs2
udevadm_test: FSTAB_OPTS=_netdev,noauto
udevadm_test: FSTAB_FREQ=0
udevadm_test: FSTAB_PASSNO=0
udevadm_test: DM_TABLE_STATE=LIVE
udevadm_test: DM_STATE=ACTIVE
udevadm_test: DM_TYPE=raid
udevadm_test: run: '/sbin/modprobe -Qba dm-multipath'
udevadm_test: run: 'socket:/org/kernel/dm/multipath_event'
udevadm_test: run: '/sbin/multipath -v0 /dev/dm-0'

Udevadm info and udevadm test print that udev should make a link with
the name /dev/dm-0 to /dev/mapper/gfs-gfsapp, which is the ocfs
filesystem device name created by udev. At this point I created the link
and tried to use command ocfs2_hb_ctl -K to stop ocfs heartbeat and then
o2cb service.

r...@db1:~# ln -s /dev/mapper/gfsapp-gfs /dev/dm-0
r...@db1:~# ocfs2_hb_ctl -K -u FC046AD7B2584E7EB12A7293993C81B0
r...@db1:~# ocfs2_hb_ctl -I -u FC046AD7B2584E7EB12A7293993C81B0
FC046AD7B2584E7EB12A7293993C81B0: 1 refs
r...@db1:~# ocfs2_hb_ctl -K -u FC046AD7B2584E7EB12A7293993C81B0
r...@db1:~# ocfs2_hb_ctl -I -u FC046AD7B2584E7EB12A7293993C81B0
FC046AD7B2584E7EB12A7293993C81B0: 0 refs
r...@db1:~# /etc/init.d/o2cb stop
Cleaning heartbeat on ocfs2: OK
Stopping O2CB cluster ocfs2: OK
Unloading module "ocfs2": OK
Unmounting ocfs2_dlmfs filesystem: OK
Unloading module "ocfs2_dlmfs": OK
Unloading module "ocfs2_stack_o2cb": OK
Unmounting configfs filesystem: OK
Unloading module "configfs": OK

Now the o2cb service stops correctly. I checked again the start and stop
o2cb and mounting and unmounting the ocfs filesystem with the link
/dev/dm-0 present. The filesystem mounting removes the link and create a
reference.

r...@db1:~# ll /dev/dm-0 && /etc/init.d/o2cb start
lrwxrwxrwx 1 root root 22 2010-08-15 10:30 /dev/dm-0 -> /dev/mapper/gfsapp-gfs
Loading filesystem "configfs": OK
Mounting configfs filesystem at /sys/kernel/config: OK
Loading stack plugin "o2cb": OK
Loading filesystem "ocfs2_dlmfs": OK
Mounting ocfs2_dlmfs filesystem at /dlm: OK
Setting cluster stack "o2cb": OK
Starting O2CB cluster ocfs2: OK
r...@db1:~# ll /dev/dm-0 && mount -v -t ocfs2 /dev/gfsapp/gfs /mnt/gfs
lrwxrwxrwx 1 root root 22 2010-08-15 10:30 /dev/dm-0 -> /dev/mapper/gfsapp-gfs
device=/dev/mapper/gfsapp-gfs
/dev/mapper/gfsapp-gfs on /mnt/gfs type ocfs2 (rw,_netdev,heartbeat=local)
r...@db1:~# ll /dev/dm-0 ocfs2_hb_ctl -I -u FC046AD7B2584E7EB12A7293993C81B0
ls: can not access /dev/dm-0: Nessun file o directory
r...@db1:~# ocfs2_hb_ctl -I -u FC046AD7B2584E7EB12A7293993C81B0
FC046AD7B2584E7EB12A7293993C81B0: 1 refs

If I recreate the link the umonting cancel correctly the reference.

r...@db1:~# ln -s /dev/mapper/gfsapp-gfs /dev/dm-0
r...@db1:~# ll /dev/dm-0 && umount -v /mnt/gfs
lrwxrwxrwx 1 root root 22 2010-08-15 10:36 /dev/dm-0 -> /dev/mapper/gfsapp-gfs
eseguito umount di /dev/mapper/gfsapp-gfs
r...@db1:~# ll /dev/dm-0 && ocfs2_hb_ctl -I -u FC046AD7B2584E7EB12A7293993C81B0
lrwxrwxrwx 1 root root 22 2010-08-15 10:36 /dev/dm-0 -> /dev/mapper/gfsapp-gfs
FC046AD7B2584E7EB12A7293993C81B0: 0 refs
r...@db1:~# ll /dev/dm-0 && /etc/init.d/o2cb stop
lrwxrwxrwx 1 root root 22 2010-08-15 10:36 /dev/dm-0 -> /dev/mapper/gfsapp-gfs
Cleaning heartbeat on ocfs2: OK
Stopping O2CB cluster ocfs2: OK
Unloading module "ocfs2": OK
Unmounting ocfs2_dlmfs filesystem: OK
Unloading module "ocfs2_dlmfs": OK
Unloading module "ocfs2_stack_o2cb": OK
Unmounting configfs filesystem: OK
Unloading module "configfs": OK

At this point I do not know if the bug is in udev that not create the
link /dev/dm-0 or in ocfs that is unable to determine the name of the
ocfs filesystem device without this link.

-- 
o2cb stopping Failed
https://bugs.launchpad.net/bugs/613793
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