Cannot extend LVM volume while active due to failed snapshot merge

This document (7018550) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Server 12
SUSE Linux Enterprise Server 11

Situation

Attempting to resize an LVM logical volume results in a warning.

sles:~ # lvs
  LV     VG   Attr      LSize  Pool Origin Data%  Move Log Copy%  Convert
  lvdata vg00 Owi-a-s-- 16.00g                                           

sles:~ # lvextend -L +1G vg00/lvdata
  Snapshot origin volumes can be resized only while inactive: try lvchange -an

However, the customer does not want deactivate the volume to resize it. The snapshot volume is missing from lvs output. Attempting to remove the snapshot volume results in the following error:

sles:~ # lvremove vg00/lvdata-snap
  Can't remove merging snapshot logical volume "lvdata-snap"

sles:~ # lvconvert --merge -i2 /dev/vg00/lvdata-snap
  Snapshot lvdata-snap is already merging
  Unable to merge LV "lvdata-snap" into its origin.

The origin LVM volume has been in an "(O)rigin with merging snapshot" state for several days and across several reboots.

sles11sp4:~ # mount /dev/vg00/lvdata-snap /mnt
mount: special device /dev/vg00/lvdata-snap does not exist

sles11sp4:~ # lvchange -ay vg00/lvdata-snap
Change of snapshot lvdata-snap will also change its origin lvdata. Proceed? [y/n]: y
  Unable to change internal LV lvdata-snap directly

The /etc/lvm/backup/vg00 file contains data like this:

vg00 {
        logical_volumes {
                lvdata {
                }
                lvdata-snap {
                }
                snapshot0 {
                }
        }
}

Resolution

1. Run vgcfgbackup
2. Make a backup copy of /etc/lvm/backup/vg00
3. Edit /etc/lvm/backup/vg00
4. Remove the lvdata-snap {} and snapshot0 {} sections associated with the snapshot. It should contain data like this (NOTE: Leave the content within the {} braces. This is just a short example of what major sections should remain in the file):

vg00 {
        logical_volumes {
                lvdata {
                }
        }
}

5. Save the file.
6. Run vgcfgrestore vg00

Cause

The snapshot merging process was interrupted before it could complete. For example, running lvconvert --merge -i2 vg00/lvdata-snap and then pressing Ctrl-C while it's running will cause this state.

Disclaimer

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