Description of problem:

We need to backport Upstream PR https://github.com/rear/rear/pull/2194 to our ReaR-2.4 to fix an issue when recovering a system in Migration Mode (happens when a different system is used or disks have not same size) or when Thin Pools are used.
Without the fix, multiple "lvmvol" lines for same LV are added in disklayout.conf, causing multiple "lvcreate" commands for same LV to be used, which breaks the recovery.


Version-Release number of selected component (if applicable):

rear-2.4


How reproducible:

Always


Steps to Reproduce:

1. Add 2 disks to an existing system (to enable creating stripes)

2. Create a VG with the disks

# vgcreate data /dev/sdb /dev/sdc

3. Create 2 LVs with segments

# lvcreate -n lv1 -L 1G data
# lvcreate -n lv2 -L 1G data
# lvextend /dev/data/lv1 -L +1G -i 2
# lvextend /dev/data/lv2 -L +1G -i 2
# lvextend /dev/data/lv1 -L +1G -i 1
# lvextend /dev/data/lv2 -L +1G -i 1

4. Format and mount the LVs

# mkdir -p /lv1 /lv2
# mkfs.ext4 /dev/data/lv1
# mkfs.ext4 /dev/data/lv2
# mount /dev/data/lv1 /lv1
# mount /dev/data/lv2 /lv2

5. Create rescue ISO

# rear mkrescue

6. Check /var/lib/rear/layout/disklayout.conf


Actual results:

(broken)
# lvmvol <volume_group> <name> <size(bytes)> <layout> [key:value ...]
lvmvol /dev/data lv1 3221225472b linear,striped stripes:1
lvmvol /dev/data lv1 3221225472b linear,striped stripesize:65536b stripes:2
lvmvol /dev/data lv1 3221225472b linear,striped stripes:1
lvmvol /dev/data lv2 2147483648b linear,striped stripes:1
lvmvol /dev/data lv2 2147483648b linear,striped stripesize:65536b stripes:2


Expected results:

(with the fix)
# lvmvol <volume_group> <name> <size(bytes)> <layout> [key:value ...]
# WARNING: Volume data/lv1 has multiple segments. Restoring it in Migration Mode using 'lvcreate' won't preserve segments and volume properties of the other segments!
lvmvol /dev/data lv1 3221225472b linear,striped segmentsize:1073741824b stripes:1
#lvmvol /dev/data lv1 3221225472b linear,striped stripesize:65536b segmentsize:1073741824b stripes:2
#lvmvol /dev/data lv1 3221225472b linear,striped segmentsize:1073741824b stripes:1
# WARNING: Volume data/lv2 has multiple segments. Restoring it in Migration Mode using 'lvcreate' won't preserve segments and volume properties of the other segments!
lvmvol /dev/data lv2 2147483648b linear,striped segmentsize:1073741824b stripes:1
#lvmvol /dev/data lv2 2147483648b linear,striped stripesize:65536b segmentsize:1073741824b stripes:2


Additional info:

When in Migration Mode or when recreating Thin Pools, the LV will be recreated using one segment only, which characteristics (e.g. "stripes") of the first segment only.
This is sub-optimal but too complicated to do differently.