/btrfs/system/@root is not a btrfs mountpoint

[kaotika]

I use a folder /btrfs/system to mount my btrfs root. Inside /btrfs/system I place snapshots inside /btrfs/system/snapshots.

tree -d -L 1 /btrfs/system/
/btrfs/system/
├── @home
├── @root
├── snapshots

I'am using this structure for a few years now and never had problems with btrfs-snap until today.

Calling:

btrfs-snap -r -c -B /btrfs/system/snapshots /btrfs/system/@root root_daily 7

throws ERROR: /btrfs/system/@root is not a btrfs mountpoint (or old version of btrfs-tools, try > 0.19).

Changing btrfs subvolume show $mp | grep "${mp}$" > /dev/null to btrfs subvolume show $mp | grep $(basename $mp) > /dev/null fixes the issue.