Nicer use of variables.

Ansible/roles/debian_server/tasks/btrfs.yml

 ---
-- name: Find a mountpoint for {{ device }}
-  # There can be multiple once with bind mounts or subvolumes, we only need
-  # one.
-  set_fact:
-    # yamllint disable rule:line-length
-    btrfs_mountpoint: |-
-      {{ (ansible_facts.mounts|selectattr("device", "equalto", device)|first)["mount"] }}
-    # yamllint enable rule:line-length
-
 - name: Install btrfs packages
   apt:
     cache_valid_time: 3600
@@ -34,6 +25,10 @@
     src: btrfs_scrub.{{ item }}.j2
   vars: &vars
     name: '{{ device|replace("/", "_") }}'
+    # yamllint disable rule:line-length
+    mountpoint: |-
+      {{ (ansible_facts.mounts|selectattr("device", "equalto", device)|first)["mount"] }}
+    # yamllint enable rule:line-length
   tags: [scrub]
 
 - name: Enable btrfs scrub timers

Ansible/roles/debian_server/templates/btrfs_check.service.j2

@@ -6,4 +6,4 @@ After=network-online.target
 
 [Service]
 Type=exec
-ExecStart=mnpw --warn -- /usr/lib/nagios-btrfs/plugins/check_btrfs --mountpoint {{ btrfs_mountpoint }}
+ExecStart=mnpw --warn -- /usr/lib/nagios-btrfs/plugins/check_btrfs --mountpoint {{ mountpoint }}