fix(partitioning): set btrfs default subvolume and restrict @pkg to Arch

roles/partitioning/tasks/_mount.yml

@@ -9,12 +9,13 @@
         - >-
           system_cfg.features.cis.enabled | bool or (
             not (system_cfg.features.cis.enabled | bool) and (
-              (system_cfg.filesystem == 'btrfs' and item.path in ['/home', '/var/log', '/var/cache/pacman/pkg'])
+              (system_cfg.filesystem == 'btrfs' and item.path in ['/home', '/var/log']
+               + (['/var/cache/pacman/pkg'] if os == 'archlinux' else []))
               or (item.path not in ['/home', '/var', '/var/log', '/var/log/audit', '/var/cache/pacman/pkg'])
             )
           )
         - >-
-          not (item.path in ['/swap', '/var/cache/pacman/pkg'] and system_cfg.filesystem != 'btrfs')
+          not (item.path in ['/swap', '/var/cache/pacman/pkg'] and (system_cfg.filesystem != 'btrfs' or os != 'archlinux'))
         - system_cfg.features.swap.enabled | bool or item.path != '/swap'
       ansible.posix.mount:
         path: /mnt{{ item.path }}

roles/partitioning/tasks/btrfs.yml

@@ -43,6 +43,7 @@
       when:
         - system_cfg.features.cis.enabled | bool or item.subvol not in ['var_log_audit']
         - system_cfg.features.swap.enabled | bool or item.subvol != 'swap'
+        - item.os is not defined or os in item.os
       ansible.builtin.command: btrfs su cr /mnt/{{ '@' if item.subvol == 'root' else '@' + item.subvol }}
       args:
         creates: /mnt/{{ '@' if item.subvol == 'root' else '@' + item.subvol }}
@@ -51,12 +52,19 @@
         - { subvol: swap }
         - { subvol: home }
         - { subvol: var }
-        - { subvol: pkg }
+        - { subvol: pkg, os: [archlinux] }
         - { subvol: var_log }
         - { subvol: var_log_audit }
       loop_control:
         label: "{{ item.subvol }}"
 
+    - name: Set default btrfs subvolume to @
+      ansible.builtin.shell: >-
+        btrfs subvolume list /mnt | awk '/ path @$/ {print $2}'
+        | xargs -I{} btrfs subvolume set-default {} /mnt
+      register: partitioning_btrfs_default_result
+      changed_when: partitioning_btrfs_default_result.rc == 0
+
     - name: Set quotas for subvolumes
       when: system_cfg.features.cis.enabled | bool
       ansible.builtin.command: btrfs qgroup limit {{ item.quota }} /mnt/{{ '@' if item.subvol == 'root' else '@' + item.subvol }}