postgres: Try to keep nocow on btrfs

roles/postgres/files/upgrade_pg.sh

@@ -34,6 +34,7 @@ pacman -S --needed postgresql-old-upgrade
 chown postgres:postgres /var/lib/postgres/
 su - postgres -c "mv /var/lib/postgres/data /var/lib/postgres/data-$FROM_VERSION"
 su - postgres -c 'mkdir /var/lib/postgres/data'
+su - postgres -c 'chattr -f +C /var/lib/postgres/data' || :
 su - postgres -c 'initdb --locale en_US.UTF-8 -E UTF8 -D /var/lib/postgres/data'
 vimdiff /var/lib/postgres/{data,data-$FROM_VERSION}/pg_hba.conf
 vimdiff /var/lib/postgres/{data,data-$FROM_VERSION}/postgresql.conf

roles/postgres/tasks/main.yml

@@ -9,6 +9,15 @@
 - name: install postgres
   pacman: name=postgresql,python-psycopg2 state=present
 
+- name: create nocow database directory
+  file:
+    state: directory
+    owner: postgres
+    group: postgres
+    attributes: "+C"
+    path: /var/lib/postgres/data
+  when: filesystem == "btrfs"
+
 - name: initialize postgres
   become: yes
   become_user: postgres