add -f flag for btrfs mkfs

diff --git a/src/ceph-disk b/src/ceph-disk
index bb819582c10a716bffd888369b5ef504989bc2a1..31ce22159c550b7a0f29b823de3aac67afc1e7ff 100755 (executable)
--- a/src/ceph-disk
+++ b/src/ceph-disk
@@ -134,6 +134,8 @@ MOUNT_OPTIONS = dict(
 
 MKFS_ARGS = dict(
     btrfs=[
+        # btrfs requires -f, for the same reason as xfs (see comment below)
+        '-f',
         '-m', 'single',
         '-l', '32768',
         '-n', '32768',