Hi, systemd does remount ro at reboot/shutdown time, and if free space tree exists, this is always logged:
[ 27.476941] systemd-shutdown[1]: Unmounting file systems. [ 27.479756] [1601]: Remounting '/' read-only in with options 'seclabel,compress=zstd:1,space_cache=v2,subvolid=258,subvol=/root'. [ 27.489196] BTRFS info (device vda3): using free space tree [ 27.492009] BTRFS warning (device vda3): remount supports changing free space tree only from ro to rw Is there a way to better detect that this isn't an attempt to change to v2? If there's no v1 present, it's not a change. -- Chris Murphy
