BTRFS_FS_CLEANER_RUNNING
set_bit(BTRFS_FS_CLEANER_RUNNING, &fs_info->flags);
clear_and_wake_up_bit(BTRFS_FS_CLEANER_RUNNING, &fs_info->flags);
if (!test_bit(BTRFS_FS_CLEANER_RUNNING, &fs_info->flags))
wait_on_bit(&fs_info->flags, BTRFS_FS_CLEANER_RUNNING, TASK_UNINTERRUPTIBLE);