BTRFS_FS_STATE_DEV_REPLACING
if (likely(!test_bit(BTRFS_FS_STATE_DEV_REPLACING,
!test_bit(BTRFS_FS_STATE_DEV_REPLACING,
set_bit(BTRFS_FS_STATE_DEV_REPLACING, &fs_info->fs_state);
clear_bit(BTRFS_FS_STATE_DEV_REPLACING, &fs_info->fs_state);
[BTRFS_FS_STATE_DEV_REPLACING] = 'R',