BCACHE_DEV_UNLINK_DONE
clear_bit(BCACHE_DEV_UNLINK_DONE, &dc->disk.flags);
if (d->c && !test_and_set_bit(BCACHE_DEV_UNLINK_DONE, &d->flags)) {
clear_bit(BCACHE_DEV_UNLINK_DONE, &d->flags);