/* * Used to identify special blocks in snapshots: * * BLK_NOCOPY - A block that was unallocated at the time the snapshot * was taken, hence does not need to be copied when written. * BLK_SNAP - A block held by another snapshot that is not needed by this * snapshot. When the other snapshot is freed, the BLK_SNAP entries * are converted to BLK_NOCOPY. These are needed to allow fsck to * identify blocks that are in use by other snapshots (which are * expunged from this snapshot). */