BLOCK_GROUP_ITEM=192 BlockGroup
CHUNK_ITEM=228 Chunk
DEV_ITEM=216 Dev
DEV_EXTENT=204 DevExtent
DIR_ITEM=84, DirList
DIR_INDEX=96, DirList
XATTR_ITEM=24 DirList
UNTYPED=0, Empty
TREE_BLOCK_REF=176, Empty
SHARED_BLOCK_REF=182, Empty
QGROUP_RELATION=246 Empty
EXTENT_ITEM=168 Extent
EXTENT_DATA_REF=178 ExtentDataRef
INODE_ITEM=1 Inode
INODE_REF=12 InodeRefList
METADATA_ITEM=169 Metadata
ORPHAN_ITEM=48 Orphan
PERSISTENT_ITEM=249 DevStats
ROOT_ITEM=132 Root
SHARED_DATA_REF=184 SharedDataRef
UUID_SUBVOL=251 UUIDMap
UUID_RECEIVED_SUBVOL=252 UUIDMap