org.apache.hadoop.hdfs.server.common
Interfaces 
HdfsConstants
Storage.StorageDirType
Upgradeable
Classes 
GenerationStamp
JspHelper
Storage
StorageInfo
UpgradeManager
UpgradeObject
UpgradeObjectCollection
UpgradeStatusReport
Util
Enums 
HdfsConstants.BlockUCState
HdfsConstants.NamenodeRole
HdfsConstants.NodeType
HdfsConstants.ReplicaState
HdfsConstants.StartupOption
Storage.StorageState
Exceptions 
InconsistentFSStateException
IncorrectVersionException