Branch-2802 Snapshot (Unreleased)

  HDFS-4076. Support snapshot of single files.  (szetszwo)

  HDFS-4082. Add editlog opcodes for snapshot create and delete operations.
  (suresh via szetszwo)

  HDFS-4086. Add editlog opcodes to allow and disallow snapshots on a 
  directory. (Brandon Li via suresh)

  HDFS-4083. Protocol changes for snapshots. (suresh)

  HDFS-4077. Add support for Snapshottable Directory. (szetszwo via suresh)

  HDFS-4087. Protocol changes for listSnapshots functionality.
  (Brandon Li via suresh)

  HDFS-4079. Add SnapshotManager which maintains a list for all the
  snapshottable directories and supports snapshot methods such as setting a
  directory to snapshottable and creating a snapshot.  (szetszwo)

  HDFS-4078. Handle replication in snapshots.  (szetszwo)

  HDFS-4084. Provide CLI support to allow and disallow snapshot 
  on a directory. (Brondon Li via suresh)

  HDFS-4091. Add snapshot quota to limit the number of snapshots allowed.
  (szetszwo)

  HDFS-4097. Provide CLI support for createSnapshot. (Brandon Li via suresh)

  HDFS-4092. Update file deletion logic for snapshot so that the current inode
  is removed from the circular linked list; and if some blocks at the end of the
  block list no longer belong to any other inode, collect them and update the
  block list.  (szetszwo)

  HDFS-4111. Support snapshot of subtrees. (szetszwo via suresh)

  HDFS-4119. Complete the allowSnapshot code and add a test for it. (szetszwo)

  HDFS-4133. Add testcases for testing basic snapshot functionalities.
  (Jing Zhao via suresh)

  HDFS-4116. Add auditlog for some snapshot operations. (Jing Zhao via suresh)

  HDFS-4095. Add some snapshot related metrics. (Jing Zhao via suresh)

  HDFS-4141. Support directory diff - the difference between the current state
  and a previous snapshot of an INodeDirectory. (szetszwo)

  HDFS-4146. Use getter and setter in INodeFileWithLink to access blocks and
  initialize root directory as snapshottable. (szetszwo)

  HDFS-4149. Implement the disallowSnapshot(..) in FSNamesystem and add
  resetSnapshottable(..) to SnapshotManager. (szetszwo)

  HDFS-4147. When there is a snapshot in a subtree, deletion of the subtree
  should fail. (Jing Zhao via szetszwo)

  HDFS-4150.  Update the inode in the block map when a snapshotted file or a
  snapshot file is deleted. (Jing Zhao via szetszwo)

  HDFS-4159. Rename should fail when the destination directory is snapshottable
  and has snapshots. (Jing Zhao via szetszwo)

  HDFS-4170. Add snapshot information to INodesInPath.  (szetszwo)

  HDFS-4177. Add a snapshot parameter to INodeDirectory.getChildrenList() for
  selecting particular snapshot children list views.  (szetszwo)

  HDFS-4148. Disallow write/modify operations on files and directories in a
  snapshot. (Brandon Li via suresh)

  HDFS-4188. Add Snapshot.ID_COMPARATOR for comparing IDs and fix a bug in
  ReadOnlyList.Util.binarySearch(..).  (szetszwo)

  HDFS-4187. Add tests for replication handling in snapshots. (Jing Zhao via
  szetszwo)

  HDFS-4196. Support renaming of snapshots. (Jing Zhao via szetszwo)

  HDFS-4175. Additional snapshot tests for more complicated directory
  structure and modifications. (Jing Zhao via suresh)

  HDFS-4293. Fix TestSnapshot failure. (Jing Zhao via suresh)

  HDFS-4317. Change INode and its subclasses to support HDFS-4103. (szetszwo)

  HDFS-4103. Support O(1) snapshot creation. (szetszwo)

  HDFS-4330. Support snapshots up to the snapshot limit. (szetszwo)

  HDFS-4357. Fix a bug that if an inode is replaced, further INode operations
  should apply to the new inode. (Jing Zhao via szetszwo)

  HDFS-4230. Support listing of all the snapshottable directories.  (Jing Zhao
  via szetszwo)

  HDFS-4244. Support snapshot deletion.  (Jing Zhao via szetszwo)

  HDFS-4245. Include snapshot related operations in TestOfflineEditsViewer.
  (Jing Zhao via szetszwo)

  HDFS-4395. In INodeDirectorySnapshottable's constructor, the passed-in dir
  could be an INodeDirectoryWithSnapshot.  (Jing Zhao via szetszwo)

  HDFS-4397. Fix a bug in INodeDirectoryWithSnapshot.Diff.combinePostDiff(..)
  that it may put the wrong node into the deleted list.  (szetszwo)

  HDFS-4407. Change INodeDirectoryWithSnapshot.Diff.combinePostDiff(..) to
  merge-sort like and keep the postDiff parameter unmodified.  (szetszwo)

  HDFS-4098. Add FileWithSnapshot, INodeFileUnderConstructionWithSnapshot and
  INodeFileUnderConstructionSnapshot for supporting append to snapshotted files.
  (szetszwo)

  HDFS-4126. Add reading/writing snapshot information to FSImage.
  (Jing Zhao via suresh)

  HDFS-4436. Change INode.recordModification(..) to return only the current
  inode and remove the updateCircularList parameter from some methods in
  INodeDirectoryWithSnapshot.Diff.  (szetszwo)

  HDFS-4429. When the latest snapshot exists, INodeFileUnderConstruction should
  be replaced with INodeFileWithSnapshot but not INodeFile.  (Jing Zhao
  via szetszwo)

  HDFS-4441. Move INodeDirectoryWithSnapshot.Diff and the related classes to a
  package.  (szetszwo)

  HDFS-4432. Support INodeFileUnderConstructionWithSnapshot in FSImage
  saving/loading. (Jing Zhao via suresh)

  HDFS-4131. Add capability to namenode to get snapshot diff. (Jing Zhao via
  suresh)

  HDFS-4447. Refactor INodeDirectoryWithSnapshot for supporting general INode
  diff lists.  (szetszwo)

  HDFS-4189. Renames the getMutableXxx methods to getXxx4Write and fix a bug
  that some getExistingPathINodes calls should be getINodesInPath4Write.
  (szetszwo)

  HDFS-4361. When listing snapshottable directories, only return those
  where the user has permission to take snapshots.  (Jing Zhao via szetszwo)

  HDFS-4464. Combine collectSubtreeBlocksAndClear with deleteDiffsForSnapshot
  and rename it to destroySubtreeAndCollectBlocks.  (szetszwo)

  HDFS-4414. Add support for getting snapshot diff from DistributedFileSystem.
  (Jing Zhao via suresh)

  HDFS-4446. Support file snapshots with diff lists.  (szetszwo)

  HDFS-4480. Eliminate the file snapshot circular linked list.  (szetszwo)