[HDFS-4648] For snapshot deletion, when merging the diff from to-delete snapshot to the prior snapshot, make sure files/directories created after the prior snapshot get deleted

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: Snapshot (HDFS-2802)
• Component/s: namenode
• Hadoop Flags: Reviewed
• Assignee: Jing Zhao
• Reporter: Jing Zhao
• Created: 29/Mar/13 02:19
• Updated: 31/Mar/13 17:43
• Resolved: 31/Mar/13 03:58

Description

When the following steps happen:
1. Take snapshot s1 on dir.
2. Create new dir and files under subDir, which is descendant of dir.
3. Take snapshot s2 on dir.
4. Delete subDir.
5. Delete snapshot s2.
When we merge the diff from s2 to s1 (since we deleted s2), we need to make
sure all the files/dirs created after s1 should be destroyed. Otherwise
if these files/dirs are saved to the fsimage, we will have FileNotFound Exception while loading fsimage.