Kihwal Lee created HDFS-4972:
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Summary: [branch-0.23] permission check and operation are done in
a separate lock for getBlockLocations()
Key: HDFS-4972
URL: https://issues.apache.org/jira/browse/HDFS-4972
Project: Hadoop HDFS
Issue Type: Bug
Components: namenode
Affects Versions: 0.23.8
Reporter: Kihwal Lee
Assignee: Kihwal Lee
For getBlockLocations() call, the read lock is acquired when doing permission
check. But unlike other namenode methods, this is outside of the lock of the
actual operation. So it ends up acquiring and releasing the lock twice. This
has two implications.
- permissions can change in between the locks
- the lock fairness will penalize getBlockLocations().
This was fixed in trunk and branch-2 as a part of HDFS-4679, but not in
branch-0.23.
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