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https://issues.apache.org/jira/browse/HDFS-6527?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14030657#comment-14030657
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Kihwal Lee commented on HDFS-6527:
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This bug has been there since 2.1.0-beta. It involves two client threads
creating and deleting the same file.
> Edit log corruption due to defered INode removal
> ------------------------------------------------
>
> Key: HDFS-6527
> URL: https://issues.apache.org/jira/browse/HDFS-6527
> Project: Hadoop HDFS
> Issue Type: Bug
> Affects Versions: 2.4.0
> Reporter: Kihwal Lee
> Assignee: Kihwal Lee
> Priority: Blocker
> Attachments: HDFS-6527.branch-2.4.patch, HDFS-6527.trunk.patch
>
>
> We have seen a SBN crashing with the following error:
> {panel}
> \[Edit log tailer\] ERROR namenode.FSEditLogLoader:
> Encountered exception on operation AddBlockOp
> [path=/xxx,
> penultimateBlock=NULL, lastBlock=blk_111_111, RpcClientId=,
> RpcCallId=-2]
> java.io.FileNotFoundException: File does not exist: /xxx
> {panel}
> This was caused by the deferred removal of deleted inodes from the inode map.
> Since startFile() acquires FSN read lock and then write lock, a deletion can
> happen in between. Because of deferred inode removal outside FSN write lock,
> startFile() can get the deleted inode from the inode map with FSN write lock
> held. This allow addition of a block to a deleted file.
> As a result, the edit log will contain OP_ADD, OP_DELETE, followed by
> OP_ADD_BLOCK. This cannot be replayed by NN, so NN doesn't start up or SBN
> crashes.
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