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https://issues.apache.org/jira/browse/HDFS-12855?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16269303#comment-16269303
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Manoj Govindassamy commented on HDFS-12855:
-------------------------------------------
The latest trunk code is also similar to 2.7.x line.
{{NamenodeFsck.blockIdCK()}} works on BlockManager and FSNameSystem layer
directly without holding NameSystem locks. One race I can think of is fsck with
block id option running in parallel with a file deletion which contains the
same block. Since the BlockInfo is obtained without holding a lock, the file
could get deleted and later the INode retrieval could return null and could
face NPE when accessing INode members. Haven't proved this with a test yet
though.
{noformat}
public void blockIdCK(String blockId) {
...
try {
//get blockInfo
Block block = new Block(Block.getBlockId(blockId));
//find which file this block belongs to
BlockInfo blockInfo = blockManager.getStoredBlock(block);
if(blockInfo == null) {
out.println("Block "+ blockId +" " + NONEXISTENT_STATUS);
LOG.warn("Block "+ blockId + " " + NONEXISTENT_STATUS);
return;
}
final INodeFile iNode =
namenode.getNamesystem().getBlockCollection(blockInfo);
NumberReplicas numberReplicas= blockManager.countNodes(blockInfo);
out.println("Block Id: " + blockId);
out.println("Block belongs to: "+iNode.getFullPathName());
out.println("No. of Expected Replica: " +
blockManager.getExpectedRedundancyNum(blockInfo));
{noformat}
> Fsck violates namesystem locking
> ---------------------------------
>
> Key: HDFS-12855
> URL: https://issues.apache.org/jira/browse/HDFS-12855
> Project: Hadoop HDFS
> Issue Type: Bug
> Affects Versions: 2.7.4
> Reporter: Konstantin Shvachko
>
> {{NamenodeFsck}} access {{FSNamesystem}} structures, such as INodes,
> BlockInfo without holding a lock. See e.g. {{NamenodeFsck.blockIdCK()}}.
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