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https://issues.apache.org/jira/browse/HDFS-16785?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17610795#comment-17610795
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ASF GitHub Bot commented on HDFS-16785:
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Hexiaoqiao commented on PR #4945:
URL: https://github.com/apache/hadoop/pull/4945#issuecomment-1261758130
> 1、When fsVolume.getVolumeMap() scan the bock from disk to add block
metadata，it may add new block metadata when another thread add block.
Great point. +1 from my side. So volume level lock will be more proper?
> 2、How we deal conflict when remove BlockPool operating occur at same time.
Not sure if this is block issue. This improvement seems not involve global
meta management, only prepare phase here? So any conflict here?
> DataNode hold BP write lock to scan disk
> ----------------------------------------
>
> Key: HDFS-16785
> URL: https://issues.apache.org/jira/browse/HDFS-16785
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: ZanderXu
> Assignee: ZanderXu
> Priority: Major
> Labels: pull-request-available
>
> When patching the fine-grained locking of datanode, I found that `addVolume`
> will hold the write block of the BP lock to scan the new volume to get the
> blocks. If we try to add one full volume that was fixed offline before, i
> will hold the write lock for a long time.
> The related code as bellows:
> {code:java}
> for (final NamespaceInfo nsInfo : nsInfos) {
> String bpid = nsInfo.getBlockPoolID();
> try (AutoCloseDataSetLock l = lockManager.writeLock(LockLevel.BLOCK_POOl,
> bpid)) {
> fsVolume.addBlockPool(bpid, this.conf, this.timer);
> fsVolume.getVolumeMap(bpid, tempVolumeMap, ramDiskReplicaTracker);
> } catch (IOException e) {
> LOG.warn("Caught exception when adding " + fsVolume +
> ". Will throw later.", e);
> exceptions.add(e);
> }
> } {code}
> And I noticed that this lock is added by HDFS-15382, means that this logic is
> not in lock before.
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