[GitHub] [hadoop] tomscut commented on pull request #4945: HDFS-16785. DataNode hold BP write lock to scan disk

[GitBox <gi...@apache.org>]

tomscut commented on PR #4945:
URL: https://github.com/apache/hadoop/pull/4945#issuecomment-1295157989

   > ```
   >   final FsVolumeImpl fsVolume =
   >         createFsVolume(sd.getStorageUuid(), sd, location);
   >     // no need to add lock
   >     final ReplicaMap tempVolumeMap = new ReplicaMap();
   >     ArrayList<IOException> exceptions = Lists.newArrayList();
   > 
   >     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);
   >       }
   >     }
   > ```
   > 
   > The `fsVolume` here is a local temporary variable and still not be added into the `volumes`, and add/remove bp operations just use the volume in `volumes`, so there is no conflicts. So here doesn't need the lock for `BlockPoolSlice`.
   > 
   > @Hexiaoqiao Sir, can check it again?
   
   I agree with @ZanderXu here. +1 from my side.


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