[HDFS-11476] Fix NPE in FsDatasetImpl#checkAndUpdate

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.9.0, 3.0.0-alpha4
• Component/s: datanode
• Hadoop Flags: Reviewed
• Assignee: Xiaobing Zhou
• Reporter: Xiaobing Zhou
• Created: 28/Feb/17 23:35
• Updated: 24/Apr/18 20:46
• Resolved: 03/Mar/17 21:40

Description

diskMetaFile can be null and passed to compareTo which dereferences it, causing NPE

// Compare generation stamp
      if (memBlockInfo.getGenerationStamp() != diskGS) {
        File memMetaFile = FsDatasetUtil.getMetaFile(diskFile, 
            memBlockInfo.getGenerationStamp());
        if (memMetaFile.exists()) {
          if (memMetaFile.compareTo(diskMetaFile) != 0) {
            LOG.warn("Metadata file in memory "
                + memMetaFile.getAbsolutePath()
                + " does not match file found by scan "
                + (diskMetaFile == null? null: diskMetaFile.getAbsolutePath()));
          }
        } else {