HBASE-27251 Rolling back from 2.5.0-SNAPSHOT to 2.4.13 fails due to 'File does not exist: /hbase/MasterData/data/master/store/.initialized/.regioninfo' Addendum

Author: Huaxiang Sun

hbase-server/src/main/java/org/apache/hadoop/hbase/master/region/MasterRegion.java

@@ -225,6 +225,12 @@ private static HRegion open(Configuration conf, TableDescriptor td, FileSystem f
     FileSystem walFs, Path walRootDir, WALFactory walFactory, MasterRegionWALRoller walRoller,
     String serverName) throws IOException {
     Path tableDir = CommonFSUtils.getTableDir(rootDir, td.getTableName());
+    FileStatus[] nonRegionDirs = fs.listStatus(tableDir, p -> p.getName().startsWith("."));
+    if (nonRegionDirs.length > 0) {
+      LOG.warn("There are non-region directories under " + tableDir + ", such as " +
+        nonRegionDirs[0].getPath() + ", ignored");
+    }
+
     // on branch-2, the RegionInfo.isEncodedRegionName will returns true for .initializing and
     // .initialized, see HBASE-25368. Since RegionInfo is IA.Public, changing the implementation may
     // raise compatibility concerns, so here we just skip them by our own.