HDFS-9273. ACLs on root directory may be lost after NN restart. Contributed by Xiao Chen.

(cherry picked from commit 1b525a9c32fabd8919c80717a58afbfa7fdce27e)
(cherry picked from commit faf1c608990408e2aa59a5e676f86d0c82dbd7f3)
(cherry picked from commit 339714baa0124d44c10d375a99fec7e1968445b1)

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -12,6 +12,9 @@ Release 2.6.4 - UNRELEASED
 
   BUG FIXES
 
+    HDFS-9273. ACLs on root directory may be lost after NN restart.
+    (Xiao Chen via cnauroth)
+
 Release 2.6.3 - UNRELEASED
 
   INCOMPATIBLE CHANGES

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImageFormatPBINode.java

@@ -338,6 +338,10 @@ public final class FSImageFormatPBINode {
       }
       dir.rootDir.cloneModificationTime(root);
       dir.rootDir.clonePermissionStatus(root);
+      final AclFeature af = root.getFeature(AclFeature.class);
+      if (af != null) {
+        dir.rootDir.addAclFeature(af);
+      }
       // root dir supports having extended attributes according to POSIX
       final XAttrFeature f = root.getXAttrFeature();
       if (f != null) {

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestFSImageWithAcl.java

@@ -206,6 +206,35 @@ public class TestFSImageWithAcl {
     doTestDefaultAclNewChildren(false);
   }
 
+  @Test
+  public void testRootACLAfterLoadingFsImage() throws IOException {
+    DistributedFileSystem fs = cluster.getFileSystem();
+    Path rootdir = new Path("/");
+    AclEntry e1 = new AclEntry.Builder().setName("foo")
+        .setPermission(ALL).setScope(ACCESS).setType(GROUP).build();
+    AclEntry e2 = new AclEntry.Builder().setName("bar")
+        .setPermission(READ).setScope(ACCESS).setType(GROUP).build();
+    fs.modifyAclEntries(rootdir, Lists.newArrayList(e1, e2));
+
+    AclStatus s = cluster.getNamesystem().getAclStatus(rootdir.toString());
+    AclEntry[] returned =
+        Lists.newArrayList(s.getEntries()).toArray(new AclEntry[0]);
+    Assert.assertArrayEquals(
+        new AclEntry[] { aclEntry(ACCESS, GROUP, READ_EXECUTE),
+            aclEntry(ACCESS, GROUP, "bar", READ),
+            aclEntry(ACCESS, GROUP, "foo", ALL) }, returned);
+
+    // restart - hence save and load from fsimage
+    restart(fs, true);
+
+    s = cluster.getNamesystem().getAclStatus(rootdir.toString());
+    returned = Lists.newArrayList(s.getEntries()).toArray(new AclEntry[0]);
+    Assert.assertArrayEquals(
+        new AclEntry[] { aclEntry(ACCESS, GROUP, READ_EXECUTE),
+            aclEntry(ACCESS, GROUP, "bar", READ),
+            aclEntry(ACCESS, GROUP, "foo", ALL) }, returned);
+  }
+
   /**
    * Restart the NameNode, optionally saving a new checkpoint.
    *