HADOOP-10520. Extended attributes definition and FileSystem APIs for extended attributes. Contributed by Yi Liu.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/HDFS-2006@1590767 13f79535-47bb-0310-9956-ffa450edef68

hadoop-common-project/hadoop-common/CHANGES-HDFS-2006.txt

@@ -8,6 +8,9 @@ HDFS-2006 (Unreleased)
 
   IMPROVEMENTS
 
+  HADOOP-10520. Extended attributes definition and FileSystem APIs for
+  extended attributes. (Yi Liu via wang)
+
   OPTIMIZATIONS
 
   BUG FIXES

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/AbstractFileSystem.java

@@ -1039,6 +1039,154 @@ public abstract class AbstractFileSystem {
         + " doesn't support getAclStatus");
   }
 
+  /**
+   * Set the xattr of a file or directory.
+   * Name must be prefixed with user/trusted/security/system which
+   * followed by ".", For example "user.attr".
+   * <p/>
+   * A regular user only can set xattr of "user" namespace.
+   * A super user can set xattr of "user" and "trusted" namespace.
+   * XAttr of "security" and "system" namespace is only used/exposed
+   * internally to the FS impl.
+   * <p/>
+   * For xattr of "user" namespace, its access permissions are
+   * defined by the file or directory permission bits.
+   * XAttr will be set only when login user has correct permissions.
+   * If the xattr exists, it will be replaced.
+   * <p/>
+   * @see <a href="http://en.wikipedia.org/wiki/Extended_file_attributes">
+   * http://en.wikipedia.org/wiki/Extended_file_attributes</a>
+   *
+   * @param path Path to modify
+   * @param name xattr name.
+   * @param value xattr value.
+   * @throws IOException
+   */
+  public void setXAttr(Path path, String name, byte[] value)
+      throws IOException {
+    setXAttr(path, name, value, EnumSet.of(XAttrSetFlag.CREATE,
+        XAttrSetFlag.REPLACE));
+  }
+
+  /**
+   * Set the xattr of a file or directory.
+   * Name must be prefixed with user/trusted/security/system which
+   * followed by ".", For example "user.attr".
+   * <p/>
+   * A regular user only can set xattr of "user" namespace.
+   * A super user can set xattr of "user" and "trusted" namespace.
+   * XAttr of "security" and "system" namespace is only used/exposed
+   * internally to the FS impl.
+   * <p/>
+   * For xattr of "user" namespace, its access permissions are
+   * defined by the file or directory permission bits.
+   * XAttr will be set only when login user has correct permissions.
+   * <p/>
+   * @see <a href="http://en.wikipedia.org/wiki/Extended_file_attributes">
+   * http://en.wikipedia.org/wiki/Extended_file_attributes</a>
+   *
+   * @param path Path to modify
+   * @param name xattr name.
+   * @param value xattr value.
+   * @param flag xattr set flag
+   * @throws IOException
+   */
+  public void setXAttr(Path path, String name, byte[] value,
+      EnumSet<XAttrSetFlag> flag) throws IOException {
+    throw new UnsupportedOperationException(getClass().getSimpleName()
+        + " doesn't support setXAttr");
+  }
+
+  /**
+   * Get xattr of a file or directory.
+   * Name must be prefixed with user/trusted/security/system.
+   * <p/>
+   * A regular user only can get xattr of "user" namespace.
+   * A super user can get xattr of "user" and "trusted" namespace.
+   * XAttr of "security" and "system" namespace is only used/exposed
+   * internally to the FS impl.
+   * <p/>
+   * XAttr will be returned only when login user has correct permissions.
+   * <p/>
+   * @see <a href="http://en.wikipedia.org/wiki/Extended_file_attributes">
+   * http://en.wikipedia.org/wiki/Extended_file_attributes</a>
+   *
+   * @param path Path to get extended attribute
+   * @param name xattr name.
+   * @return byte[] xattr value.
+   * @throws IOException
+   */
+  public byte[] getXAttr(Path path, String name) throws IOException {
+    throw new UnsupportedOperationException(getClass().getSimpleName()
+        + " doesn't support getXAttr");
+  }
+
+  /**
+   * Get all xattrs of a file or directory.
+   * Only xattrs which login user has correct permissions will be returned.
+   * <p/>
+   * A regular user only can get xattr of "user" namespace.
+   * A super user can get xattr of "user" and "trusted" namespace.
+   * XAttr of "security" and "system" namespace is only used/exposed
+   * internally to the FS impl.
+   * <p/>
+   * @see <a href="http://en.wikipedia.org/wiki/Extended_file_attributes">
+   * http://en.wikipedia.org/wiki/Extended_file_attributes</a>
+   *
+   * @param path Path to get extended attributes
+   * @return Map<String, byte[]> describing the XAttrs of the file or directory
+   * @throws IOException
+   */
+  public Map<String, byte[]> getXAttrs(Path path) throws IOException {
+    throw new UnsupportedOperationException(getClass().getSimpleName()
+        + " doesn't support getXAttrs");
+  }
+
+  /**
+   * Get the xattrs of a file or directory.
+   * Name must be prefixed with user/trusted/security/system.
+   * Only xattrs which login user has correct permissions will be returned.
+   * <p/>
+   * A regular user only can get xattr of "user" namespace.
+   * A super user can get xattr of "user" and "trusted" namespace.
+   * XAttr of "security" and "system" namespace is only used/exposed
+   * internally to the FS impl.
+   * <p/>
+   * @see <a href="http://en.wikipedia.org/wiki/Extended_file_attributes">
+   * http://en.wikipedia.org/wiki/Extended_file_attributes</a>
+   *
+   * @param path Path to get extended attributes
+   * @param names XAttr names.
+   * @return Map<String, byte[]> describing the XAttrs of the file or directory
+   * @throws IOException
+   */
+  public Map<String, byte[]> getXAttrs(Path path, List<String> names)
+      throws IOException {
+    throw new UnsupportedOperationException(getClass().getSimpleName()
+        + " doesn't support getXAttrs");
+  }
+
+  /**
+   * Remove xattr of a file or directory.
+   * Name must be prefixed with user/trusted/security/system.
+   * <p/>
+   * A regular user only can remove xattr of "user" namespace.
+   * A super user can remove xattr of "user" and "trusted" namespace.
+   * XAttr of "security" and "system" namespace is only used/exposed
+   * internally to the FS impl.
+   * <p/>
+   * @see <a href="http://en.wikipedia.org/wiki/Extended_file_attributes">
+   * http://en.wikipedia.org/wiki/Extended_file_attributes</a>
+   *
+   * @param path Path to remove extended attribute
+   * @param name xattr name
+   * @throws IOException
+   */
+  public void removeXAttr(Path path, String name) throws IOException {
+    throw new UnsupportedOperationException(getClass().getSimpleName()
+        + " doesn't support removeXAttr");
+  }
+
   @Override //Object
   public int hashCode() {
     return myUri.hashCode();

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FileContext.java

@@ -2294,4 +2294,184 @@ public final class FileContext {
       }
     }.resolve(this, absF);
   }
+
+  /**
+   * Set the xattr of a file or directory.
+   * Name must be prefixed with user/trusted/security/system which
+   * followed by ".", For example "user.attr".
+   * <p/>
+   * A regular user only can set xattr of "user" namespace.
+   * A super user can set xattr of "user" and "trusted" namespace.
+   * XAttr of "security" and "system" namespace is only used/exposed
+   * internally to the FS impl.
+   * <p/>
+   * For xattr of "user" namespace, its access permissions are
+   * defined by the file or directory permission bits.
+   * XAttr will be set only when login user has correct permissions.
+   * If the xattr exists, it will be replaced.
+   * <p/>
+   * @see <a href="http://en.wikipedia.org/wiki/Extended_file_attributes">
+   * http://en.wikipedia.org/wiki/Extended_file_attributes</a>
+   *
+   * @param path Path to modify
+   * @param name xattr name.
+   * @param value xattr value.
+   * @throws IOException
+   */
+  public void setXAttr(Path path, String name, byte[] value)
+      throws IOException {
+    setXAttr(path, name, value, EnumSet.of(XAttrSetFlag.CREATE,
+        XAttrSetFlag.REPLACE));
+  }
+
+  /**
+   * Set the xattr of a file or directory.
+   * Name must be prefixed with user/trusted/security/system which
+   * followed by ".", For example "user.attr".
+   * <p/>
+   * A regular user only can set xattr of "user" namespace.
+   * A super user can set xattr of "user" and "trusted" namespace.
+   * XAttr of "security" and "system" namespace is only used/exposed
+   * internally to the FS impl.
+   * <p/>
+   * For xattr of "user" namespace, its access permissions are
+   * defined by the file or directory permission bits.
+   * XAttr will be set only when login user has correct permissions.
+   * <p/>
+   * @see <a href="http://en.wikipedia.org/wiki/Extended_file_attributes">
+   * http://en.wikipedia.org/wiki/Extended_file_attributes</a>
+   *
+   * @param path Path to modify
+   * @param name xattr name.
+   * @param value xattr value.
+   * @param flag xattr set flag
+   * @throws IOException
+   */
+  public void setXAttr(Path path, final String name, final byte[] value,
+      final EnumSet<XAttrSetFlag> flag) throws IOException {
+    Path absF = fixRelativePart(path);
+    new FSLinkResolver<Void>() {
+      @Override
+      public Void next(final AbstractFileSystem fs, final Path p)
+          throws IOException {
+        fs.setXAttr(p, name, value, flag);
+        return null;
+      }
+    }.resolve(this, absF);
+  }
+
+  /**
+   * Get xattr of a file or directory.
+   * Name must be prefixed with user/trusted/security/system.
+   * <p/>
+   * A regular user only can get xattr of "user" namespace.
+   * A super user can get xattr of "user" and "trusted" namespace.
+   * XAttr of "security" and "system" namespace is only used/exposed
+   * internally to the FS impl.
+   * <p/>
+   * XAttr will be returned only when login user has correct permissions.
+   * <p/>
+   * @see <a href="http://en.wikipedia.org/wiki/Extended_file_attributes">
+   * http://en.wikipedia.org/wiki/Extended_file_attributes</a>
+   *
+   * @param path Path to get extended attribute
+   * @param name xattr name.
+   * @return byte[] xattr value.
+   * @throws IOException
+   */
+  public byte[] getXAttr(Path path, final String name) throws IOException {
+    Path absF = fixRelativePart(path);
+    return new FSLinkResolver<byte[]>() {
+      @Override
+      public byte[] next(final AbstractFileSystem fs, final Path p)
+          throws IOException {
+        return fs.getXAttr(p, name);
+      }
+    }.resolve(this, absF);
+  }
+
+  /**
+   * Get all xattrs of a file or directory.
+   * Only xattrs which login user has correct permissions will be returned.
+   * <p/>
+   * A regular user only can get xattr of "user" namespace.
+   * A super user can get xattr of "user" and "trusted" namespace.
+   * XAttr of "security" and "system" namespace is only used/exposed
+   * internally to the FS impl.
+   * <p/>
+   * @see <a href="http://en.wikipedia.org/wiki/Extended_file_attributes">
+   * http://en.wikipedia.org/wiki/Extended_file_attributes</a>
+   *
+   * @param path Path to get extended attributes
+   * @return Map<String, byte[]> describing the XAttrs of the file or directory
+   * @throws IOException
+   */
+  public Map<String, byte[]> getXAttrs(Path path) throws IOException {
+    Path absF = fixRelativePart(path);
+    return new FSLinkResolver<Map<String, byte[]>>() {
+      @Override
+      public Map<String, byte[]> next(final AbstractFileSystem fs, final Path p)
+          throws IOException {
+        return fs.getXAttrs(p);
+      }
+    }.resolve(this, absF);
+  }
+
+  /**
+   * Get the xattrs of a file or directory.
+   * Name must be prefixed with user/trusted/security/system.
+   * Only xattrs which login user has correct permissions will be returned.
+   * <p/>
+   * A regular user only can get xattr of "user" namespace.
+   * A super user can get xattr of "user" and "trusted" namespace.
+   * XAttr of "security" and "system" namespace is only used/exposed
+   * internally to the FS impl.
+   * <p/>
+   * @see <a href="http://en.wikipedia.org/wiki/Extended_file_attributes">
+   * http://en.wikipedia.org/wiki/Extended_file_attributes</a>
+   *
+   * @param path Path to get extended attributes
+   * @param names XAttr names.
+   * @return Map<String, byte[]> describing the XAttrs of the file or directory
+   * @throws IOException
+   */
+  public Map<String, byte[]> getXAttrs(Path path, final List<String> names)
+      throws IOException {
+    Path absF = fixRelativePart(path);
+    return new FSLinkResolver<Map<String, byte[]>>() {
+      @Override
+      public Map<String, byte[]> next(final AbstractFileSystem fs, final Path p)
+          throws IOException {
+        return fs.getXAttrs(p, names);
+      }
+    }.resolve(this, absF);
+  }
+
+  /**
+   * Remove xattr of a file or directory.
+   * Name must be prefixed with user/trusted/security/system.
+   * <p/>
+   * A regular user only can remove xattr of "user" namespace.
+   * A super user can remove xattr of "user" and "trusted" namespace.
+   * XAttr of "security" and "system" namespace is only used/exposed
+   * internally to the FS impl.
+   * <p/>
+   * @see <a href="http://en.wikipedia.org/wiki/Extended_file_attributes">
+   * http://en.wikipedia.org/wiki/Extended_file_attributes</a>
+   *
+   * @param path Path to remove extended attribute
+   * @param name xattr name
+   * @throws IOException
+   */
+  public void removeXAttr(Path path, final String name) throws IOException {
+    Path absF = fixRelativePart(path);
+    new FSLinkResolver<Void>() {
+      @Override
+      public Void next(final AbstractFileSystem fs, final Path p)
+          throws IOException {
+        fs.removeXAttr(p, name);
+        return null;
+      }
+    }.resolve(this, absF);
+  }
 }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FileSystem.java

@@ -2350,6 +2350,154 @@ public abstract class FileSystem extends Configured implements Closeable {
         + " doesn't support getAclStatus");
   }
 
+  /**
+   * Set the xattr of a file or directory.
+   * Name must be prefixed with user/trusted/security/system which
+   * followed by ".", For example "user.attr".
+   * <p/>
+   * A regular user only can set xattr of "user" namespace.
+   * A super user can set xattr of "user" and "trusted" namespace.
+   * XAttr of "security" and "system" namespace is only used/exposed
+   * internally to the FS impl.
+   * <p/>
+   * For xattr of "user" namespace, its access permissions are
+   * defined by the file or directory permission bits.
+   * XAttr will be set only when login user has correct permissions.
+   * If the xattr exists, it will be replaced.
+   * <p/>
+   * @see <a href="http://en.wikipedia.org/wiki/Extended_file_attributes">
+   * http://en.wikipedia.org/wiki/Extended_file_attributes</a>
+   *
+   * @param path Path to modify
+   * @param name xattr name.
+   * @param value xattr value.
+   * @throws IOException
+   */
+  public void setXAttr(Path path, String name, byte[] value)
+      throws IOException {
+    setXAttr(path, name, value, EnumSet.of(XAttrSetFlag.CREATE,
+        XAttrSetFlag.REPLACE));
+  }
+
+  /**
+   * Set the xattr of a file or directory.
+   * Name must be prefixed with user/trusted/security/system which
+   * followed by ".", For example "user.attr".
+   * <p/>
+   * A regular user only can set xattr of "user" namespace.
+   * A super user can set xattr of "user" and "trusted" namespace.
+   * XAttr of "security" and "system" namespace is only used/exposed
+   * internally to the FS impl.
+   * <p/>
+   * For xattr of "user" namespace, its access permissions are
+   * defined by the file or directory permission bits.
+   * XAttr will be set only when login user has correct permissions.
+   * <p/>
+   * @see <a href="http://en.wikipedia.org/wiki/Extended_file_attributes">
+   * http://en.wikipedia.org/wiki/Extended_file_attributes</a>
+   *
+   * @param path Path to modify
+   * @param name xattr name.
+   * @param value xattr value.
+   * @param flag xattr set flag
+   * @throws IOException
+   */
+  public void setXAttr(Path path, String name, byte[] value,
+      EnumSet<XAttrSetFlag> flag) throws IOException {
+    throw new UnsupportedOperationException(getClass().getSimpleName()
+        + " doesn't support setXAttr");
+  }
+
+  /**
+   * Get xattr of a file or directory.
+   * Name must be prefixed with user/trusted/security/system.
+   * <p/>
+   * A regular user only can get xattr of "user" namespace.
+   * A super user can get xattr of "user" and "trusted" namespace.
+   * XAttr of "security" and "system" namespace is only used/exposed
+   * internally to the FS impl.
+   * <p/>
+   * XAttr will be returned only when login user has correct permissions.
+   * <p/>
+   * @see <a href="http://en.wikipedia.org/wiki/Extended_file_attributes">
+   * http://en.wikipedia.org/wiki/Extended_file_attributes</a>
+   *
+   * @param path Path to get extended attribute
+   * @param name xattr name.
+   * @return byte[] xattr value.
+   * @throws IOException
+   */
+  public byte[] getXAttr(Path path, String name) throws IOException {
+    throw new UnsupportedOperationException(getClass().getSimpleName()
+        + " doesn't support getXAttr");
+  }
+
+  /**
+   * Get all xattrs of a file or directory.
+   * Only xattrs which login user has correct permissions will be returned.
+   * <p/>
+   * A regular user only can get xattr of "user" namespace.
+   * A super user can get xattr of "user" and "trusted" namespace.
+   * XAttr of "security" and "system" namespace is only used/exposed
+   * internally to the FS impl.
+   * <p/>
+   * @see <a href="http://en.wikipedia.org/wiki/Extended_file_attributes">
+   * http://en.wikipedia.org/wiki/Extended_file_attributes</a>
+   *
+   * @param path Path to get extended attributes
+   * @return Map<String, byte[]> describing the XAttrs of the file or directory
+   * @throws IOException
+   */
+  public Map<String, byte[]> getXAttrs(Path path) throws IOException {
+    throw new UnsupportedOperationException(getClass().getSimpleName()
+        + " doesn't support getXAttrs");
+  }
+
+  /**
+   * Get the xattrs of a file or directory.
+   * Name must be prefixed with user/trusted/security/system.
+   * Only xattrs which login user has correct permissions will be returned.
+   * <p/>
+   * A regular user only can get xattr of "user" namespace.
+   * A super user can get xattr of "user" and "trusted" namespace.
+   * XAttr of "security" and "system" namespace is only used/exposed
+   * internally to the FS impl.
+   * <p/>
+   * @see <a href="http://en.wikipedia.org/wiki/Extended_file_attributes">
+   * http://en.wikipedia.org/wiki/Extended_file_attributes</a>
+   *
+   * @param path Path to get extended attributes
+   * @param names XAttr names.
+   * @return Map<String, byte[]> describing the XAttrs of the file or directory
+   * @throws IOException
+   */
+  public Map<String, byte[]> getXAttrs(Path path, List<String> names)
+      throws IOException {
+    throw new UnsupportedOperationException(getClass().getSimpleName()
+        + " doesn't support getXAttrs");
+  }
+
+  /**
+   * Remove xattr of a file or directory.
+   * Name must be prefixed with user/trusted/security/system.
+   * <p/>
+   * A regular user only can remove xattr of "user" namespace.
+   * A super user can remove xattr of "user" and "trusted" namespace.
+   * XAttr of "security" and "system" namespace is only used/exposed
+   * internally to the FS impl.
+   * <p/>
+   * @see <a href="http://en.wikipedia.org/wiki/Extended_file_attributes">
+   * http://en.wikipedia.org/wiki/Extended_file_attributes</a>
+   *
+   * @param path Path to remove extended attribute
+   * @param name xattr name
+   * @throws IOException
+   */
+  public void removeXAttr(Path path, String name) throws IOException {
+    throw new UnsupportedOperationException(getClass().getSimpleName()
+        + " doesn't support removeXAttr");
+  }
+
   // making it volatile to be able to do a double checked locking
   private volatile static boolean FILE_SYSTEMS_LOADED = false;
 

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FilterFileSystem.java

@@ -23,6 +23,7 @@ import java.net.URI;
 import java.net.URISyntaxException;
 import java.util.EnumSet;
 import java.util.List;
+import java.util.Map;
 
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
@@ -538,4 +539,37 @@ public class FilterFileSystem extends FileSystem {
   public AclStatus getAclStatus(Path path) throws IOException {
     return fs.getAclStatus(path);
   }
+
+  @Override
+  public void setXAttr(Path path, String name, byte[] value)
+      throws IOException {
+    fs.setXAttr(path, name, value);
+  }
+
+  @Override
+  public void setXAttr(Path path, String name, byte[] value,
+      EnumSet<XAttrSetFlag> flag) throws IOException {
+    fs.setXAttr(path, name, value, flag);
+  }
+
+  @Override
+  public byte[] getXAttr(Path path, String name) throws IOException {
+    return fs.getXAttr(path, name);
+  }
+
+  @Override
+  public Map<String, byte[]> getXAttrs(Path path) throws IOException {
+    return fs.getXAttrs(path);
+  }
+
+  @Override
+  public Map<String, byte[]> getXAttrs(Path path, List<String> names)
+      throws IOException {
+    return fs.getXAttrs(path, names);
+  }
+
+  @Override
+  public void removeXAttr(Path path, String name) throws IOException {
+    fs.removeXAttr(path, name);
+  }
 }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FilterFs.java

@@ -22,6 +22,7 @@ import java.net.URI;
 import java.net.URISyntaxException;
 import java.util.EnumSet;
 import java.util.List;
+import java.util.Map;
 
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
@@ -316,4 +317,37 @@ public abstract class FilterFs extends AbstractFileSystem {
   public AclStatus getAclStatus(Path path) throws IOException {
     return myFs.getAclStatus(path);
   }
+
+  @Override
+  public void setXAttr(Path path, String name, byte[] value)
+      throws IOException {
+    myFs.setXAttr(path, name, value);
+  }
+
+  @Override
+  public void setXAttr(Path path, String name, byte[] value,
+      EnumSet<XAttrSetFlag> flag) throws IOException {
+    myFs.setXAttr(path, name, value, flag);
+  }
+
+  @Override
+  public byte[] getXAttr(Path path, String name) throws IOException {
+    return myFs.getXAttr(path, name);
+  }
+
+  @Override
+  public Map<String, byte[]> getXAttrs(Path path) throws IOException {
+    return myFs.getXAttrs(path);
+  }
+
+  @Override
+  public Map<String, byte[]> getXAttrs(Path path, List<String> names)
+      throws IOException {
+    return myFs.getXAttrs(path, names);
+  }
+
+  @Override
+  public void removeXAttr(Path path, String name) throws IOException {
+    myFs.removeXAttr(path, name);
+  }
 }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/XAttrSetFlag.java

@@ -0,0 +1,71 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.hadoop.fs;
+
+import java.io.IOException;
+import java.util.EnumSet;
+
+import org.apache.hadoop.HadoopIllegalArgumentException;
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.classification.InterfaceStability;
+
+@InterfaceAudience.Public
+@InterfaceStability.Stable
+public enum XAttrSetFlag {
+  /**
+   * Create a new xattr.
+   * If the xattr exists already, exception will be thrown.
+   */
+  CREATE((short) 0x01),
+
+  /**
+   * Replace a existing xattr.
+   * If the xattr does not exist, exception will be thrown.
+   */
+  REPLACE((short) 0x02);
+
+  private final short flag;
+
+  private XAttrSetFlag(short flag) {
+    this.flag = flag;
+  }
+
+  short getFlag() {
+    return flag;
+  }
+
+  public static void validate(String xAttrName, boolean xAttrExists,
+      EnumSet<XAttrSetFlag> flag) throws IOException {
+    if (flag == null || flag.isEmpty()) {
+      throw new HadoopIllegalArgumentException("Should specify set flag");
+    }
+
+    if (xAttrExists) {
+      if (!flag.contains(REPLACE)) {
+        throw new IOException("XAttr: " + xAttrName +
+            " already exists. REPLACE flag must be specified.");
+      }
+    } else {
+      if (!flag.contains(CREATE)) {
+        throw new IOException("XAttr: " + xAttrName +
+            " does not exist. CREATE flag must be specified.");
+      }
+    }
+  }
+}

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/viewfs/ChRootedFileSystem.java

@@ -21,6 +21,7 @@ import java.io.IOException;
 import java.net.URI;
 import java.util.EnumSet;
 import java.util.List;
+import java.util.Map;
 
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
@@ -37,6 +38,7 @@ import org.apache.hadoop.fs.FilterFileSystem;
 import org.apache.hadoop.fs.FsServerDefaults;
 import org.apache.hadoop.fs.FsStatus;
 import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.fs.XAttrSetFlag;
 import org.apache.hadoop.fs.permission.AclEntry;
 import org.apache.hadoop.fs.permission.AclStatus;
 import org.apache.hadoop.fs.permission.FsPermission;
@@ -313,6 +315,33 @@ class ChRootedFileSystem extends FilterFileSystem {
     return super.getAclStatus(fullPath(path));
   }
 
+  @Override
+  public void setXAttr(Path path, String name, byte[] value,
+      EnumSet<XAttrSetFlag> flag) throws IOException {
+    super.setXAttr(fullPath(path), name, value, flag);
+  }
+
+  @Override
+  public byte[] getXAttr(Path path, String name) throws IOException {
+    return super.getXAttr(fullPath(path), name);
+  }
+
+  @Override
+  public Map<String, byte[]> getXAttrs(Path path) throws IOException {
+    return super.getXAttrs(fullPath(path));
+  }
+
+  @Override
+  public Map<String, byte[]> getXAttrs(Path path, List<String> names)
+      throws IOException {
+    return super.getXAttrs(fullPath(path), names);
+  }
+
+  @Override
+  public void removeXAttr(Path path, String name) throws IOException {
+    super.removeXAttr(fullPath(path), name);
+  }
+
   @Override
   public Path resolvePath(final Path p) throws IOException {
     return super.resolvePath(fullPath(p));

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/viewfs/ViewFileSystem.java

@@ -27,6 +27,7 @@ import java.util.Arrays;
 import java.util.EnumSet;
 import java.util.HashSet;
 import java.util.List;
+import java.util.Map;
 import java.util.Set;
 import java.util.Map.Entry;
 
@@ -46,6 +47,7 @@ import org.apache.hadoop.fs.FsConstants;
 import org.apache.hadoop.fs.FsServerDefaults;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.fs.UnsupportedFileSystemException;
+import org.apache.hadoop.fs.XAttrSetFlag;
 import org.apache.hadoop.fs.permission.AclEntry;
 import org.apache.hadoop.fs.permission.AclStatus;
 import org.apache.hadoop.fs.permission.FsPermission;
@@ -519,6 +521,43 @@ public class ViewFileSystem extends FileSystem {
     return res.targetFileSystem.getAclStatus(res.remainingPath);
   }
 
+  @Override
+  public void setXAttr(Path path, String name, byte[] value,
+      EnumSet<XAttrSetFlag> flag) throws IOException {
+    InodeTree.ResolveResult<FileSystem> res =
+        fsState.resolve(getUriPath(path), true);
+    res.targetFileSystem.setXAttr(res.remainingPath, name, value, flag);
+  }
+
+  @Override
+  public byte[] getXAttr(Path path, String name) throws IOException {
+    InodeTree.ResolveResult<FileSystem> res =
+        fsState.resolve(getUriPath(path), true);
+    return res.targetFileSystem.getXAttr(res.remainingPath, name);
+  }
+
+  @Override
+  public Map<String, byte[]> getXAttrs(Path path) throws IOException {
+    InodeTree.ResolveResult<FileSystem> res =
+        fsState.resolve(getUriPath(path), true);
+    return res.targetFileSystem.getXAttrs(res.remainingPath);
+  }
+
+  @Override
+  public Map<String, byte[]> getXAttrs(Path path, List<String> names)
+      throws IOException {
+    InodeTree.ResolveResult<FileSystem> res =
+        fsState.resolve(getUriPath(path), true);
+    return res.targetFileSystem.getXAttrs(res.remainingPath, names);
+  }
+
+  @Override
+  public void removeXAttr(Path path, String name) throws IOException {
+    InodeTree.ResolveResult<FileSystem> res = fsState.resolve(getUriPath(path),
+        true);
+    res.targetFileSystem.removeXAttr(res.remainingPath, name);
+  }
+
   @Override
   public void setVerifyChecksum(final boolean verifyChecksum) { 
     List<InodeTree.MountPoint<FileSystem>> mountPoints = 

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/fs/TestHarFileSystem.java

@@ -36,6 +36,7 @@ import java.lang.reflect.Modifier;
 import java.util.EnumSet;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Map;
 
 import static org.apache.hadoop.fs.Options.ChecksumOpt;
 import static org.apache.hadoop.fs.Options.CreateOpts;
@@ -181,6 +182,21 @@ public class TestHarFileSystem {
 
     public void setAcl(Path path, List<AclEntry> aclSpec) throws IOException;
 
+    public void setXAttr(Path path, String name, byte[] value)
+        throws IOException;
+
+    public void setXAttr(Path path, String name, byte[] value,
+        EnumSet<XAttrSetFlag> flag) throws IOException;
+
+    public byte[] getXAttr(Path path, String name) throws IOException;
+
+    public Map<String, byte[]> getXAttrs(Path path) throws IOException;
+
+    public Map<String, byte[]> getXAttrs(Path path, List<String> names)
+        throws IOException;
+
+    public void removeXAttr(Path path, String name) throws IOException;
+
     public AclStatus getAclStatus(Path path) throws IOException;
   }