8360887: [AIX] getFileAttributeView returns unusable FileAttributeView if UserDefinedFileAttributeView unavailable

Author: TheRealMDoerr

src/java.base/aix/classes/sun/nio/fs/AixFileSystemProvider.java

@@ -52,15 +52,24 @@ AixFileStore getFileStore(UnixPath path) throws IOException {
         return new AixFileStore(path);
     }
 
+    static boolean supportsUserDefinedFileAttributeView(Path obj) {
+        try {
+            FileStore store = Files.getFileStore(obj);
+            return store.supportsFileAttributeView(UserDefinedFileAttributeView.class);
+        } catch (IOException e) {
+            return false;
+        }
+    }
+
     @Override
     @SuppressWarnings("unchecked")
     public <V extends FileAttributeView> V getFileAttributeView(Path obj,
                                                                 Class<V> type,
                                                                 LinkOption... options)
     {
         if (type == UserDefinedFileAttributeView.class) {
-            return (V) new AixUserDefinedFileAttributeView(UnixPath.toUnixPath(obj),
-                    Util.followLinks(options));
+            return !supportsUserDefinedFileAttributeView(obj) ? null :
+                (V) new AixUserDefinedFileAttributeView(UnixPath.toUnixPath(obj), Util.followLinks(options));
         }
         return super.getFileAttributeView(obj, type, options);
     }
@@ -71,8 +80,8 @@ public DynamicFileAttributeView getFileAttributeView(Path obj,
                                                          LinkOption... options)
     {
         if (name.equals("user")) {
-            return new AixUserDefinedFileAttributeView(UnixPath.toUnixPath(obj),
-                    Util.followLinks(options));
+            return !supportsUserDefinedFileAttributeView(obj) ? null :
+                new AixUserDefinedFileAttributeView(UnixPath.toUnixPath(obj), Util.followLinks(options));
         }
         return super.getFileAttributeView(obj, name, options);
     }

test/jdk/java/nio/file/attribute/UserDefinedFileAttributeView/Basic.java

@@ -282,6 +282,11 @@ public static void main(String[] args) throws IOException {
         Path dir = TestUtil.createTemporaryDirectory();
         try {
             if (!Files.getFileStore(dir).supportsFileAttributeView("user")) {
+                // check if getFileAttributeView behaves as specified in this case
+                if (Files.getFileAttributeView(dir, UserDefinedFileAttributeView.class) != null) {
+                    throw new RuntimeException("UserDefinedFileAttributeView not supported, getFileAttributeView should return null");
+                }
+
                 System.out.println("UserDefinedFileAttributeView not supported - skip test");
                 return;
             }