8034057: Files.getFileStore and Files.isWritable do not work with SUBST'ed drives (win)

Reviewed-by: alanb, chegar
Contributed-by: pavel.rappo@oracle.com

src/windows/classes/sun/nio/fs/WindowsConstants.java

@@ -98,6 +98,7 @@ class WindowsConstants {
     public static final int ERROR_DISK_FULL             = 112;
     public static final int ERROR_INSUFFICIENT_BUFFER   = 122;
     public static final int ERROR_INVALID_LEVEL         = 124;
+    public static final int ERROR_DIR_NOT_ROOT          = 144;
     public static final int ERROR_DIR_NOT_EMPTY         = 145;
     public static final int ERROR_ALREADY_EXISTS        = 183;
     public static final int ERROR_MORE_DATA             = 234;

src/windows/classes/sun/nio/fs/WindowsFileStore.java

@@ -86,14 +86,28 @@ class WindowsFileStore
                 WindowsFileAttributes.get(file, true);
                 target = file.getPathForWin32Calls();
             }
-            String root = GetVolumePathName(target);
-            return new WindowsFileStore(root);
+            try {
+                return createFromPath(target);
+            } catch (WindowsException e) {
+                if (e.lastError() != ERROR_DIR_NOT_ROOT)
+                    throw e;
+                target = WindowsLinkSupport.getFinalPath(file);
+                if (target == null)
+                    throw new FileSystemException(file.getPathForExceptionMessage(),
+                            null, "Couldn't resolve path");
+                return createFromPath(target);
+            }
         } catch (WindowsException x) {
             x.rethrowAsIOException(file);
             return null; // keep compiler happy
         }
     }
 
+    private static WindowsFileStore createFromPath(String target) throws WindowsException {
+        String root = GetVolumePathName(target);
+        return new WindowsFileStore(root);
+    }
+
     VolumeInformation volumeInformation() {
         return volInfo;
     }

src/windows/classes/sun/nio/fs/WindowsLinkSupport.java

@@ -66,7 +66,7 @@ class WindowsLinkSupport {
      * Returns the final path (all symbolic links resolved) or null if this
      * operation is not supported.
      */
-    private static String getFinalPath(WindowsPath input) throws IOException {
+    static String getFinalPath(WindowsPath input) throws IOException {
         long h = 0;
         try {
             h = input.openForReadAttributeAccess(true);