eCryptfs: Check return of filemap_write_and_wait during fsync

Error out of ecryptfs_fsync() if filemap_write_and_wait() fails.
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Cc: Paul Taysom <taysom@chromium.org>
Cc: Olof Johansson <olofj@chromium.org>
Cc: stable@vger.kernel.org # v3.6+

fs/ecryptfs/file.c

@@ -295,7 +295,12 @@ static int ecryptfs_release(struct inode *inode, struct file *file)
 static int
 ecryptfs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 {
-	filemap_write_and_wait(file->f_mapping);
+	int rc;
+
+	rc = filemap_write_and_wait(file->f_mapping);
+	if (rc)
+		return rc;
+
 	return vfs_fsync(ecryptfs_file_to_lower(file), datasync);
 }