libnilfs: add functions to get pathname or FD of mount point directory

Add export functions to get the absolute path name or file descriptor
of the mount point directory (file system root directory).

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>

Author: konis

include/nilfs.h

@@ -79,6 +79,8 @@ struct nilfs *nilfs_open(const char *dev, const char *dir, int flags);
 void nilfs_close(struct nilfs *nilfs);
 
 const char *nilfs_get_dev(const struct nilfs *nilfs);
+const char *nilfs_get_root_path(const struct nilfs *nilfs);
+int nilfs_get_root_fd(const struct nilfs *nilfs);
 
 int nilfs_opt_test(const struct nilfs *nilfs, unsigned int index);
 int nilfs_opt_set(struct nilfs *nilfs, unsigned int index);

lib/nilfs.c

@@ -598,6 +598,31 @@ const char *nilfs_get_dev(const struct nilfs *nilfs)
 	return nilfs->n_dev;
 }
 
+/**
+ * nilfs_get_root_path - get the path name string of the mount point
+ * @nilfs: nilfs object
+ *
+ * Return: The absolute path name of the mount point directory, or %NULL if
+ * unavailable.
+ */
+const char *nilfs_get_root_path(const struct nilfs *nilfs)
+{
+	return nilfs->n_ioc;
+}
+
+/**
+ * nilfs_get_root_fd - get the file descriptor of the mount point directory
+ *                     (file system root directory)
+ * @nilfs: nilfs object
+ *
+ * Return: The file descriptor of the mount point directory, or -1 if not
+ * available.
+ */
+int nilfs_get_root_fd(const struct nilfs *nilfs)
+{
+	return nilfs->n_iocfd;
+}
+
 /**
  * nilfs_lock - acquire a lock
  * @nilfs: nilfs object