6 uses of FILE_READABLE

drupal_install_fix_file in drupal/core/includes/install.inc
Attempts to fix file permissions.
drupal_install_mkdir in drupal/core/includes/install.inc
Creates a directory with the specified permissions.
drupal_verify_install_file in drupal/core/includes/install.inc
Verifies the state of the specified file.
install_check_requirements in drupal/core/includes/install.core.inc
Checks installation requirements and reports any errors.
install_configure_form in drupal/core/includes/install.core.inc
Form constructor for a form to configure the new site.
update_prepare_d8_bootstrap in drupal/core/includes/update.inc
Performs extra steps required to bootstrap when using a Drupal 7 database.