If "root\_path" takes you to the root page, what's the equivalent path to redirect you to the same page?

Here's the context: I'm using Devise for logging in users on a Rails 4.0 app, and my "custom\_failure.rb" file currently redirects the user to the root page if login is unsuccessful.

Right now, a failed login will take the user to the root path. But the login form is on every page on the site, and if someone makes a failed login on page X, I want that user to stay on page X (or at least be redirected back to it). 

Here's my "custom\_failure.rb" file right now:

```
class CustomFailure < Devise::FailureApp
  def redirect_url
    root_path
  end
.
.
end

```

What should I type in to replace "root\_path"?