How to get a Bootstrap dropdown submenu to 'dropup'

Question

I have a Bootstrap dropdown menu. The last li item is a submenu. How do I get the submenu to dropup while the full menu drops down? Here's the code:

<div class="dropdown">
    <a class="inputBarA dropdown-toggle" data-toggle="dropdown" href="#">FILTER</a>
    <ul class="dropdown-menu" role="menu" aria-labelledby="dLabel">
        <li role="presentation">
            <a role="menuitem" href="#">Text</a>
        </li>
        <li role="presentation">
            <label>Label name</label>
            <label>Label name</label>
            <label class="checkbox">
                <input type="checkbox">
                Text </label>
            <label class="checkbox">
                <input type="checkbox">
                Text </label>
            <label class="checkbox">
                <input type="checkbox">
                Text </label>
            <label class="checkbox">
                <input type="checkbox">
                Text </label>
        </li>
        <li class="dropdown-submenu">
            <a tabindex="-1" href="#">Centralities</a>
            <ul class="dropdown-menu">
                <label class="radio">
                    <input type="radio" name="options" id="optionsRadios1" value="A" checked>
                    AA </label>
                <label class="radio">
                    <input type="radio" name="options" id="optionsRadios2" value="B">
                    BB </label><label class="radio">
                    <input type="radio" name="options" id="optionsRadios2" value="C">
                    CC </label><label class="radio">
                    <input type="radio" name="options" id="optionsRadios2" value="D">
                    DD </label><label class="radio">
                    <input type="radio" name="options" id="optionsRadios2" value="E">
                    EE </label>
            </ul>
        </li>
    </ul>
</div>

Answer 1

The best solution:

<div class="dropup">
   <ul class="dropdown-menu"></ul>
</div>

It's a native class in bootstrap. The bootstrap (using 3.1.1) css file has a .dropup .dropdown-menu selector so that's how I found out.