How to get a Bootstrap dropdown submenu to 'dropup'

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>

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.

It sounds like the answer below would be how to do it from scratch, I was unaware there was a dropup class in Bootstrap...

So the short Bootstrap answer is to apply the class "dropup" to the <ul> in earlier versions of bootstrap:

 <ul class="dropdown-menu dropup" role="menu" aria-labelledby="dLabel">

However in newer versions of bootstrap (v3) the "dropup" class needs to be applied to the <ul>'s container instead of the the <ul> itself:

<div class="dropup">
    <ul class="dropdown-menu" role="menu" aria-labelledby="dLabel">
</div>

See http://jsfiddle.net/ZgyZP/5/

Original working answer that doesn't use bootstrap:

You could use javascript to calculate the height of the submenu and then negatively offset the submenu's position.

something like (with jQuery):

$('.dropdown-submenu').hover(
    function(){
    //hover in 
        $('.dropdown-submenu > ul').css('top', '-' + $('.dropdown-submenu > ul').css('height'));

    },
    //hover out
    function(){
    }
);

Fiddle: http://jsfiddle.net/ZgyZP/4/

Use a class, like up <ul class="dropdown up">

Write style of up .up { bottom:100% !important; top:auto !important; }

Note: Increase bottom as per your button size.

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

The above code is correct, but doesn't work unless a parent element has the position property set.

Examples that works are class="col-lg-12" or just

<div style="position: relative;">

I use Bootstrap v3.0.0.