commit a6a0564dc8f0b4de10f01ec35fea3ccd75ffa849
Author: Peter Jones <pjones@redhat.com>
Date:   Thu Nov 29 14:25:19 2007 -0500

    Add support for luks-based encrypted filesystems

contains:

@@ -1081,7 +1090,7 @@ if [ "x$PROBE" == "xyes" ]; then
             "$rootdev" != "${rootdev##UUID=}" ]; then
         rootopts=$(echo $rootopts | sed -e 's/^r[ow],//' -e 's/,_netdev//' -e
's/_netdev//' -e 's/,r[ow],$//' -e 's/,r[ow],/,/' -e 's/^r[ow]$/defaults/' -e
's/$/,ro/')
         physdev=$(findblockdevinsys "$rootdev")
-        physdev=${physdev##*/}
+        physdev=${physdev##*/dev/}
         if [ -n "$physdev" ]; then
             vecho "Found root device $physdev for $rootdev"
         else

Since physdev at this point is returning /sys/block/sda/sda2, this doesn't prune
the device name at all, and it therefore fails to find the root FS driver.

Reverting this bit fixes it.