Since Fedora 21, I'm not able to autocomplete paths if the already typed path contains spaces:
mkdir -p "a dir/b"
cd a[tab] -> gives cd a\ dir, which is fine
cd a\ dir/[tab] -> no effect, even after hitting tab several times

But if I do:
ls a\ dir/[tab]
I get the expected completion to a\ dir/b


This is with bash 4.3.30 on Fedora 21. It worked fine on Fedora 20.