how does anaconda determine the mountpoint of an ext3 filesystem? (during fedora upgrade from ISO)

[John Lumby]

I hope it is ok to ask a question about a problem I'm having with anaconda.

I am trying to upgrade a Fedora 15 system to Fedora 16 using the Fedora 16 iso,
using the "upgrade existing system".   This is anaconda  16.25 .   
I have run into the problem described in
    https://bugzilla.redhat.com/show_bug.cgi?id=743647

I have posted some comments there,   but basically I am hitting a hard stop when
anaconda comes to try to mount my F15 root filesystem,  because it is failing to
discover the mountpoint of this filesystem.

The problem occurs about 1 second after the screen which shows the discovered 
existing Fedora system  (which it correctly identifies as Fedora 15 on /dev/sda3),
and asks me to confirm to go ahead with the upgrade.

I tried some static debugging from the python source and can see that it cannot decide which
is the rootDevice of the fsset because it fails to match any of the filesystem devices in the fsset to "/".
But this is weird because it has already found my root filesystem and must have mounted it in order
to read the fstab and so on.

By the way,  I have successfully upgraded a different Fedora 15 to F16 using this same iso image,
so I know this iso is good.

Anyway,   I have two questions and hope someone can answer:

.  in anaconda 16.25,  how does it determine what is the mountpoint of an ext3 filesystem?
     (pointer to relevant code appreciated)
.   is there any way to turn on tracing of python code during anaconda upgrade of existing Fedora?

Oh  -  and  -  does anyone know if this has been fixed in later anaconda releases?

John Lumby