Inconsistent behaviour around completion buffers

[Knut Forkalsrud]

When using the find-file function you can press TAB a couple of times
to get a completion buffer with filenames to choose from.  If you
don't like moving your arm from the keyboard to the mouse and back,
you can press the page-up key to jump to the completion buffer and
pick a file.  Once you are there pressing C-g will not cancel the
file-open operation.  I would expect that C-g aborted the find-file
function and maybe hide the completion buffer.

Also, when you type C-M-/ (dabbrev-completion) you can get the same
kind of completion buffer, but here the page-up key doesn't bring you
to the completion buffer like you are used to from the find-file
version.  I understand that this slightly more difficult to fit into
some consistent behaviour, since the active point is in a random
buffer when page-up is pressed.  The mode of that buffer most likely
has the page-up key bound to some other function, whereas the
minibuffer is always in minibuffer-mode.

Thanks,

-Knut