* plan9assembler <plan9assembler@gmail.com> [2013-06-02 19:55:49 +0900]:

> and Szabolcs Nagy was right, sscanf malloc patch fixed umount segfault.
> but mount/umount timed out operation didn't fixed.
>

as you can see in the strace log mount waits in a loop
for /etc/mtab~ to disappear so it can link /etc/mtab~.PID
there, but it never disappears so mount fails

remove that file and mount will work