The faulty package is system-config-printer which linterally creates
millions of files in /tmp [1].
As as side-effect, you'll see that rebooting your system can take ages,
when /tmp is being cleaned up [2] and you likely see output like this:
"a start job is running for Create Volatile files and directories (xx
minutes / no limit)"
Ext4 is highly inefficient apparently when dealing with huge amount of
files in on directory
[1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=764253
[2] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=766092#62