Useful if one need a prefix over module messages.
I use it in tty c/r, thus having something like

 | TTY: master 0x31 index 2 fd 6 pid 5079 (create 1)
 | TTY:     `- slave 0x5c index 2 fd 255 pid 5080 (create 0 send 0)
 | TTY: standalone slave 0x2e index 1 fd 3 pid 5079 (create 1)

in log. Which helps filtering messages.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>