[RFC] Per file OOM badness

[Andrey Grodzovsky]

Hi, this series is a revised version of an RFC sent by Christian König
a few years ago. The original RFC can be found at 
https://lists.freedesktop.org/archives/dri-devel/2015-September/089778.html

This is the same idea and I've just adressed his concern from the original RFC 
and switched to a callback into file_ops instead of a new member in struct file.

Thanks,
Andrey