Comment 5 for bug 843904

Reapplied these to master-next:

drm/i915: Fix refleak during eviction.
drm/i915: Hold a reference to the object whilst unbinding the eviction list
drm/i915: Remove BUG_ON from i915_gem_evict_something
drm/i915: Periodically flush the active lists and requests
drm/i915/evict: Ensure we completely cleanup on failure
drm/i915: Maintain LRU order of inactive objects upon access by CPU (v2)
drm/i915: Implement fair lru eviction across both rings. (v2)
drm/i915: Move the eviction logic to its own file.
drm/i915: prepare for fair lru eviction