drm: mm: track free areas implicitly
The idea is to track free holes implicitly by marking the allocation immediatly preceeding a hole. To avoid an ugly corner case add a dummy head_node to struct drm_mm to track the hole that spans to complete allocation area when the memory manager is empty. To guarantee that there's always a preceeding/following node (that might be marked as hole_follows == 1), move the mm->node_list list_head to the head_node. The main allocator and fair-lru scan code actually becomes simpler. Only the debug code slightly suffers because free areas are no longer explicit. Also add drm_mm_for_each_node (which will be much more useful when struct drm_mm_node is embeddable). Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch> Signed-off-by: NDave Airlie <airlied@redhat.com>
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