[$] Reconsidering the direct-map fragmentation problem

Mike Rapoport has put a considerable amount of effort into solving theproblem of direct-map fragmentation over the years; this has resulted inproposals like __GFP_UNMAPPED anda session at the 2022 Linux Storage,Filesystem, Memory-Management, and BPF Summit. Rapoport returned at the 2023 Summit to revisit this issue, but hestarted with a somewhat surprising spoiler.