[$] The ongoing trouble with get_user_pages()

The 2018 Linux Storage, Filesystem, and Memory-Management (LSFMM)conference included a session onget_user_pages(), an internal kernel interface that can, insome situations, be used in ways that will lead to data corruption orkernel crashes. As the 2023 LSFMM+BPF eventapproaches, this problem remains unsolved and is still the topic of ongoingdiscussion. This patchseries from Lorenzo Stoakes, which is another attempt at a partialsolution, is the latest focus point.