[$] The trouble with get_user_pages()

When kernel code needs to work directly with user-space pages, it oftencalls get_user_pages()(or one of several variants) to fault those pages into RAM and pin themthere. This function is not entirely easy to use, though, and recentchanges have made it harder to use safely. Jan Kara and Dan Williams led aplenary session at the 2018 Linux Storage, Filesystem, andMemory-Management Summit to discuss potential solutions, but it is notentirely clear that any were found.