[$] Prerequisites for large anonymous folios

The work to add support for large anonymousfolios to the kernel has been underway for some time, but this featurehas not yet landed in the mainline. The author of this work, Ryan Roberts,has been trying to get a handle on what the remaining obstacles are so hecan address them. On September6, an online meeting ofmemory-management developers discussed that topic and made some progress;there is still some work to do, though, before large anonymous folios cango upstream.