[$] Prerequisites for large anonymous folios

The work to add support for large anonymous
folios to the kernel has been underway for some time, but this feature
has 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 he
can address them. On September 6, an online meeting of
memory-management developers discussed that topic and made some progress;
there is still some work to do, though, before large anonymous folios can
go upstream.