[$] Landlock (finally) sets sail

Kernel development is not for people who lack persistence; changes can takea number of revisions and a lot of time to make it into a mainlinerelease. Even so, the story of the Landlock security module, developed byMickael Salaun, seems like an extreme case; this code was merged for 5.13 aftermore than five years of development and 34 versions of the patch set.This sandboxing mechanism has evolved considerably since LWN covered version 3 of the patch set in2016, so a look at what Landlock has become is warranted.