Thanks for looking Andrew. And, fair criticism. In keeping with the status quo, I'm thinking of just adding a new command-line argument which toggles between the two modes. But, if I'm honest, it's starting to feel like the test has way too many arguments... I'm tempted to refactor the test to use the kselftest framework [1], get rid of all these command line arguments, and just always test everything. But, this seems like a big and perhaps controversial refactor, so I may take it up after this series... [1]: https://www.kernel.org/doc/html/latest/dev-tools/kselftest.html On Tue, Apr 12, 2022 at 1:42 PM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > On Tue, 12 Apr 2022 13:29:42 -0700 Axel Rasmussen <axelrasmussen@xxxxxxxxxx> wrote: > > > Prefer this new interface, but if using it fails for any reason just > > fall back to using userfaultfd(2) as before. > > This seems a poor idea - the old interface will henceforth be untested. > > Why not tweak the code to test both interfaces?