userfaultfd: selftests: modify selftest to use /dev/userfaultfd

We clearly want to ensure both userfaultfd(2) and /dev/userfaultfd keep
working into the future, so just run the test twice, using each interface.

Instead of always testing both userfaultfd(2) and /dev/userfaultfd, let
the user choose which to test.

As with other test features, change the behavior based on a new command
line flag.  Introduce the idea of "test mods", which are generic (not
specific to a test type) modifications to the behavior of the test.  This
is sort of borrowed from this RFC patch series [1], but simplified a bit.

The benefit is, in "typical" configurations this test is somewhat slow
(say, 30sec or something).  Testing both clearly doubles it, so it may not
always be desirable, as users are likely to use one or the other, but
never both, in the "real world".

[1]: https://patchwork.kernel.org/project/linux-mm/patch/[email protected]/

[[email protected]: modify selftest to exit with KSFT_SKIP *only* when features are unsupported, per Mike]
  Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Axel Rasmussen <[email protected]>
Acked-by: Peter Xu <[email protected]>
Acked-by: Mike Rapoport <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Dmitry V. Levin <[email protected]>
Cc: Gleb Fotengauer-Malinovskiy <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Shuah Khan <[email protected]>
Cc: Shuah Khan <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Zhang Yi <[email protected]>
Cc: Mike Rapoport <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions