This series is based on torvalds/master, but additionally the run_vmtests.sh
changes assume my refactor [1] has been applied first.

The series is split up like so:
- Patch 1 is a simple fixup which we should take in any case (even by itself).
- Patches 2-4 add the feature, basic support for it to the selftest, and docs.
- Patches 5-6 make the selftest configurable, so you can test one or the other
  instead of always both. If we decide this is overcomplicated, we could just
  drop these two patches and take the rest of the series.

[1]: https://patchwork.kernel.org/project/linux-mm/patch/20220421224928.1848230-1-axelrasmussen@google.com/

Changelog:
v1->v2:
  - Add documentation update.
  - Test *both* userfaultfd(2) and /dev/userfaultfd via the selftest.

Axel Rasmussen (6):
  selftests: vm: add hugetlb_shared userfaultfd test to run_vmtests.sh
  userfaultfd: add /dev/userfaultfd for fine grained access control
  userfaultfd: selftests: modify selftest to use /dev/userfaultfd
  userfaultfd: update documentation to describe /dev/userfaultfd
  userfaultfd: selftests: make /dev/userfaultfd testing configurable
  selftests: vm: add /dev/userfaultfd test cases to run_vmtests.sh

 Documentation/admin-guide/mm/userfaultfd.rst | 38 +++++++++-
 Documentation/admin-guide/sysctl/vm.rst      |  3 +
 fs/userfaultfd.c                             | 79 ++++++++++++++++----
 include/uapi/linux/userfaultfd.h             |  4 +
 tools/testing/selftests/vm/run_vmtests.sh    | 11 ++-
 tools/testing/selftests/vm/userfaultfd.c     | 60 +++++++++++++--
 6 files changed, 170 insertions(+), 25 deletions(-)

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2.36.0.rc2.479.g8af0fa9b8e-goog