Re: [PATCH v4 09/10] userfaultfd: update documentation to describe minor fault handling

[Randy Dunlap <rdunlap@infradead.org>]

Hi Axel-

one typo found:

On 2/4/21 10:34 AM, Axel Rasmussen wrote:
> Reword / reorganize things a little bit into "lists", so new features /
> modes / ioctls can sort of just be appended.

Good plan.

> 
> Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
> ---
>  Documentation/admin-guide/mm/userfaultfd.rst | 107 ++++++++++++-------
>  1 file changed, 66 insertions(+), 41 deletions(-)
> 
> diff --git a/Documentation/admin-guide/mm/userfaultfd.rst b/Documentation/admin-guide/mm/userfaultfd.rst
> index 65eefa66c0ba..cfd3daf59d0e 100644
> --- a/Documentation/admin-guide/mm/userfaultfd.rst
> +++ b/Documentation/admin-guide/mm/userfaultfd.rst

[snip]

> -
> -Once the ``userfaultfd`` has been enabled the ``UFFDIO_REGISTER`` ioctl should
> -be invoked (if present in the returned ``uffdio_api.ioctls`` bitmask) to
> -register a memory range in the ``userfaultfd`` by setting the
> +events, except page fault notifications, may be generated:
> +
> +- The ``UFFD_FEATURE_EVENT_*`` flags indicate that various other events
> +  other than page faults are supported. These events are described in more
> +  detail below in the `Non-cooperative userfaultfd`_ section.
> +
> +- ``UFFD_FEATURE_MISSING_HUGETLBFS`` and ``UFFD_FEATURE_MISSING_SHMEM``
> +  indicate that the kernel supports ``UFFDIO_REGISTER_MODE_MISSING``
> +  registrations for hugetlbfs and shared memory (covering all shmem APIs,
> +  i.e. tmpfs, ``IPCSHM``, ``/dev/zero``, ``MAP_SHARED``, ``memfd_create``,
> +  etc) virtual memory areas, respectively.
> +
> +- ``UFFD_FEATURE_MINOR_HUGETLBFS`` indicates that the kernel supports
> +  ``UFFDIO_REGISTER_MODE_MINOR`` registration for hugetlbfs virtual memory
> +  areas.
> +
> +The userland application should set the feature flags it intends to use

(ah, userspace has moved to userland temporarily. :)

> +when envoking the ``UFFDIO_API`` ioctl, to request that those features be

        invoking

> +enabled if supported.


thanks.
-- 
~Randy