Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH v4 09/10] userfaultfd: update documentation to describe
 minor fault handling
To:     Axel Rasmussen <axelrasmussen@google.com>
Cc:     Alexander Viro <viro@zeniv.linux.org.uk>,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Anshuman Khandual <anshuman.khandual@arm.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Chinwen Chang <chinwen.chang@mediatek.com>,
        Huang Ying <ying.huang@intel.com>,
        Ingo Molnar <mingo@redhat.com>, Jann Horn <jannh@google.com>,
        Jerome Glisse <jglisse@redhat.com>,
        Lokesh Gidra <lokeshgidra@google.com>,
        "Matthew Wilcox (Oracle)" <willy@infradead.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        =?UTF-8?Q?Michal_Koutn=c3=bd?= <mkoutny@suse.com>,
        Michel Lespinasse <walken@google.com>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Mike Rapoport <rppt@linux.vnet.ibm.com>,
        Nicholas Piggin <npiggin@gmail.com>,
        Peter Xu <peterx@redhat.com>, Shaohua Li <shli@fb.com>,
        Shawn Anastasio <shawn@anastas.io>,
        Steven Rostedt <rostedt@goodmis.org>,
        Steven Price <steven.price@arm.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-fsdevel@vger.kernel.org, Linux MM <linux-mm@kvack.org>,
        Adam Ruprecht <ruprecht@google.com>,
        Cannon Matthews <cannonmatthews@google.com>,
        "Dr . David Alan Gilbert" <dgilbert@redhat.com>,
        David Rientjes <rientjes@google.com>,
        Mina Almasry <almasrymina@google.com>,
        Oliver Upton <oupton@google.com>
References: <20210204183433.1431202-1-axelrasmussen@google.com>
 <20210204183433.1431202-10-axelrasmussen@google.com>
 <bb81e2b1-eb6b-0dfb-c2d6-82843d3750e7@infradead.org>
 <CAJHvVchiABBitTRkr4boSj7pkBN3_y7-1kLVxyhCo5w4m=PEEA@mail.gmail.com>
From:   Randy Dunlap <rdunlap@infradead.org>
Message-ID: <d457b1bf-023a-89c0-fad0-c61b2792dfb3@infradead.org>
Date:   Thu, 4 Feb 2021 13:07:55 -0800
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101
 Thunderbird/78.4.0
MIME-Version: 1.0
In-Reply-To: <CAJHvVchiABBitTRkr4boSj7pkBN3_y7-1kLVxyhCo5w4m=PEEA@mail.gmail.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 2/4/21 1:04 PM, Axel Rasmussen wrote:
> On Thu, Feb 4, 2021 at 11:57 AM Randy Dunlap <rdunlap@infradead.org> wrote:
>>
>> 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. :)
> 
> For better or worse, other parts of the document I'm not touching also
> use this wording. Maybe we should s/userland/userspace/g, but perhaps
> better done as a separate commit to keep this diff focused?
> Anecdotally, the use of "userland" doesn't seem to be completely
> unprecedented (e.g. grep -r "userland" | wc -l yields 566 matches in
> the kernel tree).
> 
> I don't have strong feelings, and I was amused by picturing some
> Shire-esque countryside with a friendly sign that reads: ~userland
> welcomes you~. :)

I'm OK with not changing it. Up to you.

-- 
~Randy