From: Peter Xu <peterx@redhat.com>
To: Axel Rasmussen <axelrasmussen@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Shuah Khan <shuah@kernel.org>, Linux MM <linux-mm@kvack.org>,
Linuxkselftest <linux-kselftest@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/3] userfaultfd/selftests: fix feature support detection
Date: Wed, 22 Sep 2021 13:32:56 -0400 [thread overview]
Message-ID: <YUtoyNic4Jxfv9f7@t490s> (raw)
In-Reply-To: <CAJHvVciZc0mpcw8OSPk71YsVzCTajY+ikymcD3+zBJKsZynYkg@mail.gmail.com>
Hello, Axel,
On Wed, Sep 22, 2021 at 10:04:03AM -0700, Axel Rasmussen wrote:
> Thanks for discussing the design Peter. I have some ideas which might
> make for a nicer v2; I'll massage the code a bit and see what I can
> come up with.
Sure thing. Note again that as I don't have a strong opinion on that, feel
free to keep it. However if you provide v2, I'll read.
[off-topic below]
Another thing I probably have forgot but need your confirmation is, when you
worked on uffd minor mode, did you explicitly disable thp, or is it allowed?
When I'm reworking the uffd-wp series, I noticed that commit e1e267c7928f
("khugepaged: skip collapse if uffd-wp detected", 2020-04-07) was actually
awkward and not efficient, as we can simply lookup the vma flags for detecting
uffd-wp enablement. I'm preparing a patch for it to do it by checking vmas
(and that patch will also pave the way for file-backed).
Then I noticed we need similar thing for minor mode?
I think the answer is yes, but I didn't see any code that explicitly handled
thp for minor mode, do you remember?
To be explicit, what if in mcontinue_atomic_pte() we get a shmem_getpage() call
with a thp returned? Will minor mode break?
I plan to post the khugepaged patch soon and I plan to cover minor mode too
there, but I'm not sure whether that's enough, as the thp can be there from the
1st day I think, but I could have missed something.
--
Peter Xu
next prev parent reply other threads:[~2021-09-22 17:33 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-21 16:33 [PATCH 1/3] userfaultfd/selftests: fix feature support detection Axel Rasmussen
2021-09-21 16:33 ` [PATCH 2/3] userfaultfd/selftests: fix calculation of expected ioctls Axel Rasmussen
2021-09-21 16:33 ` [PATCH 3/3] userfaultfd/selftests: don't rely on GNU extensions for random numbers Axel Rasmussen
2021-09-21 18:03 ` Peter Xu
2021-09-21 17:44 ` [PATCH 1/3] userfaultfd/selftests: fix feature support detection Peter Xu
2021-09-21 18:26 ` Axel Rasmussen
2021-09-21 19:21 ` Peter Xu
2021-09-21 20:31 ` Axel Rasmussen
2021-09-22 0:29 ` Peter Xu
2021-09-22 17:04 ` Axel Rasmussen
2021-09-22 17:32 ` Peter Xu [this message]
2021-09-22 20:54 ` Axel Rasmussen
2021-09-22 21:51 ` Peter Xu
2021-09-22 22:29 ` Axel Rasmussen
2021-09-22 23:49 ` Peter Xu
2021-09-23 4:17 ` James Houghton
2021-09-23 5:43 ` Jue Wang
2021-09-24 20:09 ` Peter Xu
2021-09-24 20:22 ` Jue Wang
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