linux-kernel - Re: [PATCH v3 2/3] userfaultfd: UFFDIO

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Message-ID: <ZTVD18RgBfITsQC4@x1n>
Date:   Sun, 22 Oct 2023 11:46:31 -0400
From:   Peter Xu <peterx@...hat.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     Suren Baghdasaryan <surenb@...gle.com>,
        Lokesh Gidra <lokeshgidra@...gle.com>,
        akpm@...ux-foundation.org, viro@...iv.linux.org.uk,
        brauner@...nel.org, shuah@...nel.org, aarcange@...hat.com,
        hughd@...gle.com, mhocko@...e.com, axelrasmussen@...gle.com,
        rppt@...nel.org, willy@...radead.org, Liam.Howlett@...cle.com,
        jannh@...gle.com, zhangpeng362@...wei.com, bgeffon@...gle.com,
        kaleshsingh@...gle.com, ngeoffray@...gle.com, jdduke@...gle.com,
        linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        kernel-team@...roid.com
Subject: Re: [PATCH v3 2/3] userfaultfd: UFFDIO_MOVE uABI

On Fri, Oct 20, 2023 at 07:16:19PM +0200, David Hildenbrand wrote:
> These are rather the vibes I'm getting from Peter. "Why rename it, could
> confuse people because the original patches are old", "Why exclude it if it
> has been included in the original patches". Not the kind of reasoning I can
> relate to when it comes to upstreaming some patches.

You can't blame anyone if you misunderstood and biased the question.

The first question is definitely valid, even until now.  You guys still
prefer to rename it, which I'm totally fine with.

The 2nd question is wrong from your interpretation.  That's not my point,
at least not starting from a few replies already.  What I was asking for is
why such page movement between mm is dangerous.  I don't think I get solid
answers even until now.

Noticing "memcg is missing" is not an argument for "cross-mm is dangerous",
it's a review comment.  Suren can address that.

You'll propose a new feature that may tag an mm is not an argument either,
if it's not merged yet.  We can also address that depending on what it is,
also on which lands earlier.

It'll be good to discuss these details even in a single-mm support.  Anyone
would like to add that can already refer to discussion in this thread.

I hope I'm clear.

-- 
Peter Xu