Re: [PATCH v3 2/3] userfaultfd: UFFDIO_MOVE uABI

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On 23.10.23 14:03, David Hildenbrand wrote:
On 22.10.23 17:46, Peter Xu wrote:
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.


I said everything I had to say, go read what I wrote.

Re-read your message after flying over first couple of paragraphs previously a bit quick too quickly (can easily happen when I'm told that I misunderstand questions and read them in a "biased" way).

I'll happy to discuss cross-mm support once we actually need it. I just don't see the need to spend any energy on that right now, without any users on the horizon.

[(a) I didn't blame anybody, I said that I don't understand the reasoning. (b) I hope I made it clear that this is added complexity (and not just currently dangerous) and so far I haven't heard a compelling argument why we should do any of that or even spend our time discussing that. (c) I never used "memcg is missing" as an argument for "cross-mm is dangerous", all about added complexity without actual users. (d) "it easily shows that there are cases where this will require extra work -- without any current benefits" -- is IMHO a perfectly fine argument against complexity that currently nobody needs]

--
Cheers,

David / dhildenb





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