linux-kernel - Re: [PULL] topic/iomem-mmap-vs-gup

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Message-ID: <CAHk-=wiwgOPQ+4Eaf0GD5P_GveE6vUHsKxAT=pMsjk1v_kh4ig@mail.gmail.com>
Date:   Thu, 6 May 2021 15:30:45 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Daniel Vetter <daniel.vetter@...ll.ch>
Cc:     DRI Development <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        linux-samsung-soc@...r.kernel.org
Subject: Re: [PULL] topic/iomem-mmap-vs-gup

[ You had a really odd Reply-to on this one ]

On Mon, May 3, 2021 at 12:15 PM Daniel Vetter <daniel.vetter@...ll.ch> wrote:
>
> Anyway here's a small pull for you to ponder, now that the big ones are
> all through.

Well, _now_ I'm all caught up. Knock wood. Anyway, time to look at it:

> Follow-up to my pull from last merge window: kvm and vfio lost their
> very unsafe use of follow_pfn, this appropriately marks up the very
> last user for some userptr-as-buffer use-cases in media. There was
> some resistance to outright removing it, maybe we can do this in a few
> releases.

Hmm. So this looks mostly ok to me, although I think the change to the
nommu case is pretty ridiculous.

On nommu, unsafe_follow_pfn() should just be a wrapper around
follow_pfn(). There's no races when you can't remap anything. No?

Do the two media cases even work on nommu?

Finally - did you intend fo this to be a real pull request? Because
the email read to me like "think about this and tell me what you
think" rather than "please pull"..

And I have now fulfilled that "think about and tell me" part ;)

              Linus