linux-kernel - Re: Ack to merge through DRM? WAS Re: [PATCH v2 1/5] mm: Add write-protect and clean utilities for address space ranges

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Message-ID: <CAHk-=wigUfYXiizFH6tBCH0Na=L+c=k7CgXGoZjwKg4K1rNJ2Q@mail.gmail.com>
Date:   Mon, 30 Sep 2019 10:12:23 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     Thomas Hellström (VMware) 
        <thomas_os@...pmail.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Linux-MM <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>
Subject: Re: Ack to merge through DRM? WAS Re: [PATCH v2 1/5] mm: Add
 write-protect and clean utilities for address space ranges

On Mon, Sep 30, 2019 at 6:04 AM Kirill A. Shutemov <kirill@...temov.name> wrote:
>
> Have you seen page_vma_mapped_walk()? I made it specifically for rmap code
> to cover cases when a THP is mapped with PTEs. To me it's not a big
> stretch to make it cover multiple pages too.

I agree that is closer, but it does make for calling that big complex
function for every iteration step.

Of course, you are right that the callback approach is problematic
too, now that we have retpoline issues, making those very expensive.
But at least that hopefully gets fixed some day and gets to be a rare
problem.

Matter ot taste, I guess.

              Linus