linux-kernel - Re: [PATCH v3] mm/gup: Allow real explicit breaking of COW

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Message-ID: <CAHk-=wjn90-=s6MBerxTuP=-FVEZtR-LpoH9eenEQ3A-QfKTZw@mail.gmail.com>
Date:   Fri, 21 Aug 2020 12:06:17 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Peter Xu <peterx@...hat.com>
Cc:     Jan Kara <jack@...e.cz>, Andrea Arcangeli <aarcange@...hat.com>,
        Linux-MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Marty Mcfadden <mcfadden8@...l.gov>,
        "Maya B . Gokhale" <gokhale2@...l.gov>,
        Jann Horn <jannh@...gle.com>, Christoph Hellwig <hch@....de>,
        Oleg Nesterov <oleg@...hat.com>,
        Kirill Shutemov <kirill@...temov.name>
Subject: Re: [PATCH v3] mm/gup: Allow real explicit breaking of COW

On Fri, Aug 21, 2020 at 12:05 PM Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> Well, the fix is simple, although I don't love the magic PageKsm
> semantics that hide it from the page count.
>
> But since (a) a Ksm page is presumably normally shared (ie things like
> all zeroes) and (b) copying should always be safe, just do that.

I meant to attach the patch that did that, but didn't. Here is the
obvious modified version.

             Linus

View attachment "0001-Trial-do_wp_page-simplification.patch" of type "text/x-patch" (2872 bytes)