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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Sat, 9 Jan 2021 16:55:49 -0800
Message-ID: <CAHk-=wghqNywtf=sRv_5FmG=+hPGqj=KWakw34tNeoZ1wPuaHg@mail.gmail.com>
Subject: Re: [PATCH 0/1] mm: restore full accuracy in COW page reuse
To:     Andrea Arcangeli <aarcange@redhat.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Linux-MM <linux-mm@kvack.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Yu Zhao <yuzhao@google.com>, Andy Lutomirski <luto@kernel.org>,
        Peter Xu <peterx@redhat.com>,
        Pavel Emelyanov <xemul@openvz.org>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Mike Rapoport <rppt@linux.vnet.ibm.com>,
        Minchan Kim <minchan@kernel.org>,
        Will Deacon <will@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Hugh Dickins <hughd@google.com>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
        Matthew Wilcox <willy@infradead.org>,
        Oleg Nesterov <oleg@redhat.com>, Jann Horn <jannh@google.com>,
        Kees Cook <keescook@chromium.org>,
        John Hubbard <jhubbard@nvidia.com>,
        Leon Romanovsky <leonro@nvidia.com>,
        Jason Gunthorpe <jgg@ziepe.ca>, Jan Kara <jack@suse.cz>,
        Kirill Tkhai <ktkhai@virtuozzo.com>,
        Nadav Amit <nadav.amit@gmail.com>, Jens Axboe <axboe@kernel.dk>
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On Sat, Jan 9, 2021 at 4:44 PM Andrea Arcangeli <aarcange@redhat.com> wrote:
>
> Once we agree that COW page reuse requires full accuracy, [...]

You have completely and utterly ignored every single argument against that.

Instead, you just continue to push your agenda.

The thing is, GUP works fine.

COW works fine.

The thing that is broken is clear_refs.

Yet you try to now "fix" the two fine cases, because you don't want to
fix clear_refs.

What part of "clear_refs is the _least_ important of the three cases"
are you not willing to understand?

                 Linus