linux-kernel - Re: mm: delay rmap removal until after TLB flush

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Message-ID: <CAHk-=wjtqVTvR2gZx_UgxXyx3t93a6DMmW265xbp3tbJWLxK9w@mail.gmail.com>
Date:   Wed, 2 Nov 2022 16:13:02 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Gerald Schaefer <gerald.schaefer@...ux.ibm.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Will Deacon <will@...nel.org>,
        Aneesh Kumar <aneesh.kumar@...ux.ibm.com>,
        Nick Piggin <npiggin@...il.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Jann Horn <jannh@...gle.com>,
        John Hubbard <jhubbard@...dia.com>, X86 ML <x86@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Joerg Roedel <jroedel@...e.de>,
        Uros Bizjak <ubizjak@...il.com>,
        Alistair Popple <apopple@...dia.com>,
        linux-arch <linux-arch@...r.kernel.org>
Subject: Re: mm: delay rmap removal until after TLB flush

On Wed, Nov 2, 2022 at 3:31 PM Gerald Schaefer
<gerald.schaefer@...ux.ibm.com> wrote:
>
> Just wondering a bit why you did not also add the
> VM_WARN_ON_ONCE_PAGE(page_mapcount(page) < 0, page), like
> in the generic change.

Heh, I had considered dropping it entirely even from the generic code,
since I don't remember seeing that ever trigger, but PeterZ convinced
me otherwise.

For the s390 side I really wanted to keep things minimal since I
(obviously) didn't even built-test it, so..

I'm perfectly happy with s390 people adding it later, of course.

                Linus