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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Wed, 9 Nov 2022 13:04:07 -0800
Message-ID: <CAHk-=wiFmm+X92Ghkz_LDG53djReK=idAj0uvSdES+yeG1X=Dw@mail.gmail.com>
Subject: Re: [PATCH 4/4] mm: delay page_remove_rmap() until after the TLB has
 been flushed
To:     Hugh Dickins <hughd@google.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Nadav Amit <nadav.amit@gmail.com>,
        Will Deacon <will@kernel.org>,
        Aneesh Kumar <aneesh.kumar@linux.ibm.com>,
        Nick Piggin <npiggin@gmail.com>,
        Heiko Carstens <hca@linux.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Alexander Gordeev <agordeev@linux.ibm.com>,
        Christian Borntraeger <borntraeger@linux.ibm.com>,
        Sven Schnelle <svens@linux.ibm.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Gerald Schaefer <gerald.schaefer@linux.ibm.com>
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On Wed, Nov 9, 2022 at 12:48 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> I'm sure I messed something up in the process [...]

I hate being right.

The UP build requires a

  #ifdef CONFIG_SMP
  ..
  #endif

around the tlb_flush_rmaps() implementation in mm/mmu_gather.c, since
the UP case now shares the empty "no nothing" implementation with
s390.

I'm not going to re-send the series for that trivial fix, since nobody
is likely to actually care about UP anyway, but since I noticed it
(after sending things out, sorrt), I'll just mention it here.

And I was so happy about sharing the s390 and UP case, and avoiding
any code being specific to s390. Which is what introduced this thing.

Oh well. Easy fix. Just egg on my face. Again.

                Linus