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Subject: Re: [PATCH 4/4] mm: delay page_remove_rmap() until after the TLB has
 been flushed
From:   Nadav Amit <nadav.amit@gmail.com>
In-Reply-To: <20221108194139.57604-4-torvalds@linux-foundation.org>
Date:   Tue, 8 Nov 2022 13:05:39 -0800
Cc:     Hugh Dickins <hughd@google.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        kernel list <linux-kernel@vger.kernel.org>,
        Linux-MM <linux-mm@kvack.org>, 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>,
        David Hildenbrand <david@redhat.com>
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References: <CAHk-=wh6MxaCA4pXpt1F5Bn2__6MxCq0Dr-rES4i=MOL9ibjpg@mail.gmail.com>
 <20221108194139.57604-4-torvalds@linux-foundation.org>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Precedence: bulk

On Nov 8, 2022, at 11:41 AM, Linus Torvalds =
<torvalds@linux-foundation.org> wrote:

> When we remove a page table entry, we are very careful to only free =
the
> page after we have flushed the TLB, because other CPUs could still be
> using the page through stale TLB entries until after the flush.

The patches (all 4) look fine to me.

I mean there are minor issues here and there, like s390=E2=80=99s =
tlb_flush_rmaps()
that can have VM_WARN_ON(1);the generic tlb_flush_rmaps() that is =
missing an
empty line after the =E2=80=98page' variable definition; or perhaps =
using __bitwise
for sparse (as David pointed) =E2=80=94 but it can all be addressed =
later.