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AJvYcCWtVZ1jLNx4+E02/Hs5AouQT2sZ+VtCZCiRZ16LjDPzdXXy3ivLwzpi9AHCazgJpuMJ57UZnaiLjw==@kvack.org X-Gm-Message-State: AOJu0YzEeS/QVZcCxxGhO67ihJ1XbcP7XeN5fewUfS0iQ4RHRpxLdeVu GiQCn9Jt5eiQMujN7UEdnJdUz96eyTehOq/MpHyu4RQRvYhFFvinB4m8zbDTcDCcAjvS1HKZnT1 QzR2jc6OKTVEWhoCeRpsi9uRz0iMluQEQU9tY X-Google-Smtp-Source: AGHT+IFJF3MOvQxmk700Ff5143ZixS+E6Lj6H0zZBG81tkCepaNoLsGPC7etwa0YVohmOPEH7ZSLTVkx1hmqfi9iEdY= X-Received: by 2002:a05:6512:1307:b0:539:e436:f1d1 with SMTP id 2adb3069b0e04-53a14e6caf0mr12729e87.1.1729188453051; Thu, 17 Oct 2024 11:07:33 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Jann Horn Date: Thu, 17 Oct 2024 20:06:57 +0200 Message-ID: Subject: Re: [PATCH v1 2/7] mm: make zap_pte_range() handle full within-PMD range To: Qi Zheng Cc: david@redhat.com, hughd@google.com, willy@infradead.org, mgorman@suse.de, muchun.song@linux.dev, vbabka@kernel.org, akpm@linux-foundation.org, zokeefe@google.com, rientjes@google.com, peterx@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, x86@kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: C41BD120005 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: wexh9a3zmzjqit1xph54oou5ia46fzx6 X-HE-Tag: 1729188441-919707 X-HE-Meta: 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 a7fek3Du dl8YfvdmXW+hEONJsOBHLlHY43bjxZcX8LbhvKmwKAmOQl9Nx4IF6vn64KiXry6SAvCW44U+81r8bxkwZGocaDjAkbBU0kt4L39JTz3tf/2SSzO+U+G4JU4229NBOeNAL5ViYPVQa67uk0crv8r6DEzNSk2cdv8Jawv4y5FDq672Vl9saUr0U4KGScdRtJ2Qa/fIODY4lYWHHePBD/+fRRkr4eWbY4gSlaaL8BIGbdRcHZsqY7ikQt6AEcQBq+KA5xqHZA4AatKtEkPc= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Oct 17, 2024 at 11:48=E2=80=AFAM Qi Zheng wrote: > In preparation for reclaiming empty PTE pages, this commit first makes > zap_pte_range() to handle the full within-PMD range, so that we can more > easily detect and free PTE pages in this function in subsequent commits. I think your patch causes some unintended difference in behavior: > Signed-off-by: Qi Zheng > --- > mm/memory.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/mm/memory.c b/mm/memory.c > index caa6ed0a7fe5b..fd57c0f49fce2 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -1602,6 +1602,7 @@ static unsigned long zap_pte_range(struct mmu_gathe= r *tlb, > swp_entry_t entry; > int nr; > > +retry: This "retry" label is below the line "bool force_flush =3D false, force_break =3D false;", so I think after force_break is set once and you go through the retry path, every subsequent present PTE will again bail out and retry. I think that doesn't lead to anything bad, but it seems unintended.