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b=nV8roOhEKCzd0klA0IZP9b6yC8z0UOgjK1pql6YB7FfazfpFKMzc+ZEjD3UQA9YxN wvXAGypAVDyL/NPt9gnkhtW5OFTB323fmBOXep+mU/wo0ZHonXyivYrGJcvFFuTqV7 asGB7elZGV9f+v1WXmlnpJ57JWSX5WMN5a+vSlwStQFtFHsrwt8KCd2FWWr13SRgbj +7jQd6pWuGFqkx/WAQ9uJS9veNfxvM+XvmWBwlMbROJekzxbomxb4jNO2QlN6k176r FJZQKBmr3LVrikdVF9j2YsyGXy0rFTl3QyL138Q9xMBWNladqC5YJwniwRs73wxaiP pcNLKEJrO7bIw== Received: by mail-pg1-f175.google.com with SMTP id 41be03b00d2f7-5ce942efda5so5547137a12.2 for ; Thu, 25 Jan 2024 17:09:55 -0800 (PST) X-Gm-Message-State: AOJu0Yxoo4JwZxl4T1/m/VBoWujU8Fd31nlhTsJmZgCR7W5MdmzVV6y6 euvV3Imj/SXIs3uJWjsDcrj8WUfOUb+Ga60PJHOFC8fDjZEnLEyyI4KqVfh6Lk3ITjbfsBd8UHh B/gry+KUW1yhmbeePUfd9ezTpjw1+mYjJYD/e X-Google-Smtp-Source: AGHT+IFPjHIoFHpS6lUwKN2Ik89SZ4wdLjZNpBhW99q6IwgqhzpQ9EhayIgGH+gohje52GYr1BlFthvuU1QxnMZhlTk= X-Received: by 2002:a17:903:1108:b0:1d4:d5bb:5d7c with SMTP id n8-20020a170903110800b001d4d5bb5d7cmr695292plh.110.1706231394824; Thu, 25 Jan 2024 17:09:54 -0800 (PST) MIME-Version: 1.0 References: <20240120024007.2850671-1-yosryahmed@google.com> <20240120024007.2850671-3-yosryahmed@google.com> <20240122201906.GA1567330@cmpxchg.org> <20240123153851.GA1745986@cmpxchg.org> <20240123201234.GC1745986@cmpxchg.org> In-Reply-To: From: Chris Li Date: Thu, 25 Jan 2024 17:09:43 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 2/2] mm: zswap: remove unnecessary tree cleanups in zswap_swapoff() To: Yosry Ahmed Cc: Johannes Weiner , Andrew Morton , Nhat Pham , Chengming Zhou , Huang Ying , linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 9831B14001F X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: sr4yp76fjrenx1wug3gth56tm1chs549 X-HE-Tag: 1706231396-484860 X-HE-Meta: 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 eJ4h34qQ sJNbFQcTF7vCFIyj1zPBEtXC5w11iAnq/UlBHFRHl0kCAfKRxhI09KKOv4Qcl7ckfgfDIhugW5uu8kdpgNjqm6YwwQbMnf3IgKU/s2HRbTzX5SNi2IZDuGjfyLFyFiVLMuIOhvG5biYUN7ozSyCDxcZLwWIplYDGwm+JW57xQO5vPb3I3SYPMXqEYFbzaN1Qe+TPYXkJqEmsdH4EYGSY5WP/6OQJqxe8s+MMHyVRoXJSAiSB0+IXwcWK35UAJCiKQYHzDxrgQFiO6T8IvHmm3G1SF/57huasGWVNp9uHLPeGmdB/klSgc20NBkQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000003, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Yosry, On Thu, Jan 25, 2024 at 2:34=E2=80=AFPM Yosry Ahmed = wrote: > > > > problem is that after the entry is isolated from the zswap LRU, we > > > need to grab the tree lock to make sure it's still there and get a > > > ref, and just trying to lock the tree may be a UAF if we race with > > > swapoff. > > > > I feel it is very wrong to have the tree freed while having > > outstanding entry allocationed from the tree pending. > > I would want to avoid that situation if possible. > > This should be the case with Chengming's solution. Thanks for confirming. Looking forward to Chenming's patch. Chris