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Tue, 06 Jan 2026 23:12:49 -0800 (PST) Received: from google.com ([2a00:79e0:2031:6:9f6a:2617:8891:93ff]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-34f5fa93ee7sm4057780a91.7.2026.01.06.23.12.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 06 Jan 2026 23:12:49 -0800 (PST) Date: Wed, 7 Jan 2026 16:12:44 +0900 From: Sergey Senozhatsky To: Yosry Ahmed Cc: Andrew Morton , Nhat Pham , Minchan Kim , Johannes Weiner , Brian Geffon , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Sergey Senozhatsky Subject: Re: [PATCH] zsmalloc: use actual object size to detect spans Message-ID: References: <20260106042507.2579150-1-senozhatsky@chromium.org> <5smqbald5bollibqjsvqw2tfngdoiiucurikdgqtz6xjb7u7vz@7p6hskoixaak> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 158C340003 X-Stat-Signature: zw3cyf86eaqwg4t7tn8h5e9jdusre8re X-Rspam-User: X-HE-Tag: 1767769970-804942 X-HE-Meta: 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 Kn5d5Fkc eICLmBQ8hhJux0jMINH9fQc9xP5R3igGGwJIyMj/OUuRd2NcR/bnnBkJ1cLUp2Mr5vffN2Q1ygnH+2za4C+tLTW2fhW99/45xY5q/mXbNb436We2UQq4KT8DPm3qpZaOZAanhOI0NXXEgY7Z9xH/Nlqi1q9C9WUnRf4O/guMvV51m+pIhYs9QnL9qVhiT7uVrndHt1pM3C/Ykdc+9QnYJbMtLHYAFAlurjjIyHCEt22XH04QPT5zDtVYbTt0CBH/xYFDsCTzdytvf3zeCQuRIrzRBeBgAR83ixn3KiK0H63ehgSnAA6NlDsCoTN+A+YaC31oJM/2/V7F02EuOGanoS9JfdbaUBAm2AIR5QE4zg47rle8= 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: A correction: On (26/01/07 14:30), Sergey Senozhatsky wrote: > > We increase the offset by 8 bytes (ZS_HANDLE_SIZE), but we still copy 48 > > bytes, even though 48 bytes includes both the object and ZS_HANDLE_SIZE. > > So we end up copying 8 bytes beyond the end of the object, which puts us > > in the next page which we should not be copying. > > Correct. We increased it twice: off +8 and mem_len +8. ^^ class->size (implicit +8) I tested your patch as is, w/o applying mine.