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b=0G/0Jcyby3mLtIFfRj9YYzME6z+ZmSLTmcxgR0x5iTwgW5ZoRT7thYuOiq5Poa92+ UKxQTOlPKsnhIe7GDmY8oWUEVEs+M6UrqvfFDzluqf1zlFHKGeF8/2qfiLQRBXh5WJ uREfa7XESaC18PPOPJ8HgXzYoGcELmuXx3bjO+6w= Date: Mon, 31 Aug 2026 17:12:05 -0700 From: Andrew Morton To: Sarthak Sharma Cc: David Hildenbrand , Jason Gunthorpe , John Hubbard , Peter Xu , Kiryl Shutsemau , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] mm/gup_test: report actual pinned bytes Message-Id: <20260831171205.9463e83d82da2a0b403da26a@linux-foundation.org> In-Reply-To: <20260831101304.162867-1-sarthak.sharma@arm.com> References: <20260831101304.162867-1-sarthak.sharma@arm.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: bkzoty6dn4zh9e5m46ejht5prfckjwyc X-Rspamd-Queue-Id: DFCC640010 X-Rspamd-Server: rspam02 X-Rspam-User: X-HE-Tag: 1788221527-327686 X-HE-Meta: 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 z0hD1o1s +xh6qZE/KVZnLlNG1kMlp9GMlSWd6tpBIdw3CLp4+uBZyoMVNMlcKj0ZigmpauO5suYaLsU79HOzCNyTMcDV1W9jv1jIg9dlKNHjf50XbRtfrdFONWhp61lihLoU85cVGkT7iSTDKTuyjPAVMCCBuGzp79b6PWRFsit86PpnpwmxWWW+cVL8vLYhZGGSAjr0pJHhEd+XRIGYZ6Lxmhr7hXESQPueVeUjUbiCn/NrlZVJRKIYaBcdGhikchnTOhjB5naeSlG2N6wI07EVxQ7OJv4V8D73kdpz1d+rvRYLV80wRYmELF5WyZ6vSo9j69ctuj7SMjlgkHhFU+tFIwaR33uoBDZJb8XeWSXJ8+hzG1bDUu6welJV0JnOuVNu8keXHvn+Zj6XJJDrUGxd5heBW72rk27gQQGiuPpeUNistL8L3wUfm7VeJ3TPRl6WuhlMhbco01yZ3fQOu8h9+8tHJtjV/9w== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, 31 Aug 2026 15:43:04 +0530 Sarthak Sharma wrote: > __gup_test_ioctl() advances addr to the end of the current batch before > checking if GUP pinned the entire requested batch. If GUP pins more than > 0 pages but less than the requested batch size, addr still advances by > the requested batch size. > > The next iteration detects the partial pinning and breaks out of the loop. > Again gup->size is calculated using addr - gup->addr, so it also includes > the unpinned pages of the requested batch. > > Calculate gup->size using the actual number of pages pinned multiplied > by PAGE_SIZE. Thanks. Sashiko might have found a somewhat-related overflow on 32-bit. Maybe fix that while we're in there? https://sashiko.dev/#/patchset/20260831101304.162867-1-sarthak.sharma@arm.com