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[173.79.60.52]) by smtp.gmail.com with ESMTPSA id af79cd13be357-930b54773fbsm894382285a.39.2026.07.20.08.49.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 20 Jul 2026 08:49:05 -0700 (PDT) Date: Mon, 20 Jul 2026 11:49:00 -0400 From: Gregory Price To: "Lorenzo Stoakes (ARM)" Cc: Andrew Morton , David Hildenbrand , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato , "Matthew Wilcox (Oracle)" , Jan Kara , Miaohe Lin , Naoya Horiguchi , Rik van Riel , Harry Yoo , Lance Yang , Kees Cook , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Usama Arif , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Ying Huang , Alistair Popple , Peter Xu , Xu Xin , Chengming Zhou , Arnd Bergmann , Greg Kroah-Hartman , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH v2 01/15] mm/vma: introduce VMA virtual page offset field and add helpers Message-ID: References: <20260720-b4-scalable-cow-virt-pgoff-v2-0-2d549757a76f@kernel.org> <20260720-b4-scalable-cow-virt-pgoff-v2-1-2d549757a76f@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260720-b4-scalable-cow-virt-pgoff-v2-1-2d549757a76f@kernel.org> On Mon, Jul 20, 2026 at 03:38:27PM +0100, Lorenzo Stoakes (ARM) wrote: > > The virtual page offset of a VMA is equal to vma->vm_start >> PAGE_SHIFT if > they are unfaulted or were not remapped, otherwise it is equal to this > value at the point of first fault. > The latter half of this description is a bit confusing. Why would the value differ from (vma->vm_start >> PAGE_SHIFT)? (because it's file backed?) It sounds like this value can change in response to an event, which makes me thing a reader could see two values across two calls? Apologies if i'm fundamentally misunderstanding something. ~Gregory