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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> 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> X-Stat-Signature: wopa84ieyax64jgew1ygrf6cdx486e34 X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 7A0A2100006 X-HE-Tag: 1784562546-236443 X-HE-Meta: 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 CSZ3PGzg 2i88oMWXZ36Vxz/OKNgrKtOq4YLSzt0xsUVrlkEU1z4nDn71Q3txTeb0b30qkjVPm1IBRR2qyxvsJ9CPAxAQwooDkZ5cF5H46QnMB+pjlUmwZAYYuUM4xb/ZL7IOEkecTqFqPVETzD8uHJqIUtdWC/q9ouYqWJ5nOSGJukca27DWq2banlVaVckOdfwyPsbNsUTJDTwwp+FQ3rEn5vjRWcWzIGa930+0M/Yqt6Oh7ZKt73ClSQL+cslw/+L0yfpvA0y27Qknt1n8TxCQI1WQ8vZoxoYkIvDEEsAM9nmbXczK//EqLDWFR8nfQ/mFYPnMoKAi7KYpFEOkVur4NYo8i1lwHvbibV0AiCb4BQ3SpSyNb0LOk6dVHGFg4gr0YzLZZR3IY7lFlpourO9JRsJnjM62l8A== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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