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[173.79.60.52]) by smtp.gmail.com with ESMTPSA id af79cd13be357-930b54773fbsm912994185a.39.2026.07.20.10.26.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 20 Jul 2026 10:26:14 -0700 (PDT) Date: Mon, 20 Jul 2026 13:26:09 -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: X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: EE486100002 X-Stat-Signature: mz497g3rufeyqme1pm84cmr8etbsb6yk X-HE-Tag: 1784568375-724552 X-HE-Meta: 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 6RnJRYDu 8BMC5jZzw/pPLgbg8SCj2k8Gb8APB1ye1Xlo7EXu4BUeL6W/3OeR7eOghKlUgMwPf4tijdFGtLZ0oUE6+vm+cqy6pkdkwX8GgWZ8y3AneSAXDKm7+XDKeD1gv0s6TM0SO5VS2DpnoqTjSfsnY16fkq33fYfnlgrOC6nIWb9+qM/M30b8aNuL39zgoqT0BWFcMKDH9OBsaIrQ+YKA4P6IVN325+TKkjw7B7YKtjOiGbszMv8BwzkLknNbyhpiLXQNG5Ro97232PDcOGjmCn7/TwCJnEVz6ehcI07Q/nzKf98K5OROgsdt8LhTXhJhedSJlkP/d4JAf+/Q4x3vI71TAu3ZwUZyUfJV8eGpMV18RuxfRRirIv+PeytNhL9LdEDPHr/6kk72BDEX9Brg3yCl5tiG41w== 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 05:56:52PM +0100, Lorenzo Stoakes (ARM) wrote: > On Mon, Jul 20, 2026 at 11:49:00AM -0400, Gregory Price wrote: > > 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? > > Because the VMA gets remapped. > > If it's remapped when it's unfaulted, then virtual page offset gets updated, if > it's faulted then not. > ahhhhh the wording is just wonky then when faulted or remapped, x is... when unfaulted or unremapped, x is... instead of x is ... if unfaulted or were not remapped, otherwise... Sort of a complex combination of 3 negatives there. ~Gregory