From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-qk1-f176.google.com (mail-qk1-f176.google.com [209.85.222.176]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D3188436353 for ; Mon, 20 Jul 2026 15:49:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.222.176 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784562548; cv=none; b=XY/YbuFZN2bnWDyPFKP92FdutLYA6hXF+qQQwIRREscM/kRB1BYsxwtHW23Amc+If9dnEiV4P/s0LKjePeS2lg64ISssZZ2wrVO+vNcKxzbEO1EWzswrKSvBitmxOdb7mwJ+V9cyzX4teYkfWplcwDhPv9XhQv2RD/rg2pabuoA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784562548; c=relaxed/simple; bh=iagDN9MQzUvFfugJi8ZOtR1qNU9GWfiOIuQ/KX35R/o=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=kViGVpO/+S6fG3y9PwGrZOq4TgT5Gbrh5HHsSADhz6oiTLhlpf86LZA3bTVFrPplQz4ubtvxtgVk1Zox7SWn/fs3/Qo2r3TuUpHEHI8Ix7rbBKWz8KIK0V07QGIz5vyaTvmIhRdAAcJJgowfrZ+wK3Lrv/fx4yJj93PZUoAIIUc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=gourry.net; spf=pass smtp.mailfrom=gourry.net; dkim=pass (2048-bit key) header.d=gourry.net header.i=@gourry.net header.b=Oz6w8IK5; arc=none smtp.client-ip=209.85.222.176 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=gourry.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gourry.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gourry.net header.i=@gourry.net header.b="Oz6w8IK5" Received: by mail-qk1-f176.google.com with SMTP id af79cd13be357-92e622cc874so763066485a.0 for ; Mon, 20 Jul 2026 08:49:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gourry.net; s=google; t=1784562545; x=1785167345; darn=vger.kernel.org; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:from:to:cc:subject :date:message-id:reply-to:content-type; bh=89meaKDhwFe10Z71hE7i2nRHODsJTbsiRnn58cHYtjw=; b=Oz6w8IK5ZAwjM2E9DgdoVBHJKXQkwDwrOnCBPa/wPDQNh683mkFqvwchbawBzpersU lj++PO8JAi1kix3SYjAsQlUsF08NCuwdBpR1vVso7HCgyZixchhFEWLB4Y12JC/HIi0R tcJzqSdLBUSfu7I9EY6SvqyxvEsxpeF0wWpMep7tX2zzHUCp4xWwAm0G2qEvDLN+gwbd 9oe8mVqSlIPpWaIBQKBN5N8Zf4w90sYfSsEL+bFgyK3tUcz/X2fCWdnGFSe4WzIZHCBZ 019Em8Ep7PoOFEKMjVWIR46FF2YzLSNUe53t1BUzoOkE0Tq4/lSQ0Hd3O/tqZDu0nh/N rFlQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1784562545; x=1785167345; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=89meaKDhwFe10Z71hE7i2nRHODsJTbsiRnn58cHYtjw=; b=RWmM5odsiVkME5Nh5oml0Zq1H3gYjdw0BzzDHaoNoaskZzvo0FBsn12luPCIABdwlo zS9S0GXDIQ32PbPBSQcAoViD9YlKq15MwtpBw9JzrqVt92/+OZE6j/okfXV2IBPQFh6J zaL9kvlbIiUufQGKtd5nuYLrFwSlpRsmuKaN3/eEYr2RKhdbmnXGCAr+FMkIE7xCftZL UU80W2H3jsqxWYwERdXzYT6IoaOqYif/4ns9FhiL8I5Q8f272kZG2iewbuBVPWlZyc+D QjNZt9VjsUZapvkjTjHiwJXuH9XpV32Br1seEJwdfsrkTqgJozSEicuDfIFJ1hCMoogK HPPg== X-Forwarded-Encrypted: i=1; AHgh+RpHaZcApvmyb04/jcsvEtjci47mcOMK9d2tmXgBnGAXVLTTowaEydGiwNlQY/rMuNc72RNrc7OrR9RdgNVK@vger.kernel.org X-Gm-Message-State: AOJu0YwQGO+aQjXa12elVbUiJfysWv2R1vGrzU4nF5oiNxYhjg7+O9hl RBL8Zp8goa6ZgJ0qTB1+Il8G6rRION3nDm0WUUiyBoM10HbYJ+LH/Zyt5fGQ4uMVZBc= X-Gm-Gg: AfdE7cl6J9q5SQSHm9TgUx1U5uH3sCZ/6aPE4X0SEchYiKq+4WOsPB2BCEVtvzXVLBz aRnQm/vPGpm4gxxEeUpNXVpym/+YECo7X1gLv0r6+gMCFKMRyb5fze285TQBF0v1Oc9cv5/7ImA N4OYxz7Wc8l068ldMTeoCExZXAf9yQSK2ks6IGKSgDrVWC6W8S1FuDxuRRL84kjstRKlkOauhSK JPRoe6Mw/361Z4VgWGUTZsKaMLbwNobWrlnfwLdWz2Ymj0RtsaYEHCRpprDvTtipgMPubHTl9kb IIIDRCydnw6hfLE7xvVMMgcwq6vV1U2ffqUYm8fBIt5EcnxVEKPd1J/vDeGPPS4MoIeckgGXun0 RMEye431HgXRWspcuiCFg8K8TlZ3w2I75qzXqgzb//ODAaFelp9ZgosdtFocVV9du5lmZ1EUQU+ ap+YTaIhUDdD31FlirBb/b6/As8xBnUtZQNckjL9JnaYkt/Ghv7CTjkQyqHg== X-Received: by 2002:a05:620a:25d4:b0:930:ab28:9459 with SMTP id af79cd13be357-930b41e29bamr1533354985a.56.1784562545561; Mon, 20 Jul 2026 08:49:05 -0700 (PDT) Received: from gourry-fedora-PF4VCD3F (pool-173-79-60-52.washdc.fios.verizon.net. [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-fsdevel@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