From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id DF102C5AD7B for ; Mon, 10 Aug 2026 08:40:25 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E13FC6B0095; Mon, 10 Aug 2026 04:40:24 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D9DB06B0096; Mon, 10 Aug 2026 04:40:24 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C666D6B0098; Mon, 10 Aug 2026 04:40:24 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 999696B0095 for ; Mon, 10 Aug 2026 04:40:24 -0400 (EDT) Received: from smtpin27.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 361161A06DA for ; Mon, 10 Aug 2026 08:40:24 +0000 (UTC) X-FDA: 85084713168.27.CB494D5 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf07.hostedemail.com (Postfix) with ESMTP id 7E3A640009 for ; Mon, 10 Aug 2026 08:40:22 +0000 (UTC) Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=JKo9vEdD; spf=pass (imf07.hostedemail.com: domain of ljs@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=ljs@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1786351222; b=lURc9C+LPKN0iepyaNLyHU44+a4m263w03tft0R/lKlBZWUA88wxGfs3pR3G2/qJwCKNyT 8aFPQ72TYNMSzYE8J9comKKwPcBp4vv8mEl3q/AZe0xt38HZkYJPxhXb0hlAHw+OZASMo3 pGjj7HQJK3NNJDdxXJvaJ9OEZevNj2o= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=JKo9vEdD; spf=pass (imf07.hostedemail.com: domain of ljs@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=ljs@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1786351222; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=pqefW5WYGaVGXBp1EcWnADXqL4SSTTp93r2Me4s4EHs=; b=WyplLP9p32feiNPbnWCPfgDAD5t0w/+M0NCdhuxV4qUp27jtHoeTaTAfIX+gMantsH4gXF F7zcWDZFKEvqf27NYf/jG0Jb5kftsXvzfAtkjFaueVKh4J/Us5DGNSQ2wnV65E7rm42iEM lSf0Wp3K5tpt0BcY0TgbnVkQOPXoanE= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 4949E41776; Mon, 10 Aug 2026 08:40:21 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 15B481F000E9; Mon, 10 Aug 2026 08:40:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786351221; bh=pqefW5WYGaVGXBp1EcWnADXqL4SSTTp93r2Me4s4EHs=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=JKo9vEdDRY9kEpH19pzoxMjPpB+BwegkZ/hk4gIse31W3/UahgMnQa9xh4JjiQFgo vyAT1sLy2fN77hi3ktVZitRAApigE7usTNwPtrxSB+xZCKedho76MmsOO/kaNwnbCG G3vVVXUDdlBbR1BRn+wmJtYxwXZyV17hCm0IC+Cr7LvHqWPryov+rSycK1U6Sf07Q1 a7K8Tx1IL6pcLFaXbOdwrOnccNyiajONZXrnTfr9FsiSjC5tGcxHcAlw+KE9+lCQDw I5B2NwM1a16Nkb4aClNBGjXSL3P4mApb8jLLnQeWlG5EA6ipQr7F/Z059iZBFNYRbF tXXNVEkrpiKjA== Date: Mon, 10 Aug 2026 09:39:47 +0100 From: "Lorenzo Stoakes (ARM)" To: Suren Baghdasaryan Cc: Andrew Morton , David Hildenbrand , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , 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 , Gregory Price , Ying Huang , Alistair Popple , Peter Xu , Xu Xin , Chengming Zhou , Arnd Bergmann , Greg Kroah-Hartman , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Sven Schnelle , Alex Deucher , Christian =?utf-8?B?S8O2bmln?= , David Airlie , Simona Vetter , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Boris Brezillon , Steven Price , Liviu Dudau , Huang Rui , Matthew Auld , Thomas =?utf-8?Q?Hellstr=C3=B6m?= , Rodrigo Vivi , Masami Hiramatsu , Oleg Nesterov , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , James Clark , Jason Gunthorpe , John Hubbard , Muchun Song , Oscar Salvador , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , Youngjun Park , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org, kvm@vger.kernel.org, linux-s390@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, intel-xe@lists.freedesktop.org, linux-perf-users@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: Re: [PATCH v4 03/20] mm: introduce linear_anon_page_index() Message-ID: References: <20260806-b4-scalable-cow-virt-pgoff-v4-0-ab318a350404@kernel.org> <20260806-b4-scalable-cow-virt-pgoff-v4-3-ab318a350404@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 7E3A640009 X-Stat-Signature: gi7ge1s6xzqn6ggfxkgi698edgnt16ze X-Rspam-User: X-HE-Tag: 1786351222-487705 X-HE-Meta: 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 xW+clTCV sqnV8Y/a7lXj5yxGaLWAZUEIfsR2BA1sJ9Jvs4rC00GEkK2QpTHSTJ8jVuDKAXf0rhsU+wIyo9AIEBSWfWnugfYJW1SKg0+e+f+2THYECM7OmXWTRwifNWUQ8uKKyNquZqBkWoniSB4sTj/MDQe46yRgR0C7KOQa0x0rFo7rtJpqTo4G0koJyAOjDTyGJEvwVXTNNhHkIF+NF9Y0UcDCcK7NbJ9W37z9w4YolJIFSxOtkqyDO9TL5wQiJpfpcccbaAsRXVo8KLr7ubom/aWYnizZGK3iSUH7xDGLWNPzsjuLk7A1AAeXAKm1UWcT3CMERd4LYDMlZ8dEu6xk71VtfmnxHlmeyw4UIIiUNyVqNNlvJxLGmkwJNuk8GNGNk0JcZFu/L/3ejC5j8ihdAyK5ROm4PZlR042VUXs5q16xlKst06Cg= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sat, Aug 08, 2026 at 05:49:48PM -0700, Suren Baghdasaryan wrote: > On Thu, Aug 6, 2026 at 1:23 PM Lorenzo Stoakes (ARM) wrote: > > > > This function provides the anonymous equivalent of linear_page_index(), > > instead offsetting based on the anonymous page offset of the VMA. > > > > It is valid only for anonymous or MAP_PRIVATE file-backed mappings, in > > other words CoW mappings. > > > > For pure anon VMAs, this will be equal to linear_page_index(). > > > > Assert that both of these invariants are true In linear_anon_page_index() > > s/In/in Ack. I ran these patches through claude several times and it didn't get this ;) the machines are not taking over just yet... Andrew - could you change this in-place? Thanks! > > diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h > > index c6fc783aaee5..0adfa6605653 100644 > > --- a/include/linux/pagemap.h > > +++ b/include/linux/pagemap.h > > @@ -1094,10 +1094,44 @@ static inline pgoff_t linear_page_delta(const struct vm_area_struct *vma, > > static inline pgoff_t linear_page_index(const struct vm_area_struct *vma, > > const unsigned long address) > > { > > - pgoff_t pgoff; > > + return linear_page_delta(vma, address) + vma_start_pgoff(vma); > > +} > > + > > +static inline pgoff_t __linear_anon_page_index(const struct vm_area_struct *vma, > > + const unsigned long address) > > +{ > > + return linear_page_delta(vma, address) + vma_start_anon_pgoff(vma); > > +} > > + > > +/** > > + * linear_anon_page_index() - Determine the absolute anonymous page offset of > > + * @address within @vma. > > + * @vma: An anonymous or MAP_PRIVATE file-backed VMA in which @address resides. > > + * @address: The address whose absolute page offset is required. > > + * > > + * This returns the anonymous page offset of @address, which is the page offset > > + * the address possessed at the time the VMA was first faulted. > > + * > > + * For anonymous mappings, this returns the same value as linear_page_index(). > > + * > > + * For MAP_PRIVATE file-backed mappings, this returns the anonymous page offset > > + * of @address, which is the page offset the address possessed at the time the > > + * VMA was first faulted. > > + * > > + * It is not valid to call this function for shared file-backed mappings. > > + * > > + * Returns: The absolute anonymous page offset of @address within @vma. > > + */ > > +static inline pgoff_t linear_anon_page_index(const struct vm_area_struct *vma, > > + const unsigned long address) > > +{ > > + const pgoff_t pgoff = __linear_anon_page_index(vma, address); > > + > > + VM_WARN_ON_ONCE(!vma_is_cow_mapping(vma)); > > As discussed off the list, this assertion works even for read-only > anon mappings because, as you said, "there's no such thing as a pure > anon mapping that is !VMA_MAYWRITE_BIT, there is no way to achieve > that." > It took me some time to see that after reading your discussion with > David at [1] and [2], and I don't think it's very intuitive. Could you > please add a comment explaining that? Maybe add a comment at > vma_is_cow_mapping() definition since you are using the same assertion > in another patch of this series? Sure will do! It is very confusing stuff (and I was duly confused also at first). To save a respin (unless there's more stuff I need to address) I will probably reply to the relevant patch with a proposed new comment. > > [1] https://lore.kernel.org/linux-mm/anBjpdMicqaGADr-@lucifer/ > [2] https://lore.kernel.org/linux-mm/anLyhaI6kW-EWk13@lucifer/ -- Cheers, Lorenzo