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 8A2DAC55184 for ; Mon, 3 Aug 2026 13:04:40 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 813726B009E; Mon, 3 Aug 2026 09:04:39 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7EB766B009F; Mon, 3 Aug 2026 09:04:39 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 703CC6B00A2; Mon, 3 Aug 2026 09:04:39 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 483D86B009E for ; Mon, 3 Aug 2026 09:04:39 -0400 (EDT) Received: from smtpin21.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay10.hostedemail.com (Postfix) with ESMTP id A7843C0682 for ; Mon, 3 Aug 2026 09:28:42 +0000 (UTC) X-FDA: 85059433284.21.B229F2E Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf04.hostedemail.com (Postfix) with ESMTP id EBCC440005 for ; Mon, 3 Aug 2026 09:28:40 +0000 (UTC) Authentication-Results: imf04.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b="W+fpwFs/"; spf=pass (imf04.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@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=1785749320; 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=hUNX++3BEUzA26hicxStbuLxQDCbIeizijI0OkQjZck=; b=J3v1QhUOQ8I7w0zGHu/S/DaSYIc/fDNf5qnjqX4nr+yJRSItbrQVb16oCdhZeu2PeGY2kj kKVv4HyItdLTMNrmEfFulwk/dlf96g3FZMujwXg3cDmG2o7TSuVMJ1HHT6v71xqX/NfMng SNuzaf2rn/Qz980IV025xi4L0GcjY8o= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1785749320; b=cfZmse8ecCx1JJ3ujQh1V5FCgTz/3QvtdP6gZm83PLj7Oziqf/ZzvFhHOZkBOi5flkBz5K qZv1nLw8Z8WgN7p7uUrfPJ7eG7k9URKwReYEnyAdpgS2kl5xGI/7UkDqeBV3im/Hqekckh uRqRc0F3l2oBpeSMYkhZHPBnqsGb9AE= ARC-Authentication-Results: i=1; imf04.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b="W+fpwFs/"; spf=pass (imf04.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 7BB4160A64; Mon, 3 Aug 2026 09:28:40 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7ED211F00A3A; Mon, 3 Aug 2026 09:28:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785749320; bh=hUNX++3BEUzA26hicxStbuLxQDCbIeizijI0OkQjZck=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=W+fpwFs/JXd5ssh7ZvqoPV4mgc6cns70ZX82HVprWFINNlekvxdEDGQYq0twhE/dB 4Nbt/63rh/mObIY9W+yhKvUJOcQjMvj7Vsgyag0DGFxrXWFn46NBCinM+2Rgyd8Bm3 nuvqJgmZX+QMcWIx5hoohcLZEG1JC9pBLOxXNrZ8ZthH1exCXltLZLXzz8QZQjko94 mba5S+VDexpjZxkcwNS3O2GNS6RbufGYkp+nMb6iJP7wSyoEsg1PGKjivG0uCHtvkq JbodFQKyDMkbGFNRhIhWlbv/RkYeyj86XbV2obzzLiaopEoV22UedVvElH0i3qEDue 0F5qBmbU65dJg== Message-ID: <2ac2746f-18b4-4960-8628-82e87c2140ce@kernel.org> Date: Mon, 3 Aug 2026 11:28:28 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 01/15] mm/vma: introduce VMA anon page offset field and add helpers To: "Lorenzo Stoakes (ARM)" , Andrew Morton , "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 , Gregory Price , Ying Huang , Alistair Popple , Peter Xu , Xu Xin , Chengming Zhou , Arnd Bergmann , Greg Kroah-Hartman Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org References: <20260729-b4-scalable-cow-virt-pgoff-v3-0-e8ecfefea812@kernel.org> <20260729-b4-scalable-cow-virt-pgoff-v3-1-e8ecfefea812@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20260729-b4-scalable-cow-virt-pgoff-v3-1-e8ecfefea812@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: EBCC440005 X-Stat-Signature: t69843cd5cmuc8u81kkddq8f5fy1idzd X-Rspam-User: X-HE-Tag: 1785749320-223745 X-HE-Meta: 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 EaSJp5qo TRvPPe1Df2eH4+sQCcaLgwxrvr7lXYHHpd0ejnITyxFa50Q3mkA/MhtcjmNOx5jymsojyIHhHXiYP9WRr5Bdny+DiW3q+tmOaxs2Ui9RnkbOi/WzK6aVWx6y3eadrL9jA5AVZaIPtOsDP9+Zfi1rNL5OsKQ6QwP/4v2g5SoHvmO43nCdcARVOlmv6N4sJU5Mseyeqz/0DDf31iSff16eq/DrNBip/kGo0+Vc2b2EflpbZdFvNyLemLlhux0vAAfG6EEvjTGcSRQgcDNG8i3GHdDKzAVGNS6Ia+TLBzu1WFFwTVb8sdnjkS4XD8X5uvN3cehDtMnpGxoW09ORO9wCbrM6RmuXYKmO48k13xd6K/KxGqzY= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/29/26 18:48, Lorenzo Stoakes (ARM) wrote: > This patch establishes fields within the vm_area_struct type to store the > anonymous page offset of VMAs. Nit: Avoid "This patch". Just say "Establish ..." (I was surprised to find that even Documentation/process/submitting-patches.rst document this) > > The anonymous 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. > > Currently, anonymous folios belonging to CoW'd MAP_PRIVATE-mapped > file-backed VMAs are tracked by their file offset. By adding anonymous > offset as a property of VMAs, we can now track them by their anonymous page > offset instead. > > By tracking this, we provide the means by which to eliminate this > inconsistency, and more importantly lay the foundations for future work for > the scalable CoW anonymous rmap rework. > > This patch simply adds the fields and some simple helpers. Subsequent > patches will update mm code to make use of these fields correctly. > > The fields chosen are packed in the VMA such that, for 64-bit kernel > builds, no additional space is taken up. > > The first field is present on cacheline 0 containing key VMA fields, and > the second on cacheline 3, which contains file-backed reverse mapping > fields. > > Given the relative time spent accessing reverse mapping fields as well as > updating them, there shouldn't be any performance impact here from false > sharing. > > Update the VMA userland tests to account for this change. > > No callsites are updated yet, so no functional change intended. > > Signed-off-by: Lorenzo Stoakes (ARM) > --- [...] > +static inline void __vma_set_anon_pgoff(struct vm_area_struct *vma, pgoff_t pgoff) > +{ > +#ifdef CONFIG_64BIT > + vma->__vm_anon_pgoff_hi = pgoff >> 32; > +#endif > + vma->__vm_anon_pgoff_lo = pgoff & GENMASK(31, 0); > +} > + > +static inline void vma_set_anon_pgoff(struct vm_area_struct *vma, pgoff_t pgoff) > +{ > + vma_assert_can_modify(vma); > + __vma_set_anon_pgoff(vma, pgoff); > +} > + > static inline void vma_add_pgoff(struct vm_area_struct *vma, pgoff_t delta) > { > vma_assert_can_modify(vma); > diff --git a/mm/vma_init.c b/mm/vma_init.c > index 715feee283f0..baa7e82f47e3 100644 > --- a/mm/vma_init.c > +++ b/mm/vma_init.c > @@ -51,6 +51,7 @@ static void vm_area_init_from(const struct vm_area_struct *src, > dest->vm_end = src->vm_end; > dest->anon_vma = src->anon_vma; > dest->vm_pgoff = vma_start_pgoff(src); > + __vma_set_anon_pgoff(dest, vma_start_anon_pgoff(src)); It would be cleaner if both interfaces would either contain "start" or not contain it. The former would be better __vma_set_start_anon_pgoff(dest, vma_start_anon_pgoff(src)); Acked-by: David Hildenbrand (Arm) -- Cheers, David