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 67FFFC55184 for ; Mon, 3 Aug 2026 12:52:48 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 7AC426B007B; Mon, 3 Aug 2026 08:52:47 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 75C5E6B009F; Mon, 3 Aug 2026 08:52:47 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 64BDD6B00A0; Mon, 3 Aug 2026 08:52:47 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 372D46B007B for ; Mon, 3 Aug 2026 08:52:47 -0400 (EDT) Received: from smtpin05.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 75E47A06AF for ; Mon, 3 Aug 2026 11:33:04 +0000 (UTC) X-FDA: 85059746688.05.6BEB2D4 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf10.hostedemail.com (Postfix) with ESMTP id BEDF6C0009 for ; Mon, 3 Aug 2026 11:33:02 +0000 (UTC) Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b="SttuxkJ/"; spf=pass (imf10.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-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1785756782; b=RIG9E9sXtoS8/9NlVeCuEyccA7GIRf6zMQoflgo/6gBw4DCclftuomTZAl1qAaIShdb84i aZzePhjtyTcvRwJT07V2F7ilBYz8n7d4/eFhFe9SUqUBjG9nH/xS1AlYUOiM9jxEE6D9NC 6CsEhFhXE/Iobyiz2CDgz+CfYu5sPUQ= ARC-Authentication-Results: i=1; imf10.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b="SttuxkJ/"; spf=pass (imf10.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=1785756782; 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=ZdkYkZfcV13Rm76AHyDXctAB6jChiddr7RTO+n76n64=; b=iOtj/qNz/0fGkq9qSw45NmJv+bCkbALvQfY4hnU6q+o4NMcbC5Wk46sE46ukmHOE5eXirq qbSzAIxN7qGmTglEHAVpPL+vPGG+FbNHrPHRB1jrIePJWnqCTR/6d2j/8m3Fql3o4DnA1J zvgHHCfCf76iWdYmufPsNRKNzuBwmME= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 53D3360A78; Mon, 3 Aug 2026 11:33:02 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 560C51F00A3A; Mon, 3 Aug 2026 11:32:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785756782; bh=ZdkYkZfcV13Rm76AHyDXctAB6jChiddr7RTO+n76n64=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=SttuxkJ/o74K45+6zlwW1rejwGDsKpDF91iLL81a11ij5Ult+WrfH+5LI51Ybr3wK 1wqUG75oERvglx5vVielESYfP5TTjDkm6+pY6B4+aYC3rIlhgztLQOMcFKZcsKK661 yT0qz6VnJElKTTvYXQ0L6f1AVQC3lc61PakAIFTnzL9xS0jUmFL/GMWR1q9pIIfZ9q 3w3M9rEiHWxklbgu1qstWXa41n1GN/pusx5mE8eLqYKfRncMwHRwHMaJhDvLPMSOJT ln3QAdZ9d7yutDSCaNk+Yx9qNMfG/wvLqPW7gfofin7DjO4ti3tn8QfWqBU3rFkZyR hKqzjMSANV0bw== Message-ID: <5dcf29d5-2fb4-4550-a3e9-a39645d736c8@kernel.org> Date: Mon, 3 Aug 2026 13:32:50 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 09/15] mm/rmap: use anon pgoff to track MAP_PRIVATE file-backed anon folios 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-v3-9-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-v3-9-e8ecfefea812@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: au4hs1nurmm6jeagn5sos9fkh45pta16 X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: BEDF6C0009 X-Rspam-User: X-HE-Tag: 1785756782-179246 X-HE-Meta: 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 MRfpBIsW 8M7HpaT8POf6IN8doIvyArxTDPsqnGDplrve6UpStyGWOV6eMF+rmHRPQGODKCL3WPWPZaTEmrJAmq4eRF7xrj2nWIZjxRg9zg2VfpQPMM9DMdRp430DKNwsNE8iUKcwq5fxg5068fX49EEHwheZ14Dzm0eH5XY+8FY4dA02rtlttQTW0KsCsRfizX0z328bftHdHVyR44sZkYmdpiATJuC96EMIT7PAm9m86dQcA2xYY0VjoBC7DfxmYc9uc8M3DqPAlZ4yYCHi6IlS/KgkpXAW18otziy4R0E4UzER7VJMSrMaNUDjdko/AM0yfn0WgaMJIh44uh0JSZ9wx3CxTXGKmNjKb/4Xcd2s2sz088uGh83XsUx4lZU2oCqzfKGh1//Lh 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: > Currently anonymous folios belonging to CoW'd MAP_PRIVATE file-backed > mappings are indexed by their page offset within the file in which they > were originally mapped. > > This differs from anonymous folios belonging to pure anon mappings which > are indexed by their anonymous page offset (the address at which they'd > belong in the VMA when first faulted). > > This change fixes this inconsistency, always indexing anonymous folios by > their anonymous page offset regardless of the VMA to which they belong. > Yes, this is great. > The foundations have been laid such that we need only switch this > functionality on such by: > > * Using linear_anon_page_index() in __folio_set_anon() to assign the > folio's index to the anonymous linear index rather than the file-backed > one. > > * Otherwise using linear_anon_page_index() in all instances where > anonymous folios are being referenced or manipulated. > > * Replacing vma_address() with vma_filebacked_address() or > vma_anon_address() as appropriate. > > * Updating the merging logic to check that anonymous page offsets are > aligned as well as filebacked ones for MAP_PRIVATE file-backed VMAs, > introducing needs_adjacent_anon_pgoff() to figure out when this is > required. > > * Updating linear_folio_page_index() to invoke linear_anon_page_index() > if the folio is anonymous. > > * Updating vma_address_end() to use the VMA's anonymous page offset when > pvmw->pgoff is anonymous. > > * Correcting folio_within_range() to use anonymous page offset for > anonymous folios. > > This will have no impact on merging of anonymous VMAs, whose page offset > and anonymous page offset are identical, nor will it impact shared > file-backed VMAs, which will continue to be merged based on the file-backed > page offset. > > However, MAP_PRIVATE file-backed mappings must now be aligned on anonymous > page offset as well. > > In most instances this should have no impact on merging of file-backed > mappings, which are usually not merged all that often, let alone > MAP_PRIVATE mapped ones, and rarely remapped and faulted before being moved > back in place (the case in which a merge may now fail). Agreed. [...] > > /** > - * vma_address - Find the virtual address a page range is mapped at. > - * @vma: The vma which maps this object. > - * @pgoff: The page offset within its object. > - * @nr_pages: The number of pages to consider. > - * > - * If any page in this range is mapped by this VMA, return the first address > - * where any of these pages appear. Otherwise, return -EFAULT. > - */ > -static inline unsigned long vma_address(const struct vm_area_struct *vma, > - pgoff_t pgoff, unsigned long nr_pages) > -{ > - return __vma_address(vma, pgoff, vma_start_pgoff(vma), nr_pages); > -} Good to see this go. [...] > rmap_item->anon_vma = vma->anon_vma; > - rmap_item->linear_page_index = linear_page_index(vma, rmap_item->address); > + /* The VMA is always anon/MAP_PRIVATE-file backed so use anon index. */ > + rmap_item->linear_page_index = linear_anon_page_index(vma, rmap_item->address); You can drop this comment: It's an anon_vma + linear_page_index pair, so the anon_page_index is implied. [...] > WRITE_ONCE(folio->mapping, (struct address_space *) anon_vma); > - folio->index = linear_page_index(vma, address); > + folio->index = linear_anon_page_index(vma, address); Apart from the LGTM. -- Cheers, David