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 459B8C982D0 for ; Thu, 17 Sep 2026 09:45:31 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 487386B0095; Thu, 17 Sep 2026 05:45:30 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 460296B0096; Thu, 17 Sep 2026 05:45:30 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 350856B0098; Thu, 17 Sep 2026 05:45:30 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 09D376B0095 for ; Thu, 17 Sep 2026 05:45:30 -0400 (EDT) Received: from smtpin13.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay09.hostedemail.com (Postfix) with ESMTP id A407A802C5 for ; Thu, 17 Sep 2026 09:45:27 +0000 (UTC) X-FDA: 85222771494.13.E5EB24B Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf17.hostedemail.com (Postfix) with ESMTP id E31704000A for ; Thu, 17 Sep 2026 09:45:25 +0000 (UTC) Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=PsOiXOhA; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf17.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1789638325; b=aet9WefWNyqizeuLB/38YoX93k3z/1S+bQhqXfFapN01JfNj2tq23xjuOdtQ8/eyG9nYz6 90KLJ6+Bkcm010cHtyozg8isGJPB+TJzxim+wMozlT2hRRWB/SorVWL1JRwzGzLG5Z6IXl +zbjcQc68OgCAursaefKs4D6WXW5Xvo= ARC-Authentication-Results: i=1; imf17.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=PsOiXOhA; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf17.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1789638325; 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=hlEiyYfBcgBZ76TWKmXGj0+0TR0lMPdB4pkDmKpFYnI=; b=il/Zdx8s1ufv9G8zgd9n6FJ6AbM005LpqiRuwhQC0mHW7rwkXj5Cp0ADeiyv92yUj5+L8v ET157LCV+towo0uELapTZJeM0KdeUiX0DXdOfe+Vo/rdAr6EbAe4w2oS4CScZpP0SJfNCY 7GFRqeW8jiO5U078MzF3G3gKb+o2Kkc= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 2EA1F602D1; Thu, 17 Sep 2026 09:45:25 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B321A1F00893; Thu, 17 Sep 2026 09:45:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789638324; bh=hlEiyYfBcgBZ76TWKmXGj0+0TR0lMPdB4pkDmKpFYnI=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=PsOiXOhApn42Zfm7SERnLwjOpVr1mytK2ATvjWg4avApWeoUvMYCLfLOZeFxER7Mj 0bNXhssDlY7hMTWjHTWYpqcd4MIVzjdJZUgcsGqSztD3IjSVHSVJ+foGP5SzMGSN9/ bXV8BiUExefzNgVnwygrPmASeqh3xdrPGXica0UquwskEPtdboK6JgffcoXR56M7pz hP/1S/UCsdQuHAwt6t3fMq18jfCjfxM7MMO/Kp9s60aVoRTg4X/USwa9FQjz7MeyoC MkH7MwmcCCnaZK9Oazl/T5+Snp6cIhh1ylpJZ+xJysSs1z/hdqVCxFWR7UJ1cYbn0l iej8UquDDA3ag== Message-ID: <4b2c99f6-d7c0-42a2-bf9a-e85061d53c93@kernel.org> Date: Thu, 17 Sep 2026 11:45:12 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm: implement and use vma_anon_tracked(), silence KCSAN To: "Lorenzo Stoakes (ARM)" , Kiryl Shutsemau Cc: Andrew Morton , Suren Baghdasaryan , "Liam R. Howlett" , Vlastimil Babka , Shakeel Butt , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Mike Rapoport , Michal Hocko , Xu Xin , Chengming Zhou , Jann Horn , Pedro Falcato , Rik van Riel , Harry Yoo , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , Youngjun Park , Peter Xu , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Guilherme Giacomo Simoes References: <20260910-vma-is-faulted-v2-1-e81ebc7d146b@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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: E31704000A X-Stat-Signature: sfbr6eem4khy1sw9zanmf4saj9i3sjac X-HE-Tag: 1789638325-742095 X-HE-Meta: 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 P7j+sQFU AB7BdcHH5TLCLuHV23CyCBcXYWLhn7lpugqpp7EJFLUBNtNgOj/OO/31GapBdIp9S49xyyg/xEA22EHwTYdF5dqrP69pJEnTjwQU2r9HWyuky6ZXGmwlxrUtC6GRTDhE7nDE4pts4GHqSrsz4JMwfG9CyPUrVn0LdMHiIuUWWNUcOv0qHWx1Kry04DQCH1RXDzuMa5yEusyEe921SHD7uZqOyaKB+Ko8U/2h6zzhfiAKwzmrw8B+TMY7z9bVOSpjcxqR8m1WEk21tDksiGetpnRyl+FCfp+Bgb5DhzIFOWSLaaj8J9TmYcMOX7NTBiGnwYaahzkOcnt93gAdxFjXgAvP8ICE9HwGTjytf Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/14/26 17:21, Lorenzo Stoakes (ARM) wrote: > On Thu, Sep 10, 2026 at 02:50:25PM +0100, Kiryl Shutsemau wrote: >> On Thu, Sep 10, 2026 at 02:18:35PM +0100, Lorenzo Stoakes (ARM) wrote: >>> Provide a function to abstract the common task of checking whether >>> a VMA is faulted in or not. >>> >>> A VMA or mmap lock must be held when calling this function. For an attached >>> VMA the transitions between unfaulted/faulted state are: >>> >>> Transition | VMA/mmap Lock state >>> ------------------------|----------------------------------------------- >>> unfaulted to faulted | write lock OR read lock + mm->page_table_lock >>> faulted to unfaulted | write lock >>> >>> So vma_anon_tracked() never provides a false positive (the lock precludes >>> it), but if only a read lock is held, a negative result must be re-checked >>> with mm->page_table_lock held. >>> >>> Detached VMAs cannot be concurrently manipulated as they are removed from >>> the maple tree so require no guarantees. >>> >>> Use data_race() to silence KCSAN about non-existent data races between >>> concurrent vma->anon_vma read/write on optimistic fault tests. >>> >>> Also while here, const-ify vma_is_attached(), vma_assert_stabilised() and >>> dependants. >> >> If you end up respinning anyway, this would be a natural separate >> prep patch. > > Yup will do, Pedro also asked for this! > >> >>> Finally, update the core VMA merge/split, rmap, mremap, KSM and fault >>> preparation callers which test vma->anon_vma directly to use >>> vma_anon_tracked() instead. >>> >>> Note that the lockless read in reusable_anon_vma() is doing more than >>> checking whether the VMA is faulted - it is returning the anon_vma to be >>> used on fault, so this check is not altered. >>> >>> There is one odd one out - file_backed_vma_is_retractable() - which holds >>> neither a VMA nor mmap lock and is stabilised by the file rmap lock only. >>> >>> Therefore just add a comment to explain why the direct vma->anon_vma check >>> is required. >>> >>> Reported-by: Guilherme Giacomo Simoes >>> Closes: https://lore.kernel.org/all/20260829100034.423064-1-trintaeoitogc@gmail.com/ >>> Closes: https://lore.kernel.org/all/20260909115723.528501-1-trintaeoitogc@gmail.com/ >>> Signed-off-by: Lorenzo Stoakes (ARM) >>> --- >>> v2: >>> - Renamed vma_is_faulted() to vma_anon_tracked() as per David. >> >> I don't particularly like vma_anon_tracked(), but naming is hard... > > Yeah it was a compromise because David and I disagreed on naming (again ;) > > I think vma_has_anon_rmap() is a better compromise? Yeah let's go for that. -- Cheers, David