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 0BDABC88E46 for ; Thu, 10 Sep 2026 13:34:15 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 2462E6B0093; Thu, 10 Sep 2026 09:34:14 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 21E096B0095; Thu, 10 Sep 2026 09:34:14 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 10DB46B0096; Thu, 10 Sep 2026 09:34:14 -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 E21B06B0093 for ; Thu, 10 Sep 2026 09:34:13 -0400 (EDT) Received: from smtpin16.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 267651A053B for ; Thu, 10 Sep 2026 13:34:13 +0000 (UTC) X-FDA: 85197946386.16.13DD6EA Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf29.hostedemail.com (Postfix) with ESMTP id 603C1120009 for ; Thu, 10 Sep 2026 13:34:11 +0000 (UTC) Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=e3QGBMx4; spf=pass (imf29.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 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=1789047251; b=XXsm1023IOC7Msoe2UZOwmIClAwTUbpO40oaBtctZYdPk4tZ4bIYUJcjvIs/D+mYstJhNf BF2/OPbChM0Y61qM1YIkfzNwbwxAVlOUe4XfR9DE0ZsThUCzIUDB0EOBLfjrhCCrGoVjYC WKeyXMSsG6ee6/oCRIwIUIZStlKbd9U= ARC-Authentication-Results: i=1; imf29.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=e3QGBMx4; spf=pass (imf29.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 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=1789047251; 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=R6tbpyuljfgfZdUpmG6m3DA4a87+jb+g/2HfQLUIr5Q=; b=DqyCZ8Okoz/r+Hn6IxpRpPL9WGIgTc/hNXZIN9KvDMntTCklAbH4pKBwWnEhRbmcAW/Dkh O9LUuWM4S33i6+rV701ThBSRdwdY+Q4r7lKovSUBKiLSfKTjen0vVRqQeQKn7tpe5+LkWz vB3qQdIScRBflPoSKF4uZnH8ujS+6bs= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 96F6B439D3; Thu, 10 Sep 2026 13:34:10 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 759441F00898; Thu, 10 Sep 2026 13:34:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789047250; bh=R6tbpyuljfgfZdUpmG6m3DA4a87+jb+g/2HfQLUIr5Q=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=e3QGBMx40PqUN7AXNN5xvAZrRXc+smUA71DzaOAKCJ6G7uqdD/CedJcNXMpOGUtHV Oin5mrHtRH23KfztzB+zwG/7C1glqUgUwj6gLis2aKwn1hCcbYbcWE2YjEX8j2f0vz ITlhZYTr4l0g/wDFEPFTBYUwOyPh8Y0EXNK+44DCc11pTauxgCg3z7KF4079I7zGh4 YzbRYSmBqz6tHCTqhhCe2BLIicwyugGqTygpIr7GqAKHWqjqfAxLl3y/wcvvqr/QKt pYGbrrHMx/QLyGr4h06b4NGOBWghPeB6yFdgwKWG1AZ0cow3YJLjnuA1Ny7jRfsZFo Avx7L5fZNelJg== Message-ID: Date: Thu, 10 Sep 2026 15:33:59 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 08/12] mm/sparse: move __highest_used_section_nr handling To: "Oscar Salvador (SUSE)" Cc: Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kairui Song , Qi Zheng , Shakeel Butt , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baoquan He , Baolin Wang , Brendan Jackman , Johannes Weiner , Zi Yan , Oscar Salvador , Greg Kroah-Hartman , "Rafael J. Wysocki" , Danilo Krummrich , Jan Kiszka , Kieran Bingham , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-cxl@vger.kernel.org, driver-core@lists.linux.dev, linux-fsdevel@vger.kernel.org References: <20260909-b4-sparsemem_cleanups-v1-0-008fc8d579fe@kernel.org> <20260909-b4-sparsemem_cleanups-v1-8-008fc8d579fe@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: rspam08 X-Rspamd-Queue-Id: 603C1120009 X-Stat-Signature: fexj6twx6eeycfif6g57m4des7exf6bq X-HE-Tag: 1789047251-43593 X-HE-Meta: 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 o8FC2CNN cYidQyAoFfcODqxPaNQxjp5z2X7KwwYZqHUkGMwoDgTJg7mcwgdDBy4ELLfpxEdpPCLnxBsi+9pueY2iyqb2BDvThyzY6e8om6zxL5f86LXslWihk9sAMoNNcPRz3G/mEL3negAXBWM9N7D3EDXa4ZSEouzmcDxaDNTSLpuy9pIMbjtB5NgDPa1HfizYYUmjimCF3He8XtCii2imyYw03JT/FmpdddnQekcHf83pUnTSuAnkWpj1ryqfR2Q7ogafdBHCJOYbzM0S3pV9m4LhUhAQBhHGpubNyisWySreO5STEqzJ4rI/itKp9uw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/10/26 14:08, Oscar Salvador (SUSE) wrote: > On Thu, Sep 10, 2026 at 11:13:18AM +0200, David Hildenbrand (Arm) wrote: >> If you have something consuming __highest_used_section_nr while concurrently >> updating it, you might get torn reads/writes that mess up the value on the >> reader side. >> >> For example, mm/compaction.c consuming __highest_used_section_nr. > > Right, but I guess that if we get a 'wild' value, at least we are > guarded by online_section_nr() performing the right thing? I guess so, I was assuming the only real scenario would be us missing to process certain sections (which would usually not be the end of the world). Getting larger values is unlikely when tearing reads/writes I think. -- Cheers, David