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 007A4F531C0 for ; Mon, 13 Apr 2026 18:35:15 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 2DA226B0089; Mon, 13 Apr 2026 14:35:15 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 28ACC6B00A3; Mon, 13 Apr 2026 14:35:15 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1799D6B00A4; Mon, 13 Apr 2026 14:35:15 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 06B946B0089 for ; Mon, 13 Apr 2026 14:35:15 -0400 (EDT) Received: from smtpin15.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id B5B2257AC7 for ; Mon, 13 Apr 2026 18:35:14 +0000 (UTC) X-FDA: 84654384948.15.156197A Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf11.hostedemail.com (Postfix) with ESMTP id 0424240002 for ; Mon, 13 Apr 2026 18:35:12 +0000 (UTC) Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=hSqxz1wq; spf=pass (imf11.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=1776105313; 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=emS9h9SsHUsj8hR6Z4Z7761tXh2GMkn98Pw5sqBFMdk=; b=UWJXLiv/sSH6LehUxH6XBt2aCISmVZrlH2RJkSKbqxX/gxdsct/iELUv20KUjhdlxN4OCI 0cOjgyJuN7UwYi0Soc2EneXWEOYo9HTv7oueG/djeG410ZnmErmtrjw6qlaDkJDGq6tsej t0fe9G180e2eVdY/X813nNmJdAHfEGI= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1776105313; a=rsa-sha256; cv=none; b=8Z3OHSPozEPH77pGwUWkb020sCF/b65Y2WOKSNdmoWjHrl49LDoQm3ebbuBi4sdwwK65Bb Srx/uq/BZDliOfgxnuNtTzkuQpNG+H940Ws5syjJzWhsSJmQtaXX28CeDEMIRNW7G3SQ9K EnzqOTuvWiST33LY7p7amwOLaPfCdF8= ARC-Authentication-Results: i=1; imf11.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=hSqxz1wq; spf=pass (imf11.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 (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 6562B6183C; Mon, 13 Apr 2026 18:35:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 90406C2BCAF; Mon, 13 Apr 2026 18:35:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776105312; bh=QlkC+Nb3eufRhvEx7dHbKvueJitX1g7CjlX7z9V2ABs=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=hSqxz1wqjzil05kMy/UZtG69pcoMl5JhqTFqv2BL6HlY42Gopl08qfZLvt7OIHZT5 jxGGq5iDz7HgHk4T4ssMVg6C4tlCDyWu9Q/fTjmfpXdGiXXkxkkDG8Rwnpzu92rEW/ wsIL4kt3XSvaMABjYTlARUO3gWB40dTSk7vyYoq05XMXg5WgJjgYgEDMVAo6Eizw/O 1TqrpsbRExmEIJP1Oi97IRLvGOsqoTo9BnJeLZZOYFbVx5I0s/0ra4112T34uzOnom 5ocYASrGBqDefYJy2Z293syYv5sVu9wyEXJWId5VPR2+i/igTHfY04gWAnDyqayqTJ tWerozM0ER2Gw== Message-ID: <2f092c37-95b3-4206-9866-f844273ed1bd@kernel.org> Date: Mon, 13 Apr 2026 20:35:02 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 01/49] mm/sparse: fix vmemmap accounting imbalance on memory hotplug error To: Muchun Song , Andrew Morton , Muchun Song , Oscar Salvador , Michael Ellerman , Madhavan Srinivasan Cc: Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Nicholas Piggin , Christophe Leroy , aneesh.kumar@linux.ibm.com, joao.m.martins@oracle.com, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org References: <20260405125240.2558577-1-songmuchun@bytedance.com> <20260405125240.2558577-2-songmuchun@bytedance.com> 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: <20260405125240.2558577-2-songmuchun@bytedance.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Stat-Signature: ikj39ewc9wwp6mt4io5ppmmtjsik1ajt X-Rspamd-Queue-Id: 0424240002 X-Rspam-User: X-HE-Tag: 1776105312-618886 X-HE-Meta: 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 La1b1iOk ZogUBxkK5dRCr7lDVMMXdodGy7ZLSL71QEUStxp2Rv9Z4oKpdDBG+hyLlQYZZ6a9wQ201wDo0MPDgF3bQNlZWel5+RviyfLt899vDCFfEHo8ok01o0qzhv7Zij1zAxRrRLQrV0hhQHzl5UeLWat7+uQDDvq2RdcZ2yYfpskB9pTBPTxHDpkbsJyVLVMYJkCD0Py3xSRnEchJzvS+vwmyzpdbxvdWSvk/xvErofPVy2LiCjMnnurFvmoZf9OpmLdKOvURjzDpBqwKZwbA3bASWujo93g== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/5/26 14:51, Muchun Song wrote: > In section_activate(), if populate_section_memmap() fails, the error > handling path calls section_deactivate() to roll back the state. This > approach introduces an accounting imbalance. > > Since the commit c3576889d87b ("mm: fix accounting of memmap pages"), > memmap pages are accounted for only after populate_section_memmap() > succeeds. However, section_deactivate() unconditionally decrements the > vmemmap account. Consequently, a failure in populate_section_memmap() > leads to a negative offset (underflow) in the system's vmemmap tracking. > > We can fix this by ensuring that the vmemmap accounting is incremented > immediately before checking for the success of populate_section_memmap(). > If populate_section_memmap() fails, the subsequent call to > section_deactivate() will decrement the accounting, perfectly offsetting > the increment and maintaining balance. > > Fixes: c3576889d87b ("mm: fix accounting of memmap pages") > Signed-off-by: Muchun Song > --- Can you send the revised fix separately, please? AI review flagged that recently on one of my series that touched the code, thanks for taking it off my todo list :) -- Cheers, David