[{"id":3681367,"web_url":"http://patchwork.ozlabs.org/comment/3681367/","msgid":"<1cbae635-a115-4270-bae2-64145d16f936@kernel.org>","date":"2026-04-23T10:40:25","subject":"Re: [PATCH v5 v5 4/6] mm/sparse-vmemmap: Fix DAX vmemmap accounting\n with optimization","submitter":{"id":92023,"url":"http://patchwork.ozlabs.org/api/people/92023/","name":"David Hildenbrand (Arm)","email":"david@kernel.org"},"content":"On 4/23/26 09:19, Muchun Song wrote:\n> When vmemmap optimization is enabled for DAX, the nr_memmap_pages\n> counter in /proc/vmstat is incorrect. The current code always accounts\n> for the full, non-optimized vmemmap size, but vmemmap optimization\n> reduces the actual number of vmemmap pages by reusing tail pages. This\n> causes the system to overcount vmemmap usage, leading to inaccurate\n> page statistics in /proc/vmstat.\n> \n> Fix this by introducing section_vmemmap_pages(), which returns the exact\n> vmemmap page count for a given pfn range based on whether optimization\n> is in effect.\n> \n> Fixes: 15995a352474 (\"mm: report per-page metadata information\")\n> Signed-off-by: Muchun Song \n> Acked-by: Mike Rapoport (Microsoft) \n> Acked-by: Oscar Salvador \n> ---\n> mm/sparse-vmemmap.c | 31 +++++++++++++++++++++++++++----\n> 1 file changed, 27 insertions(+), 4 deletions(-)\n> \n> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c\n> index 3340f6d30b01..979d71158c9b 100644\n> --- a/mm/sparse-vmemmap.c\n> +++ b/mm/sparse-vmemmap.c\n> @@ -652,6 +652,28 @@ void offline_mem_sections(unsigned long start_pfn, unsigned long end_pfn)\n> \t}\n> }\n> \n> +static int __meminit section_nr_vmemmap_pages(unsigned long pfn, unsigned long nr_pages,\n> +\t\tstruct vmem_altmap *altmap, struct dev_pagemap *pgmap)\n> +{\n> +\tconst unsigned int order = pgmap ? pgmap->vmemmap_shift : 0;\n> +\tconst unsigned long pages_per_compound = 1UL << order;\n> +\n> +\tVM_WARN_ON_ONCE(!IS_ALIGNED(pfn | nr_pages, pages_per_compound));\n> +\tVM_WARN_ON_ONCE(!IS_ALIGNED(pfn | nr_pages, PAGES_PER_SECTION));\n\nThinking about the PAGES_PER_SECTION, can't we get called for sub-sections?","headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linuxppc-dev@lists.ozlabs.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256\n header.s=k20201202 header.b=SyDXjw67;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=lists.ozlabs.org\n (client-ip=2404:9400:21b9:f100::1; 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Howlett\" ,\n Vlastimil Babka , Mike Rapoport ,\n Suren Baghdasaryan , Michal Hocko ,\n Nicholas Piggin , Christophe Leroy ,\n aneesh.kumar@linux.ibm.com, joao.m.martins@oracle.com, linux-mm@kvack.org,\n linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org","References":"<20260423071911.1962859-1-songmuchun@bytedance.com>\n <20260423071911.1962859-5-songmuchun@bytedance.com>","From":"\"David Hildenbrand (Arm)\" ","Content-Language":"en-US","Autocrypt":"addr=david@kernel.org; keydata=\n xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ\n dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL\n QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp\n XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK\n Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9\n PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt\n WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc\n UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv\n jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb\n B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk\n ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik\n AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN\n 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD\n g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz\n ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x\n 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7\n /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4\n jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ\n DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R\n HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC\n 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7\n LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR\n 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt\n VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk\n /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy\n iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ\n 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21\n zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg\n azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY\n FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D\n sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO\n 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e\n EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts\n IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC\n 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV\n Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS\n sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx\n yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9\n 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg\n r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ\n 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ\n CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY\n qIws/H2t","In-Reply-To":"<20260423071911.1962859-5-songmuchun@bytedance.com>","Content-Type":"text/plain; charset=UTF-8","Content-Transfer-Encoding":"7bit","X-Spam-Status":"No, score=-0.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED,\n\tDKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,SPF_HELO_NONE,SPF_PASS\n\tautolearn=disabled version=4.0.1 OzLabs 8","X-Spam-Checker-Version":"SpamAssassin 4.0.1 (2024-03-25) on lists.ozlabs.org"}},{"id":3681413,"web_url":"http://patchwork.ozlabs.org/comment/3681413/","msgid":"<1ADE7CE5-F02D-42B2-B7AC-FE0D6E86042D@linux.dev>","date":"2026-04-23T12:04:21","subject":"Re: [PATCH v5 v5 4/6] mm/sparse-vmemmap: Fix DAX vmemmap accounting\n with optimization","submitter":{"id":84878,"url":"http://patchwork.ozlabs.org/api/people/84878/","name":"Muchun Song","email":"muchun.song@linux.dev"},"content":"> On Apr 23, 2026, at 18:40, David Hildenbrand (Arm) wrote:\n> \n> On 4/23/26 09:19, Muchun Song wrote:\n>> When vmemmap optimization is enabled for DAX, the nr_memmap_pages\n>> counter in /proc/vmstat is incorrect. The current code always accounts\n>> for the full, non-optimized vmemmap size, but vmemmap optimization\n>> reduces the actual number of vmemmap pages by reusing tail pages. This\n>> causes the system to overcount vmemmap usage, leading to inaccurate\n>> page statistics in /proc/vmstat.\n>> \n>> Fix this by introducing section_vmemmap_pages(), which returns the exact\n>> vmemmap page count for a given pfn range based on whether optimization\n>> is in effect.\n>> \n>> Fixes: 15995a352474 (\"mm: report per-page metadata information\")\n>> Signed-off-by: Muchun Song \n>> Acked-by: Mike Rapoport (Microsoft) \n>> Acked-by: Oscar Salvador \n>> ---\n>> mm/sparse-vmemmap.c | 31 +++++++++++++++++++++++++++----\n>> 1 file changed, 27 insertions(+), 4 deletions(-)\n>> \n>> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c\n>> index 3340f6d30b01..979d71158c9b 100644\n>> --- a/mm/sparse-vmemmap.c\n>> +++ b/mm/sparse-vmemmap.c\n>> @@ -652,6 +652,28 @@ void offline_mem_sections(unsigned long start_pfn, unsigned long end_pfn)\n>> }\n>> }\n>> \n>> +static int __meminit section_nr_vmemmap_pages(unsigned long pfn, unsigned long nr_pages,\n>> +\tstruct vmem_altmap *altmap, struct dev_pagemap *pgmap)\n>> +{\n>> + \tconst unsigned int order = pgmap ? pgmap->vmemmap_shift : 0;\n>> + \tconst unsigned long pages_per_compound = 1UL << order;\n>> +\n>> + \tVM_WARN_ON_ONCE(!IS_ALIGNED(pfn | nr_pages, pages_per_compound));\n>> + \tVM_WARN_ON_ONCE(!IS_ALIGNED(pfn | nr_pages, PAGES_PER_SECTION));\n> \n> Thinking about the PAGES_PER_SECTION, can't we get called for sub-sections?\n\nOh, I see. My apologies—I just remembered why I took the minimum of\npages_per_compound and PAGES_PER_SECTION in the previous version v4:\nit was specifically to support subsections.\n\nIn the last version, when I was addressing your suggestions/questions,\nI forgot about this underlying logic and simplified it to two lines.\nOf course, that’s on me, not you.\n\nAh, looks like I need to update the patch to fix this.\n\nMuchun,\nThanks.\n\n> \n> -- \n> Cheers,\n> \n> David","headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linuxppc-dev@lists.ozlabs.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256\n header.s=key1 header.b=loE9WOAK;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=lists.ozlabs.org\n (client-ip=2404:9400:21b9:f100::1; helo=lists.ozlabs.org;\n envelope-from=linuxppc-dev+bounces-20006-incoming=patchwork.ozlabs.org@lists.ozlabs.org;\n receiver=patchwork.ozlabs.org)","lists.ozlabs.org;\n arc=none smtp.remote-ip=91.218.175.177","lists.ozlabs.org;\n dmarc=pass (p=none dis=none) header.from=linux.dev","lists.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256\n header.s=key1 header.b=loE9WOAK;\n\tdkim-atps=neutral","lists.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=linux.dev\n (client-ip=91.218.175.177; 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lists.ozlabs.org;\n dmarc=pass (p=none dis=none) header.from=linux.dev; dkim=pass (1024-bit key;\n unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256\n header.s=key1 header.b=loE9WOAK; dkim-atps=neutral;\n spf=pass (client-ip=91.218.175.177; helo=out-177.mta0.migadu.com;\n envelope-from=muchun.song@linux.dev;\n receiver=lists.ozlabs.org) smtp.mailfrom=linux.dev","Content-Type":"text/plain;\n\tcharset=utf-8","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1;\n\tt=1776945907;\n\th=from:from:reply-to:subject:subject:date:date:message-id:message-id:\n\t to:to:cc:cc:mime-version:mime-version:content-type:content-type:\n\t content-transfer-encoding:content-transfer-encoding:\n\t in-reply-to:in-reply-to:references:references;\n\tbh=r2ijiexG6FD3eVhJKFQEv8cSP6rYZ0EZ6ENNdT32YGY=;\n\tb=loE9WOAKvvpSicNxVCnhTWQ4U0StHn5NBmnVSl5HthVRJaAX8DQNdOjl3sOEec+wJmyBYR\n\t1I3Zw2WfbSOPvDxPo108yOvJgV+wKg5hjlhLbbMfR3YdbIw5ptwEft6Vu75oO/LqQ7QLk6\n\tGK737O+gWWCesjjYSz+fM9tScT+YnzI=","X-Mailing-List":"linuxppc-dev@lists.ozlabs.org","List-Id":"","List-Help":"","List-Owner":"","List-Post":"","List-Archive":",\n ","List-Subscribe":",\n ,\n ","List-Unsubscribe":"","Precedence":"list","Mime-Version":"1.0 (Mac OS X Mail 16.0 \\(3864.500.181\\))","Subject":"Re: [PATCH v5 v5 4/6] mm/sparse-vmemmap: Fix DAX vmemmap accounting\n with optimization","X-Report-Abuse":"Please report any abuse attempt to abuse@migadu.com and\n include these headers.","From":"Muchun Song ","In-Reply-To":"<1cbae635-a115-4270-bae2-64145d16f936@kernel.org>","Date":"Thu, 23 Apr 2026 20:04:21 +0800","Cc":"Muchun Song ,\n Andrew Morton ,\n Oscar Salvador ,\n Michael Ellerman ,\n Madhavan Srinivasan ,\n Lorenzo Stoakes ,\n \"Liam R . Howlett\" ,\n Vlastimil Babka ,\n Mike Rapoport ,\n Suren Baghdasaryan ,\n Michal Hocko ,\n Nicholas Piggin ,\n Christophe Leroy ,\n aneesh.kumar@linux.ibm.com,\n joao.m.martins@oracle.com,\n linux-mm@kvack.org,\n linuxppc-dev@lists.ozlabs.org,\n linux-kernel@vger.kernel.org","Content-Transfer-Encoding":"quoted-printable","Message-Id":"<1ADE7CE5-F02D-42B2-B7AC-FE0D6E86042D@linux.dev>","References":"<20260423071911.1962859-1-songmuchun@bytedance.com>\n <20260423071911.1962859-5-songmuchun@bytedance.com>\n <1cbae635-a115-4270-bae2-64145d16f936@kernel.org>","To":"\"David Hildenbrand (Arm)\" ","X-Migadu-Flow":"FLOW_OUT","X-Spam-Status":"No, score=-0.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID,\n\tDKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_LOW,SPF_HELO_PASS,SPF_PASS\n\tautolearn=disabled version=4.0.1 OzLabs 8","X-Spam-Checker-Version":"SpamAssassin 4.0.1 (2024-03-25) on lists.ozlabs.org"}},{"id":3681430,"web_url":"http://patchwork.ozlabs.org/comment/3681430/","msgid":"<20260423053237.a44b68034673bb35a1e042cd@linux-foundation.org>","date":"2026-04-23T12:32:37","subject":"Re: [PATCH v5 v5 4/6] mm/sparse-vmemmap: Fix DAX vmemmap accounting\n with optimization","submitter":{"id":107,"url":"http://patchwork.ozlabs.org/api/people/107/","name":"Andrew Morton","email":"akpm@linux-foundation.org"},"content":"On Thu, 23 Apr 2026 20:04:21 +0800 Muchun Song wrote:\n\n> Ah, looks like I need to update the patch to fix this.\n\nOK. Please have a think about which patches we should backport into\n-stable. Possibly all 6! And the timing of this backport.\n\nIdeally, split the series up into one series for 7.1-rcX+stable, another\nseries for 7.2.rc1.","headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linuxppc-dev@lists.ozlabs.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=linux-foundation.org header.i=@linux-foundation.org\n header.a=rsa-sha256 header.s=korg header.b=1tmWKztb;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=lists.ozlabs.org\n (client-ip=2404:9400:21b9:f100::1; helo=lists.ozlabs.org;\n envelope-from=linuxppc-dev+bounces-20011-incoming=patchwork.ozlabs.org@lists.ozlabs.org;\n receiver=patchwork.ozlabs.org)","lists.ozlabs.org;\n arc=none smtp.remote-ip=172.105.4.254","lists.ozlabs.org;\n dmarc=none (p=none dis=none) header.from=linux-foundation.org","lists.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=linux-foundation.org header.i=@linux-foundation.org\n header.a=rsa-sha256 header.s=korg header.b=1tmWKztb;\n\tdkim-atps=neutral","lists.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=linux-foundation.org\n (client-ip=172.105.4.254; helo=tor.source.kernel.org;\n envelope-from=akpm@linux-foundation.org; receiver=lists.ozlabs.org)"],"Received":["from lists.ozlabs.org (lists.ozlabs.org\n [IPv6:2404:9400:21b9:f100::1])\n\t(using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)\n\t key-exchange x25519)\n\t(No client certificate requested)\n\tby legolas.ozlabs.org (Postfix) with ESMTPS id 4g1b8Z11xlz1yD5\n\tfor ; Thu, 23 Apr 2026 22:32:45 +1000 (AEST)","from boromir.ozlabs.org (localhost [127.0.0.1])\n\tby lists.ozlabs.org (Postfix) with ESMTP id 4g1b8Y3M5Lz2yGf;\n\tThu, 23 Apr 2026 22:32:45 +1000 (AEST)","from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254])\n\t(using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)\n\t key-exchange x25519)\n\t(No client certificate requested)\n\tby lists.ozlabs.org (Postfix) with ESMTPS id 4g1b8S6clhz2y8d\n\tfor ; Thu, 23 Apr 2026 22:32:40 +1000 (AEST)","from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58])\n\tby tor.source.kernel.org (Postfix) with ESMTP id AD58860123;\n\tThu, 23 Apr 2026 12:32:38 +0000 (UTC)","by smtp.kernel.org (Postfix) with ESMTPSA id C94F9C2BCAF;\n\tThu, 23 Apr 2026 12:32:37 +0000 (UTC)"],"ARC-Seal":"i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1776947565;\n\tcv=none;\n b=LuFxgufxCZum5q3tPUAVHylRW0F5KC12ePowV9b1SYdPhw1mVbOmkGcDuzxONkQTp5ectgfZNIzJIxL8Vcx0rpJUeUwzwmud/+REh5fGJCPk6hfilKx9pTrzDtsHoGh39dsoEFunamnLk9Iew2zSK99AjPSpgg6k6ai/0gq3K7/dJT2PBIdxMPD6R8+h0X0dHqEeE4/7m/Tsz4rZ7d2p6S9mvzMeKfw4Ui3pLzWumJCCp1O9h6FrPcpZHles8BCQ19f6xwgYeAmFGNHuSvlRWzU7po4bryFyWAJMPwuIhuokpwH1C/jw8ZBqg36yiXMVhff+JtJB8qiBTY/YlUPwew==","ARC-Message-Signature":"i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707;\n\tt=1776947565; c=relaxed/relaxed;\n\tbh=0Sm1+HBnujx7eaCDOZfyNeyN8WHlWDXXHQPnbPCVZFY=;\n\th=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References:\n\t Mime-Version:Content-Type;\n b=Due//mmig3JFpfGnchbwG2twA5Fm100k0uxUWwg7Y7B5d3nDUZB5kIQeCiKcuQTZlNVT5PPcsyysMZoofKo5j6C6maQhwDvKEjSofWFWxQYZXA6MmNVxqqvsW3YfjSSRefUwa5sXzy6L5NxCKuzFvlfp7w2xMhFQ+fdml92OE4BxcDUv8NE3SKkWYcyODXXvC371/xIUURjzVhlPdh3rEjaOJK/RZ3+Bc3R4f0e6PO/CyzlwVkLkB9m3ioV4leWVb476IDLYpWr0EAuztS9jmSHvv+a7ZNXKOV7t2RNnRE8Gd8VMJhTiqIvPTIXWnQjAgMUn9ajLrFPTaG+ZPyqJQw==","ARC-Authentication-Results":"i=1; lists.ozlabs.org;\n dmarc=none (p=none dis=none) header.from=linux-foundation.org;\n dkim=pass (1024-bit key;\n unprotected) header.d=linux-foundation.org header.i=@linux-foundation.org\n header.a=rsa-sha256 header.s=korg header.b=1tmWKztb; dkim-atps=neutral;\n spf=pass (client-ip=172.105.4.254; helo=tor.source.kernel.org;\n envelope-from=akpm@linux-foundation.org;\n receiver=lists.ozlabs.org) smtp.mailfrom=linux-foundation.org","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org;\n\ts=korg; t=1776947558;\n\tbh=mLO1y63KeITgQnUtuuXUB7kwisFayIJWJCkn+Pp4dzQ=;\n\th=Date:From:To:Cc:Subject:In-Reply-To:References:From;\n\tb=1tmWKztbTYs2a2lnZ2W3wKk0ddFcrR5tPBvRW6LZjbenwsnC6sxbXDaVDkLHtFIK2\n\t Q2FcV7i7E/VourF3CDjnZlCSvecYn6y/hnNfmlw1JVnSBIE+iCAcKf6mXAWx9SbzO5\n\t DaBWiDwSdF6pPLaoxg5Hkf04poOAtzQymmkk++/I=","Date":"Thu, 23 Apr 2026 05:32:37 -0700","From":"Andrew Morton ","To":"Muchun Song ","Cc":"\"David Hildenbrand (Arm)\" , Muchun Song\n , Oscar Salvador , Michael\n Ellerman , Madhavan Srinivasan ,\n Lorenzo Stoakes , \"Liam R . Howlett\"\n , Vlastimil Babka , Mike\n Rapoport , Suren Baghdasaryan , Michal\n Hocko , Nicholas Piggin , Christophe\n Leroy , aneesh.kumar@linux.ibm.com,\n joao.m.martins@oracle.com, linux-mm@kvack.org,\n linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org","Subject":"Re: [PATCH v5 v5 4/6] mm/sparse-vmemmap: Fix DAX vmemmap accounting\n with optimization","Message-Id":"<20260423053237.a44b68034673bb35a1e042cd@linux-foundation.org>","In-Reply-To":"<1ADE7CE5-F02D-42B2-B7AC-FE0D6E86042D@linux.dev>","References":"<20260423071911.1962859-1-songmuchun@bytedance.com>\n\t<20260423071911.1962859-5-songmuchun@bytedance.com>\n\t<1cbae635-a115-4270-bae2-64145d16f936@kernel.org>\n\t<1ADE7CE5-F02D-42B2-B7AC-FE0D6E86042D@linux.dev>","X-Mailer":"Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu)","X-Mailing-List":"linuxppc-dev@lists.ozlabs.org","List-Id":"","List-Help":"","List-Owner":"","List-Post":"","List-Archive":",\n ","List-Subscribe":",\n ,\n ","List-Unsubscribe":"","Precedence":"list","Mime-Version":"1.0","Content-Type":"text/plain; charset=US-ASCII","Content-Transfer-Encoding":"7bit","X-Spam-Status":"No, score=-0.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID,\n\tDKIM_VALID_AU,DKIM_VALID_EF,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS\n\tautolearn=disabled version=4.0.1 OzLabs 8","X-Spam-Checker-Version":"SpamAssassin 4.0.1 (2024-03-25) on lists.ozlabs.org"}},{"id":3681446,"web_url":"http://patchwork.ozlabs.org/comment/3681446/","msgid":"","date":"2026-04-23T12:43:02","subject":"Re: [PATCH v5 v5 4/6] mm/sparse-vmemmap: Fix DAX vmemmap accounting\n with optimization","submitter":{"id":84878,"url":"http://patchwork.ozlabs.org/api/people/84878/","name":"Muchun Song","email":"muchun.song@linux.dev"},"content":"> On Apr 23, 2026, at 20:32, Andrew Morton wrote:\n> \n> On Thu, 23 Apr 2026 20:04:21 +0800 Muchun Song wrote:\n> \n>> Ah, looks like I need to update the patch to fix this.\n> \n> OK. Please have a think about which patches we should backport into\n> -stable. Possibly all 6! And the timing of this backport.\n\nIn theory, I think all of these require backporting, and each carries a certain\nlevel of potential impact.\n\n> \n> Ideally, split the series up into one series for 7.1-rcX+stable, another\n> series for 7.2.rc1.\n\nGiven that these issues have existed for a long time and the trigger\nfrequency is very low, I suggest we take a more conservative timing.\n\nWe can prioritize getting the series into 7.2-rc1 first. Once they have\n'baked' in the mainline for a while without issues, we can then proceed\nwith the backport to -stable (7.1.x). This avoids rushing risky changes\ninto stable branches.\n\nThanks,\nMuchun","headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linuxppc-dev@lists.ozlabs.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256\n header.s=key1 header.b=eCIMj6Zf;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=lists.ozlabs.org\n (client-ip=2404:9400:21b9:f100::1; helo=lists.ozlabs.org;\n envelope-from=linuxppc-dev+bounces-20013-incoming=patchwork.ozlabs.org@lists.ozlabs.org;\n receiver=patchwork.ozlabs.org)","lists.ozlabs.org;\n arc=none smtp.remote-ip=91.218.175.181","lists.ozlabs.org;\n dmarc=pass (p=none dis=none) header.from=linux.dev","lists.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256\n header.s=key1 header.b=eCIMj6Zf;\n\tdkim-atps=neutral","lists.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=linux.dev\n (client-ip=91.218.175.181; 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lists.ozlabs.org;\n dmarc=pass (p=none dis=none) header.from=linux.dev; dkim=pass (1024-bit key;\n unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256\n header.s=key1 header.b=eCIMj6Zf; dkim-atps=neutral;\n spf=pass (client-ip=91.218.175.181; helo=out-181.mta0.migadu.com;\n envelope-from=muchun.song@linux.dev;\n receiver=lists.ozlabs.org) smtp.mailfrom=linux.dev","Content-Type":"text/plain;\n\tcharset=us-ascii","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1;\n\tt=1776948488;\n\th=from:from:reply-to:subject:subject:date:date:message-id:message-id:\n\t to:to:cc:cc:mime-version:mime-version:content-type:content-type:\n\t content-transfer-encoding:content-transfer-encoding:\n\t in-reply-to:in-reply-to:references:references;\n\tbh=mzyqTkwD3Tq3eWJj43nY/4NCn6uElngPKF2N7BctSd4=;\n\tb=eCIMj6ZffdfaEQ/eCdUmx55xZEnSNjMOWnXKRPikt4j4906Q1SttxKiVjKU8rlNbvJpCby\n\terUQIBtSxfqPziAXNQuEfEecz4uegx50F+rqJgqHbsujB4xw/yqILQ/i2jg0Vq6Ad0Vpcj\n\tqd6Rxnai0Y+qvbwrtDxUe9CV+iyEcm4=","X-Mailing-List":"linuxppc-dev@lists.ozlabs.org","List-Id":"","List-Help":"","List-Owner":"","List-Post":"","List-Archive":",\n ","List-Subscribe":",\n ,\n ","List-Unsubscribe":"","Precedence":"list","Mime-Version":"1.0 (Mac OS X Mail 16.0 \\(3864.500.181\\))","Subject":"Re: [PATCH v5 v5 4/6] mm/sparse-vmemmap: Fix DAX vmemmap accounting\n with optimization","X-Report-Abuse":"Please report any abuse attempt to abuse@migadu.com and\n include these headers.","From":"Muchun Song ","In-Reply-To":"<20260423053237.a44b68034673bb35a1e042cd@linux-foundation.org>","Date":"Thu, 23 Apr 2026 20:43:02 +0800","Cc":"\"David Hildenbrand (Arm)\" ,\n Muchun Song ,\n Oscar Salvador ,\n Michael Ellerman ,\n Madhavan Srinivasan ,\n Lorenzo Stoakes ,\n \"Liam R . Howlett\" ,\n Vlastimil Babka ,\n Mike Rapoport ,\n Suren Baghdasaryan ,\n Michal Hocko ,\n Nicholas Piggin ,\n Christophe Leroy ,\n aneesh.kumar@linux.ibm.com,\n joao.m.martins@oracle.com,\n linux-mm@kvack.org,\n linuxppc-dev@lists.ozlabs.org,\n linux-kernel@vger.kernel.org","Content-Transfer-Encoding":"quoted-printable","Message-Id":"","References":"<20260423071911.1962859-1-songmuchun@bytedance.com>\n <20260423071911.1962859-5-songmuchun@bytedance.com>\n <1cbae635-a115-4270-bae2-64145d16f936@kernel.org>\n <1ADE7CE5-F02D-42B2-B7AC-FE0D6E86042D@linux.dev>\n <20260423053237.a44b68034673bb35a1e042cd@linux-foundation.org>","To":"Andrew Morton ","X-Migadu-Flow":"FLOW_OUT","X-Spam-Status":"No, score=-0.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID,\n\tDKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_LOW,SPF_HELO_PASS,SPF_PASS\n\tautolearn=disabled version=4.0.1 OzLabs 8","X-Spam-Checker-Version":"SpamAssassin 4.0.1 (2024-03-25) on lists.ozlabs.org"}},{"id":3681454,"web_url":"http://patchwork.ozlabs.org/comment/3681454/","msgid":"<20260423061402.71f0f37285e922f28853e5f8@linux-foundation.org>","date":"2026-04-23T13:14:02","subject":"Re: [PATCH v5 v5 4/6] mm/sparse-vmemmap: Fix DAX vmemmap accounting\n with optimization","submitter":{"id":107,"url":"http://patchwork.ozlabs.org/api/people/107/","name":"Andrew Morton","email":"akpm@linux-foundation.org"},"content":"On Thu, 23 Apr 2026 20:43:02 +0800 Muchun Song wrote:\n\n> > \n> > Ideally, split the series up into one series for 7.1-rcX+stable, another\n> > series for 7.2.rc1.\n> \n> Given that these issues have existed for a long time and the trigger\n> frequency is very low, I suggest we take a more conservative timing.\n> \n> We can prioritize getting the series into 7.2-rc1 first. Once they have\n> 'baked' in the mainline for a while without issues, we can then proceed\n> with the backport to -stable (7.1.x). This avoids rushing risky changes\n> into stable branches.\n\nGood plan. thanks.","headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linuxppc-dev@lists.ozlabs.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=linux-foundation.org header.i=@linux-foundation.org\n header.a=rsa-sha256 header.s=korg header.b=S03Ap+5t;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=lists.ozlabs.org\n (client-ip=112.213.38.117; helo=lists.ozlabs.org;\n envelope-from=linuxppc-dev+bounces-20014-incoming=patchwork.ozlabs.org@lists.ozlabs.org;\n receiver=patchwork.ozlabs.org)","lists.ozlabs.org;\n arc=none smtp.remote-ip=\"2600:3c0a:e001:78e:0:1991:8:25\"","lists.ozlabs.org;\n dmarc=none (p=none dis=none) header.from=linux-foundation.org","lists.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=linux-foundation.org header.i=@linux-foundation.org\n header.a=rsa-sha256 header.s=korg header.b=S03Ap+5t;\n\tdkim-atps=neutral","lists.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=linux-foundation.org\n (client-ip=2600:3c0a:e001:78e:0:1991:8:25; helo=sea.source.kernel.org;\n envelope-from=akpm@linux-foundation.org; receiver=lists.ozlabs.org)"],"Received":["from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117])\n\t(using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)\n\t key-exchange x25519 server-signature ECDSA (secp384r1 raw public key)\n server-digest SHA384)\n\t(No client certificate requested)\n\tby legolas.ozlabs.org (Postfix) with ESMTPS id 4g1c4W1sb9z1y2d\n\tfor ; Thu, 23 Apr 2026 23:14:17 +1000 (AEST)","from boromir.ozlabs.org (localhost [127.0.0.1])\n\tby lists.ozlabs.org (Postfix) with ESMTP id 4g1c4S5xgsz2yGf;\n\tThu, 23 Apr 2026 23:14:16 +1000 (AEST)","from sea.source.kernel.org (sea.source.kernel.org\n [IPv6:2600:3c0a:e001:78e:0:1991:8:25])\n\t(using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)\n\t key-exchange x25519 server-signature RSA-PSS (2048 bits) server-digest\n SHA256)\n\t(No client certificate requested)\n\tby lists.ozlabs.org (Postfix) with ESMTPS id 4g1c4M3h84z2yFQ\n\tfor ; Thu, 23 Apr 2026 23:14:10 +1000 (AEST)","from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58])\n\tby sea.source.kernel.org (Postfix) with ESMTP id 6E4EB40395;\n\tThu, 23 Apr 2026 13:14:03 +0000 (UTC)","by smtp.kernel.org (Postfix) with ESMTPSA id B3830C2BCAF;\n\tThu, 23 Apr 2026 13:14:02 +0000 (UTC)"],"ARC-Seal":"i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1776950056;\n\tcv=none;\n b=EQeqFm5ivULUlAIA0fEWdoSooaUIKeITci1JKjo7NKebpLJO2B47xS84jHM9Yb8QFZkvPs/JIseA73gS5S4mya+kZ/uoDRKv7s8Mm3xLlBsXMCNlPmtjNmNCk8GGxuAJGjedMCT7mK6Yd0h9JOtrawVbjb/KbR5eg/dyS1NXbC1X+nZUZ61Wc8gWitYhEb/XfyYLsvmMWayqlrzEYqDyncfMEMctZr0c55z1TGHS0SQ6Zkc36XUznJ57+zM2uezDO27QugCqaCGsYVE9himwRlPtrOgSmdy+YaVucKQO+nK/2sBEb7U4PEPTnSEyaqOIgG8RivL/rlghLHds0vr+Aw==","ARC-Message-Signature":"i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707;\n\tt=1776950056; c=relaxed/relaxed;\n\tbh=E5zu17eWGJx0ZbQT3/4IhKgc7X0rd78xRrUuhl9JKjo=;\n\th=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References:\n\t Mime-Version:Content-Type;\n b=gbZZB47SDFICp+oTY/rM3xOb3xES5DZy9ALS/b1RvbLYSN7KW+nw/AW6l3wRC7tcr6rXt/iqQt6SylHXOLqV64i0oo0GRG0ZuGNhcLuXjZIQsvtGkjIekyoH60d7VicPtyJF+fAN37H6si4Qy6E8h66bQTYcGJVY5zAomlzJjzo0q03T1PTwq5mIiTPO38Lrdw1DPeSI6IaP8QilLC63OBJJEnGap3MKHOorS6uV7AnjCUGbmKGTV2TR9UoYfJmAeI4DVLD+L5CbDJEpiQczrUPnbZByogrgUKRygM9fcW6goDbE5y3RYkWyBuv2K93EbQjtmgSosYBQy02W3/wHDw==","ARC-Authentication-Results":"i=1; lists.ozlabs.org;\n dmarc=none (p=none dis=none) header.from=linux-foundation.org;\n dkim=pass (1024-bit key;\n unprotected) header.d=linux-foundation.org header.i=@linux-foundation.org\n header.a=rsa-sha256 header.s=korg header.b=S03Ap+5t; dkim-atps=neutral;\n spf=pass (client-ip=2600:3c0a:e001:78e:0:1991:8:25;\n helo=sea.source.kernel.org; envelope-from=akpm@linux-foundation.org;\n receiver=lists.ozlabs.org) smtp.mailfrom=linux-foundation.org","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org;\n\ts=korg; t=1776950043;\n\tbh=vnWoAcvGkh3LMITKH32uZE+wtK1wshJpIlS68Lsz+nA=;\n\th=Date:From:To:Cc:Subject:In-Reply-To:References:From;\n\tb=S03Ap+5tRCZsFG/zml8CtLTb9BLLVXvGEoZoAY1RDgMQdM7wvq1yuwkIVYkAy2l2r\n\t ZlbkQb1/rkCirun+/str7aimc8Ii31c13+V/2Wa9O/D1OMLHNQBv4iOL3M2YQKTfNG\n\t qLoS826+ne+kj4Lz5F+ChjQSVWBhYDlhrAyzBOJ8=","Date":"Thu, 23 Apr 2026 06:14:02 -0700","From":"Andrew Morton ","To":"Muchun Song ","Cc":"\"David Hildenbrand (Arm)\" , Muchun Song\n , Oscar Salvador , Michael\n Ellerman , Madhavan Srinivasan ,\n Lorenzo Stoakes , \"Liam R . Howlett\"\n , Vlastimil Babka , Mike\n Rapoport , Suren Baghdasaryan , Michal\n Hocko , Nicholas Piggin , Christophe\n Leroy , aneesh.kumar@linux.ibm.com,\n joao.m.martins@oracle.com, linux-mm@kvack.org,\n linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org","Subject":"Re: [PATCH v5 v5 4/6] mm/sparse-vmemmap: Fix DAX vmemmap accounting\n with optimization","Message-Id":"<20260423061402.71f0f37285e922f28853e5f8@linux-foundation.org>","In-Reply-To":"","References":"<20260423071911.1962859-1-songmuchun@bytedance.com>\n\t<20260423071911.1962859-5-songmuchun@bytedance.com>\n\t<1cbae635-a115-4270-bae2-64145d16f936@kernel.org>\n\t<1ADE7CE5-F02D-42B2-B7AC-FE0D6E86042D@linux.dev>\n\t<20260423053237.a44b68034673bb35a1e042cd@linux-foundation.org>\n\t","X-Mailer":"Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu)","X-Mailing-List":"linuxppc-dev@lists.ozlabs.org","List-Id":"","List-Help":"","List-Owner":"","List-Post":"","List-Archive":",\n ","List-Subscribe":",\n ,\n ","List-Unsubscribe":"","Precedence":"list","Mime-Version":"1.0","Content-Type":"text/plain; charset=US-ASCII","Content-Transfer-Encoding":"7bit","X-Spam-Status":"No, score=-0.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID,\n\tDKIM_VALID_AU,DKIM_VALID_EF,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS\n\tautolearn=disabled version=4.0.1 OzLabs 8","X-Spam-Checker-Version":"SpamAssassin 4.0.1 (2024-03-25) on lists.ozlabs.org"}}]