Patch Detail
get:
Show a patch.
patch:
Update a patch.
put:
Update a patch.
GET /api/1.1/patches/2229396/?format=api
{ "id": 2229396, "url": "http://patchwork.ozlabs.org/api/1.1/patches/2229396/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20260428081855.1249045-5-songmuchun@bytedance.com/", "project": { "id": 2, "url": "http://patchwork.ozlabs.org/api/1.1/projects/2/?format=api", "name": "Linux PPC development", "link_name": "linuxppc-dev", "list_id": "linuxppc-dev.lists.ozlabs.org", "list_email": "linuxppc-dev@lists.ozlabs.org", "web_url": "https://github.com/linuxppc/wiki/wiki", "scm_url": "https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git", "webscm_url": "https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/" }, "msgid": "<20260428081855.1249045-5-songmuchun@bytedance.com>", "date": "2026-04-28T08:18:53", "name": "[v8,4/6] mm/sparse-vmemmap: Fix DAX vmemmap accounting with optimization", "commit_ref": null, "pull_url": null, "state": "new", "archived": false, "hash": "87369a09430a64bd5dd87674bd8bb90c6e338d50", "submitter": { "id": 78930, "url": "http://patchwork.ozlabs.org/api/1.1/people/78930/?format=api", "name": "Muchun Song", "email": "songmuchun@bytedance.com" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20260428081855.1249045-5-songmuchun@bytedance.com/mbox/", "series": [ { "id": 501789, "url": "http://patchwork.ozlabs.org/api/1.1/series/501789/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=501789", "date": "2026-04-28T08:18:50", "name": "[v8,1/6] mm/sparse-vmemmap: Fix vmemmap accounting underflow", "version": 8, "mbox": "http://patchwork.ozlabs.org/series/501789/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/2229396/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/2229396/checks/", "tags": {}, "headers": { "Return-Path": "\n <linuxppc-dev+bounces-20225-incoming=patchwork.ozlabs.org@lists.ozlabs.org>", "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=bytedance.com header.i=@bytedance.com\n header.a=rsa-sha256 header.s=google header.b=kbarLWTO;\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-20225-incoming=patchwork.ozlabs.org@lists.ozlabs.org;\n receiver=patchwork.ozlabs.org)", "lists.ozlabs.org;\n arc=none smtp.remote-ip=\"2607:f8b0:4864:20::102f\"", "lists.ozlabs.org;\n dmarc=pass (p=quarantine dis=none) header.from=bytedance.com", "lists.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=bytedance.com header.i=@bytedance.com\n header.a=rsa-sha256 header.s=google header.b=kbarLWTO;\n\tdkim-atps=neutral", "lists.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=bytedance.com\n (client-ip=2607:f8b0:4864:20::102f; helo=mail-pj1-x102f.google.com;\n envelope-from=songmuchun@bytedance.com; 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)\n\t(No client certificate requested)\n\tby legolas.ozlabs.org (Postfix) with ESMTPS id 4g4YJF314xz1yHX\n\tfor <incoming@patchwork.ozlabs.org>; Tue, 28 Apr 2026 18:19:41 +1000 (AEST)", "from boromir.ozlabs.org (localhost [127.0.0.1])\n\tby lists.ozlabs.org (Postfix) with ESMTP id 4g4YHz4t0Zz2ynv;\n\tTue, 28 Apr 2026 18:19:27 +1000 (AEST)", "from mail-pj1-x102f.google.com (mail-pj1-x102f.google.com\n [IPv6:2607:f8b0:4864:20::102f])\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 4g4YHy5yLLz2yr4\n\tfor <linuxppc-dev@lists.ozlabs.org>; Tue, 28 Apr 2026 18:19:26 +1000 (AEST)", "by mail-pj1-x102f.google.com with SMTP id\n 98e67ed59e1d1-35fb7c1a455so4112469a91.3\n for <linuxppc-dev@lists.ozlabs.org>;\n Tue, 28 Apr 2026 01:19:26 -0700 (PDT)", "from n232-176-004.byted.org ([36.110.163.101])\n by smtp.gmail.com with ESMTPSA id\n 98e67ed59e1d1-3649003650esm2181356a91.8.2026.04.28.01.19.19\n (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256);\n Tue, 28 Apr 2026 01:19:24 -0700 (PDT)" ], "ARC-Seal": "i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1777364367;\n\tcv=none;\n b=WIgVZlT7u84D/a3329n/9dpkM8VxpRvwtONpDnzCH5oV23xMvZTvPLQw69iBbz17MBGYSOWc3CdFEVnS5gfTCefNjinvK23aTVcmchaqyxLP9She3iE4xfKzy313Zqn6cJOH0WfNepuhuP9WTEL2o2F+A74WgmhiMCPbrkX2gPl+WOLS6WlPSYXnzAyPDjEsagmC5p6VkHDntmHfBLDqnjdHKuAyB24kbWR9dYto53+s58F5rN3cRd3jpEnfJ0N1cX/Oy/4fG+wtV6g98wRvZG361T8bLwBgxmaEs0NUxsMkkweIZmrP7VRsdQDEHYhusxKOnDF8HT3joOzl5wAYXw==", "ARC-Message-Signature": "i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707;\n\tt=1777364367; c=relaxed/relaxed;\n\tbh=rL183+C/B0Npg+SiHlF1+/ufB8oZmfwNupE6AmX40Ic=;\n\th=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References:\n\t MIME-Version;\n b=ht/ZuFkxsuKn0koWz3cz+flOFseGvvfj+pHfKuwqP/xgax8J5HegdFy5C06YlXPmIPWGOyvzwd6FJbcycYQK0Rx4s1JFfjOo8qiT4PNR86yzKE0yEdoha5HrvIOPr8KjwOFcaGuIqat8rNY5WqnfLDAqOcpHOhZFTQhOOfEHvaTIX3N3VrcNbHVCWU9LpDkDvFRNAuJTOkDq16ACmweJI3twiTYtspgY/2gEe6hUwWsGGcWzLp1BEYyDaMwL73GDUmjXssYCDqU+xhRDetXWYzYy/p+06Hic52sLi2mGpdETRYbyjyF5lrTf82YqK8688H9kINA6sfFgzgOCbco2Pw==", "ARC-Authentication-Results": "i=1; lists.ozlabs.org;\n dmarc=pass (p=quarantine dis=none) header.from=bytedance.com;\n dkim=pass (2048-bit key;\n unprotected) header.d=bytedance.com header.i=@bytedance.com\n header.a=rsa-sha256 header.s=google header.b=kbarLWTO; dkim-atps=neutral;\n spf=pass (client-ip=2607:f8b0:4864:20::102f; helo=mail-pj1-x102f.google.com;\n envelope-from=songmuchun@bytedance.com;\n receiver=lists.ozlabs.org) smtp.mailfrom=bytedance.com", "DKIM-Signature": "v=1; a=rsa-sha256; c=relaxed/relaxed;\n d=bytedance.com; s=google; t=1777364365; x=1777969165;\n darn=lists.ozlabs.org;\n h=content-transfer-encoding:mime-version:references:in-reply-to\n :message-id:date:subject:cc:to:from:from:to:cc:subject:date\n :message-id:reply-to;\n bh=rL183+C/B0Npg+SiHlF1+/ufB8oZmfwNupE6AmX40Ic=;\n b=kbarLWTOjs54Fuaop4Y7A/QTI3FWw+4UkNEi1QojID4PymS2Sir9KZkzY6JejIvvIn\n QaUt94tCxATiPy1WuV8Ic4I/d6vvE4rWhtdfEhdN1oVJk43fDlI+62LU8YSCZO12iWqH\n CQKQyXVVw+iaG8ZK6He8fvRmFLkKO/WEu1ZYGIMN+vKskduM/At3hp6G1WOQG1c4xRxc\n oz0ZzP7/oaTx/WRiq8VRYx1cOP77jC7kmWkDl6GQXPKdv9Nb7Ne5A/5uR6YKQ9O2OC/L\n iYNd77QCEzIaFbZFYBFCf9t/zpIvR7N7ekbUiVdFxRieN3xi5FD33b5+VJcYzTCRhaRx\n kl4A==", "X-Google-DKIM-Signature": "v=1; a=rsa-sha256; c=relaxed/relaxed;\n d=1e100.net; s=20251104; t=1777364365; x=1777969165;\n h=content-transfer-encoding:mime-version:references:in-reply-to\n :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from\n :to:cc:subject:date:message-id:reply-to;\n bh=rL183+C/B0Npg+SiHlF1+/ufB8oZmfwNupE6AmX40Ic=;\n b=dA1SV3tXHavFJAvKyCSIigUHxzmaAhglOgx3KCyJUCUggtxTcMSM5XWmmh60FlfLgt\n UERn7yByK//oJmUd5qNDGYm85RTOjT2QyNDty7XMz/WyQukKHO7IKFhdlcP+hSDvZ3Sv\n 5vzvseJHdOsNNz5nQZcuQgVvg2yKaWn0s5aN78DZfdlpDuia0u8VCjXDVdwF9jp8o7dU\n 0I65G+TCJR/m5cKD4/sn5IIwSSfcSnelziIMiazHoVB/puxIvUMCYz3NdpJe1anCudKd\n +rlhUmnaVyeZRtM/STjFUk3vM3D3gDX4W6Nnxt8V7dHpKEkn5rldsjyCZKlFYi8oNqxp\n z+MA==", "X-Forwarded-Encrypted": "i=1;\n AFNElJ8i1O8I+lJFCPbn+6VkD6Hg+EJD9DHM08ehfhQ0XPyM6avhX9jA7UJWkaC1eEVcHFP5AAitjocDD8/Ak8E=@lists.ozlabs.org", "X-Gm-Message-State": "AOJu0YwOgPUfhQi0HBAgTKBNTlOD8LnyvERp8cuu9PUL859o2gPcVgv6\n\tRcNQ9fzacVMXZaiqPPdUSH2LovAeou8b0+TX3KJdEQaraP6r3//2L+MgjZ1qjh+1rNc=", "X-Gm-Gg": "AeBDievpXtuanvbrPO7PCbpsVfi4WSGJJ1Sv4wlhAwyRm9emclT+SqDur+iHK/z79lj\n\t8GXbbFRHDaC0/IPJYQySdJE4KV6wySk7tgH1V5izOh8mfhLrvVXw/tueCFRbzWFQ2qOp68iRT1I\n\tGvkPX0tHIyQh2np6qDmKK06etQHryBk/UPm1NNEpfEtfHBMyXq5OQMtVMRjJ7WbdFN27K+i1tLo\n\ty+4kqEgC5Na8ogagEaowG4hOcrlqERQKrkUBzQMhQDOniPWMHVnZrSeI9WN8CLlaRPMj5Co7/ap\n\tH+md+ir+kFBuDU3LIImoJqOxc4dae50aUSlytse4dPa16pw1zuk63vpElmGozMMfGMKBzxVvO3R\n\tS3+Wt0o7j3NQvgGy040Bz9uCjaTKNgg1okXZ6+seSKSdPbTrs2mQ4eNgvbTxORormtq/Xp/cVk+\n\t0X5TyoQUQIMHP3KMXuI2wclKjPqG4ogmVasblqv0qocFYvMbvuLMse7Gfwkrnbs+HULA==", "X-Received": "by 2002:a17:90b:56cf:b0:35b:96bb:47ba with SMTP id\n 98e67ed59e1d1-364921a915dmr2295268a91.26.1777364364837;\n Tue, 28 Apr 2026 01:19:24 -0700 (PDT)", "From": "Muchun Song <songmuchun@bytedance.com>", "To": "Andrew Morton <akpm@linux-foundation.org>,\n\tDavid Hildenbrand <david@kernel.org>,\n\tMuchun Song <muchun.song@linux.dev>,\n\tOscar Salvador <osalvador@suse.de>,\n\tMichael Ellerman <mpe@ellerman.id.au>,\n\tMadhavan Srinivasan <maddy@linux.ibm.com>", "Cc": "Lorenzo Stoakes <ljs@kernel.org>,\n\t\"Liam R . Howlett\" <Liam.Howlett@oracle.com>,\n\tVlastimil Babka <vbabka@kernel.org>,\n\tMike Rapoport <rppt@kernel.org>,\n\tSuren Baghdasaryan <surenb@google.com>,\n\tMichal Hocko <mhocko@suse.com>,\n\tNicholas Piggin <npiggin@gmail.com>,\n\tChristophe Leroy <chleroy@kernel.org>,\n\taneesh.kumar@linux.ibm.com,\n\tjoao.m.martins@oracle.com,\n\tlinux-mm@kvack.org,\n\tlinuxppc-dev@lists.ozlabs.org,\n\tlinux-kernel@vger.kernel.org,\n\tMuchun Song <songmuchun@bytedance.com>,\n\tstable@vger.kernel.org", "Subject": "[PATCH v8 4/6] mm/sparse-vmemmap: Fix DAX vmemmap accounting with\n optimization", "Date": "Tue, 28 Apr 2026 16:18:53 +0800", "Message-Id": "<20260428081855.1249045-5-songmuchun@bytedance.com>", "X-Mailer": "git-send-email 2.20.1", "In-Reply-To": "<20260428081855.1249045-1-songmuchun@bytedance.com>", "References": "<20260428081855.1249045-1-songmuchun@bytedance.com>", "X-Mailing-List": "linuxppc-dev@lists.ozlabs.org", "List-Id": "<linuxppc-dev.lists.ozlabs.org>", "List-Help": "<mailto:linuxppc-dev+help@lists.ozlabs.org>", "List-Owner": "<mailto:linuxppc-dev+owner@lists.ozlabs.org>", "List-Post": "<mailto:linuxppc-dev@lists.ozlabs.org>", "List-Archive": "<https://lore.kernel.org/linuxppc-dev/>,\n <https://lists.ozlabs.org/pipermail/linuxppc-dev/>", "List-Subscribe": "<mailto:linuxppc-dev+subscribe@lists.ozlabs.org>,\n <mailto:linuxppc-dev+subscribe-digest@lists.ozlabs.org>,\n <mailto:linuxppc-dev+subscribe-nomail@lists.ozlabs.org>", "List-Unsubscribe": "<mailto:linuxppc-dev+unsubscribe@lists.ozlabs.org>", "Precedence": "list", "MIME-Version": "1.0", "Content-Transfer-Encoding": "8bit", "X-Spam-Status": "No, score=-0.2 required=3.0 tests=DKIM_SIGNED,DKIM_VALID,\n\tDKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE,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" }, "content": "When vmemmap optimization is enabled for DAX, the nr_memmap_pages\ncounter in /proc/vmstat is incorrect. The current code always accounts\nfor the full, non-optimized vmemmap size, but vmemmap optimization\nreduces the actual number of vmemmap pages by reusing tail pages. This\ncauses the system to overcount vmemmap usage, leading to inaccurate\npage statistics in /proc/vmstat.\n\nFix this by introducing section_nr_vmemmap_pages(), which returns the exact\nvmemmap page count for a given pfn range based on whether optimization\nis in effect.\n\nFixes: 15995a352474 (\"mm: report per-page metadata information\")\nCc: stable@vger.kernel.org\nSigned-off-by: Muchun Song <songmuchun@bytedance.com>\nAcked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>\nAcked-by: Oscar Salvador <osalvador@suse.de>\nAcked-by: David Hildenbrand (Arm) <david@kernel.org>\n---\nv7-v8:\n- Move VM_WARN_ON_ONCE(nr_pages > PAGES_PER_SECTION); to the top of\n section_nr_vmemmap_pages().\n- Add Acked-by from David.\n---\n mm/sparse-vmemmap.c | 34 ++++++++++++++++++++++++++++++----\n 1 file changed, 30 insertions(+), 4 deletions(-)", "diff": "diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c\nindex 3340f6d30b01..932082296e8d 100644\n--- a/mm/sparse-vmemmap.c\n+++ b/mm/sparse-vmemmap.c\n@@ -652,6 +652,31 @@ 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_SUBSECTION));\n+\tVM_WARN_ON_ONCE(nr_pages > PAGES_PER_SECTION);\n+\n+\tif (!vmemmap_can_optimize(altmap, pgmap))\n+\t\treturn DIV_ROUND_UP(nr_pages * sizeof(struct page), PAGE_SIZE);\n+\n+\tif (order < PFN_SECTION_SHIFT) {\n+\t\tVM_WARN_ON_ONCE(!IS_ALIGNED(pfn | nr_pages, pages_per_compound));\n+\t\treturn VMEMMAP_RESERVE_NR * nr_pages / pages_per_compound;\n+\t}\n+\n+\tVM_WARN_ON_ONCE(!IS_ALIGNED(pfn | nr_pages, PAGES_PER_SECTION));\n+\n+\tif (IS_ALIGNED(pfn, pages_per_compound))\n+\t\treturn VMEMMAP_RESERVE_NR;\n+\n+\treturn 0;\n+}\n+\n static struct page * __meminit populate_section_memmap(unsigned long pfn,\n \t\tunsigned long nr_pages, int nid, struct vmem_altmap *altmap,\n \t\tstruct dev_pagemap *pgmap)\n@@ -659,7 +684,7 @@ static struct page * __meminit populate_section_memmap(unsigned long pfn,\n \tstruct page *page = __populate_section_memmap(pfn, nr_pages, nid, altmap,\n \t\t\t\t\t\t pgmap);\n \n-\tmemmap_pages_add(DIV_ROUND_UP(nr_pages * sizeof(struct page), PAGE_SIZE));\n+\tmemmap_pages_add(section_nr_vmemmap_pages(pfn, nr_pages, altmap, pgmap));\n \n \treturn page;\n }\n@@ -670,7 +695,7 @@ static void depopulate_section_memmap(unsigned long pfn, unsigned long nr_pages,\n \tunsigned long start = (unsigned long) pfn_to_page(pfn);\n \tunsigned long end = start + nr_pages * sizeof(struct page);\n \n-\tmemmap_pages_add(-1L * (DIV_ROUND_UP(nr_pages * sizeof(struct page), PAGE_SIZE)));\n+\tmemmap_pages_add(-section_nr_vmemmap_pages(pfn, nr_pages, altmap, pgmap));\n \tvmemmap_free(start, end, altmap);\n }\n \n@@ -678,9 +703,10 @@ static void free_map_bootmem(struct page *memmap)\n {\n \tunsigned long start = (unsigned long)memmap;\n \tunsigned long end = (unsigned long)(memmap + PAGES_PER_SECTION);\n+\tunsigned long pfn = page_to_pfn(memmap);\n \n-\tmemmap_boot_pages_add(-1L * (DIV_ROUND_UP(PAGES_PER_SECTION * sizeof(struct page),\n-\t\t\t\t\t\t PAGE_SIZE)));\n+\tmemmap_boot_pages_add(-section_nr_vmemmap_pages(pfn, PAGES_PER_SECTION,\n+\t\t\t\t\t\t\tNULL, NULL));\n \tvmemmap_free(start, end, NULL);\n }\n \n", "prefixes": [ "v8", "4/6" ] }