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GET /api/1.2/patches/2219926/?format=api
{ "id": 2219926, "url": "http://patchwork.ozlabs.org/api/1.2/patches/2219926/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20260405125240.2558577-2-songmuchun@bytedance.com/", "project": { "id": 2, "url": "http://patchwork.ozlabs.org/api/1.2/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/", "list_archive_url": "https://lore.kernel.org/linuxppc-dev/", "list_archive_url_format": "https://lore.kernel.org/linuxppc-dev/{}/", "commit_url_format": "https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/commit/?id={}" }, "msgid": "<20260405125240.2558577-2-songmuchun@bytedance.com>", "list_archive_url": "https://lore.kernel.org/linuxppc-dev/20260405125240.2558577-2-songmuchun@bytedance.com/", "date": "2026-04-05T12:51:52", "name": "[01/49] mm/sparse: fix vmemmap accounting imbalance on memory hotplug error", "commit_ref": null, "pull_url": null, "state": "new", "archived": false, "hash": "b51c5aa3a36b99a393f0ef261ff9f665bf571c4f", "submitter": { "id": 78930, "url": "http://patchwork.ozlabs.org/api/1.2/people/78930/?format=api", "name": "Muchun Song", "email": "songmuchun@bytedance.com" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20260405125240.2558577-2-songmuchun@bytedance.com/mbox/", "series": [ { "id": 498783, "url": "http://patchwork.ozlabs.org/api/1.2/series/498783/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=498783", "date": "2026-04-05T12:51:51", "name": "mm: Generalize vmemmap optimization for DAX and HugeTLB", "version": 1, "mbox": "http://patchwork.ozlabs.org/series/498783/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/2219926/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/2219926/checks/", "tags": {}, "related": [], "headers": { "Return-Path": "\n <linuxppc-dev+bounces-19331-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=eK+EuRsY;\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; 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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>", "Subject": "[PATCH 01/49] mm/sparse: fix vmemmap accounting imbalance on memory\n hotplug error", "Date": "Sun, 5 Apr 2026 20:51:52 +0800", "Message-Id": "<20260405125240.2558577-2-songmuchun@bytedance.com>", "X-Mailer": "git-send-email 2.20.1", "In-Reply-To": "<20260405125240.2558577-1-songmuchun@bytedance.com>", "References": "<20260405125240.2558577-1-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": "In section_activate(), if populate_section_memmap() fails, the error\nhandling path calls section_deactivate() to roll back the state. This\napproach introduces an accounting imbalance.\n\nSince the commit c3576889d87b (\"mm: fix accounting of memmap pages\"),\nmemmap pages are accounted for only after populate_section_memmap()\nsucceeds. However, section_deactivate() unconditionally decrements the\nvmemmap account. Consequently, a failure in populate_section_memmap()\nleads to a negative offset (underflow) in the system's vmemmap tracking.\n\nWe can fix this by ensuring that the vmemmap accounting is incremented\nimmediately before checking for the success of populate_section_memmap().\nIf populate_section_memmap() fails, the subsequent call to\nsection_deactivate() will decrement the accounting, perfectly offsetting\nthe increment and maintaining balance.\n\nFixes: c3576889d87b (\"mm: fix accounting of memmap pages\")\nSigned-off-by: Muchun Song <songmuchun@bytedance.com>\n---\n mm/sparse-vmemmap.c | 2 +-\n 1 file changed, 1 insertion(+), 1 deletion(-)", "diff": "diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c\nindex 6eadb9d116e4..ee27d0c0efe2 100644\n--- a/mm/sparse-vmemmap.c\n+++ b/mm/sparse-vmemmap.c\n@@ -822,11 +822,11 @@ static struct page * __meminit section_activate(int nid, unsigned long pfn,\n \t\treturn pfn_to_page(pfn);\n \n \tmemmap = populate_section_memmap(pfn, nr_pages, nid, altmap, pgmap);\n+\tmemmap_pages_add(DIV_ROUND_UP(nr_pages * sizeof(struct page), PAGE_SIZE));\n \tif (!memmap) {\n \t\tsection_deactivate(pfn, nr_pages, altmap);\n \t\treturn ERR_PTR(-ENOMEM);\n \t}\n-\tmemmap_pages_add(DIV_ROUND_UP(nr_pages * sizeof(struct page), PAGE_SIZE));\n \n \treturn memmap;\n }\n", "prefixes": [ "01/49" ] }