{"id":2219926,"url":"http://patchwork.ozlabs.org/api/1.2/patches/2219926/?format=json","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=json","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=json","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=json","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 ","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\" ,\n\tVlastimil Babka ,\n\tMike Rapoport ,\n\tSuren Baghdasaryan ,\n\tMichal Hocko ,\n\tNicholas Piggin ,\n\tChristophe Leroy ,\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 ","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":"","List-Help":"","List-Owner":"","List-Post":"","List-Archive":",\n ","List-Subscribe":",\n ,\n ","List-Unsubscribe":"","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 \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"]}