{"id":2227629,"url":"http://patchwork.ozlabs.org/api/patches/2227629/?format=json","web_url":"http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20260424025547.3806072-7-songmuchun@bytedance.com/","project":{"id":2,"url":"http://patchwork.ozlabs.org/api/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":"<20260424025547.3806072-7-songmuchun@bytedance.com>","list_archive_url":"https://lore.kernel.org/linuxppc-dev/20260424025547.3806072-7-songmuchun@bytedance.com/","date":"2026-04-24T02:55:46","name":"[v6,6/7] mm/mm_init: Fix uninitialized struct pages for ZONE_DEVICE","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"94b7e34f9eae36397189582ac79ee28c1f9746fa","submitter":{"id":78930,"url":"http://patchwork.ozlabs.org/api/people/78930/?format=json","name":"Muchun Song","email":"songmuchun@bytedance.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20260424025547.3806072-7-songmuchun@bytedance.com/mbox/","series":[{"id":501285,"url":"http://patchwork.ozlabs.org/api/series/501285/?format=json","web_url":"http://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=501285","date":"2026-04-24T02:55:40","name":"mm: fix vmemmap optimization accounting and initialization","version":6,"mbox":"http://patchwork.ozlabs.org/series/501285/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2227629/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2227629/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=PuBNGDMd;\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 ,\n\tstable@vger.kernel.org","Subject":"[PATCH v6 6/7] mm/mm_init: Fix uninitialized struct pages for\n ZONE_DEVICE","Date":"Fri, 24 Apr 2026 10:55:46 +0800","Message-Id":"<20260424025547.3806072-7-songmuchun@bytedance.com>","X-Mailer":"git-send-email 2.20.1","In-Reply-To":"<20260424025547.3806072-1-songmuchun@bytedance.com>","References":"<20260424025547.3806072-1-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":"If DAX memory is hotplugged into an unoccupied subsection of an early\nsection, section_activate() reuses the unoptimized boot memmap.\nHowever, compound_nr_pages() still assumes that vmemmap optimization is\nin effect and initializes only the reduced number of struct pages. As a\nresult, the remaining tail struct pages are left uninitialized, which\ncan later lead to unexpected behavior or crashes.\n\nFix this by treating early sections as unoptimized when calculating how\nmany struct pages to initialize.\n\nFixes: 6fd3620b3428 (\"mm/page_alloc: reuse tail struct pages for compound devmaps\")\nCc: stable@vger.kernel.org\nSigned-off-by: Muchun Song \nAcked-by: David Hildenbrand (Arm) \n---\n mm/mm_init.c | 13 ++++++++++---\n 1 file changed, 10 insertions(+), 3 deletions(-)","diff":"diff --git a/mm/mm_init.c b/mm/mm_init.c\nindex cfc76953e249..bd466a3c10c8 100644\n--- a/mm/mm_init.c\n+++ b/mm/mm_init.c\n@@ -1055,10 +1055,17 @@ static void __ref __init_zone_device_page(struct page *page, unsigned long pfn,\n * of how the sparse_vmemmap internals handle compound pages in the lack\n * of an altmap. See vmemmap_populate_compound_pages().\n */\n-static inline unsigned long compound_nr_pages(struct vmem_altmap *altmap,\n+static inline unsigned long compound_nr_pages(unsigned long pfn,\n+\t\t\t\t\t struct vmem_altmap *altmap,\n \t\t\t\t\t struct dev_pagemap *pgmap)\n {\n-\tif (!vmemmap_can_optimize(altmap, pgmap))\n+\t/*\n+\t * If DAX memory is hot-plugged into an unoccupied subsection\n+\t * of an early section, the unoptimized boot memmap is reused.\n+\t * See section_activate().\n+\t */\n+\tif (early_section(__pfn_to_section(pfn)) ||\n+\t !vmemmap_can_optimize(altmap, pgmap))\n \t\treturn pgmap_vmemmap_nr(pgmap);\n \n \treturn VMEMMAP_RESERVE_NR * (PAGE_SIZE / sizeof(struct page));\n@@ -1128,7 +1135,7 @@ void __ref memmap_init_zone_device(struct zone *zone,\n \t\t\tcontinue;\n \n \t\tmemmap_init_compound(page, pfn, zone_idx, nid, pgmap,\n-\t\t\t\t compound_nr_pages(altmap, pgmap));\n+\t\t\t\t compound_nr_pages(pfn, altmap, pgmap));\n \t}\n \n \tpageblock_migratetype_init_range(start_pfn, nr_pages, MIGRATE_MOVABLE);\n","prefixes":["v6","6/7"]}