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GET /api/1.2/patches/2219957/?format=api
{ "id": 2219957, "url": "http://patchwork.ozlabs.org/api/1.2/patches/2219957/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20260405125240.2558577-33-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": "<20260405125240.2558577-33-songmuchun@bytedance.com>", "list_archive_url": "https://lore.kernel.org/linuxppc-dev/20260405125240.2558577-33-songmuchun@bytedance.com/", "date": "2026-04-05T12:52:23", "name": "[32/49] mm/sparse-vmemmap: consolidate shared tail page allocation", "commit_ref": null, "pull_url": null, "state": "new", "archived": false, "hash": "9516093a650bb3614af47b9be52762356e526d1c", "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/20260405125240.2558577-33-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/2219957/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/2219957/checks/", "tags": {}, "related": [], "headers": { "Return-Path": "\n <linuxppc-dev+bounces-19362-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=ca6xQcsy;\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 32/49] mm/sparse-vmemmap: consolidate shared tail page\n allocation", "Date": "Sun, 5 Apr 2026 20:52:23 +0800", "Message-Id": "<20260405125240.2558577-33-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": "Currently, both HugeTLB and sparse-vmemmap have their own logic to get\nor allocate the shared tail page for vmemmap optimization. The HugeTLB\nversion handles runtime concurrency using cmpxchg, while the\nsparse-vmemmap version (used only at boot time) was simpler.\n\nThis patch unifies them into a single function in mm/sparse-vmemmap.c.\n\nThe new function of vmemmap_shared_tail_page() is introduced: it returns\nthe shared page frame used to map the tail vmemmap pages of a compound\npage.\n\nFurthermore, vmemmap_alloc_block_zero() is used as a safe allocation\nmethod for both situations:\n\n1. It calls alloc_pages_node() (via vmemmap_alloc_block()) when slab is\n available.\n\n2. It falls back to bootmem allocation during early boot, making the function\n suitable for use in both early boot (sparse-vmemmap init) and runtime\n (HugeTLB HVO) contexts.\n\nThis reduces code duplication and ensures consistent behavior.\n\nSigned-off-by: Muchun Song <songmuchun@bytedance.com>\n---\n include/linux/mm.h | 1 +\n mm/hugetlb_vmemmap.c | 28 +---------------------------\n mm/sparse-vmemmap.c | 42 +++++++++++++++++++++---------------------\n 3 files changed, 23 insertions(+), 48 deletions(-)", "diff": "diff --git a/include/linux/mm.h b/include/linux/mm.h\nindex 93e447468131..15841829b7eb 100644\n--- a/include/linux/mm.h\n+++ b/include/linux/mm.h\n@@ -4880,6 +4880,7 @@ int vmemmap_populate(unsigned long start, unsigned long end, int node,\n void vmemmap_wrprotect_hvo(unsigned long start, unsigned long end, int node,\n \t\t\t unsigned long headsize);\n void vmemmap_populate_print_last(void);\n+struct page *vmemmap_shared_tail_page(unsigned int order, struct zone *zone);\n #ifdef CONFIG_MEMORY_HOTPLUG\n void vmemmap_free(unsigned long start, unsigned long end,\n \t\tstruct vmem_altmap *altmap);\ndiff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c\nindex a190b9b94346..a7ea98fcc18e 100644\n--- a/mm/hugetlb_vmemmap.c\n+++ b/mm/hugetlb_vmemmap.c\n@@ -493,32 +493,6 @@ static bool vmemmap_should_optimize_folio(const struct hstate *h, struct folio *\n \treturn true;\n }\n \n-static struct page *vmemmap_get_tail(unsigned int order, struct zone *zone)\n-{\n-\tconst unsigned int idx = order - OPTIMIZABLE_FOLIO_MIN_ORDER;\n-\tstruct page *tail, *p;\n-\tint node = zone_to_nid(zone);\n-\n-\ttail = READ_ONCE(zone->vmemmap_tails[idx]);\n-\tif (likely(tail))\n-\t\treturn tail;\n-\n-\ttail = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);\n-\tif (!tail)\n-\t\treturn NULL;\n-\n-\tp = page_to_virt(tail);\n-\tfor (int i = 0; i < PAGE_SIZE / sizeof(struct page); i++)\n-\t\tinit_compound_tail(p + i, NULL, order, zone);\n-\n-\tif (cmpxchg(&zone->vmemmap_tails[idx], NULL, tail)) {\n-\t\t__free_page(tail);\n-\t\ttail = READ_ONCE(zone->vmemmap_tails[idx]);\n-\t}\n-\n-\treturn tail;\n-}\n-\n static int __hugetlb_vmemmap_optimize_folio(const struct hstate *h,\n \t\t\t\t\t struct folio *folio,\n \t\t\t\t\t struct list_head *vmemmap_pages,\n@@ -535,7 +509,7 @@ static int __hugetlb_vmemmap_optimize_folio(const struct hstate *h,\n \t\treturn ret;\n \n \tnid = folio_nid(folio);\n-\tvmemmap_tail = vmemmap_get_tail(h->order, folio_zone(folio));\n+\tvmemmap_tail = vmemmap_shared_tail_page(h->order, folio_zone(folio));\n \tif (!vmemmap_tail)\n \t\treturn -ENOMEM;\n \ndiff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c\nindex c35d912a1fef..309d935fb05e 100644\n--- a/mm/sparse-vmemmap.c\n+++ b/mm/sparse-vmemmap.c\n@@ -143,8 +143,6 @@ void __meminit vmemmap_verify(pte_t *pte, int node,\n \t\t\tstart, end - 1);\n }\n \n-static __meminit struct page *vmemmap_get_tail(unsigned int order, struct zone *zone);\n-\n static pte_t * __meminit vmemmap_pte_populate(pmd_t *pmd, unsigned long addr, int node,\n \t\t\t\t\t struct vmem_altmap *altmap,\n \t\t\t\t\t unsigned long ptpfn)\n@@ -160,8 +158,8 @@ static pte_t * __meminit vmemmap_pte_populate(pmd_t *pmd, unsigned long addr, in\n \t\t\tunsigned long pfn = page_to_pfn((struct page *)addr);\n \t\t\tconst struct mem_section *ms = __pfn_to_section(pfn);\n \n-\t\t\tpage = vmemmap_get_tail(section_order(ms),\n-\t\t\t\t\t\tpfn_to_zone(pfn, node));\n+\t\t\tpage = vmemmap_shared_tail_page(section_order(ms),\n+\t\t\t\t\t\t\tpfn_to_zone(pfn, node));\n \t\t\tif (!page)\n \t\t\t\treturn NULL;\n \t\t\tptpfn = page_to_pfn(page);\n@@ -338,32 +336,34 @@ void vmemmap_wrprotect_hvo(unsigned long addr, unsigned long end,\n \t}\n }\n \n-static __meminit struct page *vmemmap_get_tail(unsigned int order, struct zone *zone)\n+struct page *vmemmap_shared_tail_page(unsigned int order, struct zone *zone)\n {\n-\tstruct page *p, *tail;\n-\tunsigned int idx;\n-\tint node = zone_to_nid(zone);\n+\tvoid *addr;\n+\tstruct page *page;\n+\tunsigned int idx = order - OPTIMIZABLE_FOLIO_MIN_ORDER;\n \n-\tif (WARN_ON_ONCE(order < OPTIMIZABLE_FOLIO_MIN_ORDER))\n-\t\treturn NULL;\n-\tif (WARN_ON_ONCE(order > MAX_FOLIO_ORDER))\n+\tif (WARN_ON_ONCE(idx >= ARRAY_SIZE(zone->vmemmap_tails)))\n \t\treturn NULL;\n \n-\tidx = order - OPTIMIZABLE_FOLIO_MIN_ORDER;\n-\ttail = zone->vmemmap_tails[idx];\n-\tif (tail)\n-\t\treturn tail;\n+\tpage = READ_ONCE(zone->vmemmap_tails[idx]);\n+\tif (likely(page))\n+\t\treturn page;\n \n-\tp = vmemmap_alloc_block_zero(PAGE_SIZE, node);\n-\tif (!p)\n+\taddr = vmemmap_alloc_block_zero(PAGE_SIZE, zone_to_nid(zone));\n+\tif (!addr)\n \t\treturn NULL;\n+\n \tfor (int i = 0; i < PAGE_SIZE / sizeof(struct page); i++)\n-\t\tinit_compound_tail(p + i, NULL, order, zone);\n+\t\tinit_compound_tail((struct page *)addr + i, NULL, order, zone);\n \n-\ttail = virt_to_page(p);\n-\tzone->vmemmap_tails[idx] = tail;\n+\tpage = virt_to_page(addr);\n+\tif (cmpxchg(&zone->vmemmap_tails[idx], NULL, page) != NULL) {\n+\t\tVM_BUG_ON(!slab_is_available());\n+\t\t__free_page(page);\n+\t\tpage = READ_ONCE(zone->vmemmap_tails[idx]);\n+\t}\n \n-\treturn tail;\n+\treturn page;\n }\n \n void __weak __meminit vmemmap_set_pmd(pmd_t *pmd, void *p, int node,\n", "prefixes": [ "32/49" ] }