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GET /api/1.2/patches/2219949/?format=api
{ "id": 2219949, "url": "http://patchwork.ozlabs.org/api/1.2/patches/2219949/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20260405125240.2558577-25-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": "<20260405125240.2558577-25-songmuchun@bytedance.com>", "list_archive_url": "https://lore.kernel.org/linuxppc-dev/20260405125240.2558577-25-songmuchun@bytedance.com/", "date": "2026-04-05T12:52:15", "name": "[24/49] mm/sparse-vmemmap: initialize shared tail vmemmap page upon allocation", "commit_ref": null, "pull_url": null, "state": "new", "archived": false, "hash": "ed58ab4d3c19ef30c0f377900387d5a20efd5e5c", "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/20260405125240.2558577-25-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/2219949/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/2219949/checks/", "tags": {}, "related": [], "headers": { "Return-Path": "\n <linuxppc-dev+bounces-19354-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=Bai+42H6;\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 24/49] mm/sparse-vmemmap: initialize shared tail vmemmap page\n upon allocation", "Date": "Sun, 5 Apr 2026 20:52:15 +0800", "Message-Id": "<20260405125240.2558577-25-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": "Previously, the shared vmemmap tail page allocated in vmemmap_get_tail()\nwas intentionally left uninitialized. This was because the subsequent\nmemmap_init_range() would unconditionally overwrite any initialization done\nhere, forcing subsystems (like HugeTLB) to compensate and perform the\ninitialization later in their own specific routines (e.g., hugetlb_vmemmap_init()).\n\nThanks to the previous patch, memmap_init_range() is now aware of the\nsection's compound page order and safely skips the redundant initialization\nfor these optimizable compound vmemmap pages.\n\nBecause the overwrite issue is resolved, we can now fully initialize the\nshared tail pages (via init_compound_tail()) immediately upon allocation\nin vmemmap_get_tail(). This simplifies the initialization flow and removes\nthe need to defer this work to specific subsystems.\n\nNote that the initialization logic in hugetlb_vmemmap_init() is not removed\nyet. It will be completely removed once HugeTLB switches to the new memory\nsection compound page order mechanism.\n\nSigned-off-by: Muchun Song <songmuchun@bytedance.com>\n---\n mm/sparse-vmemmap.c | 11 ++---------\n 1 file changed, 2 insertions(+), 9 deletions(-)", "diff": "diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c\nindex 9f70559df4e8..2a6c3c82f9f5 100644\n--- a/mm/sparse-vmemmap.c\n+++ b/mm/sparse-vmemmap.c\n@@ -340,18 +340,11 @@ static __meminit struct page *vmemmap_get_tail(unsigned int order, struct zone *\n \tif (tail)\n \t\treturn tail;\n \n-\t/*\n-\t * Only allocate the page, but do not initialize it.\n-\t *\n-\t * Any initialization done here will be overwritten by memmap_init().\n-\t *\n-\t * hugetlb_vmemmap_init() will take care of initialization after\n-\t * memmap_init().\n-\t */\n-\n \tp = vmemmap_alloc_block_zero(PAGE_SIZE, node);\n \tif (!p)\n \t\treturn NULL;\n+\tfor (int i = 0; i < PAGE_SIZE / sizeof(struct page); i++)\n+\t\tinit_compound_tail(p + i, NULL, order, zone);\n \n \ttail = virt_to_page(p);\n \tzone->vmemmap_tails[idx] = tail;\n", "prefixes": [ "24/49" ] }