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Thu, 24 Sep 2026 00:58:17 -0700 (PDT) From: Muchun Song To: Madhavan Srinivasan , Mike Rapoport , Andrew Morton , David Hildenbrand Cc: Michael Ellerman , Nicholas Piggin , Christophe Leroy , Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Qi Zheng , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Muchun Song , muchun.song@linux.dev Subject: [PATCH v2 3/6] mm/sparse-vmemmap: drop Device DAX-specific population path Date: Thu, 24 Sep 2026 15:52:56 +0800 Message-ID: <20260924075259.2013039-4-songmuchun@bytedance.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260924075259.2013039-1-songmuchun@bytedance.com> References: <20260924075259.2013039-1-songmuchun@bytedance.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Stat-Signature: 14m1mnkzipuwopowqgc76cpak9isbaj5 X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: E86ED1A0003 X-HE-Tag: 1790236699-147810 X-HE-Meta: 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 zEBW0G8y /Ur4+4TLBTBfuTd68YAbNvcEWwHyQfNfITdrkAkuYXndTG4KA0atrTNM1ARrUPRH5ajf9mlbBwslxT7ueMiH20FvMjVManc6N14FToDOdTkHFf96rhNLWnZSTCYjts5WV4HMQvOiKEDVMK8+5yFBOy4b7xT4XlHtvTQRvo7uJNeHbesaC1NDZkF6CgGtCD4Gr0cowMgNHbnUlUzEFA5kDVtbkh9vS1cqLhfWnzOtbnPtztTUDCmj1I1N2iVMNu9OUYHETM2lSbQOrNFEsPW0HHVeEEwJMv0hpdyvZeNabonRRINnALpX9E8BKHQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: The common vmemmap path selects the shared page for optimized mappings itself, so Device DAX no longer needs vmemmap_populate_compound_pages() to find a shared tail page and pass its backing PFN through the generic population helpers. Remove the Device DAX-specific population path and let section memmap population always use vmemmap_populate(). The powerpc retains an architecture-specific compound-page implementation, so select it directly from radix__vmemmap_populate() for optimizable sections. Signed-off-by: Muchun Song Acked-by: Qi Zheng --- v2: - Collect Acked-by from Qi Zheng --- arch/powerpc/mm/book3s64/radix_pgtable.c | 3 + mm/mm_init.c | 2 +- mm/sparse-vmemmap.c | 71 +----------------------- 3 files changed, 5 insertions(+), 71 deletions(-) diff --git a/arch/powerpc/mm/book3s64/radix_pgtable.c b/arch/powerpc/mm/book3s64/radix_pgtable.c index 9ca28e4a610a..cb72d9ccf747 100644 --- a/arch/powerpc/mm/book3s64/radix_pgtable.c +++ b/arch/powerpc/mm/book3s64/radix_pgtable.c @@ -1122,7 +1122,10 @@ int __meminit radix__vmemmap_populate(unsigned long start, unsigned long end, in pud_t *pud; pmd_t *pmd; pte_t *pte; + unsigned long pfn = page_to_pfn((struct page *)start); + if (section_vmemmap_optimizable(__pfn_to_section(pfn))) + return vmemmap_populate_compound_pages(pfn, start, end, node, NULL); /* * If altmap is present, Make sure we align the start vmemmap addr * to PAGE_SIZE so that we calculate the correct start_pfn in diff --git a/mm/mm_init.c b/mm/mm_init.c index 56bb4567a494..1650d6bc1211 100644 --- a/mm/mm_init.c +++ b/mm/mm_init.c @@ -1046,7 +1046,7 @@ static void zone_device_page_init_from_template(struct page *page, * initialize is a lot smaller that the total amount of struct pages being * mapped. This is a paired / mild layering violation with explicit knowledge * of how the sparse_vmemmap internals handle compound pages in the lack - * of an altmap. See vmemmap_populate_compound_pages(). + * of an altmap. */ static inline unsigned long compound_nr_pages(unsigned long pfn, struct dev_pagemap *pgmap) diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c index cdcc93714a9a..4aae22beca21 100644 --- a/mm/sparse-vmemmap.c +++ b/mm/sparse-vmemmap.c @@ -466,71 +466,6 @@ int __meminit vmemmap_populate_hugepages(unsigned long start, unsigned long end, return 0; } -#ifndef vmemmap_populate_compound_pages -/* - * For compound pages bigger than section size (e.g. x86 1G compound - * pages with 2M subsection size) fill the rest of sections as tail - * pages. - * - * Note that memremap_pages() resets @nr_range value and will increment - * it after each range successful onlining. Thus the value or @nr_range - * at section memmap populate corresponds to the in-progress range - * being onlined here. - */ -static bool __meminit reuse_compound_section(unsigned long start_pfn, - struct dev_pagemap *pgmap) -{ - unsigned long nr_pages = pgmap_vmemmap_nr(pgmap); - unsigned long offset = start_pfn - - PHYS_PFN(pgmap->ranges[pgmap->nr_range].start); - - return !IS_ALIGNED(offset, nr_pages) && nr_pages > PAGES_PER_SUBSECTION; -} - -static int __meminit vmemmap_populate_compound_pages(unsigned long start_pfn, - unsigned long start, - unsigned long end, int node, - struct dev_pagemap *pgmap) -{ - unsigned long size, addr; - pte_t *pte; - int rc; - struct page *page; - unsigned int order = pfn_to_section_compound_order(start_pfn); - - page = vmemmap_shared_tail_page(order, device_zone(node)); - if (!page) - return -ENOMEM; - - if (reuse_compound_section(start_pfn, pgmap)) - return vmemmap_populate_range(start, end, node, NULL, - page_to_pfn(page)); - - size = min(end - start, (1UL << order) * sizeof(struct page)); - for (addr = start; addr < end; addr += size) { - unsigned long next, last = addr + size; - - /* Populate the head page vmemmap page */ - pte = vmemmap_populate_address(addr, node, NULL, -1); - if (!pte) - return -ENOMEM; - - /* - * Reuse the shared page for the rest of tail pages - * See layout diagram in Documentation/mm/vmemmap_dedup.rst - */ - next = addr + PAGE_SIZE; - rc = vmemmap_populate_range(next, last, node, NULL, - page_to_pfn(page)); - if (rc) - return -ENOMEM; - } - - return 0; -} - -#endif - struct page * __meminit __populate_section_memmap(unsigned long pfn, unsigned long nr_pages, int nid, struct vmem_altmap *altmap, struct dev_pagemap *pgmap) @@ -543,11 +478,7 @@ struct page * __meminit __populate_section_memmap(unsigned long pfn, !IS_ALIGNED(nr_pages, PAGES_PER_SUBSECTION))) return NULL; - if (pgmap && section_vmemmap_optimizable(__pfn_to_section(pfn))) - r = vmemmap_populate_compound_pages(pfn, start, end, nid, pgmap); - else - r = vmemmap_populate(start, end, nid, altmap); - + r = vmemmap_populate(start, end, nid, altmap); if (r < 0) return NULL; -- 2.54.0