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Mon, 28 Sep 2026 22:33:33 -0700 (PDT) Received: from G6L4RL2QG9 ([139.177.225.254]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2df9142bafesm49251765ad.51.2026.09.28.22.33.25 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Mon, 28 Sep 2026 22:33:32 -0700 (PDT) From: Muchun Song To: Madhavan Srinivasan , Mike Rapoport , Andrew Morton , David Hildenbrand Cc: Michael Ellerman , Nicholas Piggin , Christophe Leroy , Ritesh Harjani , Shrikanth Hegde , 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 v3 3/6] mm/sparse-vmemmap: drop Device DAX-specific population path Date: Tue, 29 Sep 2026 13:32:28 +0800 Message-ID: <20260929053231.66085-4-songmuchun@bytedance.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260929053231.66085-1-songmuchun@bytedance.com> References: <20260929053231.66085-1-songmuchun@bytedance.com> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 --- v3: - Use the public order-based optimization predicate in the powerpc path 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..fd13fa91e5c0 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 (vmemmap_optimizable_order(pfn_to_section_compound_order(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 ee4c113ca938..dee95e520376 100644 --- a/mm/sparse-vmemmap.c +++ b/mm/sparse-vmemmap.c @@ -499,71 +499,6 @@ 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) @@ -576,11 +511,7 @@ 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