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Wed, 30 Sep 2026 07:07:22 -0700 (PDT) From: Muchun Song To: Andrew Morton , David Hildenbrand , Oscar Salvador , Madhavan Srinivasan , Michael Ellerman , Jonathan Corbet Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-doc@vger.kernel.org, Muchun Song , Lorenzo Stoakes , Mike Rapoport , Qi Zheng , Nicholas Piggin , Christophe Leroy , Ritesh Harjani , Shrikanth Hegde , Randy Dunlap , Muchun Song , Lance Yang Subject: [PATCH v6 01/12] mm/sparse-vmemmap: factor out shared vmemmap tail page allocation Date: Wed, 30 Sep 2026 22:06:16 +0800 Message-ID: <20260930140627.57431-2-songmuchun@bytedance.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260930140627.57431-1-songmuchun@bytedance.com> References: <20260930140627.57431-1-songmuchun@bytedance.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit HugeTLB and sparse-vmemmap each have their own helper to allocate the shared vmemmap tail page used by vmemmap optimization. Factor that logic into a common vmemmap_shared_tail_page() helper. It allocates the page through vmemmap_alloc_block(), initializes the tail struct pages, and uses cmpxchg() to install the per-zone shared page. This removes duplicate allocation logic while handling both early boot and runtime allocation through the same helper. Signed-off-by: Muchun Song Acked-by: Qi Zheng Acked-by: Mike Rapoport (Microsoft) Acked-by: David Hildenbrand (Arm) --- v6: - Move the constant declaration to the top of the function (suggested by David Hildenbrand) - Collect Acked-by from David Hildenbrand v5: - Move this patch before CONFIG_VMEMMAP_OPTIMIZATION is introduced v4: - Update the commit message for the renamed VMEMMAP_OPTIMIZATION config - Collect Acked-by from Mike Rapoport v2: - Collect Acked-by from Qi Zheng --- mm/hugetlb_vmemmap.c | 29 +----------------- mm/sparse-vmemmap.c | 70 ++++++++++++++++++++------------------------ mm/sparse.h | 3 ++ 3 files changed, 36 insertions(+), 66 deletions(-) diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c index f977d0a7e002..76765c97ff68 100644 --- a/mm/hugetlb_vmemmap.c +++ b/mm/hugetlb_vmemmap.c @@ -19,7 +19,6 @@ #include #include "hugetlb_vmemmap.h" #include "sparse.h" -#include "internal.h" /** * struct vmemmap_remap_walk - walk vmemmap page table @@ -493,32 +492,6 @@ static bool vmemmap_should_optimize_folio(const struct hstate *h, struct folio * return true; } -static struct page *vmemmap_get_tail(unsigned int order, struct zone *zone) -{ - const unsigned int idx = order - VMEMMAP_OPTIMIZATION_MIN_ORDER; - struct page *tail, *p; - int node = zone_to_nid(zone); - - tail = READ_ONCE(zone->vmemmap_tails[idx]); - if (likely(tail)) - return tail; - - tail = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0); - if (!tail) - return NULL; - - p = page_to_virt(tail); - for (int i = 0; i < PAGE_SIZE / sizeof(struct page); i++) - init_compound_tail(p + i, NULL, order, zone); - - if (cmpxchg(&zone->vmemmap_tails[idx], NULL, tail)) { - __free_page(tail); - tail = READ_ONCE(zone->vmemmap_tails[idx]); - } - - return tail; -} - static int __hugetlb_vmemmap_optimize_folio(const struct hstate *h, struct folio *folio, struct list_head *vmemmap_pages, @@ -535,7 +508,7 @@ static int __hugetlb_vmemmap_optimize_folio(const struct hstate *h, return ret; nid = folio_nid(folio); - vmemmap_tail = vmemmap_get_tail(h->order, folio_zone(folio)); + vmemmap_tail = vmemmap_shared_tail_page(h->order, folio_zone(folio)); if (!vmemmap_tail) return -ENOMEM; diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c index f22d815d7af0..9af349581fbd 100644 --- a/mm/sparse-vmemmap.c +++ b/mm/sparse-vmemmap.c @@ -42,27 +42,13 @@ #include "mm_init.h" #include "sparse.h" -/* - * Allocate a block of memory to be used to back the virtual memory map - * or to back the page tables that are used to create the mapping. - * Uses the main allocators if they are available, else bootmem. - */ - -static void * __ref __earlyonly_bootmem_alloc(int node, - unsigned long size, - unsigned long align, - unsigned long goal) -{ - return memmap_alloc(size, align, goal, node, false); -} - -void * __meminit vmemmap_alloc_block(unsigned long size, int node) +void __ref *vmemmap_alloc_block(unsigned long size, int node) { /* If the main allocator is up use that, fallback to bootmem. */ if (slab_is_available()) { gfp_t gfp_mask = GFP_KERNEL|__GFP_RETRY_MAYFAIL|__GFP_NOWARN; int order = get_order(size); - static bool warned __meminitdata; + static bool warned; struct page *page; page = alloc_pages_node(node, gfp_mask, order); @@ -76,8 +62,7 @@ void * __meminit vmemmap_alloc_block(unsigned long size, int node) } return NULL; } else - return __earlyonly_bootmem_alloc(node, size, size, - __pa(MAX_DMA_ADDRESS)); + return memmap_alloc(size, size, __pa(MAX_DMA_ADDRESS), node, false); } static void * __meminit altmap_alloc_block_buf(unsigned long size, @@ -185,34 +170,43 @@ static void * __meminit vmemmap_alloc_block_zero(unsigned long size, int node) } #ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP -static __meminit struct page *vmemmap_get_tail(unsigned int order, struct zone *zone) +struct page __ref *vmemmap_shared_tail_page(unsigned int order, struct zone *zone) { - struct page *p, *tail; - unsigned int idx; - int node = zone_to_nid(zone); + const unsigned int idx = order - VMEMMAP_OPTIMIZATION_MIN_ORDER; + struct page *page; + void *addr; - if (WARN_ON_ONCE(order < VMEMMAP_OPTIMIZATION_MIN_ORDER)) - return NULL; - if (WARN_ON_ONCE(order > MAX_FOLIO_ORDER)) + if (WARN_ON_ONCE(idx >= VMEMMAP_OPTIMIZATION_NR_ORDERS)) return NULL; - idx = order - VMEMMAP_OPTIMIZATION_MIN_ORDER; - tail = zone->vmemmap_tails[idx]; - if (tail) - return tail; - p = vmemmap_alloc_block_zero(PAGE_SIZE, node); - if (!p) + page = READ_ONCE(zone->vmemmap_tails[idx]); + if (page) + return page; + + addr = vmemmap_alloc_block(PAGE_SIZE, zone_to_nid(zone)); + if (!addr) return NULL; - for (int i = 0; i < PAGE_SIZE / sizeof(struct page); i++) - init_compound_tail(p + i, NULL, order, zone); - tail = virt_to_page(p); - zone->vmemmap_tails[idx] = tail; + for (int i = 0; i < PAGE_SIZE / sizeof(struct page); i++) { + page = (struct page *)addr + i; + mm_zero_struct_page(page); + init_compound_tail(page, NULL, order, zone); + } - return tail; + page = virt_to_page(addr); + if (cmpxchg(&zone->vmemmap_tails[idx], NULL, page) != NULL) { + if (slab_is_available()) + __free_page(page); + else + memblock_free(addr, PAGE_SIZE); + page = READ_ONCE(zone->vmemmap_tails[idx]); + } + + return page; } #else -static inline struct page *vmemmap_get_tail(unsigned int order, struct zone *zone) +static inline struct page *vmemmap_shared_tail_page(unsigned int order, + struct zone *zone) { return NULL; } @@ -229,7 +223,7 @@ static __meminit void *vmemmap_alloc_pte(unsigned long pfn, int node, return vmemmap_alloc_block_buf(PAGE_SIZE, node, altmap); zone = pfn_to_zone(pfn, node); - page = vmemmap_get_tail(order, zone); + page = vmemmap_shared_tail_page(order, zone); if (!page) return NULL; diff --git a/mm/sparse.h b/mm/sparse.h index d3a71ef4fad0..6e7aaeaa5594 100644 --- a/mm/sparse.h +++ b/mm/sparse.h @@ -142,6 +142,9 @@ static inline void sparse_sections_init(void) {} * mm/sparse-vmemmap.c */ #ifdef CONFIG_SPARSEMEM_VMEMMAP +#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP +struct page *vmemmap_shared_tail_page(unsigned int order, struct zone *zone); +#endif void sparse_init_subsection_map(void); int section_nr_vmemmap_pages(unsigned long pfn, unsigned long nr_pages, struct vmem_altmap *altmap, struct dev_pagemap *pgmap); -- 2.54.0