1 /* 2 * mm/percpu-km.c - kernel memory based chunk allocation 3 * 4 * Copyright (C) 2010 SUSE Linux Products GmbH 5 * Copyright (C) 2010 Tejun Heo <tj@kernel.org> 6 * 7 * This file is released under the GPLv2. 8 * 9 * Chunks are allocated as a contiguous kernel memory using gfp 10 * allocation. This is to be used on nommu architectures. 11 * 12 * To use percpu-km, 13 * 14 * - define CONFIG_NEED_PER_CPU_KM from the arch Kconfig. 15 * 16 * - CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK must not be defined. It's 17 * not compatible with PER_CPU_KM. EMBED_FIRST_CHUNK should work 18 * fine. 19 * 20 * - NUMA is not supported. When setting up the first chunk, 21 * @cpu_distance_fn should be NULL or report all CPUs to be nearer 22 * than or at LOCAL_DISTANCE. 23 * 24 * - It's best if the chunk size is power of two multiple of 25 * PAGE_SIZE. Because each chunk is allocated as a contiguous 26 * kernel memory block using alloc_pages(), memory will be wasted if 27 * chunk size is not aligned. percpu-km code will whine about it. 28 */ 29 30 #if defined(CONFIG_SMP) && defined(CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK) 31 #error "contiguous percpu allocation is incompatible with paged first chunk" 32 #endif 33 34 #include <linux/log2.h> 35 36 static int pcpu_populate_chunk(struct pcpu_chunk *chunk, 37 int page_start, int page_end, gfp_t gfp) 38 { 39 return 0; 40 } 41 42 static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk, 43 int page_start, int page_end) 44 { 45 /* nada */ 46 } 47 48 static struct pcpu_chunk *pcpu_create_chunk(gfp_t gfp) 49 { 50 const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT; 51 struct pcpu_chunk *chunk; 52 struct page *pages; 53 int i; 54 55 chunk = pcpu_alloc_chunk(gfp); 56 if (!chunk) 57 return NULL; 58 59 pages = alloc_pages(gfp, order_base_2(nr_pages)); 60 if (!pages) { 61 pcpu_free_chunk(chunk); 62 return NULL; 63 } 64 65 for (i = 0; i < nr_pages; i++) 66 pcpu_set_page_chunk(nth_page(pages, i), chunk); 67 68 chunk->data = pages; 69 chunk->base_addr = page_address(pages) - pcpu_group_offsets[0]; 70 71 spin_lock_irq(&pcpu_lock); 72 pcpu_chunk_populated(chunk, 0, nr_pages, false); 73 spin_unlock_irq(&pcpu_lock); 74 75 pcpu_stats_chunk_alloc(); 76 trace_percpu_create_chunk(chunk->base_addr); 77 78 return chunk; 79 } 80 81 static void pcpu_destroy_chunk(struct pcpu_chunk *chunk) 82 { 83 const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT; 84 85 if (!chunk) 86 return; 87 88 pcpu_stats_chunk_dealloc(); 89 trace_percpu_destroy_chunk(chunk->base_addr); 90 91 if (chunk->data) 92 __free_pages(chunk->data, order_base_2(nr_pages)); 93 pcpu_free_chunk(chunk); 94 } 95 96 static struct page *pcpu_addr_to_page(void *addr) 97 { 98 return virt_to_page(addr); 99 } 100 101 static int __init pcpu_verify_alloc_info(const struct pcpu_alloc_info *ai) 102 { 103 size_t nr_pages, alloc_pages; 104 105 /* all units must be in a single group */ 106 if (ai->nr_groups != 1) { 107 pr_crit("can't handle more than one group\n"); 108 return -EINVAL; 109 } 110 111 nr_pages = (ai->groups[0].nr_units * ai->unit_size) >> PAGE_SHIFT; 112 alloc_pages = roundup_pow_of_two(nr_pages); 113 114 if (alloc_pages > nr_pages) 115 pr_warn("wasting %zu pages per chunk\n", 116 alloc_pages - nr_pages); 117 118 return 0; 119 } 120