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) 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(void) 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(); 56 if (!chunk) 57 return NULL; 58 59 pages = alloc_pages(GFP_KERNEL, 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); 73 spin_unlock_irq(&pcpu_lock); 74 75 return chunk; 76 } 77 78 static void pcpu_destroy_chunk(struct pcpu_chunk *chunk) 79 { 80 const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT; 81 82 if (chunk && chunk->data) 83 __free_pages(chunk->data, order_base_2(nr_pages)); 84 pcpu_free_chunk(chunk); 85 } 86 87 static struct page *pcpu_addr_to_page(void *addr) 88 { 89 return virt_to_page(addr); 90 } 91 92 static int __init pcpu_verify_alloc_info(const struct pcpu_alloc_info *ai) 93 { 94 size_t nr_pages, alloc_pages; 95 96 /* all units must be in a single group */ 97 if (ai->nr_groups != 1) { 98 printk(KERN_CRIT "percpu: can't handle more than one groups\n"); 99 return -EINVAL; 100 } 101 102 nr_pages = (ai->groups[0].nr_units * ai->unit_size) >> PAGE_SHIFT; 103 alloc_pages = roundup_pow_of_two(nr_pages); 104 105 if (alloc_pages > nr_pages) 106 printk(KERN_WARNING "percpu: wasting %zu pages per chunk\n", 107 alloc_pages - nr_pages); 108 109 return 0; 110 } 111