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
 36static int pcpu_populate_chunk(struct pcpu_chunk *chunk, int off, int size)
 37{
 38	unsigned int cpu;
 39
 40	for_each_possible_cpu(cpu)
 41		memset((void *)pcpu_chunk_addr(chunk, cpu, 0) + off, 0, size);
 42
 43	return 0;
 44}
 45
 46static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk, int off, int size)
 47{
 48	/* nada */
 49}
 50
 51static struct pcpu_chunk *pcpu_create_chunk(void)
 52{
 53	const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT;
 54	struct pcpu_chunk *chunk;
 55	struct page *pages;
 56	int i;
 57
 58	chunk = pcpu_alloc_chunk();
 59	if (!chunk)
 60		return NULL;
 61
 62	pages = alloc_pages(GFP_KERNEL, order_base_2(nr_pages));
 63	if (!pages) {
 64		pcpu_free_chunk(chunk);
 65		return NULL;
 66	}
 67
 68	for (i = 0; i < nr_pages; i++)
 69		pcpu_set_page_chunk(nth_page(pages, i), chunk);
 70
 71	chunk->data = pages;
 72	chunk->base_addr = page_address(pages) - pcpu_group_offsets[0];
 73	return chunk;
 74}
 75
 76static void pcpu_destroy_chunk(struct pcpu_chunk *chunk)
 77{
 78	const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT;
 79
 80	if (chunk && chunk->data)
 81		__free_pages(chunk->data, order_base_2(nr_pages));
 82	pcpu_free_chunk(chunk);
 83}
 84
 85static struct page *pcpu_addr_to_page(void *addr)
 86{
 87	return virt_to_page(addr);
 88}
 89
 90static int __init pcpu_verify_alloc_info(const struct pcpu_alloc_info *ai)
 91{
 92	size_t nr_pages, alloc_pages;
 93
 94	/* all units must be in a single group */
 95	if (ai->nr_groups != 1) {
 96		printk(KERN_CRIT "percpu: can't handle more than one groups\n");
 97		return -EINVAL;
 98	}
 99
100	nr_pages = (ai->groups[0].nr_units * ai->unit_size) >> PAGE_SHIFT;
101	alloc_pages = roundup_pow_of_two(nr_pages);
102
103	if (alloc_pages > nr_pages)
104		printk(KERN_WARNING "percpu: wasting %zu pages per chunk\n",
105		       alloc_pages - nr_pages);
106
107	return 0;
108}