LXR linux/mm/percpu-km.c

   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,
  37                               int page_start, int page_end)
  38{
  39        return 0;
  40}
  41
  42static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk,
  43                                  int page_start, int page_end)
  44{
  45        /* nada */
  46}
  47
  48static 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
  78static 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
  87static struct page *pcpu_addr_to_page(void *addr)
  88{
  89        return virt_to_page(addr);
  90}
  91
  92static 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                pr_crit("can't handle more than one group\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                pr_warn("wasting %zu pages per chunk\n",
 107                        alloc_pages - nr_pages);
 108
 109        return 0;
 110}
 111