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