linux/mm/percpu-km.c
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   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}
 109
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