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
  36 static 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
  46 static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk, int off, int size)
  47 {
  48         /* nada */
  49 }
  50
  51 static 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
  76 static 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
  85 static struct page *pcpu_addr_to_page(void *addr)
  86 {
  87         return virt_to_page(addr);
  88 }
  89
  90 static 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 }