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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 
 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 }
109 

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