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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 
 36 static int pcpu_populate_chunk(struct pcpu_chunk *chunk,
 37                                int page_start, int page_end)
 38 {
 39         return 0;
 40 }
 41 
 42 static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk,
 43                                   int page_start, int page_end)
 44 {
 45         /* nada */
 46 }
 47 
 48 static 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 
 78 static 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 
 87 static struct page *pcpu_addr_to_page(void *addr)
 88 {
 89         return virt_to_page(addr);
 90 }
 91 
 92 static 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 

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