lib/genalloc.c

   1 /*
   2  * Basic general purpose allocator for managing special purpose memory
   3  * not managed by the regular kmalloc/kfree interface.
   4  * Uses for this includes on-device special memory, uncached memory
   5  * etc.
   6  *
   7  * Copyright 2005 (C) Jes Sorensen <jes@trained-monkey.org>
   8  *
   9  * This source code is licensed under the GNU General Public License,
  10  * Version 2.  See the file COPYING for more details.
  11  */
  12
  13 #include <linux/module.h>
  14 #include <linux/genalloc.h>
  15
  16
  17 /*
  18  * Create a new special memory pool.
  19  *
  20  * @min_alloc_order: log base 2 of number of bytes each bitmap bit represents
  21  * @nid: node id of the node the pool structure should be allocated on, or -1
  22  */
  23 struct gen_pool *gen_pool_create(int min_alloc_order, int nid)
  24 {
  25         struct gen_pool *pool;
  26
  27         pool = kmalloc_node(sizeof(struct gen_pool), GFP_KERNEL, nid);
  28         if (pool != NULL) {
  29                 rwlock_init(&pool->lock);
  30                 INIT_LIST_HEAD(&pool->chunks);
  31                 pool->min_alloc_order = min_alloc_order;
  32         }
  33         return pool;
  34 }
  35 EXPORT_SYMBOL(gen_pool_create);
  36
  37
  38 /*
  39  * Add a new chunk of memory to the specified pool.
  40  *
  41  * @pool: pool to add new memory chunk to
  42  * @addr: starting address of memory chunk to add to pool
  43  * @size: size in bytes of the memory chunk to add to pool
  44  * @nid: node id of the node the chunk structure and bitmap should be
  45  *       allocated on, or -1
  46  */
  47 int gen_pool_add(struct gen_pool *pool, unsigned long addr, size_t size,
  48                  int nid)
  49 {
  50         struct gen_pool_chunk *chunk;
  51         int nbits = size >> pool->min_alloc_order;
  52         int nbytes = sizeof(struct gen_pool_chunk) +
  53                                 (nbits + BITS_PER_BYTE - 1) / BITS_PER_BYTE;
  54
  55         chunk = kmalloc_node(nbytes, GFP_KERNEL, nid);
  56         if (unlikely(chunk == NULL))
  57                 return -1;
  58
  59         memset(chunk, 0, nbytes);
  60         spin_lock_init(&chunk->lock);
  61         chunk->start_addr = addr;
  62         chunk->end_addr = addr + size;
  63
  64         write_lock(&pool->lock);
  65         list_add(&chunk->next_chunk, &pool->chunks);
  66         write_unlock(&pool->lock);
  67
  68         return 0;
  69 }
  70 EXPORT_SYMBOL(gen_pool_add);
  71
  72
  73 /*
  74  * Allocate the requested number of bytes from the specified pool.
  75  * Uses a first-fit algorithm.
  76  *
  77  * @pool: pool to allocate from
  78  * @size: number of bytes to allocate from the pool
  79  */
  80 unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size)
  81 {
  82         struct list_head *_chunk;
  83         struct gen_pool_chunk *chunk;
  84         unsigned long addr, flags;
  85         int order = pool->min_alloc_order;
  86         int nbits, bit, start_bit, end_bit;
  87
  88         if (size == 0)
  89                 return 0;
  90
  91         nbits = (size + (1UL << order) - 1) >> order;
  92
  93         read_lock(&pool->lock);
  94         list_for_each(_chunk, &pool->chunks) {
  95                 chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk);
  96
  97                 end_bit = (chunk->end_addr - chunk->start_addr) >> order;
  98                 end_bit -= nbits + 1;
  99
 100                 spin_lock_irqsave(&chunk->lock, flags);
 101                 bit = -1;
 102                 while (bit + 1 < end_bit) {
 103                         bit = find_next_zero_bit(chunk->bits, end_bit, bit + 1);
 104                         if (bit >= end_bit)
 105                                 break;
 106
 107                         start_bit = bit;
 108                         if (nbits > 1) {
 109                                 bit = find_next_bit(chunk->bits, bit + nbits,
 110                                                         bit + 1);
 111                                 if (bit - start_bit < nbits)
 112                                         continue;
 113                         }
 114
 115                         addr = chunk->start_addr +
 116                                             ((unsigned long)start_bit << order);
 117                         while (nbits--)
 118                                 __set_bit(start_bit++, &chunk->bits);
 119                         spin_unlock_irqrestore(&chunk->lock, flags);
 120                         read_unlock(&pool->lock);
 121                         return addr;
 122                 }
 123                 spin_unlock_irqrestore(&chunk->lock, flags);
 124         }
 125         read_unlock(&pool->lock);
 126         return 0;
 127 }
 128 EXPORT_SYMBOL(gen_pool_alloc);
 129
 130
 131 /*
 132  * Free the specified memory back to the specified pool.
 133  *
 134  * @pool: pool to free to
 135  * @addr: starting address of memory to free back to pool
 136  * @size: size in bytes of memory to free
 137  */
 138 void gen_pool_free(struct gen_pool *pool, unsigned long addr, size_t size)
 139 {
 140         struct list_head *_chunk;
 141         struct gen_pool_chunk *chunk;
 142         unsigned long flags;
 143         int order = pool->min_alloc_order;
 144         int bit, nbits;
 145
 146         nbits = (size + (1UL << order) - 1) >> order;
 147
 148         read_lock(&pool->lock);
 149         list_for_each(_chunk, &pool->chunks) {
 150                 chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk);
 151
 152                 if (addr >= chunk->start_addr && addr < chunk->end_addr) {
 153                         BUG_ON(addr + size > chunk->end_addr);
 154                         spin_lock_irqsave(&chunk->lock, flags);
 155                         bit = (addr - chunk->start_addr) >> order;
 156                         while (nbits--)
 157                                 __clear_bit(bit++, &chunk->bits);
 158                         spin_unlock_irqrestore(&chunk->lock, flags);
 159                         break;
 160                 }
 161         }
 162         BUG_ON(nbits > 0);
 163         read_unlock(&pool->lock);
 164 }
 165 EXPORT_SYMBOL(gen_pool_free);