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/slab.h>
  14 #include <linux/module.h>
  15 #include <linux/bitmap.h>
  16 #include <linux/genalloc.h>
  17
  18
  19 /**
  20  * gen_pool_create - create a new special memory pool
  21  * @min_alloc_order: log base 2 of number of bytes each bitmap bit represents
  22  * @nid: node id of the node the pool structure should be allocated on, or -1
  23  *
  24  * Create a new special memory pool that can be used to manage special purpose
  25  * memory not managed by the regular kmalloc/kfree interface.
  26  */
  27 struct gen_pool *gen_pool_create(int min_alloc_order, int nid)
  28 {
  29         struct gen_pool *pool;
  30
  31         pool = kmalloc_node(sizeof(struct gen_pool), GFP_KERNEL, nid);
  32         if (pool != NULL) {
  33                 rwlock_init(&pool->lock);
  34                 INIT_LIST_HEAD(&pool->chunks);
  35                 pool->min_alloc_order = min_alloc_order;
  36         }
  37         return pool;
  38 }
  39 EXPORT_SYMBOL(gen_pool_create);
  40
  41 /**
  42  * gen_pool_add - add a new chunk of special memory to the pool
  43  * @pool: pool to add new memory chunk to
  44  * @addr: starting address of memory chunk to add to pool
  45  * @size: size in bytes of the memory chunk to add to pool
  46  * @nid: node id of the node the chunk structure and bitmap should be
  47  *       allocated on, or -1
  48  *
  49  * Add a new chunk of special memory to the specified pool.
  50  */
  51 int gen_pool_add(struct gen_pool *pool, unsigned long addr, size_t size,
  52                  int nid)
  53 {
  54         struct gen_pool_chunk *chunk;
  55         int nbits = size >> pool->min_alloc_order;
  56         int nbytes = sizeof(struct gen_pool_chunk) +
  57                                 (nbits + BITS_PER_BYTE - 1) / BITS_PER_BYTE;
  58
  59         chunk = kmalloc_node(nbytes, GFP_KERNEL | __GFP_ZERO, nid);
  60         if (unlikely(chunk == NULL))
  61                 return -1;
  62
  63         spin_lock_init(&chunk->lock);
  64         chunk->start_addr = addr;
  65         chunk->end_addr = addr + size;
  66
  67         write_lock(&pool->lock);
  68         list_add(&chunk->next_chunk, &pool->chunks);
  69         write_unlock(&pool->lock);
  70
  71         return 0;
  72 }
  73 EXPORT_SYMBOL(gen_pool_add);
  74
  75 /**
  76  * gen_pool_destroy - destroy a special memory pool
  77  * @pool: pool to destroy
  78  *
  79  * Destroy the specified special memory pool. Verifies that there are no
  80  * outstanding allocations.
  81  */
  82 void gen_pool_destroy(struct gen_pool *pool)
  83 {
  84         struct list_head *_chunk, *_next_chunk;
  85         struct gen_pool_chunk *chunk;
  86         int order = pool->min_alloc_order;
  87         int bit, end_bit;
  88
  89
  90         list_for_each_safe(_chunk, _next_chunk, &pool->chunks) {
  91                 chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk);
  92                 list_del(&chunk->next_chunk);
  93
  94                 end_bit = (chunk->end_addr - chunk->start_addr) >> order;
  95                 bit = find_next_bit(chunk->bits, end_bit, 0);
  96                 BUG_ON(bit < end_bit);
  97
  98                 kfree(chunk);
  99         }
 100         kfree(pool);
 101         return;
 102 }
 103 EXPORT_SYMBOL(gen_pool_destroy);
 104
 105 /**
 106  * gen_pool_alloc - allocate special memory from the pool
 107  * @pool: pool to allocate from
 108  * @size: number of bytes to allocate from the pool
 109  *
 110  * Allocate the requested number of bytes from the specified pool.
 111  * Uses a first-fit algorithm.
 112  */
 113 unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size)
 114 {
 115         struct list_head *_chunk;
 116         struct gen_pool_chunk *chunk;
 117         unsigned long addr, flags;
 118         int order = pool->min_alloc_order;
 119         int nbits, start_bit, end_bit;
 120
 121         if (size == 0)
 122                 return 0;
 123
 124         nbits = (size + (1UL << order) - 1) >> order;
 125
 126         read_lock(&pool->lock);
 127         list_for_each(_chunk, &pool->chunks) {
 128                 chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk);
 129
 130                 end_bit = (chunk->end_addr - chunk->start_addr) >> order;
 131
 132                 spin_lock_irqsave(&chunk->lock, flags);
 133                 start_bit = bitmap_find_next_zero_area(chunk->bits, end_bit, 0,
 134                                                 nbits, 0);
 135                 if (start_bit >= end_bit) {
 136                         spin_unlock_irqrestore(&chunk->lock, flags);
 137                         continue;
 138                 }
 139
 140                 addr = chunk->start_addr + ((unsigned long)start_bit << order);
 141
 142                 bitmap_set(chunk->bits, start_bit, nbits);
 143                 spin_unlock_irqrestore(&chunk->lock, flags);
 144                 read_unlock(&pool->lock);
 145                 return addr;
 146         }
 147         read_unlock(&pool->lock);
 148         return 0;
 149 }
 150 EXPORT_SYMBOL(gen_pool_alloc);
 151
 152 /**
 153  * gen_pool_free - free allocated special memory back to the pool
 154  * @pool: pool to free to
 155  * @addr: starting address of memory to free back to pool
 156  * @size: size in bytes of memory to free
 157  *
 158  * Free previously allocated special memory back to the specified pool.
 159  */
 160 void gen_pool_free(struct gen_pool *pool, unsigned long addr, size_t size)
 161 {
 162         struct list_head *_chunk;
 163         struct gen_pool_chunk *chunk;
 164         unsigned long flags;
 165         int order = pool->min_alloc_order;
 166         int bit, nbits;
 167
 168         nbits = (size + (1UL << order) - 1) >> order;
 169
 170         read_lock(&pool->lock);
 171         list_for_each(_chunk, &pool->chunks) {
 172                 chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk);
 173
 174                 if (addr >= chunk->start_addr && addr < chunk->end_addr) {
 175                         BUG_ON(addr + size > chunk->end_addr);
 176                         spin_lock_irqsave(&chunk->lock, flags);
 177                         bit = (addr - chunk->start_addr) >> order;
 178                         while (nbits--)
 179                                 __clear_bit(bit++, chunk->bits);
 180                         spin_unlock_irqrestore(&chunk->lock, flags);
 181                         break;
 182                 }
 183         }
 184         BUG_ON(nbits > 0);
 185         read_unlock(&pool->lock);
 186 }
 187 EXPORT_SYMBOL(gen_pool_free);