linux/lib/genalloc.c
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   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 */
  27struct 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}
  39EXPORT_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 */
  51int 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}
  73EXPORT_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 */
  82void 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}
 103EXPORT_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 */
 113unsigned 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}
 150EXPORT_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 */
 160void 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}
 187EXPORT_SYMBOL(gen_pool_free);
 188