linux/mm/mempool.c
<<
>>
Prefs
   1/*
   2 *  linux/mm/mempool.c
   3 *
   4 *  memory buffer pool support. Such pools are mostly used
   5 *  for guaranteed, deadlock-free memory allocations during
   6 *  extreme VM load.
   7 *
   8 *  started by Ingo Molnar, Copyright (C) 2001
   9 */
  10
  11#include <linux/mm.h>
  12#include <linux/slab.h>
  13#include <linux/module.h>
  14#include <linux/mempool.h>
  15#include <linux/blkdev.h>
  16#include <linux/writeback.h>
  17
  18static void add_element(mempool_t *pool, void *element)
  19{
  20        BUG_ON(pool->curr_nr >= pool->min_nr);
  21        pool->elements[pool->curr_nr++] = element;
  22}
  23
  24static void *remove_element(mempool_t *pool)
  25{
  26        BUG_ON(pool->curr_nr <= 0);
  27        return pool->elements[--pool->curr_nr];
  28}
  29
  30static void free_pool(mempool_t *pool)
  31{
  32        while (pool->curr_nr) {
  33                void *element = remove_element(pool);
  34                pool->free(element, pool->pool_data);
  35        }
  36        kfree(pool->elements);
  37        kfree(pool);
  38}
  39
  40/**
  41 * mempool_create - create a memory pool
  42 * @min_nr:    the minimum number of elements guaranteed to be
  43 *             allocated for this pool.
  44 * @alloc_fn:  user-defined element-allocation function.
  45 * @free_fn:   user-defined element-freeing function.
  46 * @pool_data: optional private data available to the user-defined functions.
  47 *
  48 * this function creates and allocates a guaranteed size, preallocated
  49 * memory pool. The pool can be used from the mempool_alloc() and mempool_free()
  50 * functions. This function might sleep. Both the alloc_fn() and the free_fn()
  51 * functions might sleep - as long as the mempool_alloc() function is not called
  52 * from IRQ contexts.
  53 */
  54mempool_t *mempool_create(int min_nr, mempool_alloc_t *alloc_fn,
  55                                mempool_free_t *free_fn, void *pool_data)
  56{
  57        return  mempool_create_node(min_nr,alloc_fn,free_fn, pool_data,-1);
  58}
  59EXPORT_SYMBOL(mempool_create);
  60
  61mempool_t *mempool_create_node(int min_nr, mempool_alloc_t *alloc_fn,
  62                        mempool_free_t *free_fn, void *pool_data, int node_id)
  63{
  64        mempool_t *pool;
  65        pool = kmalloc_node(sizeof(*pool), GFP_KERNEL | __GFP_ZERO, node_id);
  66        if (!pool)
  67                return NULL;
  68        pool->elements = kmalloc_node(min_nr * sizeof(void *),
  69                                        GFP_KERNEL, node_id);
  70        if (!pool->elements) {
  71                kfree(pool);
  72                return NULL;
  73        }
  74        spin_lock_init(&pool->lock);
  75        pool->min_nr = min_nr;
  76        pool->pool_data = pool_data;
  77        init_waitqueue_head(&pool->wait);
  78        pool->alloc = alloc_fn;
  79        pool->free = free_fn;
  80
  81        /*
  82         * First pre-allocate the guaranteed number of buffers.
  83         */
  84        while (pool->curr_nr < pool->min_nr) {
  85                void *element;
  86
  87                element = pool->alloc(GFP_KERNEL, pool->pool_data);
  88                if (unlikely(!element)) {
  89                        free_pool(pool);
  90                        return NULL;
  91                }
  92                add_element(pool, element);
  93        }
  94        return pool;
  95}
  96EXPORT_SYMBOL(mempool_create_node);
  97
  98/**
  99 * mempool_resize - resize an existing memory pool
 100 * @pool:       pointer to the memory pool which was allocated via
 101 *              mempool_create().
 102 * @new_min_nr: the new minimum number of elements guaranteed to be
 103 *              allocated for this pool.
 104 * @gfp_mask:   the usual allocation bitmask.
 105 *
 106 * This function shrinks/grows the pool. In the case of growing,
 107 * it cannot be guaranteed that the pool will be grown to the new
 108 * size immediately, but new mempool_free() calls will refill it.
 109 *
 110 * Note, the caller must guarantee that no mempool_destroy is called
 111 * while this function is running. mempool_alloc() & mempool_free()
 112 * might be called (eg. from IRQ contexts) while this function executes.
 113 */
 114int mempool_resize(mempool_t *pool, int new_min_nr, gfp_t gfp_mask)
 115{
 116        void *element;
 117        void **new_elements;
 118        unsigned long flags;
 119
 120        BUG_ON(new_min_nr <= 0);
 121
 122        spin_lock_irqsave(&pool->lock, flags);
 123        if (new_min_nr <= pool->min_nr) {
 124                while (new_min_nr < pool->curr_nr) {
 125                        element = remove_element(pool);
 126                        spin_unlock_irqrestore(&pool->lock, flags);
 127                        pool->free(element, pool->pool_data);
 128                        spin_lock_irqsave(&pool->lock, flags);
 129                }
 130                pool->min_nr = new_min_nr;
 131                goto out_unlock;
 132        }
 133        spin_unlock_irqrestore(&pool->lock, flags);
 134
 135        /* Grow the pool */
 136        new_elements = kmalloc(new_min_nr * sizeof(*new_elements), gfp_mask);
 137        if (!new_elements)
 138                return -ENOMEM;
 139
 140        spin_lock_irqsave(&pool->lock, flags);
 141        if (unlikely(new_min_nr <= pool->min_nr)) {
 142                /* Raced, other resize will do our work */
 143                spin_unlock_irqrestore(&pool->lock, flags);
 144                kfree(new_elements);
 145                goto out;
 146        }
 147        memcpy(new_elements, pool->elements,
 148                        pool->curr_nr * sizeof(*new_elements));
 149        kfree(pool->elements);
 150        pool->elements = new_elements;
 151        pool->min_nr = new_min_nr;
 152
 153        while (pool->curr_nr < pool->min_nr) {
 154                spin_unlock_irqrestore(&pool->lock, flags);
 155                element = pool->alloc(gfp_mask, pool->pool_data);
 156                if (!element)
 157                        goto out;
 158                spin_lock_irqsave(&pool->lock, flags);
 159                if (pool->curr_nr < pool->min_nr) {
 160                        add_element(pool, element);
 161                } else {
 162                        spin_unlock_irqrestore(&pool->lock, flags);
 163                        pool->free(element, pool->pool_data);   /* Raced */
 164                        goto out;
 165                }
 166        }
 167out_unlock:
 168        spin_unlock_irqrestore(&pool->lock, flags);
 169out:
 170        return 0;
 171}
 172EXPORT_SYMBOL(mempool_resize);
 173
 174/**
 175 * mempool_destroy - deallocate a memory pool
 176 * @pool:      pointer to the memory pool which was allocated via
 177 *             mempool_create().
 178 *
 179 * this function only sleeps if the free_fn() function sleeps. The caller
 180 * has to guarantee that all elements have been returned to the pool (ie:
 181 * freed) prior to calling mempool_destroy().
 182 */
 183void mempool_destroy(mempool_t *pool)
 184{
 185        /* Check for outstanding elements */
 186        BUG_ON(pool->curr_nr != pool->min_nr);
 187        free_pool(pool);
 188}
 189EXPORT_SYMBOL(mempool_destroy);
 190
 191/**
 192 * mempool_alloc - allocate an element from a specific memory pool
 193 * @pool:      pointer to the memory pool which was allocated via
 194 *             mempool_create().
 195 * @gfp_mask:  the usual allocation bitmask.
 196 *
 197 * this function only sleeps if the alloc_fn() function sleeps or
 198 * returns NULL. Note that due to preallocation, this function
 199 * *never* fails when called from process contexts. (it might
 200 * fail if called from an IRQ context.)
 201 */
 202void * mempool_alloc(mempool_t *pool, gfp_t gfp_mask)
 203{
 204        void *element;
 205        unsigned long flags;
 206        wait_queue_t wait;
 207        gfp_t gfp_temp;
 208
 209        might_sleep_if(gfp_mask & __GFP_WAIT);
 210
 211        gfp_mask |= __GFP_NOMEMALLOC;   /* don't allocate emergency reserves */
 212        gfp_mask |= __GFP_NORETRY;      /* don't loop in __alloc_pages */
 213        gfp_mask |= __GFP_NOWARN;       /* failures are OK */
 214
 215        gfp_temp = gfp_mask & ~(__GFP_WAIT|__GFP_IO);
 216
 217repeat_alloc:
 218
 219        element = pool->alloc(gfp_temp, pool->pool_data);
 220        if (likely(element != NULL))
 221                return element;
 222
 223        spin_lock_irqsave(&pool->lock, flags);
 224        if (likely(pool->curr_nr)) {
 225                element = remove_element(pool);
 226                spin_unlock_irqrestore(&pool->lock, flags);
 227                return element;
 228        }
 229        spin_unlock_irqrestore(&pool->lock, flags);
 230
 231        /* We must not sleep in the GFP_ATOMIC case */
 232        if (!(gfp_mask & __GFP_WAIT))
 233                return NULL;
 234
 235        /* Now start performing page reclaim */
 236        gfp_temp = gfp_mask;
 237        init_wait(&wait);
 238        prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE);
 239        smp_mb();
 240        if (!pool->curr_nr) {
 241                /*
 242                 * FIXME: this should be io_schedule().  The timeout is there
 243                 * as a workaround for some DM problems in 2.6.18.
 244                 */
 245                io_schedule_timeout(5*HZ);
 246        }
 247        finish_wait(&pool->wait, &wait);
 248
 249        goto repeat_alloc;
 250}
 251EXPORT_SYMBOL(mempool_alloc);
 252
 253/**
 254 * mempool_free - return an element to the pool.
 255 * @element:   pool element pointer.
 256 * @pool:      pointer to the memory pool which was allocated via
 257 *             mempool_create().
 258 *
 259 * this function only sleeps if the free_fn() function sleeps.
 260 */
 261void mempool_free(void *element, mempool_t *pool)
 262{
 263        unsigned long flags;
 264
 265        if (unlikely(element == NULL))
 266                return;
 267
 268        smp_mb();
 269        if (pool->curr_nr < pool->min_nr) {
 270                spin_lock_irqsave(&pool->lock, flags);
 271                if (pool->curr_nr < pool->min_nr) {
 272                        add_element(pool, element);
 273                        spin_unlock_irqrestore(&pool->lock, flags);
 274                        wake_up(&pool->wait);
 275                        return;
 276                }
 277                spin_unlock_irqrestore(&pool->lock, flags);
 278        }
 279        pool->free(element, pool->pool_data);
 280}
 281EXPORT_SYMBOL(mempool_free);
 282
 283/*
 284 * A commonly used alloc and free fn.
 285 */
 286void *mempool_alloc_slab(gfp_t gfp_mask, void *pool_data)
 287{
 288        struct kmem_cache *mem = pool_data;
 289        return kmem_cache_alloc(mem, gfp_mask);
 290}
 291EXPORT_SYMBOL(mempool_alloc_slab);
 292
 293void mempool_free_slab(void *element, void *pool_data)
 294{
 295        struct kmem_cache *mem = pool_data;
 296        kmem_cache_free(mem, element);
 297}
 298EXPORT_SYMBOL(mempool_free_slab);
 299
 300/*
 301 * A commonly used alloc and free fn that kmalloc/kfrees the amount of memory
 302 * specified by pool_data
 303 */
 304void *mempool_kmalloc(gfp_t gfp_mask, void *pool_data)
 305{
 306        size_t size = (size_t)pool_data;
 307        return kmalloc(size, gfp_mask);
 308}
 309EXPORT_SYMBOL(mempool_kmalloc);
 310
 311void mempool_kfree(void *element, void *pool_data)
 312{
 313        kfree(element);
 314}
 315EXPORT_SYMBOL(mempool_kfree);
 316
 317/*
 318 * A simple mempool-backed page allocator that allocates pages
 319 * of the order specified by pool_data.
 320 */
 321void *mempool_alloc_pages(gfp_t gfp_mask, void *pool_data)
 322{
 323        int order = (int)(long)pool_data;
 324        return alloc_pages(gfp_mask, order);
 325}
 326EXPORT_SYMBOL(mempool_alloc_pages);
 327
 328void mempool_free_pages(void *element, void *pool_data)
 329{
 330        int order = (int)(long)pool_data;
 331        __free_pages(element, order);
 332}
 333EXPORT_SYMBOL(mempool_free_pages);
 334
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.