Linux Cross Reference
Linux-2.6.17/mm/mempool.c

   /*
    *  linux/mm/mempool.c
    *
    *  memory buffer pool support. Such pools are mostly used
    *  for guaranteed, deadlock-free memory allocations during
    *  extreme VM load.
    *
    *  started by Ingo Molnar, Copyright (C) 2001
    */
  
  #include <linux/mm.h>
  #include <linux/slab.h>
  #include <linux/module.h>
  #include <linux/mempool.h>
  #include <linux/blkdev.h>
  #include <linux/writeback.h>
  
  static void add_element(mempool_t *pool, void *element)
  {
          BUG_ON(pool->curr_nr >= pool->min_nr);
          pool->elements[pool->curr_nr++] = element;
  }
  
  static void *remove_element(mempool_t *pool)
  {
          BUG_ON(pool->curr_nr <= 0);
          return pool->elements[--pool->curr_nr];
  }
  
  static void free_pool(mempool_t *pool)
  {
          while (pool->curr_nr) {
                  void *element = remove_element(pool);
                  pool->free(element, pool->pool_data);
          }
          kfree(pool->elements);
          kfree(pool);
  }
  
  /**
   * mempool_create - create a memory pool
   * @min_nr:    the minimum number of elements guaranteed to be
   *             allocated for this pool.
   * @alloc_fn:  user-defined element-allocation function.
   * @free_fn:   user-defined element-freeing function.
   * @pool_data: optional private data available to the user-defined functions.
   *
   * this function creates and allocates a guaranteed size, preallocated
   * memory pool. The pool can be used from the mempool_alloc and mempool_free
   * functions. This function might sleep. Both the alloc_fn() and the free_fn()
   * functions might sleep - as long as the mempool_alloc function is not called
   * from IRQ contexts.
   */
  mempool_t *mempool_create(int min_nr, mempool_alloc_t *alloc_fn,
                                  mempool_free_t *free_fn, void *pool_data)
  {
          return  mempool_create_node(min_nr,alloc_fn,free_fn, pool_data,-1);
  }
  EXPORT_SYMBOL(mempool_create);
  
  mempool_t *mempool_create_node(int min_nr, mempool_alloc_t *alloc_fn,
                          mempool_free_t *free_fn, void *pool_data, int node_id)
  {
          mempool_t *pool;
          pool = kmalloc_node(sizeof(*pool), GFP_KERNEL, node_id);
          if (!pool)
                  return NULL;
          memset(pool, 0, sizeof(*pool));
          pool->elements = kmalloc_node(min_nr * sizeof(void *),
                                          GFP_KERNEL, node_id);
          if (!pool->elements) {
                  kfree(pool);
                  return NULL;
          }
          spin_lock_init(&pool->lock);
          pool->min_nr = min_nr;
          pool->pool_data = pool_data;
          init_waitqueue_head(&pool->wait);
          pool->alloc = alloc_fn;
          pool->free = free_fn;
  
          /*
           * First pre-allocate the guaranteed number of buffers.
           */
          while (pool->curr_nr < pool->min_nr) {
                  void *element;
  
                  element = pool->alloc(GFP_KERNEL, pool->pool_data);
                  if (unlikely(!element)) {
                          free_pool(pool);
                          return NULL;
                  }
                  add_element(pool, element);
          }
          return pool;
  }
  EXPORT_SYMBOL(mempool_create_node);
  
  /**
  * mempool_resize - resize an existing memory pool
  * @pool:       pointer to the memory pool which was allocated via
  *              mempool_create().
  * @new_min_nr: the new minimum number of elements guaranteed to be
  *              allocated for this pool.
  * @gfp_mask:   the usual allocation bitmask.
  *
  * This function shrinks/grows the pool. In the case of growing,
  * it cannot be guaranteed that the pool will be grown to the new
  * size immediately, but new mempool_free() calls will refill it.
  *
  * Note, the caller must guarantee that no mempool_destroy is called
  * while this function is running. mempool_alloc() & mempool_free()
  * might be called (eg. from IRQ contexts) while this function executes.
  */
 int mempool_resize(mempool_t *pool, int new_min_nr, gfp_t gfp_mask)
 {
         void *element;
         void **new_elements;
         unsigned long flags;
 
         BUG_ON(new_min_nr <= 0);
 
         spin_lock_irqsave(&pool->lock, flags);
         if (new_min_nr <= pool->min_nr) {
                 while (new_min_nr < pool->curr_nr) {
                         element = remove_element(pool);
                         spin_unlock_irqrestore(&pool->lock, flags);
                         pool->free(element, pool->pool_data);
                         spin_lock_irqsave(&pool->lock, flags);
                 }
                 pool->min_nr = new_min_nr;
                 goto out_unlock;
         }
         spin_unlock_irqrestore(&pool->lock, flags);
 
         /* Grow the pool */
         new_elements = kmalloc(new_min_nr * sizeof(*new_elements), gfp_mask);
         if (!new_elements)
                 return -ENOMEM;
 
         spin_lock_irqsave(&pool->lock, flags);
         if (unlikely(new_min_nr <= pool->min_nr)) {
                 /* Raced, other resize will do our work */
                 spin_unlock_irqrestore(&pool->lock, flags);
                 kfree(new_elements);
                 goto out;
         }
         memcpy(new_elements, pool->elements,
                         pool->curr_nr * sizeof(*new_elements));
         kfree(pool->elements);
         pool->elements = new_elements;
         pool->min_nr = new_min_nr;
 
         while (pool->curr_nr < pool->min_nr) {
                 spin_unlock_irqrestore(&pool->lock, flags);
                 element = pool->alloc(gfp_mask, pool->pool_data);
                 if (!element)
                         goto out;
                 spin_lock_irqsave(&pool->lock, flags);
                 if (pool->curr_nr < pool->min_nr) {
                         add_element(pool, element);
                 } else {
                         spin_unlock_irqrestore(&pool->lock, flags);
                         pool->free(element, pool->pool_data);   /* Raced */
                         goto out;
                 }
         }
 out_unlock:
         spin_unlock_irqrestore(&pool->lock, flags);
 out:
         return 0;
 }
 EXPORT_SYMBOL(mempool_resize);
 
 /**
  * mempool_destroy - deallocate a memory pool
  * @pool:      pointer to the memory pool which was allocated via
  *             mempool_create().
  *
  * this function only sleeps if the free_fn() function sleeps. The caller
  * has to guarantee that all elements have been returned to the pool (ie:
  * freed) prior to calling mempool_destroy().
  */
 void mempool_destroy(mempool_t *pool)
 {
         /* Check for outstanding elements */
         BUG_ON(pool->curr_nr != pool->min_nr);
         free_pool(pool);
 }
 EXPORT_SYMBOL(mempool_destroy);
 
 /**
  * mempool_alloc - allocate an element from a specific memory pool
  * @pool:      pointer to the memory pool which was allocated via
  *             mempool_create().
  * @gfp_mask:  the usual allocation bitmask.
  *
  * this function only sleeps if the alloc_fn function sleeps or
  * returns NULL. Note that due to preallocation, this function
  * *never* fails when called from process contexts. (it might
  * fail if called from an IRQ context.)
  */
 void * mempool_alloc(mempool_t *pool, gfp_t gfp_mask)
 {
         void *element;
         unsigned long flags;
         wait_queue_t wait;
         gfp_t gfp_temp;
 
         might_sleep_if(gfp_mask & __GFP_WAIT);
 
         gfp_mask |= __GFP_NOMEMALLOC;   /* don't allocate emergency reserves */
         gfp_mask |= __GFP_NORETRY;      /* don't loop in __alloc_pages */
         gfp_mask |= __GFP_NOWARN;       /* failures are OK */
 
         gfp_temp = gfp_mask & ~(__GFP_WAIT|__GFP_IO);
 
 repeat_alloc:
 
         element = pool->alloc(gfp_temp, pool->pool_data);
         if (likely(element != NULL))
                 return element;
 
         spin_lock_irqsave(&pool->lock, flags);
         if (likely(pool->curr_nr)) {
                 element = remove_element(pool);
                 spin_unlock_irqrestore(&pool->lock, flags);
                 return element;
         }
         spin_unlock_irqrestore(&pool->lock, flags);
 
         /* We must not sleep in the GFP_ATOMIC case */
         if (!(gfp_mask & __GFP_WAIT))
                 return NULL;
 
         /* Now start performing page reclaim */
         gfp_temp = gfp_mask;
         init_wait(&wait);
         prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE);
         smp_mb();
         if (!pool->curr_nr)
                 io_schedule();
         finish_wait(&pool->wait, &wait);
 
         goto repeat_alloc;
 }
 EXPORT_SYMBOL(mempool_alloc);
 
 /**
  * mempool_free - return an element to the pool.
  * @element:   pool element pointer.
  * @pool:      pointer to the memory pool which was allocated via
  *             mempool_create().
  *
  * this function only sleeps if the free_fn() function sleeps.
  */
 void mempool_free(void *element, mempool_t *pool)
 {
         unsigned long flags;
 
         smp_mb();
         if (pool->curr_nr < pool->min_nr) {
                 spin_lock_irqsave(&pool->lock, flags);
                 if (pool->curr_nr < pool->min_nr) {
                         add_element(pool, element);
                         spin_unlock_irqrestore(&pool->lock, flags);
                         wake_up(&pool->wait);
                         return;
                 }
                 spin_unlock_irqrestore(&pool->lock, flags);
         }
         pool->free(element, pool->pool_data);
 }
 EXPORT_SYMBOL(mempool_free);
 
 /*
  * A commonly used alloc and free fn.
  */
 void *mempool_alloc_slab(gfp_t gfp_mask, void *pool_data)
 {
         struct kmem_cache *mem = pool_data;
         return kmem_cache_alloc(mem, gfp_mask);
 }
 EXPORT_SYMBOL(mempool_alloc_slab);
 
 void mempool_free_slab(void *element, void *pool_data)
 {
         struct kmem_cache *mem = pool_data;
         kmem_cache_free(mem, element);
 }
 EXPORT_SYMBOL(mempool_free_slab);
 
 /*
  * A commonly used alloc and free fn that kmalloc/kfrees the amount of memory
  * specfied by pool_data
  */
 void *mempool_kmalloc(gfp_t gfp_mask, void *pool_data)
 {
         size_t size = (size_t)(long)pool_data;
         return kmalloc(size, gfp_mask);
 }
 EXPORT_SYMBOL(mempool_kmalloc);
 
 void *mempool_kzalloc(gfp_t gfp_mask, void *pool_data)
 {
         size_t size = (size_t) pool_data;
         return kzalloc(size, gfp_mask);
 }
 EXPORT_SYMBOL(mempool_kzalloc);
 
 void mempool_kfree(void *element, void *pool_data)
 {
         kfree(element);
 }
 EXPORT_SYMBOL(mempool_kfree);
 
 /*
  * A simple mempool-backed page allocator that allocates pages
  * of the order specified by pool_data.
  */
 void *mempool_alloc_pages(gfp_t gfp_mask, void *pool_data)
 {
         int order = (int)(long)pool_data;
         return alloc_pages(gfp_mask, order);
 }
 EXPORT_SYMBOL(mempool_alloc_pages);
 
 void mempool_free_pages(void *element, void *pool_data)
 {
         int order = (int)(long)pool_data;
         __free_pages(element, order);
 }
 EXPORT_SYMBOL(mempool_free_pages);