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/*

 *  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 | __GFP_ZERO, node_id);

        if (!pool)

                return NULL;

        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) {

                /*

                 * FIXME: this should be io_schedule().  The timeout is there

                 * as a workaround for some DM problems in 2.6.18.

                 */

                io_schedule_timeout(5*HZ);

        }

        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;

        if (unlikely(element == NULL))

                return;

        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

 * specified 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);