[linux.git] / 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/export.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];
}

/**
 * mempool_destroy - deallocate a memory pool
 * @pool:      pointer to the memory pool which was allocated via
 *             mempool_create().
 *
 * Free all reserved elements in @pool and @pool itself.  This function
 * only sleeps if the free_fn() function sleeps.
 */
void mempool_destroy(mempool_t *pool)
{
	while (pool->curr_nr) {
		void *element = remove_element(pool);
		pool->free(element, pool->pool_data);
	}
	kfree(pool->elements);
	kfree(pool);
}
EXPORT_SYMBOL(mempool_destroy);

/**
 * 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)) {
			mempool_destroy(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_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);
		/* paired with rmb in mempool_free(), read comment there */
		smp_wmb();
		return element;
	}

	/*
	 * We use gfp mask w/o __GFP_WAIT or IO for the first round.  If
	 * alloc failed with that and @pool was empty, retry immediately.
	 */
	if (gfp_temp != gfp_mask) {
		spin_unlock_irqrestore(&pool->lock, flags);
		gfp_temp = gfp_mask;
		goto repeat_alloc;
	}

	/* We must not sleep if !__GFP_WAIT */
	if (!(gfp_mask & __GFP_WAIT)) {
		spin_unlock_irqrestore(&pool->lock, flags);
		return NULL;
	}

	/* Let's wait for someone else to return an element to @pool */
	init_wait(&wait);
	prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE);

	spin_unlock_irqrestore(&pool->lock, flags);

	/*
	 * 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;

	/*
	 * Paired with the wmb in mempool_alloc().  The preceding read is
	 * for @element and the following @pool->curr_nr.  This ensures
	 * that the visible value of @pool->curr_nr is from after the
	 * allocation of @element.  This is necessary for fringe cases
	 * where @element was passed to this task without going through
	 * barriers.
	 *
	 * For example, assume @p is %NULL at the beginning and one task
	 * performs "p = mempool_alloc(...);" while another task is doing
	 * "while (!p) cpu_relax(); mempool_free(p, ...);".  This function
	 * may end up using curr_nr value which is from before allocation
	 * of @p without the following rmb.
	 */
	smp_rmb();

	/*
	 * For correctness, we need a test which is guaranteed to trigger
	 * if curr_nr + #allocated == min_nr.  Testing curr_nr < min_nr
	 * without locking achieves that and refilling as soon as possible
	 * is desirable.
	 *
	 * Because curr_nr visible here is always a value after the
	 * allocation of @element, any task which decremented curr_nr below
	 * min_nr is guaranteed to see curr_nr < min_nr unless curr_nr gets
	 * incremented to min_nr afterwards.  If curr_nr gets incremented
	 * to min_nr after the allocation of @element, the elements
	 * allocated after that are subject to the same guarantee.
	 *
	 * Waiters happen iff curr_nr is 0 and the above guarantee also
	 * ensures that there will be frees which return elements to the
	 * pool waking up the waiters.
	 */
	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)pool_data;
	return kmalloc(size, gfp_mask);
}
EXPORT_SYMBOL(mempool_kmalloc);

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);
Commit	Line	Data
1da177e4 LT	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>
b95f1b31	13	#include <linux/export.h>
1da177e4 LT	14	#include <linux/mempool.h>
	15	#include <linux/blkdev.h>
	16	#include <linux/writeback.h>
	17
	18	static 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
	24	static void remove_element(mempool_t pool)
	25	{
	26	BUG_ON(pool->curr_nr <= 0);
	27	return pool->elements[--pool->curr_nr];
	28	}
	29
0565d317 TH	30	/**
	31	* mempool_destroy - deallocate a memory pool
	32	* @pool: pointer to the memory pool which was allocated via
	33	* mempool_create().
	34	*
	35	* Free all reserved elements in @pool and @pool itself. This function
	36	* only sleeps if the free_fn() function sleeps.
	37	*/
	38	void mempool_destroy(mempool_t *pool)
1da177e4 LT	39	{
	40	while (pool->curr_nr) {
	41	void *element = remove_element(pool);
	42	pool->free(element, pool->pool_data);
	43	}
	44	kfree(pool->elements);
	45	kfree(pool);
	46	}
0565d317	47	EXPORT_SYMBOL(mempool_destroy);
1da177e4 LT	48
	49	/**
	50	* mempool_create - create a memory pool
	51	* @min_nr: the minimum number of elements guaranteed to be
	52	* allocated for this pool.
	53	* @alloc_fn: user-defined element-allocation function.
	54	* @free_fn: user-defined element-freeing function.
	55	* @pool_data: optional private data available to the user-defined functions.
	56	*
	57	* this function creates and allocates a guaranteed size, preallocated
72fd4a35	58	* memory pool. The pool can be used from the mempool_alloc() and mempool_free()
1da177e4	59	* functions. This function might sleep. Both the alloc_fn() and the free_fn()
72fd4a35	60	* functions might sleep - as long as the mempool_alloc() function is not called
1da177e4 LT	61	* from IRQ contexts.
1da177e4 LT	62	*/
1946089a	63	mempool_t mempool_create(int min_nr, mempool_alloc_t alloc_fn,
1da177e4 LT	64	mempool_free_t free_fn, void pool_data)
1da177e4 LT	65	{
1946089a CL	66	return mempool_create_node(min_nr,alloc_fn,free_fn, pool_data,-1);
	67	}
	68	EXPORT_SYMBOL(mempool_create);
1da177e4	69
1946089a CL	70	mempool_t mempool_create_node(int min_nr, mempool_alloc_t alloc_fn,
	71	mempool_free_t free_fn, void pool_data, int node_id)
	72	{
	73	mempool_t *pool;
94f6030c	74	pool = kmalloc_node(sizeof(*pool), GFP_KERNEL \| __GFP_ZERO, node_id);
1da177e4 LT	75	if (!pool)
1da177e4 LT	76	return NULL;
1946089a CL	77	pool->elements = kmalloc_node(min_nr * sizeof(void *),
1946089a CL	78	GFP_KERNEL, node_id);
1da177e4 LT	79	if (!pool->elements) {
	80	kfree(pool);
	81	return NULL;
	82	}
	83	spin_lock_init(&pool->lock);
	84	pool->min_nr = min_nr;
	85	pool->pool_data = pool_data;
	86	init_waitqueue_head(&pool->wait);
	87	pool->alloc = alloc_fn;
	88	pool->free = free_fn;
	89
	90	/*
	91	* First pre-allocate the guaranteed number of buffers.
	92	*/
	93	while (pool->curr_nr < pool->min_nr) {
	94	void *element;
	95
	96	element = pool->alloc(GFP_KERNEL, pool->pool_data);
	97	if (unlikely(!element)) {
0565d317	98	mempool_destroy(pool);
1da177e4 LT	99	return NULL;
	100	}
	101	add_element(pool, element);
	102	}
	103	return pool;
	104	}
1946089a	105	EXPORT_SYMBOL(mempool_create_node);
1da177e4 LT	106
	107	/**
	108	* mempool_resize - resize an existing memory pool
	109	* @pool: pointer to the memory pool which was allocated via
	110	* mempool_create().
	111	* @new_min_nr: the new minimum number of elements guaranteed to be
	112	* allocated for this pool.
	113	* @gfp_mask: the usual allocation bitmask.
	114	*
	115	* This function shrinks/grows the pool. In the case of growing,
	116	* it cannot be guaranteed that the pool will be grown to the new
	117	* size immediately, but new mempool_free() calls will refill it.
	118	*
	119	* Note, the caller must guarantee that no mempool_destroy is called
	120	* while this function is running. mempool_alloc() & mempool_free()
	121	* might be called (eg. from IRQ contexts) while this function executes.
	122	*/
dd0fc66f	123	int mempool_resize(mempool_t *pool, int new_min_nr, gfp_t gfp_mask)
1da177e4 LT	124	{
	125	void *element;
	126	void **new_elements;
	127	unsigned long flags;
	128
	129	BUG_ON(new_min_nr <= 0);
	130
	131	spin_lock_irqsave(&pool->lock, flags);
	132	if (new_min_nr <= pool->min_nr) {
	133	while (new_min_nr < pool->curr_nr) {
	134	element = remove_element(pool);
	135	spin_unlock_irqrestore(&pool->lock, flags);
	136	pool->free(element, pool->pool_data);
	137	spin_lock_irqsave(&pool->lock, flags);
	138	}
	139	pool->min_nr = new_min_nr;
	140	goto out_unlock;
	141	}
	142	spin_unlock_irqrestore(&pool->lock, flags);
	143
	144	/* Grow the pool */
	145	new_elements = kmalloc(new_min_nr * sizeof(*new_elements), gfp_mask);
	146	if (!new_elements)
	147	return -ENOMEM;
	148
	149	spin_lock_irqsave(&pool->lock, flags);
	150	if (unlikely(new_min_nr <= pool->min_nr)) {
	151	/* Raced, other resize will do our work */
	152	spin_unlock_irqrestore(&pool->lock, flags);
	153	kfree(new_elements);
	154	goto out;
	155	}
	156	memcpy(new_elements, pool->elements,
	157	pool->curr_nr * sizeof(*new_elements));
	158	kfree(pool->elements);
	159	pool->elements = new_elements;
	160	pool->min_nr = new_min_nr;
	161
	162	while (pool->curr_nr < pool->min_nr) {
	163	spin_unlock_irqrestore(&pool->lock, flags);
	164	element = pool->alloc(gfp_mask, pool->pool_data);
	165	if (!element)
	166	goto out;
	167	spin_lock_irqsave(&pool->lock, flags);
	168	if (pool->curr_nr < pool->min_nr) {
	169	add_element(pool, element);
	170	} else {
	171	spin_unlock_irqrestore(&pool->lock, flags);
	172	pool->free(element, pool->pool_data); /* Raced */
	173	goto out;
	174	}
	175	}
	176	out_unlock:
	177	spin_unlock_irqrestore(&pool->lock, flags);
	178	out:
	179	return 0;
	180	}
	181	EXPORT_SYMBOL(mempool_resize);
	182
1da177e4 LT	183	/**
	184	* mempool_alloc - allocate an element from a specific memory pool
	185	* @pool: pointer to the memory pool which was allocated via
	186	* mempool_create().
	187	* @gfp_mask: the usual allocation bitmask.
	188	*
72fd4a35	189	* this function only sleeps if the alloc_fn() function sleeps or
1da177e4 LT	190	* returns NULL. Note that due to preallocation, this function
	191	* never fails when called from process contexts. (it might
	192	* fail if called from an IRQ context.)
	193	*/
dd0fc66f	194	void * mempool_alloc(mempool_t *pool, gfp_t gfp_mask)
1da177e4 LT	195	{
	196	void *element;
	197	unsigned long flags;
01890a4c	198	wait_queue_t wait;
6daa0e28	199	gfp_t gfp_temp;
20a77776 NP	200
20a77776 NP	201	might_sleep_if(gfp_mask & __GFP_WAIT);
b84a35be NP	202
	203	gfp_mask \|= __GFP_NOMEMALLOC; /* don't allocate emergency reserves */
	204	gfp_mask \|= __GFP_NORETRY; /* don't loop in __alloc_pages */
	205	gfp_mask \|= __GFP_NOWARN; /* failures are OK */
1da177e4	206
20a77776 NP	207	gfp_temp = gfp_mask & ~(__GFP_WAIT\|__GFP_IO);
20a77776 NP	208
1da177e4	209	repeat_alloc:
20a77776 NP	210
20a77776 NP	211	element = pool->alloc(gfp_temp, pool->pool_data);
1da177e4 LT	212	if (likely(element != NULL))
	213	return element;
	214
1da177e4 LT	215	spin_lock_irqsave(&pool->lock, flags);
	216	if (likely(pool->curr_nr)) {
	217	element = remove_element(pool);
	218	spin_unlock_irqrestore(&pool->lock, flags);
5b990546 TH	219	/* paired with rmb in mempool_free(), read comment there */
5b990546 TH	220	smp_wmb();
1da177e4 LT	221	return element;
1da177e4 LT	222	}
1da177e4	223
1ebb7044 TH	224	/*
	225	* We use gfp mask w/o __GFP_WAIT or IO for the first round. If
	226	* alloc failed with that and @pool was empty, retry immediately.
	227	*/
	228	if (gfp_temp != gfp_mask) {
	229	spin_unlock_irqrestore(&pool->lock, flags);
	230	gfp_temp = gfp_mask;
	231	goto repeat_alloc;
	232	}
	233
	234	/* We must not sleep if !__GFP_WAIT */
5b990546 TH	235	if (!(gfp_mask & __GFP_WAIT)) {
5b990546 TH	236	spin_unlock_irqrestore(&pool->lock, flags);
1da177e4	237	return NULL;
5b990546	238	}
1da177e4	239
5b990546	240	/* Let's wait for someone else to return an element to @pool */
01890a4c	241	init_wait(&wait);
1da177e4	242	prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE);
1da177e4	243
5b990546 TH	244	spin_unlock_irqrestore(&pool->lock, flags);
	245
	246	/*
	247	* FIXME: this should be io_schedule(). The timeout is there as a
	248	* workaround for some DM problems in 2.6.18.
	249	*/
	250	io_schedule_timeout(5*HZ);
	251
	252	finish_wait(&pool->wait, &wait);
1da177e4 LT	253	goto repeat_alloc;
	254	}
	255	EXPORT_SYMBOL(mempool_alloc);
	256
	257	/**
	258	* mempool_free - return an element to the pool.
	259	* @element: pool element pointer.
	260	* @pool: pointer to the memory pool which was allocated via
	261	* mempool_create().
	262	*
	263	* this function only sleeps if the free_fn() function sleeps.
	264	*/
	265	void mempool_free(void element, mempool_t pool)
	266	{
	267	unsigned long flags;
	268
c80e7a82 RR	269	if (unlikely(element == NULL))
	270	return;
	271
5b990546 TH	272	/*
	273	* Paired with the wmb in mempool_alloc(). The preceding read is
	274	* for @element and the following @pool->curr_nr. This ensures
	275	* that the visible value of @pool->curr_nr is from after the
	276	* allocation of @element. This is necessary for fringe cases
	277	* where @element was passed to this task without going through
	278	* barriers.
	279	*
	280	* For example, assume @p is %NULL at the beginning and one task
	281	* performs "p = mempool_alloc(...);" while another task is doing
	282	* "while (!p) cpu_relax(); mempool_free(p, ...);". This function
	283	* may end up using curr_nr value which is from before allocation
	284	* of @p without the following rmb.
	285	*/
	286	smp_rmb();
	287
	288	/*
	289	* For correctness, we need a test which is guaranteed to trigger
	290	* if curr_nr + #allocated == min_nr. Testing curr_nr < min_nr
	291	* without locking achieves that and refilling as soon as possible
	292	* is desirable.
	293	*
	294	* Because curr_nr visible here is always a value after the
	295	* allocation of @element, any task which decremented curr_nr below
	296	* min_nr is guaranteed to see curr_nr < min_nr unless curr_nr gets
	297	* incremented to min_nr afterwards. If curr_nr gets incremented
	298	* to min_nr after the allocation of @element, the elements
	299	* allocated after that are subject to the same guarantee.
	300	*
	301	* Waiters happen iff curr_nr is 0 and the above guarantee also
	302	* ensures that there will be frees which return elements to the
	303	* pool waking up the waiters.
	304	*/
1da177e4 LT	305	if (pool->curr_nr < pool->min_nr) {
	306	spin_lock_irqsave(&pool->lock, flags);
	307	if (pool->curr_nr < pool->min_nr) {
	308	add_element(pool, element);
	309	spin_unlock_irqrestore(&pool->lock, flags);
	310	wake_up(&pool->wait);
	311	return;
	312	}
	313	spin_unlock_irqrestore(&pool->lock, flags);
	314	}
	315	pool->free(element, pool->pool_data);
	316	}
	317	EXPORT_SYMBOL(mempool_free);
	318
	319	/*
	320	* A commonly used alloc and free fn.
	321	*/
dd0fc66f	322	void mempool_alloc_slab(gfp_t gfp_mask, void pool_data)
1da177e4	323	{
fcc234f8	324	struct kmem_cache *mem = pool_data;
1da177e4 LT	325	return kmem_cache_alloc(mem, gfp_mask);
	326	}
	327	EXPORT_SYMBOL(mempool_alloc_slab);
	328
	329	void mempool_free_slab(void element, void pool_data)
	330	{
fcc234f8	331	struct kmem_cache *mem = pool_data;
1da177e4 LT	332	kmem_cache_free(mem, element);
	333	}
	334	EXPORT_SYMBOL(mempool_free_slab);
6e0678f3	335
53184082 MD	336	/*
53184082 MD	337	* A commonly used alloc and free fn that kmalloc/kfrees the amount of memory
183ff22b	338	* specified by pool_data
53184082 MD	339	*/
	340	void mempool_kmalloc(gfp_t gfp_mask, void pool_data)
	341	{
5e2f89b5	342	size_t size = (size_t)pool_data;
53184082 MD	343	return kmalloc(size, gfp_mask);
	344	}
	345	EXPORT_SYMBOL(mempool_kmalloc);
	346
	347	void mempool_kfree(void element, void pool_data)
	348	{
	349	kfree(element);
	350	}
	351	EXPORT_SYMBOL(mempool_kfree);
	352
6e0678f3 MD	353	/*
	354	* A simple mempool-backed page allocator that allocates pages
	355	* of the order specified by pool_data.
	356	*/
	357	void mempool_alloc_pages(gfp_t gfp_mask, void pool_data)
	358	{
	359	int order = (int)(long)pool_data;
	360	return alloc_pages(gfp_mask, order);
	361	}
	362	EXPORT_SYMBOL(mempool_alloc_pages);
	363
	364	void mempool_free_pages(void element, void pool_data)
	365	{
	366	int order = (int)(long)pool_data;
	367	__free_pages(element, order);
	368	}
	369	EXPORT_SYMBOL(mempool_free_pages);