[mirror_ubuntu-zesty-kernel.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];
}

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

	/* We must not sleep in the GFP_ATOMIC case */
	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 */
	gfp_temp = gfp_mask;
	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
	30	static 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
72fd4a35	49	* memory pool. The pool can be used from the mempool_alloc() and mempool_free()
1da177e4	50	* functions. This function might sleep. Both the alloc_fn() and the free_fn()
72fd4a35	51	* functions might sleep - as long as the mempool_alloc() function is not called
1da177e4 LT	52	* from IRQ contexts.
1da177e4 LT	53	*/
1946089a	54	mempool_t mempool_create(int min_nr, mempool_alloc_t alloc_fn,
1da177e4 LT	55	mempool_free_t free_fn, void pool_data)
1da177e4 LT	56	{
1946089a CL	57	return mempool_create_node(min_nr,alloc_fn,free_fn, pool_data,-1);
	58	}
	59	EXPORT_SYMBOL(mempool_create);
1da177e4	60
1946089a CL	61	mempool_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;
94f6030c	65	pool = kmalloc_node(sizeof(*pool), GFP_KERNEL \| __GFP_ZERO, node_id);
1da177e4 LT	66	if (!pool)
1da177e4 LT	67	return NULL;
1946089a CL	68	pool->elements = kmalloc_node(min_nr * sizeof(void *),
1946089a CL	69	GFP_KERNEL, node_id);
1da177e4 LT	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	}
1946089a	96	EXPORT_SYMBOL(mempool_create_node);
1da177e4 LT	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	*/
dd0fc66f	114	int mempool_resize(mempool_t *pool, int new_min_nr, gfp_t gfp_mask)
1da177e4 LT	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	}
	167	out_unlock:
	168	spin_unlock_irqrestore(&pool->lock, flags);
	169	out:
	170	return 0;
	171	}
	172	EXPORT_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	*/
183	void mempool_destroy(mempool_t *pool)
184	{
f02e1faf ES	185	/* Check for outstanding elements */
f02e1faf ES	186	BUG_ON(pool->curr_nr != pool->min_nr);
1da177e4 LT	187	free_pool(pool);
	188	}
	189	EXPORT_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	*
72fd4a35	197	* this function only sleeps if the alloc_fn() function sleeps or
1da177e4 LT	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	*/
dd0fc66f	202	void * mempool_alloc(mempool_t *pool, gfp_t gfp_mask)
1da177e4 LT	203	{
	204	void *element;
	205	unsigned long flags;
01890a4c	206	wait_queue_t wait;
6daa0e28	207	gfp_t gfp_temp;
20a77776 NP	208
20a77776 NP	209	might_sleep_if(gfp_mask & __GFP_WAIT);
b84a35be NP	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 */
1da177e4	214
20a77776 NP	215	gfp_temp = gfp_mask & ~(__GFP_WAIT\|__GFP_IO);
20a77776 NP	216
1da177e4	217	repeat_alloc:
20a77776 NP	218
20a77776 NP	219	element = pool->alloc(gfp_temp, pool->pool_data);
1da177e4 LT	220	if (likely(element != NULL))
	221	return element;
	222
1da177e4 LT	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);
5b990546 TH	227	/* paired with rmb in mempool_free(), read comment there */
5b990546 TH	228	smp_wmb();
1da177e4 LT	229	return element;
1da177e4 LT	230	}
1da177e4 LT	231
1da177e4 LT	232	/* We must not sleep in the GFP_ATOMIC case */
5b990546 TH	233	if (!(gfp_mask & __GFP_WAIT)) {
5b990546 TH	234	spin_unlock_irqrestore(&pool->lock, flags);
1da177e4	235	return NULL;
5b990546	236	}
1da177e4	237
5b990546	238	/* Let's wait for someone else to return an element to @pool */
20a77776	239	gfp_temp = gfp_mask;
01890a4c	240	init_wait(&wait);
1da177e4	241	prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE);
1da177e4	242
5b990546 TH	243	spin_unlock_irqrestore(&pool->lock, flags);
	244
	245	/*
	246	* FIXME: this should be io_schedule(). The timeout is there as a
	247	* workaround for some DM problems in 2.6.18.
	248	*/
	249	io_schedule_timeout(5*HZ);
	250
	251	finish_wait(&pool->wait, &wait);
1da177e4 LT	252	goto repeat_alloc;
	253	}
	254	EXPORT_SYMBOL(mempool_alloc);
	255
	256	/**
	257	* mempool_free - return an element to the pool.
	258	* @element: pool element pointer.
	259	* @pool: pointer to the memory pool which was allocated via
	260	* mempool_create().
	261	*
	262	* this function only sleeps if the free_fn() function sleeps.
	263	*/
	264	void mempool_free(void element, mempool_t pool)
	265	{
	266	unsigned long flags;
	267
c80e7a82 RR	268	if (unlikely(element == NULL))
	269	return;
	270
5b990546 TH	271	/*
	272	* Paired with the wmb in mempool_alloc(). The preceding read is
	273	* for @element and the following @pool->curr_nr. This ensures
	274	* that the visible value of @pool->curr_nr is from after the
	275	* allocation of @element. This is necessary for fringe cases
	276	* where @element was passed to this task without going through
	277	* barriers.
	278	*
	279	* For example, assume @p is %NULL at the beginning and one task
	280	* performs "p = mempool_alloc(...);" while another task is doing
	281	* "while (!p) cpu_relax(); mempool_free(p, ...);". This function
	282	* may end up using curr_nr value which is from before allocation
	283	* of @p without the following rmb.
	284	*/
	285	smp_rmb();
	286
	287	/*
	288	* For correctness, we need a test which is guaranteed to trigger
	289	* if curr_nr + #allocated == min_nr. Testing curr_nr < min_nr
	290	* without locking achieves that and refilling as soon as possible
	291	* is desirable.
	292	*
	293	* Because curr_nr visible here is always a value after the
	294	* allocation of @element, any task which decremented curr_nr below
	295	* min_nr is guaranteed to see curr_nr < min_nr unless curr_nr gets
	296	* incremented to min_nr afterwards. If curr_nr gets incremented
	297	* to min_nr after the allocation of @element, the elements
	298	* allocated after that are subject to the same guarantee.
	299	*
	300	* Waiters happen iff curr_nr is 0 and the above guarantee also
	301	* ensures that there will be frees which return elements to the
	302	* pool waking up the waiters.
	303	*/
1da177e4 LT	304	if (pool->curr_nr < pool->min_nr) {
	305	spin_lock_irqsave(&pool->lock, flags);
	306	if (pool->curr_nr < pool->min_nr) {
	307	add_element(pool, element);
	308	spin_unlock_irqrestore(&pool->lock, flags);
	309	wake_up(&pool->wait);
	310	return;
	311	}
	312	spin_unlock_irqrestore(&pool->lock, flags);
	313	}
	314	pool->free(element, pool->pool_data);
	315	}
	316	EXPORT_SYMBOL(mempool_free);
	317
	318	/*
	319	* A commonly used alloc and free fn.
	320	*/
dd0fc66f	321	void mempool_alloc_slab(gfp_t gfp_mask, void pool_data)
1da177e4	322	{
fcc234f8	323	struct kmem_cache *mem = pool_data;
1da177e4 LT	324	return kmem_cache_alloc(mem, gfp_mask);
	325	}
	326	EXPORT_SYMBOL(mempool_alloc_slab);
	327
	328	void mempool_free_slab(void element, void pool_data)
	329	{
fcc234f8	330	struct kmem_cache *mem = pool_data;
1da177e4 LT	331	kmem_cache_free(mem, element);
	332	}
	333	EXPORT_SYMBOL(mempool_free_slab);
6e0678f3	334
53184082 MD	335	/*
53184082 MD	336	* A commonly used alloc and free fn that kmalloc/kfrees the amount of memory
183ff22b	337	* specified by pool_data
53184082 MD	338	*/
	339	void mempool_kmalloc(gfp_t gfp_mask, void pool_data)
	340	{
5e2f89b5	341	size_t size = (size_t)pool_data;
53184082 MD	342	return kmalloc(size, gfp_mask);
	343	}
	344	EXPORT_SYMBOL(mempool_kmalloc);
	345
	346	void mempool_kfree(void element, void pool_data)
	347	{
	348	kfree(element);
	349	}
	350	EXPORT_SYMBOL(mempool_kfree);
	351
6e0678f3 MD	352	/*
	353	* A simple mempool-backed page allocator that allocates pages
	354	* of the order specified by pool_data.
	355	*/
	356	void mempool_alloc_pages(gfp_t gfp_mask, void pool_data)
	357	{
	358	int order = (int)(long)pool_data;
	359	return alloc_pages(gfp_mask, order);
	360	}
	361	EXPORT_SYMBOL(mempool_alloc_pages);
	362
	363	void mempool_free_pages(void element, void pool_data)
	364	{
	365	int order = (int)(long)pool_data;
	366	__free_pages(element, order);
	367	}
	368	EXPORT_SYMBOL(mempool_free_pages);