[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/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)
{
	if (pool->curr_nr != pool->min_nr)
		BUG();		/* There were outstanding elements */
	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)
{
	kmem_cache_t *mem = (kmem_cache_t *) pool_data;
	return kmem_cache_alloc(mem, gfp_mask);
}
EXPORT_SYMBOL(mempool_alloc_slab);

void mempool_free_slab(void *element, void *pool_data)
{
	kmem_cache_t *mem = (kmem_cache_t *) pool_data;
	kmem_cache_free(mem, element);
}
EXPORT_SYMBOL(mempool_free_slab);
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>
	13	#include <linux/module.h>
	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
	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	*/
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;
	65	pool = kmalloc_node(sizeof(*pool), GFP_KERNEL, node_id);
1da177e4 LT	66	if (!pool)
	67	return NULL;
	68	memset(pool, 0, sizeof(*pool));
1946089a CL	69	pool->elements = kmalloc_node(min_nr * sizeof(void *),
1946089a CL	70	GFP_KERNEL, node_id);
1da177e4 LT	71	if (!pool->elements) {
	72	kfree(pool);
	73	return NULL;
	74	}
	75	spin_lock_init(&pool->lock);
	76	pool->min_nr = min_nr;
	77	pool->pool_data = pool_data;
	78	init_waitqueue_head(&pool->wait);
	79	pool->alloc = alloc_fn;
	80	pool->free = free_fn;
	81
	82	/*
	83	* First pre-allocate the guaranteed number of buffers.
	84	*/
	85	while (pool->curr_nr < pool->min_nr) {
	86	void *element;
	87
	88	element = pool->alloc(GFP_KERNEL, pool->pool_data);
	89	if (unlikely(!element)) {
	90	free_pool(pool);
	91	return NULL;
	92	}
	93	add_element(pool, element);
	94	}
	95	return pool;
	96	}
1946089a	97	EXPORT_SYMBOL(mempool_create_node);
1da177e4 LT	98
	99	/**
	100	* mempool_resize - resize an existing memory pool
	101	* @pool: pointer to the memory pool which was allocated via
	102	* mempool_create().
	103	* @new_min_nr: the new minimum number of elements guaranteed to be
	104	* allocated for this pool.
	105	* @gfp_mask: the usual allocation bitmask.
	106	*
	107	* This function shrinks/grows the pool. In the case of growing,
	108	* it cannot be guaranteed that the pool will be grown to the new
	109	* size immediately, but new mempool_free() calls will refill it.
	110	*
	111	* Note, the caller must guarantee that no mempool_destroy is called
	112	* while this function is running. mempool_alloc() & mempool_free()
	113	* might be called (eg. from IRQ contexts) while this function executes.
	114	*/
dd0fc66f	115	int mempool_resize(mempool_t *pool, int new_min_nr, gfp_t gfp_mask)
1da177e4 LT	116	{
	117	void *element;
	118	void **new_elements;
	119	unsigned long flags;
	120
	121	BUG_ON(new_min_nr <= 0);
	122
	123	spin_lock_irqsave(&pool->lock, flags);
	124	if (new_min_nr <= pool->min_nr) {
	125	while (new_min_nr < pool->curr_nr) {
	126	element = remove_element(pool);
	127	spin_unlock_irqrestore(&pool->lock, flags);
	128	pool->free(element, pool->pool_data);
	129	spin_lock_irqsave(&pool->lock, flags);
	130	}
	131	pool->min_nr = new_min_nr;
	132	goto out_unlock;
	133	}
	134	spin_unlock_irqrestore(&pool->lock, flags);
	135
	136	/* Grow the pool */
	137	new_elements = kmalloc(new_min_nr * sizeof(*new_elements), gfp_mask);
	138	if (!new_elements)
	139	return -ENOMEM;
	140
	141	spin_lock_irqsave(&pool->lock, flags);
	142	if (unlikely(new_min_nr <= pool->min_nr)) {
	143	/* Raced, other resize will do our work */
	144	spin_unlock_irqrestore(&pool->lock, flags);
	145	kfree(new_elements);
	146	goto out;
	147	}
	148	memcpy(new_elements, pool->elements,
	149	pool->curr_nr * sizeof(*new_elements));
	150	kfree(pool->elements);
	151	pool->elements = new_elements;
	152	pool->min_nr = new_min_nr;
	153
	154	while (pool->curr_nr < pool->min_nr) {
	155	spin_unlock_irqrestore(&pool->lock, flags);
	156	element = pool->alloc(gfp_mask, pool->pool_data);
	157	if (!element)
	158	goto out;
	159	spin_lock_irqsave(&pool->lock, flags);
	160	if (pool->curr_nr < pool->min_nr) {
	161	add_element(pool, element);
	162	} else {
	163	spin_unlock_irqrestore(&pool->lock, flags);
	164	pool->free(element, pool->pool_data); /* Raced */
	165	goto out;
	166	}
	167	}
	168	out_unlock:
	169	spin_unlock_irqrestore(&pool->lock, flags);
	170	out:
	171	return 0;
	172	}
	173	EXPORT_SYMBOL(mempool_resize);
	174
	175	/**
	176	* mempool_destroy - deallocate a memory pool
	177	* @pool: pointer to the memory pool which was allocated via
	178	* mempool_create().
	179	*
180	* this function only sleeps if the free_fn() function sleeps. The caller
181	* has to guarantee that all elements have been returned to the pool (ie:
182	* freed) prior to calling mempool_destroy().
183	*/
184	void mempool_destroy(mempool_t *pool)
185	{
186	if (pool->curr_nr != pool->min_nr)
187	BUG(); /* There were outstanding elements */
188	free_pool(pool);
189	}
190	EXPORT_SYMBOL(mempool_destroy);
191
192	/**
193	* mempool_alloc - allocate an element from a specific memory pool
194	* @pool: pointer to the memory pool which was allocated via
195	* mempool_create().
196	* @gfp_mask: the usual allocation bitmask.
197	*
198	* this function only sleeps if the alloc_fn function sleeps or
199	* returns NULL. Note that due to preallocation, this function
200	* never fails when called from process contexts. (it might
201	* fail if called from an IRQ context.)
202	*/
dd0fc66f	203	void * mempool_alloc(mempool_t *pool, gfp_t gfp_mask)
1da177e4 LT	204	{
	205	void *element;
	206	unsigned long flags;
01890a4c	207	wait_queue_t wait;
6daa0e28	208	gfp_t gfp_temp;
20a77776 NP	209
20a77776 NP	210	might_sleep_if(gfp_mask & __GFP_WAIT);
b84a35be NP	211
	212	gfp_mask \|= __GFP_NOMEMALLOC; /* don't allocate emergency reserves */
	213	gfp_mask \|= __GFP_NORETRY; /* don't loop in __alloc_pages */
	214	gfp_mask \|= __GFP_NOWARN; /* failures are OK */
1da177e4	215
20a77776 NP	216	gfp_temp = gfp_mask & ~(__GFP_WAIT\|__GFP_IO);
20a77776 NP	217
1da177e4	218	repeat_alloc:
20a77776 NP	219
20a77776 NP	220	element = pool->alloc(gfp_temp, pool->pool_data);
1da177e4 LT	221	if (likely(element != NULL))
	222	return element;
	223
1da177e4 LT	224	spin_lock_irqsave(&pool->lock, flags);
	225	if (likely(pool->curr_nr)) {
	226	element = remove_element(pool);
	227	spin_unlock_irqrestore(&pool->lock, flags);
	228	return element;
	229	}
	230	spin_unlock_irqrestore(&pool->lock, flags);
	231
	232	/* We must not sleep in the GFP_ATOMIC case */
	233	if (!(gfp_mask & __GFP_WAIT))
	234	return NULL;
	235
20a77776 NP	236	/* Now start performing page reclaim */
20a77776 NP	237	gfp_temp = gfp_mask;
01890a4c	238	init_wait(&wait);
1da177e4	239	prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE);
d59dd462	240	smp_mb();
1da177e4 LT	241	if (!pool->curr_nr)
	242	io_schedule();
	243	finish_wait(&pool->wait, &wait);
	244
	245	goto repeat_alloc;
	246	}
	247	EXPORT_SYMBOL(mempool_alloc);
	248
	249	/**
	250	* mempool_free - return an element to the pool.
	251	* @element: pool element pointer.
	252	* @pool: pointer to the memory pool which was allocated via
	253	* mempool_create().
	254	*
	255	* this function only sleeps if the free_fn() function sleeps.
	256	*/
	257	void mempool_free(void element, mempool_t pool)
	258	{
	259	unsigned long flags;
	260
d59dd462	261	smp_mb();
1da177e4 LT	262	if (pool->curr_nr < pool->min_nr) {
	263	spin_lock_irqsave(&pool->lock, flags);
	264	if (pool->curr_nr < pool->min_nr) {
	265	add_element(pool, element);
	266	spin_unlock_irqrestore(&pool->lock, flags);
	267	wake_up(&pool->wait);
	268	return;
	269	}
	270	spin_unlock_irqrestore(&pool->lock, flags);
	271	}
	272	pool->free(element, pool->pool_data);
	273	}
	274	EXPORT_SYMBOL(mempool_free);
	275
	276	/*
	277	* A commonly used alloc and free fn.
	278	*/
dd0fc66f	279	void mempool_alloc_slab(gfp_t gfp_mask, void pool_data)
1da177e4 LT	280	{
	281	kmem_cache_t mem = (kmem_cache_t ) pool_data;
	282	return kmem_cache_alloc(mem, gfp_mask);
	283	}
	284	EXPORT_SYMBOL(mempool_alloc_slab);
	285
	286	void mempool_free_slab(void element, void pool_data)
	287	{
	288	kmem_cache_t mem = (kmem_cache_t ) pool_data;
	289	kmem_cache_free(mem, element);
	290	}
	291	EXPORT_SYMBOL(mempool_free_slab);