/* *  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,				   GFP_KERNEL, NUMA_NO_NODE);}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,			       gfp_t gfp_mask, int node_id){	mempool_t *pool;	pool = kzalloc_node(sizeof(*pool), gfp_mask, node_id);	if (!pool)		return NULL;	pool->elements = kmalloc_node(min_nr * sizeof(void *),				      gfp_mask, 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_mask, 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);