/* * 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) { mempool_t *pool; pool = kmalloc(sizeof(*pool), GFP_KERNEL); if (!pool) return NULL; memset(pool, 0, sizeof(*pool)); pool->elements = kmalloc(min_nr * sizeof(void *), GFP_KERNEL); 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); /** * 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, unsigned int __nocast 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, unsigned int __nocast gfp_mask) { void *element; unsigned long flags; DEFINE_WAIT(wait); int 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; 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(unsigned int __nocast 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);