diff options
Diffstat (limited to 'mm/mempool.c')
-rw-r--r-- | mm/mempool.c | 333 |
1 files changed, 333 insertions, 0 deletions
diff --git a/mm/mempool.c b/mm/mempool.c new file mode 100644 index 00000000..1a3bc3d4 --- /dev/null +++ b/mm/mempool.c @@ -0,0 +1,333 @@ +/* + * 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 | __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); + 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) { + /* + * 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; + + 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) +{ + 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); |