Mempool version by Christoph Hellwig that holds the free objects in an array rather than a list. This prevents the objects getting dirtied, eg, people maybe expecting them to come out of a slab with a particular state. --- diff/include/linux/mempool.h 2002-11-29 09:44:59.000000000 +0000 +++ source/include/linux/mempool.h 2002-11-29 09:45:30.000000000 +0000 @@ -13,24 +13,13 @@ typedef void * (mempool_alloc_t)(int gfp_mask, void *pool_data); typedef void (mempool_free_t)(void *element, void *pool_data); -struct mempool_s { - spinlock_t lock; - int min_nr, curr_nr; - struct list_head elements; - - void *pool_data; - mempool_alloc_t *alloc; - mempool_free_t *free; - wait_queue_head_t wait; -}; extern mempool_t * mempool_create(int min_nr, mempool_alloc_t *alloc_fn, mempool_free_t *free_fn, void *pool_data); -extern void mempool_resize(mempool_t *pool, int new_min_nr, int gfp_mask); +extern int mempool_resize(mempool_t *pool, int new_min_nr, int gfp_mask); extern void mempool_destroy(mempool_t *pool); extern void * mempool_alloc(mempool_t *pool, int gfp_mask); extern void mempool_free(void *element, mempool_t *pool); - /* * A mempool_alloc_t and mempool_free_t that get the memory from * a slab that is passed in through pool_data. @@ -38,4 +27,5 @@ void *mempool_alloc_slab(int gfp_mask, void *pool_data); void mempool_free_slab(void *element, void *pool_data); + #endif /* _LINUX_MEMPOOL_H */ --- diff/mm/mempool.c 2002-11-29 09:44:59.000000000 +0000 +++ source/mm/mempool.c 2002-11-29 09:45:30.000000000 +0000 @@ -12,7 +12,40 @@ #include #include #include -#include + +struct mempool_s { + spinlock_t lock; + int min_nr; /* nr of elements at *elements */ + int curr_nr; /* Current nr of elements at *elements */ + void **elements; + + void *pool_data; + mempool_alloc_t *alloc; + mempool_free_t *free; + wait_queue_head_t wait; +}; + +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 @@ -26,24 +59,25 @@ * 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. The element allocated by alloc_fn() must be able to - * hold a struct list_head. (8 bytes on x86.) + * 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; - int i; 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_LIST_HEAD(&pool->elements); init_waitqueue_head(&pool->wait); pool->alloc = alloc_fn; pool->free = free_fn; @@ -51,27 +85,15 @@ /* * First pre-allocate the guaranteed number of buffers. */ - for (i = 0; i < min_nr; i++) { + while (pool->curr_nr < pool->min_nr) { void *element; - struct list_head *tmp; - element = pool->alloc(GFP_KERNEL, pool->pool_data); + element = pool->alloc(GFP_KERNEL, pool->pool_data); if (unlikely(!element)) { - /* - * Not enough memory - free the allocated ones - * and return: - */ - list_for_each(tmp, &pool->elements) { - element = tmp; - pool->free(element, pool->pool_data); - } - kfree(pool); - + free_pool(pool); return NULL; } - tmp = element; - list_add(tmp, &pool->elements); - pool->curr_nr++; + add_element(pool, element); } return pool; } @@ -92,53 +114,54 @@ * while this function is running. mempool_alloc() & mempool_free() * might be called (eg. from IRQ contexts) while this function executes. */ -void mempool_resize(mempool_t *pool, int new_min_nr, int gfp_mask) +int mempool_resize(mempool_t *pool, int new_min_nr, int gfp_mask) { - int delta; void *element; + void **new_elements; unsigned long flags; - struct list_head *tmp; - if (new_min_nr <= 0) - BUG(); + BUG_ON(new_min_nr <= 0); spin_lock_irqsave(&pool->lock, flags); if (new_min_nr < pool->min_nr) { - pool->min_nr = new_min_nr; - /* - * Free possible excess elements. - */ - while (pool->curr_nr > pool->min_nr) { - tmp = pool->elements.next; - if (tmp == &pool->elements) - BUG(); - list_del(tmp); - element = tmp; - pool->curr_nr--; + while (pool->curr_nr > new_min_nr) { + element = remove_element(pool); spin_unlock_irqrestore(&pool->lock, flags); - pool->free(element, pool->pool_data); - spin_lock_irqsave(&pool->lock, flags); } - spin_unlock_irqrestore(&pool->lock, flags); - return; + pool->min_nr = new_min_nr; + goto out_unlock; } - delta = new_min_nr - pool->min_nr; - pool->min_nr = new_min_nr; spin_unlock_irqrestore(&pool->lock, flags); - /* - * We refill the pool up to the new treshold - but we dont - * (cannot) guarantee that the refill succeeds. - */ - while (delta) { + /* 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); + 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) - break; - mempool_free(element, pool); - delta--; + goto out; + spin_lock_irqsave(&pool->lock, flags); + if (pool->curr_nr < pool->min_nr) + add_element(pool, element); + else + kfree(element); /* Raced */ } +out_unlock: + spin_unlock_irqrestore(&pool->lock, flags); +out: + return 0; } /** @@ -147,27 +170,14 @@ * mempool_create(). * * this function only sleeps if the free_fn() function sleeps. The caller - * has to guarantee that no mempool_alloc() nor mempool_free() happens in - * this pool when calling this function. + * 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) { - void *element; - struct list_head *head, *tmp; - - if (!pool) - return; - - head = &pool->elements; - for (tmp = head->next; tmp != head; ) { - element = tmp; - tmp = tmp->next; - pool->free(element, pool->pool_data); - pool->curr_nr--; - } - if (pool->curr_nr) - BUG(); - kfree(pool); + if (pool->curr_nr != pool->min_nr) + BUG(); /* There were outstanding elements */ + free_pool(pool); } /** @@ -185,7 +195,6 @@ { void *element; unsigned long flags; - struct list_head *tmp; int curr_nr; DECLARE_WAITQUEUE(wait, current); int gfp_nowait = gfp_mask & ~(__GFP_WAIT | __GFP_IO); @@ -212,10 +221,7 @@ spin_lock_irqsave(&pool->lock, flags); if (likely(pool->curr_nr)) { - tmp = pool->elements.next; - list_del(tmp); - element = tmp; - pool->curr_nr--; + element = remove_element(pool); spin_unlock_irqrestore(&pool->lock, flags); return element; } @@ -258,8 +264,7 @@ if (pool->curr_nr < pool->min_nr) { spin_lock_irqsave(&pool->lock, flags); if (pool->curr_nr < pool->min_nr) { - list_add(element, &pool->elements); - pool->curr_nr++; + add_element(pool, element); spin_unlock_irqrestore(&pool->lock, flags); wake_up(&pool->wait); return; @@ -292,4 +297,3 @@ EXPORT_SYMBOL(mempool_free); EXPORT_SYMBOL(mempool_alloc_slab); EXPORT_SYMBOL(mempool_free_slab); -