4 * memory buffer pool support. Such pools are mostly used
5 * for guaranteed, deadlock-free memory allocations during
8 * started by Ingo Molnar, Copyright (C) 2001
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>
18 static void add_element(mempool_t *pool, void *element)
20 BUG_ON(pool->curr_nr >= pool->min_nr);
21 pool->elements[pool->curr_nr++] = element;
24 static void *remove_element(mempool_t *pool)
26 BUG_ON(pool->curr_nr <= 0);
27 return pool->elements[--pool->curr_nr];
30 static void free_pool(mempool_t *pool)
32 while (pool->curr_nr) {
33 void *element = remove_element(pool);
34 pool->free(element, pool->pool_data);
36 kfree(pool->elements);
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.
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
54 mempool_t * mempool_create(int min_nr, mempool_alloc_t *alloc_fn,
55 mempool_free_t *free_fn, void *pool_data)
59 pool = kmalloc(sizeof(*pool), GFP_KERNEL);
62 memset(pool, 0, sizeof(*pool));
63 pool->elements = kmalloc(min_nr * sizeof(void *), GFP_KERNEL);
64 if (!pool->elements) {
68 spin_lock_init(&pool->lock);
69 pool->min_nr = min_nr;
70 pool->pool_data = pool_data;
71 init_waitqueue_head(&pool->wait);
72 pool->alloc = alloc_fn;
76 * First pre-allocate the guaranteed number of buffers.
78 while (pool->curr_nr < pool->min_nr) {
81 element = pool->alloc(GFP_KERNEL, pool->pool_data);
82 if (unlikely(!element)) {
86 add_element(pool, element);
90 EXPORT_SYMBOL(mempool_create);
93 * mempool_resize is disabled for now, because it has no callers. Feel free
94 * to turn it back on if needed.
98 * mempool_resize - resize an existing memory pool
99 * @pool: pointer to the memory pool which was allocated via
101 * @new_min_nr: the new minimum number of elements guaranteed to be
102 * allocated for this pool.
103 * @gfp_mask: the usual allocation bitmask.
105 * This function shrinks/grows the pool. In the case of growing,
106 * it cannot be guaranteed that the pool will be grown to the new
107 * size immediately, but new mempool_free() calls will refill it.
109 * Note, the caller must guarantee that no mempool_destroy is called
110 * while this function is running. mempool_alloc() & mempool_free()
111 * might be called (eg. from IRQ contexts) while this function executes.
113 int mempool_resize(mempool_t *pool, int new_min_nr, int gfp_mask)
119 BUG_ON(new_min_nr <= 0);
121 spin_lock_irqsave(&pool->lock, flags);
122 if (new_min_nr < pool->min_nr) {
123 while (pool->curr_nr > new_min_nr) {
124 element = remove_element(pool);
125 spin_unlock_irqrestore(&pool->lock, flags);
126 pool->free(element, pool->pool_data);
127 spin_lock_irqsave(&pool->lock, flags);
129 pool->min_nr = new_min_nr;
132 spin_unlock_irqrestore(&pool->lock, flags);
135 new_elements = kmalloc(new_min_nr * sizeof(*new_elements), gfp_mask);
139 spin_lock_irqsave(&pool->lock, flags);
140 memcpy(new_elements, pool->elements,
141 pool->curr_nr * sizeof(*new_elements));
142 kfree(pool->elements);
143 pool->elements = new_elements;
144 pool->min_nr = new_min_nr;
146 while (pool->curr_nr < pool->min_nr) {
147 spin_unlock_irqrestore(&pool->lock, flags);
148 element = pool->alloc(gfp_mask, pool->pool_data);
151 spin_lock_irqsave(&pool->lock, flags);
152 if (pool->curr_nr < pool->min_nr) {
153 add_element(pool, element);
155 spin_unlock_irqrestore(&pool->lock, flags);
156 pool->free(element, pool->pool_data); /* Raced */
157 spin_lock_irqsave(&pool->lock, flags);
161 spin_unlock_irqrestore(&pool->lock, flags);
165 EXPORT_SYMBOL(mempool_resize);
169 * mempool_destroy - deallocate a memory pool
170 * @pool: pointer to the memory pool which was allocated via
173 * this function only sleeps if the free_fn() function sleeps. The caller
174 * has to guarantee that all elements have been returned to the pool (ie:
175 * freed) prior to calling mempool_destroy().
177 void mempool_destroy(mempool_t *pool)
179 if (pool->curr_nr != pool->min_nr)
180 BUG(); /* There were outstanding elements */
183 EXPORT_SYMBOL(mempool_destroy);
186 * mempool_alloc - allocate an element from a specific memory pool
187 * @pool: pointer to the memory pool which was allocated via
189 * @gfp_mask: the usual allocation bitmask.
191 * this function only sleeps if the alloc_fn function sleeps or
192 * returns NULL. Note that due to preallocation, this function
193 * *never* fails when called from process contexts. (it might
194 * fail if called from an IRQ context.)
196 void * mempool_alloc(mempool_t *pool, int gfp_mask)
201 int gfp_nowait = gfp_mask & ~(__GFP_WAIT | __GFP_IO);
204 element = pool->alloc(gfp_nowait|__GFP_NOWARN, pool->pool_data);
205 if (likely(element != NULL))
209 * If the pool is less than 50% full and we can perform effective
210 * page reclaim then try harder to allocate an element.
213 if ((gfp_mask & __GFP_FS) && (gfp_mask != gfp_nowait) &&
214 (pool->curr_nr <= pool->min_nr/2)) {
215 element = pool->alloc(gfp_mask, pool->pool_data);
216 if (likely(element != NULL))
221 * Kick the VM at this point.
225 spin_lock_irqsave(&pool->lock, flags);
226 if (likely(pool->curr_nr)) {
227 element = remove_element(pool);
228 spin_unlock_irqrestore(&pool->lock, flags);
231 spin_unlock_irqrestore(&pool->lock, flags);
233 /* We must not sleep in the GFP_ATOMIC case */
234 if (!(gfp_mask & __GFP_WAIT))
237 prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE);
241 finish_wait(&pool->wait, &wait);
245 EXPORT_SYMBOL(mempool_alloc);
248 * mempool_free - return an element to the pool.
249 * @element: pool element pointer.
250 * @pool: pointer to the memory pool which was allocated via
253 * this function only sleeps if the free_fn() function sleeps.
255 void mempool_free(void *element, mempool_t *pool)
260 if (pool->curr_nr < pool->min_nr) {
261 spin_lock_irqsave(&pool->lock, flags);
262 if (pool->curr_nr < pool->min_nr) {
263 add_element(pool, element);
264 spin_unlock_irqrestore(&pool->lock, flags);
265 wake_up(&pool->wait);
268 spin_unlock_irqrestore(&pool->lock, flags);
270 pool->free(element, pool->pool_data);
272 EXPORT_SYMBOL(mempool_free);
275 * A commonly used alloc and free fn.
277 void *mempool_alloc_slab(int gfp_mask, void *pool_data)
279 kmem_cache_t *mem = (kmem_cache_t *) pool_data;
280 return kmem_cache_alloc(mem, gfp_mask);
282 EXPORT_SYMBOL(mempool_alloc_slab);
284 void mempool_free_slab(void *element, void *pool_data)
286 kmem_cache_t *mem = (kmem_cache_t *) pool_data;
287 kmem_cache_free(mem, element);
289 EXPORT_SYMBOL(mempool_free_slab);