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/export.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
];
31 * mempool_destroy - deallocate a memory pool
32 * @pool: pointer to the memory pool which was allocated via
35 * Free all reserved elements in @pool and @pool itself. This function
36 * only sleeps if the free_fn() function sleeps.
38 void mempool_destroy(mempool_t
*pool
)
40 while (pool
->curr_nr
) {
41 void *element
= remove_element(pool
);
42 pool
->free(element
, pool
->pool_data
);
44 kfree(pool
->elements
);
47 EXPORT_SYMBOL(mempool_destroy
);
50 * mempool_create - create a memory pool
51 * @min_nr: the minimum number of elements guaranteed to be
52 * allocated for this pool.
53 * @alloc_fn: user-defined element-allocation function.
54 * @free_fn: user-defined element-freeing function.
55 * @pool_data: optional private data available to the user-defined functions.
57 * this function creates and allocates a guaranteed size, preallocated
58 * memory pool. The pool can be used from the mempool_alloc() and mempool_free()
59 * functions. This function might sleep. Both the alloc_fn() and the free_fn()
60 * functions might sleep - as long as the mempool_alloc() function is not called
63 mempool_t
*mempool_create(int min_nr
, mempool_alloc_t
*alloc_fn
,
64 mempool_free_t
*free_fn
, void *pool_data
)
66 return mempool_create_node(min_nr
,alloc_fn
,free_fn
, pool_data
,-1);
68 EXPORT_SYMBOL(mempool_create
);
70 mempool_t
*mempool_create_node(int min_nr
, mempool_alloc_t
*alloc_fn
,
71 mempool_free_t
*free_fn
, void *pool_data
, int node_id
)
74 pool
= kmalloc_node(sizeof(*pool
), GFP_KERNEL
| __GFP_ZERO
, node_id
);
77 pool
->elements
= kmalloc_node(min_nr
* sizeof(void *),
79 if (!pool
->elements
) {
83 spin_lock_init(&pool
->lock
);
84 pool
->min_nr
= min_nr
;
85 pool
->pool_data
= pool_data
;
86 init_waitqueue_head(&pool
->wait
);
87 pool
->alloc
= alloc_fn
;
91 * First pre-allocate the guaranteed number of buffers.
93 while (pool
->curr_nr
< pool
->min_nr
) {
96 element
= pool
->alloc(GFP_KERNEL
, pool
->pool_data
);
97 if (unlikely(!element
)) {
98 mempool_destroy(pool
);
101 add_element(pool
, element
);
105 EXPORT_SYMBOL(mempool_create_node
);
108 * mempool_resize - resize an existing memory pool
109 * @pool: pointer to the memory pool which was allocated via
111 * @new_min_nr: the new minimum number of elements guaranteed to be
112 * allocated for this pool.
113 * @gfp_mask: the usual allocation bitmask.
115 * This function shrinks/grows the pool. In the case of growing,
116 * it cannot be guaranteed that the pool will be grown to the new
117 * size immediately, but new mempool_free() calls will refill it.
119 * Note, the caller must guarantee that no mempool_destroy is called
120 * while this function is running. mempool_alloc() & mempool_free()
121 * might be called (eg. from IRQ contexts) while this function executes.
123 int mempool_resize(mempool_t
*pool
, int new_min_nr
, gfp_t gfp_mask
)
129 BUG_ON(new_min_nr
<= 0);
131 spin_lock_irqsave(&pool
->lock
, flags
);
132 if (new_min_nr
<= pool
->min_nr
) {
133 while (new_min_nr
< pool
->curr_nr
) {
134 element
= remove_element(pool
);
135 spin_unlock_irqrestore(&pool
->lock
, flags
);
136 pool
->free(element
, pool
->pool_data
);
137 spin_lock_irqsave(&pool
->lock
, flags
);
139 pool
->min_nr
= new_min_nr
;
142 spin_unlock_irqrestore(&pool
->lock
, flags
);
145 new_elements
= kmalloc(new_min_nr
* sizeof(*new_elements
), gfp_mask
);
149 spin_lock_irqsave(&pool
->lock
, flags
);
150 if (unlikely(new_min_nr
<= pool
->min_nr
)) {
151 /* Raced, other resize will do our work */
152 spin_unlock_irqrestore(&pool
->lock
, flags
);
156 memcpy(new_elements
, pool
->elements
,
157 pool
->curr_nr
* sizeof(*new_elements
));
158 kfree(pool
->elements
);
159 pool
->elements
= new_elements
;
160 pool
->min_nr
= new_min_nr
;
162 while (pool
->curr_nr
< pool
->min_nr
) {
163 spin_unlock_irqrestore(&pool
->lock
, flags
);
164 element
= pool
->alloc(gfp_mask
, pool
->pool_data
);
167 spin_lock_irqsave(&pool
->lock
, flags
);
168 if (pool
->curr_nr
< pool
->min_nr
) {
169 add_element(pool
, element
);
171 spin_unlock_irqrestore(&pool
->lock
, flags
);
172 pool
->free(element
, pool
->pool_data
); /* Raced */
177 spin_unlock_irqrestore(&pool
->lock
, flags
);
181 EXPORT_SYMBOL(mempool_resize
);
184 * mempool_alloc - allocate an element from a specific memory pool
185 * @pool: pointer to the memory pool which was allocated via
187 * @gfp_mask: the usual allocation bitmask.
189 * this function only sleeps if the alloc_fn() function sleeps or
190 * returns NULL. Note that due to preallocation, this function
191 * *never* fails when called from process contexts. (it might
192 * fail if called from an IRQ context.)
194 void * mempool_alloc(mempool_t
*pool
, gfp_t gfp_mask
)
201 might_sleep_if(gfp_mask
& __GFP_WAIT
);
203 gfp_mask
|= __GFP_NOMEMALLOC
; /* don't allocate emergency reserves */
204 gfp_mask
|= __GFP_NORETRY
; /* don't loop in __alloc_pages */
205 gfp_mask
|= __GFP_NOWARN
; /* failures are OK */
207 gfp_temp
= gfp_mask
& ~(__GFP_WAIT
|__GFP_IO
);
211 element
= pool
->alloc(gfp_temp
, pool
->pool_data
);
212 if (likely(element
!= NULL
))
215 spin_lock_irqsave(&pool
->lock
, flags
);
216 if (likely(pool
->curr_nr
)) {
217 element
= remove_element(pool
);
218 spin_unlock_irqrestore(&pool
->lock
, flags
);
219 /* paired with rmb in mempool_free(), read comment there */
225 * We use gfp mask w/o __GFP_WAIT or IO for the first round. If
226 * alloc failed with that and @pool was empty, retry immediately.
228 if (gfp_temp
!= gfp_mask
) {
229 spin_unlock_irqrestore(&pool
->lock
, flags
);
234 /* We must not sleep if !__GFP_WAIT */
235 if (!(gfp_mask
& __GFP_WAIT
)) {
236 spin_unlock_irqrestore(&pool
->lock
, flags
);
240 /* Let's wait for someone else to return an element to @pool */
242 prepare_to_wait(&pool
->wait
, &wait
, TASK_UNINTERRUPTIBLE
);
244 spin_unlock_irqrestore(&pool
->lock
, flags
);
247 * FIXME: this should be io_schedule(). The timeout is there as a
248 * workaround for some DM problems in 2.6.18.
250 io_schedule_timeout(5*HZ
);
252 finish_wait(&pool
->wait
, &wait
);
255 EXPORT_SYMBOL(mempool_alloc
);
258 * mempool_free - return an element to the pool.
259 * @element: pool element pointer.
260 * @pool: pointer to the memory pool which was allocated via
263 * this function only sleeps if the free_fn() function sleeps.
265 void mempool_free(void *element
, mempool_t
*pool
)
269 if (unlikely(element
== NULL
))
273 * Paired with the wmb in mempool_alloc(). The preceding read is
274 * for @element and the following @pool->curr_nr. This ensures
275 * that the visible value of @pool->curr_nr is from after the
276 * allocation of @element. This is necessary for fringe cases
277 * where @element was passed to this task without going through
280 * For example, assume @p is %NULL at the beginning and one task
281 * performs "p = mempool_alloc(...);" while another task is doing
282 * "while (!p) cpu_relax(); mempool_free(p, ...);". This function
283 * may end up using curr_nr value which is from before allocation
284 * of @p without the following rmb.
289 * For correctness, we need a test which is guaranteed to trigger
290 * if curr_nr + #allocated == min_nr. Testing curr_nr < min_nr
291 * without locking achieves that and refilling as soon as possible
294 * Because curr_nr visible here is always a value after the
295 * allocation of @element, any task which decremented curr_nr below
296 * min_nr is guaranteed to see curr_nr < min_nr unless curr_nr gets
297 * incremented to min_nr afterwards. If curr_nr gets incremented
298 * to min_nr after the allocation of @element, the elements
299 * allocated after that are subject to the same guarantee.
301 * Waiters happen iff curr_nr is 0 and the above guarantee also
302 * ensures that there will be frees which return elements to the
303 * pool waking up the waiters.
305 if (pool
->curr_nr
< pool
->min_nr
) {
306 spin_lock_irqsave(&pool
->lock
, flags
);
307 if (pool
->curr_nr
< pool
->min_nr
) {
308 add_element(pool
, element
);
309 spin_unlock_irqrestore(&pool
->lock
, flags
);
310 wake_up(&pool
->wait
);
313 spin_unlock_irqrestore(&pool
->lock
, flags
);
315 pool
->free(element
, pool
->pool_data
);
317 EXPORT_SYMBOL(mempool_free
);
320 * A commonly used alloc and free fn.
322 void *mempool_alloc_slab(gfp_t gfp_mask
, void *pool_data
)
324 struct kmem_cache
*mem
= pool_data
;
325 return kmem_cache_alloc(mem
, gfp_mask
);
327 EXPORT_SYMBOL(mempool_alloc_slab
);
329 void mempool_free_slab(void *element
, void *pool_data
)
331 struct kmem_cache
*mem
= pool_data
;
332 kmem_cache_free(mem
, element
);
334 EXPORT_SYMBOL(mempool_free_slab
);
337 * A commonly used alloc and free fn that kmalloc/kfrees the amount of memory
338 * specified by pool_data
340 void *mempool_kmalloc(gfp_t gfp_mask
, void *pool_data
)
342 size_t size
= (size_t)pool_data
;
343 return kmalloc(size
, gfp_mask
);
345 EXPORT_SYMBOL(mempool_kmalloc
);
347 void mempool_kfree(void *element
, void *pool_data
)
351 EXPORT_SYMBOL(mempool_kfree
);
354 * A simple mempool-backed page allocator that allocates pages
355 * of the order specified by pool_data.
357 void *mempool_alloc_pages(gfp_t gfp_mask
, void *pool_data
)
359 int order
= (int)(long)pool_data
;
360 return alloc_pages(gfp_mask
, order
);
362 EXPORT_SYMBOL(mempool_alloc_pages
);
364 void mempool_free_pages(void *element
, void *pool_data
)
366 int order
= (int)(long)pool_data
;
367 __free_pages(element
, order
);
369 EXPORT_SYMBOL(mempool_free_pages
);
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