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/kmemleak.h>
14 #include <linux/export.h>
15 #include <linux/mempool.h>
16 #include <linux/blkdev.h>
17 #include <linux/writeback.h>
19 static void add_element(mempool_t
*pool
, void *element
)
21 BUG_ON(pool
->curr_nr
>= pool
->min_nr
);
22 pool
->elements
[pool
->curr_nr
++] = element
;
25 static void *remove_element(mempool_t
*pool
)
27 BUG_ON(pool
->curr_nr
<= 0);
28 return pool
->elements
[--pool
->curr_nr
];
32 * mempool_destroy - deallocate a memory pool
33 * @pool: pointer to the memory pool which was allocated via
36 * Free all reserved elements in @pool and @pool itself. This function
37 * only sleeps if the free_fn() function sleeps.
39 void mempool_destroy(mempool_t
*pool
)
41 while (pool
->curr_nr
) {
42 void *element
= remove_element(pool
);
43 pool
->free(element
, pool
->pool_data
);
45 kfree(pool
->elements
);
48 EXPORT_SYMBOL(mempool_destroy
);
51 * mempool_create - create a memory pool
52 * @min_nr: the minimum number of elements guaranteed to be
53 * allocated for this pool.
54 * @alloc_fn: user-defined element-allocation function.
55 * @free_fn: user-defined element-freeing function.
56 * @pool_data: optional private data available to the user-defined functions.
58 * this function creates and allocates a guaranteed size, preallocated
59 * memory pool. The pool can be used from the mempool_alloc() and mempool_free()
60 * functions. This function might sleep. Both the alloc_fn() and the free_fn()
61 * functions might sleep - as long as the mempool_alloc() function is not called
64 mempool_t
*mempool_create(int min_nr
, mempool_alloc_t
*alloc_fn
,
65 mempool_free_t
*free_fn
, void *pool_data
)
67 return mempool_create_node(min_nr
,alloc_fn
,free_fn
, pool_data
,
68 GFP_KERNEL
, NUMA_NO_NODE
);
70 EXPORT_SYMBOL(mempool_create
);
72 mempool_t
*mempool_create_node(int min_nr
, mempool_alloc_t
*alloc_fn
,
73 mempool_free_t
*free_fn
, void *pool_data
,
74 gfp_t gfp_mask
, int node_id
)
77 pool
= kzalloc_node(sizeof(*pool
), gfp_mask
, node_id
);
80 pool
->elements
= kmalloc_node(min_nr
* sizeof(void *),
82 if (!pool
->elements
) {
86 spin_lock_init(&pool
->lock
);
87 pool
->min_nr
= min_nr
;
88 pool
->pool_data
= pool_data
;
89 init_waitqueue_head(&pool
->wait
);
90 pool
->alloc
= alloc_fn
;
94 * First pre-allocate the guaranteed number of buffers.
96 while (pool
->curr_nr
< pool
->min_nr
) {
99 element
= pool
->alloc(gfp_mask
, pool
->pool_data
);
100 if (unlikely(!element
)) {
101 mempool_destroy(pool
);
104 add_element(pool
, element
);
108 EXPORT_SYMBOL(mempool_create_node
);
111 * mempool_resize - resize an existing memory pool
112 * @pool: pointer to the memory pool which was allocated via
114 * @new_min_nr: the new minimum number of elements guaranteed to be
115 * allocated for this pool.
117 * This function shrinks/grows the pool. In the case of growing,
118 * it cannot be guaranteed that the pool will be grown to the new
119 * size immediately, but new mempool_free() calls will refill it.
120 * This function may sleep.
122 * Note, the caller must guarantee that no mempool_destroy is called
123 * while this function is running. mempool_alloc() & mempool_free()
124 * might be called (eg. from IRQ contexts) while this function executes.
126 int mempool_resize(mempool_t
*pool
, int new_min_nr
)
132 BUG_ON(new_min_nr
<= 0);
135 spin_lock_irqsave(&pool
->lock
, flags
);
136 if (new_min_nr
<= pool
->min_nr
) {
137 while (new_min_nr
< pool
->curr_nr
) {
138 element
= remove_element(pool
);
139 spin_unlock_irqrestore(&pool
->lock
, flags
);
140 pool
->free(element
, pool
->pool_data
);
141 spin_lock_irqsave(&pool
->lock
, flags
);
143 pool
->min_nr
= new_min_nr
;
146 spin_unlock_irqrestore(&pool
->lock
, flags
);
149 new_elements
= kmalloc_array(new_min_nr
, sizeof(*new_elements
),
154 spin_lock_irqsave(&pool
->lock
, flags
);
155 if (unlikely(new_min_nr
<= pool
->min_nr
)) {
156 /* Raced, other resize will do our work */
157 spin_unlock_irqrestore(&pool
->lock
, flags
);
161 memcpy(new_elements
, pool
->elements
,
162 pool
->curr_nr
* sizeof(*new_elements
));
163 kfree(pool
->elements
);
164 pool
->elements
= new_elements
;
165 pool
->min_nr
= new_min_nr
;
167 while (pool
->curr_nr
< pool
->min_nr
) {
168 spin_unlock_irqrestore(&pool
->lock
, flags
);
169 element
= pool
->alloc(GFP_KERNEL
, pool
->pool_data
);
172 spin_lock_irqsave(&pool
->lock
, flags
);
173 if (pool
->curr_nr
< pool
->min_nr
) {
174 add_element(pool
, element
);
176 spin_unlock_irqrestore(&pool
->lock
, flags
);
177 pool
->free(element
, pool
->pool_data
); /* Raced */
182 spin_unlock_irqrestore(&pool
->lock
, flags
);
186 EXPORT_SYMBOL(mempool_resize
);
189 * mempool_alloc - allocate an element from a specific memory pool
190 * @pool: pointer to the memory pool which was allocated via
192 * @gfp_mask: the usual allocation bitmask.
194 * this function only sleeps if the alloc_fn() function sleeps or
195 * returns NULL. Note that due to preallocation, this function
196 * *never* fails when called from process contexts. (it might
197 * fail if called from an IRQ context.)
198 * Note: using __GFP_ZERO is not supported.
200 void * mempool_alloc(mempool_t
*pool
, gfp_t gfp_mask
)
207 VM_WARN_ON_ONCE(gfp_mask
& __GFP_ZERO
);
208 might_sleep_if(gfp_mask
& __GFP_WAIT
);
210 gfp_mask
|= __GFP_NOMEMALLOC
; /* don't allocate emergency reserves */
211 gfp_mask
|= __GFP_NORETRY
; /* don't loop in __alloc_pages */
212 gfp_mask
|= __GFP_NOWARN
; /* failures are OK */
214 gfp_temp
= gfp_mask
& ~(__GFP_WAIT
|__GFP_IO
);
218 element
= pool
->alloc(gfp_temp
, pool
->pool_data
);
219 if (likely(element
!= NULL
))
222 spin_lock_irqsave(&pool
->lock
, flags
);
223 if (likely(pool
->curr_nr
)) {
224 element
= remove_element(pool
);
225 spin_unlock_irqrestore(&pool
->lock
, flags
);
226 /* paired with rmb in mempool_free(), read comment there */
229 * Update the allocation stack trace as this is more useful
232 kmemleak_update_trace(element
);
237 * We use gfp mask w/o __GFP_WAIT or IO for the first round. If
238 * alloc failed with that and @pool was empty, retry immediately.
240 if (gfp_temp
!= gfp_mask
) {
241 spin_unlock_irqrestore(&pool
->lock
, flags
);
246 /* We must not sleep if !__GFP_WAIT */
247 if (!(gfp_mask
& __GFP_WAIT
)) {
248 spin_unlock_irqrestore(&pool
->lock
, flags
);
252 /* Let's wait for someone else to return an element to @pool */
254 prepare_to_wait(&pool
->wait
, &wait
, TASK_UNINTERRUPTIBLE
);
256 spin_unlock_irqrestore(&pool
->lock
, flags
);
259 * FIXME: this should be io_schedule(). The timeout is there as a
260 * workaround for some DM problems in 2.6.18.
262 io_schedule_timeout(5*HZ
);
264 finish_wait(&pool
->wait
, &wait
);
267 EXPORT_SYMBOL(mempool_alloc
);
270 * mempool_free - return an element to the pool.
271 * @element: pool element pointer.
272 * @pool: pointer to the memory pool which was allocated via
275 * this function only sleeps if the free_fn() function sleeps.
277 void mempool_free(void *element
, mempool_t
*pool
)
281 if (unlikely(element
== NULL
))
285 * Paired with the wmb in mempool_alloc(). The preceding read is
286 * for @element and the following @pool->curr_nr. This ensures
287 * that the visible value of @pool->curr_nr is from after the
288 * allocation of @element. This is necessary for fringe cases
289 * where @element was passed to this task without going through
292 * For example, assume @p is %NULL at the beginning and one task
293 * performs "p = mempool_alloc(...);" while another task is doing
294 * "while (!p) cpu_relax(); mempool_free(p, ...);". This function
295 * may end up using curr_nr value which is from before allocation
296 * of @p without the following rmb.
301 * For correctness, we need a test which is guaranteed to trigger
302 * if curr_nr + #allocated == min_nr. Testing curr_nr < min_nr
303 * without locking achieves that and refilling as soon as possible
306 * Because curr_nr visible here is always a value after the
307 * allocation of @element, any task which decremented curr_nr below
308 * min_nr is guaranteed to see curr_nr < min_nr unless curr_nr gets
309 * incremented to min_nr afterwards. If curr_nr gets incremented
310 * to min_nr after the allocation of @element, the elements
311 * allocated after that are subject to the same guarantee.
313 * Waiters happen iff curr_nr is 0 and the above guarantee also
314 * ensures that there will be frees which return elements to the
315 * pool waking up the waiters.
317 if (unlikely(pool
->curr_nr
< pool
->min_nr
)) {
318 spin_lock_irqsave(&pool
->lock
, flags
);
319 if (likely(pool
->curr_nr
< pool
->min_nr
)) {
320 add_element(pool
, element
);
321 spin_unlock_irqrestore(&pool
->lock
, flags
);
322 wake_up(&pool
->wait
);
325 spin_unlock_irqrestore(&pool
->lock
, flags
);
327 pool
->free(element
, pool
->pool_data
);
329 EXPORT_SYMBOL(mempool_free
);
332 * A commonly used alloc and free fn.
334 void *mempool_alloc_slab(gfp_t gfp_mask
, void *pool_data
)
336 struct kmem_cache
*mem
= pool_data
;
337 return kmem_cache_alloc(mem
, gfp_mask
);
339 EXPORT_SYMBOL(mempool_alloc_slab
);
341 void mempool_free_slab(void *element
, void *pool_data
)
343 struct kmem_cache
*mem
= pool_data
;
344 kmem_cache_free(mem
, element
);
346 EXPORT_SYMBOL(mempool_free_slab
);
349 * A commonly used alloc and free fn that kmalloc/kfrees the amount of memory
350 * specified by pool_data
352 void *mempool_kmalloc(gfp_t gfp_mask
, void *pool_data
)
354 size_t size
= (size_t)pool_data
;
355 return kmalloc(size
, gfp_mask
);
357 EXPORT_SYMBOL(mempool_kmalloc
);
359 void mempool_kfree(void *element
, void *pool_data
)
363 EXPORT_SYMBOL(mempool_kfree
);
366 * A simple mempool-backed page allocator that allocates pages
367 * of the order specified by pool_data.
369 void *mempool_alloc_pages(gfp_t gfp_mask
, void *pool_data
)
371 int order
= (int)(long)pool_data
;
372 return alloc_pages(gfp_mask
, order
);
374 EXPORT_SYMBOL(mempool_alloc_pages
);
376 void mempool_free_pages(void *element
, void *pool_data
)
378 int order
= (int)(long)pool_data
;
379 __free_pages(element
, order
);
381 EXPORT_SYMBOL(mempool_free_pages
);
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