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git.proxmox.com Git - mirror_ubuntu-zesty-kernel.git/blob - mm/mempool.c
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
,
67 GFP_KERNEL
, NUMA_NO_NODE
);
69 EXPORT_SYMBOL(mempool_create
);
71 mempool_t
*mempool_create_node(int min_nr
, mempool_alloc_t
*alloc_fn
,
72 mempool_free_t
*free_fn
, void *pool_data
,
73 gfp_t gfp_mask
, int node_id
)
76 pool
= kzalloc_node(sizeof(*pool
), gfp_mask
, node_id
);
79 pool
->elements
= kmalloc_node(min_nr
* sizeof(void *),
81 if (!pool
->elements
) {
85 spin_lock_init(&pool
->lock
);
86 pool
->min_nr
= min_nr
;
87 pool
->pool_data
= pool_data
;
88 init_waitqueue_head(&pool
->wait
);
89 pool
->alloc
= alloc_fn
;
93 * First pre-allocate the guaranteed number of buffers.
95 while (pool
->curr_nr
< pool
->min_nr
) {
98 element
= pool
->alloc(gfp_mask
, pool
->pool_data
);
99 if (unlikely(!element
)) {
100 mempool_destroy(pool
);
103 add_element(pool
, element
);
107 EXPORT_SYMBOL(mempool_create_node
);
110 * mempool_resize - resize an existing memory pool
111 * @pool: pointer to the memory pool which was allocated via
113 * @new_min_nr: the new minimum number of elements guaranteed to be
114 * allocated for this pool.
115 * @gfp_mask: the usual allocation bitmask.
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.
121 * Note, the caller must guarantee that no mempool_destroy is called
122 * while this function is running. mempool_alloc() & mempool_free()
123 * might be called (eg. from IRQ contexts) while this function executes.
125 int mempool_resize(mempool_t
*pool
, int new_min_nr
, gfp_t gfp_mask
)
131 BUG_ON(new_min_nr
<= 0);
133 spin_lock_irqsave(&pool
->lock
, flags
);
134 if (new_min_nr
<= pool
->min_nr
) {
135 while (new_min_nr
< pool
->curr_nr
) {
136 element
= remove_element(pool
);
137 spin_unlock_irqrestore(&pool
->lock
, flags
);
138 pool
->free(element
, pool
->pool_data
);
139 spin_lock_irqsave(&pool
->lock
, flags
);
141 pool
->min_nr
= new_min_nr
;
144 spin_unlock_irqrestore(&pool
->lock
, flags
);
147 new_elements
= kmalloc(new_min_nr
* sizeof(*new_elements
), gfp_mask
);
151 spin_lock_irqsave(&pool
->lock
, flags
);
152 if (unlikely(new_min_nr
<= pool
->min_nr
)) {
153 /* Raced, other resize will do our work */
154 spin_unlock_irqrestore(&pool
->lock
, flags
);
158 memcpy(new_elements
, pool
->elements
,
159 pool
->curr_nr
* sizeof(*new_elements
));
160 kfree(pool
->elements
);
161 pool
->elements
= new_elements
;
162 pool
->min_nr
= new_min_nr
;
164 while (pool
->curr_nr
< pool
->min_nr
) {
165 spin_unlock_irqrestore(&pool
->lock
, flags
);
166 element
= pool
->alloc(gfp_mask
, pool
->pool_data
);
169 spin_lock_irqsave(&pool
->lock
, flags
);
170 if (pool
->curr_nr
< pool
->min_nr
) {
171 add_element(pool
, element
);
173 spin_unlock_irqrestore(&pool
->lock
, flags
);
174 pool
->free(element
, pool
->pool_data
); /* Raced */
179 spin_unlock_irqrestore(&pool
->lock
, flags
);
183 EXPORT_SYMBOL(mempool_resize
);
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
, gfp_t gfp_mask
)
203 might_sleep_if(gfp_mask
& __GFP_WAIT
);
205 gfp_mask
|= __GFP_NOMEMALLOC
; /* don't allocate emergency reserves */
206 gfp_mask
|= __GFP_NORETRY
; /* don't loop in __alloc_pages */
207 gfp_mask
|= __GFP_NOWARN
; /* failures are OK */
209 gfp_temp
= gfp_mask
& ~(__GFP_WAIT
|__GFP_IO
);
213 element
= pool
->alloc(gfp_temp
, pool
->pool_data
);
214 if (likely(element
!= NULL
))
217 spin_lock_irqsave(&pool
->lock
, flags
);
218 if (likely(pool
->curr_nr
)) {
219 element
= remove_element(pool
);
220 spin_unlock_irqrestore(&pool
->lock
, flags
);
221 /* paired with rmb in mempool_free(), read comment there */
227 * We use gfp mask w/o __GFP_WAIT or IO for the first round. If
228 * alloc failed with that and @pool was empty, retry immediately.
230 if (gfp_temp
!= gfp_mask
) {
231 spin_unlock_irqrestore(&pool
->lock
, flags
);
236 /* We must not sleep if !__GFP_WAIT */
237 if (!(gfp_mask
& __GFP_WAIT
)) {
238 spin_unlock_irqrestore(&pool
->lock
, flags
);
242 /* Let's wait for someone else to return an element to @pool */
244 prepare_to_wait(&pool
->wait
, &wait
, TASK_UNINTERRUPTIBLE
);
246 spin_unlock_irqrestore(&pool
->lock
, flags
);
249 * FIXME: this should be io_schedule(). The timeout is there as a
250 * workaround for some DM problems in 2.6.18.
252 io_schedule_timeout(5*HZ
);
254 finish_wait(&pool
->wait
, &wait
);
257 EXPORT_SYMBOL(mempool_alloc
);
260 * mempool_free - return an element to the pool.
261 * @element: pool element pointer.
262 * @pool: pointer to the memory pool which was allocated via
265 * this function only sleeps if the free_fn() function sleeps.
267 void mempool_free(void *element
, mempool_t
*pool
)
271 if (unlikely(element
== NULL
))
275 * Paired with the wmb in mempool_alloc(). The preceding read is
276 * for @element and the following @pool->curr_nr. This ensures
277 * that the visible value of @pool->curr_nr is from after the
278 * allocation of @element. This is necessary for fringe cases
279 * where @element was passed to this task without going through
282 * For example, assume @p is %NULL at the beginning and one task
283 * performs "p = mempool_alloc(...);" while another task is doing
284 * "while (!p) cpu_relax(); mempool_free(p, ...);". This function
285 * may end up using curr_nr value which is from before allocation
286 * of @p without the following rmb.
291 * For correctness, we need a test which is guaranteed to trigger
292 * if curr_nr + #allocated == min_nr. Testing curr_nr < min_nr
293 * without locking achieves that and refilling as soon as possible
296 * Because curr_nr visible here is always a value after the
297 * allocation of @element, any task which decremented curr_nr below
298 * min_nr is guaranteed to see curr_nr < min_nr unless curr_nr gets
299 * incremented to min_nr afterwards. If curr_nr gets incremented
300 * to min_nr after the allocation of @element, the elements
301 * allocated after that are subject to the same guarantee.
303 * Waiters happen iff curr_nr is 0 and the above guarantee also
304 * ensures that there will be frees which return elements to the
305 * pool waking up the waiters.
307 if (pool
->curr_nr
< pool
->min_nr
) {
308 spin_lock_irqsave(&pool
->lock
, flags
);
309 if (pool
->curr_nr
< pool
->min_nr
) {
310 add_element(pool
, element
);
311 spin_unlock_irqrestore(&pool
->lock
, flags
);
312 wake_up(&pool
->wait
);
315 spin_unlock_irqrestore(&pool
->lock
, flags
);
317 pool
->free(element
, pool
->pool_data
);
319 EXPORT_SYMBOL(mempool_free
);
322 * A commonly used alloc and free fn.
324 void *mempool_alloc_slab(gfp_t gfp_mask
, void *pool_data
)
326 struct kmem_cache
*mem
= pool_data
;
327 return kmem_cache_alloc(mem
, gfp_mask
);
329 EXPORT_SYMBOL(mempool_alloc_slab
);
331 void mempool_free_slab(void *element
, void *pool_data
)
333 struct kmem_cache
*mem
= pool_data
;
334 kmem_cache_free(mem
, element
);
336 EXPORT_SYMBOL(mempool_free_slab
);
339 * A commonly used alloc and free fn that kmalloc/kfrees the amount of memory
340 * specified by pool_data
342 void *mempool_kmalloc(gfp_t gfp_mask
, void *pool_data
)
344 size_t size
= (size_t)pool_data
;
345 return kmalloc(size
, gfp_mask
);
347 EXPORT_SYMBOL(mempool_kmalloc
);
349 void mempool_kfree(void *element
, void *pool_data
)
353 EXPORT_SYMBOL(mempool_kfree
);
356 * A simple mempool-backed page allocator that allocates pages
357 * of the order specified by pool_data.
359 void *mempool_alloc_pages(gfp_t gfp_mask
, void *pool_data
)
361 int order
= (int)(long)pool_data
;
362 return alloc_pages(gfp_mask
, order
);
364 EXPORT_SYMBOL(mempool_alloc_pages
);
366 void mempool_free_pages(void *element
, void *pool_data
)
368 int order
= (int)(long)pool_data
;
369 __free_pages(element
, order
);
371 EXPORT_SYMBOL(mempool_free_pages
);