blob: c9f3d46204287e7994711efd37059b1a151d7232 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * linux/mm/mempool.c
3 *
4 * memory buffer pool support. Such pools are mostly used
5 * for guaranteed, deadlock-free memory allocations during
6 * extreme VM load.
7 *
8 * started by Ingo Molnar, Copyright (C) 2001
9 */
10
11#include <linux/mm.h>
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>
17
18static void add_element(mempool_t *pool, void *element)
19{
20 BUG_ON(pool->curr_nr >= pool->min_nr);
21 pool->elements[pool->curr_nr++] = element;
22}
23
24static void *remove_element(mempool_t *pool)
25{
26 BUG_ON(pool->curr_nr <= 0);
27 return pool->elements[--pool->curr_nr];
28}
29
30static void free_pool(mempool_t *pool)
31{
32 while (pool->curr_nr) {
33 void *element = remove_element(pool);
34 pool->free(element, pool->pool_data);
35 }
36 kfree(pool->elements);
37 kfree(pool);
38}
39
40/**
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.
47 *
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
52 * from IRQ contexts.
53 */
54mempool_t * mempool_create(int min_nr, mempool_alloc_t *alloc_fn,
55 mempool_free_t *free_fn, void *pool_data)
56{
57 mempool_t *pool;
58
59 pool = kmalloc(sizeof(*pool), GFP_KERNEL);
60 if (!pool)
61 return NULL;
62 memset(pool, 0, sizeof(*pool));
63 pool->elements = kmalloc(min_nr * sizeof(void *), GFP_KERNEL);
64 if (!pool->elements) {
65 kfree(pool);
66 return NULL;
67 }
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;
73 pool->free = free_fn;
74
75 /*
76 * First pre-allocate the guaranteed number of buffers.
77 */
78 while (pool->curr_nr < pool->min_nr) {
79 void *element;
80
81 element = pool->alloc(GFP_KERNEL, pool->pool_data);
82 if (unlikely(!element)) {
83 free_pool(pool);
84 return NULL;
85 }
86 add_element(pool, element);
87 }
88 return pool;
89}
90EXPORT_SYMBOL(mempool_create);
91
92/**
93 * mempool_resize - resize an existing memory pool
94 * @pool: pointer to the memory pool which was allocated via
95 * mempool_create().
96 * @new_min_nr: the new minimum number of elements guaranteed to be
97 * allocated for this pool.
98 * @gfp_mask: the usual allocation bitmask.
99 *
100 * This function shrinks/grows the pool. In the case of growing,
101 * it cannot be guaranteed that the pool will be grown to the new
102 * size immediately, but new mempool_free() calls will refill it.
103 *
104 * Note, the caller must guarantee that no mempool_destroy is called
105 * while this function is running. mempool_alloc() & mempool_free()
106 * might be called (eg. from IRQ contexts) while this function executes.
107 */
108int mempool_resize(mempool_t *pool, int new_min_nr, unsigned int __nocast gfp_mask)
109{
110 void *element;
111 void **new_elements;
112 unsigned long flags;
113
114 BUG_ON(new_min_nr <= 0);
115
116 spin_lock_irqsave(&pool->lock, flags);
117 if (new_min_nr <= pool->min_nr) {
118 while (new_min_nr < pool->curr_nr) {
119 element = remove_element(pool);
120 spin_unlock_irqrestore(&pool->lock, flags);
121 pool->free(element, pool->pool_data);
122 spin_lock_irqsave(&pool->lock, flags);
123 }
124 pool->min_nr = new_min_nr;
125 goto out_unlock;
126 }
127 spin_unlock_irqrestore(&pool->lock, flags);
128
129 /* Grow the pool */
130 new_elements = kmalloc(new_min_nr * sizeof(*new_elements), gfp_mask);
131 if (!new_elements)
132 return -ENOMEM;
133
134 spin_lock_irqsave(&pool->lock, flags);
135 if (unlikely(new_min_nr <= pool->min_nr)) {
136 /* Raced, other resize will do our work */
137 spin_unlock_irqrestore(&pool->lock, flags);
138 kfree(new_elements);
139 goto out;
140 }
141 memcpy(new_elements, pool->elements,
142 pool->curr_nr * sizeof(*new_elements));
143 kfree(pool->elements);
144 pool->elements = new_elements;
145 pool->min_nr = new_min_nr;
146
147 while (pool->curr_nr < pool->min_nr) {
148 spin_unlock_irqrestore(&pool->lock, flags);
149 element = pool->alloc(gfp_mask, pool->pool_data);
150 if (!element)
151 goto out;
152 spin_lock_irqsave(&pool->lock, flags);
153 if (pool->curr_nr < pool->min_nr) {
154 add_element(pool, element);
155 } else {
156 spin_unlock_irqrestore(&pool->lock, flags);
157 pool->free(element, pool->pool_data); /* Raced */
158 goto out;
159 }
160 }
161out_unlock:
162 spin_unlock_irqrestore(&pool->lock, flags);
163out:
164 return 0;
165}
166EXPORT_SYMBOL(mempool_resize);
167
168/**
169 * mempool_destroy - deallocate a memory pool
170 * @pool: pointer to the memory pool which was allocated via
171 * mempool_create().
172 *
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().
176 */
177void mempool_destroy(mempool_t *pool)
178{
179 if (pool->curr_nr != pool->min_nr)
180 BUG(); /* There were outstanding elements */
181 free_pool(pool);
182}
183EXPORT_SYMBOL(mempool_destroy);
184
185/**
186 * mempool_alloc - allocate an element from a specific memory pool
187 * @pool: pointer to the memory pool which was allocated via
188 * mempool_create().
189 * @gfp_mask: the usual allocation bitmask.
190 *
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.)
195 */
196void * mempool_alloc(mempool_t *pool, unsigned int __nocast gfp_mask)
197{
198 void *element;
199 unsigned long flags;
200 DEFINE_WAIT(wait);
Nick Piggin20a77772005-05-01 08:58:37 -0700201 int gfp_temp;
202
203 might_sleep_if(gfp_mask & __GFP_WAIT);
Nick Pigginb84a35b2005-05-01 08:58:36 -0700204
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 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700208
Nick Piggin20a77772005-05-01 08:58:37 -0700209 gfp_temp = gfp_mask & ~(__GFP_WAIT|__GFP_IO);
210
Linus Torvalds1da177e2005-04-16 15:20:36 -0700211repeat_alloc:
Nick Piggin20a77772005-05-01 08:58:37 -0700212
213 element = pool->alloc(gfp_temp, pool->pool_data);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700214 if (likely(element != NULL))
215 return element;
216
Linus Torvalds1da177e2005-04-16 15:20:36 -0700217 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 return element;
222 }
223 spin_unlock_irqrestore(&pool->lock, flags);
224
225 /* We must not sleep in the GFP_ATOMIC case */
226 if (!(gfp_mask & __GFP_WAIT))
227 return NULL;
228
Nick Piggin20a77772005-05-01 08:58:37 -0700229 /* Now start performing page reclaim */
230 gfp_temp = gfp_mask;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700231 prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE);
akpm@osdl.orgd59dd462005-05-01 08:58:47 -0700232 smp_mb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700233 if (!pool->curr_nr)
234 io_schedule();
235 finish_wait(&pool->wait, &wait);
236
237 goto repeat_alloc;
238}
239EXPORT_SYMBOL(mempool_alloc);
240
241/**
242 * mempool_free - return an element to the pool.
243 * @element: pool element pointer.
244 * @pool: pointer to the memory pool which was allocated via
245 * mempool_create().
246 *
247 * this function only sleeps if the free_fn() function sleeps.
248 */
249void mempool_free(void *element, mempool_t *pool)
250{
251 unsigned long flags;
252
akpm@osdl.orgd59dd462005-05-01 08:58:47 -0700253 smp_mb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700254 if (pool->curr_nr < pool->min_nr) {
255 spin_lock_irqsave(&pool->lock, flags);
256 if (pool->curr_nr < pool->min_nr) {
257 add_element(pool, element);
258 spin_unlock_irqrestore(&pool->lock, flags);
259 wake_up(&pool->wait);
260 return;
261 }
262 spin_unlock_irqrestore(&pool->lock, flags);
263 }
264 pool->free(element, pool->pool_data);
265}
266EXPORT_SYMBOL(mempool_free);
267
268/*
269 * A commonly used alloc and free fn.
270 */
271void *mempool_alloc_slab(unsigned int __nocast gfp_mask, void *pool_data)
272{
273 kmem_cache_t *mem = (kmem_cache_t *) pool_data;
274 return kmem_cache_alloc(mem, gfp_mask);
275}
276EXPORT_SYMBOL(mempool_alloc_slab);
277
278void mempool_free_slab(void *element, void *pool_data)
279{
280 kmem_cache_t *mem = (kmem_cache_t *) pool_data;
281 kmem_cache_free(mem, element);
282}
283EXPORT_SYMBOL(mempool_free_slab);