Contents of /alx-src/tags/kernel26-2.6.12-alx-r9/mm/mempool.c
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Wed Mar 4 11:03:09 2009 UTC (15 years, 6 months ago) by niro
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Wed Mar 4 11:03:09 2009 UTC (15 years, 6 months ago) by niro
File MIME type: text/plain
File size: 7872 byte(s)
Tag kernel26-2.6.12-alx-r9
1 | /* |
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 | |
18 | static 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 | |
24 | static void *remove_element(mempool_t *pool) |
25 | { |
26 | BUG_ON(pool->curr_nr <= 0); |
27 | return pool->elements[--pool->curr_nr]; |
28 | } |
29 | |
30 | static 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 | */ |
54 | mempool_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 | } |
90 | EXPORT_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 | */ |
108 | int 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 | } |
161 | out_unlock: |
162 | spin_unlock_irqrestore(&pool->lock, flags); |
163 | out: |
164 | return 0; |
165 | } |
166 | EXPORT_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 | */ |
177 | void 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 | } |
183 | EXPORT_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 | */ |
196 | void * mempool_alloc(mempool_t *pool, unsigned int __nocast gfp_mask) |
197 | { |
198 | void *element; |
199 | unsigned long flags; |
200 | DEFINE_WAIT(wait); |
201 | int gfp_temp; |
202 | |
203 | might_sleep_if(gfp_mask & __GFP_WAIT); |
204 | |
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 */ |
208 | |
209 | gfp_temp = gfp_mask & ~(__GFP_WAIT|__GFP_IO); |
210 | |
211 | repeat_alloc: |
212 | |
213 | element = pool->alloc(gfp_temp, pool->pool_data); |
214 | if (likely(element != NULL)) |
215 | return element; |
216 | |
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 | 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 | |
229 | /* Now start performing page reclaim */ |
230 | gfp_temp = gfp_mask; |
231 | prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE); |
232 | smp_mb(); |
233 | if (!pool->curr_nr) |
234 | io_schedule(); |
235 | finish_wait(&pool->wait, &wait); |
236 | |
237 | goto repeat_alloc; |
238 | } |
239 | EXPORT_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 | */ |
249 | void mempool_free(void *element, mempool_t *pool) |
250 | { |
251 | unsigned long flags; |
252 | |
253 | smp_mb(); |
254 | 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 | } |
266 | EXPORT_SYMBOL(mempool_free); |
267 | |
268 | /* |
269 | * A commonly used alloc and free fn. |
270 | */ |
271 | void *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 | } |
276 | EXPORT_SYMBOL(mempool_alloc_slab); |
277 | |
278 | void 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 | } |
283 | EXPORT_SYMBOL(mempool_free_slab); |