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1da177e4
LT
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>
17411962 13#include <linux/kmemleak.h>
b95f1b31 14#include <linux/export.h>
1da177e4
LT
15#include <linux/mempool.h>
16#include <linux/blkdev.h>
17#include <linux/writeback.h>
18
19static void add_element(mempool_t *pool, void *element)
20{
21 BUG_ON(pool->curr_nr >= pool->min_nr);
22 pool->elements[pool->curr_nr++] = element;
23}
24
25static void *remove_element(mempool_t *pool)
26{
27 BUG_ON(pool->curr_nr <= 0);
28 return pool->elements[--pool->curr_nr];
29}
30
0565d317
TH
31/**
32 * mempool_destroy - deallocate a memory pool
33 * @pool: pointer to the memory pool which was allocated via
34 * mempool_create().
35 *
36 * Free all reserved elements in @pool and @pool itself. This function
37 * only sleeps if the free_fn() function sleeps.
38 */
39void mempool_destroy(mempool_t *pool)
1da177e4
LT
40{
41 while (pool->curr_nr) {
42 void *element = remove_element(pool);
43 pool->free(element, pool->pool_data);
44 }
45 kfree(pool->elements);
46 kfree(pool);
47}
0565d317 48EXPORT_SYMBOL(mempool_destroy);
1da177e4
LT
49
50/**
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.
57 *
58 * this function creates and allocates a guaranteed size, preallocated
72fd4a35 59 * memory pool. The pool can be used from the mempool_alloc() and mempool_free()
1da177e4 60 * functions. This function might sleep. Both the alloc_fn() and the free_fn()
72fd4a35 61 * functions might sleep - as long as the mempool_alloc() function is not called
1da177e4
LT
62 * from IRQ contexts.
63 */
1946089a 64mempool_t *mempool_create(int min_nr, mempool_alloc_t *alloc_fn,
1da177e4
LT
65 mempool_free_t *free_fn, void *pool_data)
66{
a91a5ac6
TH
67 return mempool_create_node(min_nr,alloc_fn,free_fn, pool_data,
68 GFP_KERNEL, NUMA_NO_NODE);
1946089a
CL
69}
70EXPORT_SYMBOL(mempool_create);
1da177e4 71
1946089a 72mempool_t *mempool_create_node(int min_nr, mempool_alloc_t *alloc_fn,
a91a5ac6
TH
73 mempool_free_t *free_fn, void *pool_data,
74 gfp_t gfp_mask, int node_id)
1946089a
CL
75{
76 mempool_t *pool;
7b5219db 77 pool = kzalloc_node(sizeof(*pool), gfp_mask, node_id);
1da177e4
LT
78 if (!pool)
79 return NULL;
1946089a 80 pool->elements = kmalloc_node(min_nr * sizeof(void *),
a91a5ac6 81 gfp_mask, node_id);
1da177e4
LT
82 if (!pool->elements) {
83 kfree(pool);
84 return NULL;
85 }
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;
91 pool->free = free_fn;
92
93 /*
94 * First pre-allocate the guaranteed number of buffers.
95 */
96 while (pool->curr_nr < pool->min_nr) {
97 void *element;
98
a91a5ac6 99 element = pool->alloc(gfp_mask, pool->pool_data);
1da177e4 100 if (unlikely(!element)) {
0565d317 101 mempool_destroy(pool);
1da177e4
LT
102 return NULL;
103 }
104 add_element(pool, element);
105 }
106 return pool;
107}
1946089a 108EXPORT_SYMBOL(mempool_create_node);
1da177e4
LT
109
110/**
111 * mempool_resize - resize an existing memory pool
112 * @pool: pointer to the memory pool which was allocated via
113 * mempool_create().
114 * @new_min_nr: the new minimum number of elements guaranteed to be
115 * allocated for this pool.
116 * @gfp_mask: the usual allocation bitmask.
117 *
118 * This function shrinks/grows the pool. In the case of growing,
119 * it cannot be guaranteed that the pool will be grown to the new
120 * size immediately, but new mempool_free() calls will refill it.
121 *
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.
125 */
dd0fc66f 126int mempool_resize(mempool_t *pool, int new_min_nr, gfp_t gfp_mask)
1da177e4
LT
127{
128 void *element;
129 void **new_elements;
130 unsigned long flags;
131
132 BUG_ON(new_min_nr <= 0);
133
134 spin_lock_irqsave(&pool->lock, flags);
135 if (new_min_nr <= pool->min_nr) {
136 while (new_min_nr < pool->curr_nr) {
137 element = remove_element(pool);
138 spin_unlock_irqrestore(&pool->lock, flags);
139 pool->free(element, pool->pool_data);
140 spin_lock_irqsave(&pool->lock, flags);
141 }
142 pool->min_nr = new_min_nr;
143 goto out_unlock;
144 }
145 spin_unlock_irqrestore(&pool->lock, flags);
146
147 /* Grow the pool */
148 new_elements = kmalloc(new_min_nr * sizeof(*new_elements), gfp_mask);
149 if (!new_elements)
150 return -ENOMEM;
151
152 spin_lock_irqsave(&pool->lock, flags);
153 if (unlikely(new_min_nr <= pool->min_nr)) {
154 /* Raced, other resize will do our work */
155 spin_unlock_irqrestore(&pool->lock, flags);
156 kfree(new_elements);
157 goto out;
158 }
159 memcpy(new_elements, pool->elements,
160 pool->curr_nr * sizeof(*new_elements));
161 kfree(pool->elements);
162 pool->elements = new_elements;
163 pool->min_nr = new_min_nr;
164
165 while (pool->curr_nr < pool->min_nr) {
166 spin_unlock_irqrestore(&pool->lock, flags);
167 element = pool->alloc(gfp_mask, pool->pool_data);
168 if (!element)
169 goto out;
170 spin_lock_irqsave(&pool->lock, flags);
171 if (pool->curr_nr < pool->min_nr) {
172 add_element(pool, element);
173 } else {
174 spin_unlock_irqrestore(&pool->lock, flags);
175 pool->free(element, pool->pool_data); /* Raced */
176 goto out;
177 }
178 }
179out_unlock:
180 spin_unlock_irqrestore(&pool->lock, flags);
181out:
182 return 0;
183}
184EXPORT_SYMBOL(mempool_resize);
185
1da177e4
LT
186/**
187 * mempool_alloc - allocate an element from a specific memory pool
188 * @pool: pointer to the memory pool which was allocated via
189 * mempool_create().
190 * @gfp_mask: the usual allocation bitmask.
191 *
72fd4a35 192 * this function only sleeps if the alloc_fn() function sleeps or
1da177e4
LT
193 * returns NULL. Note that due to preallocation, this function
194 * *never* fails when called from process contexts. (it might
195 * fail if called from an IRQ context.)
8bf8fcb0 196 * Note: using __GFP_ZERO is not supported.
1da177e4 197 */
dd0fc66f 198void * mempool_alloc(mempool_t *pool, gfp_t gfp_mask)
1da177e4
LT
199{
200 void *element;
201 unsigned long flags;
01890a4c 202 wait_queue_t wait;
6daa0e28 203 gfp_t gfp_temp;
20a77776 204
8bf8fcb0 205 VM_WARN_ON_ONCE(gfp_mask & __GFP_ZERO);
20a77776 206 might_sleep_if(gfp_mask & __GFP_WAIT);
b84a35be
NP
207
208 gfp_mask |= __GFP_NOMEMALLOC; /* don't allocate emergency reserves */
209 gfp_mask |= __GFP_NORETRY; /* don't loop in __alloc_pages */
210 gfp_mask |= __GFP_NOWARN; /* failures are OK */
1da177e4 211
20a77776
NP
212 gfp_temp = gfp_mask & ~(__GFP_WAIT|__GFP_IO);
213
1da177e4 214repeat_alloc:
20a77776
NP
215
216 element = pool->alloc(gfp_temp, pool->pool_data);
1da177e4
LT
217 if (likely(element != NULL))
218 return element;
219
1da177e4
LT
220 spin_lock_irqsave(&pool->lock, flags);
221 if (likely(pool->curr_nr)) {
222 element = remove_element(pool);
223 spin_unlock_irqrestore(&pool->lock, flags);
5b990546
TH
224 /* paired with rmb in mempool_free(), read comment there */
225 smp_wmb();
17411962
CM
226 /*
227 * Update the allocation stack trace as this is more useful
228 * for debugging.
229 */
230 kmemleak_update_trace(element);
1da177e4
LT
231 return element;
232 }
1da177e4 233
1ebb7044
TH
234 /*
235 * We use gfp mask w/o __GFP_WAIT or IO for the first round. If
236 * alloc failed with that and @pool was empty, retry immediately.
237 */
238 if (gfp_temp != gfp_mask) {
239 spin_unlock_irqrestore(&pool->lock, flags);
240 gfp_temp = gfp_mask;
241 goto repeat_alloc;
242 }
243
244 /* We must not sleep if !__GFP_WAIT */
5b990546
TH
245 if (!(gfp_mask & __GFP_WAIT)) {
246 spin_unlock_irqrestore(&pool->lock, flags);
1da177e4 247 return NULL;
5b990546 248 }
1da177e4 249
5b990546 250 /* Let's wait for someone else to return an element to @pool */
01890a4c 251 init_wait(&wait);
1da177e4 252 prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE);
1da177e4 253
5b990546
TH
254 spin_unlock_irqrestore(&pool->lock, flags);
255
256 /*
257 * FIXME: this should be io_schedule(). The timeout is there as a
258 * workaround for some DM problems in 2.6.18.
259 */
260 io_schedule_timeout(5*HZ);
261
262 finish_wait(&pool->wait, &wait);
1da177e4
LT
263 goto repeat_alloc;
264}
265EXPORT_SYMBOL(mempool_alloc);
266
267/**
268 * mempool_free - return an element to the pool.
269 * @element: pool element pointer.
270 * @pool: pointer to the memory pool which was allocated via
271 * mempool_create().
272 *
273 * this function only sleeps if the free_fn() function sleeps.
274 */
275void mempool_free(void *element, mempool_t *pool)
276{
277 unsigned long flags;
278
c80e7a82
RR
279 if (unlikely(element == NULL))
280 return;
281
5b990546
TH
282 /*
283 * Paired with the wmb in mempool_alloc(). The preceding read is
284 * for @element and the following @pool->curr_nr. This ensures
285 * that the visible value of @pool->curr_nr is from after the
286 * allocation of @element. This is necessary for fringe cases
287 * where @element was passed to this task without going through
288 * barriers.
289 *
290 * For example, assume @p is %NULL at the beginning and one task
291 * performs "p = mempool_alloc(...);" while another task is doing
292 * "while (!p) cpu_relax(); mempool_free(p, ...);". This function
293 * may end up using curr_nr value which is from before allocation
294 * of @p without the following rmb.
295 */
296 smp_rmb();
297
298 /*
299 * For correctness, we need a test which is guaranteed to trigger
300 * if curr_nr + #allocated == min_nr. Testing curr_nr < min_nr
301 * without locking achieves that and refilling as soon as possible
302 * is desirable.
303 *
304 * Because curr_nr visible here is always a value after the
305 * allocation of @element, any task which decremented curr_nr below
306 * min_nr is guaranteed to see curr_nr < min_nr unless curr_nr gets
307 * incremented to min_nr afterwards. If curr_nr gets incremented
308 * to min_nr after the allocation of @element, the elements
309 * allocated after that are subject to the same guarantee.
310 *
311 * Waiters happen iff curr_nr is 0 and the above guarantee also
312 * ensures that there will be frees which return elements to the
313 * pool waking up the waiters.
314 */
eb9a3c62 315 if (unlikely(pool->curr_nr < pool->min_nr)) {
1da177e4 316 spin_lock_irqsave(&pool->lock, flags);
eb9a3c62 317 if (likely(pool->curr_nr < pool->min_nr)) {
1da177e4
LT
318 add_element(pool, element);
319 spin_unlock_irqrestore(&pool->lock, flags);
320 wake_up(&pool->wait);
321 return;
322 }
323 spin_unlock_irqrestore(&pool->lock, flags);
324 }
325 pool->free(element, pool->pool_data);
326}
327EXPORT_SYMBOL(mempool_free);
328
329/*
330 * A commonly used alloc and free fn.
331 */
dd0fc66f 332void *mempool_alloc_slab(gfp_t gfp_mask, void *pool_data)
1da177e4 333{
fcc234f8 334 struct kmem_cache *mem = pool_data;
1da177e4
LT
335 return kmem_cache_alloc(mem, gfp_mask);
336}
337EXPORT_SYMBOL(mempool_alloc_slab);
338
339void mempool_free_slab(void *element, void *pool_data)
340{
fcc234f8 341 struct kmem_cache *mem = pool_data;
1da177e4
LT
342 kmem_cache_free(mem, element);
343}
344EXPORT_SYMBOL(mempool_free_slab);
6e0678f3 345
53184082
MD
346/*
347 * A commonly used alloc and free fn that kmalloc/kfrees the amount of memory
183ff22b 348 * specified by pool_data
53184082
MD
349 */
350void *mempool_kmalloc(gfp_t gfp_mask, void *pool_data)
351{
5e2f89b5 352 size_t size = (size_t)pool_data;
53184082
MD
353 return kmalloc(size, gfp_mask);
354}
355EXPORT_SYMBOL(mempool_kmalloc);
356
357void mempool_kfree(void *element, void *pool_data)
358{
359 kfree(element);
360}
361EXPORT_SYMBOL(mempool_kfree);
362
6e0678f3
MD
363/*
364 * A simple mempool-backed page allocator that allocates pages
365 * of the order specified by pool_data.
366 */
367void *mempool_alloc_pages(gfp_t gfp_mask, void *pool_data)
368{
369 int order = (int)(long)pool_data;
370 return alloc_pages(gfp_mask, order);
371}
372EXPORT_SYMBOL(mempool_alloc_pages);
373
374void mempool_free_pages(void *element, void *pool_data)
375{
376 int order = (int)(long)pool_data;
377 __free_pages(element, order);
378}
379EXPORT_SYMBOL(mempool_free_pages);