mempool.c 10.7 KB
Newer Older
Linus Torvalds's avatar
Linus Torvalds committed
1
2
3
4
5
6
7
8
9
10
11
12
/*
 *  linux/mm/mempool.c
 *
 *  memory buffer pool support. Such pools are mostly used
 *  for guaranteed, deadlock-free memory allocations during
 *  extreme VM load.
 *
 *  started by Ingo Molnar, Copyright (C) 2001
 */

#include <linux/mm.h>
#include <linux/slab.h>
13
#include <linux/kmemleak.h>
14
#include <linux/export.h>
Linus Torvalds's avatar
Linus Torvalds committed
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
#include <linux/mempool.h>
#include <linux/blkdev.h>
#include <linux/writeback.h>

static void add_element(mempool_t *pool, void *element)
{
	BUG_ON(pool->curr_nr >= pool->min_nr);
	pool->elements[pool->curr_nr++] = element;
}

static void *remove_element(mempool_t *pool)
{
	BUG_ON(pool->curr_nr <= 0);
	return pool->elements[--pool->curr_nr];
}

31
32
33
34
35
36
37
38
39
/**
 * mempool_destroy - deallocate a memory pool
 * @pool:      pointer to the memory pool which was allocated via
 *             mempool_create().
 *
 * Free all reserved elements in @pool and @pool itself.  This function
 * only sleeps if the free_fn() function sleeps.
 */
void mempool_destroy(mempool_t *pool)
Linus Torvalds's avatar
Linus Torvalds committed
40
41
42
43
44
45
46
47
{
	while (pool->curr_nr) {
		void *element = remove_element(pool);
		pool->free(element, pool->pool_data);
	}
	kfree(pool->elements);
	kfree(pool);
}
48
EXPORT_SYMBOL(mempool_destroy);
Linus Torvalds's avatar
Linus Torvalds committed
49
50
51
52
53
54
55
56
57
58

/**
 * mempool_create - create a memory pool
 * @min_nr:    the minimum number of elements guaranteed to be
 *             allocated for this pool.
 * @alloc_fn:  user-defined element-allocation function.
 * @free_fn:   user-defined element-freeing function.
 * @pool_data: optional private data available to the user-defined functions.
 *
 * this function creates and allocates a guaranteed size, preallocated
59
 * memory pool. The pool can be used from the mempool_alloc() and mempool_free()
Linus Torvalds's avatar
Linus Torvalds committed
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
Linus Torvalds's avatar
Linus Torvalds committed
62
63
 * from IRQ contexts.
 */
64
mempool_t *mempool_create(int min_nr, mempool_alloc_t *alloc_fn,
Linus Torvalds's avatar
Linus Torvalds committed
65
66
				mempool_free_t *free_fn, void *pool_data)
{
67
68
	return mempool_create_node(min_nr,alloc_fn,free_fn, pool_data,
				   GFP_KERNEL, NUMA_NO_NODE);
69
70
}
EXPORT_SYMBOL(mempool_create);
Linus Torvalds's avatar
Linus Torvalds committed
71

72
mempool_t *mempool_create_node(int min_nr, mempool_alloc_t *alloc_fn,
73
74
			       mempool_free_t *free_fn, void *pool_data,
			       gfp_t gfp_mask, int node_id)
75
76
{
	mempool_t *pool;
77
	pool = kzalloc_node(sizeof(*pool), gfp_mask, node_id);
Linus Torvalds's avatar
Linus Torvalds committed
78
79
	if (!pool)
		return NULL;
80
	pool->elements = kmalloc_node(min_nr * sizeof(void *),
81
				      gfp_mask, node_id);
Linus Torvalds's avatar
Linus Torvalds committed
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
	if (!pool->elements) {
		kfree(pool);
		return NULL;
	}
	spin_lock_init(&pool->lock);
	pool->min_nr = min_nr;
	pool->pool_data = pool_data;
	init_waitqueue_head(&pool->wait);
	pool->alloc = alloc_fn;
	pool->free = free_fn;

	/*
	 * First pre-allocate the guaranteed number of buffers.
	 */
	while (pool->curr_nr < pool->min_nr) {
		void *element;

99
		element = pool->alloc(gfp_mask, pool->pool_data);
Linus Torvalds's avatar
Linus Torvalds committed
100
		if (unlikely(!element)) {
101
			mempool_destroy(pool);
Linus Torvalds's avatar
Linus Torvalds committed
102
103
104
105
106
107
			return NULL;
		}
		add_element(pool, element);
	}
	return pool;
}
108
EXPORT_SYMBOL(mempool_create_node);
Linus Torvalds's avatar
Linus Torvalds committed
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125

/**
 * mempool_resize - resize an existing memory pool
 * @pool:       pointer to the memory pool which was allocated via
 *              mempool_create().
 * @new_min_nr: the new minimum number of elements guaranteed to be
 *              allocated for this pool.
 * @gfp_mask:   the usual allocation bitmask.
 *
 * This function shrinks/grows the pool. In the case of growing,
 * it cannot be guaranteed that the pool will be grown to the new
 * size immediately, but new mempool_free() calls will refill it.
 *
 * Note, the caller must guarantee that no mempool_destroy is called
 * while this function is running. mempool_alloc() & mempool_free()
 * might be called (eg. from IRQ contexts) while this function executes.
 */
126
int mempool_resize(mempool_t *pool, int new_min_nr, gfp_t gfp_mask)
Linus Torvalds's avatar
Linus Torvalds committed
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
{
	void *element;
	void **new_elements;
	unsigned long flags;

	BUG_ON(new_min_nr <= 0);

	spin_lock_irqsave(&pool->lock, flags);
	if (new_min_nr <= pool->min_nr) {
		while (new_min_nr < pool->curr_nr) {
			element = remove_element(pool);
			spin_unlock_irqrestore(&pool->lock, flags);
			pool->free(element, pool->pool_data);
			spin_lock_irqsave(&pool->lock, flags);
		}
		pool->min_nr = new_min_nr;
		goto out_unlock;
	}
	spin_unlock_irqrestore(&pool->lock, flags);

	/* Grow the pool */
	new_elements = kmalloc(new_min_nr * sizeof(*new_elements), gfp_mask);
	if (!new_elements)
		return -ENOMEM;

	spin_lock_irqsave(&pool->lock, flags);
	if (unlikely(new_min_nr <= pool->min_nr)) {
		/* Raced, other resize will do our work */
		spin_unlock_irqrestore(&pool->lock, flags);
		kfree(new_elements);
		goto out;
	}
	memcpy(new_elements, pool->elements,
			pool->curr_nr * sizeof(*new_elements));
	kfree(pool->elements);
	pool->elements = new_elements;
	pool->min_nr = new_min_nr;

	while (pool->curr_nr < pool->min_nr) {
		spin_unlock_irqrestore(&pool->lock, flags);
		element = pool->alloc(gfp_mask, pool->pool_data);
		if (!element)
			goto out;
		spin_lock_irqsave(&pool->lock, flags);
		if (pool->curr_nr < pool->min_nr) {
			add_element(pool, element);
		} else {
			spin_unlock_irqrestore(&pool->lock, flags);
			pool->free(element, pool->pool_data);	/* Raced */
			goto out;
		}
	}
out_unlock:
	spin_unlock_irqrestore(&pool->lock, flags);
out:
	return 0;
}
EXPORT_SYMBOL(mempool_resize);

/**
 * mempool_alloc - allocate an element from a specific memory pool
 * @pool:      pointer to the memory pool which was allocated via
 *             mempool_create().
 * @gfp_mask:  the usual allocation bitmask.
 *
192
 * this function only sleeps if the alloc_fn() function sleeps or
Linus Torvalds's avatar
Linus Torvalds committed
193
194
195
 * returns NULL. Note that due to preallocation, this function
 * *never* fails when called from process contexts. (it might
 * fail if called from an IRQ context.)
196
 * Note: using __GFP_ZERO is not supported.
Linus Torvalds's avatar
Linus Torvalds committed
197
 */
198
void * mempool_alloc(mempool_t *pool, gfp_t gfp_mask)
Linus Torvalds's avatar
Linus Torvalds committed
199
200
201
{
	void *element;
	unsigned long flags;
202
	wait_queue_t wait;
Al Viro's avatar
Al Viro committed
203
	gfp_t gfp_temp;
Nick Piggin's avatar
Nick Piggin committed
204

205
	VM_WARN_ON_ONCE(gfp_mask & __GFP_ZERO);
Nick Piggin's avatar
Nick Piggin committed
206
	might_sleep_if(gfp_mask & __GFP_WAIT);
207
208
209
210

	gfp_mask |= __GFP_NOMEMALLOC;	/* don't allocate emergency reserves */
	gfp_mask |= __GFP_NORETRY;	/* don't loop in __alloc_pages */
	gfp_mask |= __GFP_NOWARN;	/* failures are OK */
Linus Torvalds's avatar
Linus Torvalds committed
211

Nick Piggin's avatar
Nick Piggin committed
212
213
	gfp_temp = gfp_mask & ~(__GFP_WAIT|__GFP_IO);

Linus Torvalds's avatar
Linus Torvalds committed
214
repeat_alloc:
Nick Piggin's avatar
Nick Piggin committed
215
216

	element = pool->alloc(gfp_temp, pool->pool_data);
Linus Torvalds's avatar
Linus Torvalds committed
217
218
219
220
221
222
223
	if (likely(element != NULL))
		return element;

	spin_lock_irqsave(&pool->lock, flags);
	if (likely(pool->curr_nr)) {
		element = remove_element(pool);
		spin_unlock_irqrestore(&pool->lock, flags);
224
225
		/* paired with rmb in mempool_free(), read comment there */
		smp_wmb();
226
227
228
229
230
		/*
		 * Update the allocation stack trace as this is more useful
		 * for debugging.
		 */
		kmemleak_update_trace(element);
Linus Torvalds's avatar
Linus Torvalds committed
231
232
233
		return element;
	}

234
235
236
237
238
239
240
241
242
243
244
	/*
	 * We use gfp mask w/o __GFP_WAIT or IO for the first round.  If
	 * alloc failed with that and @pool was empty, retry immediately.
	 */
	if (gfp_temp != gfp_mask) {
		spin_unlock_irqrestore(&pool->lock, flags);
		gfp_temp = gfp_mask;
		goto repeat_alloc;
	}

	/* We must not sleep if !__GFP_WAIT */
245
246
	if (!(gfp_mask & __GFP_WAIT)) {
		spin_unlock_irqrestore(&pool->lock, flags);
Linus Torvalds's avatar
Linus Torvalds committed
247
		return NULL;
248
	}
Linus Torvalds's avatar
Linus Torvalds committed
249

250
	/* Let's wait for someone else to return an element to @pool */
251
	init_wait(&wait);
Linus Torvalds's avatar
Linus Torvalds committed
252
253
	prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE);

254
255
256
257
258
259
260
261
262
	spin_unlock_irqrestore(&pool->lock, flags);

	/*
	 * FIXME: this should be io_schedule().  The timeout is there as a
	 * workaround for some DM problems in 2.6.18.
	 */
	io_schedule_timeout(5*HZ);

	finish_wait(&pool->wait, &wait);
Linus Torvalds's avatar
Linus Torvalds committed
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
	goto repeat_alloc;
}
EXPORT_SYMBOL(mempool_alloc);

/**
 * mempool_free - return an element to the pool.
 * @element:   pool element pointer.
 * @pool:      pointer to the memory pool which was allocated via
 *             mempool_create().
 *
 * this function only sleeps if the free_fn() function sleeps.
 */
void mempool_free(void *element, mempool_t *pool)
{
	unsigned long flags;

Rusty Russell's avatar
Rusty Russell committed
279
280
281
	if (unlikely(element == NULL))
		return;

282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
	/*
	 * Paired with the wmb in mempool_alloc().  The preceding read is
	 * for @element and the following @pool->curr_nr.  This ensures
	 * that the visible value of @pool->curr_nr is from after the
	 * allocation of @element.  This is necessary for fringe cases
	 * where @element was passed to this task without going through
	 * barriers.
	 *
	 * For example, assume @p is %NULL at the beginning and one task
	 * performs "p = mempool_alloc(...);" while another task is doing
	 * "while (!p) cpu_relax(); mempool_free(p, ...);".  This function
	 * may end up using curr_nr value which is from before allocation
	 * of @p without the following rmb.
	 */
	smp_rmb();

	/*
	 * For correctness, we need a test which is guaranteed to trigger
	 * if curr_nr + #allocated == min_nr.  Testing curr_nr < min_nr
	 * without locking achieves that and refilling as soon as possible
	 * is desirable.
	 *
	 * Because curr_nr visible here is always a value after the
	 * allocation of @element, any task which decremented curr_nr below
	 * min_nr is guaranteed to see curr_nr < min_nr unless curr_nr gets
	 * incremented to min_nr afterwards.  If curr_nr gets incremented
	 * to min_nr after the allocation of @element, the elements
	 * allocated after that are subject to the same guarantee.
	 *
	 * Waiters happen iff curr_nr is 0 and the above guarantee also
	 * ensures that there will be frees which return elements to the
	 * pool waking up the waiters.
	 */
315
	if (unlikely(pool->curr_nr < pool->min_nr)) {
Linus Torvalds's avatar
Linus Torvalds committed
316
		spin_lock_irqsave(&pool->lock, flags);
317
		if (likely(pool->curr_nr < pool->min_nr)) {
Linus Torvalds's avatar
Linus Torvalds committed
318
319
320
321
322
323
324
325
326
327
328
329
330
331
			add_element(pool, element);
			spin_unlock_irqrestore(&pool->lock, flags);
			wake_up(&pool->wait);
			return;
		}
		spin_unlock_irqrestore(&pool->lock, flags);
	}
	pool->free(element, pool->pool_data);
}
EXPORT_SYMBOL(mempool_free);

/*
 * A commonly used alloc and free fn.
 */
332
void *mempool_alloc_slab(gfp_t gfp_mask, void *pool_data)
Linus Torvalds's avatar
Linus Torvalds committed
333
{
334
	struct kmem_cache *mem = pool_data;
Linus Torvalds's avatar
Linus Torvalds committed
335
336
337
338
339
340
	return kmem_cache_alloc(mem, gfp_mask);
}
EXPORT_SYMBOL(mempool_alloc_slab);

void mempool_free_slab(void *element, void *pool_data)
{
341
	struct kmem_cache *mem = pool_data;
Linus Torvalds's avatar
Linus Torvalds committed
342
343
344
	kmem_cache_free(mem, element);
}
EXPORT_SYMBOL(mempool_free_slab);
345

346
347
/*
 * A commonly used alloc and free fn that kmalloc/kfrees the amount of memory
Simon Arlott's avatar
Simon Arlott committed
348
 * specified by pool_data
349
350
351
 */
void *mempool_kmalloc(gfp_t gfp_mask, void *pool_data)
{
Figo.zhang's avatar
Figo.zhang committed
352
	size_t size = (size_t)pool_data;
353
354
355
356
357
358
359
360
361
362
	return kmalloc(size, gfp_mask);
}
EXPORT_SYMBOL(mempool_kmalloc);

void mempool_kfree(void *element, void *pool_data)
{
	kfree(element);
}
EXPORT_SYMBOL(mempool_kfree);

363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
/*
 * A simple mempool-backed page allocator that allocates pages
 * of the order specified by pool_data.
 */
void *mempool_alloc_pages(gfp_t gfp_mask, void *pool_data)
{
	int order = (int)(long)pool_data;
	return alloc_pages(gfp_mask, order);
}
EXPORT_SYMBOL(mempool_alloc_pages);

void mempool_free_pages(void *element, void *pool_data)
{
	int order = (int)(long)pool_data;
	__free_pages(element, order);
}
EXPORT_SYMBOL(mempool_free_pages);