xref: /openbmc/linux/mm/mempool.c (revision 1c2f87c2)
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/export.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 /**
31  * mempool_destroy - deallocate a memory pool
32  * @pool:      pointer to the memory pool which was allocated via
33  *             mempool_create().
34  *
35  * Free all reserved elements in @pool and @pool itself.  This function
36  * only sleeps if the free_fn() function sleeps.
37  */
38 void mempool_destroy(mempool_t *pool)
39 {
40 	while (pool->curr_nr) {
41 		void *element = remove_element(pool);
42 		pool->free(element, pool->pool_data);
43 	}
44 	kfree(pool->elements);
45 	kfree(pool);
46 }
47 EXPORT_SYMBOL(mempool_destroy);
48 
49 /**
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.
56  *
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
61  * from IRQ contexts.
62  */
63 mempool_t *mempool_create(int min_nr, mempool_alloc_t *alloc_fn,
64 				mempool_free_t *free_fn, void *pool_data)
65 {
66 	return mempool_create_node(min_nr,alloc_fn,free_fn, pool_data,
67 				   GFP_KERNEL, NUMA_NO_NODE);
68 }
69 EXPORT_SYMBOL(mempool_create);
70 
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)
74 {
75 	mempool_t *pool;
76 	pool = kzalloc_node(sizeof(*pool), gfp_mask, node_id);
77 	if (!pool)
78 		return NULL;
79 	pool->elements = kmalloc_node(min_nr * sizeof(void *),
80 				      gfp_mask, node_id);
81 	if (!pool->elements) {
82 		kfree(pool);
83 		return NULL;
84 	}
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;
90 	pool->free = free_fn;
91 
92 	/*
93 	 * First pre-allocate the guaranteed number of buffers.
94 	 */
95 	while (pool->curr_nr < pool->min_nr) {
96 		void *element;
97 
98 		element = pool->alloc(gfp_mask, pool->pool_data);
99 		if (unlikely(!element)) {
100 			mempool_destroy(pool);
101 			return NULL;
102 		}
103 		add_element(pool, element);
104 	}
105 	return pool;
106 }
107 EXPORT_SYMBOL(mempool_create_node);
108 
109 /**
110  * mempool_resize - resize an existing memory pool
111  * @pool:       pointer to the memory pool which was allocated via
112  *              mempool_create().
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.
116  *
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.
120  *
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.
124  */
125 int mempool_resize(mempool_t *pool, int new_min_nr, gfp_t gfp_mask)
126 {
127 	void *element;
128 	void **new_elements;
129 	unsigned long flags;
130 
131 	BUG_ON(new_min_nr <= 0);
132 
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);
140 		}
141 		pool->min_nr = new_min_nr;
142 		goto out_unlock;
143 	}
144 	spin_unlock_irqrestore(&pool->lock, flags);
145 
146 	/* Grow the pool */
147 	new_elements = kmalloc(new_min_nr * sizeof(*new_elements), gfp_mask);
148 	if (!new_elements)
149 		return -ENOMEM;
150 
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);
155 		kfree(new_elements);
156 		goto out;
157 	}
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;
163 
164 	while (pool->curr_nr < pool->min_nr) {
165 		spin_unlock_irqrestore(&pool->lock, flags);
166 		element = pool->alloc(gfp_mask, pool->pool_data);
167 		if (!element)
168 			goto out;
169 		spin_lock_irqsave(&pool->lock, flags);
170 		if (pool->curr_nr < pool->min_nr) {
171 			add_element(pool, element);
172 		} else {
173 			spin_unlock_irqrestore(&pool->lock, flags);
174 			pool->free(element, pool->pool_data);	/* Raced */
175 			goto out;
176 		}
177 	}
178 out_unlock:
179 	spin_unlock_irqrestore(&pool->lock, flags);
180 out:
181 	return 0;
182 }
183 EXPORT_SYMBOL(mempool_resize);
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, gfp_t gfp_mask)
197 {
198 	void *element;
199 	unsigned long flags;
200 	wait_queue_t wait;
201 	gfp_t 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 		/* paired with rmb in mempool_free(), read comment there */
222 		smp_wmb();
223 		return element;
224 	}
225 
226 	/*
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.
229 	 */
230 	if (gfp_temp != gfp_mask) {
231 		spin_unlock_irqrestore(&pool->lock, flags);
232 		gfp_temp = gfp_mask;
233 		goto repeat_alloc;
234 	}
235 
236 	/* We must not sleep if !__GFP_WAIT */
237 	if (!(gfp_mask & __GFP_WAIT)) {
238 		spin_unlock_irqrestore(&pool->lock, flags);
239 		return NULL;
240 	}
241 
242 	/* Let's wait for someone else to return an element to @pool */
243 	init_wait(&wait);
244 	prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE);
245 
246 	spin_unlock_irqrestore(&pool->lock, flags);
247 
248 	/*
249 	 * FIXME: this should be io_schedule().  The timeout is there as a
250 	 * workaround for some DM problems in 2.6.18.
251 	 */
252 	io_schedule_timeout(5*HZ);
253 
254 	finish_wait(&pool->wait, &wait);
255 	goto repeat_alloc;
256 }
257 EXPORT_SYMBOL(mempool_alloc);
258 
259 /**
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
263  *             mempool_create().
264  *
265  * this function only sleeps if the free_fn() function sleeps.
266  */
267 void mempool_free(void *element, mempool_t *pool)
268 {
269 	unsigned long flags;
270 
271 	if (unlikely(element == NULL))
272 		return;
273 
274 	/*
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
280 	 * barriers.
281 	 *
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.
287 	 */
288 	smp_rmb();
289 
290 	/*
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
294 	 * is desirable.
295 	 *
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.
302 	 *
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.
306 	 */
307 	if (unlikely(pool->curr_nr < pool->min_nr)) {
308 		spin_lock_irqsave(&pool->lock, flags);
309 		if (likely(pool->curr_nr < pool->min_nr)) {
310 			add_element(pool, element);
311 			spin_unlock_irqrestore(&pool->lock, flags);
312 			wake_up(&pool->wait);
313 			return;
314 		}
315 		spin_unlock_irqrestore(&pool->lock, flags);
316 	}
317 	pool->free(element, pool->pool_data);
318 }
319 EXPORT_SYMBOL(mempool_free);
320 
321 /*
322  * A commonly used alloc and free fn.
323  */
324 void *mempool_alloc_slab(gfp_t gfp_mask, void *pool_data)
325 {
326 	struct kmem_cache *mem = pool_data;
327 	return kmem_cache_alloc(mem, gfp_mask);
328 }
329 EXPORT_SYMBOL(mempool_alloc_slab);
330 
331 void mempool_free_slab(void *element, void *pool_data)
332 {
333 	struct kmem_cache *mem = pool_data;
334 	kmem_cache_free(mem, element);
335 }
336 EXPORT_SYMBOL(mempool_free_slab);
337 
338 /*
339  * A commonly used alloc and free fn that kmalloc/kfrees the amount of memory
340  * specified by pool_data
341  */
342 void *mempool_kmalloc(gfp_t gfp_mask, void *pool_data)
343 {
344 	size_t size = (size_t)pool_data;
345 	return kmalloc(size, gfp_mask);
346 }
347 EXPORT_SYMBOL(mempool_kmalloc);
348 
349 void mempool_kfree(void *element, void *pool_data)
350 {
351 	kfree(element);
352 }
353 EXPORT_SYMBOL(mempool_kfree);
354 
355 /*
356  * A simple mempool-backed page allocator that allocates pages
357  * of the order specified by pool_data.
358  */
359 void *mempool_alloc_pages(gfp_t gfp_mask, void *pool_data)
360 {
361 	int order = (int)(long)pool_data;
362 	return alloc_pages(gfp_mask, order);
363 }
364 EXPORT_SYMBOL(mempool_alloc_pages);
365 
366 void mempool_free_pages(void *element, void *pool_data)
367 {
368 	int order = (int)(long)pool_data;
369 	__free_pages(element, order);
370 }
371 EXPORT_SYMBOL(mempool_free_pages);
372