xref: /openbmc/linux/mm/mempool.c (revision 9cdb81c7)
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,-1);
67 }
68 EXPORT_SYMBOL(mempool_create);
69 
70 mempool_t *mempool_create_node(int min_nr, mempool_alloc_t *alloc_fn,
71 			mempool_free_t *free_fn, void *pool_data, int node_id)
72 {
73 	mempool_t *pool;
74 	pool = kmalloc_node(sizeof(*pool), GFP_KERNEL | __GFP_ZERO, node_id);
75 	if (!pool)
76 		return NULL;
77 	pool->elements = kmalloc_node(min_nr * sizeof(void *),
78 					GFP_KERNEL, node_id);
79 	if (!pool->elements) {
80 		kfree(pool);
81 		return NULL;
82 	}
83 	spin_lock_init(&pool->lock);
84 	pool->min_nr = min_nr;
85 	pool->pool_data = pool_data;
86 	init_waitqueue_head(&pool->wait);
87 	pool->alloc = alloc_fn;
88 	pool->free = free_fn;
89 
90 	/*
91 	 * First pre-allocate the guaranteed number of buffers.
92 	 */
93 	while (pool->curr_nr < pool->min_nr) {
94 		void *element;
95 
96 		element = pool->alloc(GFP_KERNEL, pool->pool_data);
97 		if (unlikely(!element)) {
98 			mempool_destroy(pool);
99 			return NULL;
100 		}
101 		add_element(pool, element);
102 	}
103 	return pool;
104 }
105 EXPORT_SYMBOL(mempool_create_node);
106 
107 /**
108  * mempool_resize - resize an existing memory pool
109  * @pool:       pointer to the memory pool which was allocated via
110  *              mempool_create().
111  * @new_min_nr: the new minimum number of elements guaranteed to be
112  *              allocated for this pool.
113  * @gfp_mask:   the usual allocation bitmask.
114  *
115  * This function shrinks/grows the pool. In the case of growing,
116  * it cannot be guaranteed that the pool will be grown to the new
117  * size immediately, but new mempool_free() calls will refill it.
118  *
119  * Note, the caller must guarantee that no mempool_destroy is called
120  * while this function is running. mempool_alloc() & mempool_free()
121  * might be called (eg. from IRQ contexts) while this function executes.
122  */
123 int mempool_resize(mempool_t *pool, int new_min_nr, gfp_t gfp_mask)
124 {
125 	void *element;
126 	void **new_elements;
127 	unsigned long flags;
128 
129 	BUG_ON(new_min_nr <= 0);
130 
131 	spin_lock_irqsave(&pool->lock, flags);
132 	if (new_min_nr <= pool->min_nr) {
133 		while (new_min_nr < pool->curr_nr) {
134 			element = remove_element(pool);
135 			spin_unlock_irqrestore(&pool->lock, flags);
136 			pool->free(element, pool->pool_data);
137 			spin_lock_irqsave(&pool->lock, flags);
138 		}
139 		pool->min_nr = new_min_nr;
140 		goto out_unlock;
141 	}
142 	spin_unlock_irqrestore(&pool->lock, flags);
143 
144 	/* Grow the pool */
145 	new_elements = kmalloc(new_min_nr * sizeof(*new_elements), gfp_mask);
146 	if (!new_elements)
147 		return -ENOMEM;
148 
149 	spin_lock_irqsave(&pool->lock, flags);
150 	if (unlikely(new_min_nr <= pool->min_nr)) {
151 		/* Raced, other resize will do our work */
152 		spin_unlock_irqrestore(&pool->lock, flags);
153 		kfree(new_elements);
154 		goto out;
155 	}
156 	memcpy(new_elements, pool->elements,
157 			pool->curr_nr * sizeof(*new_elements));
158 	kfree(pool->elements);
159 	pool->elements = new_elements;
160 	pool->min_nr = new_min_nr;
161 
162 	while (pool->curr_nr < pool->min_nr) {
163 		spin_unlock_irqrestore(&pool->lock, flags);
164 		element = pool->alloc(gfp_mask, pool->pool_data);
165 		if (!element)
166 			goto out;
167 		spin_lock_irqsave(&pool->lock, flags);
168 		if (pool->curr_nr < pool->min_nr) {
169 			add_element(pool, element);
170 		} else {
171 			spin_unlock_irqrestore(&pool->lock, flags);
172 			pool->free(element, pool->pool_data);	/* Raced */
173 			goto out;
174 		}
175 	}
176 out_unlock:
177 	spin_unlock_irqrestore(&pool->lock, flags);
178 out:
179 	return 0;
180 }
181 EXPORT_SYMBOL(mempool_resize);
182 
183 /**
184  * mempool_alloc - allocate an element from a specific memory pool
185  * @pool:      pointer to the memory pool which was allocated via
186  *             mempool_create().
187  * @gfp_mask:  the usual allocation bitmask.
188  *
189  * this function only sleeps if the alloc_fn() function sleeps or
190  * returns NULL. Note that due to preallocation, this function
191  * *never* fails when called from process contexts. (it might
192  * fail if called from an IRQ context.)
193  */
194 void * mempool_alloc(mempool_t *pool, gfp_t gfp_mask)
195 {
196 	void *element;
197 	unsigned long flags;
198 	wait_queue_t wait;
199 	gfp_t gfp_temp;
200 
201 	might_sleep_if(gfp_mask & __GFP_WAIT);
202 
203 	gfp_mask |= __GFP_NOMEMALLOC;	/* don't allocate emergency reserves */
204 	gfp_mask |= __GFP_NORETRY;	/* don't loop in __alloc_pages */
205 	gfp_mask |= __GFP_NOWARN;	/* failures are OK */
206 
207 	gfp_temp = gfp_mask & ~(__GFP_WAIT|__GFP_IO);
208 
209 repeat_alloc:
210 
211 	element = pool->alloc(gfp_temp, pool->pool_data);
212 	if (likely(element != NULL))
213 		return element;
214 
215 	spin_lock_irqsave(&pool->lock, flags);
216 	if (likely(pool->curr_nr)) {
217 		element = remove_element(pool);
218 		spin_unlock_irqrestore(&pool->lock, flags);
219 		/* paired with rmb in mempool_free(), read comment there */
220 		smp_wmb();
221 		return element;
222 	}
223 
224 	/*
225 	 * We use gfp mask w/o __GFP_WAIT or IO for the first round.  If
226 	 * alloc failed with that and @pool was empty, retry immediately.
227 	 */
228 	if (gfp_temp != gfp_mask) {
229 		spin_unlock_irqrestore(&pool->lock, flags);
230 		gfp_temp = gfp_mask;
231 		goto repeat_alloc;
232 	}
233 
234 	/* We must not sleep if !__GFP_WAIT */
235 	if (!(gfp_mask & __GFP_WAIT)) {
236 		spin_unlock_irqrestore(&pool->lock, flags);
237 		return NULL;
238 	}
239 
240 	/* Let's wait for someone else to return an element to @pool */
241 	init_wait(&wait);
242 	prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE);
243 
244 	spin_unlock_irqrestore(&pool->lock, flags);
245 
246 	/*
247 	 * FIXME: this should be io_schedule().  The timeout is there as a
248 	 * workaround for some DM problems in 2.6.18.
249 	 */
250 	io_schedule_timeout(5*HZ);
251 
252 	finish_wait(&pool->wait, &wait);
253 	goto repeat_alloc;
254 }
255 EXPORT_SYMBOL(mempool_alloc);
256 
257 /**
258  * mempool_free - return an element to the pool.
259  * @element:   pool element pointer.
260  * @pool:      pointer to the memory pool which was allocated via
261  *             mempool_create().
262  *
263  * this function only sleeps if the free_fn() function sleeps.
264  */
265 void mempool_free(void *element, mempool_t *pool)
266 {
267 	unsigned long flags;
268 
269 	if (unlikely(element == NULL))
270 		return;
271 
272 	/*
273 	 * Paired with the wmb in mempool_alloc().  The preceding read is
274 	 * for @element and the following @pool->curr_nr.  This ensures
275 	 * that the visible value of @pool->curr_nr is from after the
276 	 * allocation of @element.  This is necessary for fringe cases
277 	 * where @element was passed to this task without going through
278 	 * barriers.
279 	 *
280 	 * For example, assume @p is %NULL at the beginning and one task
281 	 * performs "p = mempool_alloc(...);" while another task is doing
282 	 * "while (!p) cpu_relax(); mempool_free(p, ...);".  This function
283 	 * may end up using curr_nr value which is from before allocation
284 	 * of @p without the following rmb.
285 	 */
286 	smp_rmb();
287 
288 	/*
289 	 * For correctness, we need a test which is guaranteed to trigger
290 	 * if curr_nr + #allocated == min_nr.  Testing curr_nr < min_nr
291 	 * without locking achieves that and refilling as soon as possible
292 	 * is desirable.
293 	 *
294 	 * Because curr_nr visible here is always a value after the
295 	 * allocation of @element, any task which decremented curr_nr below
296 	 * min_nr is guaranteed to see curr_nr < min_nr unless curr_nr gets
297 	 * incremented to min_nr afterwards.  If curr_nr gets incremented
298 	 * to min_nr after the allocation of @element, the elements
299 	 * allocated after that are subject to the same guarantee.
300 	 *
301 	 * Waiters happen iff curr_nr is 0 and the above guarantee also
302 	 * ensures that there will be frees which return elements to the
303 	 * pool waking up the waiters.
304 	 */
305 	if (pool->curr_nr < pool->min_nr) {
306 		spin_lock_irqsave(&pool->lock, flags);
307 		if (pool->curr_nr < pool->min_nr) {
308 			add_element(pool, element);
309 			spin_unlock_irqrestore(&pool->lock, flags);
310 			wake_up(&pool->wait);
311 			return;
312 		}
313 		spin_unlock_irqrestore(&pool->lock, flags);
314 	}
315 	pool->free(element, pool->pool_data);
316 }
317 EXPORT_SYMBOL(mempool_free);
318 
319 /*
320  * A commonly used alloc and free fn.
321  */
322 void *mempool_alloc_slab(gfp_t gfp_mask, void *pool_data)
323 {
324 	struct kmem_cache *mem = pool_data;
325 	return kmem_cache_alloc(mem, gfp_mask);
326 }
327 EXPORT_SYMBOL(mempool_alloc_slab);
328 
329 void mempool_free_slab(void *element, void *pool_data)
330 {
331 	struct kmem_cache *mem = pool_data;
332 	kmem_cache_free(mem, element);
333 }
334 EXPORT_SYMBOL(mempool_free_slab);
335 
336 /*
337  * A commonly used alloc and free fn that kmalloc/kfrees the amount of memory
338  * specified by pool_data
339  */
340 void *mempool_kmalloc(gfp_t gfp_mask, void *pool_data)
341 {
342 	size_t size = (size_t)pool_data;
343 	return kmalloc(size, gfp_mask);
344 }
345 EXPORT_SYMBOL(mempool_kmalloc);
346 
347 void mempool_kfree(void *element, void *pool_data)
348 {
349 	kfree(element);
350 }
351 EXPORT_SYMBOL(mempool_kfree);
352 
353 /*
354  * A simple mempool-backed page allocator that allocates pages
355  * of the order specified by pool_data.
356  */
357 void *mempool_alloc_pages(gfp_t gfp_mask, void *pool_data)
358 {
359 	int order = (int)(long)pool_data;
360 	return alloc_pages(gfp_mask, order);
361 }
362 EXPORT_SYMBOL(mempool_alloc_pages);
363 
364 void mempool_free_pages(void *element, void *pool_data)
365 {
366 	int order = (int)(long)pool_data;
367 	__free_pages(element, order);
368 }
369 EXPORT_SYMBOL(mempool_free_pages);
370