Root/mm/mempool.c

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
18static 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
24static void *remove_element(mempool_t *pool)
25{
26    BUG_ON(pool->curr_nr <= 0);
27    return pool->elements[--pool->curr_nr];
28}
29
30static 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 */
54mempool_t *mempool_create(int min_nr, mempool_alloc_t *alloc_fn,
55                mempool_free_t *free_fn, void *pool_data)
56{
57    return mempool_create_node(min_nr,alloc_fn,free_fn, pool_data,-1);
58}
59EXPORT_SYMBOL(mempool_create);
60
61mempool_t *mempool_create_node(int min_nr, mempool_alloc_t *alloc_fn,
62            mempool_free_t *free_fn, void *pool_data, int node_id)
63{
64    mempool_t *pool;
65    pool = kmalloc_node(sizeof(*pool), GFP_KERNEL | __GFP_ZERO, node_id);
66    if (!pool)
67        return NULL;
68    pool->elements = kmalloc_node(min_nr * sizeof(void *),
69                    GFP_KERNEL, node_id);
70    if (!pool->elements) {
71        kfree(pool);
72        return NULL;
73    }
74    spin_lock_init(&pool->lock);
75    pool->min_nr = min_nr;
76    pool->pool_data = pool_data;
77    init_waitqueue_head(&pool->wait);
78    pool->alloc = alloc_fn;
79    pool->free = free_fn;
80
81    /*
82     * First pre-allocate the guaranteed number of buffers.
83     */
84    while (pool->curr_nr < pool->min_nr) {
85        void *element;
86
87        element = pool->alloc(GFP_KERNEL, pool->pool_data);
88        if (unlikely(!element)) {
89            free_pool(pool);
90            return NULL;
91        }
92        add_element(pool, element);
93    }
94    return pool;
95}
96EXPORT_SYMBOL(mempool_create_node);
97
98/**
99 * mempool_resize - resize an existing memory pool
100 * @pool: pointer to the memory pool which was allocated via
101 * mempool_create().
102 * @new_min_nr: the new minimum number of elements guaranteed to be
103 * allocated for this pool.
104 * @gfp_mask: the usual allocation bitmask.
105 *
106 * This function shrinks/grows the pool. In the case of growing,
107 * it cannot be guaranteed that the pool will be grown to the new
108 * size immediately, but new mempool_free() calls will refill it.
109 *
110 * Note, the caller must guarantee that no mempool_destroy is called
111 * while this function is running. mempool_alloc() & mempool_free()
112 * might be called (eg. from IRQ contexts) while this function executes.
113 */
114int mempool_resize(mempool_t *pool, int new_min_nr, gfp_t gfp_mask)
115{
116    void *element;
117    void **new_elements;
118    unsigned long flags;
119
120    BUG_ON(new_min_nr <= 0);
121
122    spin_lock_irqsave(&pool->lock, flags);
123    if (new_min_nr <= pool->min_nr) {
124        while (new_min_nr < pool->curr_nr) {
125            element = remove_element(pool);
126            spin_unlock_irqrestore(&pool->lock, flags);
127            pool->free(element, pool->pool_data);
128            spin_lock_irqsave(&pool->lock, flags);
129        }
130        pool->min_nr = new_min_nr;
131        goto out_unlock;
132    }
133    spin_unlock_irqrestore(&pool->lock, flags);
134
135    /* Grow the pool */
136    new_elements = kmalloc(new_min_nr * sizeof(*new_elements), gfp_mask);
137    if (!new_elements)
138        return -ENOMEM;
139
140    spin_lock_irqsave(&pool->lock, flags);
141    if (unlikely(new_min_nr <= pool->min_nr)) {
142        /* Raced, other resize will do our work */
143        spin_unlock_irqrestore(&pool->lock, flags);
144        kfree(new_elements);
145        goto out;
146    }
147    memcpy(new_elements, pool->elements,
148            pool->curr_nr * sizeof(*new_elements));
149    kfree(pool->elements);
150    pool->elements = new_elements;
151    pool->min_nr = new_min_nr;
152
153    while (pool->curr_nr < pool->min_nr) {
154        spin_unlock_irqrestore(&pool->lock, flags);
155        element = pool->alloc(gfp_mask, pool->pool_data);
156        if (!element)
157            goto out;
158        spin_lock_irqsave(&pool->lock, flags);
159        if (pool->curr_nr < pool->min_nr) {
160            add_element(pool, element);
161        } else {
162            spin_unlock_irqrestore(&pool->lock, flags);
163            pool->free(element, pool->pool_data); /* Raced */
164            goto out;
165        }
166    }
167out_unlock:
168    spin_unlock_irqrestore(&pool->lock, flags);
169out:
170    return 0;
171}
172EXPORT_SYMBOL(mempool_resize);
173
174/**
175 * mempool_destroy - deallocate a memory pool
176 * @pool: pointer to the memory pool which was allocated via
177 * mempool_create().
178 *
179 * this function only sleeps if the free_fn() function sleeps. The caller
180 * has to guarantee that all elements have been returned to the pool (ie:
181 * freed) prior to calling mempool_destroy().
182 */
183void mempool_destroy(mempool_t *pool)
184{
185    /* Check for outstanding elements */
186    BUG_ON(pool->curr_nr != pool->min_nr);
187    free_pool(pool);
188}
189EXPORT_SYMBOL(mempool_destroy);
190
191/**
192 * mempool_alloc - allocate an element from a specific memory pool
193 * @pool: pointer to the memory pool which was allocated via
194 * mempool_create().
195 * @gfp_mask: the usual allocation bitmask.
196 *
197 * this function only sleeps if the alloc_fn() function sleeps or
198 * returns NULL. Note that due to preallocation, this function
199 * *never* fails when called from process contexts. (it might
200 * fail if called from an IRQ context.)
201 */
202void * mempool_alloc(mempool_t *pool, gfp_t gfp_mask)
203{
204    void *element;
205    unsigned long flags;
206    wait_queue_t wait;
207    gfp_t gfp_temp;
208
209    might_sleep_if(gfp_mask & __GFP_WAIT);
210
211    gfp_mask |= __GFP_NOMEMALLOC; /* don't allocate emergency reserves */
212    gfp_mask |= __GFP_NORETRY; /* don't loop in __alloc_pages */
213    gfp_mask |= __GFP_NOWARN; /* failures are OK */
214
215    gfp_temp = gfp_mask & ~(__GFP_WAIT|__GFP_IO);
216
217repeat_alloc:
218
219    element = pool->alloc(gfp_temp, pool->pool_data);
220    if (likely(element != NULL))
221        return element;
222
223    spin_lock_irqsave(&pool->lock, flags);
224    if (likely(pool->curr_nr)) {
225        element = remove_element(pool);
226        spin_unlock_irqrestore(&pool->lock, flags);
227        return element;
228    }
229    spin_unlock_irqrestore(&pool->lock, flags);
230
231    /* We must not sleep in the GFP_ATOMIC case */
232    if (!(gfp_mask & __GFP_WAIT))
233        return NULL;
234
235    /* Now start performing page reclaim */
236    gfp_temp = gfp_mask;
237    init_wait(&wait);
238    prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE);
239    smp_mb();
240    if (!pool->curr_nr) {
241        /*
242         * FIXME: this should be io_schedule(). The timeout is there
243         * as a workaround for some DM problems in 2.6.18.
244         */
245        io_schedule_timeout(5*HZ);
246    }
247    finish_wait(&pool->wait, &wait);
248
249    goto repeat_alloc;
250}
251EXPORT_SYMBOL(mempool_alloc);
252
253/**
254 * mempool_free - return an element to the pool.
255 * @element: pool element pointer.
256 * @pool: pointer to the memory pool which was allocated via
257 * mempool_create().
258 *
259 * this function only sleeps if the free_fn() function sleeps.
260 */
261void mempool_free(void *element, mempool_t *pool)
262{
263    unsigned long flags;
264
265    if (unlikely(element == NULL))
266        return;
267
268    smp_mb();
269    if (pool->curr_nr < pool->min_nr) {
270        spin_lock_irqsave(&pool->lock, flags);
271        if (pool->curr_nr < pool->min_nr) {
272            add_element(pool, element);
273            spin_unlock_irqrestore(&pool->lock, flags);
274            wake_up(&pool->wait);
275            return;
276        }
277        spin_unlock_irqrestore(&pool->lock, flags);
278    }
279    pool->free(element, pool->pool_data);
280}
281EXPORT_SYMBOL(mempool_free);
282
283/*
284 * A commonly used alloc and free fn.
285 */
286void *mempool_alloc_slab(gfp_t gfp_mask, void *pool_data)
287{
288    struct kmem_cache *mem = pool_data;
289    return kmem_cache_alloc(mem, gfp_mask);
290}
291EXPORT_SYMBOL(mempool_alloc_slab);
292
293void mempool_free_slab(void *element, void *pool_data)
294{
295    struct kmem_cache *mem = pool_data;
296    kmem_cache_free(mem, element);
297}
298EXPORT_SYMBOL(mempool_free_slab);
299
300/*
301 * A commonly used alloc and free fn that kmalloc/kfrees the amount of memory
302 * specified by pool_data
303 */
304void *mempool_kmalloc(gfp_t gfp_mask, void *pool_data)
305{
306    size_t size = (size_t)pool_data;
307    return kmalloc(size, gfp_mask);
308}
309EXPORT_SYMBOL(mempool_kmalloc);
310
311void mempool_kfree(void *element, void *pool_data)
312{
313    kfree(element);
314}
315EXPORT_SYMBOL(mempool_kfree);
316
317/*
318 * A simple mempool-backed page allocator that allocates pages
319 * of the order specified by pool_data.
320 */
321void *mempool_alloc_pages(gfp_t gfp_mask, void *pool_data)
322{
323    int order = (int)(long)pool_data;
324    return alloc_pages(gfp_mask, order);
325}
326EXPORT_SYMBOL(mempool_alloc_pages);
327
328void mempool_free_pages(void *element, void *pool_data)
329{
330    int order = (int)(long)pool_data;
331    __free_pages(element, order);
332}
333EXPORT_SYMBOL(mempool_free_pages);
334

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