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Linux/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  *  debugging by David Rientjes, Copyright (C) 2015
 10  */
 11 
 12 #include <linux/mm.h>
 13 #include <linux/slab.h>
 14 #include <linux/highmem.h>
 15 #include <linux/kasan.h>
 16 #include <linux/kmemleak.h>
 17 #include <linux/export.h>
 18 #include <linux/mempool.h>
 19 #include <linux/blkdev.h>
 20 #include <linux/writeback.h>
 21 #include "slab.h"
 22 
 23 #if defined(CONFIG_DEBUG_SLAB) || defined(CONFIG_SLUB_DEBUG_ON)
 24 static void poison_error(mempool_t *pool, void *element, size_t size,
 25                          size_t byte)
 26 {
 27         const int nr = pool->curr_nr;
 28         const int start = max_t(int, byte - (BITS_PER_LONG / 8), 0);
 29         const int end = min_t(int, byte + (BITS_PER_LONG / 8), size);
 30         int i;
 31 
 32         pr_err("BUG: mempool element poison mismatch\n");
 33         pr_err("Mempool %p size %zu\n", pool, size);
 34         pr_err(" nr=%d @ %p: %s0x", nr, element, start > 0 ? "... " : "");
 35         for (i = start; i < end; i++)
 36                 pr_cont("%x ", *(u8 *)(element + i));
 37         pr_cont("%s\n", end < size ? "..." : "");
 38         dump_stack();
 39 }
 40 
 41 static void __check_element(mempool_t *pool, void *element, size_t size)
 42 {
 43         u8 *obj = element;
 44         size_t i;
 45 
 46         for (i = 0; i < size; i++) {
 47                 u8 exp = (i < size - 1) ? POISON_FREE : POISON_END;
 48 
 49                 if (obj[i] != exp) {
 50                         poison_error(pool, element, size, i);
 51                         return;
 52                 }
 53         }
 54         memset(obj, POISON_INUSE, size);
 55 }
 56 
 57 static void check_element(mempool_t *pool, void *element)
 58 {
 59         /* Mempools backed by slab allocator */
 60         if (pool->free == mempool_free_slab || pool->free == mempool_kfree)
 61                 __check_element(pool, element, ksize(element));
 62 
 63         /* Mempools backed by page allocator */
 64         if (pool->free == mempool_free_pages) {
 65                 int order = (int)(long)pool->pool_data;
 66                 void *addr = kmap_atomic((struct page *)element);
 67 
 68                 __check_element(pool, addr, 1UL << (PAGE_SHIFT + order));
 69                 kunmap_atomic(addr);
 70         }
 71 }
 72 
 73 static void __poison_element(void *element, size_t size)
 74 {
 75         u8 *obj = element;
 76 
 77         memset(obj, POISON_FREE, size - 1);
 78         obj[size - 1] = POISON_END;
 79 }
 80 
 81 static void poison_element(mempool_t *pool, void *element)
 82 {
 83         /* Mempools backed by slab allocator */
 84         if (pool->alloc == mempool_alloc_slab || pool->alloc == mempool_kmalloc)
 85                 __poison_element(element, ksize(element));
 86 
 87         /* Mempools backed by page allocator */
 88         if (pool->alloc == mempool_alloc_pages) {
 89                 int order = (int)(long)pool->pool_data;
 90                 void *addr = kmap_atomic((struct page *)element);
 91 
 92                 __poison_element(addr, 1UL << (PAGE_SHIFT + order));
 93                 kunmap_atomic(addr);
 94         }
 95 }
 96 #else /* CONFIG_DEBUG_SLAB || CONFIG_SLUB_DEBUG_ON */
 97 static inline void check_element(mempool_t *pool, void *element)
 98 {
 99 }
100 static inline void poison_element(mempool_t *pool, void *element)
101 {
102 }
103 #endif /* CONFIG_DEBUG_SLAB || CONFIG_SLUB_DEBUG_ON */
104 
105 static void kasan_poison_element(mempool_t *pool, void *element)
106 {
107         if (pool->alloc == mempool_alloc_slab || pool->alloc == mempool_kmalloc)
108                 kasan_poison_kfree(element);
109         if (pool->alloc == mempool_alloc_pages)
110                 kasan_free_pages(element, (unsigned long)pool->pool_data);
111 }
112 
113 static void kasan_unpoison_element(mempool_t *pool, void *element, gfp_t flags)
114 {
115         if (pool->alloc == mempool_alloc_slab || pool->alloc == mempool_kmalloc)
116                 kasan_unpoison_slab(element);
117         if (pool->alloc == mempool_alloc_pages)
118                 kasan_alloc_pages(element, (unsigned long)pool->pool_data);
119 }
120 
121 static void add_element(mempool_t *pool, void *element)
122 {
123         BUG_ON(pool->curr_nr >= pool->min_nr);
124         poison_element(pool, element);
125         kasan_poison_element(pool, element);
126         pool->elements[pool->curr_nr++] = element;
127 }
128 
129 static void *remove_element(mempool_t *pool, gfp_t flags)
130 {
131         void *element = pool->elements[--pool->curr_nr];
132 
133         BUG_ON(pool->curr_nr < 0);
134         kasan_unpoison_element(pool, element, flags);
135         check_element(pool, element);
136         return element;
137 }
138 
139 /**
140  * mempool_destroy - deallocate a memory pool
141  * @pool:      pointer to the memory pool which was allocated via
142  *             mempool_create().
143  *
144  * Free all reserved elements in @pool and @pool itself.  This function
145  * only sleeps if the free_fn() function sleeps.
146  */
147 void mempool_destroy(mempool_t *pool)
148 {
149         if (unlikely(!pool))
150                 return;
151 
152         while (pool->curr_nr) {
153                 void *element = remove_element(pool, GFP_KERNEL);
154                 pool->free(element, pool->pool_data);
155         }
156         kfree(pool->elements);
157         kfree(pool);
158 }
159 EXPORT_SYMBOL(mempool_destroy);
160 
161 /**
162  * mempool_create - create a memory pool
163  * @min_nr:    the minimum number of elements guaranteed to be
164  *             allocated for this pool.
165  * @alloc_fn:  user-defined element-allocation function.
166  * @free_fn:   user-defined element-freeing function.
167  * @pool_data: optional private data available to the user-defined functions.
168  *
169  * this function creates and allocates a guaranteed size, preallocated
170  * memory pool. The pool can be used from the mempool_alloc() and mempool_free()
171  * functions. This function might sleep. Both the alloc_fn() and the free_fn()
172  * functions might sleep - as long as the mempool_alloc() function is not called
173  * from IRQ contexts.
174  */
175 mempool_t *mempool_create(int min_nr, mempool_alloc_t *alloc_fn,
176                                 mempool_free_t *free_fn, void *pool_data)
177 {
178         return mempool_create_node(min_nr,alloc_fn,free_fn, pool_data,
179                                    GFP_KERNEL, NUMA_NO_NODE);
180 }
181 EXPORT_SYMBOL(mempool_create);
182 
183 mempool_t *mempool_create_node(int min_nr, mempool_alloc_t *alloc_fn,
184                                mempool_free_t *free_fn, void *pool_data,
185                                gfp_t gfp_mask, int node_id)
186 {
187         mempool_t *pool;
188         pool = kzalloc_node(sizeof(*pool), gfp_mask, node_id);
189         if (!pool)
190                 return NULL;
191         pool->elements = kmalloc_node(min_nr * sizeof(void *),
192                                       gfp_mask, node_id);
193         if (!pool->elements) {
194                 kfree(pool);
195                 return NULL;
196         }
197         spin_lock_init(&pool->lock);
198         pool->min_nr = min_nr;
199         pool->pool_data = pool_data;
200         init_waitqueue_head(&pool->wait);
201         pool->alloc = alloc_fn;
202         pool->free = free_fn;
203 
204         /*
205          * First pre-allocate the guaranteed number of buffers.
206          */
207         while (pool->curr_nr < pool->min_nr) {
208                 void *element;
209 
210                 element = pool->alloc(gfp_mask, pool->pool_data);
211                 if (unlikely(!element)) {
212                         mempool_destroy(pool);
213                         return NULL;
214                 }
215                 add_element(pool, element);
216         }
217         return pool;
218 }
219 EXPORT_SYMBOL(mempool_create_node);
220 
221 /**
222  * mempool_resize - resize an existing memory pool
223  * @pool:       pointer to the memory pool which was allocated via
224  *              mempool_create().
225  * @new_min_nr: the new minimum number of elements guaranteed to be
226  *              allocated for this pool.
227  *
228  * This function shrinks/grows the pool. In the case of growing,
229  * it cannot be guaranteed that the pool will be grown to the new
230  * size immediately, but new mempool_free() calls will refill it.
231  * This function may sleep.
232  *
233  * Note, the caller must guarantee that no mempool_destroy is called
234  * while this function is running. mempool_alloc() & mempool_free()
235  * might be called (eg. from IRQ contexts) while this function executes.
236  */
237 int mempool_resize(mempool_t *pool, int new_min_nr)
238 {
239         void *element;
240         void **new_elements;
241         unsigned long flags;
242 
243         BUG_ON(new_min_nr <= 0);
244         might_sleep();
245 
246         spin_lock_irqsave(&pool->lock, flags);
247         if (new_min_nr <= pool->min_nr) {
248                 while (new_min_nr < pool->curr_nr) {
249                         element = remove_element(pool, GFP_KERNEL);
250                         spin_unlock_irqrestore(&pool->lock, flags);
251                         pool->free(element, pool->pool_data);
252                         spin_lock_irqsave(&pool->lock, flags);
253                 }
254                 pool->min_nr = new_min_nr;
255                 goto out_unlock;
256         }
257         spin_unlock_irqrestore(&pool->lock, flags);
258 
259         /* Grow the pool */
260         new_elements = kmalloc_array(new_min_nr, sizeof(*new_elements),
261                                      GFP_KERNEL);
262         if (!new_elements)
263                 return -ENOMEM;
264 
265         spin_lock_irqsave(&pool->lock, flags);
266         if (unlikely(new_min_nr <= pool->min_nr)) {
267                 /* Raced, other resize will do our work */
268                 spin_unlock_irqrestore(&pool->lock, flags);
269                 kfree(new_elements);
270                 goto out;
271         }
272         memcpy(new_elements, pool->elements,
273                         pool->curr_nr * sizeof(*new_elements));
274         kfree(pool->elements);
275         pool->elements = new_elements;
276         pool->min_nr = new_min_nr;
277 
278         while (pool->curr_nr < pool->min_nr) {
279                 spin_unlock_irqrestore(&pool->lock, flags);
280                 element = pool->alloc(GFP_KERNEL, pool->pool_data);
281                 if (!element)
282                         goto out;
283                 spin_lock_irqsave(&pool->lock, flags);
284                 if (pool->curr_nr < pool->min_nr) {
285                         add_element(pool, element);
286                 } else {
287                         spin_unlock_irqrestore(&pool->lock, flags);
288                         pool->free(element, pool->pool_data);   /* Raced */
289                         goto out;
290                 }
291         }
292 out_unlock:
293         spin_unlock_irqrestore(&pool->lock, flags);
294 out:
295         return 0;
296 }
297 EXPORT_SYMBOL(mempool_resize);
298 
299 /**
300  * mempool_alloc - allocate an element from a specific memory pool
301  * @pool:      pointer to the memory pool which was allocated via
302  *             mempool_create().
303  * @gfp_mask:  the usual allocation bitmask.
304  *
305  * this function only sleeps if the alloc_fn() function sleeps or
306  * returns NULL. Note that due to preallocation, this function
307  * *never* fails when called from process contexts. (it might
308  * fail if called from an IRQ context.)
309  * Note: using __GFP_ZERO is not supported.
310  */
311 void *mempool_alloc(mempool_t *pool, gfp_t gfp_mask)
312 {
313         void *element;
314         unsigned long flags;
315         wait_queue_t wait;
316         gfp_t gfp_temp;
317 
318         VM_WARN_ON_ONCE(gfp_mask & __GFP_ZERO);
319         might_sleep_if(gfp_mask & __GFP_DIRECT_RECLAIM);
320 
321         gfp_mask |= __GFP_NOMEMALLOC;   /* don't allocate emergency reserves */
322         gfp_mask |= __GFP_NORETRY;      /* don't loop in __alloc_pages */
323         gfp_mask |= __GFP_NOWARN;       /* failures are OK */
324 
325         gfp_temp = gfp_mask & ~(__GFP_DIRECT_RECLAIM|__GFP_IO);
326 
327 repeat_alloc:
328 
329         element = pool->alloc(gfp_temp, pool->pool_data);
330         if (likely(element != NULL))
331                 return element;
332 
333         spin_lock_irqsave(&pool->lock, flags);
334         if (likely(pool->curr_nr)) {
335                 element = remove_element(pool, gfp_temp);
336                 spin_unlock_irqrestore(&pool->lock, flags);
337                 /* paired with rmb in mempool_free(), read comment there */
338                 smp_wmb();
339                 /*
340                  * Update the allocation stack trace as this is more useful
341                  * for debugging.
342                  */
343                 kmemleak_update_trace(element);
344                 return element;
345         }
346 
347         /*
348          * We use gfp mask w/o direct reclaim or IO for the first round.  If
349          * alloc failed with that and @pool was empty, retry immediately.
350          */
351         if (gfp_temp != gfp_mask) {
352                 spin_unlock_irqrestore(&pool->lock, flags);
353                 gfp_temp = gfp_mask;
354                 goto repeat_alloc;
355         }
356 
357         /* We must not sleep if !__GFP_DIRECT_RECLAIM */
358         if (!(gfp_mask & __GFP_DIRECT_RECLAIM)) {
359                 spin_unlock_irqrestore(&pool->lock, flags);
360                 return NULL;
361         }
362 
363         /* Let's wait for someone else to return an element to @pool */
364         init_wait(&wait);
365         prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE);
366 
367         spin_unlock_irqrestore(&pool->lock, flags);
368 
369         /*
370          * FIXME: this should be io_schedule().  The timeout is there as a
371          * workaround for some DM problems in 2.6.18.
372          */
373         io_schedule_timeout(5*HZ);
374 
375         finish_wait(&pool->wait, &wait);
376         goto repeat_alloc;
377 }
378 EXPORT_SYMBOL(mempool_alloc);
379 
380 /**
381  * mempool_free - return an element to the pool.
382  * @element:   pool element pointer.
383  * @pool:      pointer to the memory pool which was allocated via
384  *             mempool_create().
385  *
386  * this function only sleeps if the free_fn() function sleeps.
387  */
388 void mempool_free(void *element, mempool_t *pool)
389 {
390         unsigned long flags;
391 
392         if (unlikely(element == NULL))
393                 return;
394 
395         /*
396          * Paired with the wmb in mempool_alloc().  The preceding read is
397          * for @element and the following @pool->curr_nr.  This ensures
398          * that the visible value of @pool->curr_nr is from after the
399          * allocation of @element.  This is necessary for fringe cases
400          * where @element was passed to this task without going through
401          * barriers.
402          *
403          * For example, assume @p is %NULL at the beginning and one task
404          * performs "p = mempool_alloc(...);" while another task is doing
405          * "while (!p) cpu_relax(); mempool_free(p, ...);".  This function
406          * may end up using curr_nr value which is from before allocation
407          * of @p without the following rmb.
408          */
409         smp_rmb();
410 
411         /*
412          * For correctness, we need a test which is guaranteed to trigger
413          * if curr_nr + #allocated == min_nr.  Testing curr_nr < min_nr
414          * without locking achieves that and refilling as soon as possible
415          * is desirable.
416          *
417          * Because curr_nr visible here is always a value after the
418          * allocation of @element, any task which decremented curr_nr below
419          * min_nr is guaranteed to see curr_nr < min_nr unless curr_nr gets
420          * incremented to min_nr afterwards.  If curr_nr gets incremented
421          * to min_nr after the allocation of @element, the elements
422          * allocated after that are subject to the same guarantee.
423          *
424          * Waiters happen iff curr_nr is 0 and the above guarantee also
425          * ensures that there will be frees which return elements to the
426          * pool waking up the waiters.
427          */
428         if (unlikely(pool->curr_nr < pool->min_nr)) {
429                 spin_lock_irqsave(&pool->lock, flags);
430                 if (likely(pool->curr_nr < pool->min_nr)) {
431                         add_element(pool, element);
432                         spin_unlock_irqrestore(&pool->lock, flags);
433                         wake_up(&pool->wait);
434                         return;
435                 }
436                 spin_unlock_irqrestore(&pool->lock, flags);
437         }
438         pool->free(element, pool->pool_data);
439 }
440 EXPORT_SYMBOL(mempool_free);
441 
442 /*
443  * A commonly used alloc and free fn.
444  */
445 void *mempool_alloc_slab(gfp_t gfp_mask, void *pool_data)
446 {
447         struct kmem_cache *mem = pool_data;
448         VM_BUG_ON(mem->ctor);
449         return kmem_cache_alloc(mem, gfp_mask);
450 }
451 EXPORT_SYMBOL(mempool_alloc_slab);
452 
453 void mempool_free_slab(void *element, void *pool_data)
454 {
455         struct kmem_cache *mem = pool_data;
456         kmem_cache_free(mem, element);
457 }
458 EXPORT_SYMBOL(mempool_free_slab);
459 
460 /*
461  * A commonly used alloc and free fn that kmalloc/kfrees the amount of memory
462  * specified by pool_data
463  */
464 void *mempool_kmalloc(gfp_t gfp_mask, void *pool_data)
465 {
466         size_t size = (size_t)pool_data;
467         return kmalloc(size, gfp_mask);
468 }
469 EXPORT_SYMBOL(mempool_kmalloc);
470 
471 void mempool_kfree(void *element, void *pool_data)
472 {
473         kfree(element);
474 }
475 EXPORT_SYMBOL(mempool_kfree);
476 
477 /*
478  * A simple mempool-backed page allocator that allocates pages
479  * of the order specified by pool_data.
480  */
481 void *mempool_alloc_pages(gfp_t gfp_mask, void *pool_data)
482 {
483         int order = (int)(long)pool_data;
484         return alloc_pages(gfp_mask, order);
485 }
486 EXPORT_SYMBOL(mempool_alloc_pages);
487 
488 void mempool_free_pages(void *element, void *pool_data)
489 {
490         int order = (int)(long)pool_data;
491         __free_pages(element, order);
492 }
493 EXPORT_SYMBOL(mempool_free_pages);
494 

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